An ECR hydrogen negative ion source at CEASaclay preliminary results

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电解水生产的氧气液化流程

电解水生产的氧气液化流程英文回答：Electrolysis is a process that uses an electric current to split water molecules into hydrogen and oxygen gas. In the production of liquid oxygen from electrolysis, several steps are involved.Firstly, water is purified to remove impurities that may interfere with the electrolysis process. This is done by passing the water through filters and ion exchange resins. The purified water is then stored in a tank.Next, the purified water is electrolyzed using an electrolysis cell. The cell consists of two electrodes, an anode and a cathode, which are submerged in the purified water. When an electric current is passed through the electrodes, water molecules are split into hydrogen gas at the cathode and oxygen gas at the anode.The hydrogen gas is collected and stored separately, as it is a valuable byproduct that can be used in various industries. The oxygen gas, on the other hand, is directed into a liquefaction unit.In the liquefaction unit, the oxygen gas is cooled and compressed to convert it into a liquid state. This is achieved by passing the gas through a series of heat exchangers and compressors. The heat exchangers remove heat from the gas, causing it to cool down, while the compressors increase the pressure of the gas.Once the oxygen gas has been cooled and compressed, it is passed through a distillation column. The distillation column separates the oxygen gas from any remaining impurities, such as trace amounts of nitrogen or argon. The purified liquid oxygen is then collected and stored in cryogenic storage tanks.中文回答：电解水是一种利用电流将水分子分解成氢气和氧气的过程。

氢能电解槽英语术语

氢能电解槽英语术语English Answer：Hydrogen Electrolyzer Terminology.Anode: The electrode in an electrolyzer where oxidation occurs and hydrogen gas is produced.Cathode: The electrode in an electrolyzer where reduction occurs and oxygen gas is produced.Electrolyte: The conductive medium between the anode and cathode that allows the flow of ions.Electrolyzer: A device that uses electricity to split water into hydrogen and oxygen gases.Hydrogen Production Rate (HPR): The rate at which hydrogen gas is produced by an electrolyzer, typically measured in kilograms per hour (kg/h).Alkaline Electrolyzer: An electrolyzer that uses an alkaline electrolyte, such as potassium hydroxide (KOH).Anion Exchange Membrane (AEM) Electrolyzer: An electrolyzer that uses an anion exchange membrane as the electrolyte.Balance of Plant (BOP): The auxiliary equipment and systems that support the operation of an electrolyzer, such as water treatment, gas compressors, and power conditioning.Current Density: The amount of current passing through the electrolyzer per unit area of the electrode, typically measured in amperes per square centimeter (A/cm2).Depolarization: The reduction of the overpotential required for hydrogen evolution, which increases the efficiency of the electrolyzer.Efficiency: The ratio of the amount of energy required to produce hydrogen to the amount of energy stored in thehydrogen gas produced.Electrolysis: The process of using electricity to decompose water into hydrogen and oxygen gases.Faradaic Efficiency: The ratio of the actual amount of hydrogen produced to the theoretical amount that should be produced based on the amount of electricity used.Hydrogen Generation Unit (HGU): A system that combines an electrolyzer with auxiliary equipment, such as water treatment, gas compressors, and power conditioning.Ion Exchange Membrane (IEM) Electrolyzer: An electrolyzer that uses an ion exchange membrane as the electrolyte.Operating Voltage: The voltage required to drive the electrolysis reaction in an electrolyzer.Oxygen Production Rate (OPR): The rate at which oxygen gas is produced by an electrolyzer, typically measured inkilograms per hour (kg/h).Proton Exchange Membrane (PEM) Electrolyzer: An electrolyzer that uses a proton exchange membrane as the electrolyte.Stack: A series of electrolyzer cells connected electrically in series.Thermodynamic Efficiency: The ratio of the maximum possible amount of energy that can be stored in the hydrogen produced to the amount of electricity required to produce it.Water Splitting: The process of splitting water into hydrogen and oxygen gases using electrolysis.中文回答：氢能电解槽术语。

