氨基酸稳定的CdSe纳米晶对溶菌酶进行荧光标记

利用氨基酸中惟一带有巯基的L-半胱氨酸盐酸盐(L-Cys)作为稳定剂在水相体系中合成CdSe纳米晶,通过表面包覆的L-Cys与生物试剂溶菌酶进行结合,实现CdSe纳米晶对溶菌酶的荧光标记.利用TEM、荧光光谱仪及荧光显微镜等多种手段对样品的结构、形貌及光学性能进行表征.试验结果表明,利用L-Cys为稳定剂合成的CdSe纳米晶具有较强的生物活性,L-Cys本身所带的氨基和羧基可以和多种生物试剂通过不同途径进行结合.对溶菌酶(Lys)标记前后,CdSe纳米晶的发射光谱的峰位发生微小红移,大约为2nm,半峰全宽基本保持不变,在40~50nm之间,荧光强度随所标记的Lys浓度的不同均发生明显增强.所有特性均表明实验所合成的CdSe纳米晶在生物标记方面具有很好的实用价值.     

基于CdSe纳米晶发光器件的电致发光特性的研究

以巯基乙酸为稳定剂,在水溶液中制备了硒化镉(CdSe)纳米晶。用X射线光电子能谱(XPS)及其在水溶液中的紫外可见吸收光谱对其进行了表征。又以CdSe为发光材料制备了两种结构的电致发光器件,并对它们的光致发光和电致发光特性进行了研究。在两个器件的电致发光中都得到了CdSe纳米晶的发光,说明CdSe纳米晶是主要的发光中心而聚乙烯咔唑(PVK)只是空穴注入和传输的媒介。在电致发光光谱中还出现了一个不同于CdSe纳米晶和PVK的发光峰值,它是CdSe/BCP(2,9-二甲基-4,7-二苯基-1,10-菲咯啉)界面处的电致发光激基复合物的发光。     

不同厚度CdSe阱层的表面上自组织CdSe量子点的发光性质

利用变温和变激发功率分别研究了不同厚度CdSe阱层的自组织CdSe量子点的发光。稳态变温光谱表明:低温下CdSe量子阱有很强的发光,高温猝灭,而其表面上的量子点发光可持续到室温,原因归结于量子点的三维量子尺寸限制效应;变激发功率光谱表明:量子点激子发光是典型的自由激子发光,且在功率增加时。宽阱层表面上的CdSe量子点有明显的带填充效应。通过比较不同CdSe阱层厚度的样品的发光,发现其表面上量子点的发光差异较大,这可以归结为阱层厚度不同导致应变弛豫的程度不同,直接决定了所形成量子点的大小与空间分布^[1]。     

CdSe在高压下的电学性质及相变

 利用在金刚石压砧上集成的微电路,原位测量了CdSe多晶粉末在温度为300~450 K、压力达到23 GPa时电阻率随温度和压力的变化关系。实验结果表明：在加压过程中,电阻率在2.6 GPa压力时出现的异常改变,对应着CdSe从纤锌矿向岩盐矿结构的转变,而在6.0、9.8、17.0 GPa等压力处出现的电阻率异常,则是由CdSe中的电子结构的变化所引起的;在卸压过程中,只在约14.0和3.0 GPa压力下观察到了两个电阻率异常点。通过对电阻率随压力变化曲线的模拟,得出了CdSe高压相的带隙随压力的变化关系,据此预测CdSe金属化的压力应在70~100 GPa之间。变温实验结果表明,在实验的温度和压力范围内,CdSe的电阻率均随温度的增加而升高。     

CdSe/ZnS Fluorescent Nanoparticles as Nanoprobes of Local pH in Diagnostics of Oncology

We discuss the fluorescence spectra from a set of points in histological sections of colon tissue with different levels of pathology that were stained with hydrophilic semiconductor CdSe/ZnS nanoparticles that were modified by a unique method at the phase interface. The shifts in the fluorescence spectra that were recorded for stained cells at different pathologies are described using the electrochromism of the nanoparticles. Aqueous solutions of the CdSe/ZnS nanoparticles with different pH values are used as systems that model the acidity of a biological medium. It has been shown that the shifts of the fluorescence bands of the CdSe/ZnS nanoparticles are caused by a change in the local electrical field that is induced by solvated ions near their surface at different pH values of the solutions. The application of the CdSe/ZnS nanoparticles as nanoprobes for the local pH in biological tissue is discussed in the context of this model.     

