以Na2TeO3为碲源制备CdTe纳米晶及其表征

本文以巯基乙酸作为稳定剂,在水相中制备了CdTe纳米晶。以亚碲酸钠作为碲源,从而避免了以H2Te或NaHTe（用碲粉和硼氢化钠合成）作为碲源时,需要氮气或其它气体作为保护气体的过程,简化了制备工艺,并且提高了CdTe纳米晶的产量。用X射线衍射仪（XRD）、透射电镜（SEM）和荧光分光光度计对其进行了表征。分析表明CdTe纳米晶为立方相,并且有较窄的荧光发射峰。详细探讨了反应时间、pH值及前驱物浓度对CdTe纳米晶荧光性能的影响。     

High‐Yield Fabrication and Electrochemical Characterization of Tetrapodal CdSe,CdTe, and CdSexTe1–x Nanocrystals

The high‐yield fabrication of tetrapodal CdSe, CdTe, and CdSe_xTe_1–x nanocrystals is systematically studied. CdSe nanocrystals are prepared by first controlling the synthesis of high‐quality wurtzite CdSe and zinc blende CdSe nanocrystals at a relatively high temperature (260 °C) by selecting different ligands. Then, based on the phase control of the CdSe nanocrystals, two nanoparticle‐tailoring routes (i.e., a seed‐epitaxial route and ligand‐dependent multi‐injecting route) are used, and a high yield of CdSe tetrapods is obtained. CdTe nanocrystals are prepared by adjusting the ligand composition and the ratio of Cd to Te; CdTe tetrapods are synthesized in high yield using a mixed ligand that does not contain alkylphosphonic acids. Moreover, the nanoscale Te powder (Te nanowires/nanorods), which is highly soluble in the ligand solvent, is first used as a Te source to synthesize CdTe nanocrystals, which remarkably enhanced the output of the CdTe nanocrystals in one reaction. Furthermore, composition‐tunable ternary CdSe_xTe_1–x alloyed tetrapods are synthesized on a large scale, for the first time, by thermolyzing the mixture of the organometallic Cd precursor and the mixed (Se + Te) source in a mixed‐ligand solution. The CdSe, CdTe, and CdSe_xTe_1–x nanocrystals are characterized by transmission electron microscopy (TEM), high‐resolution TEM, selected‐area electron diffraction, X‐ray diffraction, and UV‐vis and photoluminescence (PL) spectroscopy. Interesting nonlinear, composition‐dependent absorption and PL spectra are observed for the ternary CdSe_xTe_1–x alloyed nanocrystals. The band‐edge positions of the nanocrystals of CdSe, CdSe_xTe_1–x, and CdTe are systematically studied by cyclic voltammetry.     

High‐Performance Hybrid Solar Cell Made from CdSe/CdTe Nanocrystals Supported on Reduced Graphene Oxide and PCDTBT

Core/shell tetrapods synthesized from CdSe and CdTe exhibit a type II band offset that induces separation of charge upon photoexcitation and localizes carriers to different regions of the tetrahedral geometry. CdSe/CdTe nanocrystals immobilized on oleylamine‐functionalized reduced graphene oxide (rGO) sheets can be homogeneously mixed with an organic dye (PCDTBT) to form donor–acceptor dispersed heterojunctions and exhibit a high power conversion efficiency of ～3.3% in solar cell devices. The near‐IR light absorbing type II nanocrystals complement the absorption spectrum of the visible light‐absorbing organics. The high efficiency is attributed to the amine‐functionalized rGO sheets, which allow intimate contact with the nanocrystals and efficient dispersal in the organic matrix, contributing to highly efficient charge separation and transfer at the nanocrystal, rGO, and polymer interfaces.     

Layer‐by‐Layer All‐Inorganic Quantum‐Dot‐Based LEDs: A Simple Procedure with Robust Performance

A novel all‐inorganic electroluminescent device is demonstrated based on highly luminescent CdTe nanocrystals intercalated within a laminar hydrotalcite‐like structure. The laminar scaffold acts to both support and distribute the CdTe nanocrystals. The device is synthesized using simple wet chemical processes at room temperature in ambient conditions. It has high thermal stability, operating continuously up to 90 °C, and a maximum efficiency at J = 0.12 A cm^?2. The device is targeted at the automotive industry.     

