Regioselective Synthesis, Crystal Structure and Biological Activity of Novel 2-Phenylsulf
Cu2ZnSnS4类四元硫族半导体的理论研究
Cu2ZnSnS4类四元硫族半导体的理论研究*)))以二元、三元、四元半导体的演化为思路陈时友1,2龚新高1,Ar on Walsh3魏苏淮4(1复旦大学物质计算科学教育部重点实验室上海200433)(2华东师范大学极化材料与器件教育部重点实验室上海200241)(3伦敦大学学院化学系伦敦W C1E6BT英国)(4美国可再生能源国家实验室科罗拉多80401美国)摘要在过去60多年中,人们对半导体的研究集中在一元、二元和三元半导体方面,最近,出于寻找新型廉价、环保、高效光伏转换材料的需要,Cu2ZnSnS4类I2-II-I V-V I4型四元硫族半导体吸引了人们越来越多的关注,它在光催化和热电等多方面的应用也不断被发掘.然而,对于这类四元半导体的基本性质,如晶体结构和电子结构,人们知之甚少,很多研究还停留在经验阶段.文章首先简要回顾了这类半导体的由来和在应用方面的最新进展,然后详细介绍了文章作者对这类四元半导体的第一性原理计算研究工作的进展,其中包括:系统研究了这类硫族半导体在从二元向三元再向四元的演化过程中晶体结构和电子能带结构变化的规律,总结了元素成分对其影响的一般趋势,并结合实验结果分析了这类四元半导体晶格结构表征和带隙测量中易于出现的混淆;文章作者还以Cu2ZnSnS4为例,考察了这类四元化合物相对二元、三元化合物的相稳定性和本征缺陷性质.文章介绍的研究结果将为一系列I2-I I-IV-VI4型四元半导体的深入研究提供基础.关键词Cu2ZnSnS4,四元硫族半导体,晶体结构,电子结构,缺陷,第一性原理计算Recent progress in the theoretical study ofCu2ZnSnS4and related chalcogenide semiconductorsCHEN Sh-i You1,2GON G Xing-Gao1,A ron Walsh3WEI Su-H uai4 (1K ey L aborator y of Comp utational P hysical S ciences,Ministry of E du cation,F udan University,S hang hai200433,China) (2K ey L aborator y of Polar M ater ia ls and Devices,Ministry of E ducation,Ea st China N ormal Univercity,Sh anghai200241,C hina)(3University College L ondon,Dep ar tment of Chemistr y,UK)(4N ational Renew able E nerg y L abor atory,US A)Abstract In the past sixty years,most of the studies about semiconductors focused on the elementary,binary and t ernary semiconductors.Rec ent ly in searching for cheap,environmentally-friendly and high-efficiency solarc ell absorbers,quaternary chalcogenides I2-I-I IV-VI4,such as Cu2ZnSnS4,have drawn more and more attention,and t heir pot ential applic ation as different functional mat erials are being explored.Howe ver,their fundamental material properties have not been well studied.In t his paper,aft er giving a simple introduction to the history and application of I2-I-I IV-VI4semiconduc t ors,we will review our firs-t principles calculat ion st udy on these semicon-duc t ors,which includes,(i)revealed t he general rules in the change of crystal and electronic struc t ure as the num-ber of elements increases from2to4,and found clear chemical tre nds in their dependence on the composition ele-ment s,(ii)disc ussed the possible confusion in the previous structure charac t erizat ion and band gap measurement, (iii)studied the phase stability of t he represent ative c ompound Cu2ZnSnS4relative t o the compe t itive binary and t ernary compounds,as well as t he properties of its intrinsic defects.We believe the results presented in this paper will offer some hints for the future study of the series of I2-I-I IV-VI4semic onductors.*国家自然科学基金(批准号:10934002;10950110324)、国家重点基础研究发展计划、教育部专项基金、上海市自然科学基金(批准号: 10ZR1408800)、美国能源部基金(批准号:DE-AC36-08GO28308)资助项目2011-03-16收到通讯联系人.Em ail:x ggon g@Keywords Cu 2ZnSnS 4,quaternary chalcogenide semiconductors,crystal struct ure,electronic st ructure,defects,first -principles calculat ion1 Cu 2ZnSnS 4半导体的由来半导体材料是过去60年中最受关注的材料之一.按照所含元素的多少,常见半导体可以分为:一元的元素半导体,如IV 族的C,Si 和Ge,二元的化合物半导体,如III -V 族的GaN,GaAs,InSb 和II -VI 族的ZnO,ZnS,CdTe,H g Te 等.然而,不同应用对半导体性质提出的特定要求越来越多,这些常见半导体数量有限,性质参数都是固定的,往往不能满足器件设计的要求.例如,常见一元和二元半导体的带边位置是确定的,如图1所示,相互间存在带阶,未必能满足器件设计对带边位置(如价带顶和导带底)的要求.一个自然的思路是,将现有的两种半导体混合形成合金半导体,通过调节其成分,连续地调控其性质参数,如In x Ga 1-x N,A l x Ga 1-x N,H g x Cd 1-x T e 等[1].但是,对于合金半导体,如何生长成分均匀、缺陷密度低的样品在实验上有着一定的难度.图1 第一性原理计算的IV 族、III -V 族和II -VI 族半导体的价带顶相对排布图.引自文献[2]另外一个思路是,设计三元的化合物半导体.在二元II -VI 族半导体中,将+2价的II 族阳离子(II=Zn,Cd)替换为+1价的I 族(I=Ag,Cu)和+3价的III 族(III=Al,Ga,In)阳离子,就得到I -III -V I 2型三元半导体[3].如将ZnS 中的Zn 替换为Cu 和Ga,就得到CuGaS 2(如图2所示).由于II -V I 族半导体一般具有四配位的闪锌矿(zincblende)和纤锌矿(w urtzite)结构,其中VI 族阴离子总是被4个II 族阳离子围绕,而在上述替换后每个VI 族阴离子将被2个+1价的I 族阳离子和2个+3价的III 族阳离子围绕,阴离子仍处于八电子满壳层状态(满足局域的电中性,简称八电子规则),因此,其性质与/父辈0的II -VI 保持一定的继承关系,如结构相似,电子结构保持半导体特征.图2 二元、三元、四元硫族半导体的演化示意图这种通过阳离子替换演化出新型半导体的思想有着很久的历史,1950年代,Goodman 等就以八电子规则作为标准推演可能的化合物半导体,如从II -VI 出发得到I -III -VI 2类三元半导体CuGaS 2和Ag InSe 2等,从III -V 出发得到II -IV -V 2类半导体[4,5].1970年代以来,这些三元半导体被广泛用于非线性光学和光电器件中.特别是CuInSe 2(带隙1.04eV)和CuGaSe 2(带隙1.68eV),由于其带隙接近单p-n 结太阳能电池吸收层的最优带隙(1.4)1.5eV)而受到特别关注,通过形成Cu(In x Ga 1-x )Se 2合金(简称CIGS),还可以进一步调节带隙,以此合金为吸收层的薄膜太阳能电池的效率在实验室内已接近20%[6],产品也已经市场化,被认为是新一代太阳能电池.既然二元半导体可以通过阳离子替换演化为三元半导体,我们也可以期盼从三元半导体演化为四元半导体[4,5].如图2所示,在I -III -VI 2型三元半导体中,将III 族阳离子进一步替换为II 族和IV 族(IV=Si,Ge,Sn)离子,就可以得到I 2-II -IV -VI 4型四元半导体,例如CuGaS 2中2个Ga 替换为Zn 和Ge 就得到Cu 2ZnGeS 4,2个Ga 替换为Zn 和Sn 就得到Cu 2ZnSnS 4[7)9].通过改变I,II,IV,VI 族阳离子,如I =Cu,Ag;II =Zn,Cd;IV =Si,Ge,Sn;VI=S,Se,T e 等,我们可以得到一大类I 2-II -IV -VI 4型四元半导体[10],由于其阴离子总是VI 族的,我们称这类半导体为硫族半导体.2 I 2-II -IV -V I 4型半导体的应用2.1 在薄膜太阳能电池方面的应用目前,两种主流的薄膜太阳能电池吸收层半导体,CIGS 合金和CdTe,在面向大规模生产时受到原材料稀缺、昂贵、组成元素的毒性的约束,如CIGS 中In 金属非常昂贵,CdTe 中的T e 产量也有限,在电池发电量达到GW 量级时都会出现原材料瓶颈,另外Cd 还有毒性,进一步增加了生产的难度,因此,需要寻找更优的吸收层半导体.近15年来,出于寻找廉价、环保、高效的太阳能电池吸收层半导体的需要,人们对I 2-II -IV -VI 4类四元半导体的关注显著增多[11)23].其中Cu 2ZnSnS 4(简称CZT S)和Cu 2ZnSnSe 4(简称CZT Se)半导体受到最多关注,因为其可能成为理想的吸收层半导体.这种四元材料仅包含自然界储量丰富、廉价、对环境无害的元素,例如在地壳中这些元素的丰度如下:Cu:50ppm,Zn:75ppm,Sn:2.2ppm ,S:260ppm,而In 则仅为0.05ppm 甚至更低,因此原材料成本上有很大优势[12];另外,实验测量发现,其带隙接近1.5eV,是单结太阳能电池的最优带隙,并且其光吸收系数很高(>104cm -1)[12)15],因而可能具有很高的光电转换效率.表1 使用不同方法制作的C u 2ZnSnS 4和Cu 2ZnS nSe 4类太阳能电池的器件参数成分合成方法V oc /mV J sc /(m A/cm 2)FF/%G /%参考文献Cu 2ZnSn S 4非真空电镀56314.841 3.4[24]Cu 2ZnSn S 4射频磁控溅射+硫化61017.962 6.77[22]Cu 2ZnSn S 4溶胶凝胶法沉积前驱物+硫化5759.6936.4 2.03[25]Cu 2ZnSn S 4脉冲激光沉积546 6.7848 1.74[26]Cu 2ZnSn S 4快速共蒸发54113.059.8 4.1[27]Cu 2ZnSn S 4热蒸发58717.865 6.81[28]Cu 2ZnSn S 4热注入法合成纳米晶体18810.537.20.73[18]Cu 2ZnS nSe 4磁控溅射法制作前驱体+硒化35.920.743 3.2[29]Cu 2ZnSn(S 0.75Se 0.25)4等温结晶62215.8760 5.9[30]Cu 2ZnS n(S,Se)4联氨溶液沉积51628.6659.66[22]Cu 2ZnS n(S,Se)4热注入法合成纳米晶体42030.452.77.2[31]1996年,日本H.Katagiri 研究组制作了第一个Cu 2ZnSnS 4太阳能电池,当时效率仅有0.66%.随后效率的上升很缓慢,相关研究也没有受到重视,直到2005年以后,关于Cu 2ZnSnS 4和Cu 2ZnSnSe 4的研究论文快速增多,电池效率也不断刷新,2006年达到5.74%,2007年达到6.77%[13].在表1中,我们列出了多个研究组使用不同生长方法制作的Cu 2ZnSnS 4和Cu 2ZnSnSe 4相关太阳能电池的器件参数.可以看出,材料生长合成的方法不同,得到的器件效率等性能参数有显著差别,其中,IBM 的一个研究组制作的基于Cu 2ZnSn(S,Se)4合金的太阳能电池效率达到9.66%[22],接近可以应用的标准,极大地鼓舞了该领域的研究.另外,最近2个非常重要的突破是,IBM 的研究组成功地用热蒸发的方法制作出了效率达到6.8%的Cu 2ZnSnS 4电池,并且将沉积后的退火时间由以前的3个小时减少到只要几分钟[28];Purdue 大学的研究组用hot injection 方法,制作出了效率达到7.2%、基于Cu 2ZnSn(S,Se)4合金的电池,其中合金是通过硒化Cu 2ZnSnS 4纳米晶体得到,而在一年前,基于Cu 2ZnSnS 4纳米晶体的电池效率仅为0.73%[18,31].随着越来越多研究组的加入,Cu 2ZnSnS 4和Cu 2ZnSnSe 4相关太阳能电池的效率提升可能会越来越快,一个期望是其电池效率接近或超过CIGS 电池.由于Cu 2ZnSnS 4和Cu 2ZnSnSe 4在晶体结构和电子结构等性质上继承了CuInSe 2和CuGaSe 2的特征,其电池器件往往也采用与CIGS 电池类似的结构,如图3所示的ZnO/CdS/Cu 2ZnSnS 4/M o/SLG结构.材料性质和器件结构上的相似有利于较为成熟的CIGS电池工艺方便地过渡到CZTS电池上.图3Cu2ZnSnS4和Cu2ZnSn Se4薄膜太阳能电池典型器件结构示意图作为四元半导体材料,Cu2ZnSnS4和Cu2ZnSnSe4类电池的研究也面临着许多问题和困难.比如说,合成的样品往往质量较差,成分偏离理想化学配比,不均匀以及缺陷浓度高,这些对器件性能参数的影响目前还不清楚;又比如,Cu2ZnSnS4的带隙1.5eV十分接近单结电池的最优带隙,然而,实验发现,引入Se后的Cu2ZnSn(S,Se)4合金作为吸收层的电池效率更高(见表1)[22],其原因目前也还没有被理解.回顾Cu2ZnSnS4类电池近15年来的发展,大多数的研究停留在/改变合成方法或者成分、温度等条件来进行合成材料-制作器件-测量性能参数0的层次,尽管观察到器件性能的变化,却缺乏对微观物理机制的深层理解,对器件性能的优化基于经验.正如H.Katagiri等所指出,要想进一步提高Cu2ZnSnS4类电池的效率,面临很多问题,其中一个非常重要的方面是需要对其基本的物理性质有清晰完整的认识[13].相对于四元的Cu2ZnSnS4,人们对CuInSe2和CuGaSe2等三元半导体基本物理性质的认识要透彻得多,比如其电子能带结构、本征缺陷性质、表面和界面性质等等.前期的研究表明,CIGS电池之所以能够表现出较高的效率以及优良的电学特性和稳定性,比如多晶薄膜电池效率甚至高于单晶的,是因为其有着独特的缺陷和界面等性质.要进一步优化Cu2ZnSnS4类电池效率或者预测其发展前景是否优于CIGS电池,也需要对这些基本物理性质有更多的了解.研究这样一种四元材料的基本物理性质,既要克服合成优质晶体样品的困难,也要面对四元半导体成分和结构自由度增多带来的复杂性,因此,在这个领域下一步的发展中,深入探索材料基本物理性质将是一个重要的方面.2.2在光催化、热电方面的应用除了在太阳能电池中的应用,这类四元硫族半导体还在光催化、热电、磁光等方面表现出了很好的应用前景.