Synthesis and Characterization of

合集下载

磷酸钒锂

Synthesis and characterization of carbon-coatedL i3V2(PO4)3/C cathode materials with differentcarbon sourcesKey Laboratory of Materials for Energy Conversion of Academia Sinica, Department of Materials Science and Engineering,University of Science and Technology of China, Anhui Hefei 230026, China Available online 15 January 2009Experimental1.化学计量比的L i 2C O 3,V 2O 5,NH 4H 2P O 4,(citric acid, glucose, PVDF and starch)溶于丙酮中，在球磨机中研磨几个小时使其充分混合均匀.2.得到的混合物放到烤箱中设定温度70°C 蒸发掉丙酮，在高纯氮气保护下350°C 预处理5h ，去除里面的H 2O 和NH3.3.在氮气保护下750°C 烧结16h 得到LVP/CResults and discussion•TG1.a weight loss processburnout of the residual carbon2.weight gain stepthe oxidation of V3+ inair3.carbon content1.33%, 13.27%, 12.68% and10.46% for the samples from thecarbon sources citric acid,glucose, PVDF and starchSEMa.a granular shapeporous structureb.some large particlesexistc.Many nano-sizedembedded in acontinuous carbonnetworkd.similar to glucosesome large particles existcharge-discharge curves166.7, 158.8, 152.9 and152.2mAhg−1citric acid, glucose,PVDF and starchcycle numberAfter 50 cycles, thedischarge capacityreaches 144.7, 135.7,130.0 and 130.8mAhg−1,is indicating thattheir capacityretention is 86.8%,85.5%, 85.0% and 85.9%of the initialdischarge capacityratePVDF-samplepossesses a uniformcarbon network Li3V2(PO4)3/Cparticles imbeddedcitric acid-samplepoor rate performanceowest residual carboncontent•114.6, 104.5, 107.4 and 107.7mAh g-1,•almost no capacity fading is measured for 100 cycles•the rate performances of samples are a little bette。

Synthesis and characterization of low cost magnetorheological (MR) fluids

SYNTHESIS AND CHARACTERIZATION OF LOW COSTMAGNETORHEOLOGICAL (MR) FLUIDSVK Sukhwani and H Hiraniv_sukhwani@iitb.ac.in , hirani@iitb.ac.inDepartment of Mechanical Engineering, Indian Institute of Technology BombayMumbai-40007, INDIAABSTRACTMagnetorheological fluids have great potential for engineering applications due to their variable rheological behavior. These fluids find applications in dampers, brakes, shock absorbers, and engine mounts [1].However their relatively high cost (approximately US$600 per liter) limits their wide usage. Most commonly used magnetic material “Carbonyl iron” cost more than 90% of the MR fluid cost [2]. Therefore for commercial viability of these fluids there is need of alternative economical magnetic material. In the present work synthesis of MR fluid has been attempted with objective to produce low cost MR fluid with high sedimentation stability and greater yield stress. In order to reduce the cost, economical electrolytic Iron powder (US$ 10 per Kg) has been used. Iron powder of relatively larger size (300 Mesh) has been ball milled to reduce their size to few microns (1 to 10 microns). Three different compositions have been prepared and compared for MR effect produced and stability. All have same base fluid (Synthetic oil) and same magnetic phase i.e. Iron particles but they have different additives. First preparation involves organic additives Polydimethylsiloxane (PDMS) and Stearic acid. Other two preparations involve use of two environmental friendly low-priced green additives guar gum (US$ 2 per Kg) and xanthan gum (US$ 12 per Kg) respectively.Magnetic properties of Iron particles have been measured by Vibrating Sample Magnetometer (VSM). Morphology of Iron particles and additives guar gum and xanthan gum has been examined by Scanning Electron Microscopy (SEM) and Particles Size Distribution (PSD) has been determined using Particle size analyzer. Microscopic images of particles, M-H plots and stability of synthesized MR fluids have been reported. The prepared low cost MR fluids showed promising performance and can be effectively used for engineering applications demanding controllability in operations Keywords: Smart fluids, MR fluid, Magnetorheology, Particle distribution, Guar gum, Xanthan gum, PDMS, Low cost.1.INTRODUCTIONMagnetorheological (MR) fluids are known for their ability to change their rheological behavior by several orders of magnitude within milliseconds under the influence of magnetic field and therefore have been regarded as controllable fluids for engineering applications. Typically these fluids are non colloidal suspensions of micron sized magnetic particles (generally Iron particles) in nonmagnetic carrier medium (mineral oil, synthetic oil or water). Under the influence of magnetic field, these particles polarize and forms columnar structure parallel to the applied field, thus increases the apparent viscosity of the fluid which develops the yield stress in the structure. This viscosity change is rapid and completely reversible. Therefore MR fluid can be converted from a free flowing liquid to a plastic like solid by applying magnetic field and vice versa and can be used in different applications to bring dynamic change in performance measures like damping resistance as in MR-dampers, braking torque in MR-brakes and minimum film thickness in MR-bearings [3].Performance of any MR fluid in any application depends upon the magnetic properties of the solid phase, volume fraction, size and distribution of the magnetic particles, and viscosity of the carrier fluid etc.The synthesis of MR fluid involves many challenges. Two critical factors are the problem of gravitational sedimentation and agglomeration of particles and relatively high cost of MR fluids (approximately US$ 600 per liter). The large density difference between magnetic particles (i.e., ρ =7.86 g/cm3) and carrier fluid (i.e. ρ =1 g/cm3) is responsible for sedimentation problem. The problem of sedimentation has been mainly solved by three approaches, by adding Behavior and Mechanics of Multifunctional and Composite Materials 2007, edited by Marcelo J. DapinoProc. of SPIE Vol. 6526, 65262R, (2007) · 0277-786X/07/$18 · doi: 10.1117/12.720870surfactants, by adding nano particles or using nano magnetizable particles and by coating magnetizable particles with polymers .The addition of nano particles or use of nano magnetizable particles improves sedimentation stability effectively but at the same time it also reduces the MR effect produced by MR fluids. [4]High cost of MR fluid is mainly due to the high cost of magnetic material. Most commonly used magnetic material is Carbonyl iron obtained by thermal decomposition of Iron penta carbonyl .This material costs more than 90 % of the MR fluid cost [2, 5] Therefore for commercial viability of these fluids there is need of alternative economical magnetic material. In addition, an important functional requirement to produce more MR effect is the high dynamic yield stress. Use of alternative materials to reduce the cost has been reported in literature. Foister et al [5] in their patent have described the synthesis of low cost MR fluid using low cost water atomized Iron powder, multi component organoclay and multi component additive. Also the use of green additives like guar gum as thixotropic agent to solve the problem of sedimentation and agglomeration of MR fluids has been reported in literature. Chen et al [4] and Wu Wei Ping et al [6] successfully employed guar gum for improving sedimentation stability of MR fluids but they used the expensive carbonyl iron powder for synthesis of MR fluid. Similarly use of xanthan gum for achieving sedimentation stability of particles in MR fluid has been described by JD Carlson and JC Jones Guion in their patent. [7]As per authors knowledge no one has attempted use of both the economical Iron powder and additives like guar gum or xanthan gum in a single MR fluid composition. This has been attempted in the present work. In the present work synthesis of MR fluids have been carried out with objective to produce low cost MR fluid with high sedimentation stability and large yield stress. Low cost electrolytic Iron powder as magnetic material and variety of additives has been used for the present synthesis.2. SELECTION OF MAGNETIC PARTICLESThe magnetic particles for MR fluids should have high saturation magnetization and low coercivity. Carbonyl iron powder [8, 9, 10, 11], Nickel Zink ferrite [12], Iron oxide coated polymer composite particles [13], and Iron Cobalt alloy [14, 15] go well with these requirements. Saturation magnetization of Nickel Zink ferrite, Iron powder and Iron Cobalt alloy are 0.4T, 2.1 T and 2.43 T respectively [12,15] i.e. Iron Cobalt alloy has highest saturation magnetization but its density (8.1 g/ cm3) is greater than Iron therefore it aggravates gravitational settling. All the above mentioned magnetic materials are costly and therefore don’t suit the present synthesis of low cost MR fluid. Therefore for present synthesis Iron powder produced by electrolytic process has been chosen as this process yields the Iron of very high purity at very economical price (US$ 10 per Kg).The electrolytic Iron (EI) powder of relatively larger size 300 mesh (SD Fine-Chem, India) has been ball milled by suitable stainless steel grinding media in stainless steel pot to reduce the size to the order of few microns (1 -10 micron). This milled Iron powder was used for synthesis of all three MR fluids..3. SELECTION OF CARRIER FLUIDThe function of carrier or base fluid is to provide liquid phase in which magnetically active phase can be suspended. The carrier fluid should be non magnetic, nontoxic, non corrosive and non reactive. As most of lubricant with their additives packages suits these requirements, the commercial lubricants can be used for synthesis of MR fluid. In the present synthesis work, PAO (Poly Alfa Olefin) based high temperature synthetic oil with density 0.87 gram /cm3 and viscosity 20 cSt (0.01 Pa s) at 40°C has been selected. This oil can withstand operating temperature up to 180°C.4. SELECTION OF ADDITIVESAs discussed earlier, many additives have been attempted by researchers for synthesis of MR fluid. Generally thixotropic agents are added to prevent particle sedimentation. In addition, anti wear, anti corrosion, friction modifier and antioxidant agent are also added. Following are some important additives used in the synthesis of MR fluids for different purposes as reported in the literature:•To overcome sedimentation,o Fumed Silica [11], Lithium stearate, Aluminum distearate, Thiophosphorus, Thiocarbomate, Phosphorus, Guar gum [4], Organoclay[16] Poly vinyl pyrolidone [17], Poly vinyl butyl [18]•To overcome agglomeration,o Fumed silica [11], Fibrous carbon [19], Stearic acid [20], Sodium dodecyl sulphate [15], Viscoplastic media[21] o To increase abrasion wear resistance,o ZDDP (Zink dialkyl dithio phosphate ) [22-23]•To reduce oxidation,o ZDDP [23]• To reduce friction resistance.o Organomolybydnums (Moly) [22]Most of the above additives are not only expensive they are harmful to environment also. Therefore two environmental friendly additives, guar gum and xanthan gum have been chosen to prevent sedimentation of particles in the present synthesis. However for comparison purpose one organic polymer Polydimethylsiloxane (PDMS) has also been used as additives in one MR fluid composition.Guar gum is a high molecular weight hydro colloidal polysaccharide. It is extracted from guar bean (Cyamopsistetra gonoloba). It consist of linear chains of (1→4) linked ß-D mannose residue with a-D-galactopyranosyl units attached by (1.6) linkages. There is no polar group on the main chain of the guar gum, and most of the hydroxyl group is located outside. Furthermore, the side chain of the a-D-galactopyranosyl units does not hide the active alcoholic hydroxyl group; therefore it has a very large area of hydrogen bond. These characteristics make it useful as a thickening agent, suspension agent and stabilizing agent [4]. Its main application is found in food industry, where it is used as thickener, suspending agent and binder agent of free water in sauces, Ice cream, salad dressings etc.Similarly xanthan gum is a biosynthetic gum similar to natural gum. Xanthan gum is a long chain polysaccharide. It is prepared by fermentation of corn sugar with a microbe called Xanthomonas campestris. Xanthan gum has a special molecular structure. Its most important property is its very high viscosity at low-shear and relatively low viscosity at high shear. High viscosity at low shear provides stability to colloidal suspensions and therefore it is used as thickener and stabilizer for emulsions and suspensions.In the present work guar gum with approximate particle size 300 mesh (Premcem Gums India) and xanthan gum (Sienokem USA) have been used as thixotropic additives in two different preparations. In another preparation organic additive Polydimethylsiloxane (PDMS) with viscosity 100 cSt and Stearic acid are used. In addition an additive pack consists of anti wear, anti rust, anti corrosion, friction modifier and anti oxidant agent has also been used in all three preparations.5. CHARACTERIZATIONThe solid phase of MR fluid i.e. magnetic material was characterized before it is used in synthesis. Typically characterization includes analysis of particle size and its distribution, morphology and magnetic characterization. Additives guar gum and xanthan gum were also checked for their morphology.5.1 Particle size distribution analysisParticle size distribution analysis is very important for synthesis of MR fluid as particle size and size distribution influence the important properties i.e. Sedimentation stability, yield stress and magnetic properties of MR fluids [24]. Ota and Miyamoto [25] using two particle sizes calculated the static yield stress for a theoretical ER fluid and concluded that “ER Fluid consist of only same particle size gives the higher yield stress”. Lemaire et al [26] reported the influence of particle size on MR effect “It is better to have monodisperse sample in order to optimize the MR effect”. This indicates that narrow size distribution leads to more MR effect. But Wereley et al [13] in their study concluded that use of bidisperse particles in MR fluid increases their sedimentation stability. They also suggested a favorable tradeoff of proportion of particle sizes to increase the yield stress of MR fluid. Often particle size ranging 0.1 micron to 10 micronsis preferred [27]. Particle lesser than 0.1 micron will be subjected to random Brownian forces which destroy the chain like structure leading to decrease in the yield stress. On the other hand particles larger than 10 microns create the sedimentation problem. Kordonski et al [24] reported that particle size growth results in quadratic decrease of stability. Magnetic particles were analyzed using a particle size analyzer (GALAI computerized inspection system CIS-1, Particle size analyzer, Israel). Particles were dispersed in de ionized water with few drops of polyelectrolyte stabilizer to prevent the agglomeration of particles. Sodium Hexa Meta Phosphate was used as a medium to disperse the particles in this case. Sonication was also done to disperse the particles thoroughly. Fig-1 and Fig-2 show the particle size distribution of magnetic Electrolytic Iron (EI) particles before and after milling.Fig 1 Probability Volume density Graph for Electrolytic Iron powder before millingFig 2 Probability Volume density Graph for Electrolytic Iron powder after millingResults show that magnetic particle have broad size distribution (3.94 -77.50 microns ) with mean size 39 micron before milling and narrow size distribution (1.11-9.50microns) with mean size 4.27 micron after milling. This size range is recommended size range (1-10 micron) and therefore they are suitable for synthesis of MR fluids. These particles will have relatively lesser tendency to settle down.5.2 Morphology of magnetic particles and gum powdersThe morphology of the particles was studied by scanning electron microscopy (SEM facility S-3400 N, Hitachi Science Systems Japan). The powder sample was prepared by placing very small amount of powder on double sided carbon tape and pressing with the tip of spatula. The tape was then placed on brass stub. Gold plating was done on the samples to make the samples conducive. High vacuum was used and SEM was operated at 6-10 KV.Fig 3 SEM Image of Electrolytic Iron Particles before millingThe SEM image of the electrolytic Iron particles is shown in fig-3 .It shows the characteristic morphology of the particles .The electrolytic iron particles are of dendrite shape with a size distribution. Also they are in well dispersed state. SEM was also done for additives guar gum and xanthan gum. Fig-4 shows the SEM images (×500) obtained.(a) Guar gum (b) Xanthan gumFig 4 SEM Images of Guar gum and Xanthan gum powder5.3 Magnetic properties of particlesMagnetic properties of Iron particles were measured using vibrating sample magnetometer (VSM) technique. The VSM facility used for this purpose is Lakeshore VSM (Model 7410) interfaced with Lakeshore Cryotronics, Inc.VSM software.The Iron powder weight was measured with the accuracy of 0.0001 g by electronic balance (Precisa, Switzerland). The powder sample is pressed in to a small pellet. Small part of pellet (10-100 mg) is weighed and wrapped tightly in a butter paper /Teflon tape to avoid the movement of powder inside the sample holder. The magnetic field up to 20 K Oe was applied and operating frequency was 82 Hz.VSM was also done for costly carbonyl Iron (CI) powder to compare the magnetic properties of economical electrolytic Iron (EI) with costly carbonyl Iron (CI). Figure-5 shows M-H curves of the EI powder and CI powder obtained at room temperature (210C). The VSM results show that saturation magnetization of the electrolytic Iron powder is quite high (204.54emu/g) and approximately is of the same order of saturation magnetization of costly carbonyl Iron powder which is mostly used in synthesis of MR fluids. The saturation magnetization of carbonyl Iron (CI) powder has been found 212.08 emu/g. Slightly lower value of saturation magnetization of electrolytic iron powder in comparison to carbonyl Iron may be due to the fact that the electrolytic Iron used has 95.0 % purity while examined carbonyl Iron has 97-98 % purity. Moreover electrolytic Iron powder has also been milled to reduce the particle size which may also induce some impurities in the powder. Therefore more saturation magnetization will be obtained if EI powder having more purity is used.Coercivity was also determined from VSM data. Measured coercivity for electrolytic Iron is 26 O e and for carbonyl Iron it is 22 Oe. This shows that coercivity of electrolytic iron is only a little higher than the coercivity of carbonyl Iron. Moreover its value is still lower than 50 Oe and therefore can be considered as soft magnetic materials [28]Fig 5 M-H curves for Electrolytic Iron and Carbonyl Iron6. SYNTHESIS ROUTEIn present work three MR fluids are prepared using same base fluid (PAO based synthetic oil) and same magnetic phase i.e. electrolytic Iron (EI) powder but with different additives. These MR fluids are:MR Fluid-1: It has thixotropic agent Polydimethylsiloxane (PDMS) which is silicon based organic polymer and is known for its anti caking properties, Stearic acid as stabilizer additives and an additive package consist of anti wear, anti corrosion, friction modifier and anti oxidant agent.MR Fluid-2: It has green additive guar gum as thixotropic agent and above additive package. MR Fluid-3: It has additive xanthan gum as thixotropic agent and above additive package.6.1Coating of guar gum/xanthan gum on Iron particlesAdditives guar gum /xanthan gum were coated on the milled EI powder. Wu Wei Ping et al [6] reported that additive guar gum will be more effective when it is coated over the iron particles rather than co ball milling it with the Iron powder therefore first approach has been used in this work. For coating guar gum /xanthan gum over Iron particles the measured quantity of guar gum /xanthan gum was added to some quantity of water and mixed by mechanical stirrer for 30 minutes at 500 rpm. Iron powder was then added and mixture was agitated for 30 minutes at 1000 rpm. Ethanol was then added gradually to the mixture which leads to guar gum or xanthan gum forming a coating on the Iron powder. Precipitate was washed with acetone and filtered and dried to remove the water and then milled. These coated particles were used for synthesis. The weight percentage of guar gum /xanthan gum in the MR fluids is 3 %.6.2 Preparation of MR fluidsTo prepare MR fluid, first the appropriate amount of additive package consist of anti wear, anti rust, anti corrosion, friction modifier and anti oxidant agent was added to the measured quantity of base oil and mixed appropriately for 15 minutes by mechanical stirrer. The Iron particles (uncoated in case of MR fluid-1 and coated in case of MR fluid-2 and MR fluid-3) were then directly dispersed with specified volume fraction (0.36) in the above mixture. This mixture was homogenized by agitation of a mechanical stirrer at 1000 RPM for twenty-four hours to make MR fluid homogeneous. Appropriate amounts of PDMS with viscosity100 cSt and Stearic acid were also added in addition to the above additive package to the base oil for synthesis of MR fluid MRF-1. Fig-6 shows the flow chart for synthesis route of Magnetorheological fluid. The compositions of different MR fluids synthesized are given in table-1.Fig 6 Flow chart for Synthesis route of MR fluidsTable -1, Compositions of synthesized MR Fluids7. RESULTS & DISCUSSIONSIn present study three MR fluids have been synthesized using synthetic oil as base fluid, economical electrolytic Iron (with purity > 95.0 %) particles as magnetic phase and different additives. The prepared MR fluids were checked for their magnetic properties, expected MR effect and stability against sedimentation. Results of the study are as follows:7.1 Magnetic properties of uncoated particlesAs discussed earlier, magnetic properties of uncoated EI particles has been determined by VSM. Results indicate that saturation magnetization which is most important factor for producing MR effect i.e. yield stress developed , of low cost electrolytic iron powder (204.54 emu/g) is slightly lower (3.5%) than that of costly Carbonyl iron powder (212.084 emu/g). Similarly measured coercivity of EI powder (26 Oe) is slightly greater than Coercivity of CI powder (24 Oe).Therefore electrolytic Iron (EI) can be used for synthesis of MR fluid to reduce the cost of MR fluid significantly without significant reduction in MR effect.MRF-1 MRF-2 MRF-3 Ingredients Weight % Approx.Vol % Weight % Approx.Volume % Weight % Approx.Volume %Syntheticoil 16 64 15.5 64 15.5 64 Iron Powder81 36 81 36 81 36PDMS 2 ------ ------ ------ ------ ------ Stearicacid0.5 ------ ------ ------ ------ ------Guar gum ---- ------ 3.0 ------ ------ ------ Xanthangum ---- ------ ------ ------ 3.0 ------ Additive package0.5 ------ 0.5 ------ 0.5 ------7.2 Magnetic properties of coated particlesTo observe the effect of the additives coating on the magnetic properties of iron particles the magnetic properties of guar gum and xanthan gum coated particles were also checked by VSM. M-H curves for guar gum and xanthan gum coated particles are shown in figure-7. M-H curves show that saturation magnetization of guar gum coated and xanthan gum coated Iron particles are 198.52 emu/g and 198.14 emu/g respectively. Theses values are slightly lower (3%) than magnetic saturation of uncoated iron particles (204.54 emu/g). Measured Coercivity of these guar gum coated and xanthan gum coated Iron particles are 26 Oe and 28 Oe respectively which are almost same as that of coercivity of uncoated EI particles (26 Oe). This shows that coating of additives guar gum and xanthan gum on Iron particles has negligible effect on magnetic properties of Iron particles and therefore it can be concluded that MR effect produced by MR fluid will not reduce due to additive coating.Fig 7 M-H curves for Guar gum and Xanthan gum coated Electrolytic Iron7.3 MR effect expected (Yield stress developed)Magnetorheological (MR) effect produced by any MR fluid is the measure of its performance and is judged by maximum yield stress developed on application of magnetic field. For a MR fluid of known particle loading, particle size and known viscosity of base fluid the maximum yield stress depends upon the saturation magnetization of the magnetic material.The yield stress developed in MR fluid can be determined by performing magnetorheological measurement using a rheometer with an arrangement to produce magnetic field. Alternatively maximum yield stress developed in any MR fluid can be determined by measuring the saturation magnetization of the magnetic particles using VSM (Vibrating Sample Magnetometer). The relation between maximum obtainable yield stress and saturation magnetization of the magnetic particles has bee reported in the literature [29] as 20524()(3)()5yd s sat M τξφµ⎛⎞=⎜⎟⎝⎠(1)Where, yd τ is the yield stress, 0s M µ is saturation magnetization, φ is the particle volume fraction, 0µ is permeability of the free space and (3) 1.202ξ=(a constant)Table-2 shows the maximum yield stress expected to develop in three MR fluids obtained by using Eqn-1, based on their saturation magnetization values obtained by VSM .The values of yield stresses obtained for MRF-1, MRF-2 and MRF-3are quite high and are comparable to the value of yield stress (108 KPa) obtained for MR fluid using carbonyl Iron powder (2.09 T).Table 2- Expected Yield Stress for synthesized MR FluidsMR Fluid Saturation Magnetization Yield stress (KPa)MRF-1 204.54 emu/g (2.01 T) 99.59MRF-2 198.52 emu/g (1.96 T) 94.70MRF-3 198.14 emu/g (1.95 T) 93.737.4 Sedimentation stabilityPrepared MR fluids were put in graduated cylindrical flasks and observed over period of time for their sedimentation behavior i.e. settling of particles due to gravity. It was found that all three MR fluids remain in a well dispersed and stable state without significant settling of particles for quite long time. This is due to use of different thixotropic additives in MR fluids which reduces the sedimentation by forming weakly bonded structure in the fluid .These three dimensional structures have high apparent viscosity at low shear which prevents particle settling in the suspension. These structures collapse under shear leading to significant reduction in viscosity but reform again on removal of shear. Though all three MR fluids show very good stability against sedimentation but the MR fluids prepared by using additives guar gum and xanthan gum (MR fluid-2 and MR fluid-3) have better stability in comparison to MR fluid prepared using PDMS and Stearic acid (MR fluid-1). Sedimentation stability obtained are in the decreasing order from MRF-3 to MRF-1 i.e. lowest sedimentation tendency among three fluids was observed for MR fluid with xanthan gum and the highest sedimentation tendency was observed for MR fluid with PDMS. The result shows that the coating of guar gum and xanthan gum on iron particles gives better results in comparison to adding PDMS to the base fluid. This shows the utility of low-cost environmental friendly additives guar gum and xanthan gum in synthesis of MR fluids.8. CONCLUSIONS(01) Economical Iron powder produced by electrolytic process has very good magnetic properties, almost as good as costly carbonyl Iron powder which is most commonly used magnetic material for synthesis and therefore electrolytic Iron can be used as magnetic material to reduce the cost of MR fluid considerably without any significant reduction of MR effect produced.(02) Environmental friendly additives like guar gum and xanthan gum have been found more useful in comparison to organic polymer PDMS for preventing sedimentation of the particles in the MR suspension. Lowest sedimentation tendency has been observed for MR fluid with xanthan gum and the highest sedimentation tendency has been observed for MR fluid with PDMS.(03) The effect of coating of additives guar gum and xanthan gum on saturation magnetization and coercivity of Iron particles has almost been negligible. Therefore these additives can be used to improve the sedimentation stability without reducing MR effect produced by the MR fluids.(04) All three synthesized low cost MR fluids show very good stability against sedimentation and large yield stress therefore can be used in different commercial applications for achieving controllability in operation at relatively low cost..ACKNOWLEDGEMENTAuthors would like to thank their institute IIT Bombay for providing all the necessary facilities required for this workREFERENCES[1] Li W H, Du H and Guo NQ , “Finite Element Analysis and Simulation Evaluation of a Magnetorheological Valve”, Int. Journal of Advance Manufacturing Technology, Vol. 21, pp.438–445, 2003[2] Goncalves F D, Koo, J H, and Ahmadin M, “A review of the state of art in magnetorheological fluid technology – Part 1: MR Fluid and MR fluid models”, Shock and Vibration Digest, Vol.38, pp. 203-219, 2006,[3] Sukhwani VK and Hirani H, “Synthesis of a Magnetorheological lubricant” 5th International conference on Industrial tribology, ICIT-06, IISc Bangalore, Nov.30 –Dec. 02, 2006.[4] Fang Chen, Zhao Bin Yuan, Chen Le Sheng, Wu Qing, Liu Nan and Hu Ke Ao , “The effect of the green additive guar gum on the properties of magnetorheological fluid” , Smart materials structure, Vol.14, pp. N1-N5,2005.[5] Foister, Robet T, Iyanger, Vardarajan R, Yurgelvic and Sally M “Low cost MR fluid” US Patent No 6787058 , 2004[6] Wu Wei Ping , Zhao Bin Yuan , Wu Qing , Chen Le sheng and Hu Ke Ao, “The strengthening effect of guar gum on the yield stress of magnetorheological fluid” , Smart materials structure,Vol.15, pp. N94-N98,2006.[7] Carlson J D and Jones Guion J C, “Aqueous magnetorheological materials” U S Patent No 5670077, 1997.[8] Rabinow J, US Patent No 2575360, 1951.[9] Rabinow J, “The magnetic fluid clutch”, AIEE Trans, Vol. 67, pp.1308, 1948[10] Park J H, B yung Doo Chin and Ook Park , “Rheological properties and stabilization of magnetorheological fluid ina water in oil emulsion”, Journal of Colloid and Interface science, Vol. 240, pp 349-354 ,2001.[11] Lim S T, Cho M S, Jang I B and Choi H J, “Magnetrheological characterization of carbonyl iron suspension stabilized by fumed silica”, Journal of magnetism and magnetic materials, Vol. 282, pp .170-173, 2004.[12] Phule P P and Ginder J M “Synthesis and properties of novel magnetorheological fluids having improved stability and redispersibility”, 6th International conference on ER Fluids , MR suspensions and their applications, Yonezawa, Japan, World scientific, pp 445-453,1997.[13] Werely N M, Chaudhuri A , Yoo J H , John S, Kotha S, Suggs A , Radhakrishnan R, Love B J and Sudarshan T S, “Bidisperse magnetorheological fluids using Fe particles at nanometer and micron scale” ,Journal of Intelligent Materials, Systems and Structures, Vol. 17, pp. 393-401,2006.[14] Margida A J , Wiess K D and Carlson J D , “Magnetorheological materials based on Iron alloy particles”, Int. Journal of Modern Phys B, Vol.10, pp. 3335-3341,1996.[15] Phule P P and Jatkar A D, “Synthesis and processing magnetic iron cobalt alloy particles for high strength magnetorheological fluids”, 6th International conference on ER Fluids, MR suspensions and their applications, Yonezawa, Japan, World scientific, pp. 503-510,1997.[16] Foister R.T. Iyanger V R and Yugelevic S M, “Stabilization of magnetorheological fluid suspension using a mixture of organoclays”, US Patent No 6,592,772, 2003.[17] Phule P. “Magnetorheological fluid”, US Patent No 5,985,168, 1999[18] Jang I. B., Kim H B, Lee J Y ,You J L, Choi H J and John M S , “Role of organic coating on carbonyl Iron suspended particles in magnetorheological fluids”, Journal of Applied Phys, Vol.97, pp. 1-3, 2005。