Inside Front Cover: Inkjet Printing of Luminescent CdTe Nanocrystal–Polymer Composites (Adv. Funct. Mater. 1/2007)

Schubert and co‐workers have performed a detailed investigation on ink‐jet printing of well‐defined dots of luminescent CdTe nanocrystals (NCs) embedded in a poly(vinyl alcohol) matrix, as reported on p. 23, and subsequently made studies of their morphology and photoluminescence. The inside cover shows a photograph of an ink‐jet‐printed combinatorial library of differently sized CdTe NCs emitting at different wavelengths, and a 3D profilometer image of an array of printed dots. Inkjet printing is used to produce well‐defined patterns of dots (with diameters of ca. 120 μm) that are composed of luminescent CdTe nanocrystals (NCs) embedded within a poly(vinylalcohol) (PVA) matrix. Addition of ethylene glycol (1–2 vol %) to the aqueous solution of CdTe NCs suppresses the well‐known ring‐formation effect in inkjet printing leading to exceptionally uniform dots. Atomic force microscopy characterization reveals that in the CdTe NC films the particle–particle interaction could be prevented using inert PVA as a matrix. Combinatorial libraries of CdTe NC–PVA composites with variable NC sizes and polymer/NC ratios are prepared using inkjet printing. These libraries are subsequently characterized using a UV/fluorescence plate reader to determine their luminescent properties. Energy transfer from green‐light‐emitting to red‐light‐emitting CdTe NCs in the composite containing green‐ (2.6 nm diameter) and red‐emitting (3.5 nm diameter) NCs are demonstrated.     

CdTe/CdS core shell quantum dots for photonic applications

In this work, we show a simple experimental procedure to obtain CdTe/CdS (diameter=3-7 nm) core shell nanocrystals in colloidal suspension. The nanocrystals were characterized by transmission electronic microscopy and powder X-ray diffraction analysis. The optical properties were determined by electronic absorption, excitation and emission spectroscopies and are discussed in terms of chemical changes that occur at the surface of the particles.     

Inkjet Printing of Luminescent CdTe Nanocrystal–Polymer Composites

Inkjet printing is used to produce well‐defined patterns of dots (with diameters of ca. 120 μm) that are composed of luminescent CdTe nanocrystals (NCs) embedded within a poly(vinylalcohol) (PVA) matrix. Addition of ethylene glycol (1–2 vol %) to the aqueous solution of CdTe NCs suppresses the well‐known ring‐formation effect in inkjet printing leading to exceptionally uniform dots. Atomic force microscopy characterization reveals that in the CdTe NC films the particle–particle interaction could be prevented using inert PVA as a matrix. Combinatorial libraries of CdTe NC–PVA composites with variable NC sizes and polymer/NC ratios are prepared using inkjet printing. These libraries are subsequently characterized using a UV/fluorescence plate reader to determine their luminescent properties. Energy transfer from green‐light‐emitting to red‐light‐emitting CdTe NCs in the composite containing green‐ (2.6 nm diameter) and red‐emitting (3.5 nm diameter) NCs are demonstrated.     

CuInSe_2纳米晶体的制备研究

以三乙醇胺为溶剂,通过易于实现的非注入法(noninjection)合成铜铟硒(CuInSe2)纳米晶体。采用SEM、XRD、XPS和EDX分析了所制CuInSe2纳米晶体的组分与结构。结果表明,合成的CuInSe2纳米晶体为类球形,尺寸均匀,具有单一相结构并且接近化学计量比。该纳米晶体的能带隙为(1.03±0.03)eV,对可见光吸收良好,符合光伏应用的要求。     

Electrical and photoelectric properties of polycrystalline textured CdTe

The temperature dependences of the resistivity and photoconductivity spectra of polycrystalline coarse-grained stoichiometric CdTe purified in the process of repeated recrystallization at temperatures two times lower than melting point were studied; CdTe ingots were synthesized from starting components subjected profound purification. It is shown that the main characteristics of polycrystals (resistivity, and the lifetime and mobility of carriers) are determined by composite complexes formed as a result of interaction between extended and point defects. The values of the product of mobility multiplied by lifetime are determined.     

