PCT纳米材料结构相变的变温拉曼光谱研究

采用溶胶－凝胶法制备了（Ｐｂ１－ｘＣａ）ＴｉＯ３（ＰＣＴ（ｘ）纳米晶粉和纳米薄膜,变温拉曼光谱显示ＰＣＴ（０）和ＰＣＴ（２０）从铁电四方相向顺电立方相的转变温度分别降低至４３０℃和３３０℃;结果同时表明ＰＣＴ（０）和ＰＣＴ（２０）薄膜的声子频率发生一定程度的红移或蓝移,这归因于纳米材料掺杂引起的诱导效应和晶粒尺寸效应。     

Y掺杂Ba0.90 Sr0.08 Ca0.02 TiO3固溶体纳米晶粒尺寸对其晶体结构的影响

随着电子陶瓷材料向精细、微型、多功能化的方向发展，陶瓷用的粉体晶粒尺寸对物性影响的研究显得越来越重要。钡系钙钛矿结构铁电材料是应用极为广泛的电子陶瓷材料，其铁电性与晶粒尺寸密切相关，尤其是达到纳米级时，可使材料性质发生奇异变化。迄今人们仅对纯ＢａＴｉＯ３超微细粒子的晶粒尺寸对铁电相变的影响进行了研究［１～３］，对稀土钇掺杂Ｂａ（１－ｘ－ｙ）ＳｒｘＣａｙＴｉＯ３固溶体纳米晶的相关研究报道尚少，而铁电尺寸效应对这类电子功能材料的研究、开发起着关键作用。因此，开展这方面的研究具有重要的学术价值和实际意…     

Li_(0.025)Na_(0.975)NbO_3低温铁电相变及晶体结构

铁电体是重要的物理器件材料之一,它们的自发极化性能在许多器件中得到广泛的应用。而铁电体中的顺电-铁电和铁电-铁电相变是一类重要的结构相变,研究这些相变,一方面可以获得产生铁电性微观机构的重要信息,另一方面对研制新的铁电材料及改进性能也有指导意义。低温铁电相变及共与晶体结构的关系是其中一个重要的分支。由于体系的复杂性及技术上难度的局限,迄今为止只有英国的Megaw等开展了这方面的研究。     

碲化镉纳米晶的制备及应用

基于自身的量子限域效应、尺寸效应、介电限域效应、宏观量子隧道效应和表面效应,碲化镉(CdTe)纳米晶独特的性质在非线性光学、磁介质、催化、医药及功能材料等方面得到了广泛的应用,并且展现出极为广阔的应用前景,同时对生命科学和信息技术的持续发展以及物质领域的基础研究也产生了深刻的影响。本文以 CdTe 纳米晶为对象,详细介绍了其5种典型的制备方法和应用的最新进展。在制备方面,5种典型的制备方法各有利弊,如何在温和的条件下制备出形貌和尺寸可控的 CdTe 纳米晶仍是一个值得追求的目标。通过自组装技术可以制备形貌独特,性能优异的 CdTe 纳米材料,进而实现 CdTe 半导体纳米器件的研制,具有重要的科学意义,是今后研究的热门方向。在应用方面,CdTe纳米晶不但实现了其在光电器件、生物学等领域的应用,而且将会在这些领域继续深化和延伸,开发出新的应用领域。本文同时对 CdTe 纳米晶的发展趋势也进行了展望。     

无机纳米晶-生物界面作用的分子机制

无机纳米晶材料以其独特的光、电、磁、力学性质,成为疾病诊断与治疗功能的关键材料.本文总结了无机纳米晶的表面化学活性、离子释放性、晶相结构、晶格缺陷、表面吸附和表面修饰等与尺寸相关的理化性质与生物效应之间的关系.综述了无机纳米晶与蛋白质、磷脂生物膜间的界面相互作用,探讨了纳米晶-生物界面作用的分子机理.这有助于理解无机纳米晶的生物行为和毒理性质,指导设计安全、高效的纳米晶生物医学材料.     