Synthesis and characterization of Y_2O_2SEu~3+,Mg~2+,Ti~4+ nanorods via a solvothermal routine

JOURNAL OF RARE EARTHS,Vol.27,No.6,Dec.2009,p.895Fou ndation it em:Project s upported by the National Natural Science Foundation of China (20671042,50872045)and the Natural Science Foundations of Guang-dong Province (0520055,7005918)Cor respondin g aut hor:LI Wenyu (E-mail:liwenyu_jnn@;Tel.:+86-20-85221813)DOI 6S ()635Synthesis and char acter ization of Y 2O 2S:Eu 3+,Mg 2+,Ti 4+nanorods via a solvothermal routineLI Wenyu (李文宇),LIU Yingliang (刘应亮),AI Pengfei (艾鹏飞),CHEN Xiaobo (陈小博)(Department of Chemistry,Jinan University,Guangzhou 510632,Chi na)Received 24December 2008;revised 27April 2009Abstract:Y 2O 2S:Eu 3+,Mg 2+,Ti 4+nanorods were prepared by a solvothermal procedure.Rod-like Y(OH)3was firstly synthesized by hydro-thermal method to serve as the precursor.Y 2O 2S:Eu 3+,Mg 2+,Ti 4+powders were obtained by calcinating the precursor at CS 2atmosphere.The Y 2O 2S:Eu 3+,Mg 2+,Ti 4+phosphor with diameters of 30–50nm and lengths up to 200–400nm inherited the rod-like shape from the pre-cursor after calcined at CS 2atmosphere.The Y 2O 2S:Eu 3+,Mg 2+,Ti 4+nanorods showed hexagonal pure phase,good dispersion and exhibited bright red luminescence.After irradiation by 265or 325nm for 5min,the phosphor emitted red long-lasting phosphorescence,and the phos-phorescence could be seen with the naked eyes in the dark clearly for more than 1h after the irradiation source was removed.It was consid-ered that the long-lasting phosphorescence was due to the persistent energy transfer from the traps to the Ti 4+and Mg 2+ions to generate the red-emitting long-lasting phosphorescence.Keywords:yttrium oxysulfide;rod-like structure;nanomaterials;luminescence;rare earthsDuring the recent half-century there have been consider-able interests in the long-lasting phosphors because of their potential applications in safety indicators,fluorescent lamps,urgent illumination system,and cathode ray tubes,etc.[1–4]From the point of practical application,red is one of the three fundamental colors,and a red or orange afterglow phosphor is most suitable as illuminating light sources and appropriate for various displays.Therefore,red long-lasting phosphors with high luminescence and good chemical sta-bility are badly needed.Yttrium oxysulfide has been known for a long time as an excellent red phosphor host material.While doped with Eu,Mg,Ti,a red long-lasting phosphor with the afterglow time of above 3h has been synthesized [5].But until now,the progress on the systemic research of Y 2O 2S:Eu 3+,Mg 2+,Ti 4+is very slow and the luminescent mechanism is not well disclosed.The research of the long-lasting phosphors is mainly fo-cused on the bulk materials.However,one-dimensional rare-earth nanocrystals have recently attracted great attention because of their wide applications in fabrication of optical,electronic,biochemical and medical devices [6–9].If the rare earth compounds were fabricated in the form of one-dimen-sional nanostructures,they would have some new properties as a result of both their marked shape-specific and quan-tum-confinement effects.For luminescent materials,the phosphorescent properties are greatly affected by grain size,and many new properties can be obtained when the grain size reaches nanoscale.There are some methods for the prepara-tion of fine powders in nanosize,including sol-gel method,chemical precipitation,hydrothermal synthesis,and so on.The solvothermal method which exhibits some advantages of low processing temperature,high homogeneity and purity of the products has become a promising method for the prepara-tion of well-crystallized nanomaterials.Recently,some rare earth hydroxides with controlled morphology have been re-ported [10–13].As for lanthanide oxysulfides,only La 2O 2S,Gd 2O 2S and Eu 2O 2S are known as nanorods [14–16],La 2O 2Sand Nd 2O 2S as nanowires [17]and Y 2O 2S as nanotubes [11].There is still great difficulty in developing an effective route to synthesis high-quality (single-crystalline,well-shaped and phase-pure)nanocrystals.Until now the way to produce Y 2O 2S:Eu 3+,Mg 2+,Ti 4+nanorods hasrarely been reported yet.In this paper,we reported that,for the first time to our knowledge,Y 2O 2S:Eu 3+,Mg 2+,Ti 4+nanorods have been prepared by solvothermal method followed by a calcination process in CS 2atmosphere,and their photoluminescent properties were characterized at room temperature.Such Y 2O 2S:Eu 3+,Mg 2+,Ti 4+nanorods showed persistent red:10.101/1002-07210808-0896J OURNAL OF RARE EARTHS,Vol.27,No.6,Dec.2009emission after UV illumination,exhibiting potential in photoluminescent application.1Experimental Firstly,0.091mol Y 2O 3was dissolved in concentrated HNO 3.Then appropriate amount of ammonium aqueous so-lution was added dropwise.The co-precipitated powders were centrifugally separated,washed with distilled water and butanol three times,and then mixed with 40ml butonal.The solution was transferred to a teflon-lined stainless auto-clave and maintained at 260C for 5h and then cooled down to room temperature.The desired white hydroxide nanorods were filtered,washed with distilled water and ace-tone three times,and finally dried at 80C for 6h.In the second place,sulfur powder was put in a sealed graphite cru-cible,and heated to 800C for 4h.Then the dried precursor together with the mixture of 0.005mol Eu 2O 3,0.001mol Mg(OH)2.4MgCO 3.6H 2O,and 0.001mol TiO 2were placed into the graphite crucible and calcined at 1100C for 4h.Both the as-prepared Y(OH)3precursor and the final Y 2O 2S:Eu 3+,Mg 2+,Ti 4+phosphorescent products were characterized.The structures of the products were determined by powder X-ray diffraction (Bruker D8Focus).The morphologies of the powders were observed by employing scanning electron mi-croscopy (SEM,Philips XL-30),transmission electron mi-croscopy (TEM,Philips TECNAI 10)and high resolution transmission electron microscopy (HRTEM,Fei TECNAI G2F20).The photoluminescence spectra and intensity weremeasured on a fluorophotometer (Hitachi F-4500).All meas-urements were carried out at room temperature.2Results and discussion2.1Crystal structure of the product sFig.1shows pure phases of Y(OH)3precursor generated by a solvothermal process and Y 2O 2S after calcined in CS 2environment.It can be seen from the XRD patterns that both Y(OH)3and Y 2O 2S possess hexagonal structures.No impu-rity peaks are observed.As for Y 2O 2S,lattice parameters are as a=0.375nm,c=0.656nm by calculation,which are very close to the standard lattice parameters provided by the powder diffraction file,PDF #24-1424.Co-doped Eu 3+,Mg 2+and Ti 4+occupy the lattice sites in Y 2O 2S structure to form a uniform solid solution,with a nominal chemical composition of Y 2O 2S:Eu 3+,Mg 2+,Ti 4+.2.2Morphology of the Y(OH)3pr ecursorAs shown in Fig.2,Y(OH)3nanorods with uniform size and good distribution are obtained by the solvothermal method,showing the advantage of this method in preparing the particles with uniform size.A TEM micrograph is pre-sented in Fig.2(c),indicating obviously that the surface of the nanorods is smooth.2.3Morphology of the Y 2O 2S:Eu 3+,Mg 2+,Ti 4+nanorods The calcination of the Y(OH)3in CS 2atmosphere leads toFig.1XRD patterns of the obtained Y(OH)3and Y 2O 2S:Eu 3+,Mg 2+,Ti 4+nanorodsFig.2Morphology of Y(OH)3precursor ()S M ;()()T M a E image b and c E micrographsLI Wenyu et al.,Synthesis and characterization of Y2O2S:Eu3+,Mg2+,Ti4+nanorods via a solvothermal routine897the formation of Y2O2S.As shown in Fig.3,all the crystals are of rod-like shape with the width diameters of30–50nm and the lengths ranging from200to400nm.For oxysulfide products,their1D linear morphology and diameters are nearly identical to those of the initial Y(OH)3nanorods,im-plying that the rod-like shape is kept after the high tempera-ture calcination.Although the exact mechanism is not clear now,it should be mentioned that the atmosphere in which the precursor is calcined plays an important part in keeping the rod-like shape.In our previous experiments[18],when the mixture was calcined in a flowing N2,air or H2S environ-ment,only Y2O2S:Eu3+,Mg2+,Ti4+particles were obtained. In this solid-gas reaction under such high temperature,we believe that the atmosphere is a key factor of a close mor-phological retention between the starting Y(OH)3and the final products.The detailed research of the mechanism is under way.2.4HRTEM examination of the Y2O2S:Eu3+,Mg2+,Ti4+nanorodsThe Y2O2S:Eu3+,Mg2+,Ti4+nanorods were also examined by using high resolution transmission electron microscopy. From Fig.4(a)we can see individual nanorods with the di-ameter of about50nm.A HRTEM micrograph of the nano-rod is shown in Fig.4(b),from which the single crystalline nature of the nanorod is confirmed.The spacing between the two adjacent lattice planes is0.365nm,which is just in good agreement with the interplanar crystal spacing of(101)of hexagonal phase Y2O2S:Eu3+,Mg2+,Ti4+.As is revealed in Fig.4(c),the corresponding selected area electron diffrac-tion pattern obtained is quite consistent with the target Y2O2S phase.These results further confirm that the final products are pure phased and single crystalline nanorods.2.5Luminescence property of the synthesized red phosphor For the sample calcined in CS2atmosphere under1100C, the excitation spectrum,shown in Fig.5(a),consists mainly of a wide band with two peaks at about260and325nm corresponding to Eu–O CTB(charge transfer band)and Eu–S CTB.While some weak and narrow peaks are attrib-uted to the f-f transition of Eu3+ions.The emission spectrum (Fig.5(b))excited by325nm indicates typical emission of Eu3+ion.The strong red-emission lines at615and625nm are due to transition from5D0to7F2level of Eu3+ion.Either Ti4+or Mg2+ion does not change the shape of excitation and emission spectra dramatically.2.6Afterglow decay curves of the phosphor sFrom the decay curve in Fig.6,it can be seen that doping both Mg2+and Ti4+ions can result in a long afterglow oftheFig.3Morphology of Y2O2S:Eu3+,Mg2+,Ti4+(a)SEM image;(b)and(c)TEMmicrographsFig.4TEM observation of Y2O2S:Eu3+,Mg2+,Ti4+nanorod(a)TEM micrograph for a single nanorod;(b)HRTEM image of the nanorod,showing single crystalline nature;()S Dc Corresponding AE pattern898J OURNAL OF RARE EARTHS,Vol.27,No.6,Dec.2009Fig.5Excitation and emission spectra of the Y2O2S:Eu3+,Mg2+,Ti4+phosphor(a)Excitation spectrum monitored at625nm;(b)Emission spectrum excited by325nmFig.6Afterglow decay curves of the phosphors(1)Y2O2S:Eu3+nanorods;(2)Y2O2S:Eu3+,Mg2+,Ti4+nanorods Y2O2S:Eu3+phosphor.The single Eu3+doped Y2O2S:Eu3+ phosphor shows very weak afterglow while red afterglow color can be clearly seen in the dark room for codoped Y2O2S:Eu3+,Mg2+,Ti4+.Moreover,the afterglow time of Y2O2S:Eu3+,Mg2+,Ti4+nanorods can last up to1h.We pro-pose that introduction of the Mg2+and Ti4+ions to the Y2O2S compound causes the formation of new electronic donating and accepting levels between the host lattice band gap.One of the two kinds of ions absorbs energy and ther-mally transfers the excited electrons to the other kind of ions which serves as trap centers.The trapping of excited elec-trons and thermally released processes results in the after-glow.3ConclusionsSingle crystalline Y2O2S:Eu3+,Mg2+,Ti4+nanorods were prepared by solvothermal method.Results showed that the final nanorods with uniform size and smooth surface inher-ited the rod-like shape from the precursor even after calcined S W with Mg2+and Ti4+ions,the phosphorescence lasted for1h in the light perception of the naked human eye.The intro-duction of Mg2+and Ti4+ions produced the complex hole and electron traps and resulted in long-lasting phenomenon. References:[1]Lin Y H,Tang Z L,Zhang Z T,Nan C W.Anomalous lumi-nescence in Sr4Al14O25:Eu,Dy phosphors.A pplied Physics Letter,2002,81:996.[2]Jia D,Wang X,Jia W,Yen W M.Persistent energy transfer inCaAl2O4:Tb3+,Ce3+.Journal of A pplied Physics,2003,93: 148.[3]Kamada M,Murakami J,Ohno N.Excitation spectra of a long-persistent phosphor SrAl2O4:Eu,Dy in vacuum ultraviolet region.Journal of Luminescence,2000,87-89:1042.[4]Wang X X,Zhang Z T,Tang Z L,Lin Y H.Characterizationand properties of a red and orange Y2O2S-based long afterglow phosphor.Materials Chemistry and Physics,2003, 80:1.[5]Wang Y H,Wang Z L.Characterization of Y2O2S:Eu3+,Mg2+,Ti4+long-lasting phosphor synthesized by flux method.Jour-nal ofRare Earths,2006,24(1):25.[6]Wang X,Zhang J,Peng Q,Li Y D.A general strategy fornanocrystal synthesis.Nature,2005,437:121.[7]Xia Y N,Yang P D.Chemistry and Physics of Nanowires.A dvanced Materials,2003,15:351.[8]Bockrath M,Liang W J,Bozovic D,Hafner J H,Lieber C M,Tinkham M,Park H K.Resonant electron scattering by de-fects in single-walled carbon nanotube.Science,2001,291: 283.[9]Hu J T,Odom T W,Lieber C M.Chemistry and physics inone dimension:synthesis and properties of nanowires and nanotubes.A ccounts of Chemical Research,1999,32:435. [10]Wang X,Li Y D.Synthesis and characterization of lanthanidehydroxide single-crystal nanowires.A ngew andte Chemie In-ternational Edition,2002,41:4790.[11]Wang X,Sun M,Yu D P.Rare earth compound nanotubes.at C2atmosphere at high temperatures.hile co-dopedLI Wenyu et al.,Synthesis and characterization of Y2O2S:Eu3+,Mg2+,Ti4+nanorods via a solvothermal routine899Advanced Materials,2003,15:1442.[12]Yang X F,Ning G L,Lin Y.Preparation of Eu(OH)3andEu2O3Nanorods through a Simple Method.Chemistry Letters, 2007,36:468.[13]Mao Y B,Huang J Y,Ostroumov R,Wang K L,Chang J P.Synthesis and luminescence properties of erbium-doped Y2O3 nanotubes.Journal of Physical Chemistry C,2008,112:2278.[14]Jiang Y,Wu Y,Xie Y,Qian Y T.Synthesis and characteriza-tion of nanocrystalline lanthanide oxysulfide via a La(OH)3 gel solvothermal route.Journal of the A merican Ceramic So-ciety,2000,83:2628.[15]Mao S P,Liu Q,Gu M,Mao D L,Chang C K.Long lastingphosphorescence of Gd2O2S:Eu,Ti,Mg nanorods via a hydro-thermal routine.Journal ofAlloys and Compounds,2008,468: 367.[16]Zhao F,Yuan M,Zhang W,Gao S.Monodisperse lanthanideoxysulfide nanocrystals.Journal of A merican Society,2006, 128:11758.[17]Huang Y Z,Chen L,Wu L M.Crystalline nanowires of Ln2O2S,Ln2O2S2,LnS2(Ln=La,Nd),and La2O2S:Eu3+conversions via the boron-sulfur method that preserve shape.Crystal Growth &Design,2008,8:739.[18]Li W Y,Liu Y L,Ai P F.Synthesis of nanocrystalline Y2O2S:Eu3+,Mg,Ti long-lasting phosphorescent materials by hydro-thermal-microwave method.Chinese Journal of Inorganic Chemistry,2008,24:772.。