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Ž.Surface and Coatings Technology1312000317᎐325Plasma-based low-energy ion implantation forlow-temperature surface engineeringM.K.Lei a,U,Z.L.Zhang a,T.C.Ma ba Surface Engineering Laboratory,Department of Materials Engineering and State Key Laboratory for Materials Modiﬁcation by Laser,Ionand Electron Beams,Dalian Uni¨ersity of Technology,Dalian116024,PR Chinab State Key Laboratory for Materials Modiﬁcation by Laser,Ion and Electron Beams,Dalian Uni¨ersity of Technology,Dalian116024,PR ChinaAbstractThis paper summarizes the plasma-based low-energy ion implantation technique,including plasma source ion nitriding r carburizing and plasma source low-energy ion enhanced deposition of thinﬁlms,developed from a combination of two techniques based on conventional plasma-based ion implantation and low-energy ion beam implantation for improvement in wearŽ.resistance and corrosion resistance for metals and alloys.An electron cyclotron resonance ECR microwave plasma source is used to produce the plasma with the high plasma density,electron temperature and ionization degree.The ions are accelerated from the plasma by a low pulsed negative bias of y0.4᎐y3kV,which is similar to the cathode potential of conventional plasma thermo-chemical diffusion processing.The low process temperature is in the range from150ЊC to500ЊC,which corresponds to the upper limit of conventional ion beam implantation and to the lower limit of plasma thermo-chemical diffusion processing, respectively.Low-energy ion implantation and simultaneous indiffusion is the main mass transfer mechanism,and direct thermo-chemical diffusion absorption is an additional mass transfer mechanism for formation of the nitrided r carburized layer and thinﬁlm.It has been proved that plasma-based low-energy ion implantation technique has the potential for applications in industry for surface modiﬁcation of metals and alloys.ᮊ2000Elsevier Science B.V.All rights reserved.Keywords:Plasma-based low-energy ion implantation;Plasma source ion nitriding;Plasma source ion carburizing;Plasma source low-energy ion enhanced deposition;Surface modiﬁcation;Thinﬁlm;Metal and alloy1.IntroductionŽ.Plasma source ion implantation PSII was originallyw xdeveloped and demonstrated in19861.Subsequently,Ž.plasma immersion ion implantation PIII,as an alter-w x native system to PSII,was reported in19882. Plasma-based ion implantation,including PSII and PIII, has been shown to be very effective in improving the wear and corrosion resistance for metals and alloys w x1᎐4.PIII was also performed at the elevated tempera-U Corresponding author.Ž.E-mail address:mklei@ M.K.Lei.ture due to signiﬁcant heating caused by the ion im-plantation,resulting in diffusion of the implanted species well beyond the implantation range,so increas-ing the thickness of modiﬁed layers.In the pioneering PSII and PIII experiments,a high ion energy from20 to100keV was used,because the pulsed negative bias to accelerate ions from plasma was of y20᎐y100kV, which is consistent with that of conventional ion beam w ximplantation5,6.Between1992and1994,low-energy ion beam implantation that combines the features of plasma thermo-chemical diffusion processing and con-ventional ion beam implantation was developed using aw xlow ion energy of approximately1keV7,8.This can be made to produce the microstructure and the wear0257-8972r00r$-see front matterᮊ2000Elsevier Science B.V.All rights reserved.Ž.PII:S0257-89720000799-4()M.K.Lei et al.r Surface and Coatings Technology1312000317᎐325 318and corrosion resistance for metals and alloys that are similar to the results from conventional ion beam im-plantation,i.e.high-energy ion implantation.Since1992,at the Surface Engineering Laboratory of Department of Materials Engineering and State Key Laboratory for Materials Modiﬁcation by Laser,Ion and Electron Beams,Dalian University of Technology, we have developed the plasma-based low-energy ion implantation technique based on an electron cyclotron Ž.resonance ECR microwave plasma source and a lowŽ.pulsed bias,instead of the direct current DC or radio Ž.frequency RF plasma and the high pulsed bias ofw x conventional plasma-based ion implantation9᎐11. Therefore,plasma-based low-energy ion implantation has both features of conventional plasma-based ion implantation and low-energy ion beam implantation. This technique includes two kinds of surface modiﬁca-tion processes:plasma source ion nitriding r carburizing and plasma source low-energy ion enhanced deposition of thinﬁlms.In the two processes,the low ion energy is used in the range from0.4to3kV,which is similar to the cathode potential of plasma thermo-chemical dif-fusion processing.The process temperature is 150᎐500ЊC,which corresponds to the upper limit of conventional ion beam implantation and to the lower limit of thermo-chemical diffusion processing,respec-tively.A lot of experimental results have shown that the two processes have the speciﬁc advantages over plasma-based ion implantation and plasma thermo-w xchemical diffusion processing9᎐19.This paper aims to review the plasma-based low-en-ergy ion implantation technique for low-temperature surface engineering in order to improve the wear and corrosion resistance for metals and alloys.We describe the apparatus and operating principle of plasma source ion nitriding r carburizing and plasma source low-en-ergy ion enhanced deposition.And then the summaries for their process characteristics are given in detail based on the experimental results.Finally,we point out the potential for the applications of this technique in industry.2.Plasma source ion nitriding r carburizing2.1.ApparatusFig.1shows the schematic diagram of the ECRw x microwave plasma source ion nitriding apparatus9. The complete apparatus consists ofﬁve units:mi-crowave power and transmission line,ECR microwave plasma source,process chamber,low pulsed negative bias power,and vacuum pump package.Plasma parameters of the ECR microwave plasma stream were measured by a single Langmuir probe and optical emis-Ž.sion spectrometry OES.The sample-holder waselec-Fig.1.A schematic diagram of the ECR microwave plasma source ion nitriding apparatus.()M.K.Lei et al.r Surface and Coatings Technology1312000317᎐325319trically isolated from the process chamber,and was supplied with a low pulsed negative bias of y0.4to y3 kV.The pulse repetition rate and pulse length of negative bias were independently and continuously variable.An auxiliary heater was contained in the sample-holder to regulate the process temperature from 150ЊC to450ЊC.The sample temperature was always measured during the process by a thermocouple. Fig.2shows the nitrogen plasma density measured in plasma source ion nitriding.A high nitrogen plasma density of approximately5=1011᎐8=1011cm y3was obtained,and the corresponding electron temperature was approximately7᎐pared with DC and RFw x w x plasmas used,respectively,in PSII3and PIII4,the ECR microwave plasma possesses the high plasma den-sity,electron temperature,and ionization degree.The ion N q and active molecular N U were the main species 22in the ECR microwave plasma according to the wave-length and intensity of the spectral lines in OES,as shown in Fig.3.Plasma source ion carburizing has a similar appara-tus structure to that of plasma source ion nitriding.The only difference is the plasma composition because a mixture of methane and hydrogen was used.The typi-cal operation parameters for plasma source ion nitrid-ing r carburizing into pure iron and steel are listed in Table1.2.2.Mass transfer mechanismThe ECR microwave plasma streamed and diffused from the ECR microwave plasma source into the process chamber,and immersed the samples on the sample-holder with a sheath,which was a self-bias sheath due to presence of a self-bias ofapproximately Fig. 2.The ECR microwave nitrogen plasma density for plasma source ion nitriding measured by a Langmuir probe.w x10V on the samples12.The thickness of the self-bias sheath was also of the order of the magnitude of the Debye length,approximately10y2mm in the process. Applying a negative bias pulse of y0.4᎐y3kV to the samples formed an ion matrix sheath from the self-bias sheath,then started to extend,ﬁnally developing into theﬁnal sheath,i.e.the sheath of plasma source ion nitriding r carburizing.The thickness of the sheaths, less than approximately1mm for either the ion matrix sheath or theﬁnal sheath,was estimated bycalculation Fig.3.The OES of the ECR microwave nitrogen plasma for plasma source ion nitriding.()M.K.Lei et al.r Surface and Coatings Technology 1312000317᎐325320Table 1Typical ECR microwave plasma source ion nitriding r carburizing parameters Microwave power150᎐600WNitriding r carburizing precursor N r 20%CH q 80%H 242Plasma density 1112y 3N 5=10᎐1.5=10cm 21111y 320%CH q 80%H 2=10᎐8=10cm 42Electron temperature N 7᎐10eV 220%CH q 80%H 7᎐9eV42y 3Base pressure1.5=10Pay 2Ž.Ž.Nitriding r carburizing pressure 5᎐10r 1᎐2=10Pa Pulsed negative bias Voltagey 0.4᎐y 3kV Repetition rate 100᎐1000Hz Length50᎐500␮sy 2Ž.Ž.Nitriding r carburizing ion current density 0.4᎐1.2r 1᎐2mA cm Nitriding r carburizing process temperature 150᎐450ЊC r 350᎐500ЊC Nitriding r carburizing time2᎐8husing the plasma parameters in Table 1.This means that the extent of the three sheaths is limited during the process.Fig.4shows the schematic representation of the model of the mass transfer mechanism,taking plasma source ion nitriding as an example.The ions in the evolving sheaths were implanted into the samples dur-ing the negative pulse bias.Considering the ion implan-tation process as independent of process temperature,the implantation depth and dose can be approximately Ž.calculated using transport of ions in matter TRIM .The implantation depth for N qwith an ion energy of 22kV was approximately 2.5nm.The implantation doseq Žy 2.for N ,D ions cm ,was given by 2imp Ž.D s N r e j d ␶s 2it r e1H imp s ␶where e is the charge on the electron,j is the current s density,␶is the pulse length,N is the number of pulses,t is the total process time,and i is the average ion current density during the nitriding.In plasma source ion nitriding,i was in the range of 0.4᎐1.2mA cm y 2,giving a high implantation doseof approximately 1019᎐1020ions cm y 2during a nitriding time of 4h.Because of presence of a temperature ﬁeld in the sample caused by both the auxiliary heater and ion bombardment,signiﬁcant thermal diffusion of the im-planted nitrogen took place from the surface.The nitrogen concentration distribution on the surface mainly depends on D and the process temperature.imp The D has a dynamic equilibrium relationship with imp the thermal diffusion ﬂux,J ,and the nitrogen concen-tration on the surface,C ,as follows:N Ž.D s J q C 2imp NŽ.When Eq.2attained the steady-state condition,agradient distribution of nitrogen concentration with apeak concentration,C ,was established on the surface.N It can be considered that the dimension of presence of C was in the range of implantation,i.e.in the im-N planted layer.For a certain D ,J and C were imp N affected by the process temperature and the composi-tion and structure of the matrix of the sample.After the end of a negative bias pulse,the nitrogen absorption by low-energy ion implantation ﬁnished onFig.4.A schematic representation of the model of the mass transfer mechanism for plasma source ion nitriding.()M.K.Lei et al.r Surface and Coatings Technology1312000317᎐325321the surface.Alternatively,in between the negative biaspulses,another nitrogen absorption by thermo-chem-ical diffusion occurred into the samples immersed in the ECR microwave plasma.In order to understand the effect of the direct thermo-chemical diffusion on the mass transfer mechanism,a simulative experiment was performed.This is a plasma carburizing process under the same process condition as that of plasma source ion carburizing in between the negative bias pulses,as shown in Table1,because of the same mass transfer mechanism between plasma source ion nitrid-w xing r carburizing11.Fig.5a,b shows the carbon concentration proﬁle on the surfaces of plasma carburized and plasma source ion carburized pure iron,respectively,using a mixedgas precursor of20%CH and80%H at a process42 temperature of350ЊC during a carburizing time of8h.A thin carburized layer was formed on the surface to a depth of approximately200nm with a maximum car-bon concentration of5at.%by plasma carburizing. Plasma source ion carburizing yielded a high carbon concentration layer approximately10␮m thick with a peak carbon concentration of approximately25at.%. In plasma source ion nitriding r carburizing,therefore, low-energy ion implantation plays a decisive role in the absorption of nitrogen r carbon.The low-energy ion implantation and simultaneous indiffusion is the main mass transfer mechanism in the process.Direct thermo-chemical diffusion absorption has an additional mass transfer effect,and can improve the environment for low-energy ion implantation during the next bias pulse and prevent the recombination of implanted ni-trogen r carbon on the surface.Plasma-based low-energy ion implantation has a main mass transfer mechanism,low-energy ion implantation and simultaneously indiffusion,and an additional mass transfer mechanism,direct thermo-chemical diffusion absorption.2.3.Process characteristics2.3.1.Nitriding r carburizing efﬁciency at low temperature The lower limit of process temperature for conven-w x tional plasma nitriding is approximately350ЊC20,21. The enhanced plasma nitriding r carburizing processes can be performed at a low temperature of approxi-w xmately300ЊC22,23.Plasma source ion nitriding into pure iron formed a continuous nitride layer approxi-w x mately 1.5␮m thick at150ЊC during2h12.A 10-␮m-thick carburized layer composing a Fe C phase3on the outer surface and a hardened diffusion zone was obtained on plasma source ion carburized pure ironw x and35CrMo low alloy steel at350ЊC for8h11. Plasma source ion nitriding r carburizing was carried out at a low process temperature.As a result,thelower Fig.5.The carbon concentration proﬁle on the surfaces of nitrided Ž.Ž.pure iron by:a plasma carburizing;and b plasma source ioncarburizing using a mixed gas of20%CH and80%H at a process42 temperature of350ЊC.limit of the nitriding process temperature is further reduced down to approximately200ЊC.PIII into0.3wt.%mild steel with an implantation dose of7=1017ions cm y2at340ЊC produced a nitro-w x gen modiﬁed layer approximately1␮m thick4.At 400ЊC,a4.5-␮m-thick nitrogen ion implantation layer was obtained during125min on the low-energy ionw xbeam implanted AISI304stainless steel8.PlasmaŽ. source ion nitriding into1Cr18Ni9Ti18-8type stain-Ž.less steel formed a high nitrogen f.c.c.phase␥layerN6᎐12␮m thick with a high hardness of approximatelyw xHV2000at380ЊC during4h9,19.In plasma source ion nitriding r carburizing the ECR microwave plasma, which has the high plasma density,electron tempera-ture,and ionization degree,ensures a higher implanta-w xtion dose by1᎐2orders than that of PIII2,4andw xlow-energy ion beam implantation8,despite PIII and low-energy ion beam implantation has a similar mass transfer mechanism to that of plasma source ion nitrid-ing r carburizing.The high nitrogen r carbon concentra-tion on the nitrided r carburized surfaces accelerates diffusion of the implanted nitrogen r carbon species in-ward and prevents them outward to recombination. 2.3.2.Potential applicationsCompared with PSII and PIII,plasma source ion()M.K.Lei et al.r Surface and Coatings Technology1312000317᎐325322Table2Typical ECR microwave plasma source low-energy ion enhanced deposition parameters for TiNﬁlmsMicrowave power150᎐600W1112y3 Nitrogen plasma density5=10᎐1.5=10cm Nitrogen plasma electron temperature7᎐10eVy3Base pressure 1.5=10Pay1Ž.Working pressure 1.1᎐2.1=10Pay1Ž.Partial pressure of nitrogen0.1᎐0.3=10Pay1Ž.Partial pressure of argon 1.0᎐2.0=10Pa Magnetron sputtering targetVoltage300᎐600VCurrent0.15᎐0.80APulsed negative biasVoltage y0.4᎐y3kV Repetition rate100᎐1000HzLength50᎐500␮sProcess temperature-200ЊCDeposition time0.25᎐5hnitriding r carburizing has the sheaths of small extent, leading to not only improvement in uniform coverage for the samples with complex shape or small holes but also an increase in stability of the working mode.This process can independently control and measure the ionŽimplantation energy,implantation dose rate current .density and process temperature;the required process temperature is easily achieved during the process.Fur-thermore,no powerful powers demanded for low pulsed negative bias solved the problems from the second electron emission and X-ray radiation,thereby a cost-effective and work-efﬁcient system can be attained. Plasma source ion nitriding r carburizing provides great experimentalﬂexibility,low unit cost,and technologi-cally simple apparatus design.This technique has a great potential for applications in industry.3.Plasma source low-energy ion enhanced deposition of thinﬁlms3.1.ApparatusFig.6shows the schematic diagram of the ECR microwave plasma source low-energy ion enhanced de-w xposition apparatus10.The apparatus consists of the sameﬁve units as those in plasma source ionw xnitriding r carburizing9,11,plus a magnetron sputter-ing system.In order to prepare compoundﬁlms,the sputtering deposition and plasma source low-energy ion implantation phases were alternated during the process.A planar magnetron sputtering target placed under a rotated sample-holder was operated in pure argon at a pressure of0.1᎐1Pa and a supply voltage of300᎐600 V.The maximum transverse component of the mag-neticﬁeld in the front of the sputtering target was 500᎐600G.The sample-holder was also contacted withthe same low pulsed negative bias as that in plasma source ion nitriding r carburizing.The sample tempera-ture was always measured during the process by a thermocouple.For the deposition of metal nitrideﬁlms, the pure nitrogen was used to form the ECR mi-crowave nitrogen plasma.The typical operation parameters for plasma source low-energy ion enhanced deposition of TiNﬁlms are listed in Table2.3.2.Formation mechanism of thinﬁlmsIn plasma source low-energy ion enhanced deposi-tion of metal nitrideﬁlms,such as TiN,AlN,Fe N etc.,xthe metalﬁlm was deposited on the surface of samples facing the sputtering target by magnetron sputtering. With the sample-holder continuously rotated,the sam-ples with the deposited metalﬁlm were immersed in the ECR microwave nitrogen plasma.In each cycle, plasma-based low-energy nitrogen ion implantation was performed into the fresh metalﬁlm to approximately2nm thick,and both direct and recoil effects of N q2 caused to penetrate the metalﬁlm,leading to a mixing of the metal and nitrogen atoms with the atoms of the matrix on the surface.The simultaneous indiffusion of implanted nitrogen also occurred during the process due to the presence of a temperatureﬁeld,although the nitrogen diffusion was very difﬁcult in the metal nitrideﬁlms compared with that in plasma source ion nitrided r carburized layer.As the cycle was running, the metal nitrideﬁlm grew continuously,and an in-termixed layer can form between theﬁlm and sample. When the depositedﬁlm was thicker than the range of ion implantation,low-energy ion implantation no longer had an effect on the intermixing but still affected the structure of theﬁlm.By means of controlling the()M.K.Lei et al.r Surface and Coatings Technology1312000317᎐325323Fig.6.A schematic diagram of the ECR microwave plasma source low-energy ion enhanced deposition apparatus.sputtering deposition rate from the magnetron target Ž.depending on its current and voltage and the ion implantation dose rate from the ECR microwave plasma Žon the repetition rate and length of the pulsed nega-.tive bias,a suitable arrival rate ratio of the ions to the metal atoms can be obtained to attain stoichiometry of the metal compoundﬁlms.3.3.Process characteristics3.3.1.Deposition rate of thinﬁlmsIn order to guarantee the wear and corrosion resis-tance of thinﬁlms,it is necessary to ensure their adhesion on the samples.A negative bias from several hundred volts up to approximately1᎐2kV on the samples is often used to increase the adhesive force of thinﬁlms in the different deposition processes,such asw xmagnetron sputtering ion plating24,vacuum arc de-w xposition25,etc.However,the deposition rate of thin ﬁlms is lowered by the self-sputtering caused by the negative bias.In spite of a high deposition rate that can be obtained in plasma enhanced chemical vapor depo-sition of thinﬁlms,the higher process temperaturesw xalso limit its applications26.In plasma source low energy ion enhanced deposition,use of a low pulsed negative bias apparently inhibits the self-sputtering of thinﬁlms.The independent magnetron sputtering tar-get and ECR microwave plasma source can provide the ﬁxed arrival rate ratio of the nitrogen ions to the metal atoms to maintain a high deposition rate of compound ﬁlms,which is similar to that of the pure metalﬁlms in the process.3.3.2.Adhesi¨e force on samplesFig.7shows the depth proﬁle of atomic concentra-tion for the TiNﬁlm deposited on the A3mild steel sample measured by Auger electron spectroscopy Ž.AES.An intermixing layer approximately40nm thick was observed on the A3mild steel sample,which is similar to that obtained by ion beam enhanced deposi-Ž.w x tion IBED with nitrogen ions of20᎐30keV27,28. The TiN thinﬁlm has a high adhesive force on the M2 high-speed steel samples.Superior adhesion of the metal nitrideﬁlms is responsible for formation of the intermixed layer between theﬁlm and sample.The intermixing layer of the TiNﬁlms is also thicker than those of PSII with IBED,where the metal atoms were provided from the sputtering target and simultaneously PSII into the deposited metalﬁlm occurred on the surface of the samples because of a high pulsed nega-tive bias of20᎐30kV to form the metal nitrideﬁlms w x29,30.We can speculate that the TiNﬁlms on the steels obtained by plasma source low-energy ion en-hanced deposition have a higher adhesive force than()M.K.Lei et al.r Surface and Coatings Technology 1312000317᎐325324Fig.7.AES depth proﬁle of atomic concentration for the TiN ﬁlm deposited on the A3mild steel.that of PSII with IBED,although no test data of adhesion were reported for the TiN ﬁlms by PSII with IBED.3.3.3.Stoichiometry of thin ﬁlmsw x w x In IBED 31and PSII with IBED 30,the stoichio-metric metal nitride ﬁlms can form when the arrival rate ratio of the nitrogen ions to the metal atoms was greater than unity.Plasma source low-energy ion en-hanced deposition provides a controlled environment for the deposition of metal compound ﬁlms.Although the arrival rate ratio could not be accurately measured,the steady deposition conditions were still obtained by means of controlling the nitrogen ion implantation dose rate and the sputtering deposition rate of metal atoms.For the composition of the TiN ﬁlm,as shown in Fig.7,a stoichiometric TiN ﬁlm was observed,ne-glecting the effect of the contaminant carbon of 5at.%and oxygen of 8at.%.3.3.4.Potential applicationsPlasma source low-energy ion enhanced deposition of thin ﬁlms offers great experimental ﬂexibility be-cause it also enables independent control of the nitro-gen ion energy,nitrogen ion implantation dose rate,sputtering deposition rate of metal atoms,and process temperature.It has other distinct advantages over w x IBED 27,28and conventional plasma-based ion im-w x plantation 29,30,including low unit cost,as a result of eliminating a higher-or lower-energy ion source and powerful high voltage pulsed power,and a technologi-cally simple apparatus design,that could be easily scaled to large dimensions.Like the situation in plasma w x source ion nitriding r carburizing 9,11,plasma source low-energy ion enhanced deposition also has applica-tions in industry.4.ConclusionsPlasma-based low-energy ion implantation has been developed from a combination of two techniques based on conventional plasma-based ion implantation and low-energy ion beam implantation in order to decrease the ion implantation energy and eliminate the line-of-sight restrictions of ion implantation processes.This technique includes two kinds of processes for low-tem-perature surface engineering:plasma source ion nitrid-ing r carburizing and plasma source low-energy ion en-hanced deposition of thin ﬁlms.An electron cyclotron Ž.resonance ECR microwave plasma source is used to produce the plasma with the high plasma density,elec-tron temperature and ionization degree.The ions are accelerated from the plasma by a low pulsed negative bias of y 0.4᎐y 3kV,which is similar to the cathode potential of conventional plasma thermo-chemical dif-fusion processing.The low process temperature is in the range from 150ЊC to 500ЊC,which corresponds to the upper limit of conventional ion beam implantation and to the lower limit of plasma thermo-chemical dif-fusion processing,respectively.Low-energy ion implan-tation and simultaneous indiffusion is the main mass transfer mechanism,and direct thermo-chemical diffu-sion absorption is an additional mass transfer mecha-nism for formation of the nitrided r carburized layer and thin ﬁlm.It has been proved that plasma-based low-energy ion implantation technique has the poten-tial for applications in industry for surface modiﬁcation of metals and alloys.AcknowledgementsWe acknowledge the technical assistant of D.Y.Wang,J.D.Chen,Y.Wang,G.L.Wu,S.Y.Chen,Y.H.Li,X.C.Zhang,L.J.Yuan,Y.W.Liu,and Z.P.Zhang in this research.This work is supported by the National Science Foundation of China under Grant Nos.58971074,59402009,and 59771060.Referencesw x Ž.1J.R.Conrad,J.Appl.Phys.621987777.w x 2J.Tendys,I.J.Donnelly,M.J.Kenny,J.T.A.Pollock,Appl.Ž.Phys.Lett.5319882143.w x 3J.R.Conrad,J.L.Radtke,R.A.Dodd,F.J.Worzala,N.C.Tran,Ž.J.Appl.Phys.6219874591.w x 4G.A.Collins,R.Hutchings,J.Tendys,Mater.Sci.Eng.A 139Ž.1991171.w x 5R.Leutenecker,G.Wang,T.Louis,U.Gonser,L.Guzman,A.Ž.Molinari,Mater.Sci.Eng.A 1151989229.w x 6 D.L.Williamson,L.Wang,R.Wei,P.J.Wilbur,Mater.Lett.9Ž.1990302.w x Ž.7 A.V.Byeli,S.K.Shikh,V.V.Kharko,Wear 1591992185.w x 8 D.L.Williamson,O.Ozturk,R.Wei,P.J.Wilbur,Surf.Coat.Ž.Technol.65199415.()M.K.Lei et al.r Surface and Coatings Technology1312000317᎐325325w xŽ.9M.K.Lei,Z.L.Zhang,J.Vac.Sci.Technol.A1319952986. w xŽ10M.K.Lei,D.Y.Wang,Z.L.Zhang,Vac.Sci.Technol.Zhen-.Ž.kong Kexue Yu Jishu Xuebao161996299.w xŽ.11M.K.Lei,Z.L.Zhang,J.Vac.Sci.Technol.A161998524. w xŽ.12M.K.Lei,Z.L.Zhang,Surf.Coat.Technol.91199725.w xŽ.13M.K.Lei,Z.L.Zhang,J.Vac.Sci.Technol.A151997421. w x14M.K.Lei,P.Wang,Y.Huang,Z.W.Yu,L.J.Yuan,Z.L.Zhang,Ž.Wear2091997301.w xŽ15M.K.Lei,Y.Huang,Y.H.Li,Z.L.Zhang,Tribology Mocaxue .Ž.Xuebao161997206.w xŽ.16M.K.Lei,Z.L.Zhang,J.Mater.Sci.Lett.1619971567.w xŽ. 17M.K.Lei,Y.Huang,Z.L.Zhang,J.Mater.Sci.Lett.171998 1165.w xŽ. 18M.K.Lei,X.M.Zhu,Z.L.Zhang,J.Mater.Sci.Lett.181999 1537.w xŽ.19M.K.Lei,J.Mater.Sci.3419995975.w xŽ. 20K.Ichii,K.Fujimara,T.Takase,Rep.Kansai.Univ.271986 135.w xŽ.21N.Yasumaru,K.Mamachi,J.Jpn.Inst.Metals501986362. w x22 A.Leyland,D.B.Lewis,P.R.Stevenson,A.Matthews,Surf.Ž.Coat.Technol.621993608.w x23T.Czerwiec,H.Michel,E.Bergmann,Surf.Coat.Technol.Ž.108r1091998182.w x24Y.K.Wang,X.Y.Li,X.L.Zhang,H.M.Han,Surf.Coat.Tech-Ž.nol.811996159.w xŽ.25 E.Kamijo,J.Jpn.Soc.Powder Powder Metall.441997721. w x26R.Tobe,A.Sekiguchi,M.Sasaki,O.Okada,N.Hosokawa,Ž.Thin Solid Films281r2821996155.w xŽ.27R.A.Kant,B.D.Sartwell,Mater.Sci.Eng.901987357.w x28K.Hayashi,K.Sugiyama,K.Fukutani,K.Kittaka,Mater.Sci.Ž.Eng.A1151989349.w x29J.R.Conrad,R.A.Dodd,S.Han,M.Madapura,J.Scheuer,K.Ž.Sridharan,F.J.Worzala,J.Vac.Sci.Technol.A819903146. w x30S.M.Malik,R.P.Fetherston,J.R.Conrad,J.Vac.Sci.Technol.Ž.A1519972875.w xŽ.31I.-H.Kim,S.-H.Kim,J.Vac.Sci.Technol.A1319952184.。