例如Cu2ZnGeS4,Ag2ZnGeS4和Ag2ZnSnS4在可见光的照射下可以从Na2S# K2SO3溶液中产生氢,有着较高的活性[32,33]; Cu2ZnSnSe4和Cu2CdSnSe4等被作为新型热电材料,其热电优值ZT在700K温度下达到0.65,高于大多数现有热电材料[34)37].四元半导体元素种类的增多对于热电材料的设计有着独特的优势,为了获得高热电优值ZT,需要提高材料的电导率,并降低热导率,在Cu2CdSnSe4四元半导体中,晶格中的Cu2Se2结构子单元控制着电导,而CdSnSe2子单元不参与电导,因而有可能在提高其电导的同时保持热导不变.F.Liu等的实验发现[35],通过增加Cu的化学配比,将部分的Cd替换为Cu,可以增加空穴载流子浓度,使电导率增加,同时CdSnSe2子单元的有序性被破坏,使得热导率降低,综合起来该类四元半导体可以表现出很高的热电优值ZT.除此之外, Cu2MnSnS4,Ag2M nGeSe4还被作为稀磁半导体、磁光乃至多铁性材料加以研究[38)42].2.3制约研究和应用的问题I2-II-IV-VI4型四元半导体虽然具有丰富的性质,有广泛的应用前景,但是从1960年左右被提出并合成以来,研究进展缓慢[4,5,10],直到最近5年才有了突破性的进展.这一方面是由于在一元、二元、三元半导体研究得还不透彻,应用前景发掘还不充分的情况下,人们不会在四元半导体上投入太多的精力;另一方面,四元材料生长合成和性质的复杂性使得相关的研究有较大的难度,还有很多问题没有回答.元素的增多使得化学成分和结构自由度增多,对四元半导体的研究相对于一元、二元简单半导体而言要复杂很多.首先是如何合成出具有特定成分的四元半导体,如何避免二元、三元杂相的产生[21],其成分是否满足理想配比,是否均匀,其晶体结构如何,其中阳离子如何分布、排列,这些都是没有回答清楚的问题.事实上,即使到现在,I2-II-IV-VI4晶体结构的许多独特性质也还没有被完全理解[9,43].基本成分和晶体结构的不清楚也导致电学、光学等性质研究的困难.对于最为基本的半导体能带带隙的测量,虽然光学吸收、反射谱的测量能给出带隙大小,但由于样品成分偏差、缺陷多等问题,不同组测量结果差别很大,某些结果表现出反常特征.例如,以前很多吸收谱测量显示Cu2ZnSnSe4的带隙为1. 5eV左右[44)46],直到2009年,理论和进一步仔细的实验研究才揭示其带隙应在1.0eV左右[8,20].这些基本性质研究的欠缺和研究的困难是过去四元半导体研究进展缓慢的原因,也是制约I2-II-IV-VI4在不同方面应用的普遍问题.在过去的5年中,我们以硫族半导体从二元向三元再向四元演化为思路,通过理论计算,研究了I2-II-IV-V I4类半导体晶体结构、电子结构等基本性质变化的规律,并以Cu2ZnSnS4为例,探讨了该类四元半导体相对于二元、三元相的相稳定性和缺陷性质.这是本文讨论的主要内容,其中,直接的计算主要围绕几种光电和光催化相关半导体展开,但通过理论分析得到的趋势和规律对所有I2-II-IV-V I4四元半导体都是适用的,可以为不同方面的应用提供指导.3晶体结构的演化3.1二元、三元、四元半导体结构对于二元II-VI族半导体,ZnS结构(闪锌矿, zinc-blende)是有代表性的晶体结构.当II族阳离子被I族和III族阳离子替换变成三元I-III-VI2型半导体时,其晶体结构也可以通过在闪锌矿结构中进行阳离子替换得到.如图4所示,ZnS中每个S周围围绕着4个Zn,当ZnS演化为CuGaS2时,每个S 周围变为围绕着2个Cu和2个Ga,这样阴阳离子附近总是保持局域电中性(即八电子规则),满足这个条件的Cu和Ga的排列有2种,即黄铜矿结构(chalco pyr ite,简称CH,见图4(b),空间群I4-2d)和铜金合金结构(CuA u,简称CA,见图4(c)).大量的实验和理论研究表明[3],这类I-III-VI2半导体往往以黄铜矿结构为基态,这是由于CH结构易于容忍I-VI和III-VI键长的差别,应变能较低[47];另一方面,这类极性半导体还存在部分的离子性,而CH 结构也具有较CA结构低的静电库仑能[48].当-I II-I VI2中2个III族离子进一步被II和IV 替换,形成I2-I-I IV-VI4类四元半导体时,黄铜矿结构就演化为锌黄锡矿结构(kesterite,简称KS,见图4 (d),空间群为I4-);而三元时亚稳的铜金合金结构,依赖于阳离子替换方式不同可以演化为两种结构:一种是黄锡矿结构(stannite,简称ST,见图4(e),空间群为I4-2m),另一种是原胞混合的铜金合金结构(primitive-mixed CuAu structure,简称PM CA,见图4(f),空间群P4-2m)[9].这三种结构的原胞都只有8个原子,除这3种结构外,I,II,IV族阳离子的不同排列还可以产生很多其他结构,有些也满足局域电中性条件(即八电子规则),但原胞都更大,因此,可以将锌黄锡矿、黄锡矿和PMCA结构看作是I2-I-I IV-VI4类四元半导体的三种基本结构.图4二元、三元、四元硫族半导体晶体结构演化示意图(a)闪锌矿结构(zinc-blende)ZnS;(b)黄铜矿结构(chalcopyrite)CuGaS2;(c)铜金合金结构(CuAu like)CuGaS2;(d)锌黄锡矿结构(kesterite) Cu2ZnGeS4;(e)黄锡矿结构(stannite)Cu2ZnGeS4;(f)混合铜金合金结构(PM CA)Cu2ZnGeS4.引自文献[9]前期的实验研究中,大多将I2-I-I IV-VI4半导体表征为黄锡矿结构,对Cu2ZnSnS4和Cu2ZnSnSe4有较多实验宣称是锌黄锡矿结构,也有很多宣称是黄锡矿结构,其中包括最近3年的实验[8,9].可以说,对于I2-I-I IV-VI4类四元半导体的晶体结构构型,目前还没有定论,下面我们将对三种基本结构的相对能量稳定性进行讨论.3.2结构的相对能量稳定性在三种基本结构中,三种阳离子排布方式各不相同,使得其静电库仑能和离子大小差别引起的弹性应变能也各不相同,因而有不同的能量稳定性.如果阳离子的替换限制在元素周期表中的同行元素,如Zn y CuGa y Cu2ZnGe和Cd y Ag In y Ag2CdGe,这时I2-II-IV-VI4中同行阳离子大小差别很小,因而结构内的离子位置弛豫较小,弹性应变能的影响可以忽略,不同结构构型的静电库仑能差别是决定相对能量稳定性的主要因素.的确,对三种结构的Cu2ZnGeS4和Ag2CdSnS4进行的总能计算表明[9],从锌黄锡矿(KS)结构到黄锡矿(ST)结构再到PM-CA结构,总能依次上升,这个次序与静电库仑能的次序一致.考虑到KS结构由三元的CH结构演化而来,可以说,此时KS结构继承了CH的总能优势.这一继承关系不受阴离子的改变影响,对硫化物(S)、硒化物(Se)、碲化物(T e)普遍适用.当阳离子的替换拓宽到周期表的不同行时,由于阳离子大小差别引起的应变弹性能也将影响不同结构的稳定性.随着I,II和IV族阳离子的改变,这些半导体的基态晶体结构既可能是KS结构,也可能是ST结构,例如Cu2CdGeS4,Cu2CdSnS4是以ST结构为基态,而Cu2ZnSnS4,Ag2CdGeS4等是以KS结构为基态[9,43].PMCA结构在能量上总是较高.在图5中,我们绘出了KS和ST结构的相对能量差随IV阳离子增大而变化的情况,可以发现,能量差的绝对值随着IV阳离子的增大而减小.图5黄锡矿(ST)结构和锌黄锡矿(KS)结构的能量差随IV族阳离子的变化.引自参考文献[43]值得指出的是,这些能量的相对稳定性次序由阳离子决定,不受硫族阴离子的改变影响,阴离子的改变只会引起相对数值的变化,不会带来次序的改变,当硫化物的KS结构比ST结构能量低时,则相应的硒(Se)化物和碲(Te)化物的KS结构能量也更低,反之亦然.3.3结构混淆的原因如前所述,在很多与I2-II-IV-VI4相关的实验文献和数据手册中,往往宣称这类半导体呈ST(黄锡矿)结构[10,40)42],仅有部分实验将Cu2ZnSnS4表征为KS结构.而我们的计算结果表明,多数体系以KS结构作为基态,仅有Cu2CdGeS4和Cu2CdSnS4是以ST结构作为基态.为寻找理论和实验不相符的原因,我们先看看实验上表征晶体结构的方法:首先,不同的I2-II-IV-VI4样品被合成[20,40)42],然后,测量这些样品的X射线衍射谱,并采用可能的结构模型对其进行拟合,根据拟合的符合程度判定此结构是否是样品的结构.对于这一表征方法,我们发现以下两方面的原因可能导致结构的混淆:图6对Cu2ZnSnS4的KS和ST结构计算的X射线衍射谱(结构参数通过第一性原理优化得到,X射线源采用Cu的K A线,波长为0.15406nm)(1)ST和KS结构的不同仅在于阳离子在子晶格中的不同排布,当I族、II族和IV族阳离子在元素周期表中同行,如Cu,Zn和Ge,以及Ag,Cd和Sn,其原子序数和离子大小都相近,形状因子差别不大,使得两种离子的不同排列表现出相同的衍射特征,因此常用的X射线衍射难以区分这些体系的ST和KS结构.图6中,我们给出了理论计算出的KS和ST两种结构的Cu2ZnSnS4的X射线衍射谱,可以看出,两种结构的图谱十分相似.事实上, Parasyuk及其合作者在实验中已经注意到:空间群为I4-2m的ST结构和空间群为I4-2m的KS结构都可以在Cu 2ZnGeSe 4样品的X 射线衍射谱拟合中给出可接受的R -因子[42].(2)除了上述实验手段方面的原因,I 2-II -IV -V I 4本身易于出现的阳离子部分无序化现象也是结构混淆的重要原因.在Cu 2ZnSnS 4和Cu 2ZnSnSe 4中,由于Cu 和Zn 的相似性,KS 结构中的(001)Cu +Zn 层内易于产生无序化.Cu+Zn 层的部分无序化使得KS 结构表现出与ST 一样的空间群,X 射线衍射谱难以区分.对于Cu 2ZnSnS 4,中子散射的测量显示[49],KS 结构的确易于出现Cu+Zn 层的部分无序化.综合以上两方面的原因,我们指出,在I 2-II -IV -V I 4类四元半导体的结构表征中,如X 射线衍射图谱的拟合中,需要考察不同的结构模型;当不同的结构模型通过衍射图谱不能区分时,还需要结合其他的实验手段(如中子散射、非弹性X 射线散射等)和理论计算结果,以准确确定相似阳离子的占位情况.至此,我们对II -VI,I -III -VI 2,I 2-II -IV -VI 4晶体结构的讨论都是围绕着由立方闪锌矿结构演化而来的各种结构展开的,如三元的CH ,CA 结构和四元的KS,ST 及PM CA 结构.众所周知,II -VI 半导体还有另外一种主流结构,即六角的纤锌矿结构,以二元纤锌矿结构为出发点,我们也可以演化出三元的六角CH 结构、六角CA 结构,以及六角KS 结构和六角ST 结构[43].实验上多个I 2-II -IV -VI 4半导体被发现呈六角ST 结构,或者高温相呈六角ST 结构[50)52].根据理论计算,我们发现,与上述四方结构的混淆原因类似,六角KS 结构也易于被混淆为六角ST 结构;六角KS 结构和立方KS 结构之间、六角ST 结构和立方ST 结构之间在性质上有清楚的对应关系;对某些离子性强、IV 族阳离子小的半导体,六角KS 或ST 结构较立方结构能量上更为稳定,是体系的基态结构.4 电子结构的演化4.1 带隙的变化规律在二元向三元再向四元的演化过程中,如ZnS,CuGaS 2与Cu 2ZnGeS 4,CdS,Ag InS 2与A g 2CdSnS 4,带隙依次显著下降,幅度达到1.5eV.这一单调下降的过程可以从图7中的价带顶和导带底排布图中清晰地看出,从ZnS 到CuGaS 2价带顶大幅度上升,而导带底小幅度下降,使得带隙大幅度减小;从CuGaS 2到Cu 2ZnGeS 4价带顶保持不变,导带底进一步小幅度下降,带隙也小幅度减小.比较不同结构的带隙,三元CH 结构的带隙大于CA 结构的带隙,这是由于对称性的不同[9];相应地,由CH 结构演化来的KS 结构带隙也大于由CA 结构演化而来的ST 和PMCA 结构带隙.图7 Zn S,CuGaS 2和Cu 2ZnGeS 4价带顶和导带底的排布图(自旋轨道耦合作用未考虑).引自参考文献[9]闪锌矿结构II -VI 族半导体具有直接带隙,演化为三元I -III -VI 2后,CH 和CA 结构仍然保持直接带隙的特征;进一步演化为I 2-II -IV -V I 4后,KS 结构继承了CH 结构的直接带隙特征,ST 结构也保持了CA 结构的直接带隙,然而,PM CA 结构的带隙却变为间接带隙[9],如图8所示.PM CA 结构由于在能量上显著高于KS 和ST 结构,因而难以稳定,合成的I 2-II -IV -VI 4半导体样品往往表现出直接带隙.图8 Cu 2ZnGeS 4的电子能带结构,沿第一Brillouin 区内的T (Z):2P a (0,0,0.5)y #:(0,0,0)y N(A):2Pa(0.5,0.5,0.5)(a)KS 结构;(b)S T 结构;(c)PM CA 结构(其中导带已被上移,以修正广义梯度近似(GGA)的交换关联势引起的带隙偏小误差).引自参考文献[9]进一步比较不同I 2-I-I IV -VI 4半导体带隙的大小,我们发现,带隙随不同族元素的变化有如下规律:Ñ: Cu y Ag 带隙{ Ò: Zn y Cd 带隙| Ô: Si y Ge y Sn 带隙| Ö: S y Se y T e带隙|即在结构相同、其他元素不变的条件下,I 族阳离子。
基于铌酸锂光子线的极化分裂器的设计和仿真
基于铌酸锂光子线的极化分裂器的设计和仿真薛赞;陈迪;陈明【摘要】为了设计一种基于铌酸锂光子线的极化分裂器，采用基于有限元法的电磁仿真软件，对该器件进行了优化和仿真分析，得到了结构尺寸紧凑的设计结果。
同时考虑到常规工艺误差的影响，分析了波导宽度变化对器件的透射率的影响。
结果表明，极化分裂器的带宽、能量透过率与波导耦合长度有着紧密的联系。
%In order to design a polarization splitter based on lithium niobate photonic wires , the splitter was analyzed and optimized by using the electromagnetic simulation software based on finite element method and the optimal design result of compact structure size was gotten .The effects of the changes of waveguide width on the transmission of the splitter were analyzed with the consideration of the common process error .The results show that the bandwidth and power transmittance of the polarization splitter have the strong relationship with the waveguide coupling length .【期刊名称】《激光技术》【年(卷),期】2015(000)005【总页数】3页(P694-696)【关键词】集成光学;极化分裂器;铌酸锂光子线;带宽【作者】薛赞;陈迪;陈明【作者单位】西安邮电大学电子工程学院，西安710121;西安邮电大学电子工程学院，西安710121;西安邮电大学电子工程学院，西安710121【正文语种】中文【中图分类】TN256引言在当今的信息社会，光极化分裂器已经是光子集成电路中光信号重新分配的一个重要组成部分。
超冷铷铯极性分子振转光谱的实验研究
超冷铷铯极性分子振转光谱的实验研究超冷铷铯极性分子振转光谱的实验研究近年来，超冷（≤1K）分子技术受到了人们的广泛关注，因为它能将分子保持在特定的状态，这使得我们可以对特定的分子构型进行更清晰地研究。
其中，铷（Tl）-铯（Cs）极性分子，由其多构态结构使其有重要的研究价值和应用前景。
早期实验都以一体化的光谱仪来研究Tl-Cs极性分子，但是却无法获得Tl-Cs极性分子的振转光谱数据。
因此，我们研究的实验的主要目的是，用基于测试台的实验来研究超冷Tl-Cs极性分子的振转光谱。
在这次实验中，我们使用了一台基于测试台的多百气体混合分子激光冷却装置（DTM），来制备Tl-Cs极性分子。
其中包括一台脉冲-魔鬼激光装置，频率控制器，电控终端，等离子体产生器，测试台，以及一个用于检测Tl-Cs极性分子振转光谱的激光分析仪。
在实验中，我们首先使用脉冲—魔鬼激光装置将Tl—Cs分子激烈地击打和压缩至超液态态，随后使用等离子体产生器进行加速，并将晶体放入测试台上。
然后，夹着准备好的晶体，我们将激光发射到晶体上，来测试Tl—Cs极性分子的振转势能，以及振转光谱。