TPER

of the polymers were soluble in most common organic solvents even at room temperature, and some were soluble on heating. The degradation temperatures of the resultant polymers fell in the range of 260–500C in nitrogen (with only 10% weight loss). The speciﬁc heat capacity at 200C ranged from 1.0 to 2.21 J gÀ1 KÀ1. The temperatures at which the maximum degradation of the polymer occurred ranged from 510 to 610C. The glass-transition temperatures of the polyimides ranged from 182 to 191C. The activation energy and enthalpy of the polyimides ranged from 44.44 to 73.91 kJ/mol and from 42.58 to 72.08 kJ/mol K, respectively. The moisture absorption was found in the range of 0.23–0.71%. VC 2009 Wiley Periodicals, Inc. J Appl
1Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan 45320 2Institut fu¨ r Anorganische Chemie, J. W. Goethe-Universita¨t Frankfurt, Max-Von-Laue-Strasse 7, Frankfurt/Main, Germany 60438 3Nescom, P.O. Box 2801, Islamabad, Pakistan

功能有机材料

2.2 Photochemical Syntheses
Vollhardt’s group adopted the cobalt-catalyzed photochemical cyclotrimerization of alkynes for the rapid construction of a novel class of helicenes
The challenge in this area is to obtain materials with inherently strong chiral properties at the macromolecular level, rather than derived from an aggregate or a supramolecular structure. Such inherently strong chiral properties, approaching or exceeding in magnitude their achiral counterparts, would facilitate exploration of chiral properties of single molecule devices and the design of novel chiral materials.
3. Conclusion
Introduction
Chirality is increasingly important in the design of organic π-conjugated materials. One of the aspects of the design involves optimization of achiral properties through the introduction of chirality. In this context, the inherent threedimensional character of chirality and the control of intermolecular interactions associated with diastereomeric recognition provide a versatile handle for the optimization of supramolecular structures, film morphology and liquid crystalline order of p-conjugated polymers and oligomers in three dimensions .

催化化学书籍

催化化学书籍催化化学是化学领域中极为重要的一个分支，涉及到催化剂的设计、合成和应用等方面。

因此，有很多优秀的书籍涵盖了催化化学的理论和实践知识。

下面我将介绍一些被广泛推崇的催化化学书籍。

1. "催化化学基础"（Fundamentals of Catalysis）- Masakazu Anpo, Yutaka Ono这本书是催化化学领域的经典之作，涵盖了催化剂的种类、反应机制以及催化反应的表征等内容。

此外，该书还探讨了催化剂合成和催化剂的表面结构等相关话题。

对于学习催化化学的学生和研究人员来说，这本书是一个很好的入门指南。

2. "催化剂的设计原理"（Principles of Catalyst Design）- Challa S. S. R. Kumar 这本书系统地介绍了催化剂的设计原理和方法。

作者以反应工程和材料科学为基础，深入探讨了催化剂的制备、表征以及应用等方面。

此外，还介绍了催化剂的表面结构和反应机理的相关概念。

对于催化化学领域的研究人员和工程师来说，这本书是一本非常有价值的参考资料。

3. "现代催化科学：表征和设计"（Modern Catalysis: Surface Science Concepts and Applications）- Vladimir Ponec, Geoffrey C. Bond这本书以催化科学的最新研究进展为基础，讨论了催化剂的表征和设计方法。

书中详细介绍了表面科学的相关概念和技术，并探讨了催化剂表面结构与反应机理的关系。

此外，该书还论述了催化剂的合成和应用等实际问题。

对于从事催化化学研究和工程的科学家和工程师来说，这本书是一本不可或缺的参考书籍。

4. "催化化学原理与实践"（Catalysis: Principles and Practice）- John T. Davies 这本书是一本综合性的催化化学教科书，介绍了催化剂的种类、合成和应用方面的知识。

有机化学实验报告模板

有机化学实验报告模板Title: Synthesis and Characterization of AspirinAbstract:Introduction:Materials and Methods:1. Salicylic acid (2.0 g)2. Acetic anhydride (5.0 mL)3. Concentrated sulfuric acid (2-3 drops)4. Ethanol (30 mL)5. Distilled water6. Melting point apparatus7. Thin-layer chromatography (TLC) plates8. TLC developing chamber9. UV lamp10. Infrared (IR) spectrometerThe procedure for synthesizing aspirin involved the following steps:1. Dissolving salicylic acid in acetic anhydride and addinga few drops of concentrated sulfuric acid.3. Allowing the reaction mixture to cool and then adding it to a mixture of ethanol and distilled water to precipitate the aspirin.4. Collecting the precipitated product by filtration and washing it with cold water.5. Drying the product and determining its melting point.The synthesized aspirin was characterized using thefollowing techniques:Results and Discussion:Conclusion:In conclusion, aspirin was successfully synthesized and characterized in this experiment. The physical properties of the synthesized aspirin, such as its melting point and appearance, were in agreement with the literature values. The TLC analysis indicated the purity of the synthesized aspirin, and the IR spectrum confirmed the presence of the functional groupsspecific to aspirin. Overall, this experiment provided valuable insight into the synthesis and characterization of aspirin using various techniques in organic chemistry.。

Synthesis and Characterization of Li(Li0.23Mn0.47Fe0.2Ni0.1)O2 Cathode Material for Li-ion Batteries

retention
Li(Li0.23Mn0.47Fe0.2Ni0.1)O2 compound synthesized easily at low temperature by the proposed citric acid assisted sol-gel process is a promising cathode material for Li-ion batteries.
57
EP
TE D
(1−z)Li[Li1/3Mn2/3]O2−(z)Li[Mn0.5−yNi0.5−yCo2y]O2
M AN U
[11]. to
2
Li2MnO3–LiCo1/3Ni1/3Mn1/3O2
SC
The 4.0~4.5V)
storage power station applications. Therefore, new cathode materials with high capacity, low cost and environment friendly have been investigated thoroughly in recent years [1]. Among them the layered Li2MnO3-based solid solution materials have attracted more attention of the researchers, such as Li2MnO3-LiMO2 (M = Ni, Cr and Co) [2–5], LiNiO2–Li2MnO3–LiCoO2 [8], and [6], Li2MnO3–LiNi1−xCoxO2 [7], [9], [10], above-mentioned

Synthesis and characterization of Ce_0.8Sm_0.2O_1.9 nanopowders using an acrylamide polymerizati

J OURNAL OF RARE EARTHS,Vol.28,No.1,Feb.2010,p.92F j y S f T D f (B ),N S F f(BK 3)N B R f (B 363)SUN Y (y z_@y ;T +6556)DOI 6S ()65Synthesis and characterization of Ce 0.8Sm 0.2O 1.9nanopowders using an acrylamide polymer ization processZHENG Yingping (郑颖平)1,WANG Shaorong (王绍荣)2,WANG Zhenrong (王振荣)2,WU Liwei (邬理伟)1,SUN Yueming (孙岳明)1(1.School of Chemistry and Chemical Engineering,S outheast Univers ity,Nanjing 211189,C hina; 2.S hanghai Institute of Ceramics,Chinese Academy of Sciences,S hanghai 200050,China)Received 11May 2009;revised 10July 2009Abstract:Ce 0.8Sm 0.2O 1.9(SDC)nanopowders were synthesized by an acrylamide polymerization process.The XRD results showed that SDC powders prepared at 700°C possessed a cubic fluorite structure.Transmission electron microscopy (TEM)indicated that the particle sizes of powders were in the range of 10–15nm.A 98.3%of theoretical density was obtained when the SDC pellets were sintered at 1350°C for 5h,indicating that the powders had good sinterability.The conductivity of the sintered SDC ceramics was 0.019S/cm at 600°C and the activa-tion energy was only 0.697eV.Furthermore,a unit cell was fabricated from the powders and the maximum power density of 0.169W/cm 2was achieved at 700°C with humidified hydrogen as the fuel and air as the oxidant.Keywords:acrylamide polymerization;doped ceria;solid oxide fuel cell;sintering;electrical conductivity;rare earthsCerium oxide-based materials have attracted increasing interest as the electrolyte for solid oxide fuel cells (SOFCs),especially for intermediate temperature SOFCs (ITSOFCs,600–800°C),due to their high ionic conductivity [1–8].For example,Ce 0.8Sm 0.2O 1.9shows high ionic conductivity of around 0.1S/cm,which is three times higher than that of the conventional 8YSZ (8mol.%yttria stabilized zirconia,3×10–2S/cm)at 800°C [3,5,9].In general,nano-sized powders possess high sintering ability,and the particle size of powders greatly depends on the synthesis route.Many methods are available for the preparation of ultrafine homogeneous doped ceria powders,for instance,glycine-nitrate process [10,11],citrate-nitrate gel synthesis [12,13],carbonate coprecipitation method [14],oxalate coprecipitation route [11,15,16],homogeneous precipitation process [17],and hydrothermal process [l8].In this study,we investigated the synthesis and properties of Ce 0.8Sm 0.2O 1.9(SDC)nanocrystalline powders via an acrylamide sol-gel process.In this process,a stable precursor solution of strongly chelated cations was obtained by con-trolling the amount of ligand and the pH at first.Then the solution was easily gelled by in situ formation of poly-acrylamide gel.Fine and nano-sized powders were obtained by directly decomposing this hydrous gel through thermal treatment.Furthermore,the property of a unit cell fabricated from as-prepared powders was also studied.1Experimental1.1PreparationThe starting materials were commercial CeO 2powder and Sm 2O 3powder (purity:99.9%;Sinopharm Chemical Re-agent Co.,Ltd.,China).They were weighed according to a molar ratio of 8:2,dissolved in dilute nitrate acid separately,and then mixed with 10equivalents of EDTA.A clear solu-tion was made by slowly adding dilute ammonia under stir-ring,and pH of the solution was around 8.Then the mono-mers,acrylamide and N,N -methylenediacrylamide (6g and 1g per 100ml of solution,respectively)were added to the above solution,and then the mixture was heated at 80–90°C to produce the polyacrylamide gel.The gel was dried at 120°C overnight in an oven,and cal-cined at 700°C for 4h after being pulverized in an agate mortar to prepare crystalline SDC powders.The SDC pow-ders were pressed into pellets and sintered in air on an alu-mina board at 1350°C for 5h.The sintered pellets were ap-proximately 25mm in diameter and 0.35mm in thickness.1.2Char acter izat ionThe crystal structure of the powders was investigated with X-ray diffraction (Shimadzu XD-3A)using Cu K αradiation.The data were recorded at a scanning rate of 5(°)/min with a scanning step size of 0.02°.The morphology of the SDC powder was studied with a transmission electron microscope (TEM,JEM-2000EX).The sintering shrinkage was meas-ured with a dilatometer (NETZSCH DIL 402C)from room temperature to 1500°C.The microstructure analysis of theound at ion it em:Pro ect supporte d b the c ienti ic a nd ec hnological e ve lopment Plan o Jiangsu Province E2007014the atural cience oundat ion o Jia ngsu Province 200929and ational a si c esea rc h Program o China 2007C 900Corre sponding a uthor :ueming E-ma il:p 99ahoo.c el.:8-2-209019:10.101/1002-072109008-2ZHENG Y ingping et al.,Synthesis and characterization of Ce 0.8Sm 0.2O 1.9n anopowders using an acrylamide polymerization (93)sintered pellets was carried out using a scanning electron microscope (SEM,Hitachi X-650).The relative density of the sintered pellets was determined by standard Archimedes ’method.The ionic conductivity was measured using two-probe impedance spectroscopy.Platinum paste was applied to both sides of the sintered pellets and heated at 800°C for 2h.Measurements were performed in air using an electrochemi-cal workstation (IM6eX,Zahner)in the temperature range 600–900°C.The values of conductivity at different tem-peratures were calculated with Eq.(1):L RS=σ(1)where L is the thickness of a pellet,S the area of a pellet(S=1/4πD 2,D is the diameter),and R the resistance of a pel-let at different temperatures.The electrochemical characterization of a planar single cell was performed with humidified hydrogen as the fuel and air as the oxidant at 600–700°C using the electrochemical workstation.The anode slurry consisting of 50wt.%NiO-50wt.%SDC and cathode slurry consisting of 50wt.%La 0.8Sr 0.2MnO 3(LSM)-50wt.%SDC were deposited by a screen-printing technique onto the separate sides of SDC pellet,which was air-dried and then fired at 1000°C for 2h in air.Platinum mesh was placed on top of the anode and the cathode to act as current collectors.2Results and discussion2.1Powder characterist icsFig.1shows XRD pattern of calcined SDC powder at 700°C for 4h with an acrylamide polymerization route.The powder has a fluorite structure,and its pattern is indexed on a cubic cell,space group F23with lattice parameters of a=b=c=0.5430nm,a=β=γ=90°.TEM image of the SDC nanoparticles is shown in Fig.2.It can be seen that the nanoparticle is well-crystallized with average grain size of 12nm;and the particles are slightly agglomerated,which may be due to the partial sintering while the exothermic reactions occur.Fig.3shows the sintering curve of the compact powder sample.It can be seen that the linear shrinkage begins tode-F XRD f SD scend after 700°C.A maximum shrinkage of the sampleoccurs at near 1400°C.With further increasing of the tem-perature,the sintering curve begins to rise.Therefore,the sintering temperature of the SDC was chosen between 1350–1400°C.2.2Char acter izat ion of sint ered SDC pelletsA typical SEM image of the SDC pellet sintered at 1350°C for 5h (Fig.4(a))reveals a dense and homogeneous micro-structure,and the average grain size is 1–2μm.Fig.4(b)pre-sents the microstructure of a fractured section of the pellet.The pellet is basically dense although there are closed pores of submicron-size at the grain boundaries.The relative den-sity of SDC pellet was found to be 98.3%by the standard Archimedes ’method.The ionic conductivity was measured using two-probe impedance spectroscopy.The conductivity data were fitted with the Arrhenius Eq.(2):0expa E T kT=σσ(2)where σ,σ0,E a ,k and T are the conductivity,pre-exponential factor,activation energy,Boltzmann constant and absolute temperature,respectively.Fig.5presents the Arrhenius plots for the sintered SDC pellet prepared by different methods.The ionic conductivity of the pellet prepared by acrylamide polymerization method is 0.019S/cm at 600°C,and the ac-tivation energy is 0.697eV.As comparison,the data of pel-lets prepared by glycine-nitrate method and citrate-nitrate method are also shown in Fig.5.Fig.2TEM image of SDCpowderF 3S f y z ig.1pattern o C powder ig.intering curve o the s nthesi ed powder compact sample94JOURNAL OF RARE EARTHS,Vol.28,No.1,Feb.2010Fig.4SEM micrographs of SDC sintered at 1350°C for 5h(a)Surface;(b)FractureFig.5Arrhenius plots for SDC pellets sintered at 1350°C for 5hfrom powders prepared by different methodsFrom Fig.5,it can be found that pellets prepared by acrylamide polymerization method have a lower activation energy and higher conductivity.This result shows that the acrylamide polymerization synthesis is an effective method to prepare doped ceria powders with an excellent electrical performance.Acrylamide gel consists of long polymeric chains,crosslinked to create an organic 3D tangled network where a solution of the respective cations is soaked.Polym-erization of the gel proceeds with the way of a chain reaction,the first step of which is the combination of an initiator with the acrylamide,which is thereby activated.As the chain of polyacrylamide grows,the active site shifts to its free end.N,N ’-methylenediacrylamide,which contains two acryla-mide units joined through –CONH 2group via a methylene group,can link two growing chains.Hence,diacrylamide enables the formation of cross-linked chains,resulting in a x y ,,[]M x f y DT x f and avoids the occurrence of unwanted precipitation.So this method allows preparing uniformly doped ceria powders.2.3Cell test result sThe cell structure consists of a porous NiO-SDC anode,a dense SDC electrolyte and a porous LSM-SDC composite cathode.The electrochemical performance of as-prepared unit cell was characterized.I-V curves and power densities are shown in Fig.6(a),and its impedance spectra measured at an open circuit condition for the cell are shown in Fig.6(b).The measured results are also listed in Table 1.From Fig.6(a),it can be found that I-V curves are non-linear,which indicates the presence of a significant polariza-tion at the electrode/electrolyte interface.As the temperature rises,the current density and power density rise.A maxi-mum power density of 0.169W/cm 2is achieved at 700°C.This value is a little low,but it must be noticed that the thickness of the SDC electrolyte is 350μm.From Table 1,it is very clear that the values of electrolyte resistance,R el ,and electrode polarization resistance,R p,a+c ,have increased significantly along with the increase in the OCV values.Meanwhile,the values of R el ,R p ,a+c ,and OCV decrease with the increase of temperature.The electrolyte resistance (R el )have decreased from 1.247to 0.556Ωcm 2as temperature increases from 600to 700°C.Fig.6I-V curves of a single cell at different temperatures (a),andimpedance spectra measured at an open circuit condition for the single cell (b)Table 1Cell performance and cell resistances *Temperature/°C OCV/V MPD/(W/cm 2)R el /(cm 2)R p ,a+c /(cm 2)R cel l /(cm 2)6000.8560.054 1.247 3.210 4.4576500.8350.0940.891 1.561 2.4527000.8050.1690.5561.1881.744*OCV:open circuit voltage,MPD:maximum power dens ity,R el :electrolyte oh-f IS,R ,+z f IS,R f IS (R =R +R ,+)com ple topo log with loops branches and interconnec-tions 19.eanwhile the comple ation o cations in solu tion b E A perm its the mi ing o species at a molecular levelmic resistance rom E p a c :electrode polari ation resistance rom E cell :cell res istance rom E c ell el p a cZHENG Y ingping et al.,Synthesis and characterization of Ce0.8Sm0.2O1.9n anopowders using an acrylamide polymerization (95)In comparison with R el of cells with thin SDC electrolytes (10μm)[20],the relative high value of R el may be related to the thicker electrolyte pellet.As shown in Table1,the elec-trode polarization resistance(R p,a+c)is dominant in the total resistance of the cell(R cel l),which is decreased from3.210 to1.188Ωcm2as temperature increases from600to700°C. Therefore,a better performance of the unit cell can be achieved at700°C.In order to further improve the cell per-formance,it is necessary to decrease the thickness of the electrolyte pellets and enhance catalytic activity of the elec-trode materials to lower the R c ell of unit cells.3ConclusionsCe0.8Sm0.2O1.9powder of12nm in average grain size was successfully synthesized by an acrylamide polymerization process.The SDC powder exhibited high sinterability,high conductivity,and low conduction activation energy.With an electrolyte pellet of350μm thick,a fuel cell with humidified hydrogen as the fuel and air as the oxidant was assembled and a maximum power density of0.169W/cm2was obtained at700°C.It is believed that SDC powders synthesized by this method would be a promising electrolyte material for intermediate temperature SOFCs.References:[1]Eguchi K.Ceramic materials containing rare earth oxides forsolid oxide fuel cell.Journal of A lloy s and Compounds,1997, 250:486.[2]Inoue T,Setoguchi T,Eguchi K,Arai H.Study of a solid oxidefuel cell with a ceria-based solid electrolyte.Solid State Ionics, 1989,35:285.[3]Yahiro H,Baba Y,Eguchi K,Arai H.High temperature fuelcell with ceria-yttria solid electrolyte.Journal of the Electro-chemical Society,1988,135:2077.[4]Tompsett G A,Sammes N M,Yamamoto O.Ceria-yttria-sta-bilized zirconia composite ceramic systems for applications as low-temperature electrolytes.Journal of the A merican Ce-ramic Society,1997,80:3181.[5]Mogensen M,Sammes N M,Tompsett G A.Physical,chemi-cal and electrochemical properties of pure and doped ceria.Solid State Ionics,2000,129:63.[6]Eguchi K,Setoguchi T,Inoue T,Arai H.Electrical propertiesof ceria-based oxides and their application to solid oxide fuelcells.Solid State Ionics,1992,52:165.[7]Hibino T,Hashimoto A,Inoue T,Tokuno J I,Yoshida S I,Sano M.A low-operating-temperature solid oxide fuel cell in hydrocarbon-air mixtures.Science,2000,288:2031.[8]Sahibzada M,Steele B C H,Zheng K,Rudkin R A,Metcalfe IS.Development of solid oxide fuel cells based on a Ce(Gd)O2x electrolyte film for intermediate temperature op-eration.Catalysis Today,1997,38:459.[9]Yahiro H,Baha Y,Eguchi K,Arai H.Oxygen ion conductivityof the ceria-samarium oxide system with Fluorite.Journal of Applied Electrochemistry,1988,18:527.[10]Peng R R,Xia C R,Fu Q X,Meng G Y,Peng D K.Sinteringand electrical properties of(CeO2)0.8(Sm2O3)0.1powders pre-pared by glycine-nitrate process.Materials Letters,2002,56: 1043.[11]Peng R R,Xia C R,Peng D K,Meng G Y.Effect of powderpreparation on(CeO2)0.8(Sm2O3)0.1thin film properties by screen-printing.Materials Letters,2004,58:604.[12]Peng C,Zhang Y,Cheng Z W,Cheng X,Meng J.Nitrate-citrate combustion synthesis and properties of Ce1–x Sm x O2–x/2 solid solutions.Journal of Materials Science:Materials in Electronics,2002,13:757.[13]Song X W,Peng J,Zhao Y W,Zhao W G,An S L.Synthesisand electrical conductivities of Sm2O3-CeO2systems.Journal ofRare Earths,2005,23:167.[14]Moria T,Drennanb J,Wang A Y,Aucheerlonie G,Li J,YagoA.Influence of nano-structural feature on electrolytic proper-ties in Y2O3doped CeO2system.Science and Technology of Advanced Materials,2003,4:213.[15]Gao R F,Mao Z Q.Sintering of Ce0.8Sm0.2O1.9.Journal ofRare Earths,2007,25:364.[16]Van Herle J,Horita T,KawadaT,Sakai N,Yokokana H,DokiyaM.Low temperature fabrication of(Y,Gd,Sm)-doped ceria electrolyte.Solid State Ionics,1996,86-88:1255.[17]Djuricic B,Pickering S.Nanostructured cerium oxide:prepa-ration and properties of weakly-agglomerated powders.Jour-nal ofthe European Ceramic Society,1999,19:1925.[18]Dikmen S,Shuk P,Greenblatt M,Gomez H.Hydrothermalsynthesis and properties of Ce1-x Gd x O2-δsolid solutions.Solid State Sciences,2002,4:585.[19]Sin A,Odier P.Gelation by acrylamide,a quasi-universal me-dium for the synthesis of fine oxide powders for electroce-ramic applications.Advanced Materials,2000,12:649 [20]Zhang X,Robertson M,Deces-Petit C,Qu W,Kesler O,MaricR,Ghosh D.Internal shorting and fuel loss of a low tempera-ture solid oxide fuel cell with SDC electrolyte.Journal of Power Sources,2007,164:668.。