锂电池人造石墨负极材料英文

锂电池人造石墨负极材料英文Lithium-ion batteries are widely used in various electronic devices and are considered to be one of the most efficient rechargeable battery technologies available today. The graphite anode material used in these batteries plays a crucial role in their performance and overall efficiency.In this response, I will provide a detailed explanation of the various aspects of artificial graphite as a negative electrode material for lithium-ion batteries.Firstly, let's discuss the importance of artificial graphite as a negative electrode material. The negative electrode, also known as the anode, is responsible for storing and releasing lithium ions during the charge and discharge cycles of the battery. Artificial graphite offers several advantages over other materials, such as highenergy density, excellent cycling stability, and low cost. These properties make it an ideal choice for commercial lithium-ion batteries.Secondly, let's delve into the manufacturing process of artificial graphite. The production of artificial graphite involves the carbonization of various carbon-rich precursors, such as petroleum coke or coal tar pitch, at high temperatures. This process transforms the raw materials into a highly ordered and crystalline structure, which provides the desired electrochemical properties required for battery applications. The resulting graphite particles are then further processed to achieve the desired particle size and shape.Moving on, let's explore the electrochemical performance of artificial graphite as a negative electrode material. The unique structure of artificial graphite allows for the intercalation and de-intercalation oflithium ions during the charge and discharge cycles. This reversible process enables the battery to store and release electrical energy efficiently. Moreover, artificial graphite exhibits a stable voltage profile, which ensures a consistent and reliable performance over multiple cycles. These characteristics make it an excellent choice for high-capacity and long-lasting lithium-ion batteries.Furthermore, it is worth mentioning the impact of artificial graphite on the overall safety of lithium-ion batteries. One of the major concerns with lithium-ion batteries is the possibility of thermal runaway and subsequent fire or explosion. Artificial graphite, due to its stable structure and low reactivity, minimizes the risk of thermal runaway and enhances the overall safety of the battery system. This is a crucial aspect, especially in applications where safety is of utmost importance, such as electric vehicles.Another important consideration is the environmental impact of artificial graphite production. While the production process does involve high-temperature carbonization, it is worth noting that the carbon precursors used are often derived from petroleum coke or coal tar pitch, which are by-products of the oil and coal industries. Therefore, the utilization of these precursors helps in reducing waste and utilizing available resources efficiently. Additionally, the long lifespan and recyclability of lithium-ion batteries contribute to theoverall sustainability of artificial graphite as a negative electrode material.Lastly, let's touch upon the ongoing research and development in the field of artificial graphite forlithium-ion batteries. Scientists and engineers are continuously striving to improve the performance and efficiency of lithium-ion batteries by exploring new materials, modifying existing ones, and optimizing manufacturing processes. This relentless pursuit of innovation aims to enhance the energy density, charging speed, and overall lifespan of lithium-ion batteries, ultimately leading to a more sustainable and reliable energy storage solution.In conclusion, artificial graphite as a negative electrode material for lithium-ion batteries offers numerous advantages in terms of performance, cost-effectiveness, safety, and environmental sustainability.Its unique electrochemical properties, coupled with ongoing research and development efforts, make it a key component in the advancement of rechargeable battery technologies. Aswe continue to rely on portable electronic devices and transition towards a greener future, the significance of artificial graphite in lithium-ion batteries cannot be overstated.。

循环伏安法英文

循环伏安法英文Cyclic Voltammetry: A Comprehensive OverviewIntroduction:Cyclic Voltammetry (CV) is an electrochemical technique widely used to investigate the redox properties of electroactive species in a solution. It provides valuable information about the thermodynamics, kinetics, and mechanisms of redox reactions, making it an essential tool in various fields such as analytical chemistry, electrochemistry, and materials science. This article aims to provide a comprehensive overview of Cyclic Voltammetry, discussing its principles, experimental setup, data interpretation, and applications.Principles of Cyclic Voltammetry:Cyclic Voltammetry involves the application of a triangular potential waveform to an electrochemical cell, typically consisting of a working electrode, a reference electrode, and a counter electrode. The potential is swept linearly between a negative and positive potential limit (known as the scan range) at a constant scan rate. The resulting current response is recorded as a function of applied potential.Experimental Setup:A typical experimental setup for Cyclic Voltammetry includes a potentiostat, which controls the potential at the working electrode, and an electrochemical cell equipped with the necessary electrodes. The working electrode is typically made of a conductive material such as glassy carbon, platinum, or gold. The reference electrode provides a stable reference potential against which the potential at the working electrode is measured. The counter electrode completes the electrical circuit and allows the flow of current. The electrochemical cell also contains a supporting electrolyte, which enhances the conductivity of the solution.Data Interpretation:The resulting current-potential plot obtained from Cyclic Voltammetry is called a voltammogram. It consists of two curves - a forward sweep and a reverse sweep. The peak currents observed in the voltammogram correspond to the redox processes occurring at the working electrode. The peak potential (Ep) indicates the potential at which the redox reaction occurs. The peak current (Ip) is proportional to the concentration of the electroactive species and the scan rate. The shape and position of the peaks can provide information about the nature of the redox reaction, including the number of electrons involved, the reversibility of the reaction, and any subsequent chemical reactions.Applications of Cyclic Voltammetry:Cyclic Voltammetry finds applications in various fields:1. Electrochemical Sensors: It is used to determine the concentration of analytes in solution, making it suitable for sensing applications in environmental monitoring, food analysis, and clinical diagnostics.2. Energy Storage and Conversion: Cyclic Voltammetry helps characterize the electrochemical behavior of batteries, supercapacitors, and fuel cells, aiding in the design and optimization of energy storage and conversion devices.3. Corrosion Studies: It allows the investigation of corrosion processes by determining the corrosion potential and rate of materials exposed to corrosive environments.4. Determination of Mechanisms: Cyclic Voltammetry elucidates the reaction mechanisms of electroactive compounds, providing insights into their redox behavior and electron transfer processes.5. Material Characterization: It assists in the study of materials such as catalysts, nanomaterials, and thin films by analyzing their electrochemical properties.Conclusion:Cyclic Voltammetry is a powerful technique for exploring the redox properties of electroactive species. Its ability to provide quantitative information about thethermodynamics, kinetics, and mechanisms of redox reactions makes it an indispensable tool in various scientific disciplines. By understanding the principles, experimental setup, data interpretation, and applications of Cyclic Voltammetry, researchers and scientists can effectively harness its potential for their specific research interests and practical needs.。

