Li Yun-Cai

First-principles study of structures and electronic properties of cadmium sulfide clusters

The lowest-energy structures and the electronic properties of CdnSn (n = 1?8) clusters have been studied by using density-functional theory simulating package DMol3 in the generalized gradient approximation (GGA). The ring-like structures are the lowest-energy configurations for n = 2, 3 and the three-dimensional spheroid configurations for n = 4 ? 8. The three-dimensional structures may be considered as being built from the Cd2S2 and Cd3S3 rings. Compared to the previous reports, we have found the more stable structures for CdnSn(n = 7,8). Calculations show that the magic numbers of CdnSn (n = 1 ? 8) clusters are n = 3 and 6. As cluster size increases, the properties of CdnSn clusters tend to bulk-like ones in binding energy per CdS unit and Mulliken atomic charge, obtained by comparing with the calculated results of the wurtzite and zinc blende CdS for the same simulating parameters.

Solvothermal synthesis of CdS nanorods and photovoltaic characteristics of CdS/PVK composite system

Large quantities of CdS nanorods are successfully synthesized through Cd(CH3COO)2·2H2O reacting with Na2S·9H2O and EDA in aqueous solution. XRD result shows that the sample is of hexagonal structure. And TEM result shows that the morphologies of the resulting CdS are mainly in three-armed rod-like structure with a diameter of 10–15 nm and a length of 100 nm. The nanocomposites of CdS/PVK with different molar ratios are prepared by spin coating method on tin-doped indium oxide (ITO) substrate. A notable decrease of photoluminescence (PL) efficiency and a significant enhancement of surface photovoltage signal have been observed in CdS/PVK composites when the molar fraction of CdS increases. We interpret these results as the energy level matching between CdS and PVK in nanocomposites. This energy level matching facilitates fast interfacial charge transfer then increases the separation efficiency of electron-hole pairs and the carrier generation efficiency. The detailed charge transfer process has also been demonstrated.

Synthesis of highly ordered SnO2/Fe2O3 composite nanowire arrays by electrophoretic deposition method

Highly ordered SnO2/Fe2O3 composite nanowire arrays have been synthesized by electrophoretic deposition method. The morphology and chemical composition of SnO2/Fe2O3 composite nanowire arrays are characterized by SEM, TEM, EDX, XPS, and XRD. The results show that the SnO2/Fe2O3 composite nanowires are about 180 nm in width and tens of microns in length, and they are composed of small nanoparticles of tetragonal SnO2 and rhombohedral a-Fe2O3 with diameters of 10–15 nm. The SnO2/Fe2O3 composite nanowires are formed by a series of chemical reactions.