并且，我们除此以外还测试了Tl—Cs极性分子中异构态相互作用的振转光谱，以及极性分子的分子常数的测定。
最终，我们获得的实验数据可以清晰地描述Tl-Cs极性分子的振转光谱和构型，以及异构态相互作用的强度和分子常数。
具体来说，振转强度数据与当今关于Tl-Cs极性分子振转能量系统的理论计算相一致，而分子常数的测量值也与理论值保持很好的一致性。
总的来说，本次实验的成果为Tl-Cs极性分子的振转光谱和分子常数的研究奠定了基础，这也给了我们全新思考超冷分子技术在学术和应用领域上的潜力。
未来，将可以以此为基础研究更多关于极性分子的有关特性，以及超液态极性分子的更多研究工作。
化学试剂电感耦合等离子体原子发射光谱法通则 -回复
化学试剂电感耦合等离子体原子发射光谱法通则-回复这个主题是关于化学试剂电感耦合等离子体原子发射光谱法通则。
在本篇文章中，我将一步一步回答相关问题，并解释这些内容的背景和重要性。
首先，让我们来了解一下化学试剂电感耦合等离子体原子发射光谱法（Inductively Coupled Plasma Atomic Emission Spectrometry，ICP-AES）及其背景。
ICP-AES是一种广泛应用于元素分析的技术。
通过使用电感耦合等离子体源（Inductively Coupled Plasma，ICP），该技术能够提供高灵敏度、高选择性和高稳定性的元素测定。
ICP-AES技术的基本原理是将样品离子化并激发成原子状态，然后测量其发射光谱。
这种离子化和激发过程发生在高温的等离子体环境中，其中气体被离子化，并通过高频电磁场被激发。
激发的原子会一瞬间返回其基态，并且所产生的光谱（称为原子发射光谱）可用于测量样品中的元素含量。
ICP-AES技术具有以下几个优点：首先，其灵敏度非常高。
ICP-AES可以检测到各种元素，从低至纳克级（ng/L）的浓度，这使其在环境、食品、药物等领域得到广泛应用。
其次，ICP-AES还具有元素的选择性。
该技术通过选择适当的光谱线进行测量，可以避免其他干扰物质的不良影响。
此外，ICP-AES还具有较高的分析速度和多元素分析能力。
在ICP-AES分析中，化学试剂的选择非常重要。
化学试剂被用于样品的前处理、放电感应剂以及作为内标物质。
常用的化学试剂包括溶液酸、氧化剂和还原剂等。
溶液酸通常用于提取和降解样品中的目标元素，氧化剂和还原剂则用于改变目标元素的价态以及其他反应。
选择合适的化学试剂可以提高样品前处理的效果，并减少干扰物质的存在。
此外，对于ICP-AES分析的准确性和可重复性也非常重要。
为了确保结果的准确性，需要进行仪器的校准和质量控制。
校准通常通过使用符合国际标准的参考物质进行。
《ScienceAdvances》发现对数周期量子振荡
《ScienceAdvances》发现对数周期量子振荡
2018年11月2日，著名杂志《Science Advances》在线报道了北京大学量子材料科学中心王健教授、谢心澄院士团队在高质量的三维层状拓扑材料ZrT e5单晶中首次发现了一种新规律的量子振荡——随磁场呈对数周期的磁电阻振荡。
该论文《Discovery of log-periodic oscillations in ultraquantum topological materials》指出：
“量子振荡通常是凝聚态物质系统中潜在物理性质的表现。
在这里，我们报告了超量子三维拓扑材料中的一种新型对数周期量子振荡。
超出量子极限（QL），我们观察到对数周期振荡涉及高质量单晶ZrTe5磁阻的多达五个振荡周期（五个峰和五个下降），实际上显示了离散尺度不变性的最明显特征（DSI）。
此外，理论分析表明，两体准约束状态可以反应出DSI特征。
我们的工作为QL以外的拓扑材料的基态提供了新的视角。
”
Qubitlab_Peter | 整理
Yoking | 编辑
量豆豆 | 校对。
可调谐激光 2-2
固定波长激光晶体掺Ln3+ 4f电子跃迁，几个固定波长，红外 晶体场较强时，电子-声子耦合加强 5d 4f跃迁可能成为宽带能级结构 Ce3+唯一紫外区可调谐激光晶体 Ln2+,Sm2+已在可见光谱区可调谐
掺过渡金属离子晶体
掺钛离子激光晶体
基质晶体
蓝宝石、紫翠宝石、钙钛矿
稳定性好 高导热率 熔点高（2050℃） 硬度大(9级)
掺钛蓝宝石晶体结构
三角对称性 立方场、三角场 1s22s22p63s23p63d 一个3d价电子
掺钛蓝宝石晶体能级分裂
立方场》三角场 电子能级与声子耦合 宽带能级结构 最低激发态寿命3.2μs
晶体取向、端面布角切割
掺钛蓝宝石的品质因数
红外谱区存在吸收 增益峰红移 Ti3+-Ti4+离子对模型 π 分量吸收小于σ 分量 退火处理
掺钛蓝宝石的品质因数
吸收系数 品质因数（Figure of Merit, FOM）
FOM 晶体对泵浦光吸收系数 晶体对激光峰值波长吸 收系数
掺钛蓝宝石晶体能级图
声子参与弛豫 吸收谱有两个吸收峰 发射谱单峰
吸收谱的偏振特性
π 分量偏振方向与c轴平行 σ 分量偏振方向与c轴垂直 π 分量吸收远大于σ 分量 较高的线偏振光泵浦效率
发射谱的偏振特性
2T2能级的分裂与展宽
短波长与吸收谱重叠 具有偏振特性 可获线偏振激光输出
掺其它过渡金属离子激光晶体
掺钴（Co2+）离子晶体
SelectiveSynthesisofSingle-Crystalline_Rhombic_Dodecahedral,_Octahedral,_and_Cubic_Gold_Nanocrystals
Selective Synthesis of Single-Crystalline Rhombic Dodecahedral,Octahedral,and Cubic Gold NanocrystalsWenxin Niu,†,‡Shanliang Zheng,§Dawei Wang,†,‡Xiaoqing Liu,†,‡Haijuan Li,†,‡Shuang Han,†,‡Jiuan Chen,†,‡Zhiyong Tang,*,§and Guobao Xu*,†State Key Laboratory of Electroanalytical Chemistry,Changchun Institute of Applied Chemistry,and Graduate Uni V ersity of the Chinese Academy of Sciences,Chinese Academy of Sciences,Changchun 130022,China,and National Center for Nanoscience and Technology,Beijing 100190,ChinaReceived June 6,2008;E-mail:zytang@.;guobaoxu@Abstract:This paper reports a versatile seed-mediated growth method for selectively synthesizing single-crystalline rhombic dodecahedral,octahedral,and cubic gold nanocrystals.In the seed-mediated growth method,cetylpyridinium chloride (CPC)and CPC-capped single-crystalline gold nanocrystals 41.3nm in size are used as the surfactant and seeds,respectively.The CPC-capped gold seeds can avoid twinning during the growth process,which enables us to study the correlations between the growth conditions and the shapes of the gold nanocrystals.Surface-energy and kinetic considerations are taken into account to understand the formation mechanisms of the single-crystalline gold nanocrystals with varying shapes.CPC surfactants are found to alter the surface energies of gold facets in the order {100}>{110}>{111}under the growth conditions in this study,whereas the growth kinetics leads to the formation of thermodynamically less favored shapes that are not bounded by the most stable facets.The competition between AuCl 4-reduction and the CPC capping process on the {111}and {110}facets of gold nanocrystals plays an important role in the formation of the rhombic dodecahedral (RD)and octahedral gold nanocrystals.Octahedral nanocrystals are formed when the capping of CPC on {111}facets dominates,while RD nanocrystals are formed when the reduction of AuCl 4-on {111}facets dominates.Cubic gold nanocrystals are formed by the introduction of bromide ions in the presence of CPC.The cooperative work of cetylpyridinium and bromide ions can stabilize the gold {100}facet under the growth condition in this study,thereby leading to the formation of cubic gold nanocrystals.1.IntroductionThe properties of noble-metal nanocrystals are dictated by their sizes and shapes.1-3Therefore,size-and shape-controlled synthesis of noble-metal nanocrystals is essential for uncovering and understanding their intrinsic properties,which will conse-quently enable us to exploit them for catalytic,plasmonic,sensing,and spectroscopic applications.1-6Over the past decade,great progress has been made in crystallographic control over the nucleation and growth of gold nanocrystals.Most efforts thus far have been focused on the synthesis of octahedral and cubic gold nanocrystals bounded by {111}and {100}facets.7-10Synthesis of gold nanocrystals bounded by {110}facets has seldom been reported because the surface energy of the bare {110}facets is higher than those of bare {111}and {100}facets.11In principle,the shape of single-crystalline gold crystals bounded completely by equivalent {110}facets is supposed to be rhombic dodecahedral (RD),12,13i.e.,such a crystal would be a convex polyhedron with 12rhombic faces that has eight vertices where three faces meet at their obtuse angles and six vertices where four faces meet at their acute angles (Figure 1).14RD gold crystals have been observed in minerals,12and RD gold nano-and microcrystals have also been observed in chemical syntheses.15,16However,the rational synthesis of uniform RD gold nanocrystals in high yield has not been reported to date and is still a challenge that requires exquisite crystal-growth control.Although several parameters have been revealed to greatly affect the growth mode of metal nanocrystals,the exact mechanisms for the shape-controlled synthesis of metal nanoc-†Changchun Institute of Applied Chemistry.‡Graduate University of the Chinese Academy of Sciences.§National Center for Nanoscience and Technology.(1)Murphy,C.J.;Sau,T.K.;Gole,A.M.;Orendorff,C.J.;Gao,J.;Gou,L.;Hunyadi,S.E.;Li,T.J.Phys.Chem.B 2005,109,13857.(2)Wiley,B.;Sun,Y.;Xia,Y.Acc.Chem.Res.2007,40,1067.(3)Tao,A.R.;Habas,S.;Yang,P.Small 2008,4,310.(4)Narayanan,R.;El-Sayed,M.A.J.Am.Chem.Soc.2004,126,7194.(5)Liz-Marzan,ngmuir 2006,22,32.(6)Rosi,N.L.;Mirkin,C.A.Chem.Re V .2005,105,1547.(7)Kim,F.;Connor,S.;Song,H.;Kuykendall,T.;Yang,P.Angew.Chem.,Int.Ed.2004,43,3673.(8)Sau,T.K.;Murphy,C.J.J.Am.Chem.Soc.2004,126,8648.(9)Seo,D.;Park,J.C.;Song,H.J.Am.Chem.Soc.2006,128,14863.(10)Li,C.;Shuford,K.L.;Park,Q.-H.;Cai,W.;Li,Y.;Lee,E.J.;Cho,O.C.Angew.Chem.,Int.Ed.2007,46,3264.(11)Wang,Z.L.J.Phys.Chem.B 2000,104,1153.(12)Taber,S.Am.Mineral.1948,33,482.(13)Francis,C.A.Rocks Miner.2004,79,24.(14)Weisstein,E.W.CRC Concise Encyclopedia of Mathematics ,2nd ed.;CRC Press:Boca Raton,FL,2003;p 2546.(15)Liu,X.;Wu,N.;Wunsch,B.H.,Jr.;Stellacci,F.Small 2006,2,1046.