2023申请博士点材料公示

2023申请博士点材料公示英文回答：Research Proposal on the Synthesis and Characterization of Novel Nanomaterials for Advanced Energy Storage Applications.Introduction.The urgent need to address global energy challenges and the increasing demand for portable electronic devices have spurred significant interest in the development of advanced energy storage systems. Nanomaterials, with their unique properties and tailored electrochemical performance, have emerged as promising candidates for this purpose. This research proposal aims to synthesize and characterize novel nanomaterials with tailored structures and compositions for enhanced energy storage performance.Objectives.The primary objectives of this research are:To synthesize novel nanomaterials with controlled morphology, size, and composition.To investigate the fundamental electrochemical properties of the synthesized nanomaterials.To optimize the synthesis parameters to achieve desired electrochemical performance.Methodology.The proposed research will employ various synthesis techniques, including hydrothermal, solvothermal, and electrodeposition, to synthesize nanomaterials with controlled morphologies and compositions. The synthesized nanomaterials will be characterized using advanced characterization techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and electrochemical impedancespectroscopy (EIS).Expected Outcomes.The expected outcomes of this research include:The development of novel nanomaterials with tailored structures and compositions.A comprehensive understanding of the structure-property relationships of the synthesized nanomaterials.Optimized synthesis parameters for achieving desired electrochemical performance.The identification of promising nanomaterials for advanced energy storage applications.Significance.This research has significant implications for the development of advanced energy storage systems. Thesynthesized nanomaterials with enhanced electrochemical properties could lead to the development of high-performance batteries, supercapacitors, and fuel cells. Furthermore, this research will contribute to the fundamental understanding of nanomaterial synthesis and electrochemistry, paving the way for the design and optimization of next-generation energy storage devices.中文回答：纳米材料在先进储能应用中的合成与表征研究。

硝酸银与三乙醇胺的反应方程式

硝酸银与三乙醇胺的反应方程式概述硝酸银（AgNO3）与三乙醇胺（C6H15NO3）之间的反应是一种重要的有机合成反应。

这个反应可以用于合成银纳米颗粒、有机银盐等化合物。

在本文中，我们将详细介绍硝酸银与三乙醇胺的反应方程式、反应机理、实验条件以及应用领域。

反应方程式硝酸银与三乙醇胺的反应方程式如下所示：3 AgNO3 + C6H15NO3 → Ag(C6H15NO3)3 + 3 HNO3在这个反应中，硝酸银和三乙醇胺发生反应生成三乙醇胺银盐和硝酸。

反应机理硝酸银与三乙醇胺的反应机理可以分为以下几个步骤：1.银离子（Ag+）和硝酸根离子（NO3-）在溶液中解离，生成Ag+和NO3-离子；2.三乙醇胺分子中的氢氧根离子（OH-）与Ag+离子发生配位作用，生成AgOH配合物；3.AgOH配合物进一步与三乙醇胺分子中的氢氧根离子发生配位作用，生成三乙醇胺银盐（Ag(C6H15NO3)3）；4.反应过程中产生的硝酸根离子与H+离子结合，生成硝酸（HNO3）。

实验条件实验中，硝酸银与三乙醇胺的反应需要在适当的温度和pH条件下进行。

一般来说，室温下反应进行得较慢，因此可以加热反应溶液来加快反应速率。

此外，反应溶液的pH值也会影响反应速率和产物的形成。

应用领域硝酸银与三乙醇胺的反应在许多领域中具有重要的应用价值。

合成银纳米颗粒硝酸银与三乙醇胺的反应可以用于合成银纳米颗粒。

在实验中，将硝酸银和三乙醇胺溶液混合并加热，可以观察到溶液的颜色由无色逐渐变为黄色，最终变为棕色。

这是由于反应过程中产生的银纳米颗粒的表面等离子共振效应导致的。

合成的银纳米颗粒可以在光学、生物医学等领域中应用。

有机银盐的合成硝酸银与三乙醇胺的反应还可以用于合成有机银盐。

有机银盐是一类重要的有机化合物，具有广泛的应用。

通过将硝酸银和三乙醇胺反应，可以得到三乙醇胺银盐。

这种有机银盐可以用作催化剂、抗菌剂等。

光学材料硝酸银与三乙醇胺的反应产物三乙醇胺银盐具有良好的光学性质，可以用于制备光学材料。

SYNTHESIS AND CHARACTERIZATION OF POLYROTAXANES MADE FROM α-CDs THREADED ONTO TRIBLOCK COPOLYME

,
份
,,
”
一
,
一
可卿
,
〕
一
一
,
一
。
一
,
而
一一
,
,
为
办班在
一一一 ,
而
一一
咖
, 一
科
,
一
,
而
一
,
一
一
一
一
一
,
,
又尸
‘ 一
一一一、
,
一
一
,
,
一
一
,
即
一之互
,
一
一
,
一
,
、
,
一
即
、
登
一
,
、
一
,
,
一
一、一
’
扬
’
门
一
一
一一 , 一乏
一
,
,
,
介〔
一
一
之
一
、
」
〕
,
一
一
、
,
,
们
,
、一、、一
一
一
哪
奋拼
,
一
一
,
于
尸
一一一
以抚一乃一
一
〔功
八
八
、
,
六
、
,
一一
, ,
,
孔
一
。丫
一
一
一
、
矛
一
一一
一
一
一一
‘
一

四氨基硝酸钯

四氨基硝酸钯引言四氨基硝酸钯（Pd(NO2)4）是一种重要的红色固体化合物，由钯离子和四个硝酸根离子（NO2）形成。

本文将讨论四氨基硝酸钯的结构、制备方法、性质及其在化学领域中的应用。

结构四氨基硝酸钯的结构由钯离子和四个硝酸根离子（NO2）组成。

每个钯离子均与四个硝酸根离子形成配位键。

硝酸根离子中的氮和氧原子与钯离子形成键合，形成了四面体结构。

该配位化合物的结构稳定性较高，可在不同温度和压力条件下存在。

制备方法四氨基硝酸钯的制备方法可以通过在硝酸钯溶液中加入氨水来实现。

首先，将硝酸钯溶解于水中，然后缓慢滴加氨水。

加入氨水后，溶液中的钯离子与氨水中的氨离子发生配位反应，形成四氨基硝酸钯沉淀。

最后，将沉淀加热至适当温度，得到红色固体四氨基硝酸钯。

性质四氨基硝酸钯是一种具有高度氧化性的化合物。

它具有以下主要性质：1.颜色：四氨基硝酸钯呈现出红色固体的形式。

2.溶解性：它可溶于水和一些有机溶剂，如醇类和醚类。

3.热稳定性：四氨基硝酸钯在室温下稳定，但在高温条件下会分解产生氧气和一氧化氮气体。

4.氧化性：它是一种强氧化剂，在化学反应中常被用作氧化剂。

应用四氨基硝酸钯在化学领域中有广泛的应用。

以下是其中一些主要应用：1.催化剂：四氨基硝酸钯在有机合成反应中常用作催化剂，如氢化反应、氧化反应和具有还原性的反应。

它可促进反应的进行，提高反应速率和产率。

2.金属染色剂：四氨基硝酸钯可用作金属染色剂，用于染色不锈钢、镍和其他金属，使其具有不同的颜色。

3.颜料：它也可用作颜料的成分，用于染色陶瓷、玻璃和塑料等材料。

4.电子材料：四氨基硝酸钯在电子材料中的应用较多，包括作为电容器和传感器等元件的电极材料。

结论四氨基硝酸钯是一种重要的化合物，在化学领域中有广泛的应用。

无论是作为催化剂、金属染色剂还是颜料和电子材料的成分，它都发挥着重要的作用。

通过深入了解四氨基硝酸钯的结构、制备方法和性质，我们能更好地应用它，并进一步推动化学科学的发展。

Synthesis and characterization of antimony-doped tin oxide (ATO) nanoparticles by a new hydrothermal