纳米晶MgSO4·5Mg(OH)2·3H2O合成与表征

纳米材料由于具有表面、体积和量子尺寸效应的特殊性而受到广泛重视[1～3]. 微米级硫氧镁晶须作为塑料添加增强和阻燃剂已有报道[4～7]. 纳米晶MgSO4*5Mg(OH)2*3H2O不仅对塑料起补强作用, 而且其粒度小, 使塑料变得更致密, 强度、韧性与防水性能大大提高. 目前纳米材料的合成方法多种多样[8～10], 本文采用水热法制得纳米硫氧镁晶粒, 产物纯度高、分散性好且粒度易控制.     

手性模板合成CdS纳米棒

由于纳米材料具有量子尺寸效应及大的比表面积等性质而使其在电子学[1]、光学[2]、催化[3]和陶瓷[4]等领域显示出诱人的应用前景. 近年来纳米材料的制备及纳米技术发展迅速, 特别是具有特殊光电活性的新型无机纳米材料的制备已引起人们的普遍关注. 现在合成纳米材料的方法主要包括反相胶束法[5]、 LB膜法[6]、嵌段共聚物法[7]和模板合成法[8]. 其中模板合成技术不仅可以通过设计新型的模板分子, 还可通过模板分子的不同自组装行为来调控纳米材料的尺寸和形貌. Stupp等[9]曾利用溶致液晶的六方中间相作为模板, 在其纳米孔隙中成功地合成了具有六方排列超晶格纳米结构的材料. 本文以双亲性丙氨酸衍生物为模板, 在不同的化学微环境下合成了结构不同的CdS纳米棒.     

钙钛矿二维纳米材料的合成和发光研究进展

钙钛矿纳米材料的研究取得了飞速发展:一方面,合成方法不断涌现,已经可以实现从零维纳米晶、一维纳米线到二维纳米片的形貌精确控制,对其尺寸和维度依赖的光学性质认识也不断深入;另一方面,钙钛矿纳米材料的光学和光电子应用也得到了快速发展,其中,基于钙钛矿量子点的光致发光和电致发光技术最受关注。 由于钙钛矿的天然层状结构,通过配体调控很容易制备出二维纳米材料,其发光性能可以通过层数和组分进行调节,最高量子产率超过85%,且具有偏振发光特性,有望成为一类新型发光材料。 本文从制备方法、光致发光和电致发光应用等方面综述了基于钙钛矿二维纳米材料的进展,并对其未来的发展方向进行讨论。     

纳米金属铜与纳米氧化锌之间相互作用的EPR和XPS研究

由于纳米材料独特的表面效应、电子效应及量子尺寸效应 ,已被广泛应用于各个领域 .有关纳米材料研究的报道很多 [1～ 7] ,大部分是关于纳米材料的制备[1～ 4 ] 及其特性研究 .对于纳米金属及纳米氧化物之间相互作用的研究迄今尚未见报道 .本文采用超声分散和机械研磨法物理混合纳米金属铜粉和纳米氧化锌 ,借助 EPR和 XPS技术对样品进行了表征 ,发现混合体系出现了 Cu2 + 的顺磁信号 ,Zn L3M4 5M4 5俄歇动能和 O1s的电子结合能亦发生了变化 ,表明纳米 Cu0 和纳米 Zn O之间存在相互作用 ,作用形式为 Cu— O—Zn.1　实验部分1 .1　样品…     

2-巯基喹啉包裹的金纳米颗粒的制备及其电化学性质

纳米材料特有的尺寸效应、量子效应和表面效应使其具有许多异于常规材料的性质 ,在催化、生物传感器、微电子器件和磁性材料等诸多领域都有广泛的应用前景 [1] .已有专家预言 ,与纳米材料相关的技术将在新世纪经济发展中起主导作用 ,对其研究是目前科学研究中的热点 .金纳米颗粒是目前研究得最多的金属纳米材料体系 .传统的金纳米颗粒的制备方法以溶胶 -凝胶法为主 [2～ 4 ] ,所制备的金纳米颗粒的粒径较大 (一般大于 1 0 nm) ,粒径分布不均匀 ,易于团聚 ,因而限制了其应用 .为了解决上述问题 ,Brust等 [5]将硫醇化合物在金属表面的自组装…     