(16)Chen,Y.;Gu,X.;Nie,C.-G.;Jiang,Z.-Y.;Xie,Z.-X.;Lin,C.-J.Chem.Commun.2005,4181.Published on Web 12/22/200810.1021/ja804115r CCC:$40.75 2009American Chemical SocietyJ.AM.CHEM.SOC.2009,131,697–7039697rystals are still not well-understood.3Most of the synthetic methods remain empirical,and understanding their growth mechanisms is still a challenging task.The seed-mediated growth method separates the nucleation and growth stages of nanocrystals,which provides better control over the size,size distribution,and shape evolution of the nanoparticles.1,17A typical seed-mediated growth process involves the preparation of small metal nanoparticles and their subsequent growth in reaction solutions containing metal salts,reducing agents,and surfactants.During the growth procedure,the crystal structures of the metal nanocrystals grown from small seeds are fluctuant.18The small seeds may grow into single-crystalline,twinned,or multitwinned structures,19leading to the formation of polydis-perse nanostructures.The shape evolution of metal nanocrystals from seeds with different crystal structures is quite different,20,21which blurs our understanding of the mechanisms of the growth process.To preserve the single-crystalline nature of the seeds during the seed-mediated growth process,one has to judiciously select appropriate adsorbents 20,22or manipulate the growth kinetics.8Therefore,development of a general strategy that can selectively produce single-crystalline metal nanocrystals without the need for elaborate selection of appropriate adsorbents or manipulation of the growth kinetics could enable us to study the detailed correlations between growth conditions and the shapes of the single-crystalline nanocrystals.In this study,we developed a versatile seed-mediated growth method to selectively synthesize single-crystalline RD,octahe-dral,and cubic gold nanocrystals through manipulation of the growth kinetics and selection of appropriate adsorbates.Single-crystalline gold nanocrystals with diameters of 41.3nm and capped by cetylpyridinium chloride (CPC)were prepared and explored as the seeds in the seed-mediated growth method.The single-crystalline nature and relatively large sizes of the CPC-capped seeds can fix the structure of the final nanocrystals as single-crystalline,enabling us to carefully study the parametersthat affect the formation of the gold nanocrystals with varying shapes.Several important parameters that affect the shape evolutions of the gold nanocrystals are revealed,and the growth mechanisms are explained in terms of surface energy and growth kinetics.2.Experimental Section2.1.Materials.Chloroauric acid tetrahydrate (HAuCl 4·4H 2O),sodium borohydride (NaBH 4),and cetyltrimethylammonium bro-mide (CTAB)were obtained from Sinopharm Chemical Reagent Co.,Ltd.L -Ascorbic acid,silver nitrate (AgNO 3),and potassium bromide (KBr)were obtained from Beijing Chemical Reagent Company.CPC was obtained from Shanghai Sangon Company.All of the chemicals were of analytical grade and used without further purification.Doubly distilled water was used throughout the experiments.2.2.Synthesis of Gold Nanorods. 2.2.1.Preparation of ∼1.5nm CTAB-Capped Gold Seeds.A 125µL aliquot of 10mM HAuCl 4solution was added to 5mL of 100mM CTAB solution at 30°C.After this combination was gently mixed,0.3mL of 10mM ice-cold NaBH 4solution was added all at once,followed by rapid inversion mixing for 2min.22,23The CTAB-capped gold seed solution was stored at 30°C for future use.2.2.2.Synthesis of Gold Nanorods.In sequence,2mL of 10mM HAuCl 4solution,240µL of 10mM AgNO 3solution,320µL of freshly prepared 100mM ascorbic acid solution,and 48µL of the ∼1.5nm CTAB-capped gold seed solution were added to 40mL of 100mM CTAB solution at 30°C.The solution was thoroughly mixed after each addition.22,23Finally,the gold nanorod solution was left undisturbed and aged for 2h for further use.2.3.Synthesis of the CPC-Capped Gold Seeds from Gold Nanorods.2.3.1.Secondary Overgrowth of Gold Nanorods.A 30mL aliquot of the as-synthesized gold nanorod solution was centrifuged (12000rpm,10min)and redispersed in water.Subsequently,the solution was centrifuged (12000rpm,10min)again and redispersed in 30mL of 10mM CTAB solution at 40°stly,1.5mL of 10mM HAuCl 4solution and 0.3mL of 100mM ascorbic acid solution were added in sequence and mixed thoroughly.The mixture was allowed to react at 40°C for 1h.2.3.2.Synthesis of the CPC-Capped Gold Seeds.The CPC-capped gold seeds were prepared by transformation of the over-grown gold nanorods to near-spherical nanoparticles.24Briefly,the overgrown gold nanorod solution was centrifuged (12000rpm,10min)and redispersed in 30mL of 10mM CTAB solution.Next,at 40°C,0.6mL of 10mM HAuCl 4solution was added.After the solution was gently mixed,it was left undisturbed and aged for 12h.The solution was then washed three times with 100mM CPC solution by centrifugation (12000rpm,10min)and dissolution and finally dispersed in 30mL of 100mM CPC solution.We designated these nanoparticles as the CPC-capped seeds.2.4.Seed-Mediated Growth of Three Types of Gold Nanocrystals.In a typical synthesis of the RD gold nanocrystals,100µL of 10mM HAuCl 4solution,200µL of freshly prepared 100mM ascorbic acid solution,and 200µL of the CPC-capped seed solution were added to 5mL of 10mM CPC solution at 30°C in sequence.The solution was thoroughly mixed after each addition.The reaction was stopped after 2h by centrifugation (12000rpm,10min).The gold nanocrystal solution was washed twice with water and concentrated for characterization by electron microscopy.In a typical synthesis of the octahedral gold nanocrystals,100µL of 10mM HAuCl 4solution,13µL of freshly prepared 100mM ascorbic acid solution,and 200µL of the CPC-capped seed solution were added to 5mL of 100mM CPC solution at 30°C in(17)Murphy,C.J.;Gole,A.M.;Hunyadi,S.E.;Orendorff,C.J.Inorg.Chem.2006,45,7544.(18)Elechiguerra,J.L.;Reyes-Gasga,J.;Yacaman,J.M.J.Mater.Chem.2006,16,3906.(19)Wu,H.-Y.;Huang,W.-L.;Huang,M.H.Cryst.Growth Des.2007,7,831.(20)Liu,M.;Guyot-Sionnest,G.J.Phys.Chem.B 2005,109,22192.(21)Lim,B.;Xiong,Y.;Xia,Y.Angew.Chem.,Int.Ed.2007,46,9279.(22)Nikoobakht,B.;El-Sayed,M.A.Chem.Mater.2003,15,1957.(23)Sau,T.K.;Murphy,ngmuir 2004,20,6414.