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71.
72.
M. MolaeiE. Saievar Iranizad M. MarandiN. Taghavinia R. Amrollahi 《Applied Surface Science》2011,257(23):9796-9801
We have synthesized CdS nanocrystals (NCs) by a microwave activated method. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The aqueous synthesis was based on the heat sensitivity of Na2S2O3. In this method, microwave irradiation creates the activation energy for dissociation of Na2S2O3 and leads to the CdS NCs formation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses demonstrated hexagonal phase CdS NCs with an average size around 3 nm for sample prepared at 5 min irradiation time. A band gap range of 3.38-2.89 eV was possible only by increasing the microwave irradiation time, corresponding to a 2.7-3.7 nm size. Photoluminescence (PL) spectra showed a white emission between 400 and 750 nm. The best attained PL quantum yield (QY) of the NCs was about 10%. Synthesized NCs were used as emissive layer in a light emitting device (LED) with ITO/PEDOT:PSS/PVK/CdS-NCs/AL structure. Turn on voltage of fabricated device was about 7 V. The CIE color coordinate of the LED at (0.34, 0.43) demonstrated a near white light LED with an emission on green-yellow boundary of white. 相似文献
73.
Kaushik Pal Uday Narayan Maiti Tapas Pal Majumder Subhas Chandra Debnath 《Applied Surface Science》2011,258(1):163-168
A series of novel wurtzite cadmium sulphide (CdS) nanowires with uniform diameter were synthesized by using a rapid and simple solvothermal route. CdS nano structures with certain morphology could be selectively produced by only varying the concentration of poly ethylene glycol (PEG) as a surfactant in the reaction system with cadmium acetate, sulphur powder and ethelynediamine (EDA). We extensively studied UV-vis absorption spectra, photoluminescence spectra after confirming CdS nanowires with diameter 24-25 nm and length ranging up to several nano meters by field emission scanning electron microscopy (FE-SEM). Therefore we may definitely propose a new formation mechanism of CdS nanowires assisted by PEG with its illustrating optical properties. 相似文献
74.
R. Castro-Rodríguez J. Mendez-GamboaI. Perez-Quintana R. Medina-Ezquivel 《Applied Surface Science》2011,257(22):9480-9484
CdS thin films were grown by fast evaporation technique combined with substrate rotation. The source evaporation temperature was maintained at 600 °C and the substrate temperature at 350 °C with background pressure of 1.0 m Torr. The substrates were corning glass 2947 with dimension of 1 in. × 1 in. rotate at 500 rpm during the growth. In order to verify the quality of the CdS films, the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical measurements. The films shown a flat uniformity thickness with growth rate of ∼3.5 nm/s, the orientation was in the cubic-(1 1 1) and hexagonal-(0 0 2) plane in dependence of the growth time, grain size ∼5 nm, roughness uniformity ∼2.7 nm, transmittance in the visible region spectrum ∼80%, energy band gap between 2.39 and 2.42 eV and short circuit photocurrent density (JSC) losses in the CdS films of 4.7 mA/cm2. 相似文献
75.
Blue-emitting colloidal CdS nanocrystals have been synthesized through the solvothermal reaction of cadmium acetate and thiourea
in N,N-dimethylformamide using poly(ethylene oxide; PEO) as the stabilizing polymer. The as-prepared CdS colloids were stable at
ambient conditions for several weeks. The PEO-stabilized CdS colloids showed a narrow fluorescence band with the maximum at
about 420 nm and thus emitting blue fluorescence under the ultraviolet (UV) lamp. A common red shift of fluorescence band
is not detected for the prepared CdS colloids in the study, indicating that PEO-stabilized CdS NCs possess few crystalline
defects on their surface. In addition, transmission electron microscope micrographs reveal that the sizes of CdS NCs are between
4.4 to 5.4 nm with small standard deviations from 0.5 to 0.7 nm. The particle growth kinetics was studied by monitoring UV-visible
absorption onsets versus the reaction time and was found to nearly follow the Lifshitz–Slyozov–Wagner theory for the Ostwald
ripening mechanism. 相似文献
76.
