Zn_xCd_(1-x)S纳米线的可控合成及其可调的光学性质（英文）

采用简单的气相沉积法,合成了不同组成的Znx Cd1-x S(0x1)纳米线.利用扫描电子显微镜、透射电子显微镜和电子能谱研究了所制得的纳米线的表面形貌和组成.该方法以Au为催化剂,简单控制起始物质的相对用量和沉积温度,可以获得可控的Zn/Cd比例.X射线衍射结果表明所制得的Znx Cd1-x S纳米线具有纤维锌矿的单晶结构.根据制得纳米线的表面形貌讨论了纳米线可能的生长机理为"底部生长"机理.利用拉曼光谱和光致发光光谱研究了Znx Cd1-x S纳米线的光学性质,其纵向光学(LO)声子的拉曼位移频率随着组成的变化在ZnS和CdS的拉曼位移频率之间连续变化.光致发光光谱中同时存在带边发光和缺陷发光.Znx Cd1-x S纳米线的带间跃迁的频率可随着组成的调节而调节,纳米线的禁带宽度介于ZnS(3.63 eV)和CdS(2.41 eV)的禁带宽度之间.     

功能化ZnxCd1-xS纳米晶的制备及其光学性能的研究

以氯化锌、氯化镉和硫化钠为原料，采用巯基乙醇为表面修饰剂，H₂O/DMF为溶剂，制得未团聚且分散均匀的纳米晶溶液，同时得到表面富含羟基基团不同锌镉组成的复合Zn_xCd_1-xS纳米晶。利用FTIR、EDS、UV-Vis、XRD、荧光光谱(PL)考察了复合纳米晶结构和光学性能的关系，并利用紫外灯摄像技术对Zn_xCd_1-xS纳米晶的光致发光性能进行     

Ag2S或CuS掺杂的Zn0.5Cd0.5S纳米晶体：溶剂热法合成及光致发光性能

以异丙醇为溶剂,醇热法制备Zn_0.5Cd_0.5S和Ag₂S或CuS掺杂的Zn_0.5Cd_0.5S纳米晶体,考察了这些纳米晶体在可见光区域的光致发光性能。结果表明,反应温度和反应时间、掺杂剂的浓度和种类对Zn_0.5Cd_0.5S的发光性能有很大的影响,相比未掺杂Zn_0.5Cd_0.5S纳米晶体而言,Ag₂S或CuS掺杂后其光致发光强度明显增强、半高宽更宽。     

(Zn1-xMnx)C2O4·2H2O在空气中的热分解动力学研究

用热分析（TG-DTG/DTA）、X射线衍射（XRD）技术和透射电镜（TEM）研究了固态物质Zn_1-xMn_xC₂O₄•2H₂O在空气中热分解的过程。热分析结果表明，Zn_1-xMn_xC₂O₄•2H₂O在空气中分两步分解，其失重率与理论计算失重率相吻合。 XRD和TEM结果表明，Zn_1-xMn_xC₂O₄•2H₂O分解的最终产物为Zn_1-xMn_xO,其颗粒大小约为10-13 nm。在非等温条件下对Zn_1-xMn_xC₂O₄•2H₂O的热分解动力学进行了分析。用Friedman法和Flynn-Wall-Ozawa(FWO)法求取了分解过程的活化能E，并用多元线性回归给出了可能的机理函数。Zn_1-xMn_xC₂O₄•2H₂O两步热分解的活化能分别为155.7513 kJ/mol 和215.9397 kJ/mol。     

硫化锌镉固溶体光催化分解水产氢研究现状

硫化锌镉（Cd_1-xZn_xS,0 < x < 1）固溶体因其优异的活性、可调谐的能带结构在光催化分解水制氢领域备受关注,但其较快的光生电荷复合速率和光腐蚀仍阻碍了其进一步应用。因此,研究者们针对其固有缺陷进行了大量改性工作。我们首先简述了光催化反应热力学与动力学特征,随后详细综述了近年来Cd_1-xZn_xS在光解水制氢领域的研究进展,包括其结构调控、异质结构建、杂原子掺杂等方面,简要分析了Cd_1-xZn_xS光催化分解水所面临的挑战和问题,并对近期研究进行了展望。     