(24)Rodriguez-Fernandez,J.;Perez-Juste,J.;Mulvaney,P.;Liz-Marzan,L.M.J.Phys.Chem.B 2005,109,14257.Figure 1.Geometrical models of rhombic dodecahedra:(A)overall view;(B)view perpendicular to one of the rhombic faces;(C)view centered on one of the vertices where three faces meet at their obtuse angles;(D)view centered on one of the vertices where four faces meet at their acute angles.698J.AM.CHEM.SOC.9VOL.131,NO.2,2009A R T I C L E S Niu et al.sequence.The solution was thoroughly mixed after each addition. The reaction was stopped after2h by centrifugation(12000rpm, 10min).In a typical synthesis of the cubic gold nanocrystals,500µL of 100mM KBr solution,100µL of10mM HAuCl4solution,13µL of freshly prepared100mM ascorbic acid solution,and200µL of the CPC-capped seed solution were added to5mL of100mM CPC solution at30°C in sequence.The solution was thoroughly mixed after each addition.The reaction was stopped after2h by centrifugation(12000rpm,10min).2.5.Instrumentation.Scanning electron microscopy(SEM) images were taken using an FEI XL30ESEM FEG scanning electron microscope operating at25kV.Transmission electron microscopy(TEM)and selected-area electron diffraction(SAED) studies were performed on a FEI Tecnai G220S-TWIN transmis-sion electron microscope operated at200kV.A drop of the concentrated nanocrystal solution was deposited on ITO glass or a TEM grid for SEM or TEM measurements,respectively.During natural evaporation of water,part of the nanocrystals migrated to the edge of the drop and formed a solid ring.SEM observations revealed that ordered assemblies mainly existed at the coffee-ring region,while random assemblies mainly existed at the center. UV-vis extinction spectra were taken at room temperature on a CARY500Scan UV-vis-near-IR spectrophotometer using a quartz cuvette with an optical path of1cm.X-ray diffraction(XRD) measurements were obtained with a Rigaku D/MAX-2500instru-ment(Cu K R1radiation)operated at50kV and250mA over a range of30-90°by step scanning with a step size of0.02°.3.Results and Discussion3.1.Preparation and Characterization of the CPC-Capped Gold Seeds.Gold nanorods were overgrown and then oxidized by Au(III)-CTAB complexes to prepare the CPC-capped gold seeds.The oxidation occurred preferentially at the ends of the overgrown gold nanorods and eventually led to the formation of near-spherical nanoparticles.24These near-spherical nano-particles werefinally dispersed in100mM CPC solution and designated as the CPC-capped gold seeds.As shown in Figure 2,the average width,length,and aspect ratio of the gold nanorods are27.2nm,58.8nm,and2.2,respectively,and the average width,length,and aspect ratio of the overgrown gold nanorods are32.4nm,63.7nm,and2.0,respectively;the CPC-capped gold seeds have an average diameter of41.3nm and a size distribution of5.4%.The detailed morphology and struc-tures of the CPC-capped seeds were studied through TEM. Figure3A shows that the shapes of the CPC-capped gold seeds are slightly ellipsoidal rather than perfectly spherical.Therefore, the average diameter of the seeds is bigger than the average width of the overgrown nanorods from which they originate. The SAED pattern and high-resolution TEM(HRTEM)image of a single CPC-capped seed demonstrate that the CPC-capped seeds are single-crystalline(Figure3B,C).The process of preparing the CPC-capped seeds was also studied by UV-vis spectroscopy.The UV-vis extinction spectra of the gold nanorods,overgrown gold nanorods,and CPC-capped seeds are shown in Figure2D.The two peaks in the UV-vis extinction spectra of the gold nanorods and overgrown gold nanorods can be attributed to the transverse and longitudinal plasmon modes of gold nanorods.22The blue shift in the longitudinal plasmon mode of the overgrown nanorods confirms a decrease in their aspect ratios.25The UV-vis extinction spectrum of the CPC-capped seeds has only one peak[curve(c)in Figure2D],which confirms their near-spherical morphology.3.2.Synthesis of Single-Crystalline RD,Octahedral,and Cubic Gold Nanocrystals.3.2.1.Synthesis and Characterization of RD Gold Nanocrystals.Synthesis of RD gold nanocrystals was performed at30°C.Typically,100µL of10mM HAuCl4 solution,200µL of100mM ascorbic acid solution,and200µL of the CPC-capped seed solution were added to5mL of10 mM CPC solution in sequence.The reaction was stopped after 2h by centrifugation.Figure4A,B shows SEM images of orderly assembled and randomly distributed RD gold nanoc-rystals,respectively.In the ordered assembly of RD gold nanocrystals,the RD gold nanocrystals are in the orientation shown in Figure1C.From the randomly distributed RD gold nanocrystals,the geometrical shapes of these gold nanocrystals can be viewed from different directions and identified as RD, i.e.,bounded by12equivalent rhombic faces(Figure S1in the Supporting Information).14Figure4C shows the TEM image of the RD gold nanocrystals.Most of the RD nanocrystals tend to lieflat and exhibit elongated hexagonal shapes.For aflat-(25)Tsung,C.-K.;Kou,X.;Shi,Q.;Zhang,J.;Yeung,M.H.;Wang,J.;Stucky,G.D.J.Am.Chem.Soc.2006,128,5352.Figure2.SEM images of(A)the gold nanorods,(B)the overgrown goldnanorods,and(C)the CPC-capped gold seeds(scale bars:200nm).(D)UV-vis extinction spectra of(a)the gold nanorods,(b)the overgrown goldnanorods,and(c)the CPC-capped gold seeds(each spectrum is normalizedagainst the intensity of its strongest peak).Figure3.(A)TEM image of the CPC-capped gold seeds.(B)TEM imageand corresponding SAED pattern of a single CPC-capped seed.(C)HRTEMimage of the CPC-capped seed in(B).J.AM.CHEM.SOC.9VOL.131,NO.2,2009699 Dodecahedral,Octahedral,and Cubic Gold Nanocrystals A R T I C L E Slying RD gold nanocrystal,the top and bottom {110}faces of the RD gold nanocrystal are parallel to the substrate.Directing the electron beam perpendicular to the upper face of the flat-lying RD nanocrystal produces the typical SAED pattern of a gold crystal along the [011]zone axis,12,13,26as shown in the inset of Figure 4D.The HRTEM and corresponding SAED images of gold nanocrystals viewed from different directions further confirm their RD shapes (Figure S2in the Supporting Information).It should be pointed out that the XRD pattern of the RD gold nanocrystals (Figure S3in the Supporting Informa-tion)does not have an abnormally intense (220)peak because SEM observations (Figure 4A,B)reveal that not all of the RD nanocrystals lie flat on the substrate.The TEM image in Figure 4D also reveals that the corners of the RD gold nanocrystal are slightly stretched-out,which indicates that the faces of the RD nanocrystals are not perfectly flat.In order to clearly distinguish the surface morphologies of the RD nanocrystals,larger RD nanocrystals were also synthe-sized by reducing the added volume of the seed solution to 25µL.As shown in Figure 5,the faces of the RD nanocrystals are concave with relatively flat center parts parallel to the ideal {110}facets.Therfore,although the gold nanocrystals in Figures 4and 5take an RD overall shape,their faces are not perfect {110}facets,and the center part of each facet is supposed to be a {110}facet.3.2.2.Synthesis and Characterization of Octahedral Gold Nanocrystals.Octahedral gold nanocrystals were synthesizedunder conditions similar to those for the synthesis of the RD gold nanocrystals in Figure 4,except that the concentration of CPC was increased from 10to 100mM and the volume of 100mM ascorbic acid solution was decreased from 200to 13µL.SEM and TEM images of the octahedral gold nanocrystals are presented in Figure 6A,B,respectively.The SAED study indicates that the octahedral gold nanocrystal is a piece of single crystal bounded by {111}facets (Figure 6C,D).9,103.2.3.Synthesis and Characterization of Cubic Gold Nano-crystals.Cubic gold nanocrystals were produced when 0.5mLof 100mM KBr solution was introduced while the other conditions were kept the same as those in the synthesis of the octahedral gold nanocrystals.Figure 7A,B shows the SEM and TEM images of the cubic gold nanocrystals,respectively,and Figure 7C,D shows the TEM image and corresponding SAED pattern of a single cubic gold nanocrystal.The square spot array of the SAED pattern indicates that the cubic gold nanocrystal is a single crystal bounded by {100}facets.7,9Cubic gold nanocrystals are also produced when only 0.05mL of 100mM KBr solution is introduced,as shown in Figure S4in the Supporting Information.3.2.4.Average Edge Lengths,Size Distributions,Yields,and Corresponding Optical Properties of the Gold Nano-crystals.Table 1summarizes the average sizes,size distributions,and yields of the gold nanocrystals presented in Figures 4,6,and 7.All three types of gold nanocrystals are prepared in high yields with good pared with the CPC-capped seeds,the final nanocrystals have improved monodis-(26)Wang,Z.L.Reflection Electron Microscopy and Spectroscopy forSurface Analysis ;Cambridge University Press:Cambridge,U.K.,1996;Appendix D.Figure 4.SEM images of (A)orderly assembled and (B)randomly distributed RD gold nanocrystals (scale bars:200nm).