质子交换膜燃料电池英语作文

质子交换膜燃料电池英语作文Proton Exchange Membrane Fuel CellsProton exchange membrane fuel cells (PEMFCs) are a type of electrochemical device that convert the chemical energy of hydrogen and oxygen into electrical energy through an electrochemical reaction. These fuel cells are known for their high efficiency, low operating temperatures, and potential for a wide range of applications, making them a promising technology in the pursuit of sustainable energy solutions.At the heart of a PEMFC is the proton exchange membrane, a thin, polymer-based material that acts as a barrier between the hydrogen and oxygen gases. This membrane is designed to selectively allow the passage of positively charged hydrogen ions (protons) while preventing the direct mixing of the reactant gases. This separation of the reactants is crucial, as it ensures that the desired electrochemical reaction takes place, generating electricity and water as the only byproduct.The basic operating principle of a PEMFC is as follows: Hydrogen gas is fed into the anode side of the fuel cell, where it undergoes anoxidation reaction, splitting into protons and electrons. The protons then pass through the proton exchange membrane to the cathode side, while the electrons are forced to travel through an external circuit, generating an electric current. On the cathode side, oxygen gas is fed, and the protons, electrons, and oxygen combine in a reduction reaction, producing water as the only byproduct.One of the key advantages of PEMFCs is their relatively low operating temperature, typically ranging from 60 to 80 degrees Celsius (140 to 176 degrees Fahrenheit). This allows for faster start-up times and more efficient thermal management compared to other fuel cell types, such as solid oxide fuel cells, which operate at much higher temperatures. The low operating temperature also contributes to the overall simplicity and compactness of PEMFC systems, making them suitable for a wide range of applications, including transportation, stationary power generation, and portable electronics.Another important feature of PEMFCs is their high power density, which is the amount of power generated per unit volume or weight of the fuel cell. This high power density, combined with their scalability, makes PEMFCs an attractive option for applications where space and weight are at a premium, such as in vehicles and portable devices.The development of PEMFCs has been driven by ongoing research and technological advancements in several key areas. One of the primary areas of focus is the improvement of the proton exchange membrane itself, with researchers working to develop materials that are more durable, efficient, and cost-effective. Advances in catalyst design and manufacturing techniques have also played a crucial role in enhancing the performance and reducing the cost of PEMFCs.In addition to the technical advancements, the widespread adoption of PEMFCs is also dependent on the availability and cost of hydrogen fuel. The development of reliable and cost-effective hydrogen production, storage, and distribution infrastructure is a critical factor in the broader deployment of PEMFC technology.Despite the promising potential of PEMFCs, there are still several challenges that need to be addressed before they can achieve widespread commercial success. These challenges include improving the durability and lifetime of fuel cell components, reducing manufacturing costs, and addressing the issues related to hydrogen infrastructure development.Nonetheless, the continued research and development efforts in the field of PEMFCs, coupled with the growing global emphasis on sustainable energy solutions, suggest a promising future for this technology. As PEMFCs continue to evolve and become more cost-competitive, they are poised to play a significant role in the transition towards a cleaner and more efficient energy landscape.。

氢能英文材料

氢能英文材料如下：Hydrogen as an Energy SourceHydrogen is considered a promising alternative energy source due to its clean and efficient properties. Unlike fossil fuels, hydrogen produces only water vapor when burned, making it a clean fuel option. Additionally, hydrogen has a high energy density, meaning that it contains more energy per unit of weight than gasoline or diesel fuel.One of the most attractive features of hydrogen energy is its versatility. Hydrogen can be used for a variety of applications, including fueling cars, buses, and trucks, generating electricity, and heating buildings. In fact, many automakers have already developed hydrogen fuel cell vehicles that produce zero emissions, making them an ideal solution for reducing greenhouse gas emissions in the transportation sector.Another advantage of hydrogen energy is its potential for sustainable production. While hydrogen can be produced from natural gas, which is a non-renewable resource, it can also be produced from renewable energy sources such as solar and wind power. This means that hydrogen has the potential to be a truly sustainable energy source that can help reduce our reliance on fossil fuels.However, there are still some challenges that must be overcome before hydrogen energy can become a mainstream energy source. One of the biggest challenges is the cost of producing and storing hydrogen. Currently, producing hydrogen is more expensive than producing gasoline or diesel, largely due to the energy required to split water molecules into hydrogen and oxygen. Additionally, storage of hydrogen can be difficult due to its low density, which requires large tanks or highly compressed gas cylinders.Despite these challenges, hydrogen energy remains a promising alternative to fossil fuels. As technology improves and economies of scale are achieved, the cost of hydrogen production and storage is expected to come down significantly, making it a more viable energy option for a wide range of applications.In conclusion, hydrogen energy offers a clean, efficient, and versatile alternative to fossil fuels. While there are still some barriers to overcome, hydrogen has the potential to play an important role in a sustainable energy future.。

电容去离子技术实验英语

电容去离子技术实验英语Electric Capacitive Deionization Technology ExperimentWater is an essential resource for life, but not all water is safe for consumption. One of the major challenges in providing clean drinking water is the presence of ionic contaminants. These contaminants are usually in the form of dissolved salts, minerals and other substances that make water impure.One method of removing these ions from water is by using Electr Capacitive Deionization (CDI) technology. This is an eco-friendly and efficient alternative to traditional water purification systems. In this article, we will provide a detailed description of the CDI process.Step 1: Preparing the materialsTo conduct the CDI experiment, we will need a conductivity meter, a voltage source, two electrodes made of activated carbon, and deionized water. The electrodes are cylindrical in shape and are made of a porous material capable of absorbing large amounts of ions.Step 2: Setting up the experimentThe two electrodes are placed parallel to each other in a container that is filled with deionized water. The distance between the electrodes is usually too small to allow the passage of large ions. A positive electrode and a negative electrode are connected to a voltage source.Step 3: Applying voltageWhen voltage is applied to the electrodes, a charge imbalance occurs between the electrodes resulting in theremoval of ions. The positive electrode attracts negative ions, while the negative electrode attracts positive ions.Step 4: Ion removalIons are removed as they pass through the porous electrodes and accumulate on their surfaces. The direct removal of ions reduces the electrical conductivity of the water. During this process, water molecules pass through the electrodes, thus allowing for the continuous desalination of water.Step 5: Monitoring the processThe conductivity meter is used to monitor theconductivity of the water at different stages of the process. The conductivity value provides information about the levelof impurities in the water.Step 6: Analyzing the resultsThe degree of deionization is calculated by comparingthe initial and final conductivity values. The lower the conductivity value, the higher the degree of deionization.In conclusion, the CDI technology experiment is an efficient and eco-friendly method of removing ions from water. The technology is useful in providing access to safe drinking water in areas where water sources are contaminated withionic impurities. With further advancements in the technology, it is hoped that the CDI process will become more widely used as a reliable source of clean drinking water.。

360教育集团：SAT2生物专业词汇 Chapter 1-1

官网：360教育集团：SAT2生物专业词汇Chapter 1-1据360教育集团()介绍：下面360教育集团为大家搜集整理的是关于SAT2生物词汇中字母A打头的词汇。

记忆SAT2生物词汇对于大家更快更好的备考SAT2生物考试有非常重大的影响，下面跟随360教育集团就一起来看看这些关于生物的SAT2词汇详细内容吧。

abiotic (无生命的)Nonliving materials in the environment—such as elements, sunlight, and soil—that influence and are influenced by living (biotic) entities on the planet.Acetylcholine(乙酰胆素): 运动神经释于一种化学物质,与其接受体结合后，能产生足够的电位变化来引起肌肉运动A neurotransmitter released from the axons of nerve cells to excite an action potential or trigger a muscle to contract.active immunity(主动免疫)Protective immunity to a disease in which the individual produces antibodies as a result of previous exposures to the antigen.Acids(酸)Hydrogen ion (H+) donors. Acids are very important in the chemical reactions of life because they are highly reactive. Acids have pH values below 7. They are the opposite of bases.actin (肌动蛋白)Protein filaments that, along with myosin, allow muscles to contract.。

ECR强流离子源

136Ⅱ. 加速器物理和技术CNIC-01638/12CNNC-0003用于质子直线加速器的强流ECR离子源*崔保群李立强包轶文蒋渭生王荣文中国原子能科学研究院北京，102413摘要：介绍了正在研制的一台强流ECR离子源。

它的目标是用于加速器驱动的次临界系统 (ADS)。

两种结构的离子源均获得了较好的结果。

在30 keV能量下，氢离子最大束流达到100 mA，质子比好于85%，引出束流密度最高可达340 mA/cm2。

初步测定的发射度约为0.11 πmm·mrad。

已通过了100 h的连续运行考验。

关键词：ECR ADS 质子比发射度引言中国原子能科学研究院正在进行加速器驱动的次临界系统 (Accelerator Driven Sub-critical System) 的研究。

其质子直线加速器的第一个重要部件就是强流离子源。

为了与RFQ加速段匹配，质子能量需75 keV，连续束流强大于50 mA，质子比高于85%，归一化均方根发射度ε≤0.2 πmm·mrad，n·rms能上千小时地连续稳定运行。

这些要求对离子源研究工作是一个重大挑战。

微波激励的电子回旋共振型 (ECR型) 离子源由于没有灯丝阴极，寿命可以大大延长。

另外，它的效率高，束流品质好，故国际上许多实验室都选用这种离子源[1～4]。

我们从1999年开始了ECR离子源的研制，经过多次改进，已经达到了第一阶段目标，即在30 keV能量下，引出束流大于50 mA，并通过了100 h连续运行的考验。