Stoichiometric and ultra-stable nanoparticles of II-VI compound semiconductors

Nanoparticles of (CdSe)_n are found extremely stable at n = 33 and 34 with structures distinctively different from the bulk fragments. They grow exclusively in large amount with a simple solution method. The diameter is determined as 1.5 nm. Such ultra-stable nanoparticles had been predicted both theoretically and experimentally after the discovery of carbon fullerenes, but not been produced macroscopically in any other element or compound system. First-principles calculations predict that the structures of (CdSe)₃₃ and (CdSe)₃₄ are puckered (CdSe)₂₈-cages accommodating respectively (CdSe)₅ an (CdSe)₆ inside to form a three-dimensional network of essentially hetero-polar sp³-bonding.     

The temporal evolution of the structure and luminescence properties of CdSe semiconductor quantum dots grown at low temperatures

Mono-dispersed CdSe quantum dots have been prepared by water based route using 2-mercaptoethanol at low temperatures. The structures of the CdSe nanocrystals were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The XRD pattern showed that the prepared CdSe has a cubic phase with zinc blende structure. The temporal evolution of the absorption and photoluminescence spectra was used to follow the reaction process and to characterize the optical properties of the prepared CdSe quantum dots. The results exhibited clear exciton peaks in the absorption spectra. The influence of the temperature and/or time of reaction on the properties of the CdSe nanocrystals were investigated. It is found that the size of CdSe nanoparticles increases, as the reaction temperature and/or time are increased. The results showed that the Stokes shift between photoluminescence emission peak and absorption peaks is increased with the increase of the reaction temperature.     

Ultrafast spectroscopy of CdS/CdSe quantum dots

Results from the nonresonance spectroscopy of CdS/CdSe quantum dots (composites of CdSe–CdS nanoparticles (core–shell)) are presented. The nonlinear optical properties of CdS/CdSe QDs in PMMA are studied with fs pulses at 1053 nm using the transient lens technique. QDs generate rapidly oscillating signals with amplitude rise times of around 200 fs and decay times of around 500 fs, while pure PMMA polymer only generates an oscillating signal whose envelope coincides with its autocorrelation function.     

真空蒸发CdSe1-xTex薄膜的光电导特性

本文采用CdSe和CdTe混合物作为真空蒸发源材料,制备了CdSe1-x、Tex(0相似文献   

Studies on photoinduced effects in pulse-electrodeposited Ag/Hg-1212/CdSe hetero-nanostructures

Metal/superconductor/semiconductor (Ag/Hg-1212/CdSe) hetero-nanostructures have been fabricated using pulse-electrodeposition technique and are characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy (SEM) studies. The junction capacitance of Ag/Hg-1212, Hg-1212/CdSe and Ag/Hg-1212/CdSe heterojunctions is measured in dark and under laser irradiation at room temperature. The nature of the junction formed and built-in-junction potentials were determined. The increase in carrier concentration across the junction due to photo-irradiation has been observed.     

Re-charging the luminescence states in CdSe/ZnS quantum dots at the conjugation to Osteopontin antibodies

The paper presents the original study of photoluminescence (PL) and Raman scattering spectra of core–shell CdSe/ZnS quantum dots (QDs) covered by the amine-derivatized polyethylene glycol (PEG) with luminescence interface states. First commercially available CdSe/ZnS QDs with emission at 640 nm (1.94 eV) covered by PEG polymer have been studied in nonconjugated states. PL spectra of nonconjugated QDs are characterized by a superposition of PL bands related to exciton emission in a CdSe core and to the hot electron–hole recombination via high energy luminescence states. The study of high energy PL bands in QDs at different temperatures has shown that these PL bands are related to luminescence interface states at the CdSe/ZnS or ZnS/polymer interface. Then CdSe/ZnS QDs have been conjugated with biomolecules—the Osteopontin antibodies. It is revealed that the PL spectrum of bioconjugated QDs changed essentially with decreasing hot electron–hole recombination flow via luminescence interface states. It is shown that the QD bioconjugation process to Osteopontin antibodies is complex and includes the covalent and electrostatic interactions between them. The variation of PL spectra due to the bioconjugation is explained on the basis of electrostatic interaction between the QDs and biomolecule dipoles that stimulates re-charging QD interface states. The study of Raman scattering of bioconjugated CdSe/ZnS QDs has confirmed that the antibody molecules have the electric dipoles. It is shown that CdSe/ZnS QDs with luminescence interface states are promising for the study of bioconjugation effects with specific antibodies and can be a powerful technique in biology and medicine.     