(C)TEM image of the RD gold nanocrystals (scale bar:200nm).(D)TEM image and corresponding SAED pattern of a single flat-lying RD gold nanocrystal recorded along the [011]zone axis (scale bar:50nm).Figure 5.SEM images of larger RD gold nanocrystals at differentmagnifications [scale bars:(A)1µm,(B)500nm,(C)200nm].(D)RD geometrical models with typical orientations corresponding to RD gold nanocrystals at the same positions in (C).Figure 6.(A)SEM image of octahedral gold nanocrystals (scale bar:200nm).(B)TEM image of octahedral gold nanocrystals (scale bar:100nm).(C)TEM image and (D)corresponding SAED pattern of a single flat-lyingoctahedral gold nanocrystal recorded along the [1j 11]zone axis (scale bar:20nm).700J.AM.CHEM.SOC.9VOL.131,NO.2,2009A R T I C L E S Niu et al.persity.In seed-mediated growth procedures,the improvement in the monodispersity is attributed to the “self-focusing”tendency that small particles grow faster than larger ones,causing the final sizes of the nanocrystals to become uniform.27,28Such observations are consistent with previous reports that the monodispersity of the grown nanoparticles is better than that of the seeds.29-31It is well-known that noble metal nanoparticles exhibit size-and shape-dependent optical properties arising from surface plasmon resonances.32As shown in Figure 8,the UV -vis extinction spectra of the RD,octahedral,and cubic gold nanocrystals show peaks at 582,568,and 551nm,respectively.The differences in the UV -vis extinction spectra may result from the differences in the sizes,shapes,and outstretched or truncated corners of the gold nanocrystals.3.3.Growth Mechanisms of the Gold Nanocrystals.In a seed-mediated growth procedure,several parameters are simulta-neously responsible for the final shapes of the gold nanocrys-tals.17Hence several control experiments are conducted to elucidate the growth mechanisms of the gold nanocrystals.In the nucleation stage,the size and crystal structure of seeds are proved to be important for the formation of single-crystalline structures of the gold nanocrystals.In the growth stage,surfactants,growth kinetics,and adsorbates are found to determine the final shapes of the resultant single-crystalline gold nanocrystals.3.3.1.The Importance of the Size and Crystal Structure of the Seeds.To investigate how the size and crystal structureof the seeds affect the growth of gold nanocrystals,another two types of seeds commonly used in the seed-mediated growth method were adopted here (under the same growth conditions)in addition to the CPC-capped gold seeds.These two types of seeds were ∼3nm citrate-capped twinned gold seeds and ∼1.5nm CTAB-capped single-crystalline gold seeds.20Among the three types of seeds,the ∼1.5nm CTAB-capped single-crystalline seed solution contains bromide ions,and bromide ions from this seed solution may affect the growth of gold nanocrystals.33Therefore,we intentionally adopted the growth conditions with the addition of KBr to counteract the influence of the presence or absence of bromide ions in different seed solutions.SEM images of the gold nanocrystals synthesized with the different types of seeds are shown in Figure 9,and their corresponding shape distributions are summarized in Table S1in the Supporting Information.When the CPC-capped single-crystalline gold seeds were used,cubic gold nanocrystals were produced in high yield (95.2%).In contrast,only 4.0%of the products were cubic nanocrystals when the ∼3nm twinned nanoparticles were used,and 26.1%of the products were cubic nanocrystals when ∼1.5nm single-crystalline nanoparticles were used.These results provide evidence that both the single-crystalline nature and the relatively large sizes of the CPC-capped seeds play important roles in the growth of single-crystalline gold nanocrystals with high yields.It is believed that the crystal structure of the seeds fluctuates at very small sizes,whereas their structure will be fixed as single-crystalline or multitwinned as the size of the crystals increases.18,34Because of their relatively large sizes,the CPC-capped single-crystalline seeds can avoid twinning during the growth process,enabling us to study the parameters that affect the growth of the gold nanocrystals.It should also be noted that the present procedure for preparing the CPC-capped seeds is somewhat tedious.Ongoing efforts in our group are being directed toward finding simpler methods for synthesis of high-quality single-crystalline gold seeds with relatively large sizes.(27)Reiss,H.J.Chem.Phys.1951,19,482.(28)Peng,X.G.;Wickham,J.;Alivisatos,A.P.J.Am.Chem.Soc.1998,120,5343.(29)Brown,K.R.;Walter,D.G.;Natan,M.J.Chem.Mater.2000,12,306.(30)Henglein,ngmuir 1999,15,6738.(31)Jana,N.R.;Gearheart,L.;Murphy,ngmuir 2001,17,6782.(32)Xia,Y.;Halas,N.J.MRS Bull.2005,30,338.(33)Ha,T.H.;Koo,H.J.;Chung,B.H.J.Phys.Chem.C 2007,111,1123.(34)Im,S.H.;Lee,Y.T.;Wiley,B.;Xia,Y.Angew.Chem.,Int.Ed.2005,44,2154.Figure 7.(A)SEM image of cubic gold nanocrystals (scale bar:500nm).(B)TEM image of cubic gold nanocrystals (scale bar:100nm).(C)TEM image and (D)corresponding SAED pattern of a single flat-lying cubic gold nanocrystal recorded along the [001]zone axis (scale bar:20nm).Table 1.Average Edge Lengths (L av ),Size Distribution Standard Deviations (σ),and Yields of the RD,Octahedral,and Cubic Gold NanocrystalsshapeL av (nm)σ(%)yield (%)figure no.RD53.4 5.3∼1004octahedral 59.8 4.197.26cubic 55.7 4.496.17Figure 8.UV -vis extinction spectra of (A)the RD gold nanocrystals inFigure 4,(B)the octahedral gold nanocrystals in Figure 6,and (C)the cubic gold nanocrystals in Figure 7(each spectrum is normalized against the intensity of its strongest peak).J.AM.CHEM.SOC.9VOL.131,NO.2,2009701Dodecahedral,Octahedral,and Cubic Gold Nanocrystals A R T I C L E S3.3.2.Surface Energies of Different Gold Crystallographic Facets in the Presence of CPC.Surface energies associated withdifferent gold crystallographic facets usually increase in the order γ{111}<γ{100}<γ{110}.11,35In a solution-phase synthesis,adsorbates (including surfactants,polymers,small molecules,and atomic adsorbates)can interact selectively with different metal crystal facets and alter their surface energies.3It has been reported that gold nanorods have {110}side facets.20,36These {110}facets disappear during overgrowth in the presence of CTAB or poly(vinyl pyrrolidone).37,38In contrast,CPC can selectively stabilize the {110}facets of gold,and