Limitations in Producing Nanocrystals Using Reverse Micelles as Nanoreactors

In this paper the synthesis and characterization of CdTe nanocrystals are presented. Opposite to what has been observed with Cd_1–yMn_yS, it has been impossible to include manganese ions in CdTe matrices. Only large rods of telluride were seen. ZnTe could also not be formed and again only Te rods were perceived. This clearly indicates that chemistry in colloidal self‐assemblies is not always similar to that in homogeneous solutions.     

单模微波水热控制合成PbS纳米晶

以Pb(NO3)2、生物小分子L-半胱氨酸为原料,在室温下生成前驱体,然后采用单模微波水热法在150℃下反应1h,制备出四方形的PbS纳米晶,考察了Pb(NO3)2与L-半胱氨酸的物质的量比对产物形貌的影响。采用XRD和TEM对产物的结构和形貌进行了表征。结果表明,随着Pb2+与L-半胱氨酸的物质的量比增大,纳米PbS颗粒变小,四方形结构越来越明显。初步讨论了PbS纳米粒子的形成机理。形成机理可能为:首先L-半胱氨酸通过巯基直接和Pb2+结合形成白色前驱沉淀,然后该前驱沉淀在一定温度和时间内热分解形成四方形PbS纳米晶,增大L-半胱氨酸在前驱体中的比例,由于存在阻碍作用,导致PbS小晶粒不能快速聚集而结晶生长,而有利形成四方形的纳米PbS。     

Preparation‐Condition Dependence of Hybrid SiO2‐Coated CdTe Nanocrystals with Intense and Tunable Photoluminescence

When aqueously prepared CdTe nanocrystals (NCs) are coated with a SiO₂ shell containing Cd ions and a sulfur source, they show a drastic increase in photoluminescence (PL) efficiency with a significant red shift and spectral narrowing after reflux. This is ascribed to the creation of a hybrid structure characterized by the formation of CdS‐like clusters in the vicinity of the NCs in the SiO₂ shell. Since these clusters are close to the NCs, their effective size increases to reduce the quantum size effect. The dependences of the PL properties on the preparation conditions are systematically investigated. The PL efficiency increases from 28% to 80% in the best case with a red shift of 80 nm. The PL behaviors differ from those of normal CdTe NCs and include less temperature quenching and longer PL lifetime. The SiO₂ coating enables bioconjugation with IgG without deterioration of PL efficiency, making hybrid NCs amenable for bioapplication.     

Efficient and Photostable ZnS‐Passivated CdS:Mn Luminescent Nanocrystals

Efficient and photostable ZnS‐passivated CdS:Mn (CdS:Mn/ZnS core/shell) nanocrystals were synthesized using reverse micelle chemistry. CdS:Mn/ZnS core/shell nanocrystals exhibited much improved luminescent properties (quantum yield and photostability) over organically (n‐dodecanethiol‐) capped CdS:Mn nanocrystals. This is the result of effective, robust passivation of CdS surface states by the ZnS shell and consequent suppression of non‐radiative recombination transitions. The dependence of photoluminescence (PL) intensity has been observed as a function of UV irradiation time for both organically and inorganically capped CdS:Mn nanocrystals. Whereas organically capped CdS:Mn nanocrystals exhibit a significant reduction of PL intensity, CdS:Mn/ZnS core/shell nanocrystals exhibit an increased PL intensity with UV irradiation. XPS (X‐ray photoelectron spectroscopy) studies reveal that UV irradiation of CdS:Mn/ZnS nanocrystals in air atmosphere induces the photo‐oxidation of the ZnS shell surface, leading to the formation of ZnSO₄. This photo‐oxidation product is presumably responsible for the enhanced PL emission, serving as a passivating layer.     