Materials Chemistry and Physics87(2004)10–13Materials science communicationSynthesis and characterization of antimony-doped tin oxide(ATO) nanoparticles by a new hydrothermal methodJianrong Zhang,Lian Gao∗State Key Lab of High Performance Ceramics and Superﬁne Microstructure,Shanghai Institute of Ceramics,Chinese Academy of Sciences,Shanghai200050,PR ChinaReceived31March2004;received in revised form21May2004;accepted7June2004AbstractAntimony-doped tin oxide(ATO)nanoparticles have been synthesized by mild hydrothermal method free from the widely used metal chlo-rides.The obtained particles were characterized by means of XRD,BET,Hall effect measurements,XPS and TEM.X-ray diffraction shows that all Sb ions came into the SnO2lattice to substitute Sn ions,though the hydrothermal temperature was as low as120◦C.Increasing the heat treatment temperature accelerates the growth of the nanoparticles,changes the electrical conductivity,the distribution of the Sb ions and relative amount of the two oxidation states Sb5+and Sb3+.TEM shows the ATO nanoparticles were monodispersed in the range of3–5nm.©2004Elsevier B.V.All rights reserved.Keywords:Tin(IV)oxide;Doping;Hydrothermal synthesis;XPS1.IntroductionAntimony-doped tin oxide(ATO)is an important mem-ber of transparent conductive oxides(TCOs)[1–3]that hasbeen extensively studied for its chemical,mechanical andenvironmental stabilities[4].ATOﬁlms are highly conduct-ing,and electrons can tunnel easily in either direction be-tween the adsorbed electroactive species and the SnO2con-duction band[5].The introduction of Sb into the tin oxidelattice greatly increases the electron conductivity,which ren-ders this material used as an excellent conductive agent[6].ATO is transparent throughout the visible region,while re-ﬂects infrared light.These features enable ATO to be used astransparent electrodes,heat mirrors and energy storage de-vices,have potential uses in photovoltaic and optoelectronicdevices[7,8].Nanoparticulate ATO has been used as elec-trochromic material for the production of printed displays[9]and anode material in lithium-ion batteries[10].In ad-dition,ATO has applications in nuclear waste management,good catalyst for oleﬁn oxidation[11,12].So far,ATO particles have been synthesized by solid-statereaction[13],coprecipitation[6,7,9],Pechini[13]and hy-drothermal methods[14].The coprecipitation improves the∗Corresponding author.Tel.:+86-21-5241-2718;fax:+86-21-5241-3122.E-mail address:liangaoc@(L.Gao).reactivity of the components and Pechini method enhancesthe chemical homogeneity.But a post-calcination at over500◦C is required to incorporate Sb atoms into the tin ox-ide lattice;as a consequence,a large particle size and heavydegree of agglomeration are rge amount oforganic compounds employed in the Pechini method act notonly as complexes,but also as fuel,evolving much heat dur-ing calcination,which accelerates the growth and agglomer-ation of obtained ATO particles.The hydrothermal methoddoes not need a calcination process,and the dispersity ofthe particles is greatly improved,but a comparatively highhydrothermal temperature(270◦C)is needed.The startingmaterials used in the wet chemical methods are all frommetal chlorides,such as SnCl4,SnCl2,SbCl3and SbCl5.Itis well known that chlorine ions adsorbed on tin hydrox-ide are very difﬁcult to be removed,and large amount ofproduct is lost during the repeated washing.The residualchlorine ions affect the surface and electrical properties,leading to both volatile antimony and tin compounds,caus-ing agglomeration among particles and sintering to highertemperature[15].For these reasons,new methods shouldbe developed to improve the yield and quality of ATOnanoparticles.In this paper,we report a new method for direct synthesisof conductive ATO nanoparticles with high speciﬁc surfaceareas by mild hydrothermal process from the starting mate-rials granulated tin and Sb2O3.The inﬂuence of hydrother-0254-0584/$–see front matter©2004Elsevier B.V.All rights reserved.doi:10.1016/j.matchemphys.2004.06.004J.Zhang,L.Gao /Materials Chemistry and Physics 87(2004)10–1311mal treatment temperature on the crystallite size,lattice pa-rameters,electrical conductivity and surface properties of the ATO nanoparticles is discussed.2.ExperimentalIn a typical synthesis,30mL of concentrated HNO 3(67wt.%)was poured into a stainless Telfon-lined 100-mL capacity autoclave containing 2g of granulated tin (pu-rity 99.95%),calculated amount of Sb 2O 3(the molar ratio [Sb]/[Sn]was set at 5:100in all reactions)and 50mL of H 2O.A large amount of brown gas (NO 2)gave off immedi-ately,and the mixed starting materials turned into a yellow colloid.The autoclave was sealed and heated to maintain at 120–170◦C for 10h,and then air-cooled to room tempera-ture.The resulting blue-colored products (characteristic of ATO particle)were collected and washed with water and enthanol,ﬁnally dried at 100◦C for 5h.The ATO nanoparticles obtained at different hydrother-mal temperatures were characterized by powder X-ray diffraction (XRD)(Model D/MAX 2550v;Rigaku Co.,Tokyo,Japan)with λ=0.15418nm,Cu K ␣and transmis-sion electron microscopy (TEM)(JEM-200CX TEM).The speciﬁc surface area of the powders was measured with a Micromeritics ASAP 2010analyzer using the multipoint Brunauer,Emmett and Teller (BET)adsorption and the av-erage grain size (d BET )of the particles were calculated from the formula d =6/ρA ,where ρis the theoretical density of SnO 2and A is the speciﬁc surface area of the powder.The conductivity of the 500MPa uniaxially pressed pellets was measured by the Hall effect measurements.The X-ray photoelectron (XPS)measurements were carried out at Mi-crolab 310-F Spectrometer with an X-ray gun for Mg K ␣radiation.The step width was 0.1eV and the spectra were referred to C1s emission at 284.6eV .3.Results and discussionFig.1shows the XRD patterns of the ATO nanoparticles.All peak positions agree well with the reﬂections of bulk cassiterite SnO 2.No phase ascribed to antimony compounds was detected,indicating that all antimony ions came into the lattice of bulk SnO 2to substitute for tin ions [7].The widths of the reﬂections were considerably broadened,and the av-Table 1Characterizations of the hydrothermally synthesized ATO nanoparticles Hydrothermal temperature (◦C)Lattice parameter D XRD (nm)Surface area (m 2g −1)d BET (nm)Conductivity (102S cm −1)a (Å)c (Å)V (Å3)120 4.758 3.18472.08 2.7234 3.72140 4.737 3.18671.49 3.2216 4.081704.7533.17871.794.01874.661020304050607080(310)(002)(220)(211)(200)(101)(110)(c)(b)(a)I n t e n s i t y /(a .u .)2θ/(o)Fig.1.XRD patterns of the ATO nanoparticles hydrothermally synthe-sized at different temperatures:(a)at 120◦C;(b)at 140◦C;(c)170◦C,respectively.erage crystallite sizes of the particles determined from the (110)plane by the Scherrer’formula were listed in Table 1.The size increased from 2.7nm at 120◦C to 3.2nm at 140◦C and 4.0nm at 170◦C,respectively.To the authors’knowl-edge,the speciﬁc surface areas are the largest,correspond-ingly decreased from 234m 2g −1at 120◦C to 187m 2g −1at 170◦C,which witnessed the growth of the nanoparti-cles.The much high surface areas may be ascribed to the free of Cl −ions that cause agglomeration among particles and the advantage of hydrothermal synthesis.The compar-ison of the crystallite size and the particle size calculated based on the surface area reveals that the nanoparticles are almost monodispersed.The lattice parameters determined by least-squares reﬁnement are listed in Table 1.The unit cell volume of the sample obtained at 120◦C (72.08Å3)is larger than the pure SnO 2(71.56Å3JCPDS 21–1250),de-creased to 71.49Å3at 140◦C,again increased to 71.79Å3at 170◦C,respectively.The reason can be explained as fol-lows.On one hand,nanocrystalline oxide particles exhibit a lattice expansion with reduction in particle size [16].On the other hand,the antimony incorporated into the SnO 2lat-tice exists in two oxidation states,Sb(III)and Sb(V);the Sb(V)has a smaller ionic radius (r =0.60Å)than tin ion (r =0.69Å),while Sb(III)ion (r =0.76Å)is larger than tin ion [7].So,the Sb(III)/Sb(V)content ratio can change the lattice parameters.Taking no consideration of the expansion of the crystallite size on the lattice parameters,we suppose that in the 120◦C sample,most of the Sb ions are in Sb(III)12J.Zhang,L.Gao /Materials Chemistry and Physics 87(2004)10–13oxidation state;so,the unit cell volume is much larger than pure tin oxide.When the hydrothermal temperature was in-creased to 140◦C,most of the Sb(III)ions are oxidated to Sb(V);as a result,the cell volume decreased,even smaller than pure tin oxide.Further increase in the temperature to 170◦C,most of the Sb(V)ions again reduced to Sb(III)or some of the Sb ions are separated to the grain surface and the cell volume increased.This supposition can be supported by the electrical measurements and X-ray photoelectron spec-troscopy (XPS).The electrical conductivities of the ATO nanoparticles were also shown in Table 1.The conductivities were several orders of magnitude higher than the pure SnO 2,increased from 2×102S cm −1at 120◦C to the highest value at 140◦C,8×102S cm −1,and again reduced to 6×102S cm −1at 170◦C,respectively.These values are lower than the dense ATO ﬁlms [17],which are ascribed to a high activation energy for electron to cross the grain boundaries between the nanoparticles.The conductivity mechanism of the ATO material is well known,the Sb(V)ions incorpo-rated into the SnO 2lattice act as an electron donors,while the Sb(III)ions compensate the donor electrons.At higher calcination temperatures (>600◦C)[18],the antimony ions incline to segregate to the grain boundary,trapping an electron pair in the bulk bandgap [19].So,the change of conductivity with the hydrothermal temperature is ascribed to the change of Sb(V)/Sb(III)ratio or the segregation of Sb.To further elucidate the relation between lattice param-eter and electrical conductivity of the ATO nanoparticles,we investigated the surface properties of the ATO materi-als by XPS,which is powerful to obtain surface informa-tion of the ATO particles [16].Because of overlapping of O1s and Sb3d5/2lines,the Sb3d3/2line is used to deter-mine the Sb concentration by making use of the relation between the prewave of Sb3d5/2and Sb3d3/2ratio ﬁxed to be 1.44.A typical entire spectrum of the particles ob-tained at 140◦C is shown in Fig.2.The binding energy of1000800600400200I n t e n s i t y /C P S Binding Energy/(eV)Fig.2.XPS survey spectrum of the nanoparticles hydrothermally synthe-sized at 140◦C.Table 2XPS investigations of the ATO nanoparticles obtained at different tem-peratures Hydrothermal temperature (◦C)Binding energy (eV Sb3d3/2)[Sb 5+]/[Sb](%)Sb surface enrichment 120539.6521140539.8087 1.3170539.72533.2the Sb3d3/2as a function of hydrothermal temperature is shown in Table 2.As can be seen,the binding energy shifts from 539.65eV at 120◦C to 539.80eV at 140◦C,again de-creases to 539.70eV at 170◦C,respectively.The shift to higher binding energy declares that an increasing amount of Sb ions are in the oxidation state +5.The distribution be-tween Sb 3+and Sb 5+,and surface enrichment of Sb ions were also listed in Table 2.In the 120◦C hydrothermally treated sample,almost all the Sb ions are in the oxidation state +3,which leads to a lattice expansion and a low electri-cal conductivity.The Sb ions are homogeneously distributed in the material and shows no Sb surface enrichment.Increas-ing the treatment temperature to 140◦C,most of the Sb ions are oxidated to Sb 5+and evolve large amount of electrons,the unit cell volume decreased sharply,the Sb ions showed a tendency to segregate to the surface of the ATO nanopar-ticles.Further increase in the temperature to 170◦C,more Sb ions are segregated to the particle surface and the surface enrichment increases to about 2.5,which had been observed by other authors [20,21].The enriched Sb ions are in the oxidation state +3,as a consequence,the unit cell volume shrinks and the electrical conductivity decreases.What the XPS results correlates perfectly with the XRD and electricalmeasurements.Fig.3.TEM image of the ATO nanoparticles obtained at 140◦C.J.Zhang,L.Gao/Materials Chemistry and Physics87(2004)10–1313The mechanism of the formation of conductive ATOnanoparticles at comparatively low temperature can bedescribed as follows.As HNO3was added to the mixedstarting materials,a reaction occurred3Sn+Sb2O3+6H+→3Sn2++2Sb+3H2OThen,the excessive HNO3also oxidized the unreactedSn and freshly obtained Sn2+,Sb,rendering these metalions highly activated,which was evidenced by the appear-ance of the colloid.In the following hydrothermal pro-cess,the antimony ions were very easy to incorporate intoSnO2lattice and endow the nanocrystals with electricalconductivity.Fig.3shows TEM image of the ATO nanoparticles hy-drothermally treated at140◦C.All particles have a size rang-ing from3–5nm,average size of4nm with well-deﬁnededges.The nanoparticles were monodispersed in accordancewith what the above had revealed.4.ConclusionsMonodispersed ATO nanoparticles with high speciﬁc sur-face areas has been synthesized by hydrothermal method.The method free form chlorides shortened the synthesisprocess and improve the particle quality,the use of acti-vated intermediates greatly decreased the hydrothermal tem-perature to120◦C.The highest electrical conductivity(8×102S cm−1)is obtained at a hydrothermal temperature 140◦C,accompanied with the smallest unit cell volume(71.49Å3)and the highest Sb5+concentration,about87%of the Sb ions are in the oxidation state Sb5+.This methodputs forward a new strategy to synthesize multicomponentnanocrystalline oxides.References[1]T.T.Emons,J.Q.Li,L.F.Nazar,J.Am.Chem.Soc.124(2002)8516.[2]C.Goebbert,R.Nonninger,M.A.Aegerter,A.Schmidt,Thin SolidFilms351(1999)79.[3]K.Y.Rajpure,M.N.Kusumade,M.N.Neumann-Spallart, C.H.Bhosale,Mater.Chem.Phys.64(2000)184.[4]A.Gamard,O.Babot,B.M.C.Jousseaume Rascle,T.Toupance,G.Campet,Chem.Mater.12(2000)3419.[5]G.C.Jorge,P.M.Andrew,urence,D.W.Michael,Angew.Chem.Ed.42(2003)3011.[6]Z.C.Orel,B.Ore,M.Hodoscek,V.Kaucic,J.Mater.Sci.27(1992)313.[7]J.Rockenberger,U.Felde,M.Tisher,L.Troger,M.Haase,H.Weller,J.Chem.Phys.112(2000)4296.[8]H.S.Varol,A.Hinsch,Sol.Energ.Mat.Sol.C40(1996)273.[9]J.P.Coleman,J.J.Freeman,P.Madhukar,J.H.Wagenknecht,Displays20(1999)145.[10]A.C.Bose,D.Kalpana,P.Thangadurai,S.Ramasamy,J.PowerSource107(2002)138.[11]V.Dusatre,D.E.William,J.Phys.Chem.B102(1998)6732.[12]R.koivula,R.Hajula,J.Lehto,Micropor.Mesopor.Mater.55(2002)231.[13]M.I.B.Bernardi,S.Cava,C.O.P.Santos,E.R.Leite,C.A.Paskocimas,E.Longo,J.Eur.Ceram.Soc.22(2002)2911.[14]T.Nuta,U.Felde,M.Haase,J.Chem.Phys.110(1999)12142.[15](a)O.Vasykiv,Y.Sakka,J.Am.Ceram.Soc.84(2001)2489;(b)J.S.Pena,T.BrousseL.Sanchez,J.Morals,D.M.Schleich,J.Power Sources9798(2001)232;(c) A.Roosen,H.Hausener,Adv.Ceram.Mater.3(1988)131.[16]P.Vaqueiro,M.A.Lopez-Quintela,Chem.Mater.9(1997)2836.[17]K.Y.Rajpure,M.N.Kusumade,M.N.N.Spallart, C.H.Bhosale,Mater.Chem.Phys.64(2000)184.[18]K.Sun,J.Liu,N.D.Browning,J.Catal.205(2002)266.[19]R.G.Egdell,T.J.Walker,G.Beamson,J.Electron.Spectrosc.Relat.Phenomena128(2003)59.[20]D.Szczuko,J.Werner,S.Ostwald,S.G.Behr,K.Wetzig,Appl.Surf.Sci.179(2001)301.[21]J.C.V olta,P.Bussiere,G.Coudurier,J.Herrmann,J.C.Vedrine,Appl.Catal.16(1985)315.。

Synthesis and characterization of ATO SiO2 nanocomposite coating obtained by sol–gel method

Synthesis and characterization of ATO/SiO 2nanocompositecoating obtained by sol–gel methodXiaoChuan Chen *The Key Laboratory of Materials Physics,Institute of Solid State Physics,Chinese Academy of Sciences,Hefei 230031,People’s Republic of ChinaReceived 19June 2004;accepted 20December 2004Available online 11January 2005AbstractA new sol–gel route was developed for synthesizing homogeneous nanocomposite thin film that was composed of Sb-SnO 2(ATO)nanoparticles and silica matrix.TEM studies show that as-prepared composite thin film contains the amorphous silica matrix and ATO nanocrystalline particles that were dispersed homogeneously in silica matrix.The oxalic acid is an excellent dispersant for colloidal stability of ATO aqueous sol at pH b 5.The result of Zeta potential measurement shows that dispersion mechanism comes from the chemisorption of oxalic acid on the surface of ATO nanoparticles.The thermal treatment in reducing atmosphere considerably promotes grain growth of ATO nanoparticles and changes the optical property of ATO/SiO 2nanocomposite thin film.D 2005Elsevier B.V .All rights reserved.Keywords:Sol–gel preparation;Thin films;Nanocomposites;Sb-doped SnO 21.IntroductionTin oxide is a wide band gap nonstoichiometric semi-conductor with a low n-type resistivity [1–3].The resistance can be reduced further by doping Sb,F elements [4,5].F-doped SnO 2(FTO),Sb-doped SnO 2(ATO)conducting thin films not only have high transparency in the visible region but also are good infrared reflecting materials [6,7].ATO thin films have been used in many fields such as heat shielding coating on low-emissivity window for energy saving [8].Fabrication techniques used to deposit ATO thin film include dip coating based on sol–gel method;sputtering and spray pyrolysis.The sol–gel route has several advantages over the other method.It is a low cost and simple process and makes the precise control of doping concentration easier [9,10].In order to improve the scratching abrasive resistance of ATO thin film prepared by sol–gel route [11,12]a novel sol–gel route has been proposed.In this technological process an organic–inorganic hybrid silica sol was used as the pre-cursor of protecting matrix.The ATO functional componentwas homogeneously distributed in a transparent silica matrix.The mixed structure is of benefit to preventing the crack of thin film in drying and annealing process [13].When a composite material containing two oxides with different pho-to index hopes to keep high transmittance in visible light re-gion the second phase component must be dispersed homogeneously into the amorphous matrix at a level of nanometer.In this work a transparent nanocomposite thin film com-posed of ATO and silica was synthesized by the sol–gel route.The sol–gel method includes (a)the synthesis of ATO sol and hybrid organic–inorganic silica sol;(b)mixing of two nanoparticulate sols.A TEM investigation of phase structure in ATO–silica composite gel is reported.The optical proper-ties and crystallizability of composite thin film is discussed.2.Experimental2.1.Preparation of ATO aqueous solAll the chemical reagents used in the synthesis experi-ment were obtained from commercial sources without0167-577X/$-see front matter D 2005Elsevier B.V .All rights reserved.doi:10.1016/j.matlet.2004.12.033*Tel.:+865515591477;fax:+865515591434.E-mail address:chenxiaochuan126@.Materials Letters 59(2005)1239–1242/locate/matletfurther purification.The aqueous ATO sol were prepared by a co-precipitation process from hydrolysis of SnCl4d5H2O and SbCl3,and followed by the peptization of the precipitate. The reaction was performed at room temperature.In the co-precipitation procedure aqueous NH4OH solution was added directly to the mixture solution of SnCl4d5H2O and SbCl3 until the pH of the mixture reach6–8,where pale yellow ATO hydroxide precipitate were produced.Peptization of ATO hydroxide with the aqueous solution containing oxalic acid gives a yellowish transparent sol.Finally ATO sol was heated and refluxed at608C for4h.2.2.Synthesis of hybrid organic–inorganic silica solThe hybrid organic–inorganic silica-based sols were synthesized as follows:First a mixture solution of tetrae-thoxysilane(TEOS),3-glycidoxypropyltrimethoxysilane (GPTS),isopropyl and alcohol in weight ratio1:1:2.5:3.5 was prepared.Then a suitable amount of deionized water (pH=1,by HCl addition)was added to the mixture solution. The mole ratio of TEOS and H2O is about1:6to1:8.The mixed solution was stirred and heated under reflux at808C for16h.The synthesized transparent hybrid silica sol was used as protecting component of nanocomposite thin film.2.3.Preparation of ATO/SiO2nanocomposite thin filmsA transparent functional gelled film was deposited from the mixture sol comprising the hybrid organic–inorganic silica sol and the ATO sol.Deposition was performed on the glass substrate at room temperature by a simple dip coating process.After being dried at room temperature the nano-composite gelled thin film was thermally densified at a temperature up to4008C in a reducing atmosphere containing N2and vapor of alcohol.2.4.InstrumentationThe Zeta potential measurement of the0.5wt.%ATO aqueous sol was carried out with a ZETASIZER3000HS A measuring system(MALVERN).0.1N HNO3was used to adjust the pH of reference ATO sol that does not contain oxalic acid.The X-ray diffractometer(XRD)was used for the structural characterization of the as-dried and thermally densified ATO–SiO2nanocomposite material.The micro-structure feature of nanocomposite gel film and annealed film were observed with a transmission electron microscope (TEM)(type JEM-2010).The sample for TEM study was prepared as follows:A droplet of mixed sol consisting of ATO colloidal sol and hybrid silica sol was dropped on a copper grid covered with organic film,and after solvents were vaporized a nanocomposite thin film was deposited on the copper grid.The chemical composition of annealed nanocomposite thin film was measured using an energy dispersive X-ray analysis system(EDS)equipped with a scanning electron microscope.Optical transmission was determined using a Varian Cary5E spectrophotometer in the wavelength range of300–2500nm.3.Results and discussion3.1.Surface adsorption studiesWhen oxalic acid was added to the ATO suspension the pH of suspension was adjust to2by the ionization of oxalic acid.Peptization with oxalic acid turns slowly the initial turbid ATO suspension into transparent stable sol.If without addition of oxalic acid ATO nanoparticles in the suspension will show aggregating behavior and begin precipitating at pH b5.The experimental result tells us that colloidal stability of ATO sol comes from addition of oxalic acid.Oxalic acid molecule acts as a surface-modifying agent and prevents aggregation of ATO particles.Fig.1shows the result of Zeta potential measurement at different pH level.The date shows that surface of ATO nanoparticles in aqueous sol is positively charged at pH\5without the addition of oxalic acid.The addition of oxalic acid decreases the Zeta potential of surface and changes the surface to a negative charge in the pH range2–4.According to the dissociation constant of oxalic acid the neutral molecules and negatively charged HO–(CO)2–OÀ1ions are predominant components in aqueous solution at2b pH b3.In initial suspension surface of ATO nanoparticles has a charge especially opposing the oxalic acid ions.The electrostatic force generated by the opposing charges will facilitate the ions transport stage of adsorption reaction.Now we assume that markedinteraction Fig.1.Zeta potential of ATO aqueous sol as a function of pH;0.5wt.% ATO content was used.X.C.Chen/Materials Letters59(2005)1239–1242 1240exist between oxalic acid ions and positive surface hydroxylgroups Q Sn–OH 2+or neutral surface hydroxyl groups Q Sn–OH.The oxalic acid ions can be preferentially adsorbed to the surface of ATO nanoparticles by hydrogen bond or Q Sn–O–C bond.The adsorbed ions neutralize surface positive charges and ultimately reverse the surface to a negative Zeta potential.Fig.1shows that the magnitude of negative Zeta potential is not large enough to stabilize the ATO nanoparticle electrostatically in sol.After oxalic acid was added to the suspension the transparent sol is found to remain stable almost infinitely at pH b 4.The only possible explanation is that effective dispersion mechanism comes from a combination of electrostatic and steric repulsion between oxalic acid ions that were adsorbed on surface of different ATO particles.3.2.XRD and EDS studiesFig.2shows XRD spectra of the ATO–silica nano-composite sample.The pattern (a)relates to the nano-composite gel obtained as dried at room temperature and the pattern (a)shows the presence of a very broad diffraction peak attributable only to cassiterite structure.The XRD patterns of nanocomposite samples show little difference between as-dried and thermally densified samples.Theresult indicates that ATO colloidal particles have developed a nanocrystal structure of cassiterite during sol preparation which contains a hydrothermal process at 608C.TheFig.2.XRD pattern of ATO–SiO 2composite gel:(a)as-dried at room temperature;(b)heat-treated at 5008C in air for 1h.Table 1Elemental concentration of ATO/SiO 2nanocomposite thin film Sample Atomic concentration,%V olume ratio,SiO 2/ATO O Si Sn Sb As-dried69.6917.2510.722.351.5Fig.3.Diffraction pattern and TEM image of ATO–SiO 2nanocomposite thin film as-dried at room temperature:(a)ED pattern;(b)TEMimage.Fig.4.Diffraction pattern and TEM image of ATO–SiO 2composite thin film thermal-treated at 3008C in reducing atmosphere for 2h:(a)ED pattern;(b)TEM image.X.C.Chen /Materials Letters 59(2005)1239–12421241hydrothermal process under atmosphere is also an effective method for promoting the crystallization of ATO nano-particles in the aqueous solution [14,15].The element contents in ATO–SiO 2film are shown in Table 1.Measured Si/Sn+Sb atom ratio of sample is about 1.3:1.The SiO 2/ATO volume ratio in the nanocomposite is calculated from the atom ratio and theory density.3.3.TEM and UV–Vis–Nir spectra studiesThe TEM image of as-dried ATO–SiO 2nanocomposite thin film is shown in Fig.3(b).We can observe that ATO nanoparticles are homogeneously dispersed in SiO 2-based amorphous matrix without any evidence of aggregation.ATO grains are found to have a size range of 3–5nm in diameter.Fig.3(a)shows a typical electron diffraction pattern of ATO nanocrystalline grain.Four electron dif-fraction (ED)rings can be indexed to the pattern of ATO with cassiterite structure.The result is in good agreement with XRD analysis.The structural change induced by thermal treatment of ATO thin film has been investigated.Fig.4shows the ED pattern and TEM image taken from ATO–SiO 2nanocomposite thin film which was annealed at 3008C in reducing atmosphere.The contrast morphology in this image shows some large crystal grains with diameter range from 20nm to 25nm.The ED pattern taken from the same sample contains some sharp spots resulting from thelarge crystallites.The observed results indicate that thermal treatment in reducing atmosphere can accelerate grain growth of ATO nanoparticles.The growth of crystal grain was accompanied by the disappearance of grain boundary and increased electrical conductivity and Nir-light reflec-tance of ATO film [1].The optical transmission spectra of ATO thin film deposited on the glass substrate of 1mm thick are shown in Fig.5.A high transmission of 85%is observed in the visible region.The reduction of transmission in the Nir wavelength arises from improved conductivity of nanocrystalline ATO particles that were heat-treated in the reducing atmosphere.4.ConclusionsThe transparent ATO–SiO 2nanocomposite thin films have been prepared successfully by the sol–gel method.The transmission of thin film is rather high in the visible region,range between 85%and 90%as well as the transmission in Nir region has been decreased to 41%.The thermal treatment in reducing atmosphere is an effective method for promoting crystalline grain growth of ATO nanoparticles.The oxalic acid is an excellent dispers-ing agent for ATO nanoparticle in the aqueous solution in pH range 2–4.References[1]G.Frank,E.Kauer,H.Kostlin,Thin Solid Films 77(1981)107.[2]M.S.Castro,C.M.Aldao,J.Eur.Ceram.Soc.20(2000)303.[3]O.Safonova,I.Bezverkhy,P.Fabrichnyi,M.Rumyantseva, A.Gaskov,J.Mater.Chem.7(1997)997.[4]S.Shanthi,C.Subramanian,P.Ramasamy,Cryst.Res.Technol.34(1998)1037.[5]A.E.Rakhshani,Y .Makdisi,H.A.Ramazaniyan,J.Appl.Phys.83(2)(1998)1049.[6]C.Goebbert,R.Nonninger,M.A.Aegerter,H.Schmidt,Thin SolidFilms 351(1999)79.[7]C.Terrier,J.P.Chatelon,J.A.Roger,Thin Solid Films 295(1997)95.[8]H.Ohsaki,Y .Kokubu,Thin Solid Films 351(1999)1.[9]M.A.Aegerter,N.Al-Dahoudi,J.Sol–Gel Sci.Technol.27(2003)81.[10]A.N.Banerjee,S.Kundoo,P.Saha,K.K.Chattopadhyay,J.Sol–GelSci.Technol.28(2003)105.[11]S.W.Kim,Y .W.Shin,D.S.Bae,J.H.Lee,J.Kim,H.W.Lee,ThinSolid Films 437(2003)242.[12]K.Abe,Y .Sanada,T.Morimoto,J.Sol–Gel Sci.Technol.26(2003)709.[13]J.Gallardo,A.Duran,I.Garcia,J.P.Celis,M.A.Arenas,A.Conde,J.Sol–Gel Sci.Technol.27(2003)175.[14]D.Y .Zhang,D.Z.Wang,G.M.Wang,Y .H.Wu,Z.Wang,Mater.Sci.Eng.,B,Solid-State Mater.Adv.Technol.8(1991)189.[15]S.J.Kim,S.D.Park,Y .H.Jeong,S.Park,J.Am.Ceram.Soc.82(1999)927.Fig.5.UV–Vis–Nir transmission spectra:(a)550nm thick ATO–SiO 2thin film which was coated on glass substrate;(b)glass substrate.X.C.Chen /Materials Letters 59(2005)1239–12421242。