1 实验装置ECR离子源是将微波功率以适当的方式馈入一个放电腔，腔内有一个* 本项目得到国家自然科学重点基金及国家重点基础研究(973)计划的资助。

Ⅱ. 加速器物理和技术137与微波电场相垂直的恒定磁场，当磁场强度达到电子回旋共振的条件时，腔中的电子将从微波获得能量并与周围的气体碰撞产生电离，形成等离子体。

用高压电场从放电腔的一个引出孔将离子引出而形成离子束。

大环多胺

New1H-Pyrazole-Containing Polyamine Receptors Able ToComplex L-Glutamate in Water at Physiological pH ValuesCarlos Miranda,†Francisco Escartı´,‡Laurent Lamarque,†Marı´a J.R.Yunta,§Pilar Navarro,*,†Enrique Garcı´a-Espan˜a,*,‡and M.Luisa Jimeno†Contribution from the Instituto de Quı´mica Me´dica,Centro de Quı´mica Orga´nica Manuel Lora Tamayo,CSIC,C/Juan de la Cier V a3,28006Madrid,Spain,Departamento de Quı´mica Inorga´nica,Facultad de Quı´mica,Uni V ersidad de Valencia,c/Doctor Moliner50, 46100Burjassot(Valencia),Spain,and Departamento de Quı´mica Orga´nica,Facultad deQuı´mica,Uni V ersidad Complutense de Madrid,A V plutense s/n,28040Madrid,SpainReceived April16,2003;E-mail:enrique.garcia-es@uv.esAbstract:The interaction of the pyrazole-containing macrocyclic receptors3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene1[L1],13,26-dibenzyl-3,6,9,12,13,16,-19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene2[L2],3,9,12,13,16,22,-25,26-octaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene3[L3],6,19-dibenzyl-3,6,9,12,13,-16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene4[L4],6,19-diphenethyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene5[L5],and 6,19-dioctyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetra-ene6[L6]with L-glutamate in aqueous solution has been studied by potentiometric techniques.The synthesis of receptors3-6[L3-L6]is described for the first time.The potentiometric results show that4[L4]containing benzyl groups in the central nitrogens of the polyamine side chains is the receptor displaying the larger interaction at pH7.4(K eff)2.04×104).The presence of phenethyl5[L5]or octyl groups6[L6]instead of benzyl groups4[L4]in the central nitrogens of the chains produces a drastic decrease in the stability[K eff )3.51×102(5),K eff)3.64×102(6)].The studies show the relevance of the central polyaminic nitrogen in the interaction with glutamate.1[L1]and2[L2]with secondary nitrogens in this position present significantly larger interactions than3[L3],which lacks an amino group in the center of the chains.The NMR and modeling studies suggest the important contribution of hydrogen bonding andπ-cation interaction to adduct formation.IntroductionThe search for the L-glutamate receptor field has been andcontinues to be in a state of almost explosive development.1 L-Glutamate(Glu)is thought to be the predominant excitatory transmitter in the central nervous system(CNS)acting at a rangeof excitatory amino acid receptors.It is well-known that it playsa vital role mediating a great part of the synaptic transmission.2However,there is an increasing amount of experimentalevidence that metabolic defects and glutamatergic abnormalitiescan exacerbate or induce glutamate-mediated excitotoxic damageand consequently neurological disorders.3,4Overactivation ofionotropic(NMDA,AMPA,and Kainate)receptors(iGluRs)by Glu yields an excessive Ca2+influx that produces irreversible loss of neurons of specific areas of the brain.5There is much evidence that these processes induce,at least in part,neuro-degenerative illnesses such as Parkinson,Alzheimer,Huntington, AIDS,dementia,and amyotrophic lateral sclerosis(ALS).6In particular,ALS is one of the neurodegenerative disorders for which there is more evidence that excitotoxicity due to an increase in Glu concentration may contribute to the pathology of the disease.7Memantine,a drug able to antagonize the pathological effects of sustained,but relatively small,increases in extracellular glutamate concentration,has been recently received for the treatment of Alzheimer disease.8However,there is not an effective treatment for ALS.Therefore,the preparation of adequately functionalized synthetic receptors for L-glutamate seems to be an important target in finding new routes for controlling abnormal excitatory processes.However,effective recognition in water of aminocarboxylic acids is not an easy task due to its zwitterionic character at physiological pH values and to the strong competition that it finds in its own solvent.9†Centro de Quı´mica Orga´nica Manuel Lora Tamayo.‡Universidad de Valencia.§Universidad Complutense de Madrid.(1)Jane,D.E.In Medicinal Chemistry into the Millenium;Campbell,M.M.,Blagbrough,I.S.,Eds.;Royal Society of Chemistry:Cambridge,2001;pp67-84.(2)(a)Standaert,D.G.;Young,A.B.In The Pharmacological Basis ofTherapeutics;Hardman,J.G.,Goodman Gilman,A.,Limbird,L.E.,Eds.;McGraw-Hill:New York,1996;Chapter22,p503.(b)Fletcher,E.J.;Loge,D.In An Introduction to Neurotransmission in Health and Disease;Riederer,P.,Kopp,N.,Pearson,J.,Eds.;Oxford University Press:New York,1990;Chapter7,p79.(3)Michaelis,E.K.Prog.Neurobiol.1998,54,369-415.(4)Olney,J.W.Science1969,164,719-721.(5)Green,J.G.;Greenamyre,J.T.Prog.Neurobiol.1996,48,613-63.(6)Bra¨un-Osborne,H.;Egebjerg,J.;Nielsen,E.O.;Madsen,U.;Krogsgaard-Larsen,P.J.Med.Chem.2000,43,2609-2645and references therein.(7)(a)Shaw,P.J.;Ince,P.G.J.Neurol.1997,244(Suppl2),S3-S14.(b)Plaitakis,A.;Fesdjian,C.O.;Shashidharan,S Drugs1996,5,437-456.(8)Frantz,A.;Smith,A.Nat.Re V.Drug Dico V ery2003,2,9.Published on Web12/30/200310.1021/ja035671m CCC:$27.50©2004American Chemical Society J.AM.CHEM.SOC.2004,126,823-8339823There are many types of receptors able to interact with carboxylic acids and amino acids in organic solvents,10-13yielding selective complexation in some instances.However,the number of reported receptors of glutamate in aqueous solution is very scarce.In this sense,one of the few reports concerns an optical sensor based on a Zn(II)complex of a 2,2′:6′,2′′-terpyridine derivative in which L -aspartate and L -glutamate were efficiently bound as axial ligands (K s )104-105M -1)in 50/50water/methanol mixtures.14Among the receptors employed for carboxylic acid recogni-tion,the polyamine macrocycles I -IV in Chart 1are of particular relevance to this work.In a seminal paper,Lehn et al.15showed that saturated polyamines I and II could exert chain-length discrimination between different R ,ω-dicarboxylic acids as a function of the number of methylene groups between the two triamine units of the receptor.Such compounds were also able to interact with a glutamic acid derivative which has the ammonium group protected with an acyl moiety.15,16Compounds III and IV reported by Gotor and Lehn interact in their protonated forms in aqueous solution with protected N -acetyl-L -glutamate and N -acetyl-D -glutamate,showing a higher stability for the interaction with the D -isomer.17In both reports,the interaction with protected N -acetyl-L -glutamate at physiological pH yields constants of ca.3logarithmic units.Recently,we have shown that 1H -pyrazole-containing mac-rocycles present desirable properties for the binding of dopam-ine.18These polyaza macrocycles,apart from having a highpositive charge at neutral pH values,can form hydrogen bonds not only through the ammonium or amine groups but also through the pyrazole nitrogens that can behave as hydrogen bond donors or acceptors.In fact,Elguero et al.19have recently shown the ability of the pyrazole rings to form hydrogen bonds with carboxylic and carboxylate functions.These features can be used to recognize the functionalities of glutamic acid,the carboxylic and/or carboxylate functions and the ammonium group.Apart from this,the introduction of aromatic donor groups appropriately arranged within the macrocyclic framework or appended to it through arms of adequate length may contribute to the recognition event through π-cation interactions with the ammonium group of L -glutamate.π-Cation interactions are a key feature in many enzymatic centers,a classical example being acetylcholine esterase.20The role of such an interaction in abiotic systems was very well illustrated several years ago in a seminal work carried out by Dougherty and Stauffer.21Since then,many other examples have been reported both in biotic and in abiotic systems.22Taking into account all of these considerations,here we report on the ability of receptors 1[L 1]-6[L 6](Chart 2)to interact with L -glutamic acid.These receptors display structures which differ from one another in only one feature,which helps to obtain clear-cut relations between structure and interaction(9)Rebek,J.,Jr.;Askew,B.;Nemeth,D.;Parris,K.J.Am.Chem.Soc.1987,109,2432-2434.(10)Seel,C.;de Mendoza,J.In Comprehensi V e Supramolecular Chemistry ;Vogtle,F.,Ed.;Elsevier Science:New York,1996;Vol.2,p 519.(11)(a)Sessler,J.L.;Sanson,P.I.;Andrievesky,A.;Kral,V.In SupramolecularChemistry of Anions ;Bianchi,A.,Bowman-James,K.,Garcı´a-Espan ˜a,E.,Eds.;John Wiley &Sons:New York,1997;Chapter 10,pp 369-375.(b)Sessler,J.L.;Andrievsky,A.;Kra ´l,V.;Lynch,V.J.Am.Chem.Soc.1997,119,9385-9392.(12)Fitzmaurice,R.J.;Kyne,G.M.;Douheret,D.;Kilburn,J.D.J.Chem.Soc.,Perkin Trans.12002,7,841-864and references therein.(13)Rossi,S.;Kyne,G.M.;Turner,D.L.;Wells,N.J.;Kilburn,J.D.Angew.Chem.,Int.Ed.2002,41,4233-4236.(14)Aı¨t-Haddou,H.;Wiskur,S.L.;Lynch,V.M.;Anslyn,E.V.J.Am.Chem.Soc.2001,123,11296-11297.(15)Hosseini,M.W.;Lehn,J.-M.J.Am.Chem.Soc.1982,104,3525-3527.(16)(a)Hosseini,M.W.;Lehn,J.-M.Hel V .Chim.Acta 1986,69,587-603.(b)Heyer,D.;Lehn,J.-M.Tetrahedron Lett.1986,27,5869-5872.(17)(a)Alfonso,I.;Dietrich,B.;Rebolledo,F.;Gotor,V.;Lehn,J.-M.Hel V .Chim.Acta 2001,84,280-295.(b)Alfonso,I.;Rebolledo,F.;Gotor,V.Chem.-Eur.J.2000,6,3331-3338.(18)Lamarque,L.;Navarro,P.;Miranda,C.;Ara ´n,V.J.;Ochoa,C.;Escartı´,F.;Garcı´a-Espan ˜a,E.;Latorre,J.;Luis,S.V.;Miravet,J.F.J.Am.Chem.Soc .2001,123,10560-10570.(19)Foces-Foces,C.;Echevarria,A.;Jagerovic,N.;Alkorta,I.;Elguero,J.;Langer,U.;Klein,O.;Minguet-Bonvehı´,H.-H.J.Am.Chem.Soc.2001,123,7898-7906.(20)Sussman,J.L.;Harel,M.;Frolow,F.;Oefner,C.;Goldman,A.;Toker,L.;Silman,I.Science 1991,253,872-879.(21)Dougherty,D.A.;Stauffer,D.A.Science 1990,250,1558-1560.(22)(a)Sutcliffe,M.J.;Smeeton,A.H.;Wo,Z.G.;Oswald,R.E.FaradayDiscuss.1998,111,259-272.(b)Kearney,P.C.;Mizoue,L.S.;Kumpf,R.A.;Forman,J.E.;McCurdy,A.;Dougherty,D.A.J.Am.Chem.Soc.1993,115,9907-9919.(c)Bra ¨uner-Osborne,H.;Egebjerg,J.;Nielsen,E.;Madsen,U.;Krogsgaard-Larsen,P.J.Med.Chem.2000,43,2609-2645.(d)Zacharias,N.;Dougherty,D.A.Trends Pharmacol.Sci.2002,23,281-287.(e)Hu,J.;Barbour,L.J.;Gokel,G.W.J.Am.Chem.Soc.2002,124,10940-10941.Chart 1.Some Receptors Employed for Dicarboxylic Acid and N -AcetylglutamateRecognitionChart 2.New 1H -Pyrazole-Containing Polyamine Receptors Able To Complex L -Glutamate inWaterA R T I C L E SMiranda et al.824J.AM.CHEM.SOC.9VOL.126,NO.3,2004strengths.1[L1]and2[L2]differ in the N-benzylation of the pyrazole moiety,and1[L1]and3[L3]differ in the presence in the center of the polyamine side chains of an amino group or of a methylene group.The receptors4[L4]and5[L5]present the central nitrogens of the chain N-functionalized with benzyl or phenethyl groups,and6[L6]has large hydrophobic octyl groups.Results and DiscussionSynthesis of3-6.Macrocycles3-6have been obtained following the procedure previously reported for the preparation of1and2.23The method includes a first dipodal(2+2) condensation of the1H-pyrazol-3,5-dicarbaldehyde7with the corresponding R,ω-diamine,followed by hydrogenation of the resulting Schiff base imine bonds.In the case of receptor3,the Schiff base formed by condensation with1,5-pentanediamine is a stable solid(8,mp208-210°C)which precipitated in68% yield from the reaction mixture.Further reduction with NaBH4 in absolute ethanol gave the expected tetraazamacrocycle3, which after crystallization from toluene was isolated as a pure compound(mp184-186°C).In the cases of receptors4-6, the precursor R,ω-diamines(11a-11c)(Scheme1B)were obtained,by using a procedure previously described for11a.24 This procedure is based on the previous protection of the primary amino groups of1,5-diamino-3-azapentane by treatment with phthalic anhydride,followed by alkylation of the secondary amino group of1,5-diphthalimido-3-azapentane9with benzyl, phenethyl,or octyl bromide.Finally,the phthalimido groups of the N-alkyl substituted intermediates10a-10c were removed by treatment with hydrazine to afford the desired amines11a-11c,which were obtained in moderate yield(54-63%).In contrast with the behavior previously observed in the synthesis of3,in the(2+2)dipodal condensations of7with 3-benzyl-,3-phenethyl-,and3-octyl-substituted3-aza-1,5-pentanediamine11a,11b,and11c,respectively,there was not precipitation of the expected Schiff bases(Scheme1A). Consequently,the reaction mixtures were directly reduced in situ with NaBH4to obtain the desired hexaamines4-6,which after being carefully purified by chromatography afforded purecolorless oils in51%,63%,and31%yield,respectively.The structures of all of these new cyclic polyamines have been established from the analytical and spectroscopic data(MS(ES+), 1H and13C NMR)of both the free ligands3-6and their corresponding hydrochloride salts[3‚4HCl,4‚6HCl,5‚6HCl, and6‚6HCl],which were obtained as stable solids following the same procedure previously reported18for1‚6HCl and2‚6HCl.As usually occurs for3,5-disubstituted1H-pyrazole deriva-tives,either the free ligands3-6or their hydrochlorides show very simple1H and13C NMR spectra,in which signals indicate that,because of the prototropic equilibrium of the pyrazole ring, all of these compounds present average4-fold symmetry on the NMR scale.The quaternary C3and C5carbons appear together,and the pairs of methylene carbons C6,C7,and C8are magnetically equivalent(see Experimental Section).In the13C NMR spectra registered in CDCl3solution, significant differences can be observed between ligand3,without an amino group in the center of the side chain,and the N-substituted ligands4-6.In3,the C3,5signal appears as a broad singlet.However,in4-6,it almost disappears within the baseline of the spectra,and the methylene carbon atoms C6and C8experience a significant broadening.Additionally,a remark-able line-broadening is also observed in the C1′carbon signals belonging to the phenethyl and octyl groups of L5and L6, respectively.All of these data suggest that as the N-substituents located in the middle of the side chains of4-6are larger,the dynamic exchange rate of the pyrazole prototropic equilibrium is gradually lower,probably due to a relation between proto-tropic and conformational equilibria.Acid-Base Behavior.To follow the complexation of L-glutamate(hereafter abbreviated as Glu2-)and its protonated forms(HGlu-,H2Glu,and H3Glu+)by the receptors L1-L6, the acid-base behavior of L-glutamate has to be revisited under the experimental conditions of this work,298K and0.15mol dm-3.The protonation constants obtained,included in the first column of Table1,agree with the literature25and show that the zwitterionic HGlu-species is the only species present in aqueous solution at physiological pH values(Scheme2and Figure S1of Supporting Information).Therefore,receptors for(23)Ara´n,V.J.;Kumar,M.;Molina,J.;Lamarque,L.;Navarro,P.;Garcı´a-Espan˜a,E.;Ramı´rez,J.A.;Luis,S.V.;Escuder,.Chem.1999, 64,6137-6146.