金属离子对CdS量子点/聚酰胺-胺树形分子纳米复合材料光致发光性能的影响

以聚酰胺-胺树形分子为模板制备了分散好、尺寸均匀的CdS量子点，并用分光光度滴定法研究了Cd²⁺、Zn²⁺、Pb²⁺、Cu²⁺、Mn²⁺几种金属离子对其光致发光性能的影响。发现不同离子对CdS量子点的发光性能影响不同:Cd²⁺和Zn²⁺使量子点荧光增强，Pb²⁺、Cu²⁺和Mn²⁺使其荧光有不同程度淬灭。这归因于金属离子对CdS量子点表面的修饰作用。Cd²⁺能减少由S^2-悬键构成的非辐射复合中心，增强树形分子对量子点表面缺陷的钝化作用，并能在量子点周围形成类肖特基能垒，从而显著增大CdS量子点的光致发光效率。由于ZnS与CdS的晶格参数非常接近，Zn²⁺能起到与Cd²⁺类似的作用，使CdS量子点的发光效率大大增强。Pb²⁺和Cu²⁺能取代Cd²⁺在CdS量子点表面生成窄带隙的壳层，对其发光有很强的淬灭作用。由于块体PbS的带隙比块体CuS窄，故Pb²⁺的淬灭能力强于Cu²⁺。Mn²⁺能破坏Cd²⁺与PAMAM树形分子的配位键，降低树形分子对CdS量子点表面缺陷的钝化作用，且其本身在量子点表面构成了新的荧光淬灭中心，但Mn²⁺也能形成较弱的类肖特基能垒，故对量子点的发光淬灭作用较弱。     

(Zn，M)TiO3(M=Co，Ni，Co0.5Ni0.5)固溶体的溶胶-凝胶法合成

通过改进的溶胶-凝胶工艺在低温(800 ℃)下合成了基于钛酸锌(ZnTiO₃)体系的(Zn_1-xCo_x)TiO₃、(Zn_1-xNi_x)TiO₃和[Zn_1-x(Co_0.5Ni_0.5)_x]TiO₃陶瓷固溶体。采用X射线衍射分析(XRD)和差示扫描量热法(DSC)等测量技术对产物进行了物相和热稳定性分析。XRD结果表明，获得单一六方相(Zn_1-xCo_x)TiO₃、(Zn_1-xNi_x)TiO₃和[Zn_1-x(Co_0.5Ni_0.5)_x]TiO₃时各自的固溶稳定区间为0.5 ≤ x ≤ 1.0, 0.9 ≤ x ≤ 1.0和0.8 ≤ x ≤ 1.0。与此同时，热分析结果证实，伴随钛酸锌基陶瓷体系掺杂钴量的增加，其六方相的热稳定性提高，且效果比掺杂镍更加显著。     

Na2O-P2O5系晶体微结构形态的拉曼光谱研究及其ab initio计算

本文采用激光拉曼光谱仪测量了磷酸钠二元系(1-x)Na₂O·xP₂O₅(x=0.25,0.33,0.50,1.0)几种晶体的拉曼光谱,比较并解释了随化学组成而变化微结构单元的拉曼振动模。同时用Gaussian 98W量子化学软件从头计算了这几种化合物的拉曼光谱。实验和计算均表明,磷酸盐晶体的基本结构单元为磷氧四面体[PO₄],并且晶体中磷氧四面体的伸缩模振动频率与连接中心磷原子的桥氧数密切相关,随桥氧数增加而升高。此外还解释了模拟图谱与实验谱差异的原因。     