thus,RD gold nanocrystals can exist as final products.The preparation of octahedral gold nanocrystals indicates that CPC can also stabilize the {111}facets of gold.Through a comparison between the surface structures of the larger RD and octahedral gold nanoc-rystals shown in Figures 5and 10,respectively,we found that the faces of the octahedral gold nanocrystals are flat and smooth but that the faces of the RD gold nanocrystals are not well-defined {110}facets,which suggests that CPC stabilizes {110}facets relatively poorly.Moreover,octahedral gold nanocrystals bounded by {111}facets are obtained at relatively high CPC concentrations,suggesting that the enhanced capping of CPC promotes the formation of {111}facets of gold.These observa-tions suggest that the gold {111}facets should be more stable than gold {110}facets in the presence of CPC under the growth conditions in this study.Since gold nanocrystals bounded by {100}facets are not observed in the presence of CPC,we suppose that gold {100}facets tend to disappear during the growth procedure,and it should be the most unstable low-index facet of gold in the presence of CPC.Therefore,it is reasonable to assume that CPC alters the surface energies of gold facets,ordering them as γ{111}<γ{110}<γ{100}under the growth conditions in this study.The selective interactions of CPC with different gold facets are responsible for the alteration.3.3.3.Growth Kinetics of the RD and Octahedral Gold Nanocrystals.The above surface-energy considerations suggestthat the RD gold nanocrystal is not the thermodynamically most favored shape.The formation of thermodynamically less favored shapes of nanocrystals are generally governed by growth kinetics.39-41In the case of the selective synthesis of RD and octahedral gold nanocrystals,growth kinetics and the capping effect of CPC must be taken into account simultaneously in order to understand their growth mechanisms.Several control experiments were conducted to investigate the formation mechanisms of RD and octahedral gold nanoc-rystals.RD gold nanocrystals could still be prepared when the concentration of CPC was increased to 100mM and the volume of 100mM ascorbic acid solution was between 200and 25µL,while other conditions were the same as those in the synthesis of the RD gold nanocrystals in Figure 4.The corresponding SEM images of the RD nanocrystals are shown in Figure 11A,B.When the volume of ascorbic acid solution was further reduced to 13µL,octahedral gold nanocrystals were produced,as shown in Figure 6.These results indicate that the competition between AuCl 4-reduction and the CPC capping process on the {111}and {110}surfaces plays an important role.Octahedral gold nanocrystals bounded by {111}facets were obtained at relatively high CPC concentrations,suggesting that the capping of CPC promotes the formation of {111}facets of gold.At relatively high ascorbic acid concentrations,RD nanocrystals were(35)Xiong,Y.;Wiley,B.;Xia,Y.Angew.Chem.,Int.Ed.2007,46,7157.(36)Wang,Z.L.;Mohamed,M.B.;Link,S.;El-Sayed,M.A.Surf.Sci.1999,440,L809.(37)Xiang,Y.;Wu,X.;Liu,D.;Feng,L.;Zhang,K.;Chu,W.;Zhou,W.;Xie,S.J.Phys.Chem.C 2008,112,3203.(38)Carbo-Argibay,E.;Rodriguez-Gonzalez,B.;Pacifico,J.;Pastoriza-Santos,I.;Perez-Juste,J.;Liz-Marzan,L.M.Angew.Chem.,Int.Ed.2007,46,8983.(39)Petroski,J.M.;Wang,Z.L.;Green,T.C.;El-Sayed,M.A.J.Phys.Chem.B 1998,102,3316.(40)Xiong,Y.;Cai,H.;Wiley,B.J.;Wang,J.;Kim,M.J.;Xia,Y.J.Am.Chem.Soc.2007,129,3665.(41)Tao,A.;Sinsermsuksakul,P.;Yang,P.Angew.Chem.,Int.Ed.2006,45,4597.Figure 9.SEM images of gold nanocrystals synthesized with different types of seeds:(A)41.3nm CPC-capped single-crystalline gold seeds;(B)∼3nmcitrate-capped twinned gold seeds;(C)∼1.5nm CTAB-capped single-crystalline gold seeds (all scale bars:500nm).The gold nanocrystals were synthesized by adding 50µL of 100mM KBr solution,100µL of 10mM HAuCl 4solution,15µL of 100mM ascorbic acid solution,and the corresponding amount of seed solution (200µL for the CPC-capped seed solution,1µL for the ∼3nm citrate-capped twinned seed solution,and 0.02µL for the ∼1.5nm CTAB-capped single-crystalline seed solution)to 5mL of 100mM CPC solution at 30°C.Figure 10.SEM image of larger octahedral gold nanocrystals synthesizedwith 25µL of the CPC-capped seed solution added (scale bar:200nm).702J.AM.CHEM.SOC.9VOL.131,NO.2,2009A R T I C L E S Niu et al.。
通过1,3-偶极环加成反应合成3-吡咯螺环氧化吲哚的研究进展
通过1,3-偶极环加成反应合成3-吡咯螺环氧化吲哚的研究进展周英;张文会;张敏;彭礼军;黄俊飞;杨超;刘雄利;余章彪【摘要】作为一种重要的天然生物碱,吡咯螺环氧化吲哚骨架一直是天然产物化学和药物化学领域里的研究热点.由于含吡咯螺环氧化吲哚骨架分子广泛具有抗氧化、抗肿瘤等生物活性,近年来对其进行全合成和衍生化合成研究也持续升温.以各种取代的氨基酸为原料和各种取代羰基原位产生亚胺叶立德,然后再和α,β-不饱和烯烃发生1,3-偶极[3+2]环加成反应是合成各种吡咯螺环氧化吲哚类化合物的一种有效方法.本文对这一合成方法在近几年的研究进展进行了综述.【期刊名称】《山地农业生物学报》【年(卷),期】2015(034)002【总页数】6页(P9-13,46)【关键词】亚胺叶立德;1,3-偶极环加成反应;吡咯螺环氧化吲哚;综述【作者】周英;张文会;张敏;彭礼军;黄俊飞;杨超;刘雄利;余章彪【作者单位】贵州大学药学院贵州省中药民族药创制工程中心,贵州贵阳550025;贵州大学药学院贵州省中药民族药创制工程中心,贵州贵阳550025;贵州大学药学院贵州省中药民族药创制工程中心,贵州贵阳550025;贵州大学药学院贵州省中药民族药创制工程中心,贵州贵阳550025;贵州大学药学院贵州省中药民族药创制工程中心,贵州贵阳550025;贵州大学药学院贵州省中药民族药创制工程中心,贵州贵阳550025;贵州大学药学院贵州省中药民族药创制工程中心,贵州贵阳550025;贵州大学药学院贵州省中药民族药创制工程中心,贵州贵阳550025【正文语种】中文【中图分类】R914.51 引言由于吡咯螺环氧化吲哚类化合物具有明确或潜在的生物和药物活性，近年来已被大家广泛关注［1］。
例如，spirotryprostatin A(1)［2］，pteropodine(2)［3］，alstonisine(3)［4］，elacomine(4)［5］，horsfiline(5)［6］，formosanine(6)［7］，rychnophylline(7)［8］等都是经典的含具有吡咯螺环氧化吲哚骨架的天然生物碱(见图1)。
姜黄素分子晶体结构__理论说明
姜黄素分子晶体结构理论说明1. 引言1.1 概述姜黄素作为一种活性物质，在药物学和生物学领域引起了广泛的关注。
近年来，研究人员对姜黄素的分子晶体结构进行了深入探究，并尝试从理论上解释其结构与功能之间的关系。
本文将对姜黄素分子晶体结构进行理论说明，并讨论其对姜黄素功能的影响。
1.2 文章结构本文共分为五个部分。
首先，引言部分概述了研究背景和文章结构安排；接着，在第二部分中，介绍了姜黄素的化学特性以及分子晶体的定义和性质；随后，在第三部分中，详细描述了实验方法、条件和观察结果，并进行相关数据验证和讨论；紧接着，第四部分探讨了分子晶体结构与姜黄素功能之间的关系，并提出了结构改进和优化策略建议；最后，在第五部分中总结主要研究结果，并展望未来在该领域的研究方向。
1.3 目的本文旨在通过对姜黄素分子晶体结构的理论解释，揭示其在药物学和生物学中的重要作用，并为分子晶体结构改进和优化提供科学依据。
通过本文的研究，我们希望能够加深对姜黄素分子晶体结构与功能关系的理解，为姜黄素的合理应用提供指导和启示。
同时，本文也为未来相关领域研究者提供了一些展望和建议，以推动该领域的进一步发展。
2. 姜黄素分子晶体结构理论解释：2.1 姜黄素的化学特性：姜黄素是一种来源于姜黄植物根茎中的天然化合物，也称为巴西薑。
它属于二酮类化合物，化学名称为(1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-diene-3,5-dione。
姜黄素具有抗氧化、抗炎、抗菌等多种药理活性，因此引起了广泛的关注。
2.2 分子晶体的定义与性质：分子晶体是由晶格中周期排列的分子所组成的固体结构。
相较于传统晶体，分子晶体具有较低的熔点和热稳定性，同时还表现出光电、导电和吸附等特殊性质。
其晶胞结构通常由分子间作用力（如氢键、范德华力等）决定。
2.3 理论模型与计算方法介绍：研究姜黄素分子晶体结构通常采用量子化学计算方法和密度泛函理论。
周期极化铌酸锂中通信波段纠缠双光子的波长管理方法(英文)
【关键词】光参量器件;偏振纠缠光子对;自发参量下转换;波长管理
【作 者】高士明
【作者单位】浙江大学光及电磁波研究中心
【正文语种】中 文
【中图分类】O437.4
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术 2004(11)
本文链接：/Periodical_bjgydxxb200302014.aspx 授权使用：武汉大学(whdx)，授权号：98892e6f-9f9b-43b3-bc1d-9e61014508e6
制造出具有如下参数的器件：电流增＝醢卢＝２６、％Ｂ＝７Ｖ、，咧≥ｌ ８０ｍＡ、，Ｔ≥２ＧＨｚ，实现了高频大功率，充分 强示出ｓｊ，ｓｉ。一：Ｇｅ，材辩的优越陛．
关键词：ｓｉ／ｓｉ（诗异质结双板晶体管；梳状结构；双台面＿［艺
中围分类号：１Ｎ ２３２．４
文献标识码：Ａ
文章编号：０２５４∞３７（２００３）０２—０１７９一０３
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万方数据
多发射极Si/SiGe异质结晶体管
作者： 作者单位： 刊名：
热熔融自回流法制备硫化物玻璃非线性集成光学波导说明书
第51卷第5期2022年5月Vol.51No.5May 2022光子学报ACTA PHOTONICA SINICA 热熔融自回流方法制备硫化物玻璃非线性集成光学波导（特邀）齐人铎1，翟彦芬2，张巍1，3，黄翊东1，3（1清华大学电子工程系，量子信息前沿科学中心，北京市未来芯片技术高精尖创新中心，北京信息科学与技术国家研究中心，北京100084）（2奥地利半导体实验室，A 9524Villach ，Austria ）（3北京量子信息科学研究院，北京100193）摘要：硫化物玻璃是发展非线性集成光学器件的良好材料，特殊的理化特性使得硫化物玻璃集成光学波导的制备成为研究的难点。
对硫化物玻璃波导的制备工艺进行了综述，重点介绍利用硫化物玻璃在熔融状态下流动性好的特点，采用热熔融自回流方法制备硫化物玻璃波导的工艺。
该方法避免了对硫化物玻璃薄膜完整性的破坏，以及光刻胶显影液对硫化物玻璃材料的腐蚀作用，可以得到高质量的具有小模场面积的倒脊型硫化物玻璃波导。
实验测试表明，采用热熔融自回流方法制备的硫化物玻璃波导具有良好的三阶非线性光学特性和受激布里渊散射特性。
最后，展望了采用该方法发展硫化物玻璃非线性集成光学器件及其片上系统的研究方向和前景。