(24)(a)Yuen Ng,C.;Motekaitis,R.J.;Martell,A.E.Inorg.Chem.1979,18,2982-2986.(b)Anelli,P.L.;Lunazzi,L.;Montanari,F.;Quici,.Chem.1984,49,4197-4203.Scheme1.Synthesis of the Pyrazole-Containing MacrocyclicReceptorsNew1H-Pyrazole-Containing Polyamine Receptors A R T I C L E SJ.AM.CHEM.SOC.9VOL.126,NO.3,2004825glutamate recognition able to address both the negative charges of the carboxylate groups and the positive charge of ammonium are highly relevant.The protonation constants of L 3-L 6are included in Table 1,together with those we have previously reported for receptors L 1and L 2.23A comparison of the constants of L 4-L 6with those of the nonfunctionalized receptor L 1shows a reduced basicity of the receptors L 4-L 6with tertiary nitrogens at the middle of the polyamine bridges.Such a reduction in basicity prevented the potentiometric detection of the last protonation for these ligands in aqueous solution.A similar reduction in basicity was previously reported for the macrocycle with the N -benzylated pyrazole spacers (L 2).23These diminished basicities are related to the lower probability of the tertiary nitrogens for stabilizing the positive charges through hydrogen bond formation either with adjacent nonprotonated amino groups of the molecule or with water molecules.Also,the increase in the hydrophobicity of these molecules will contribute to their lower basicity.The stepwise basicity constants are relatively high for the first four protonation steps,which is attributable to the fact that these protons can bind to the nitrogen atoms adjacent to the pyrazole groups leaving the central nitrogen free,the electrostatic repulsions between them being therefore of little significance.The remaining protonation steps will occur in the central nitrogen atom,which will produce an important increase in the electrostatic repulsion in the molecule and therefore a reduction in basicity.As stated above,the tertiary nitrogen atoms present in L 4-L 6will also contribute to this diminished basicity.To analyze the interaction with glutamic acid,it is important to know the protonation degree of the ligands at physiological pH values.In Table 2,we have calculated the percentages ofthe different protonated species existing in solution at pH 7.4for receptors L 1-L 6.As can be seen,except for the receptor with the pentamethylenic chains L 3in which the tetraprotonated species prevails,all of the other systems show that the di-and triprotonated species prevail,although to different extents.Interaction with Glutamate.The stepwise constants for the interaction of the receptors L 1-L 6with glutamate are shown in Table 3,and selected distribution diagrams are plotted in Figure 1A -C.All of the studied receptors interact with glutamate forming adduct species with protonation degrees (j )which vary between 8and 0depending on the system (see Table 3).The stepwise constants have been derived from the overall association constants (L +Glu 2-+j H +)H j LGlu (j -2)+,log j )provided by the fitting of the pH-metric titration curves.This takes into account the basicities of the receptors and glutamate (vide supra)and the pH range in which a given species prevails in solution.In this respect,except below pH ca.4and above pH 9,HGlu -can be chosen as the protonated form of glutamate involved in the formation of the different adducts.Below pH 4,the participation of H 2Glu in the equilibria has also to be considered (entries 9and 10in Table 3).For instance,the formation of the H 6LGlu 4+species can proceed through the equilibria HGlu -+H 5L 5+)H 6LGlu 4+(entry 8,Table 3),and H 2Glu +H 4L 4+)H 6LGlu 4(entry 9Table 3),with percentages of participation that depend on pH.One of the effects of the interaction is to render somewhat more basic the receptor,and somewhat more acidic glutamic acid,facilitating the attraction between op-positely charged partners.A first inspection of Table 3and of the diagrams A,B,and C in Figure 1shows that the interaction strengths differ markedly from one system to another depending on the structural features of the receptors involved.L 4is the receptor that presents the highest capacity for interacting with glutamate throughout all of the pH range explored.It must also be remarked that there are not clear-cut trends in the values of the stepwise constants as a function of the protonation degree of the receptors.This suggests that charge -charge attractions do not play the most(25)(a)Martell,E.;Smith,R.M.Critical Stability Constants ;Plenum:NewYork,1975.(b)Motekaitis,R.J.NIST Critically Selected Stability Constants of Metal Complexes Database ;NIST Standard Reference Database,version 4,1997.Table 1.Protonation Constants of Glutamic Acid and Receptors L 1-L 6Determined in NaCl 0.15mol dm -3at 298.1KreactionGluL 1aL 2aL 3bL 4L 5L 6L +H )L H c 9.574(2)d 9.74(2)8.90(3)9.56(1)9.25(3)9.49(4)9.34(5)L H +H )L H 2 4.165(3)8.86(2)8.27(2)8.939(7)8.38(3)8.11(5)8.13(5)L H 2+H )L H 3 2.18(2)7.96(2) 6.62(3)8.02(1) 6.89(5)7.17(6)7.46(7)L H 3+H )L H 4 6.83(2) 5.85(4)7.63(1) 6.32(5) 6.35(6) 5.97(8)L H 4+H )L H 5 4.57(3) 3.37(4) 2.72(8) 2.84(9) 3.23(9)L H 5+H )L H 6 3.18(3) 2.27(6)∑log K H n L41.135.334.233.634.034.1aTaken from ref 23.b These data were previously cited in a short communication (ref 26).c Charges omitted for clarity.d Values in parentheses are the standard deviations in the last significant figure.Scheme 2.L -Glutamate Acid -BaseBehaviorTable 2.Percentages of the Different Protonated Species at pH 7.4H 1L aH 2LH 3LH 4LL 11186417L 21077130L 3083458L 4083458L 51154323L 6842482aCharges omitted for clarity.A R T I C L E SMiranda et al.826J.AM.CHEM.SOC.9VOL.126,NO.3,2004outstanding role and that other forces contribute very importantly to these processes.26However,in systems such as these,which present overlapping equilibria,it is convenient to use conditional constants because they provide a clearer picture of the selectivity trends.27These constants are defined as the quotient between the overall amounts of complexed species and those of free receptor and substrate at a given pH[eq1].In Figure2are presented the logarithms of the effective constants versus pH for all of the studied systems.Receptors L1and L2with a nonfunctionalized secondary amino group in the side chains display opposite trend from all other receptors. While the stability of the L1and L2adducts tends to increase with pH,the other ligands show a decreasing interaction. Additionally,L1and L2present a close interaction over the entire pH range under study.The tetraaminic macrocycle L3is a better(26)Escartı´,F.;Miranda,C.;Lamarque,L.;Latorre,J.;Garcı´a-Espan˜a,E.;Kumar,M.;Ara´n,V.J.;Navarro,mun.2002,9,936-937.(27)(a)Bianchi,A.;Garcı´a-Espan˜a,c.1999,12,1725-1732.(b)Aguilar,J.A.;Celda,B.;Garcı´a-Espan˜a,E.;Luis,S.V.;Martı´nez,M.;Ramı´rez,J.A.;Soriano,C.;Tejero,B.J.Chem.Soc.,Perkin Trans.22000, 7,1323-1328.Table3.Stability Constants for the Interaction of L1-L6with the Different Protonated Forms of Glutamate(Glu) entry reaction a L1L2L3L4L5L6 1Glu+L)Glu L 3.30(2)b 4.11(1)2HGlu+L)HGlu L 3.65(2) 4.11(1) 3.68(2) 3.38(4) 3Glu+H L)HGlu L 3.89(2) 4.48(1) 3.96(2) 3.57(4) 4HGlu+H L)H2Glu L 3.49(2) 3.89(1) 2.37(4) 3.71(2)5HGlu+H2L)H3Glu L 3.44(2) 3.73(1) 2.34(3) 4.14(2) 2.46(4) 2.61(7) 6HGlu+H3L)H4Glu L 3.33(2) 3.56(2) 2.66(3) 4.65(2) 2.74(3) 2.55(7) 7HGlu+H4L)H5Glu L 3.02(2) 3.26(2) 2.58(3) 4.77(2) 2.87(3) 2.91(5) 8HGlu+H5L)H6Glu L 3.11(3) 3.54(2) 6.76(3) 4.96(3) 4.47(3) 9H2Glu+H4L)H6Glu L 2.54(3) 3.05(2) 3.88(2) 5.35(3) 3.66(4) 3.56(3) 10H2Glu+H5L)H7Glu L 2.61(6) 2.73(4) 5.51(3) 3.57(4) 3.22(8) 11H3Glu+H4L)H7Glu L 4.82(2) 4.12(9)a Charges omitted for clarity.b Values in parentheses are standard deviations in the last significantfigure.Figure1.Distribution diagrams for the systems(A)L1-glutamic acid, (B)L4-glutamic acid,and(C)L5-glutamicacid.Figure2.Representation of the variation of K cond(M-1)for the interaction of glutamic acid with(A)L1and L3,(B)L2,L4,L5,and L6.Initial concentrations of glutamate and receptors are10-3mol dm-3.Kcond)∑[(H i L)‚(H j Glu)]/{∑[H i L]∑[H j Glu]}(1)New1H-Pyrazole-Containing Polyamine Receptors A R T I C L E SJ.AM.CHEM.SOC.9VOL.126,NO.3,2004827receptor at acidic pH,but its interaction markedly decreases on raising the pH.These results strongly suggest the implication of the central nitrogens of the lateral polyamine chains in the stabilization of the adducts.Among the N-functionalized receptors,L4presents the largest interaction with glutamate.Interestingly enough,L5,which differs from L4only in having a phenethyl group instead of a benzyl one,presents much lower stability of its adducts.Since the basicity and thereby the protonation states that L4and L5 present with pH are very close,the reason for the larger stability of the L4adducts could reside on a better spatial disposition for formingπ-cation interactions with the ammonium group of the amino acid.In addition,as already pointed out,L4presents the highest affinity for glutamic acid in a wide pH range,being overcome only by L1and L2at pH values over9.This observation again supports the contribution ofπ-cation inter-actions in the system L4-glutamic because at these pH values the ammonium functionality will start to deprotonate(see Scheme2and Figure1B).Table4gathers the percentages of the species existing in equilibria at pH7.4together with the values of the conditional constant at this pH.In correspondence with Figure1A,1C and Figure S2(Supporting Information),it can be seen that for L1, L2,L5,and L6the prevailing species are[H2L‚HGlu]+and[H3L‚HGlu]2+(protonation degrees3and4,respectively),while for L3the main species are[H3L‚HGlu]+and[H4L‚HGlu]2+ (protonation degrees4and5,respectively).The most effective receptor at this pH would be L4which joins hydrogen bonding, charge-charge,andπ-cation contributions for the stabilization of the adducts.To check the selectivity of this receptor,we have also studied its interaction with L-aspartate,which is a competitor of L-glutamate in the biologic receptors.The conditional constant at pH7.4has a value of3.1logarithmic units for the system Asp-L4.Therefore,the selectivity of L4 for glutamate over aspartate(K cond(L4-glu)/K cond(L4-asp))will be of ca.15.It is interesting to remark that the affinity of L4 for zwiterionic L-glutamate at pH7.4is even larger than that displayed by receptors III and IV(Chart1)with the protected dianion N-acetyl-L-glutamate lacking the zwitterionic charac-teristics.Applying eq1and the stability constants reported in ref17,conditional constants at pH7.4of 3.24and 2.96 logarithmic units can be derived for the systems III-L-Glu and IV-L-Glu,respectively.Molecular Modeling Studies.Molecular mechanics-based methods involving docking studies have been used to study the binding orientations and affinities for the complexation of glutamate by L1-L6receptors.The quality of a computer simulation depends on two factors:accuracy of the force field that describes intra-and intermolecular interactions,and an adequate sampling of the conformational and configuration space of the system.28The additive AMBER force field is appropriate for describing the complexation processes of our compounds,as it is one of the best methods29in reproducing H-bonding and stacking stabiliza-tion energies.The experimental data show that at pH7.4,L1-L6exist in different protonation states.So,a theoretical study of the protonation of these ligands was done,including all of the species shown in5%or more abundance in the potentiometric measurements(Table4).In each case,the more favored positions of protons were calculated for mono-,di-,tri-,and tetraprotonated species.Molecular dynamics studies were performed to find the minimum energy conformations with simulated solvent effects.Molecular modeling studies were carried out using the AMBER30method implemented in the Hyperchem6.0pack-age,31modified by the inclusion of appropriate parameters. Where available,the parameters came from analogous ones used in the literature.32All others were developed following Koll-man33and Hopfinger34procedures.The equilibrium bond length and angle values came from experimental values of reasonable reference compounds.All of the compounds were constructed using standard geometry and standard bond lengths.To develop suitable parameters for NH‚‚‚N hydrogen bonding,ab initio calculations at the STO-3G level35were used to calculate atomic charges compatible with the AMBER force field charges,as they gave excellent results,and,at the same time,this method allows the study of aryl-amine interactions.In all cases,full geometry optimizations with the Polak-Ribiere algorithm were carried out,with no restraints.Ions are separated far away and well solvated in water due to the fact that water has a high dielectric constant and hydrogen bond network.Consequently,there is no need to use counteri-ons36in the modelization studies.In the absence of explicit solvent molecules,a distance-dependent dielectric factor quali-tatively simulates the presence of water,as it takes into account the fact that the intermolecular electrostatic interactions should vanish more rapidly with distance than in the gas phase.The same results can be obtained using a constant dielectric factor greater than1.We have chosen to use a distance-dependent dielectric constant( )4R ij)as this was the method used by Weiner et al.37to develop the AMBER force field.Table8 shows the theoretical differences in protonation energy(∆E p) of mono-,bi-,and triprotonated hexaamine ligands,for the (28)Urban,J.J.;Cronin,C.W.;Roberts,R.R.;Famini,G.R.J.Am.Chem.Soc.1997,119,12292-12299.(29)Hobza,P.;Kabelac,M.;Sponer,J.;Mejzlik,P.;Vondrasek,put.Chem.1997,18,1136-1150.(30)Cornell,W.D.;Cieplak,P.;Bayly,C.I.;Gould,I.R.;Merz,K.M.,Jr.;Ferguson,D.M.;Spelmeyer,D.C.;Fox,T.;Caldwell,J.W.;Kollman,P.A.J.Am.Chem.Soc.1995,117,5179-5197.(31)Hyperchem6.0(Hypercube Inc.).(32)(a)Fox,T.;Scanlan,T.S.;Kollman,P.A.J.Am.Chem.Soc.1997,119,11571-11577.(b)Grootenhuis,P.D.;Kollman,P.A.J.Am.Chem.Soc.1989,111,2152-2158.(c)Moyna,G.;Hernandez,G.;Williams,H.J.;Nachman,R.J.;Scott,put.Sci.1997,37,951-956.(d)Boden,C.D.J.;Patenden,put.-Aided Mol.Des.1999, 13,153-166.(33)/amber.(34)Hopfinger,A.J.;Pearlstein,put.Chem.1984,5,486-499.(35)Glennon,T.M.;Zheng,Y.-J.;Le Grand,S.M.;Shutzberg,B.A.;Merz,K.M.,put.Chem.1994,15,1019-1040.(36)Wang,J.;Kollman,P.A.J.Am.Chem.Soc.1998,120,11106-11114.Table4.Percentages of the Different Protonated Adducts[HGlu‚H j L](j-1)+,Overall Percentages of Complexation,andConditional Constants(K Cond)at pH7.4for the Interaction ofGlutamate(HGlu-)with Receptors L1-L6at Physiological pH[H n L‚HGlu]an)1n)2n)3n)4∑{[H n L‚HGlu]}K cond(M-1)L13272353 2.44×103L2947763 4.12×103L31101324 3.99×102L423737581 2.04×104L51010222 3.51×102L6121224 3.64×102a Charges omitted for clarity.A R T I C L E S Miranda et al. 828J.AM.CHEM.SOC.9VOL.126,NO.3,2004。

