Highly ordered SnO2/Fe2O3 composite nano- wire arrays have been synthesized by electrophoretic deposi- tion 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 ɑ-Fe2O3 with diameters of 10-15 nm. The SnO2/Fe2O3 com- posite nanowires are formed by a series of chemical reac- tions.
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 enhance-ment of surface photovoltage signal have been observed in CdS/PVK composites when the molar frac-tion 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.
JI YanLing CHENG Ke ZHANG HongMei ZHANG XingTang LI YunCai DU ZuLiang
Sodium titanate nanotubes have been prepared and modified chemically with CdSe quantum dots (QDs) using bifunctional modifiers (HS-COOH). Their photovoltaic characteristics have also been studied. The results indicate that the surface photovoltage response of nanotubes extends to the visible light region, and the intensity of surface photovoltage is enhanced after modification with CdSe QDs. The field-induced surface photovoltage spectroscopy (FISPS) shows that sodium titanate nanotubes have different photovoltaic response before and after modification. That is, the surface photovoltaic re-sponse of pure sodium titanate nanotubes increases with the enhancement of positive applied bias and decreases with the enhancement of negative applied bias. Meanwhile, the surface photovoltaic re-sponse of CdSe modified sodium titanate nanotubes is different from that of the pure sodium titanate nanotubes. The whole spectrum increases with the enhancement of applied bias at the first stage. However, when the applied bias reaches a certain value, the surface photovoltage response keeps in-creasing in some spectrum regions, while decreasing in other spectrum regions. This novel phe-nomenon is explained by using an electric field induced dipole model.
Semiconductor SnO2 nanotube arrays were fabricated by sol-gel method based on highly ordered nanoporous anodic alumina membrane. Their microstruc- tures were characterized by scanning electron microscopy, transmission electron microscopy, selective electron diffrac- tion spectroscopy and X-ray diffraction. Results indicated that SnO2 nanotubes have a thickness of about 20―30 nm, and a diameter of about 100―200 nm. The length of the nanotubes is about 1 μm, XRD and SEDS indicated that these SnO2 nanotubes are polycrystalline.