Evidence of electron wave function delocalization in CdSe/CdS asymmetric nanocrystals

We studied the delocalization of electron wave function in asymmetric CdSe/CdS nanocrystals, consisting of a spherical CdSe dot embedded in an elongated CdS shell, by means of a pump–probe technique. By comparing the transient spectra obtained upon pumping the band edge transition of the CdSe in CdSe/CdS heterostructure and in a bare CdSe dot, we observed the delocalization of electron wave function at the CdSe/CdS interface.     

Electrosynthesis and characterization of Fe doped CdSe thin films from ethylene glycol bath

The CdSe and Fe doped CdSe (Fe:CdSe) thin films have been electrodeposited potentiostatically onto the stainless steel and fluorine doped tin oxide (FTO) glass substrates, from ethylene glycol bath containing (CH₃COO)₂·Cd·2H₂O, SeO₂, and FeCl₃ at room temperature. The doping concentration of Fe is optimized by using (photo) electrochemical (PEC) characterization technique. The deposition mechanism and Fe incorporation are studied by cyclic voltammetry. The structural, surface morphological and optical properties of the deposited CdSe and Fe:CdSe thin films have been studied by X-ray diffraction, scanning electron microscopy (SEM) and optical absorption techniques respectively. The PEC study shows that Fe:CdSe thin films are more photosensitive than that of undoped CdSe thin films. The X-ray diffraction analysis shows that the films are polycrystalline with hexagonal crystal structure. SEM studies reveal that the films with uniformly distributed grains over the entire surface of the substrate. The complete surface morphology has been changed after doping. Optical absorption study shows the presence of direct transition and a considerable decrease in bandgap, E_g from 1.95 to 1.65 eV.     

CdSe:Nd纳米晶及CdSe:Nd@SiO2核壳结构的合成及发光性能

利用有机相法合成Nd³⁺掺杂CdSe纳米晶（CdSe∶Nd）,通过X射线粉末衍射（XRD）、透射电镜（TEM）、紫外吸收光光谱及荧光光谱表征,证明Nd³⁺已经成功掺入到CdSe的晶格中。与纯CdSe纳米晶相比,CdSe∶Nd纳米晶的结构仍为立方晶型,且形貌近似球形,均匀分散,粒径约为2~4 nm。紫外吸收峰和荧光发射峰都发生红移,而且掺杂后的CdSe∶Nd纳米晶量子产率也提高,这可能是由于掺杂Nd³⁺引入了新的杂质能级,带隙减小。为了实现CdSe∶Nd纳米晶的可加工性和功能性,通过微乳法合成SiO₂壳包覆的CdSe∶Nd纳米球（CdSe∶Nd@SiO₂纳米球）,CdSe∶Nd@SiO₂纳米球呈均匀球形,直径约为100~115 nm,并且包壳后的CdSe∶Nd@SiO₂纳米球发射峰（581 nm）与CdSe∶Nd纳米晶（598 nm）相比,发光强度提高且发射峰蓝移,蓝移约为17 nm,可能是因为SiO₂壳可以减少纳米晶表面的非辐射跃迁以及改善表面缺陷导致的。     

Al/CdSe/GaSe/C resonant tunneling thin film transistors

An Al/CdSe/GaSe/C thin film transistor device was prepared by the physical vapor deposition technique at a vacuum pressure of 10⁻⁵ mbar. The x-ray diffraction measurements demonstrated the polycrystalline nature of the surface of the device. The dc current-voltage characteristics recorded for the Al/CdSe/C and Al/CdSe/GaSe/C channels displayed a resonant tunneling diode features during the forward and reverse voltage biasing, respectively. In addition, the switching current ratio of the Al/CdSe/C increased from 18.6 to 9.62×10³ as a result of the GaSe deposition on the CdSe surface. Moreover, the alternating electrical signal analyses in the frequency range of 1.0 MHz to 1.8 GHz, showed some remarkable properties of negative resistance and negative capacitance spectra of the Al/CdSe/GaSe/C thin film transistors. Two distinct resonance-antiresonance phenomena in the resistance spectra and one in the capacitance spectra were observed at 0.53, 1.04 and 1.40 GHz for the Al/CdSe/C channel, respectively. The respective resonating peak positions of the resistance spectra shift to 0.38 and 0.95 GHz when GaSe is interfaced with CdSe. These features of the thin film transistors are promising for use in high quality microwave filtering circuits and also for use as ultrafast switches.     