电芬顿法英文

电芬顿法英文Electrochemical Fenton Process: A Promising Approach for Wastewater TreatmentThe rapid industrialization and urbanization have led to the generation of a vast array of pollutants, posing a significant threat to the environment and human health. Among the various pollutants, organic contaminants have become a major concern due to their persistence, toxicity, and potential for bioaccumulation. Conventional wastewater treatment methods often struggle to effectively remove these recalcitrant organic compounds, necessitating the development of more efficient and sustainable treatment technologies.One such promising approach is the electrochemical Fenton process, which combines the principles of electrochemistry and the Fenton reaction to achieve the degradation of organic pollutants. The Fenton reaction, named after its discoverer Henry John Horstman Fenton, involves the generation of highly reactive hydroxyl radicals (•OH) through the reaction between hydrogen peroxide (H2O2) and ferrous ions (Fe2+). These hydroxyl radicals are potent oxidizing agents capable of breaking down a wide range of organiccompounds into less harmful or even harmless substances.The electrochemical Fenton process takes the Fenton reaction a step further by integrating an electrochemical system. In this approach, the ferrous ions required for the Fenton reaction are generated in situ through the electrochemical oxidation of an iron or steel electrode. This eliminates the need for the external addition of ferrous salts, which can lead to the generation of unwanted sludge. Additionally, the electrochemical system allows for the in situ production of hydrogen peroxide, further enhancing the efficiency of the Fenton reaction.The electrochemical Fenton process offers several advantages over traditional wastewater treatment methods. Firstly, it is highly effective in the degradation of a wide range of organic pollutants, including dyes, pesticides, pharmaceuticals, and industrial chemicals. The hydroxyl radicals generated during the process are capable of breaking down complex organic molecules into simpler, less harmful compounds, ultimately leading to the mineralization of the pollutants.Secondly, the electrochemical Fenton process is a relatively simple and cost-effective technology. The in situ generation of the required reagents, such as ferrous ions and hydrogen peroxide, eliminates the need for the external addition of costly chemicals, reducing theoverall operational costs. Additionally, the process can be easily integrated into existing wastewater treatment systems, making it a versatile and adaptable solution.Furthermore, the electrochemical Fenton process is considered an environmentally friendly technology. Unlike some conventional treatment methods that may generate hazardous sludge or byproducts, the electrochemical Fenton process typically produces only innocuous end products, such as carbon dioxide and water, minimizing the environmental impact.The implementation of the electrochemical Fenton process in wastewater treatment has been the subject of extensive research and development. Numerous studies have demonstrated the effectiveness of this technology in treating a wide range of organic pollutants, including dyes, pesticides, pharmaceuticals, and industrial chemicals. The process has been successfully applied at both laboratory and pilot scales, showcasing its potential for large-scale industrial applications.One of the key factors in the successful implementation of the electrochemical Fenton process is the optimization of various operating parameters, such as pH, current density, and the concentration of reactants. Researchers have explored different electrode materials, reactor configurations, and processmodifications to enhance the efficiency and performance of the system.Additionally, the integration of the electrochemical Fenton process with other treatment technologies, such as adsorption, membrane filtration, or biological treatment, has been investigated to further improve the overall treatment efficiency and expand the range of pollutants that can be effectively removed.As the global demand for sustainable and efficient wastewater treatment solutions continues to grow, the electrochemical Fenton process emerges as a promising technology that can contribute to addressing the pressing environmental challenges. With its ability to effectively degrade a wide range of organic contaminants, its cost-effectiveness, and its environmental friendliness, the electrochemical Fenton process holds great potential for widespread adoption in the field of wastewater treatment.。

氧还原极限电流英文

氧还原极限电流英文The limiting current of oxygen reduction (ORR) refers to the maximum current that can be achieved during the reduction of oxygen in an electrochemical cell. It is an important parameter to evaluate the performance of electrochemical devices, such as fuel cells and metal-air batteries.The ORR is a key process in many energy conversion systems, as it involves the reduction of oxygen to form water. In fuel cells, for example, the ORR occurs at the cathode where oxygen from the air reacts with hydrogen ions to produce water. The limiting current of ORR determines the maximum power output of a fuel cell and is directly related to its efficiency.There are several factors that influence the limiting current of ORR. One of the most important factors is the electrocatalyst used at the cathode. Platinum and itsalloys are widely used as electrocatalysts for ORR due to their high activity and stability. Other materials, such as transition metal oxides and carbon-based materials, have also been investigated as alternative electrocatalysts. Thechoice of electrocatalyst can greatly affect the ORRkinetics and, consequently, the limiting current.Another factor that affects the ORR limiting current is the concentration of oxygen in the electrolyte. Higher oxygen concentrations can lead to higher limiting currents, as there are more oxygen molecules available for reduction. However, excessively high oxygen concentrations can also increase the likelihood of side reactions, such as the formation of peroxides, which can reduce the overall efficiency of the electrochemical device.The temperature of the electrolyte is also an important parameter that affects the limiting current of ORR. Generally, higher temperatures promote faster reaction kinetics, leading to higher limiting currents. However, excessively high temperatures can also lead to increased electrode degradation and reduced device lifetime.In addition to these factors, the electrode surface area, the mass transport of reactants and products, and the pH of the electrolyte can also influence the ORR limiting current. Overall, achieving a high limiting current of ORR requires careful optimization of these parameters.氧还原极限电流是指在电化学电池中还原氧气时可以达到的最大电流。