Controlling the Optical Properties of Inorganic Nanoparticles

The sophistication with which we can now prepare and characterize inorganic nanoparticles has inspired new areas of research into the fundamental properties and applications of these fascinating nanoscale systems. In this article some of the recent ideas concerning control of their optical properties are examined and explained, focusing on semiconductor nanocrystals. It is known that the optical properties of nanocrystals can be size‐tunable, but it is less obvious how shape matters. To explain how size as well as shape matters, the electronic structure of nanocrystals is sketched in relatively simple terms, leading to an introduction to deeper concepts at the heart of spectroscopy such as the exciton fine structure. The exciton fine structure states, although obscured by inhomogeneous line broadening, dictate selection rules for optical excitation. These viewpoints are compared and contrasted to well‐established principles in molecular spectroscopy that provide inspiration as well as perspective. The control of optical poperties is founded on our ability to prepare good quality colloidal particles. Recent advances in nanocrystal shape control are described. The current status of heterostructures is examined, with an emphasis on charge separation in CdSe–CdTe nanorods.     

Protein‐Mediated Synthesis of Uniform Superparamagnetic Magnetite Nanocrystals

Magnetite nanocrystals are synthesized in the presence of a recombinant Mms6 protein thought to be involved in the biomineralization of bacterial magnetite magnetosomes, the mammalian iron‐storage protein, ferritin, and two proteins not known to bind iron, lipocalin (Lcn2) and bovine serum albumin (BSA). To mimic the conditions at which magnetite nanocrystals are formed in magnetotactic bacteria, magnetite synthesis is performed in a polymeric gel to slow down the diffusion rates of the reagents. Recombinant Mms6 facilitates formation of ca. 30 nm single‐domain, uniform magnetite nanocrystals in solution, as verified by using transmission electron microscopy analysis and magnetization measurements. The nanocrystals formed in the presence of ferritin, Lcn2, and BSA, do not exhibit the uniform sizes and shapes observed for those produced in the presence of Mms6. Mms6‐derived magnetite nanoparticles show the largest magnetization values above the blocking temperature, as well as the largest magnetic susceptibility compared to those of the nanomaterials synthesized with other proteins. The latter is indicative of a substantial effective magnetic moment per particle, which is consistent with the presence of magnetite with a well‐defined crystalline structure. The combination of electron microscopy analysis and magnetic measurements confirms our hypothesis that Mms6 promotes the shape‐selective formation of uniform superparamagnetic nanocrystals. This provides a unique bioinspired route for synthesis of uniform magnetite nanocrystals.     

CdTe和CdTe/CdS量子点的量子尺寸效应

利用水热法合成了三种不同尺寸的单核CdTe量子点和核壳CdTe/CdS量子点。应用Top-hat Z-scan技术在纳秒、皮秒、飞秒激光脉冲作用下研究了三种不同尺寸单核CdTe量子点的非线性吸收特性。实验结果表明:在不同激光脉冲作用下三种不同尺寸的CdTe量子点的非线性吸收特性均表现为饱和吸收,并且均呈现出随着量子点尺寸的减小,其非线性吸收特性增大的趋势。为了进一步研究量子点尺寸的变化对非线性吸收特性的影响,又在飞秒激光脉冲作用下研究了核壳CdTe/CdS量子点的非线性吸收特性;随着包壳时间的增加,壳层厚度增加,量子点尺寸增加,其非线性吸收特性呈减小趋势,并且核壳CdTe/CdS量子点的非线性吸收特性明显优于单核CdTe量子点;分析讨论了单核CdTe量子点与核壳CdTe/CdS量子点的非线性吸收特性和量子尺寸效应机制,实验结果表明合成的量子点样品均具有良好的量子尺寸效应。     