李春霞 《原子与分子物理学报》2007,24(5):1060-1064
基于密度泛函理论(DFT)的第一性原理方法(DMOL3程序),在广义梯度近似(GGA)下,计算了中小尺寸II~VI族(CdS)n和(CdTe)n团簇的基态结构、最高占据轨道(HOMO)和最低未占据轨道(LUMO)的能隙、结合能等,比较了(CdS)n和(CdTe)n两种团簇的基态结构,能隙与结合能随尺寸变化关系的差异等. 相似文献
77.
Nicolás de la Rosa-Fox Manuel Piñero Rocío Litrán Luis Esquivias 《Journal of Sol-Gel Science and Technology》2003,26(1-3):947-951
CdS semiconductor nanocrystals were grown as quantum dots (QDs) inside a silica matrix obtained by the sol-gelmethod and assisted in the mother liquid by high powerultrasounds. Small-angle neutron scattering (SANS) accountsfor a 3.6 nm crystal size homogeneously distributed. Optical excitation from the third harmonic of a Nd:YAG ns laser wasfocused on the sample to study the photoluminescence (PL) atroom temperature. The PL spectrum shows radiative processfrom intrinsic transitions and a broad band corresponding tothe traps. Variable stripe length (VSL) method was used to measure the optical gain spectra by the growth of theamplified luminescence. A broad optical gain spectrumproduced by the biexciton-exciton transitions revealing thestimulated emission from the CdS QDs. It is also observed ared-shift of the PL emission crystal size-dependent. 相似文献
78.
A photoelectroactive film composed of CdS quantum dots and graphene sheets (GS) was coated on F-doped SnO2 (FTO) conducting glass for studying the electrochemical response of p-phenylenediamine (PPD) under photoirradiation. The result indicated that the cyclic voltammogram of PPD on CdS–GS hybrid film became sigmoidal in shape after exposed under visible light, due to the photoelectrocatalytic reaction. Such a photovoltammetric response was used to rapidly optimize the photoelectrocatalytic activity of hybrid films composed of different ratios of CdS to GS toward PPD. The influences of scan rate and pH on the photovoltammetric behavior of PPD on CdS–GS film revealed that although the controlled step for electrochemical process was not changed under photoirradiation, more electrons than protons might participate the photoelectrocatalytic process. Furthermore, the photoelectroactive CdS–GS hybrid film was explored for PPD determination based on the photocurrent response of film toward PPD. Under optimal conditions, the photocurrent signal on CdS–GS film was linearly proportional to the concentration of PPD ranging from 1.0 × 10−7 to 3.0 × 10−6 mol L−1, with a detection limit (3S/N) of 4.3 × 10−8 mol L−1. Our work based on CdS–GS hybrid film not only demonstrated a new facile photovoltammetric way to study the photoinduced electron transfer process of PPD, but also developed a sensitive photoelectrochemical strategy for PPD determination. 相似文献
79.
We have developed an analytical method to detect adenosine-5′-triphosphate (ATP) and alkaline phosphatase (ALP) based on the generation of CdS quantum dots (QDs). We demonstrated that Cd2+ cation reacts with S2− anion to generate fluorescent CdS QDs in the presence of some certain amount of ATP. With increase in the ATP concentration, the fluorescence intensity of CdS QDs was also enhanced. ATP can be converted into adenosine by the dephosphorylation of ALP, so that the generation of CdS QDs would be inhibited in the presence of ALP. Therefore, this novel analysis system could be applied to assay ATP and ALP based on the growth of fluorescent CdS QDs. 相似文献
80.
开发了一种以聚乙烯吡咯烷酮为分散剂和稳定剂经条件温和的室温水相合成光谱可调的水溶性CdTe/CdS核/壳结构量子点的方法:向新鲜制备的CdTe量子点溶液中加入硫源,继续反应即可生成CdS壳层,通过控制硫源的浓度即可控制CdS壳层厚度,从而调节光谱性质和增强稳定性.采用XRD、TEM、HRTEM、荧光光谱以及紫外-可见光... 相似文献