核/壳结构ZnS : Mn/CdS纳米粒子的制备及发光

利用溶剂热法制备了Mn离子掺杂的ZnS纳米粒子(ZnS : Mn),利用沉淀法对ZnS ∶ Mn纳米粒子进行了不同厚度的CdS无机壳层包覆。采用X射线衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)及光致发光(PL)光谱等手段对样品进行了表征。TEM显示粒子为球形,直径大约在14~18 nm之间。由XRD结果可以看出CdS壳层的形成过程受到了ZnS ∶ Mn核的影响,导致其结晶较差。XRD和XPS测量证明了ZnS : Mn/CdS的核壳结构。随着CdS壳层的增厚,样品的发光强度呈现一直减弱的现象。     

核壳结构CdS/ZnS纳米微粒的制备与光学特性

用微乳液法制备CdS纳米微粒 ,以ZnS对其进行表面修饰 ,得到具有核壳结构的CdS/ZnS纳米微粒 .采用X射线衍射 (XRD)、透射电镜 (TEM )表征其结构、粒度和形貌 ,紫外 可见吸收光谱 (UV)、光致发光光谱(PL)表征其光学特性 .制得的CdS近似呈球形 ,直径为 3.3nm ;以XRD和UV证实了CdS/ZnS核壳结构的实现 .研究了不同ZnS壳层厚度对CdS纳米微粒光学性能的影响 ,UV谱表明随着壳层厚度的增加纳米微粒的吸收带边有轻微的红移 ,同时短波吸收增强 ;PL谱表明壳层ZnS的包覆可减少CdS纳米微粒的表面缺陷 ,带边直接复合发光的几率增大 ,具有合适的壳层厚度时发光效率大大提高 .     

CdS/ZnO纳米复合结构的制备、表征及其光催化活性的改善

利用简单的水热法在ZnO纳米棒表面合成CdS纳米粒子.用扫描电镜(SEM)和X射线衍射(XRD)对CdS/ZnO异质结构进行表征.实验结果表明,在生长CdS的过程中ZnO被逐渐地腐蚀.选择CdS/ZnO纳米复合材料作为光催化剂在紫外光和绿光照射的条件下降解甲基橙(MO).CdS/ZnO纳米复合材料纳米棒作为光催化剂降解...     

HgTe/CdS/ZnS多壳层量子点的制备与表征

采用一种简单的方法合成HgTe/CdS/ZnS多壳层量子点。首先,以1-硫代甘油为稳定剂,在水相溶液中制备出HgTe核量子点;然后,采用外延生长法依次在HgTe核量子点表面包覆CdS和ZnS壳层,合成出最终具有稳定近红外发光的HgTe/CdS/ZnS多壳层量子点。该合成方法仅需3个步骤,具有操作简单、成本低廉的优点。实验结果显示,当反应温度为90 ℃、反应溶液pH为11.0、反应加热回流时间为4 min时,HgTe/CdS/ZnS多壳层量子点具有最高荧光量子产率36%。     

g-C3N4/CdS异质结紫外-可见光电探测器的制备及其性能研究

通过热聚法以三聚氰胺为原料制备g-C_3N_4纳米片,然后采用化学水浴法生长CdS纳米颗粒,进而成功构筑g-C_3N_4/CdS异质结构。采用扫描电子显微镜,X射线衍射仪和X射线光电子能谱仪对样品的微观形貌、晶体结构和化学成分进行表征。结果表明,CdS纳米颗粒为六方纤锌矿结构,且均匀致密地附着在g-C_3N_4纳米片表面;g-C_3N_4/CdS探测器能够在零偏压工作条件下对紫外光有较好的光响应,且光电流值较g-C_3N_4纳米片探测器提高了约8倍。此外,g-C_3N_4/CdS探测器在可见光区也表现出良好的光响应,对蓝光和绿光多个周期探测的结果也表明其具有稳定性和循环性。     