掺锰五磷酸铈、铽晶体的生长及其光谱

用蒸发溶液法从磷酸溶液中首次生长出一系列Ce_xTb_(1-x)P_5O_(14):Mn晶体。它们属于单斜晶系,空间群P2_1/c。计算了晶格常数,用EPR结果确定在晶体中锰离子呈二价。测定了Ce_xTb_(1-x)P_5O_(14):Mn晶体的光谱,说明在晶体中存在着Ce~(3+)到Tb~(3+)和Mn~(2+)的能量转移。Mn~(2+)和Tb~(3+)的发射峰重叠,并使Tb~(3+)的发射峰增强。     

Crystal structure of the new FeSe(1-x) superconductor

The newly discovered superconductor FeSe(1-x) (x approximately 0.08, T(c)(onset) approximately 13.5 K at ambient pressure rising to 27 K at 1.48 GPa) exhibits a structural phase transition from tetragonal to orthorhombic below 70 K at ambient pressure-the crystal structure in the superconducting state shows remarkable similarities to that of the REFeAsO(1-x)F(x) (RE = rare earth) superconductors.     

Controlled synthesis of tuned bandgap nanodimensional alloys of PbS(x)Se(1-x)

Truly alloyed PbS(x)Se(1-x) (x = 0-1) nanocrystals (～5 nm in size) have been prepared, and their resulting optical properties are red-shifted systematically as the sulfur content of the materials increases. Their optical properties are discussed using a modified Vegard's approach and the bowing parameter for these nanoalloys is reported for the first time. The alloyed structure of the nanocrystals is supported by the energy-filtered transmission electron microscope images of the samples, which show a homogeneous distribution of sulfur and selenium within the nanocrystals. X-ray photoelectron spectroscopy studies on ligand-exchanged nanocrystals confirmed the expected stoichiometry and various oxidized species.     

Kinetics of induced crystallization of the LC(1-x)Sil(x) system

This study explores the kinetics of a new feature, called "induced crystallization (IC)", observed in an Aerosil dispersed octylcyanobiphenyl (8CB) liquid crystal system. Heating rate dependent experiments were performed using modulation differential scanning calorimetry (MDSC) at various heating ramp rates. In the presence of Aerosil nanoparticles, a well-defined exothermic peak was found as an additional feature on the heating scan before the melting transition, which was absent in the bulk 8CB; hence, we like to call it an "IC" as it is induced by Aerosil nanoparticles in the system. The system LC1-xSilx was prepared by mixing Aerosil nanoparticles in the bulk 8CB by the solvent dispersion method (SDM) where LC represents bulk 8CB and Sil represents Aerosil nanoparticles with x as the Aerosil fraction. The concentration of the Aerosil nanoparticles (x) varied from 0 to 0.2 g/cm3 in the bulk 8CB. The IC transition peak showed a temperature shift and change in the shape and size in the presence of Aerosil nanoparticles. In addition, this transition shifted significantly with different heating ramp rates following an Arrhenius behavior showing activated kinetics. The presence of Aerosil nanoparticles caused a significant increase in the enthalpy and decrease in the activation energy for the IC transition as the density of Aerosil nanoparticles increases and showed a saturation for the highest density of Aerosil nanoparticles. This behavior can be explained in terms of molecular disorder and surface molecular interaction induced by adding Aerosil nanoparticles into the bulk of 8CB liquid crystal.     