硫脲修饰ZnSe:Cu量子点的水相合成及荧光特性

以3-巯基丙酸为稳定剂在水相中合成了Cu掺杂的ZnSe量子点(QDs), 并利用硫脲(CH₄N₂S)对其进行表面修饰, 制备出核壳结构的ZnSe:Cu/ZnS 量子点. 制得的量子点呈闪锌矿结构, 尺寸约为5 nm, 有较好的分散性, 其荧光发射峰在460 nm左右. 经CH₄N₂S修饰后, 量子点表面形成了宽禁带的ZnS包覆层, 将电子和空穴限域在了ZnSe:Cu 核内, 减少了表面发生非辐射复合的载流子, 显著提高了量子点的荧光强度. 与Na₂S、硫代乙酰胺(TAA)等常用硫源相比, 以CH₄N₂S为硫源制得的ZnSe:Cu/ZnS 量子点壳层厚度可控, 表面钝化效果更好, 显示出更佳的荧光效率和稳定性. ZnSe:Cu/ZnS 量子点经过紫外线照射后消除了表面的悬空键, 进一步提高了其量子产率, 最终获到了具有较好荧光性质的ZnSe:Cu/ZnS量子点.     

BaFeO3-x与Cu-ZSM-5耦合催化剂的NOx储存还原性能

为替代传统的贵金属基NO_x储存还原（NSR）催化剂,本文设计并制备了不含贵金属的BaFeO_3-x+Cu-ZSM-5 耦合催化剂,用于催化消除稀燃发动机尾气中的NO_x. 在稀燃阶段,NO在BaFeO_3-x催化剂上发生了氧化和储存反应;在富燃阶段,从BaFeO_3-x催化剂中脱附出来未能消除的NO_x被置于其后的Cu-ZSM-5催化剂进一步催化消除. 实验结果表明,BaFeO_3-x+Cu-ZSM-5 耦合催化剂的工作温度窗口被拓宽到250-400 ℃,同时NO_x消除性能得到了显著提高：NO_x转化率最高可达98%,N₂选择性接近100%.     

Effects of gold catalysts and thermal evaporation method modifications on the growth process of Zn1−xMgxO nanowires

In this paper, we investigate the roles of gold catalysts and thermal evaporation method modifications in the growth process of Zn_1−xMg_xO nanowires. Zn_1−xMg_xO nanowires are fabricated on silicon substrates with and without using a gold catalyst. Characterizations reveal that Mg acts in a self-catalyst role during the growth process of Zn_1−xMg_xO nanowires grown on catalyst-free substrate. The optical properties and crystalline quality of the Zn_1−xMg_xO nanowires are characterized by room temperature photoluminescence (PL) measurements and Raman spectroscopy, respectively. The Raman and PL studies demonstrate that the Zn_1−xMg_xO nanowires grown using the catalyst-free method have good crystallinity with excellent optical properties and have a larger band-gap in comparison to those grown with the assistance of gold.     

Nanocrystalline Zn1−x−yBexMgyO thin films synthesized by the sol–gel method: structural and near infrared photoluminescence properties

In this paper, we reports on the structural and optical properties of Zn_1?x?yBe_xMg_yO thin films prepared by sol–gel method, which are new materials for optoelectronic and ultraviolet-light-emitting devices. The crystal structure and core level spectra of these films are studied by X-ray diffraction and X-ray photoelectron spectroscopy. Surface morphology of the films is analyzed by scanning electron microscope images and the surface is composed of spherical shaped grains. Micro-photoluminescence shows a near edge band emission and the peak values tuned from 3.26 eV for the undoped to 3.4 eV for the doped ZnO film. Near infrared emission is observed in the region 1.64–1.67 eV for pure and co-doped ZnO films. In micro-Raman spectra, multiple-order Raman bands originating from ZnO-like longitudinal optical (LO) phonons are observed. A Raman shift of about 5–18 cm^?1 is observed for the first-order LO phonon. A comparative study was made on Raman band for BeZnO, MgZnO and BeMgZnO nanocrystals with the LO phonon band of bulk ZnO. The ultraviolet resonant Raman excitation at room temperature shows multi-phonon LO modes up to the fourth order. Deformation energy of all the films is calculated and BeMgZnO film has the minimum deformation energy.     

