Pure CdS Nanoparticles Research Articles

Synthesis and characterization of bamboo-like CdS/TiO2 nanotubes composites with enhanced visible-light photocatalytic activity

In order to efficiently use the visible light in the photocatalytic reaction, a novel bamboo-like CdS/TiO2 nanotubes composite was prepared by a facile chemical reduction method, in which CdS nanoparticles located in the TiO2 nanotubes. The composition and structure of this nanocomposite were characterized by TEM, HRTEM, XRD, XPS, FTIR and UV-vis spectroscopy. This CdS/TiO2 nanotubes composite exhibited much higher visible-light photocatalytic activity for the degradation of methylene blue than pure TiO2 nanotubes and CdS nanoparticles, and the highest photodegradation efficiency after 6 h irradiation can reach 84.5%. It is inferred that the unique structure of CdS/TiO2 nanotubes composites acts an important role for the improvement of their photocatalytic activity.

Optical and photophysical properties of Ag/CdS nanocomposites—An analysis of relaxation kinetics of the charge carriers

Ag/CdS nanocomposites have been synthesized and characterized by TEM, XRD, electronic and fluorescence spectroscopy. The content of Ag modifies the nature of surface interaction between the two components as revealed by TEM, electronic and fluorescence measurements. Increasing contents of silver in the composite reduces the interparticle separation. The addition of silver blue shifts the absorption maxima and, influences the emission behavior and charge dynamics in a complex manner. At low molar ratio of Ag:CdS about five-fold enhancement in fluorescence is observed which is attributed to the excited state charge transfer interaction between the two components. On the contrary at high Ag the fluorescence intensity is reduced significantly to become smaller than that of pure CdS nanoparticles. The quenching of emission is understood to occur by the rapid electron transfer from the excited CdS to Ag particle. Relaxation kinetics of charge carriers of CdS also reveal the formation of transitory CT complex between excited CdS and Ag, in which the extent of electron transfer is controlled by the amount of Ag and thus supporting the steady-state findings. A mechanism of these processes is discussed.

Fast interfacial charge separation in chemically hybridized CdS-PVK nanocomposites studied by photoluminescence and photoconductivity measurements

Photoinduced charge transfer and separation in chemically hybridized CdS-PVK nanocomposites is investigated by steady-state and time-resolved photoluminescence as well as photoconductivity measurements. The chemically hybridized CdS-PVK composites display a longer luminescence lifetime than the pure CdS nanoparticles. At the same time, they show an enhanced photoconductivity as compared with PVK. It is also found that the chemically hybridized Cd-PVK nanocomposites exhibit a higher photoconductivity than the CdS/PVK nano-blends at the same molar ratio. The photoluminescence and photoconductivity results are explained by fast interfacial charge transfer between the Q-CdS and PVK.

Chemical Design of Nanostructured Luminescent Materials

ABSTRACTDuring the last 50 years, there has been a considerable amount of work for the elaboration of efficient luminescent materials, most of them dealing with the search for new chemical compositions. Only a very few studies have concerned the study of the influence of the microstructure of the materials on their properties of emission, especially when the grain sizes of the materials are in the nanometer range. On another side, important advances have been performed in colloid chemistry in the last years, especially in the case of II-VI chalcogenides, as a consequence on the intense activity around the physics of quantum confinement in semiconductors.The basic idea of this work is to show that the techniques developed in the case of II-VI nanoparticles could find interesting applications for the elaboration of nanostructured luminescent materials. This is first illustrated in the case of pure CdS nanoparticles, whose properties are deeply affected by their surface state and their chemical environment. Incorporation of manganese in solid solution in the CdS particles drastically changes the emission process, which now essentially depends on the manganese content inside each particle. Finally, the extension of the synthesis process to rare earth doped oxide particles is presented, and the luminescence efficiency is discussed as a function of the size, the structure, and the chemical environment of the particles.

Surface and confined optical phonons in CdSxSe1-x nanoparticles in a glass matrix.

We report first- and higher-order Raman scattering from the surface and confined optic phonons in ${\mathrm{CdS}}_{0.65}$${\mathrm{Se}}_{0.35}$ and pure CdS nanoparticles embedded in glass matrix. The average particle sizes and size distribution have been estimated from the quantitative comparison of the blue-shifted optical-absorption spectra with the calculations based on the tight-binding model. The first-order asymmetric Raman line shape has been analyzed by including both the confined optic modes and the surface modes. The average particle sizes so obtained from this analysis compare well with those estimated from the optical-absorption spectra. The observed frequencies of the surface modes have been compared with the results of the dielectric response function model. \textcopyright{} 1996 The American Physical Society.