硼酸酯合成

Synthesis and Characterization of Monodisperse OligofluorenesJungho Jo,+[b]Chunyan Chi,+[a]Sigurd Hˆger,[c]Gerhard Wegner,*[a]and Do Y.Yoon*[b]Introduction9,9-Disubstituted polyfluorenes find extensive scientific and technological application as efficient organic blue-light-emit-ting diode materials.[1,2]Polyfluorenes showextremely high photoluminescence quantum yields,high thermal and oxida-tive stability,and good solubility in common organic sol-vents for easy processing by spin-or dip-coating methods.[3]They also exhibit interesting thermotropic liquid-crystal characteristics,[4]and consequently,upon annealing in the nematic melts,the polymer chains were shown to be easily aligned on a rubbed polyimide surface.[5]Such an alignment of the polymer results in the polarization of the emitted light and improves the charge carrier mobility,a prerequisite for the fabrication of an organic thin-film transistor.[6]Thus,the ability of the polyfluorenes to align excellently paves the way to make thin films with highly anisotropic electrooptical and electrical properties.[7]Polyfluorenes are readily prepared by Ni 0-mediated cou-pling of the corresponding dibromo monomers.Polymers obtained by this method have weight-averaged molecular weights (M w )of the order of several hundred thousand with polydispersities of around three (according to GPC analysis against polystyrene standards).The long chain lengths and the polydispersity in chain lengths lead to complex structur-al characteristics of the thin films and make it very difficult to establish a proper structure±property relationship.More-over,the normal synthetic procedure leads to incorporation of a small amount of chemical defects,which may be re-sponsible for undesirable green-band emission characteris-tics.[8]Therefore,for better understanding of the structure±prop-erty relationships of polyfluorenes,it would be very helpful to study the properties of a series of pure oligomers with well-defined length and no chemical defects.The absorption spectra of a series of oligomers will allow the estimation of the effective conjugation length of the polymer.[9]In addi-tion,a detailed study of the photoluminescence spectra of pure oligomers may help to solve questions concerning the origin of the green-emission band observed in the photolu-minescence and electroluminescence spectra of polyfluorene films.[10]Moreover,well-defined,defect-free oligofluorenes may also be welcome as active materials in organic light-emitting diodes and organic thin-film transistors.Monodispersed dialkyl fluorene oligomers were first re-ported by Klaerner and Miller.[11]They showed that the Ni 0-mediated oligomerization of 2,7-dibromo-9,9-bis(n -hexyl)-fluorene in the presence of 2-bromofluorene as an end-cap-ping agent gives a mixture of oligomers and low-molecular-weight polymers that could be fractionated by HPLC.From the spectroscopic properties of the samples,the effective[a]C.Chi,+Prof.Dr.G.WegnerMax Planck Institute for Polymer Research Ackermannweg 10,55128Mainz (Germany)Fax:(+49)6131-379-100E-mail:wegner@mpip-mainz.mpg.de [b]J.Jo,+Prof.Dr.D.Y.YoonSchool of Chemistry,Seoul National University San 56±1,Sillim-dong,Seoul,151±747(Korea)Fax:(+82)2-877-6814E-mail:dyyoon@snu.ac.kr [c]Prof.Dr.S.HˆgerPolymer-Institut,Universit‰t KarlsruheHertzstrasse 16,76187Karlsruhe (Germany)[+]These authors contributed equally to this work as part of their Ph.D.theses.Abstract:An efficient synthesis of 9,9-bis(2-ethylhexyl)fluorene oligomers up to the heptamer is reported,with repet-itive Suzuki and Yamamoto coupling reactions employed in the synthesis.The key steps for preparation of the es-sential intermediates include Pd-cata-lyzed transformation of aryl bromides to aryl boronic esters (Miyaura reac-tion)and the application of the much higher reactivity of aryl boronic esters over aryl bromides in the Pd-catalyzed cross-coupling reaction with aryl diazo-nium salts.Variation of the UV/Vis ab-sorption and photoluminescence char-acteristics with chain length is report-ed.Moreover,glass transition and liquid-crystal characteristics of the oligomers are described and compared with those of the polymer.Keywords:fluorene ¥glasses ¥liq-uid crystals ¥oligomerization ¥pho-toluminescenceFULL PAPERconjugation length was estimated to be approximately 12fluorene units.Lee and Tsutsui prepared a series of oli-gofluorenes up to the tetramer by a repetitive2n divergent approach from2,7-dibromo-9,9-bis(n-hexyl)fluorene,with coupling with bis(n-hexyl)fluorene-2-borate and subsequent bromination of the coupling product.[12]Anemian et al.syn-thesized monodisperse dihexylfluorene oligomers up to the hexamer by a combination of Suzuki and Yamamoto cou-pling reactions.[13]Oligomers with n repeating units contain-ing only one bromine atom at positions2or7on the end fluorenes were prepared by coupling the corresponding monoboronate(nÀ1)with2-bromo-7-iodo-9,9-bis(n-hexyl)-fluorene at the iodo site,which is significantly more reactive than the bromo site.The resulting monobromo oligomers were then coupled by a Yamamoto reaction.Most recently, a detailed description of the synthesis,optical properties, and solid-state properties of defined oligofluorenes,up to the hexadecamer,containing chiral substituents at position9 was presented by Geng et al.[14]Here again,the iodo/bromo selectivity in the Suzuki coupling reaction and the use of tri-methylsilyl groups as dormant iodides were used as key fac-tors in the oligomer synthesis.The enormous success of the Suzuki reaction[15]in the preparation of these oligomers arises from the high yield of the coupling reaction together with the easy availability of the boronic acids and the boronates.[16]They are prepared in good to excellent yields by halogen±metal exchange and subsequent trapping of the aryl lithium compound with trial-kylborates.Recently,the scope of this reaction has been dra-matically expanded by the discovery that aryl boronates are also available directly from the aryl halides by a Pd0-cata-lyzed reaction with the pinacol ester of diboron(the Miyaura reaction).[17]This transformation avoids the use of strongly basic organometallic reagents and thus allows the preparation of a wide variety of functionalized aryl boronic esters.Here,we present the synthesis of oligofluorenes from the dimer up to the heptamer by Suzuki and Yamamoto reac-tions,[18]with the Miyaura reaction employed for the first time for the preparation of the aryl boronates.Also,we have taken advantage of a large difference in the reactivity between aryl diazonium salts and aryl bromides in the Suzuki coupling reaction[19]in the preparation of the key in-termediates.The oligomers have been characterized with re-gards to their optical(absorption and photoluminescence) properties and their phase behavior,including glass transi-tion and liquid-crystal characteristics.Finally,the properties of the oligomers are compared with those of the polymer in order to gain newinsights into the polymer properties.Results and DiscussionSynthesis of oligofluorenes:The synthetic route towards the oligofluorenes is shown in Scheme1.First,2,7-dibromofluor-ene and2-bromofluorene were alkylated with2-ethylhexyl bromide to give the di-and monobromides of fluorene,1 and3,respectively.Both of these compounds,as well as the corresponding boronic acids,have already been reported in the literature.[11±14]However,in our synthesis,we trans-formed the aryl bromides into the corresponding aryl boron-ic esters with the Miyaura reaction.In these reactions the corresponding boronic esters,2and4,are formed in high yields(>90%)and can easily be purified by column pounds4and2were then coupled with3 to give the fluorenyl dimer5and trimer6,respectively. Scheme1.Synthesis of the oligofluorenes:a)2-Ethylhexyl bromide,50% aqueous NaOH/DMSO,room temperature;b)bis(pinacolato)diboron, AcOK/DMF,[Pd(dppf)Cl2],608C;c)[Pd(PPh3)4],toluene/aqueous Na2CO3,reflux;d)BF3¥OEt2,butylnitrite/dichloromethane,À108C;e)Pd(OAc)2/EtOH,reflux;f)Br2,dichloromethane,reflux;g)[Ni(cod)2], COD,Bipy,toluene/DMF,808C.DMSO=dimethylsulfoxide,DMF= N,N-dimethylformamide,dppf=1,1’-bis(diphenylphosphanyl)ferrocene, COD=cycloocta-1,5-diene,Bipy=2,2’-bipyridine.FULL PAPER G.Wegner,D.Y.Yoon et al.To synthesize the longer fluorene oligomers,the unsym-metrical monobrominated intermediates,such as9and11, are essential.However,these intermediates cannot be ob-tained directly by bromination of5or6with bromine,since statistical product mixtures are obtained which are very dif-ficult to separate on a large scale.One possibility to obtain the monobrominated intermediates is to use compounds with one potential reaction site in a protected form(for ex-ample,trimethylsilyl groups instead of bromo or iodo func-tionalities[20])as described by Geng et al.[14]Another way is to use fluorene derivatives with two reaction sites of signifi-cantly different reactivity.In the latter case,the use of bro-moiodofluorene derivatives is quite obvious since the reac-tivity of aryl iodides towards the Suzuki coupling is substan-tially higher than the reactivity of aryl bromides;this con-cept has already been used by Anemian et al.[13]A good alternative approach is to use the large reactivity difference between aryl diazonium salts and aryl bromides in the cross-coupling reaction with aryl boronates.Since the reaction with aryl diazonium salts does not need a base such as Na2CO3,which is essential in the Suzuki coupling reac-tion with aryl bromides,the coupling reaction takes place only at the site of the diazonium salt.Hence,we employed this reaction in our synthetic procedure as follows.2-Amino-7-bromofluorene was alkylated with2-ethylhex-yl bromide to give7in82%yield;7was subsequently trans-formed into the corresponding diazonium salt8(81%). Cross-coupling reaction of4and8with Pd(OAc)2gave9in 70%yield within an hour.This result shows that the reactiv-ity difference between aryl diazonium salts and aryl halides is larger than that between aryl iodides and aryl bromides.9 was transformed into the corresponding boronic ester10in 56%yield with the Miyaura reaction.Subsequently,the cross-coupling reaction of10and8gave11in48%yield. Another method we have used to obtain the monobro-mides is to treat the monoboronate with an excess of the di-bromofluorene.Indeed,the coupling of4with an excess of 1was successfully performed by using only1.5equivalents of1to give the monobrominated dimer9in50%yield(not shown in Scheme1).Similarly,the monobrominated trimer 11was obtained in45%yield by the reaction of4with1.5-fold excess of the dibrominated product12,which was pre-pared from5in90%yield.[21]Both methods led to identical compounds,thereby demonstrating the validity of our syn-thetic methodology.Yamamoto homocoupling re-actions of9and11gave the flu-orenyl tetramer13and hexam-er15,respectively,both in%50%yield.The fluorenylpentamer14was obtained witha cross-coupling reaction of9and2in47%yield.The highreactivity of the diazonium saltswas also used to prepare the di-bromofluorenyl trimer16,which was obtained in54%yield by coupling of2and8.Although16can,in principle,also be prepared by the bromination of6,a detailed mass spectral analysis of the crude reaction products showed that varying amounts of tribromide contaminate the dibromide. Since even small amounts of an impurity affect the liquid-crystalline behavior of the oligomers,we avoided the bromi-nation of the fluorenyl trimer and higher oligomers in our oligomer synthesis.The fluorenyl heptamer17was obtained in38%yield by cross-coupling reaction of10and16. Optical properties of oligofluorenes:Electronic absorption spectra of monodisperse oligo(9,9-bis(2-ethylhexyl)fluorene-2,7-diyl)compounds5,6,13,14,15,and17in diluted chloroform solution with the same fluorene unit concentra-tion(1.0î10À5m)are shown in Figure1and the data are col-lected in Table1.The oligofluorenes exhibit unstructured absorption bands, as is also seen for polyfluorenes.[3]The absorption maximum is red-shifted with increasing number(n)of fluorene units. The molar extinction coefficients(e)of the oligofluorenes showa good approximation of a linear increase w ith n from dimer to heptamer,as seen in Table1.The increment is 30.3î103L molÀ1cmÀ1for each repeat unit.The plot of the wave number of the maximum absorption versus1/nfollows Figure1.UV/Vis absorption of oligofluorenes(dimer to heptamer)in chloroform solution at room temperature at a fixed concentration of flu-orene repeat units of1.0î10À5mole LÀ1.Table1.Summary of UV/Vis absorption(n max(abs))and photoluminescence(n max(PL))spectra for the fluoreneoligomers and polymer,from chloroform solutions and solid films.[a]Sample Solution Filmn max(abs)e max n max(PL)n max(abs)n max(PL)[cmÀ1][L molÀ1cmÀ1][cmÀ1][cmÀ1][cmÀ1]dimer530580491702740025970304002710025770trimer628740813302538024100286502513023870tetramer13279301115002475023470275502439023200pentamer14274001417002445023150270302398022940hexamer15271701730002433023040268802381022780heptamer17268802003002427023040268102370022730polymer26110±2410022940259102359022570[a]Since the resolution of the low-energy peak was too low at the temperature at which the data were record-ed,only the n max values of the two high-energy components are given.Synthesis and Characterization of Monodisperse Oligofluorenes2681±2688a linear fit,as shown in Figure 2.The polymer has a maxi-mum absorption at 26110cm À1(383nm);[3]hence,we can estimate an effective conjugation length of 14repeat unitsfrom the plot in Figure 2,a figure that can be compared with the reported value of 12for poly(9,9-bis(n -hexyl)fluor-ene-2,7-diyl).[11]The UV/Vis absorption spectra of thin films of the oligofluorenes on quartz substrates are practically identical to the solution data except for slight red-shifts in the absorption maxima,as listed in Table 1.Figure 3a shows the photoluminescence (PL)spectra of the oligomers from dimer 5to heptamer 17in chloroform with the same concentration of fluorene units (1.0î10À6m ),excited at the corresponding energy of maximum absorp-tion.Similar to polyfluorenes,three well-resolved fluores-cence bands are observed.They may be assigned to the 0±0,0±1,and 0±2intrachain singlet transitions.[22]The spectral position and the intensity of the PL maximum changes with the number of fluorene units,n .This is explained by the in-crease of effective conjugation from dimer 5up to heptamer 17.Notably,the relative intensity of the three emission bands also changes with n .The relative intensity of the 0±0transition increases with n ,while that of the 0±2transition decreases.This may be related to an increase of the intra-chain coupling interaction with the molecule×s length.Normalized solid-state PL spectra of oligofluorenes 5,6,13,14,15,and 17from thin films on a quartz plate excited at the absorption maxima are shown in Figure 3b and the key data are listed in Table 1.Relative to the PL spectra measured in solution,red shifts in the emission maxima are observed and the relative intensities of the 0±2intrachain singlet transition increase in all cases.Most importantly,the green-band emission usually seen for the polymer [3]is absent for all of the oligomers (Figure 3b).Even upon high-temperature annealing (1808C)in air,this green emission is still negligible for the oligomers.This result casts doubt on the widely discussed hypothesis that the green emission seen with varable intensity in polymer samples (Figure 3b)origi-nates from excimer formation by interchain interaction.It is difficult to see why such interchain interactions should be suppressed in the case of oligomers if this explanation was true.Phase transition characteristics of oligofluorenes :The DSC traces shown in Figure 4clearly exhibit the glass transition temperatures for all of the oligomers in the low-temperature range,followed by an endothermic transition for the tetram-er 13,pentamer 14,hexamer 15,and heptamer 17as the temperature is increased.The latter transition is identified as the liquid-crystalline to isotropic transition from the po-larized optical microscopy study.The Schlieren texture and the very small enthalpy value of the transition,as shown in Table 2,indicate that the liquid-crystal structure is probably of nematic character,but a further study on this topic is in progress.The isotropization temperature T iso of this liquid-crystal-line to isotropic transition extrapolates to a hypothetical T iso (Polymer)for n !¥of 4758C if plotted in the coordi-nates T iso =T iso (n !¥)(1ÀKX E )where X E is the molefrac-Figure 2.Plot of n ˜max versus reciprocal degree of polymerization n.Figure 3.a)Fluorescence spectra of oligofluorenes (dimer to heptamer)in chloroform solution at room temperature at a fixed concentration of fluorene repeat units of 1î10À6mole L À1.b)Photoluminescence spectra of thin films of the oligofluorenes (dimer to heptamer).The spectrum for the polymer,also shown in this figure,was obtained for a sample an-nealed at 1808C for 1h in air.FULL PAPERG.Wegner,D.Y.Yoon et al.tion of end groups and K is an empirical constant.This tem-perature is well above the decomposition range of the high polymer.In this regard,it is important to note that the poly-mer exhibits a well-known ™melting∫transition around 1608C.Above 1608C the polymer exists in a nematic liquid-crystal phase;belowthat temperature another solid phase is formed,the true nature of which is not yet understood.It may be of higher order smectic type but of such a rigidity of the packing that a transition to a glassy state is suppressed.Whether this substantial difference in the phase structure and nature of transitions has consequences for the electro-optical properties of these materials needs to be studied fur-ther.The glass transition temperatures,listed in Table 2,tend to level off as the chain length increases and exhibit n À1de-pendence of the type:T g =64.0À174.7n À1.Therefore,the extrapolated T g for the polymer is estimat-ed to be approximately 648C.The occurrence of this glass transition is difficult,if not impossible,to see in the DSC thermogram for the polymer (see Figure 4).This may be due to the above-mentioned differences of the liquid-crystal phases in the polymer and in the oligomers.ConclusionOligofluorenes up to the heptamer can be synthesized on the hundred-milligram scale by a stepwise route involving Suzuki and Yamamoto coupling reactions.The synthesis of the boronates for the Suzuki coupling is based on the Pd-catalyzed transformation of aryl bromides into boronates,a process that avoids strongly basic aryl lithium intermediates.Therefore,this methodology has potential for the synthesis of oligofluorenes containing a variety of functional groups.The synthesis of mono-or dibrominated fluorenyl oligomers,which are essential for expanding of the chain length,is based on the much higher reactivity of aryl boronates over aryl bromides in the Pd-catalyzed cross-coupling reaction with aryl diazonium salts.The pure oligomers as solid films do not showthe unde-sired green-band emission characteristics of the polymer.Moreover,they are found to align more readily to form monodomains on various surfaces,as will be published else-where.The oligomers from tetramer to heptamer show a liquid-crystal phase with clearly defined isotropization tem-peratures;this allows extrapolation to the expected isotropi-zation temperature of the polymer at around 4758C,well above the thermal decomposition temperature.Most impor-tantly,the oligofluorenes do not showthe same high-order phase that the polymer exhibits belowthe melting tempera-ture of approximately 1608C.However,unlike the polymer,the oligomers do showa glass transition temperature w hichexhibits n À1dependence and allows extrapolation to a hypo-thetical glass transition of the polymer at around 648C.As this glass transition refers to a freezing of a liquid-crystal phase not seen for the polymer,it is not too surprising that this phenomenon cannot be detected for the polymer.Experimental SectionGeneral remarks :Reactions requiring an inert gas atmosphere were con-ducted under argon and the glassware was oven-dried (1408C).Tetrahy-drofuran (THF)was distilled from potassium prior to mercially available chemicals were used as received.1H NMR and 13C NMR spec-tra were recorded on Bruker DPX 250or AC 300spectrometers (250and 300MHz for 1H,62.5and 75.48MHz for 13C).Chemical shifts are given in ppm,referenced to residual proton resonances of the solvents.Thin-layer chromatography was performed on aluminium plates precoated with Merck 5735silica gel 60F 254.Column chromatography was per-formed with Merck silica gel 60(230Æ400mesh).Field desorption spec-tra were recorded on a VG ZAB 2-SE FPD machine.Differential scan-ning calorimetry was measured on a Mettler DSC 30with a heating or cooling rate of 10K min À1.Polarization microscopy was performed on a Zeiss Axiophot apparatus with a nitrogen-flushed Linkam THM 600hot stage.UV/Vis spectra were recorded at room temperature with a Perkin±Elmer Lambda 9UV/Vis/NIR spectrophotometer.Photoluminescence spectra were obtained on a Spex Fluorolog II (212)apparatus.Optical properties of solid thin films were normally obtained for samples spin-coated on a quartz substrate from dilute chloroform solutions and dried under vacuum.Elemental analysis were performed by the University of Mainz.Melting points were measured with a Reichert hot-stage appara-tus and are uncorrected.2,7-Dibromo-9,9-bis(2-ethylhexyl)fluorene (1):2-Ethylhexylbromide (38.73g,185.18mmol,35.74mL)was added to a mixture of 2,7-dibromo-fluorene (25.0g,77.16mmol)and triethylbenzylammonium chloride (0.878g, 3.86mmol,5mol %)in DMSO (125mL)and 50%aqueousFigure 4.DSC traces for the oligofluorenes (dimer to heptamer;second heating at 108C min À1).The DSC trace for the polymer is also shown for comparison.Table 2.Summary of glass transition temperature (T g ),isotropization temperature (T iso ),and the enthalpy of isoptropization value (D H iso )for the oligofluorenes.Sample T g [K]T iso [K]D H iso [J g À1]dimer 5252±±trimer 6274±±tetramer 132953370.50pentamer 143013990.47hexamer 153074630.71heptamer 173155190.74Synthesis and Characterization of Monodisperse Oligofluorenes 2681±2688NaOH(31mL).The reaction mixture was stirred at room temperature for5h.An excess of diethyl ether was added,the organic layer was washed with water,diluted HCl,and brine,then dried over MgSO4.The solvent was removed under vacuum and the residue was purified by column chromatography over silica gel with n-hexane as the eluent(R f= 0.78)and solidified from EtOH atÀ308C to give1as a white solid (36.21g,85.6%):M.p.45±548C;1H NMR(250MHz,CD2Cl2):d=7.57±7.43(m,6H),1.94(d,J=5.35Hz,4H),0.89±0.68(m,22H),0.55±0.41(m, 8H)ppm;13C NMR(62.5MHz,CDCl3):d=152.3,139.1,130.1,127.4, 121.0,55.3,44.3,34.6,33.6,28.0,27.1,22.7,14.0,10.3ppm;MS(FD): m/z:548.2[M+].2-Bromo-9,9-bis(2-ethylhexyl)fluorene(3):Compound3was prepared ac-cording to the method used for1by using2-ethylhexylbromide(43.3g, 224.5mmol,39.9mL),2-bromofluorene(25.0g,102.0mmol),triethylben-zylammonium chloride(1.16g,5.10mmol,5mol%),DMSO(165mL), and50%aqueous NaOH(41mL).Purification by column chromatogra-phy over silica gel with n-hexane as the eluent(R f=0.72)gave3as a col-orless liquid(43.14g,90.1%):1H NMR(250MHz,CD2Cl2):d=7.70±7.26 (m,7H),1.97(m,4H),0.90±0.43(m,30H)ppm;13C NMR(62.5MHz, CDCl3):d=152.8,150.0,140.3,129.8,127.3,126.9,124.0,120.9,120.4, 119.6,55.1,44.4,34.6,33.6,28.0,27.0,22.7,14.0,10.4ppm;MS(FD): m/z:470.2[M+].2,7-Bis(4,4,5,5-tetramethyl[1.3.2]dioxaborolan-2-yl)-9,9-bis(2-ethylhexyl)-fluorene(2):Under an argon atmosphere,1(2.43g,4.43mmol),bis(pina-colato)diboron(4.05g,15.94mmol),KOAc(2.60g,26.57mmol),and Pd(dppf)Cl2(0.226g,0.266mmol)were dissolved in DMF(40mL)and heated to608C overnight.After the reaction mixture was cooled to room temperature,water and diethyl ether were added.The aqueous phase was extracted with diethyl ether and the combined organic layers were dried over MgSO4.The solvent was removed under vacuum and the resi-due was purified by column chromatography over silica gel with petrole-um ether/dichloromethane(3:1)as the eluent(R f=0.34)and solidified from EtOH atÀ308C to give2as a white solid(2.60g,91.5%):M.p.85.5±87.68C;1H NMR(250MHz,CD2Cl2):d=7.84±7.69(m,6H),2.00 (d,J=5.3Hz,4H), 1.36(s,24H),0.86±0.50(m,22H),0.48±0.45(m, 8H)ppm;13C NMR(62.5MHz,CDCl3):d=150.1,143.9,133.5,130.4, 119.2,83.5,54.7,44.0,34.6,33.5,27.8,27.2,24.8,22.7,14.1,10.3ppm;MS (FD):m/z:643.0[M+].2-(4,4,5,5-Tetramethyl[1.3.2]dioxaborolan-2-yl)-9,9-bis(2-ethylhexyl)fluor-ene(4):Compound4was prepared according to the method used for2 by using3(14.07g,30.0mmol),bis(pinacolato)diboron(12.19g, 48.0mmol),KOAc(8.82g,90.0mmol),and[Pd(dppf)Cl2](1.23g, 1.5mmol)in DMF(300mL).Column chromatography over silica gel with petroleum ether/dichloromethane(4:1)as the eluent(R f=0.59)af-forded4as an oily product(14.78g,95.5%):1H NMR(250MHz, CD2Cl2):d=7.82±7.64(m,4H),7.36±7.21(m,3H),2.0±1.86(m,4H), 1.34(s,24H),0.86±0.65(m,22H),0.50±0.43(m,8H)ppm;13C NMR (62.5MHz,CDCl3):d=151.0,149.5,144.2,141.1,133.6,130.3,126.6, 124.1,120.0,118.8,83.5,54.8,44.5,44.1,34.6,33.5,28.2,27.8,27.3,26.8, 24.8,22.7,14.1,10.5,10.1ppm;MS(FD):m/z:516.7[M+].9,9,9’,9’-Tetrakis(2-ethylhexyl)-2,2’-bifluorene(5):A mixture of4(5.17g, 10.0mmol)and3(4.69g,10.0mmol)in toluene(50mL)and2m aqueous Na2CO3solution(25mL,50mmol)was degassed by pump and freeze cycles(3î)and[Pd(PPh3)4](0.577g,0.5mmol)was added under argon. The solution was heated to reflux with vigorous stirring for20h.After the reaction mixture was cooled to room temperature,diethyl ether and water were added.The organic layer was separated and washed with di-luted HCl and brine,then dried over MgSO4.The solvent was removed under vacuum and the residue was purified by column chromatograpy over silica gel with petroleum ether as the eluent(R f=0.47)to give5 (7.08g,90.8%):1H NMR(250MHz,CD2Cl2):d=7.73±7.80(m,4H), 7.57±7.64(m,4H),7.25±7.44(m,6H),2.04±2.14(m,8H),0.49±0.88(m, 60H)ppm;13C NMR(62.5MHz,CDCl3):d=150.9,150.6,141.1,140.4, 126.8,126.3,126.0,124.1,122.9,119.6,54.9,44.5,34.6,33.8,28.2,26.9, 22.7,14.0,10.3ppm;MS(FD):m/z:779.4[M+];elemental analysis: calcd for C58H82(779.2):C89.39,H10.61;found:C89.29,H10.79.9,9,9’,9’,9’’,9’’-Hexakis(2-ethylhexyl)-2,2’-7’,2’’-terfluorene(6):Compound 6was prepared according to the method used for5by using2(2.0g, 3.12mmol),3(4.40g,9.36mmol),and[Pd(PPh3)4](0.36g,0.31mmol)in toluene(30mL)and2m Na2CO3aqueous solution(15.6mL,31.2mmol)for27h.After cooling to room temperature,the mixture was diluted with ethyl acetate and the organic layer was washed with diluted HCl and brine,then dried over MgSO4.The solvent was removed under vacuum and the residue was purified by column chromatography over silica gel with petroleum ether as the eluent(R f=0.22)to give6as a col-orless viscous gum(2.32g,63.8%):1H NMR(250MHz,CD2Cl2):d= 7.83±7.73(m,6H),7.61±7.66(m,8H),7.44±7.25(m,6H),2.13±2.05(m, 12H),0.90±0.49(m,90H)ppm;13C NMR(62.5MHz,CDCl3):d=151.2, 150.9,150.6,141.1,140.4,140.1,126.8,126.3,126.0,124.1,122.9,119.7, 119.6,54.9,44.6,34.6,33.8,28.2,27.1,22.8,14.0,10.3ppm;MS(FD):m/ z:1168.2[M+];elemental analysis:calcd for C87H122(1167.9):C89.47,H 10.53;found:C89.26,H10.42.2-Amino-7-bromo-9,9-bis(2-ethylhexyl)fluorene(7):Compound7was prepared according to the method used for1by using2-ethylhexylbro-mide(7.78g,40.3mmol,7.2mL),2-amino-7-bromofluorene(5.0g, 19.2mmol),triethylbenzylammonium chloride(220mg,1mmol,5 mol%),DMSO(50mL),and50%aqueous NaOH(3.8mL).The reac-tion mixture was stirred for2h.Purification by column chromatography over silica gel with n-hexane/dichloromethane(6.5:3.5)as the eluent (R f=0.47,0.44,and0.38;the title product separated into three spots,due to the diaseteroisomers)gave7as a slightly yellowoily product(7.65g, 82%):1H NMR(300MHz,CD2Cl2):d=7.46±7.37(m,4H),6.70±6.63(m, 2H),3.81(br s,2H),1.84±1.90(m,4H),0.92±0.73(m,22H),0.57±0.52 (m,8H)ppm;13C NMR(75MHz,CDCl3):d=152.5±152.4(three peaks, 2îC),146.9±146.8(three peaks),141.4,131.5±131.4(three peaks),129.8, 127.4±127.3(three peaks),120.9,119.9,118.7±118.5(three peaks),114.2, 110.9±110.8(three peaks),55.2,44.9±44.8(four peaks),35.0,33.9±33.7 (four peaks),28.5±28.3(four peaks),23.2,14.3,10.6±10.4(four peaks)ppm;MS(FD):m/z:484.0[M+].2-Bromo-9,9-bis(2-ethylhexyl)fluorenyl-7-diazonium tetrafluoroborate (8):A solution of7(3.48g,7.18mmol)in CH2Cl2(10mL)was slowly added to BF3¥OEt2(11.46mmol,1.42mL)with stirring under an argon athmosphere atÀ108C.After10min,a solution of butyl nitrite(1.18mL, 10.01mmol)in CH2Cl2(4mL)was slowly added and the mixture stirred for additional30min at08C.n-Pentane(200mL)was added and the mix-ture was stored atÀ208C overnight.The precipitate was filtered off, washed with cold diethyl ether and dried in air to give8as a pale yellow solid(3.39g,81%):1H NMR(300MHz,[D6]acetone):d=9.08(m,1H), 8.87(m,1H),8.53(m,1H),8.16(m,1H),8.06(s,1H),7.77(m,1H), 2.30±2.20(m,4H),0.88±0.45(m,1H)ppm;13C NMR(75MHz,acetone-d6):d=156.6,154.2±153.9(three peaks),153.8,137.9±137.8(three peaks), 134.6,132.6±132.5(three peaks),129.5±129.4(three peaks),129.0±128.8 (three peaks),126.7,125.8,123.7±123.6(three peaks),111.9±111.6(three peaks),57.6±57.5(three peaks),44.5±44.3(four peaks),35.9±35.8(two peaks),34.7±33.9(three peaks),28.9±28.5(three peaks),28.0,23.4±23.3 (two peaks),14.3±14.2(two peaks),10.7±10.3(three peaks)ppm;decom-position temperature:988C.7-Bromo-9,9,9’,9’-tetrakis(2-ethylhexyl)-2,2’-bifluorene(9):A mixture of 4(0.90g, 1.74mmol),8(1.12g, 1.92mmol),and Pd(OAc)2(40mg, 0.178mmol)in ethanol(30mL)was heated to608C for1h(no addition-al base was added).After cooling to room temperature,the mixture was diluted with diethyl ether and the organic layer was washed with brine and dried over MgSO4.The solvent was removed under vacuum and the residue was purified by column chromatography over silica gel with pe-troleum ether as the eluent(R f=0.49)to give9as an oily product(1.04g,70%):1H NMR(250MHz,CD2Cl2):d=7.80±7.26(m,13H),2.14±2.04(m,8H),0.88±0.52(m,60H)ppm;13C NMR(62.5MHz, CDCl3):d=153.0,151.0,150.6,141.0,140.5,140.1,139.2,129.9,127.4, 126.8,126.4,126.0,124.1,122.9,120.9,120.3,119.6,54.9,44.5,34.6,33.8, 28.2,27.1,22.7,14.0,10.3ppm;MS(FD):m/z:857.6[M+].2-[9,9,9’,9’-Tetrakis(2-ethylhexyl)-7,2’-bifluoren-2-yl]-4,4,5,5-tetrame-thyl[1.3.2]dioxaborolan(10):Compound10was prepared according to the method used for2by using9(970mg,1.1mmol),bis(pinacolato)di-boron(450mg,1.8mmol),KOAc(326mg,3.3mmol),and[Pd(dppf)Cl2] (45mg,0.055mmol)in DMF(10mL).Column chromatography over silica gel with n-hexane/CH2Cl2(9:1)as the eluent(R f=0.12)gave10as an oily product(570mg,55.7%):1H NMR(300MHz,CD2Cl2):d=7.86±7.73(m,6H),7.65±7.60(m,4H),7.41(m,1H),7.36±7.27(m,2H),2.09±2.04(m,8H),1.35(s,12H),0.88±0.49(m,90H)ppm;13C NMR(75MHz, CD2Cl2):d=152.8,151.6,151.3,150.5±150.3,144.6,141.7,141.1±140.6, 134.1,131.1±130.9,127.4,127.0,126.6±126.5,124.8,123.6±123.4,120.8,FULL PAPER G.Wegner,D.Y.Yoon et al.。