Raman spectroscopy in AB2X4 pseudoternary layered compounds

We have synthesized several pseudoternary layered compounds by cation or anion cross substitution in ternary AB₂X₄ compounds. Here we report on the low frequency Raman spectra obtained from Zn_xCd_1-xIn₂S₄, Zn(In_xGa_1-x)₂S₄ and ZnIn₂(S_xSe_1-x)₄ single crystals. Within these systems we have identified five compositionally or dynamically different phases. Each of these phases may be characterized by its peculiar low frequency Raman spectrum which is connected to the dynamics of the layers in the unit cell. Abrupt structural/dynamical changes are observed as a function of composition between different phases. Within each phase compositional changes cause only smooth and small spectral variations.     

First-principles calculations of Cd-doped ZnO thin films deposited by pulse laser deposition

Zn_1−xCd_xO thin films are deposited on quartz substrate by pulse laser deposition. Their band structure and optical properties are experimentally and theoretically investigated. By varying Cd concentration, the band gap of Zn_1−xCd_xO films can be adjusted in a wide range from 3.219 eV for ZnO to 2.197 eV for Zn_0.5Cd_0.5O, which produces different emissions from ultraviolet to Kelly light in their photoluminescence spectra. Simultaneity, the electronic structure and band gap of Zn_1−xCd_xO are investigated by the density functional theory (DFT) with a combined generalized gradient approximation (GGA) plus Hubbard U approach, which precisely predicts the band-gaps of ZnO and Zn_1−xCd_xO alloys. Both the experimental results and theoretical simulation reveal that with increasing Cd concentration in Zn_1−xCd_xO alloys, their absorption coefficients in visible light range are evidently enhanced. The adjustable photoluminescence emission and enhanced visible light absorption endow Zn_1−xCd_xO alloys potential applications in optoelectronic and photocatalytic fields.     

Reverse micelle-derived Cu-doped Zn1−xCdxS quantum dots and their core/shell structure

Reverse micelle chemistry-derived Cu-doped Zn_1?xCd_xS quantum dots (QDs) with the composition (x) of 0, 0.5, 1 are reported. The Cu emission was found to be dependent on the host composition of QDs. While a dim green/orange emission was observed from ZnS:Cu QDs, a relatively strong red emission could be obtained from CdS:Cu and Zn_0.5Cd_0.5S:Cu QDs. Luminescent properties of undoped QDs versus Cu-doped ones and quantum yields of alloyed ZnCdS versus CdS QDs are compared and discussed. To enhance Cu-related red emission of CdS:Cu and Zn_0.5Cd_0.5S:Cu core QDs, core/shell structured QDs with a wider band gap of ZnS shell are also demonstrated.     

Optical Properties of Mg x Zn1−x O Polycrystalline Thin Films Prepared by Sol-Gel Deposition Method

The Mg _x Zn_1–x O alloy thin films were synthesized on Si and quartz substrates by the sol-gel deposition method. The transmittance and cathodoluminescence spectra of the Mg_0.05Zn_0.95O and Mg_0.15Zn_0.85O nanoparticle films were obtained at room temperature. It was found that the bandgap of Mg_0.05Zn_0.95O and Mg_0.15Zn_0.85O films is as large as 3.72 eV and 3.79 eV, respectively. The ultraviolet emission peaks are located at 376 nm and 370 nm, respectively, for the samples annealed at 600°C. When the annealing temperature is elevated to 1000°C, the band-gap decreases to 3.42 eV and an emission line related to the deep-level defect appears at 500 nm. The mechanism behind these phenomena is discussed.     

