共查询到20条相似文献,搜索用时 15 毫秒
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G. Murugadoss 《Journal of luminescence》2012,132(10):2665-2669
Excellent luminescence properties of ZnS/CdS/ZnO and ZnO/ZnS/CdS nanocrystallites synthesized through a simple chemical method at room temperature are reported. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), UV–visible absorption and photoluminescence techniques were used to characterize the undoped ZnS, CdS and ZnO and the novel ZnS/CdS/ZnO and ZnO/ZnS/CdS nanoparticles. The optical properties of ZnS/CdS/ZnO and ZnO/ZnS/CdS nanoparticles reflect a combinational effect of the photoluminescent properties of ZnS, CdS and ZnO. 相似文献
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本文用高阶Mie散射理论研究了CdS、ZnS毫微晶的吸收(消光)光谱及其随微晶尺寸的变化,提出了在CdS、ZnS毫微晶半径大于~10nm时,吸收峰及吸收边的蓝移主要由经典尺寸效应所引起;在毫微晶半径小于~10nm时,吸收的蓝移主要是量子尺寸效应的贡献. 相似文献
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采用反胶束方法制备了ZnS/CdS/ZnS量子点量子阱,并对其光谱性质进行了研究。结果表明所制得的量子点量子阱尺寸分布均匀,平均粒径为4.5nm,发光峰位于515nm左右,归属于CdS体内的施主-受主对复合。ZnS/CdS/ZnS量子点量子阱中CdS的发光比核-壳结构的ZnS/CdS量子点增强了近四倍,荧光寿命也有所增长。 相似文献
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EPR measurements were carried out on nickel doped ZnS and CdS crystals at 4.2°K and 9.3 Gc/sec. In ZnS crystals the isotropic line corresponding to the naturally occuring nickel isotopes 58Ni and 60Ni is significantly narrower than previously reported. The single line attributed to natural nickel has been observed in CdS crystals. The hyperfine structure has been studied on samples enriched in 61Ni. The angular dependence has been thoroughly investigated. 相似文献
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Graphene-based nanocomposites are emerging as a new class of materials that hold promise for many applications. In this paper, we present a facile approach for the preparation of graphene/CdS nanocomposites through simple reflux processes, in which thiourea (CS(NH2)2) and thioacetamide (C2H5NS) act as a sulphide source, respectively. The samples were characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectrum (FT-IR), ultraviolet-visible (UV-vis) spectroscopy and thermogravimetry analysis. It was shown that in the nanocomposites, the CdS nanoparticles were densely and uniformly deposited on the graphene sheets, and the sulphide source used has a great influence on the morphology, structure and property of the graphene/CdS nanocomposites. The good distribution of CdS nanoparticles on graphene sheets guarantees the efficient optoelectronic properties of graphene/CdS and would be promising for practical applications in future nanotechnology. 相似文献
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Auger processes are investigated for CdS/ZnS core-shell quantum dots. Auger recombination (AR) lifetime and electron relaxation inside the core are computed. Using the effective-mass theory and by solving a three-dimension Schrödinger equation we predict the dependence of Auger relaxation on size of core-shell nanocrystals. We considered in this work different AR processes: the excited electron (EE), excited hole (EH), multiexciton AR type. Likewise, Auger multiexciton recombination rates are predicted for biexciton. Our results show that biexciton AR type is more efficient than the other AR process (excited electron (EE) and excited hole (EH)). We also found that electron Auger relaxation P→S is very efficient in core-shell nanostructures. 相似文献
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M. S. Smirnov D. I. Stasel’ko O. V. Ovchinnikov A. N. Latyshev O. V. Buganov S. A. Tikhomirov A. S. Perepelitsa 《Optics and Spectroscopy》2013,115(5):651-659
Using the spectral methods of induced absorption, luminescence, and photostimulated luminescence flash, we have experimentally investigated processes of decay of electronic excitations in CdS colloidal quantum dots and in CdS/ZnS “core-shell” systems synthesized in gelatin by the sol-gel method. It has been shown that the decay of electronic excitations in colloidal quantum dots of this type is predominantly related to a fast localization of nonequilibrium charge carriers on surface defects and their subsequent recombination during times on the order of units and tens of picoseconds. The passage to core-shell systems eliminates, to a large extent, surface defects of the core, some of which are luminescence centers. However, upon using the sol-gel synthesis, a noticeable fraction of luminescence centers are formed in the interior of the CdS quantum dot, which, as well as in the case of CdS/ZnS systems, ensures localization of exciton, blocks its direct annihilation, and maintains recombination radiation. 相似文献
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CdS, ZnS and ZnCdS nanoparticles of various sizes (1–10 nm) are synthesized using a wet chemical route including passivation by organic capping molecules. The particles can also be doped with transition metal ions. The optical properties of the particles are investigated using UV absorption and photoluminescence spectroscopies. High resolution photoelectron spectroscopy using variable photon energy from a synchrotron source is performed to obtain detailed information about the nanoparticle surfaces. These investigations are able to reveal the termination of the nanoparticles and the nature of bonding between the surface atoms and stabilizing organic molecules. 相似文献
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It has been a general opinion that the Clausius-Mossotti dielectric theory is not capable of explaining the observed photoelastic behaviour of partially ionic crystals.However in the present communication we show that by making account of the variation of polarizabilities under compressive stress within the framework of the Clausius-Mossotti theory it is possible to obtain a reasonable agreement with experimental data on the photoelastic behaviour of ZnO, ZnS and CdS crystals. 相似文献
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S. V. Petrushkin 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(3):276-278
The possibility of using CdS nanocomposites for optical cooling is analyzed on the basis of their spectroscopic properties.
The physical principles of laser cooling in semiconductor structures are discussed. 相似文献
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P. Sreekumari Nair T. Radhakrishnan N. Revaprasadu A.S. Luyt 《Journal of Physics and Chemistry of Solids》2005,66(7):1302-1306
Composites of CdS nanoparticles confined in a polystyrene-co-maleic acid (PS-co-MAc) matrix have been prepared and characterized. It was shown that the acid groups of the co-polymer could be successfully used to control the aggregation of the nanoparticles, because they act as coordinate sites for Cd ions. UV-VIS measurements showed a blue shift of the absorption threshold, proving the presence of nanoparticles. An average size of the nanoparticles of about 4 nm is estimated from the change in band gap energy. Although the FTIR spectrum of the nanocomposite showed the presence of C-S bonds, a broad emission originating from surface recombination sites are noticed. DSC and TGA measurements revealed changes in thermal properties upon incorporation of nanoparticles. No thermal transition was observed in the nanocomposite, while the pure co-polymer exhibits a glass transition at 190 °C. In the presence of nanoparticles the onset of the thermal decomposition of the matrix is also shifted by 50 °C towards a higher temperature. 相似文献
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Electron–phonon effects on the two first electronic states in both CdS and GaAs quantum dots are investigated. Both confined longitudinal optical (LO) and surface optical (SO) phonons are considered. We use the intermediate-type variational approach. We find that, shifts caused by phonon contribution on electronic energies are more significant for CdS quantum dot. We find, also, that, contrary to GaAs based quantum dots, we shouldn’t neglect the SO phonon contribution for CdS based ones, especially for small dots. 相似文献
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核壳结构CdS/ZnS纳米微粒的制备与光学特性 总被引:6,自引:0,他引:6
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 . 相似文献