异质结型CuO/ZnO复合纳米线的制备及光催化性能

在室温下,通过溶液法在Cu衬底上制备了CuO纳米线,然后采用溶剂热法在CuO纳米线表面生长ZnO纳米颗粒以构建CuO/ZnO复合纳米线异质结构。利用扫描电镜、透射电镜、X射线衍射仪和X射线光电子能谱分析了样品的形貌、结构和元素组成。结果显示CuO/ZnO复合纳米线由ZnO纳米颗粒和CuO纳米线组成。在模拟太阳光照射下,以亚甲基蓝溶液为模拟污染物研究了样品的光催化性能。结果表明,相比纯CuO纳米线,CuO/ZnO复合纳米线能够使亚甲基蓝溶液的光降解效率达到40%,在相同条件下具有更优异的光催化活性。光催化机理研究表明CuO/ZnO纳米复合材料光催化活性的增强主要是由于CuO与ZnO结合形成的p-n异质结有效促进了光生载流子的分离。     

ZnS/CdS复合窗口层对CdTe太阳能电池短波光谱响应的影响

采用磁控溅射法制备了ZnS/CdS复合窗口层,并将其应用于CdTe太阳能电池。对所制备薄膜的形貌和结构等进行了研究。测试了具有不同窗口层的CdTe太阳电池的量子效率和光Ⅰ-Ⅴ特性,分析了ZnS薄膜制备条件对CdTe电池器件性能影响;研究了CdS薄膜厚度和ZnS/CdS复合窗口层对短波区透过率以及CdTe太阳电池的光谱响应的影响。着重研究了具有ZnS/CdS复合窗口层的CdTe太阳电池的短波光谱响应。结果表明,CdS窗口层厚度从100 nm减至50 nm后,其对短波区光子透过率平均提高了18.3%,CdTe太阳电池短波区光谱响应平均提高了27.6%。衬底温度250 ℃条件下制备的ZnS晶粒尺寸小于室温下制备的ZnS。具有ZnS/CdS复合窗口层的CdTe电池中,采用衬底温度250 ℃沉积ZnS薄膜来制备窗口层的电池器件,其性能要优于室温下沉积ZnS制备窗口层的电池器件。这说明晶粒尺寸的大小对电子输运有一定影响。在相同厚度CdS的前提下,具有ZnS/CdS复合窗口层的CdTe电池比具有CdS窗口层在短波的光谱响应提高了约2%。这说明ZnS/CdS复合窗口层能够做到减少对短波光子的吸收,从而使更多的光子被CdTe电池的吸收层吸收。     

真空热蒸发生长CdX(X=S,Te)纳米线研究性实验

将一维纳米结构的气—液—固生长机制与大学材料物理实验真空热蒸发镀膜结合,设计了生长半导体纳米线的研究性实验.利用金属铋或锡作为催化剂,真空热蒸发生长了CdS,CdTe等半导体纳米线.纳米线产物形貌均匀,并可实现选择性生长.     

ZnSe(ZnS)纳米晶与MEH-PPV的共掺有机电致发光器件

采用水相法合成核壳结构ZnSe/ZnS 纳米晶,经X射线衍射(XRD)分析和透射电子显微镜(TEM)表征,证实所制备的样品为立方晶型闪锌矿结构ZnSe/ZnS量子点。按照一定的质量比将ZnSe/ZnS 纳米晶和有机聚合物MEH-PPV(poly ) 共掺并将其作为发光层,分别制备单层和多层有机电致发光器件,结构为ITO/MEH-PPV∶ZnSe(ZnS)(50 nm)/Al和 ITO/PEDOT∶PSS(70 nm)/ MEH-PPV∶ZnSe(ZnS)(50 nm)/BCP(15 nm)/Alq₃(12 nm) /LiF(0.5 nm)/Al。实验结果表明,多层发光器件的发光特性与单层器件不同,工作电压的增大使其发光峰发生了明显的蓝移。     

金辅助催化方法制备GaAs和GaAs/InGaAs纳米线结构的形貌表征及生长机理研究

利用金（Au）辅助催化的方法,通过金属有机化学气相沉积技术制备了GaAs纳米线及GaAs/InGaAs纳米线异质结构.通过对扫描电子显微镜（SEM）测试结果分析,发现温度会改变纳米线的生长机理,进而影响形貌特征.在GaAs纳米线的基础上制备了高质量的纳米线轴、径向异质结构,并对生长机理进行分析.SEM测试显示,GaAs/InGaAs异质结构呈现明显的“柱状”形貌与衬底垂直,InGaAs与GaAs段之间的界面清晰可见.通过X射线能谱对异质结样品进行了线分析,结果表明在GaAs/InGaAs轴向纳米线异质结构样品中,未发现明显的径向生长.从生长机理出发分析了在GaAs/InGaAs径向纳米线结构制备过程中伴随有少许轴向生长的现象.     