Synthesis of nanocomposite, (CdxZn1-x)S by gamma-irradiation in an aqueous system

Gamma-irradiation has been applied to synthesize the nanocomposite semiconductor constituted of zinc and cadmium sulfide Cd_1-xZn_xS ultra fine particles at room temperature by utilizing homogeneous release of S^2– ions from the decomposition of sodium thiosulfate. The structure, morphology, size and optical properties of that compound have been studied by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet-visible spectrometer (UV-visible). The product obtained from irradiated solutions containing zinc ions, cadmium ions and the sulfur source has been characterized as a composite of (Cd_xZn_1-x)S, with spherical morphology and with a diameter of average size of about 5.3 nm. The possible mechanism of formation of the composite is proposed.The financial support of Shanghai Science and Technology Foundation through No. 0252nm 095 is gratefully acknowledged.The authors would thank the staff of Shanghai Applied Radiation Institute of Shanghai University for their valuable contributions.     

Fluorescent-Magnetic Nanostructures Based on Polymer-Quantum Dots Conjugates

Summary: In this study it is presented the synthesis and the characterization of Fluorescent-Magnetic Nanostructures based on polymer-quantum dots conjugates. Polyvinyl alcohol (PVA) was used as the capping-ligand for the preparation of Cd_xMn_1-xS semiconductor nanocrystals via aqueous colloidal chemistry. Different substitution ratios of Cd²⁺ by Mn⁺² ions were investigated aiming at the formation of stable nanoparticles with photo-luminescent and semi-magnetic properties. UV-visible spectroscopy (UV-vis), photoluminescence spectroscopy (PL), Electric Paramagnetic Resonance Spectroscopy (EPR), and transmission electron microscopy (TEM) were used to characterize the formation and the relative stability of Cd_xMn_1-xS nanoparticles. The results have showed the influence of the Mn²⁺partially replacing Cd²⁺ in the optical behavior of the quantum dots (QDs) produced. In addition, the Cd_xMn_1-xS QDs have evidenced luminescent and semi-magnetic properties. Thus, the biocompatible water-soluble polymer was effective as ligand for synthesizing and stabilizing QDs conjugates with properties allowing them to be potentially applied as imaging and labeling probes in the biomedical field.     

Photopolymerization of water-soluble acrylic monomers induced by colloidal CdS and Cd x Zn1 − x S nanoparticles

Photocatalytic activity of CdS and Cd _x Zn_1−x S nanoparticles in the polymerization of acrylamide and acrylic acid in aqueous solutions has been found. It has been shown that the most probable way of the photogeneration of primary radicals is the reduction of an adsorbed monomer by the conduction band electrons of the semiconductor nanoparticles, a monomer oxidation by the valence band holes and atomic hydrogen addition to a monomer being complementary photoinitiation routes. A correlation between the composition of Cd_xZn_1-xS nanoparticles and their photocatalytic activity in the acrylamide polymerization has been established. It has been shown that an increase in the quantum yield of the photopolymerization in a sequence СdS < Cd_0.75Zn_0.25S < CdS_0.5Zn_0.5S < Cd_0.3Zn_0.7S originates from a concurrent increase of the conduction band potential of the semiconductor nanoparticles. A kinetic equation of the photocatalytic acrylamide polymerization has been derived. Quantum yields of the photoinitiation have been found to be as small as 10⁻⁴ to 10⁻³.     

Magneto‐Optical Studies of HgTe/HgxCd1−xTe(S) Core–Shell Nanocrystals

The synthesis and magneto‐optical properties of HgTe nanocrystals capped with Hg_xCd_1?xTe(S) alloyed shells have been investigated. The magneto‐optical measurements included the use of optically detected magnetic resonance (ODMR) and circular polarized photoluminescence (CP‐PL) spectroscopy. The PL spectra suggest the existence of luminescence events from both the core HgTe and the Hg_xCd_1?xTe(S) shells. The continuous‐wave (cw) and time‐resolved ODMR measurements revealed that the luminescence at the shell regime is associated with a trap‐to‐band recombination emission. The electron trap is comprised of a Cd–Hg mixed site, confirming the existence of an alloyed Hg_xCd_1?xTe(S) composition. The ODMR data and the CP‐PL measurements together revealed the g‐values of the trapped electron and the valence band hole.