CdSe/ZnSe/ZnS多壳层结构量子点的制备与表征

展示了一种简捷的多壳层量子点合成路线。在含有过量Se源的CdSe体系中直接注入Zn源,"一步法"合成了CdSe/ZnSe量子点;进一步以CdSe/ZnSe为"核",表面外延生长ZnS壳层制备了核/壳/壳结构CdSe/ZnSe/ZnS量子点。相对于以往报道的多壳层结构量子点的制备方法,该方法通过减少壳层的生长步骤有效地简化了实验操作,缩短了实验周期,同时减少对原料的损耗。对量子点进行高温退火处理,能够大幅提高CdSe/ZnSe/ZnS量子点的发光量子产率。透射电镜、XRD以及光谱研究表明:所制备的量子点接近球形,核与壳层纳米晶均为闪锌矿结构,最终获得的CdSe/ZnSe/ZnS量子点的光致发光量子产率达到53％。为了实现量子点的表面生物功能化,通过巯基酸进行了表面配体交换修饰,使量子点表面具有水溶性的羧基功能团,并且能够维持较高的光致发光量子产率。     

A novel two-phase thermal approach for synthesizing CdSe/CdS core/shell nanostructure

CdSe/CdS core/shell nanocrystals have been synthesized through a low cost and simple two-phase thermal route. The optical spectroscopy and structural characterization evidenced the core/shell structure of the CdSe/CdS nanoparticles. The X-ray diffraction patterns of CdSe and CdSe/CdS nanoparticles exhibited peak positions corresponding to those of their bulk cubic crystal structures. The X-ray photoelectron spectroscopy data confirmed the elemental composition of the CdSe/CdS nanoparticles. The absorption spectra of core/shell nanoparticles showed red shift with respect to the core CdSe nanoparticles. The photoluminescence study indicates that the intensity of the emission maximum is considerably increased in the core/shell structure as compared with the parent material, and the capping of CdS nanoparticles with CdSe material exhibit a near band-edge emission, indicating a successful passivation by removing surface defects. The high-resolution transmission microscope images of the bare and core/shell nanoparticles ascertained the monodispersed and well-defined spherical particles. The average particle sizes for CdSe and CdSe/CdS nanoparticles are 2.5 and 5 nm, respectively, thus confirming, the larger diameter of CdSe/CdS core/shell nanostructure than the core CdSe nanoparticles.     

Direct and stepwise energy transfer from excitons to plasmons in close-packed metal and semiconductor nanoparticle monolayer films

We studied the dynamics of photoluminescence (PL) and energy transfer in close-packed monolayer films of CdSe and Au nanoparticles (NPs) assembled using the Langmuir-Blodgett technique. The PL intensity and dynamics depended on the ratio of CdSe to Au NPs in the mixed films. The PL quenching of CdSe NPs occurs through rapid energy transfer from excitons in CdSe NPs to plasmons in Au NPs. The PL decay curves of the mixed NPs monolayers are determined by three decay rates: the direct energy transfer between the nearest-neighbor CdSe and Au NPs (CdSe-->Au), the stepwise energy transfer from CdSe to CdSe to Au NPs (CdSe-->CdSe-->Au), and the radiative recombination in CdSe NPs.     

Surface control of CdSe nanocrystals by UV-exposure in air and successive thermal treatment under ultra high vacuum

Colloidal CdSe nanocrystals were synthesized through a solution process. The CdSe nanocrystals coated on Si(1 0 0) wafers were UV-exposed in either an air or argon atmosphere to distinguish the effect of generated ozone from UV-radiation at 365 nm on the removal of surface capping pyridine molecules. The pyridine on the CdSe nanocrystal's surface could be effectively removed by the ozone generated during UV-exposure with an accompanying highly oxidized surface state of the CdSe nanocrystals. For the removal of surface oxides of CdSe nanocrystals, a successive thermal treatment under ultra high vacuum (UHV) was adopted. The optical energy bandgap measured by using UV-vis absorption spectroscopy showed a red shift with treatment with an increase of annealing temperature. The electronic energy structure of UHV-annealed CdSe nanocrystals film was analyzed in situ using X-ray absorption and photoelectron spectroscopy. A great resemblance was found between the values of the optical and electron energy bandgaps of effectively surface-treated CdSe nanocrystals film after UHV-annealing at 400 °C.     

TiO2/CdSe多层膜结构的制备及光电化学性能研究

采用电化学方法在导电的ITO/TiO₂ 薄膜上沉积了棕红色CdSe薄膜, 并制得TiO₂/CdSe多层膜体系,研究了多层膜的微结构和光电化学性能. 实验表明, CdSe薄膜沿着(111)方向择优生长, 多层膜结构的厚度和紫外-可见光吸收强度随着沉积层数的增加而增加. 通过测定多层膜电极的光电化学性能表明, 二层膜体系的开路电压和短路电流密度最大,光电化学性能最好.