关键词：硫化物玻璃；非线性光学器件；集成光学波导；三阶光学非线性；受激布里渊散射中图分类号：TN256文献标识码：A doi ：10.3788/gzxb20225105.05513030引言集成光学的概念在20世纪60年代被首次提出，通过将光学器件集成在芯片上，使其具有体积小、稳定性高、功耗低等优势。
经过几十年的发展，集成光学领域已经取得极大进展。
在集成光学器件中引入非线性光学过程，实现光子的产生和调控等功能，一直是集成光学的重要研究方向之一［1-3］。
硫化物玻璃是实现非线性集成光学器件的重要候选材料［4-7］。
硫化物玻璃（Chalcogenide Glass ，ChG ）也称硫系玻璃，是由硫系元素中的硫（S ）、硒（Se ）、碲（Te ）这三种元素中的一种或多种，与其他的元素如砷（As ）、锗（Ge ）、锑（Sb ）等共价结合而形成的非晶态无机玻璃材料［4］。
《X射线和单晶衍射》课件
Laue方程描述了X射线在非 周期性物质中的散射现象。
衍射实验与数据处理
1
X射线单晶衍射实验
通过实验测量晶体中的X射线衍射图样。
2
衍射图样的解析
分析衍射图样来确定晶体结构的信息。
3
结构分析软件的使用
使用计算机软件来解析和处理衍射数据。
X射线衍射在材料科学中的应用
1
晶体结构分析
利用X射线衍射来确定材料的晶体结构。
《X射线和单晶衍射》 PPT课件
欢迎来到《X射线和单晶衍射》PPT课件。在本次课程中，我们将探讨X射线的 原理、产生过程以及在材料科学中的应用，同时也介绍了单晶衍射的基础知 识和数据处理方法。
简介
什么是X射线？
X射线是一种电磁辐射，具有极 短的波长和高能量。
X射线的应用领域
X射线在医学、材料科学、安全 检测等领域有广泛的应用。
什么是单晶衍射
单晶衍射是通过射向晶体的X射 线来研究晶体结构的技术。
X射线的产生
X射线管的工作原理
X射线管通过高压电场和阴极产生电子，然后利用阳极产生X射线。
X射线的产生过程
当快速移动的电子撞击靶材时，产生了X射线。
X射线的特性
X射线的波长和频率
X射线的波长非常短，频率非常高， 能够穿透物质并与之相互作用。
2
孪晶分析
通过X射线衍射研究材料中的孪晶现象。
3
磁性材料中的衍射
利用X射线衍射研究磁性材料的结构和性质。
结论
X射线技术在现代材料科学中的广泛应用
X射线技术在材料科学中起着至关重要的作用，帮助我们研究和理解材料的结构和性质。
学பைடு நூலகம்X射线和单晶衍射的必要性
学习X射线和单晶衍射对于从事材料科学研究和相关领域的人士来说是非常重要的。
氰乙酸合成路线
氰乙酸合成路线氰乙酸是一种常用的有机化合物，广泛应用于医药、农药、染料、涂料等领域。
下面将介绍氰乙酸的合成路线及其相关参考内容。
氰乙酸的合成路线主要有以下几种方法：1. 路线一：氨水与氰化钠反应得到氰化钠，然后与醋酸反应生成氰化乙酸，进而与碱进行中和生成氰乙酸。
反应式如下：NaCN + H2O → NaOH + HCNHCN + CH3COOH → CH3CNO + H2OCH3CNO + NaOH → CH3COONa + HCN相关参考内容：- Gulyaev K.A., Svetlova V.A., Karpov A.M. (2019) Hydrolysis of Aminoacetonitrile in the Salt Systems LiCl–KCN and LiCl–KCN–KF–H2O. Russian Journal of Inorganic Chemistry, 64(3), 345-350. - Pandey R.P. et al. (2019) A Green Approach to Synthesize 2-Hydroxy-5-methyl-3-isopropylcyclohexa-2,5-diene-1,4-dione Using Non-conventional Heating Methods. Journal of Chemical Sciences, 131(6), 1-6.2. 路线二：氰乙醇通过水解反应得到氰乙酸。
反应式如下：CH3CH(OH)CN + H2O → CH3COOH + NH3相关参考内容：- Gilli P., Pretto L., Gilli G. (2009) Acetic Acid Dimer: An Accidental Molecular Sieve. Crystal Growth & Design, 9(11), 5132-5136.- France J.L. et al. (2018) High-Resolution FTIR Spectroscopy of the ν7 and ν12 Modes of trans-Ethyl Methyl Ether. Journal of Physical Chemistry A, 122(37), 7388-7396.3. 路线三：苯甲醛与氰化钠在碱催化下反应，生成苯乙腈，然后苯乙腈在酸催化下经水解生成氰乙酸。
【高分子专业英语翻译】
【高分子专业英语翻译】第五课乳液聚合大部分的乳液聚合都是由自由基引发的并且表现出其他自由基体系的很多特点,最主要的反应机理的不同源自小体积元中自由基增长的场所不同。
乳液聚合不仅允许在高反应速率下获得较高分子量,这在本体聚合中是无法实现或效率低下的,,同时还有其他重要的实用优点。
水吸收了大部分聚合热且有利于反应控制,产物在低粘度体系中获得,容易处理,可直接使用或是在凝聚,水洗,干燥之后很快转化成固体聚合物。
在共聚中,尽管共聚原理适用于乳液体系,单体在水相中溶解能力的不同也可能导致其与本体聚合行为不同,从而有重要的实际意义。
乳液聚合的变化很大,从包含单一单体,乳化剂,水和单一引发剂的简单体系到这些包含有2,3个单体,一次或分批添加,,混合乳化剂和助稳定剂以及包括链转移剂的复合引发体系。
单体和水相的比例允许变化范围很大,但是在技术做法上通常限制在30/70到60/40。
单体和水相比更高时则达到了直接聚合允许的极限,只有通过分批添加单体方法来排除聚合产生的大量的热。
更复杂的是随着胶体数的增加粘度也大大增加,尤其是当水溶性的单体和聚合物易容时,反应结束胶乳浓度降低。
这一阶段常常伴随着通过聚集作用或是在热力学不稳定时凝结作用而使胶粒尺寸增大。
第十课高分子的构型和构象本课中我们将使用根据经典有机化学术语而来的构型和构象这两个词。
构型异构是由于分子中存在一个或多个不对称中心,以最简单的C原子为例,每一碳原子的绝对构型为R型和S型,当存在双键时会有顺式和反式几何异构。
以合成聚合物为例,构型异构的典型问题和R.S型不对称碳原子在主链上的排布有关。
这些不对称碳原子要么来自不对称单体,如环氧丙烷,要么来自对称单体,如乙烯单体,,这些物质的聚合,在每个单体单元中形成至少一个不对称碳原子。
大分子中的构型异构源于侧链上存在不对称的碳原子,例如不对称乙烯单体的聚合,也是可能的,现今已经被广泛研究。
和经典有机化学术语一致,构象,旋转体,旋转异构体,构象异构体,指的是由于分子单键的内旋转而形成的空间排布的不同。
β-烯胺酮类化合物的合成与结构鉴定
β-烯胺酮类化合物的合成与结构鉴定刘丰收;申东升;邓爵安;谭诚【摘要】目的研究合成烯胺酮类化合物的新路线.方法以含活泼甲基、亚甲基的酮为原料.以甲酸乙酯为羰基化试剂,得到多一个醛羰基的酮,再与二甲胺盐酸盐作用,在室温下反应,合成了9个β-烯胺酮类化合物.结果目标化合物经红外光谱、质谱、核磁共振氢谱和单晶衍射确证了结构.结论合成路线起始原料便宜,改进后的工艺操作简单,适合大批量生产.%Objective To establish a new route for the synthesis of β-Enamino ketone. Methods 9 β-Enamino ketones were synthesized at room temperature, using α-methyl ketones as starting materials. via two steps reaction of formylation and ketone-amine condensation. Results The structures of title compounds were confirmedby IR, MS, and 1H-NMR and XRD analysis. Conclusion The improved procedure has the advantage of low costing of starting material. and the convenient simple route, which is suitable for large scale of production.【期刊名称】《广东药学院学报》【年(卷),期】2011(027)001【总页数】4页(P27-30)【关键词】β-烯胺酮;碳负离子;甲酰化【作者】刘丰收;申东升;邓爵安;谭诚【作者单位】广东药学院,医药化工学院,广东,广州,510006;广东药学院,医药化工学院,广东,广州,510006;广东药学院,医药化工学院,广东,广州,510006;广东药学院,医药化工学院,广东,广州,510006【正文语种】中文【中图分类】R914烯胺酮类化合物是一组多功能的合成子,在有机合成中具有非常重要的应用:是合成吡啶、吡咯、吲哚、唑烷、嘧啶酮、喹啉等含氮杂环化合物的关键中间体[1-4];在合成3-氨基糖衍生物类化合物、生物碱类化合物、β-氨基衍生物类化合物中有重要的应用[4-5];氮原子和氧原子的存在使烯胺酮类化合物可以与主族金属或过渡金属形成六元配合物结构,从而成为一类潜在的金属有机配体[6-9]。
自由空间泵浦玻璃微球的光学特性
Supported by National Natural Science Foundation of China(61605094) ; The K. C. Wong Magna Fund in Ningbo University, China
DING Hai-zhen1,2 , WU Yue-hao2∗ , WANG Xun-si1,2
(1. Laboratory of Infrared Materials and Devices, Advanced Technology Research Institute, Ningbo University, Ningbo 315211, China; 2. Faculty of Electrical Engineering and Computer Science, Ningbo University, Ningbo 315211, China) ∗Corresponding Author, E-mail: wuyuehao@ nbu. edu. cn
关 键 词: 自由空间泵浦; 微球激光器; 稀土掺杂; 回廊模 中图分类号: O433. 1 文献标识码: A DOI: 10. 37188 / CJL. 20210109
Optical Characterization of Free-space Coupled Microsphere Resonators
图 1(a)仿真模型使用的碲酸盐玻璃微球中 未加入有源掺杂物质,因此其内部形成的电场 分布由从自由空间导入微球的泵浦光形成。 从 图 1(a)可见,微球与空气交界面附近形成了类 似高阶回廊模( 径向量子数 n > 1) 的电场分布, 表明有部分折射进入微球的泵浦光以多次反射 的方式被限制在微球内部。 从图中也可观察到 明显的折射漏光现象。 这是因为由折射导入微 球的泵 浦 光 在 微 球 内 部 传 输 时 无 法 形 成 全 反 射。 根据菲涅尔反射基本原理,部分泵浦光能 量会在微球 / 空气界面折射出微球,形成漏光。 泵浦光在微球内部的传输角越接近全反射临界
手性离子液体的合成
收稿:2007年6月,收修改稿:2007年8月 3通讯联系人 e 2mail :gaoge @手性离子液体的合成孙洪海1,2 高 宇3 翟永爱1 张 青1 刘凤岐1 高 歌13(11吉林大学化学学院 长春130023;21大庆师范学院化学系 大庆163712;31北京大学医学部 北京100083)摘 要 近年来,研究者对室温离子液体极为关注,因为这些离子液体可以作为潜在的替代试剂用于有机合成、提取与分离、电化学和材料科学等方面。
在离子液体中,手性离子液体由于可用在手性识别、不对称合成、消旋体的拆分、立体选择聚合、气相色谱、NMR 位移试剂和液晶等方面而受到特别注意。
尽管手性离子液体由于合成困难和费用昂贵而限制了其广泛应用,但其在不对称合成中可作为手性诱导物的应用前景促使研究者不断地去开发新型的手性离子液体。
手性离子液体的制备既可以使用手性源(如氨基酸、胺、氨基醇以及生物碱类),也可以利用不对称合成的手段,其所具有的手性可位于分子的中心、轴或者平面上。
本文综述了手性离子液体合成的最新进展,并按照阴离子或阳离子的种类将其分为咪唑类、吡啶类、铵类和噻唑啉盐类,同时简要介绍了一些新的合成技术。
关键词 手性 离子液体 合成中图分类号:O62113,O64514 文献标识码:A 文章编号:10052281X (2008)0520698215Synthesis of Chiral Ionic LiquidsSun Honghai1,2 Gao Yu 3 Zhai Yongai 1 Zhang Qing 1 Liu Fengqi 1 Gao G e13(1.C ollege of Chemistry ,Jilin University ,Changchun 130023,China ;2.Department of Chemistry ,Daqing NormalUniversity ,Daqing 163712,China ;3.Health Science Center ,Peking University ,Beijing 100083,China )Abstract The interest in using room tem perature ionic liquids (RTI Ls )as potential replacement s olvents for organic synthesis ,extraction ,electrochemistry ,and materials science has increased tremendously in the recent years.Am ong them ,chiral ionic liquids are particularly attractive due to their potential for chiral discrimination ,asymmetric synthesis ,optical res olution of racemates ,stereoselective polymerization ,gas chromatography ,NMR shift reagents and liquid crystals.Even though the difficult syntheses of chiral ionic liquids and their high cost often precluded their use ,the possibility to use chiral ionic liquids as inducers for asymmetric reactions has greatly prom pted researchers to continuely synthesize new chiral s olvents.The chiral ionic liquids are designed either from the chiral pool (aminoacids ,amines ,aminoalcohols ,and alkaloids )or by asymmetric synthesis ;they can bear central ,axial or planar chirality.This review deals mainly with recent advances in synthesis of chiral ionic liquids.Based on the species of cation or anion ,they are classified into imidazolium 2based ,pyridinium 2based ,amm onium 2based ,and thiazolinium 2based etc.In addtion ,s ome new synthesis techniques are als o introduced.K ey w ords chirality ;ionic liquids ;synthesis 以离子液体(I Ls )为溶剂进行有机合成反应是近年来的新兴研究领域之一。