氧化锌/硫化锌异质纳米线结构和电子性质比较研究

用第一性原理方法系统研究氧化锌/硫化锌超晶格纳米线和核壳结构纳米线的结构和电子性质.结构优化后,氧化锌/硫化锌异质结构纳米线和纯氧化锌或硫化锌纳米线结构相似.对于两种异质结构纳米线,能带结构显示他们都是直接带隙半导体.对于氧化锌/硫化锌超晶格纳米线,随着径向厚度的增加,能带变的越来越水平.对于核壳结构纳米线,分波态密度显示它们都是Ⅱ型异质结构.研究有助于理解这类异质结构纳米线以及它们在电子发动机及光伏设备方面的应用.     

Atomistic tight-binding computations of the structural and optical properties of CdTe/CdX (X=S and Se)/ZnS core/shell/shell nanocrystals

A study of CdTe/CdX (X=S and Se)/ZnS core/shell/shell nanocrystals is carried out using atomistic tight-binding theory and the configuration interaction method to provide information for applications in bioimaging, biolabeling, display devices and near-infrared electronic instruments. The calculations yield the dependences of the internal and external passivated shells on the natural behaviours of CdTe/CdX (X=S and Se)/ZnS core/shell/shell nanocrystals. The reduction of the optical band gaps is observed with increasing numbers of monolayers in the external ZnS shell due to quantum confinement. Interestingly, the optical band gaps of CdTe/CdS/ZnS core/shell/shell nanocrystals are greater than those of CdTe/CdSe/ZnS core/shell/shell nanocrystals. In the presence of an external ZnS-coated shell, electron–hole wave function overlaps, oscillation strengths, ground-state exchange energies and Stokes shift are improved, whereas ground-state coulomb energies and fine-structure splitting are reduced. The oscillation strengths, Stokes shift and fine-structure splitting are reduced with the increase in external ZnS shell thickness. The oscillation strengths, Stokes shift and fine-structure splitting of CdTe/CdS/ZnS core/shell/shell nanocrystals are larger than those of CdTe/CdSe/ZnS core/shell/shell nanocrystals. Reduction of the atomistic electron–hole interactions is observed with increasing external ZnS shell size. The strong electron–hole interactions are more probed in CdTe/CdS/ZnS core/shell/shell nanocrystals than in CdTe/CdSe/ZnS core/shell/shell nanocrystals.     

单核/双壳结构CdSe/CdS/ZnS纳米晶的合成与发光性质

以巯基乙酸为稳定剂,在水溶液中合成了单核/双壳结构的CdSe/CdS/ZnS纳米晶。在内核CdSe和外壳ZnS之间的内壳CdS作为晶格匹配调节层,能够很好的改善核/壳界面处的性能,而且,最外层ZnS能够最大程度地使激子受限。用TEM和XPS对纳米晶进行了表征,并且用光致发光光谱和吸收光谱对不同核壳结构的纳米晶的发光性能进行了比较,结果表明单核/双壳结构的纳米晶具有更加优异的发光特性。     

CdS/ZnS core–shell nanoparticles in arachidic acid LB films

Core–shell CdS/ZnS nanoparticles in arachidic acid film were prepared through a novel Langmuir–Blodgett (LB) approach. Post-deposition treatment of the precursor LB multilayers of cadmium arachidate with H₂S gas followed by intercalation of Zn²⁺ ions and further sulfidation result in the formation of CdS/ZnS nanoparticles in the LB film. The formation of these nanoparticles and resulting changes in layered structures were studied by FTIR and X-ray reflection measurements. The optical properties were studied using UV–vis absorption and photoluminescence spectroscopy. A red-shift in the absorption spectrum and enhancement of CdS excitonic emission together with reduction of surface states emission suggest that after the intercalation step, a thin layer of ZnS surrounds the CdS nanoparticles, thus forming a core–shell structure. Subsequent to the second sulfidation, a further red-shift in absorption suggests the formation of a thicker ZnS coating on CdS. Electron diffraction of CdS nanoparticles coated with thicker ZnS showed the diffraction patterns of only ZnS, as expected for core–shell structures.     