氧气和水的循环伏安

氧气和水的循环伏安英文回答：The cyclic voltammetry of oxygen and water involves the measurement of the current as a function of the applied voltage. This technique is commonly used to study the electrochemical behavior of these species.In the case of oxygen, the cyclic voltammetry can provide information about its reduction and oxidation reactions. When a positive voltage is applied, oxygen molecules can be reduced at the electrode surface, forming hydroxide ions. On the other hand, when a negative voltage is applied, the hydroxide ions can be oxidized back to oxygen. By scanning the voltage in a cyclic manner, we can observe the current response and determine the electrochemical behavior of oxygen.For example, let's say we are studying the cyclic voltammetry of oxygen in an aqueous solution. We start byapplying a positive voltage to the electrode, which leads to the reduction of oxygen to hydroxide ions. As a result, we observe a peak in the current response. Then, we reverse the voltage and apply a negative voltage, causing the oxidation of hydroxide ions back to oxygen. This results in another peak in the current response, but with opposite polarity compared to the reduction peak.Now let's move on to the cyclic voltammetry of water. Water can undergo both reduction and oxidation reactions at the electrode surface. When a positive voltage is applied, water molecules can be oxidized, releasing electrons and forming oxygen gas. On the other hand, when a negative voltage is applied, water molecules can be reduced, consuming electrons and forming hydrogen gas.For instance, imagine we are investigating the cyclic voltammetry of water in an acidic solution. We start by applying a positive voltage, which leads to the oxidation of water molecules and the generation of oxygen gas. As a result, we observe a peak in the current response. Then, we reverse the voltage and apply a negative voltage, causingthe reduction of water molecules and the production of hydrogen gas. This results in another peak in the current response, but with opposite polarity compared to the oxidation peak.中文回答：氧气和水的循环伏安实验涉及测量电流与施加电压之间的关系。

离子交换法英文

离子交换法英文Ion Exchange MethodIon exchange is a versatile and widely used technique in various industries, including water treatment, chemical processing, and pharmaceutical manufacturing. The ion exchange method involves the selective removal or exchange of ions from a solution by using a solid ion exchange material, typically a resin. This process is based on the principle of reversible chemical reactions, where ions are exchanged between the solution and the ion exchange material.The ion exchange process is particularly effective in the removal of undesirable ions, such as heavy metals, hardness ions, and certain anions, from aqueous solutions. The ion exchange material, which can be either a cation exchange resin or an anion exchange resin, selectively adsorbs the target ions from the solution and releases an equivalent amount of other ions in exchange.Cation exchange resins are typically made of a polymeric matrix, such as styrene-divinylbenzene, with sulfonic acid groups attached to the matrix. These resins are capable of exchanging positively charged ions, such as sodium, calcium, and heavy metals, with hydrogen ions(H+) or other cations present in the solution. Anion exchange resins, on the other hand, are made of a similar polymeric matrix with quaternary ammonium groups attached, which can exchange negatively charged ions, such as chloride, sulfate, and nitrate, with hydroxide ions (OH-) or other anions.The ion exchange process can be divided into several steps, including loading, regeneration, and rinsing. During the loading step, the ion exchange material is contacted with the feed solution, and the target ions are adsorbed onto the resin. Once the resin's capacity is exhausted, it undergoes a regeneration step, where a concentrated solution of a regenerant, such as hydrochloric acid or sodium hydroxide, is passed through the resin to displace the adsorbed ions and restore the resin's capacity.The regeneration step is followed by a rinsing step, where the resin is washed with water to remove any residual regenerant solution and prepare it for the next cycle of operation.The ion exchange method has several advantages over other separation techniques, such as:1. High selectivity: Ion exchange resins can be designed to selectively remove specific ions from complex mixtures, making it an efficient and targeted purification method.2. Reversibility: The ion exchange process is reversible, allowing the resin to be regenerated and reused multiple times, reducing the overall operating costs.3. Continuous operation: Ion exchange systems can be designed for continuous operation, enabling a steady stream of treated water or other solutions.4. Scalability: Ion exchange technology can be easily scaled up or down to accommodate different production volumes or flow rates, making it suitable for a wide range of applications.5. Versatility: Ion exchange can be used to remove a wide range of ionic species, including heavy metals, radionuclides, and organic ions, making it a versatile separation technique.Despite its advantages, the ion exchange method also has some limitations, such as the potential for fouling or scaling of the resin due to the presence of certain contaminants in the feed solution. Additionally, the regeneration process can generate waste streams that require proper treatment and disposal.In conclusion, the ion exchange method is a powerful and widely used separation technique that plays a crucial role in variousindustries. Its ability to selectively remove and exchange ions, coupled with its reversibility and scalability, make it an indispensable tool for purification, water treatment, and other industrial processes.。

混合阳离子小柱富集酸水提取液英文

混合阳离子小柱富集酸水提取液英文Hybrid Cation Column Enrichment of Acidic Water ExtractThe extraction and purification of valuable compounds from natural sources often involve complex and multistep processes. One such technique is the use of hybrid cation column enrichment to concentrate acidic water extracts. This method combines the advantages of ion exchange chromatography and solid-phase extraction, allowing for the selective isolation and concentration of target analytes.The process begins with the collection of an acidic water extract, which may contain a variety of compounds, including organic acids, phenols, and other polar molecules. This extract is then introduced into a hybrid cation column, which is typically composed of a resin or sorbent material that has been functionalized with both cation exchange and hydrophobic moieties.As the extract passes through the column, the cation exchange sites interact with positively charged species, such as metal ions or protonated organic compounds. Simultaneously, the hydrophobic regions of the sorbent material can selectively retain non-polar ormoderately polar analytes, effectively separating them from the bulk matrix. This dual-mode interaction allows for the concentration and purification of the target compounds, while the unwanted components are eluted from the column.The specific mechanisms governing the retention and elution of analytes within the hybrid cation column depend on a variety of factors, including the pH, ionic strength, and composition of the sample matrix, as well as the properties of the sorbent material and the target compounds. Optimization of these parameters is crucial for achieving efficient and selective enrichment of the desired analytes.One of the key advantages of the hybrid cation column enrichment technique is its versatility. It can be applied to a wide range of sample types, from natural water sources to complex biological matrices, and can be used to isolate a diverse array of target compounds, including organic acids, phenols, alkaloids, and other biologically active molecules.Furthermore, the technique can be easily integrated into larger analytical workflows, such as those involving liquid chromatography or mass spectrometry, enabling the sensitive and accurate quantification of the enriched analytes. This integration can be particularly valuable in fields such as environmental monitoring,pharmaceutical research, and food quality control, where the accurate determination of trace-level compounds is of critical importance.Despite its advantages, the implementation of hybrid cation column enrichment is not without its challenges. Factors such as the complexity of the sample matrix, the presence of interfering compounds, and the potential for column fouling can all impact the efficiency and reproducibility of the extraction and purification process. Careful optimization of the column parameters, sample preparation, and elution conditions is often necessary to overcome these obstacles and achieve reliable and consistent results.In conclusion, the hybrid cation column enrichment of acidic water extracts is a powerful technique that combines the strengths of ion exchange and solid-phase extraction to selectively isolate and concentrate target analytes. Its versatility, integration into analytical workflows, and potential for overcoming matrix-related challenges make it a valuable tool in a wide range of research and industrial applications.。

离子源模式英文

离子源模式英文The ion source is a crucial component in various analytical techniques, including mass spectrometry, ion implantation, and ion beam lithography. It is responsible for generating ions of a particular nature, which are then directed into the instrument for further analysis or manipulation.There are various types of ion sources, each with its unique characteristics and modes of operation. For example, the electron ionization (EI) source, commonly used in mass spectrometry, creates a beam of electrons that interact with the sample to generate positively charged ions. Similarly, the matrix-assisted laser desorption/ionization (MALDI) source uses a laser to desorb and ionize molecules from a matrix material.Another important aspect of ion sources is their mode of operation, which determines the type of ions that are generated. In electron ionization, the most common mode is the "hard" ionization mode, which generates highly energetic ions with many fragments. In contrast, the "soft" ionization mode generates less energetic ions with fewer fragmentations, allowing for more straightforward analysis of molecular structures.In addition to the traditional ion sources, there are also newer methods being developed, such as electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), which are widely used in the field of proteomics for the analysis of complex biological samples.Overall, the ion source is an essential component in various analytical techniques, and advances in ion source technology have led to improvements in sensitivity, resolution, and reliability in analytical instrumentation.。

关于臭氟氧的作文英语

关于臭氟氧的作文英语英文回答：Chlorofluorocarbons, also known as CFCs, are a group of chemicals that have been widely used in various industries for decades. They were commonly used as refrigerants in air conditioners and refrigerators, as propellants in aerosol sprays, and in the production of foam insulation. However, the use of CFCs has been linked to the depletion of the ozone layer, which is a crucial part of the Earth's atmosphere that protects us from harmful ultraviolet radiation from the sun.I remember learning about the harmful effects of CFCs in school and how they contribute to ozone depletion. It was shocking to realize that something as common as a can of hairspray could have such a negative impact on the environment. I also remember hearing about the Montreal Protocol, an international treaty aimed at phasing out the production and use of CFCs to protect the ozone layer.In recent years, there has been a global effort to find alternatives to CFCs in various industries. Manufacturers have developed new refrigerants that are more environmentally friendly, and aerosol sprays now use propellants that do not harm the ozone layer. These changes are a step in the right direction towards protecting our planet for future generations.中文回答：氯氟烃，也称为CFCs，是一类在各行各业广泛使用了几十年的化学物质。

水解氯英文版检测方法的附件英文

水解氯英文版检测方法的附件英文Attachment for the English version of the testing method for Chloride hydrolysis:1. IntroductionThe chloride hydrolysis test method is used to determine the level of chloride content in a sample by measuring its hydrolysis. This attachment provides additional information and guidelines to conduct this test in an English version.2. Equipment and Materials- Sample container- Deionized water- Pipettes- pH meter- Burette- Sodium hydroxide (NaOH) solution- Indicator (e.g., phenolphthalein)- Glass beakers- Heating source (e.g., Bunsen burner)- Filter paper- Analytical balance3. Procedure3.1 Sample Preparation- Weigh an appropriate amount of the sample using an analytical balance.- Transfer the sample into a sample container.3.2 Hydrolysis- Add deionized water to the sample container, ensuring that the sample is completely submerged.- Allow the sample to hydrolyze for a predetermined period (e.g., 24 hours) at room temperature.3.3 Measurement- Take a pH measurement of the hydrolyzed sample using a pH meter.- Record the pH value obtained.3.4 Titration- Transfer a known volume of the hydrolyzed sample (e.g., 50 mL) into a glass beaker.- Add a few drops of the indicator to the beaker.- Titrate the sample with sodium hydroxide solution until the pH reaches the desired endpoint (e.g., pH 8.3). Record the volume of NaOH solution used.4. Calculation- Calculate the chloride content in the sample using the volume of NaOH solution used, the concentration of the NaOH solution, and the initial mass of the sample.5. ReportingReport the chloride content of the sample in the appropriate unit (e.g., ppm) along with the testing conditions, including the sample preparation method, hydrolysis time, pH measurement, and titration procedure.Please note that this is a general guidance for the English versionof the testing method for chloride hydrolysis. Specific details and procedure may vary depending on the laboratory's protocols and requirements.。

扬州“PEP”2024年11版小学三年级下册第1次英语第二单元真题试卷

扬州“PEP”2024年11版小学三年级下册英语第二单元真题试卷考试时间：100分钟（总分:140）A卷考试人：_________题号一二三四五总分得分一、综合题(共计100题)1、填空题：The ________ sings in the morning.2、选择题：What is the main ingredient in hummus?A. ChickpeasB. LentilsC. PeasD. Beans3、听力题：The cat is ___ (purring/meowing).4、填空题：My grandma always says, “Call me !” (我奶奶总是说：“叫我！”)5、听力题：The ________ is an important area for wildlife conservation.6、听力题：The chemical formula for hydrogen peroxide is ________.7、听力题：A geyser is a natural fountain of ______.8、What do you call a young goose?A. GoslingB. ChickC. DucklingD. Fawn9、What is the main purpose of an umbrella?A. To keep you warmB. To keep you dryC. To provide shadeD. To decorate10、填空题：My favorite animal is a ______ (猫) that loves to chase toys.11、What do we call the person who designs buildings?A. EngineerB. ArchitectC. ContractorD. Carpenter答案: B12、What is the largest continent?A. AfricaB. AsiaC. EuropeD. Antarctica答案: B13、听力题：A reaction that produces gas is called a ______ reaction.14、What is the term for a person who designs buildings?A. EngineerB. ArchitectC. ContractorD. Builder答案:B15、填空题：The ________ was a renowned leader in the civil rights movement.16、听力题：I have a ___ (funny) story to tell.17、填空题：I enjoy making ______ (手工艺品) for my friends.18、填空题：My friend is __________ (幽默感)十足。