分子束外延CdTe（211）B／Si复合衬底材料

报道了用MBE的方法，在3英寸Si衬底上制备ZnTe／CdTe（211）B复合衬底材料的初步研究结果，该研究结果将能够直接应用于大面积Si基HgCdTe IRFPA材料的生长．经过Si（211）衬底低温表面处理、ZnTe低温成核、高温退火、高温ZnTe、CdTe层的生长研究，用MBE方法成功地获得了3英寸Si基ZnTe／CdTe（211）B复合衬底材料．CdTe厚度大于10μm，XRD FWHM平均值为120arc sec，最好达到100arc sec，无（133）孪晶和其他多晶晶向．     

Nanoparticles Prepared by Salt Vapor‐Solvent Vapor Cocondensation and Controlled Nucleation: Metal Sulfides (ZnS,CdS, CdSe,PbS), and Metal Halide (LiF). Size,Aggregates, Structures,Digestive Ripening,Superlattices, and Impregnations

A versatile method for the production of gram quantities of nanocrystals of metal sulfides and metal halides has been developed, based on vaporization of the bulk materials followed by controlled nucleation of the molecular vapor species in cold solvent matrices (cocondensate). This approach worked well with ZnS, CdS, CdSe, CdTe, SnS, PbS, and LiF as examples, and is applicable for a large number of semiconductors, ionic salts, as well as metals. Choice of solvent (polar or non‐polar), vaporization rate, and rate of warm‐up of the cocondensate (period of nucleation) allows some control of crystallite size, aggregate size, and surface area. Interestingly, polar solvents lead to smaller nanocrystals, but larger, less porous aggregates. Also, molar mass of the molecular species has an effect on crystallite size, with heavier molecules giving smaller crystals, apparently due to slower migration in the warming cocondensate. Studies of sintering temperature and crystal growth have shown the nanocrystals are quite thermally stable. Addition of ligands, such as thiols, followed by heating in solvent (digestive ripening) has allowed more monodisperse materials to be formed. Finally, this molecular vapor synthesis approach can be used for impregnating semiconductors (CdS, CdSe) of controlled crystal size on solid supports, such as TiO₂ or SiO₂.     

Coordinatable and High Charge‐Carrier‐Mobility Water‐Soluble Conjugated Copolymers for Effective Aqueous‐Processed Polymer–Nanocrystal Hybrid Solar Cells and OFET Applications

A water‐soluble conjugated polymer (WCP) poly[(3,4‐dibromo‐2,5‐thienylene vinylene)‐co‐(p‐phenylene‐vinylene)] (PBTPV), containing thiophene rings with high charge‐carrier mobility and benzene rings with excellent solubility is designed and prepared through Wessling polymerization. The PBTPV precursor can be easily processed by employing water or alcohols as the solvents, which are clean, environmentally friendly, and non‐toxic compared with the highly toxic organic solvents such as chloroform and chlorobenzene. As a novel photoelectric material, PBTPV presents excellent hole‐transport properties with a carrier mobility of 5 × 10^?4 cm² V^?1 s^?1 measured in an organic field‐effect transistor device. By integrating PBTPV with aqueous CdTe nanocrystals (NCs) to produce the active layer of water‐processed hybrid solar cells, the devices exhibit effective power conversion efficiency up to 3.3%. Moreover, the PBTPV can form strong coordination interactions with the CdTe NCs through the S atoms on the thiophene rings, and effective coordination with other nanoparticles can be reasonably expected.     

稀土掺杂Y2O3纳米晶发光材料的研究进展

总结了近几年稀土掺杂Y2O3纳米晶发光材料的研究工作。回顾了Y2O3:Eu3+纳米晶的制备方法及发光性质,特别是采用溶胶–凝胶热解过程,在激发光谱中观察到同基质晶格和粒径相关的蓝色位移(≈600cm–1)。详细介绍了Er3+和Ho3+掺杂的Y2O3纳米晶的上转换机理,由于纳米晶表面容易吸附空气中的CO2和H2O,使得上转换性能明显低于体材料。通过对其进行表面改性处理,可以大大提高发光效率。并探讨了其发展前景。