Enhancement in the photoluminescence of ZnS nanowires by TiO2 coating and thermal annealing

Influences of the TiO₂ coating and thermal annealing on the photoluminescence (PL) properties of ZnS nanowires were investigated. ZnS nanowires were synthesized by thermal evaporation of ZnS powder and then coated with TiO₂ by using the sputtering technique. The PL emission of ZnS nanowires can be significantly enhanced without nearly changing the wavelength of the emission by coating them with a TiO₂ layer with an appropriate thickness and then annealing them in an Ar atmosphere. The optimum TiO₂ coating layer thickness for the highest PL emission enhancement was found to be about 6.5 nm. The PL emission of the ZnS-core/TiO₂-shell coaxial nanowires is degraded by annealing in an oxygen atmosphere whereas it is enhanced by annealing in an argon atmosphere.     

Metal/semiconductor hybrids consisting of self-assembled CdS nanoparticles on Cd nanowires

We report on the synthesis and the characterisation of metal/semiconductor hybrids consisting of self-assembled CdS nanoparticles on Cd nanowires, which are grown by thermal evaporation of the mixture of CdS and Cr. The growth of the hybrids is attributed to the decomposition of CdS at high temperature and the strain relieving that arises mainly from the lattice mismatch between Cd and CdS. Temperature dependence of zero-field resistance of single nanohybrid indicates that the as-produced Cd/CdS nanohybrid undergoes a metal--semiconductor transition as a natural consequence of hybrid from metallic Cd and semiconducting CdS. The metal/semiconductor hybrid property provides a promising basis for the development of novel nanoelectronic devices.     

Facile synthesis of mercaptosuccinic acid-capped CdTe/CdS/ZnS core/double shell quantum dots with improved cell viability on different cancer cells and normal cells

Water-soluble, mercaptosuccinic acid (MSA)-capped CdTe/CdS/ZnS core/double shell quantum dots (QDs) were prepared by successive growth of CdS and ZnS shells on the as-synthesized CdTe/CdS_thin core/shell quantum dots. The formation of core/double shell structured QDs was investigated by ultraviolet-visible (UV–Vis) absorption and photoluminescence (PL) spectroscopy, PL decay studies, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The core/double shell QDs exhibited good photoluminescence quantum yield (PLQY) which is 70% higher than that of the parent core/shell QDs, and they are stable for months. The average particle size of the core/double shell QDs was ～3 nm as calculated from the transmission electron microscope (TEM) images. The cytotoxicity of the QDs was evaluated on a variety of cancer cells such as HeLa, MCF-7, A549, and normal Vero cells by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) cell viability assay. The results showed that core/double shell QDs were less toxic to the cells when compared to the parent core/shell QDs. MCF-7 cells showed proliferation on incubation with QDs, and this is attributed to the metalloestrogenic activity of cadmium ions released from QDs. The core/double shell CdTe/CdS/ZnS (CSS) QDs were conjugated with transferrin and successfully employed for the biolabeling and fluorescent imaging of HeLa cells. These core/double shell QDs are highly promising fluorescent probe for cancer cell labeling and imaging applications.     

Cell labeling and cytotoxicity of aqueously synthesized CdTe/CdS/ZnS core–shell–shell quantum dots by a water bath-hydrothermal method

CdTe/CdS/ZnS core–shell–shell quantum dots (QDs) were synthesized in aqueous solution via water-bathing combined hydrothermal method using L-cysteine as a stabilizer. The present method features markedly reduced synthesis time, higher fluorescent intensity and lower cytotoxicity of the QDs. Structural and spectroscopic properties of core–shell–shell QDs are well characterized by absorption and fluorescence spectroscopy, X-ray diffraction, transmission electron microscopy, and fourier transform infrared spectroscopy. Both CdS and ZnS shells were capped on the CdTe core and the fluorescence was greatly enhanced by the ZnS coating. The ternary QDs conjugated with transferrins were successfully employed for the biolabeling and fluorescent imaging of HeLa cells. Cytotoxicity evaluation shows that CdTe/CdS/ZnS was less toxic for cells than CdTe and CdTe/CdS due to the presence of a ZnS coating on surface, which inhibited the release of cadmium ions.