Synthesis and Characterization of Er3+∶Y3Al5O12 Nanocrystalline Powders Prepared by Sol-Gel Met

［ 8］ ’(.&* H,)(#’ （ 7),H&, $%)# 2 !N ） -)# @& /@$)(#&* R 2 3 U# $%(’ ?)?&,，>& ?,&’&#$ $%& 1, 4 52 *)N)H& $%,&’%/7*（ _
-N
） )#* %(H% &N(’’(/# -,/’’A’&-$(/#’R
! D( E%)#0)（李战发）， 5F)# GF/,/#H（袁多荣）， GF)# I(F7)#（段秀兰），!%( IF.%/#H（石绪忠）， !/#H J()#K)#（宋建安）， L)#H D(%F)（王丽华）
（ !"#"$ %$& ’#()*#")*& )+ ,*&-"#. /#"$*0#.-，!1#23)24 5206$*-0"& ，702#2 89:;::，,102#）
!"#$%&’ "( $&$) )&$*+,
-./0 12 ，,3450 67784，9:;0 1<<=，30 >1?
@ @ @ @ @
!"#$%&’(’ )#* +%),)-$&,(.)$(/# /0 1,2 3 4 =,&?),&* @" !/7AB&7 C&$%/*
!
52 678 9:; <)#/-,"’$)77(#& =/>*&,’
!"#$%&’$ ：<)#/A’(.&* 1,