Na_（1－x）Zr（2－x）Nb_xP_3O_（12）系列化合物的水热晶化研究

采用水热晶化反应，制备出传统需要高温固相反应合成的掺杂ＮＡＳＩＣＯＮ化合物Ｎａ（１－ｘ）Ｚｒ（２－ｘ）ＮｂｘＰ３Ｏ１２（０＜ｘ＜１），并应用ＸＲＤ、ＩＲ方法对产物的晶体结构进行了研究，表明水热晶化产物是纯的物相并具有与ＮａＺｒ２Ｐ３Ｏ１２相同的结构．固体３１ＰＮＭＲ研究证实Ｎｂ（５＋）部分取代了Ｚｒ（４＋）所在位置，参与骨架的组成，并统计分布于结构中．水热晶化产物与固相反应产物具有相同的离子电导性能．     

Synthesis and characterization thesulphides type ZnS(1-x)MSx

ZnS_(1-x)MS_x(x=0.01 and M=Mn²⁺, Cu²⁺ and Eu²⁺) compounds have been obtained by precipitation from homogeneous solutions of zinc, copper, manganese and europium salts, with S^2- as the precipitating anion, formed by the decomposition of thioacetamide. The thermal study of the milled zinc acetate, thioacetamide, copper acetate, manganese acetate and europium nitrate, respectively, was studied for thermal analyis TG/DSC. XRD respect exhibits a zinc blend crystal structure. This revised version was published online in August 2006 with corrections to the Cover Date.     

Einkristallzüchtung und Verfeinerung der Kristallstruktur von BaPb(1-x)BixO3 (x = 0, 15)

Crystal Growth and Structure Determination of BaPb_(1–x)Bi_xO₃ (x = 0.15) Single crystals (0.15X0.20X0.20 mm) of BaPb_(1–x)Bi_xO₃ (x = 0.15) have been grown from a lead (II)-oxide melt. The refinement of the crystal structure (I4/mcm; a = 6.047(5), c = 8.603(8) Å; Z = 4; 281 diffractometer data, R = 0.03) resulted in Pb(Bi)? O? Pb(Bi) bonding angles of 180° (2X), and 165° (4X) within the a/b plane. The identity of single crystals and powder material was ensured by an Rietveld profile fit of the X-ray powder diagram. The compositions of the single crystals have been determined applying electron microprobe techniques. T_c of the single crystals was found to be 13.2 K (onset, S QUID-magnetometer).     

Photophysical and photocatalytic properties of Ca(1-x)BixVxMo(1-x)O4 solid solutions

New solid solutions with the composition of Ca(1-x)BixVxMo(1-x)O4 prepared by a solid-state method were found as novel photocatalysts with enhanced activity for O(2) evolution from aqueous solutions containing sacrificial reagent AgNO3 under visible-light irradiation (>420 nm). The obtained solid solutions crystallized in tetragonal crystal structures, except one of the end compounds, BiVO4, which crystallized in monoclinic structures. The diffuse reflection spectra of the solid solutions shift monotonically to a long wavelength as the ratio of Bi (V) ions to Ca (Mo) ions increases in the solid solution. The band structure and the dependence of the photocatalytic properties were discussed in relation to the solid-solution compositions and photophysical properties.     

Synthesis and Crystal Structure of 2（1-Phenyl-3-methyl-5-chloro-1H-pyrazol-4-yl）-3-（1-naphthoylamido）-4-thiazolidinone

1INTRODUCTIONManypyrazolederivativeshavebeenreportedtoshowvariousbiologicalactivitiestobeusedasbactericide[1],fungicide[2],herbicide[3],insecticide[4]andvirucide[5]agents.Inaddition,4-thiazolidinoneplaysavitalroleowingtoitswiderangeofbiologi-calactivities…     

(QuinH)_3〔Mo(i-mnt)_4〕的晶体和分子结构

(QuinH)_3 [Mo(i-mnt)_4]为黑色柱状晶体(式中Qui=喹啉 难溶于水,在空气中很稳定。晶体属单斜晶系,空间群Cc,晶胞参数:a=10.688(16),b=31.545(5),c=14.682(26),B=109.28(14)°;ρobs=1.50克/厘米~3,Z=4(ρcalc=1.489克/厘米~3)。晶体在CAD-4衍射仪上,用Mo-Kα射线,θ-2θ扫描方式,在1°<θ<23°范围内收集了4275个独立衍射点。晶体结构用Patterson函数法和Fourier合数法解出,经全矩阵最小二乘方修正,偏离因子R=0.075。结构分析结果说明Mo原子与四个双齿螯合配位基的八个硫原子形成近似于D_(2d)对称性的十二面体结构。