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

This article was downloaded by: [University of Ottawa]On: 09 April 2014, At: 19:25Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UKMolecular Crystals and Liquid CrystalsPublication details, including instructions for authors andsubscription information:/loi/gmcl20Synthesis and Characterization ofCarbazole-based Copolymers ContainingBenzothiadiazole Derivative for PolymerLight-Emitting DiodesJin Su Park a , Sung-Ho Jin a , Yeong-Soon Gal b , Jun Hee Lee c & JaeWook Lee da Department of Chemistry Education, Interdisciplinary Program ofAdvanced Information and Display Materials , Institute for PlasticInformation and Energy Materials , Busan , 609-735 , Koreab Polymer Chemistry Lab , Kyungil University , Hayang , 712-701 ,Koreac Department of Advanced Materials Engineering , Dong-AUniversity , Busan , 604-714 , Koread Department of Chemistry , Dong-A University , Busan , 604-714 ,KoreaPublished online: 17 Sep 2012.PLEASE SCROLL DOWN FOR ARTICLETaylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis,our agents, and our licensors make no representations or warranties whatsoever as tothe accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sourcesof information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.D o w n l o a d e d b y [U n i v e r s i t y o f O t t a w a ] a t 19:25 09 A p r i l 2014Mol.Cryst.Liq.Cryst.,V ol.567:pp.102–109,2012Copyright ©Taylor &Francis Group,LLC ISSN:1542-1406print /1563-5287online DOI:10.1080/15421406.2012.702439Synthesis and Characterization of Carbazole-based Copolymers Containing Benzothiadiazole Derivativefor Polymer Light-Emitting DiodesJIN SU PARK,1SUNG-HO JIN,1,∗YEONG-SOON GAL,2JUN HEE LEE,3AND JAE WOOK LEE 41Department of Chemistry Education,Interdisciplinary Program of Advanced Information and Display Materials,and Institute for Plastic Information and Energy Materials,Busan 609-735,Korea 2Polymer Chemistry Lab,Kyungil University,Hayang 712-701,Korea 3Department of Advanced Materials Engineering,Dong-A University,Busan 604-714,Korea 4Department of Chemistry,Dong-A University,Busan 604-714,KoreaA new thermally robust electroluminescent (EL)carbazole-based π-conjugated copolymer,including poly[3,7-(N-hexylcarbazole)-co-4,7-{5,6-bis(3,7-dimethyloctylo-xymethyl)-2,1,3-(benzothiadiazole)}](PCz-co -P2C 10BT )was synthesized and used to fabricate the efﬁcient polymer light-emitting diodes (PLEDs).The glass transi-tion temperature of the PCz-co -P2C 10BT (105◦C)was found to be higher than that of poly(9,9-dialkylﬂuorene)derivatives.We fabricated PLEDs in ITO/PEDOT/light-emitting polymer/Alq 3/LiF/Al conﬁguration.The new copolymer was found to have green emission color (523nm).The maximum brightness and external quantum efﬁciency of PCz-co -P2C 10BT were 260cd/m 2at 14V and 0.22%,respectively.Keywords benzothiadiazole;carbazole;polymer light-emitting diodes;PhOLEDs;IntroductionEver since Tang and Vanslyke constructed organic light-emitting diodes (OLEDs)using organic materials as emitters,OLEDs continue to attract intensive interest because of their numerous applications in full-color ﬂat-panel displays and other lighting sources [1,2].Polymer light-emitting diodes (PLEDs)have received remarkable scientiﬁc and in-dustrial attention due to their potential applications in large area ﬂat-panel displays [3].π-Conjugated polymers are attractive because of their applicability to PLEDs [4].Among the various types of π-conjugated polymers reported,poly(N-alkylcarbazole)(PCz)and its derivatives exhibit the most promise for PLED applications and have been widely used,because of their chemical and thermal stability,high photoluminescent (PL)quantum efﬁciency,and ease of property tuning by copolymerization with various comonomers.∗Address correspondence to Sung-Ho Jin,Department of Chemistry Education,Interdisciplinary Program of Advanced Information and Display Materials,and Center for Plastic Information System,Pusan National University,Busan 609-735,Korea.E-mail:shjin@pusan.ac.kr and Jae Wook Lee,Department of Chemistry,Dong-A University,Busan,604-714,Korea.E-mail:jlee@donga.ac.kr[304]/102D o w n l o a d e d b y [U n i v e r s i t y o f O t t a w a ] a t 19:25 09 A p r i l 2014Benzothiadiazole Derivative for PLEDs [305]/103PCz derivatives have strong absorption in the near UV region and a low redox potential.The electrochemical and spectroscopic properties of PCz derivatives have been extensively investigated [5].Normally,PCz derivatives emit blue light with a wide band gap.However,by incorporating a narrow band gap comonomers into the carbazole backbone,the emission colors of PCz derivatives could be tuned over the entire visible range [6].The most com-monly used comonomer is the electron deﬁcient 2,1,3-benzothiadiazole (BT)unit,which emits the green color in PLEDs [7,8].In this article,we report the synthesis and charac-terization of a new EL polymer,consisting of poly[3,7-(N-Hexylcarbazole)-co -4,7-{5,6-bis(3,7-dimethyloctyloxymethyl)-2,1,3-(benzothiadiazole)}](PCz-co -P2C 10BT ),aimed at increasing the solubility of resulting copolymer,tuning the emission color from blue to green,and improving the PLED performance.The new copolymer was synthesized with palladium-catalyzed Suzuki polymerizations and was fully characterized.The new EL polymer was used to fabricate efﬁcient PLEDs using PCz-co -P2C 10BT as an emitting layer with ITO/PEDOT/polymer/Alq 3/LiF/Al conﬁguration.ExperimentalCharacterizationCarbazole,N-bromosuceinimide (NBS),sodium hydride,1-bromohexane,n-butyl lithium,2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane,Alq 3,LiF,and aluminum were pur-chased from Aldrich Co.,and used without further puriﬁcation unless otherwise noted.Solvents were dried and puriﬁed by fractional distillation over sodium/benzophenone and handled in a moisture-free atmosphere.The moisture content of THF was below 10ppm.Column chromatography was performed using silica gel (Merck,250–430mesh).The 1H-NMR spectra were recorded on an Inova-500spectrometer and the chemical shifts were recorded in ppm units with chloroform as the internal standard.The UV-visible and the emission spectra were recorded with a Shimadzu UV-3100and Hitachi F-4500ﬂuorescence spectrophotometers.The solid state emission measurements were carried out by supporting each ﬁlm on a quartz substrate,which was mounted to receive front-face excitation at an angle <45o .Polymer ﬁlm was excited with several portions of the visible spectrum using a xenon lamp.The molecular weight and polydispersity of the polymer were determined by gel permeation chromatography (GPC)using a PL gel 5µm MIXED-C column on an Agi-lent 1100series liquid chromatography system with THF as an eluent and calibration with polystyrene standards.Thermal analyses were carried out on a Mettler Toledo TGA/SDTA 851,DSC 822analyzer under an N 2atmosphere at a heating rate of 10◦C/min.Cyclic voltammetry (CV)was carried out in a 0.1M solution of tetrabutylammonium tetraﬂuo-roborate (Bu 4NBF 4)in anhydrous chloroform using a CHI600C at a potential scan rate of 50–100mV/s.Polymer ﬁlm was coated onto a Pt disc electrode (diameter:0.2cm)by dipping the electrode into the polymer solution (10mg/mL).A platinum wire was used as the counter electrode and Ag/AgNO 3electrode was used as the reference electrode.All electrochemical experiments were performed at room temperature in a glove box in an Ar atmosphere.Synthesis of 3,6-Dibromo-9H-Carbazole (1)To a solution of carbazole (5g,29.9mmol)in anhydrous tetrahydrofurane (THF)was added NBS (10.64g,59.8mmol)at room temperature.The reaction mixture was stirred atD o w n l o a d e d b y [U n i v e r s i t y o f O t t a w a ] a t 19:25 09 A p r i l 2014104/[306]J.S.Park et al.85◦C for 48h.Then the reaction mixture was diluted with water and extracted with ethyl acetate.The combined organic layers were washed with brine,dried anhydrous MgSO 4and concentrated.The product was puriﬁed by recrystallization.(1.9g,98%)1H-NMR (Acetone-d 6,δppm):7.20–7.31(m,4H),8.41(s,2H);13C-NMR (CDCl 3,δppm):129.2,121.1,121.0,119.7,117.0,113.3.Anal.Calcd for (C 12H 7Br 2N):C 44.35,H 2.17,N 4.31Found :C 46.12,H 2.24,N 4.13.Synthesis of 3,6-Dibromo-N-Hexylcarbazole (2)60mL of dried THF in a 100mL three neck ﬂask was purged with a continuous N 2ﬂow.Sodium hydride (0.2g,7.6mmol)was added into the ﬂask to be stirred.3,6-Dibromo-9H-carbazole (3g,9.2mmol)was added slowly into the mixture.1-Bromohexane (1.1g,7.6mmol)diluted by THF (10mL)was added dropwise into the ﬂask and the content in the ﬂask was reﬂuxed for 12h.The reactant was cooled to room temperature and then the solvent was stripped off by evaporation.The residue was mixed with H 2O (60mL)and extracted with ethyl acetate.The extracted solution was dried with anhydrous MgSO 4and then ﬁltrate.Yellowish viscous liquid was obtained by evaporation of the solvent and was puriﬁed by employing a silica gel column with an eluent of an ethyl acetate:hexane:methylene chloride (1:7:2).The product was puriﬁed by recrystallization (4.36g,80%).1H-NMR (CDCl 3,δppm):0.84(m,3H),1.33(m,6H),1.81(m,2H),4.20(t,2H),7.24(d,2H),7.56(q,2H),7.76(d,1H),7.86(s,1H),8.17(s,1H).13C-NMR (CDCl 3,δppm):130.3,121.1,121.0,120.0,117.0,113.3,60.9,31.5,30.4,27.0,22.7,14.01.Anal.Calcd for (C 18H 19Br 2N):C 52.84,H 4.68,N 3.42Found :C 50.94,H 4.86,N 3.55.Synthesis of 3,6-bis(4,4,5,5-Tetramethyl-1,3,2-Tioxaborolan-2-yl)-N-Hexylcarbazole (3)To a solution of 3,6-dibromo-N-hexylcarbazole (0.2g,0.49mmol)in anhydrous THF (10mL)at −78◦C,n -butillithium was added by syringe.The mixture was stirred at −78◦C for 2hr.2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (0.2ml,1.1mmol)was added slowly to the solution and the mixture was stirred for 2h at −78◦C.The resulting mixture was warmed to room temperature and stirred for 24h.The mixture was poured into water and was extracted with diethyl ether.The organic layer was washed with brine and dried over anhydrous MgSO 4.The solvent was removed by distillation and the residue was puriﬁed by column chromatography.The product was white solid in 43%yield.1H-NMR (CDCl 3,δppm):0.86(t,3H),1.41(m,30H),1.83(t,2H),4.29(t,2H),7.39(d,2H),7.98(d,2H),8.78(s,2H).13C-NMR (CDCl 3,δppm):130.8,122.0,121.0,120.0,118.9,111.1,83.1,60.9,31.5,30.4,27.0,22.7,21.3,14.1.Anal.Calcd for (C 30H 43B 2NO 4):C 71.59,H 8.61,N 2.78,O 12.72Found :C 74.31,H 8.95,N 2.89.4,7-Dibromo-5,6-bis(Decyloxymethyl)Benzo[c][1,2,5]thiadiazole (4)1H-NMR (CDCl 3,δppm):0.92(m,6H),1.31–1.36(m,30H),1.86–1.88(m,4H),3.38(t,4H),4.72(d,4H).13C-NMR (CDCl 3,δppm):159.7,142.3,114.2,72.0,68.2,31.8,30.0,29.6,29.3,25.9,22.7,14.1.Anal.Calcd for (C 28H 46Br 2N 2O 2S):C 53.0,H 7.31,N 4.41,O 5.04Found :C 51.04,H 7.60,N 4.56.D o w n l o a d e d b y [U n i v e r s i t y o f O t t a w a ] a t 19:25 09 A p r i l 2014Benzothiadiazole Derivative for PLEDs [307]/105Synthesis of Poly[3,7-(N-Hexylcarbazole)-co -4,7-{5,6-bis(3,7-Dimethyloctyloxymethyl)-2,1,3-(Benzothiadiazole)}](PCz-co -P2C 10BT)(1:1mol%)The copolymer was prepared by the Suzuki coupling reaction between 3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-N-hexylcarbazole (3)and 5,6-bis(3,7-dimethyloctyloxymethyl)-4,7-dibromo-2,1,3-benzothiadiazole (4).A mixture of compound 3(0.3g,0.6mmol),compound 4(0.38g,0.6mmol)and Pd(PPh 3)4(20mg,0.025mmol)in toluene (5mL)was stirred at 95◦C.To this ﬂask,aqueous 2M Na 2CO 3(0.5mL)was added and the mixture was stirred for 48h at 100◦C.The polymer was end-capped by adding a small amount of bromobenzene to remove the boronic ester end group,followed by stirring for 2h.The polymerization solution was poured into methanol (500mL)and the crude polymer was successively Soxhlet extracted with methanol,isopropyl alcohol and hexane to remove the unreacted monomers,impurities and oligomers.The collected powder was dried under vacuum overnight at 40◦C to afford PCz-co -P2C 10BT (70mg,37%)as a dark purple powder.1H-NMR (CDCl 3,δppm):8.0–7.4(br,6H,aromatic protons),4.8–4.5(br,4H,methoxy protons next to oxygen),4.5–4.2(br,2H,methoxy protons next to nitrogen),3.6–3.2(br,4H,methylene protons next to oxygen),1.8–0.6(br,47H,aliphatic protons).Anal.Calcd for (C 46H 67N 3O 2S)n :C,79.58;H,9.26;N,6.33;S,4.83Found :C,73.35;H,5.40;N,8.65:S,3.72.Fabrication of PLED and MeasurementsOptical thin ﬁlm of the PCz-co -P2C 10BT was obtained by spin-coating from their toluene solutions.Polymer solution was ﬁltered with 0.45µm PP syringe ﬁlter (Whatman)prior to spin-coating.Film for optical absorption and PL measurement was spin-coated onto quartz substrates and dried over 10min at 120◦C under N 2atmosphere.Glass substrate coated with ITO,whose conductivity was 15 /cm 2(Samsung Corning)served as anode electrode.The ITO substrates were cleaned successive rinsing with acetone and wiping with non-woven tissues to remove adhering glass particle from cutting and ultrasonic treatment with distilled water,acetone,isopropyl alcohol,and ﬁnally distilled water and dried with N 2gas.The PEDOT/PSS (Baytron CH8000,30nm)as a hole injection and decreasing roughness of ITO surface was spin-coated from aqueous solution with 10wt%of isopropyl alcohol.A solution of PCz-co -P2C 10BT (0.5–1.5wt%in toluene)was ﬁltered through 0.45µm PP syringe ﬁlter and deposited by spin coating onto the PEDOT/PSS layer with uniform and pinhole free ﬁlms as a thickness around 100nm.Finally,cathode electrode,Alq 3(15nm)/LiF (1nm)/Al (200nm)triple layer,was vacuum (1×10−6torr)evaporated onto the resulting emitting layer.The active area of the PLED was approximately 4mm 2.The thickness of the active layer was measured using a KLA Tencor Alpha-step IQ surface proﬁlometer.For the measurements of device characteristics,current density-voltage-luminescence (J-V-L )characteristics were measured using a current/voltage source (Keithly 238)and an optical power meter (CS-1000,LS-100).All processes and measurements mentioned above were carried out in the open air at room temperature.Results and DiscussionCarbazole-based polymers have many advantages such as good hole injection and trans-porting properties,thermal stability and tuning the emission colors.Its unique chemical properties are effectively raise the highest occupied molecular orbital (HOMO)energy level and reduce the barrier height for hole injection between the anode layer and the emittingD o w n l o a d e d b y [U n i v e r s i t y o f O t t a w a ] a t 19:25 09 A p r i l 2014106/[308]J.S.Park et al.NaH, (CH )BrTHF(2)(3)4NB B OO O O+NSNC 10H 21OOC 10H 21Tetraethylammonium hydroxideN S NBrBrOO C 10H 21C 10H 21(3)(4)N*n (4)PCz-co -P2C 10BT(1)Scheme 1.Synthetic process of the PCz-co -P2C 10BTlayer in PLEDs.Scheme 1outlines the synthetic routes of the monomer and the PCz-co -P2C 10BT .Compound (2)was prepared from bromination of carbazole,followed by alkylation.Finally we introduced boronic acid at the position of 3-and 6-in compound (3)for Suzuki polymerization by treating n -BuLi.5,6-Bis(3,7-dimethyloctyloxymethyl)-4,7-dibromo-2,1,3-benzothiadiazole (4)was synthesized according to the published procedures [9].The polymerization was carried out using palladium(II)acetate,tricyclohexylphos-phine,tetraethylammonium hydroxide aqueous solution (20%w/w)in dried toluene underD o w n l o a d e d b y [U n i v e r s i t y o f O t t a w a ] a t 19:25 09 A p r i l 2014Benzothiadiazole Derivative for PLEDs [309]/107N 2atmosphere for 48–72h.During the polymerization,the ﬂuorescent light was observed without any precipitation.The PCz-co -P2C 10BT was completely soluble in various organic solvents such as chloroform,chlorobenzene,toluene,and THF.Molecular structures of the monomer and the PCz-co -P2C 10BT were identiﬁed by 1H-and 13C-NMR and elemen-tal analysis.To improve color purity and PLED performance,the PCz-co -P2C 10BT was further puriﬁed by multiple soxhlet extraction with different solvents including methanol,acetone and ﬁnally chloroform to remove unreacted monomers and inorganic impurities.The solution of PCz-co -P2C 10BT was ﬁltered through the methanol precipitation and then dried in vacuo.From these processes,the highly puriﬁed and narrow polydispersity of PCz-co -P2C 10BT was obtained.The weight-average molecular weight (Mw)and the polydispersity of the PCz-co -P2C 10BT were 5,570and 1.21,respectively.The glass tran-sition temperature of PCz-co -P2C 10BT was 105◦C.TGA thermogram was measured at temperature of 5%weight loss for PCz-co -P2C 10BT and showed the stable up to 279◦C.Higher thermal stability of the light emitting polymer is one of the most critical require-ments to operate the PLED especially for blue light emitting it needs higher turn on voltage compared to other color light emitting polymers.The absorption and PL spectra of the PCz-co -P2C 10BT in CHCl 3solution and the polymer ﬁlm spin-coated onto quartz with CHCl 3solution were measured at room temper-ature.Figure 1shows the optical absorption,PL spectrum of PCz-co -P2C 10BT in solution state and EL spectra in ﬁlm state.The PCz-co -P2C 10BT exhibited two absorption peaks at 287nm and 419nm which can be attributed to the carbazole and 2,1,3-benzothiadiazole segments in the polymer.The absorption and emission peaks in ﬁlm state were slightly red shifted comparing with the solution state because of the interchain aggregation.The absorption,emission maxima and energy band gap of PCz-co -P2C 10BT in solution and ﬁlm states are summarized in Table 1.To investigate the charge injection and transport in PCz-co -P2C 10BT ,it is very impor-tant to determine the energy band diagrams of the HOMO and LUMO binding energy levels with respect to the ferrocene standard by using cyclic voltammetry (CV)measurements and the band gaps obtained from the optical absorption spectrum.The ionization potentialI n t e n s i t y [N o r m a l i z e d ]Wavelength [nm]Figure 1.UV-visible absorption,PL and EL spectra of PCz-co -P2C 10BT .D o w n l o a d e d b y [U n i v e r s i t y o f O t t a w a ] a t 19:25 09 A p r i l 2014108/[310]J.S.Park et al.Table 1.Electro-Optical properties of PCz-co -P2C 10BT .Abs (nm)aPL (nm)a Polymer Solution Film Solution Film EL(nm)b Eg(eV)c PCz-co -P2C 10BT4074194895155222.64a Measured in the thin ﬁlm onto the quartz substrate.bEL spectras were measured cathode using by LiF/Al as cathode.cBand gap estimated from the onset wavelength of the optical absorption.(IP)and electron afﬁnity (EA)or their associated HOMO and LUMO energy levels were estimated from the onset oxidation data and optical band edges.IP/HOMO =E ox +4.8eV and EA/LUMO =E HOMO +E g ,where an SCE energy level of -4.8eV below the vacuum level was used [10].The HOMO energy level and optical band gap of PCz-co -P2C 10BT were 5.55eV and 2.63eV ,respectively.The major carriers in PCz-co -P2C 10BT are holes rather than electrons,due to the lower band offset between the ITO and HOMO energy levels.The band offset was 0.80eV for hole injection at the interface of the ITO/HOMO state.To investigate the PLED performance of PCz-co -P2C 10BT as an emitting layer,we fab-ricated PLED with a conﬁguration of ITO/PEDOT/PCz-co -P2C 10BT /Alq 3/LiF (1nm)/Al (120nm).The maximum EL peak of PCz-co -P2C 10BT was slightly red-shifted with re-spect to the PL peak of ﬁlm state as shown in Figure 1.The red-shifted EL spectrum was attributed to the injected current density,which extended the effective conjugation length.The maximum emission peak of PCz-co -P2C 10BT was at 523nm,which corresponded to a green color.Figure 2shows the current density-voltage-luminescence characteristics of the ITO/PEDOT/PCz-co -P2C 10BT /Alq 3/LiF (1nm)/Al (120nm)device.The turn-on volt-age of PCz-co -P2C 10BT was 10V .The PLED performances of PCz-co -P2C 10BT are2468101214020406080100Bias [V]C u r r e n t d e n s i t y [m A /c m 2]10-210-110101102Luminance [cd/m 2]Figure 2.Current density-Luminescence-voltage (J-V-L )characteristic of PCz-co -P2C 10BT .D o w n l o a d e d b y [U n i v e r s i t y o f O t t a w a ] a t 19:25 09 A p r i l 2014Benzothiadiazole Derivative for PLEDs [311]/109Table 2.PLED Performance of PCz-co -P2C 10BT.Polymer Turn-on (V)PE a (lm/W)Lmax b (cd/m 2)EQE (%)PCz-co -P2C 10BT100.182600.22a Maximum power efﬁciency.bMaximum luminescence.summarized in Table 2.The maximum brightness,power efﬁciency and external quantum efﬁciency of PCz-co -P2C 10BT were 260cd/m 2,0.18lm/W and 0.22%,respectively.ConclusionsThis study focused on the molecular design and synthesis of bipolar struc-ture of poly[3,7-(N-Hexylcarbazole)-co -4,7-{5,6-bis(3,7-dimethyloctyloxymethyl)-2,1,3-(benzothiadiazole)}](PCz-co -P2C 10BT )for PLED applications.The resulting EL poly-mer was highly soluble in common organic solvents,which allowed being easily spin-coated onto glass substrates with high quality optical thin ﬁlms.We fabricated PLEDs in ITO/PEDOT/PCz-co -P2C 10BT /Alq 3/LiF (1nm)/Al (120nm)conﬁguration.The max-imum brightness and power efﬁciency were 260cd/m 2at 14V and 0.18lm/W at 11V ,respectively.AcknowledgementsThis work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF)grant funded from the Ministry of Education,Science and Technology (MEST)of Korea for the Center for Next Generation Dye-sensitized Solar Cells (No.2011–0001055)and the New &Renewable Energy program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP)grant (No.20103020010050)funded by the Ministry of Knowledge Economy,Republic of Korea.References[1]Tang,C.W.,&Vanslyke,S.A.(1987).Appl.Phys.Lett ,51,913.[2]Burroughes,J.H.,Bradley,D.D.C.,Brown,A.R.,Marks,R.N.,Mackay,K.,Friend,R.H.,Burns,P.L.,&Holmes,A.B.(1990).Nature ,347,539.[3]Schwab,P.F.H.,Smith,J.R.,&Michel (2005).J.Chem.Rev ,105,1197.[4]Sonntag,M.,&Strohriegl,P.(2004).Chem.Mater ,16,4736.[5]Wei,Y .,Wang,B.,Wang,W.,&Tain,J.(1995).Tetrahedron Lett ,36,665.[6]Liu,R.,Xiong,Y .,Zeng,W.,Wu,Z.,Du,B.,Yang,W.,Sun,M.,&Cao,Y .(2007).Macromol.Chem.Phys ,208,1503.[7]Bernius,M.T.,Inbasekaran,M.,O’Brien,J.,&Wu,W.(2000).Adv.Mater ,12,1737.[8]Herguth,P.,Jiang,X.,Liu,M.S.,&Jen,A.K.Y .(2002).Macromolecules ,35,6094.[9]Yoon,K.J.,Park,J.S.,Lee,S.J.,Song,M.,Shin,I.A.,Lee,J.W.,Gal,Y .S.,&Jin,S.H.(2008).Journal of Polymer Science:Part A:Polymer Chemistry ,46,6762.[10]Jandke,M.,Strohriegl,P.,Berleb,S.,Werner,E.,&Brutting,W.(1998).Macromolecules ,31,6434.D o w n l o a d e d b y [U n i v e r s i t y o f O t t a w a ] a t 19:25 09 A p r i l 2014。