Du Zuliang

Raman Investigation of Sodium Titanate Nanotubes under Hydrostatic Pressures up to 26.9 GPa

High pressure behavior of sodium titanate nanotubes (Na2Ti2O5) is investigated by Raman spectroscopy in a diamond anvil cell (DAC) at room temperature. The two pressure-induced irreversible phase transitions are observed under the given pressure. One occurs at about 4.2 GPa accompanied with a new Raman peak emerging at 834 cm−1 which results from the lattice distortion of the Ti-O network in titanate nanotubes. It can be can be assigned to Ti-O lattice vibrations within lepidocrocite-type (H0.7Ti1.825V0.175O 4H2O)TiO6 octahedral host layers with V being vacancy. The structure of the nanotubes transforms to orthorhombic lepidocrocite structure. Another amorphous phase transition occurs at 16.7 GPa. This phase transition is induced by the collapse of titanate nanotubes. All the Raman bands shift toward higher wavenumbers with a pressure dependence ranging from 1.58–5.6 cm−1/GPa.

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.

Investigation of tribological properties of composite C60-LB films

Composite C60-LB films were fabricated by the Langmuir-Blodgett (LB) technique, their micro-structures, micro-and macro-tribological properties were investigated using atomic force microscope/friction force microscope (AFM/FFM). The results showed that in the confined C60-LB films there were two kinds of structures for the special C60 assembly: grain diameters of one kind were in the range of 150–230 nm; the other was smaller than 20 nm. Micro-tribological studies showed that topographical images of tiny C60 aggregates (<20 nm) were consistent with their frictional ones very well, namely, low friction occurred on tiny C60 aggregates compared with fatty chains LB monolayer, and ‘Micro-rolling effect’ was apparent; but for big large ones frictional forces were relatively high and ‘ratchet mechanism’ was seen apparently. Macro-tribological data proved large C60 aggregates had wear resistance and load-carrying capacities and anti-wear lives for composite C60-LB films were prolonged greatly with dispersibility of C60 improved and its grain diameter reduced. Tiny C60 aggregates were mainly the lubricating agents. Friction coefficients of composite C60-LB films gradually reduced with loads increasing having the same friction coefficient-load relations with boundary lubrication films.

Influence of pH Value in Electrolyte on Photovoltaic Performance of CIGS Thin-films Prepared by Electrochemical Method: Influence of pH Value in Electrolyte on Photovoltaic Performance of CIGS Thin-films Prepared by Electrochemical Method

Cu(In1-x,Ga-x)Se-2 (CIGS) films were prepared by one-step electrodeposition method on FTO glass substrates, and the influence of electrolytic pH on the chemical composition, structure and photovoltaic performance of CIGS thin-films were studied in detail. The results showed that the stoichiometry of In and Ga in the film could be effectively regulated by changing the pH value of the electrolyte. The X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) results showed that the CIGS thin-films had good crystallinity and uniform particle size distribution when the pH value was 2.0. The effect of different stoichiometries of the CIGS thin-films on the kinetics of photo-charges was also studied. The CIGS thin film with a stoichiometric ratio of 0.3 for Ga/(In + Ga) presented the strongest surface photovoltaic effect.

Synthesis and gas-sensing properties of CuO nanowires array film by magnetron sputtering method

The thin copper films were deposited by magnet sputtering on fluorine-doped tin oxide (FTO) coated glass. The CuO nanowires array film can be obtained through the heat oxidation process. The morphology and microstructure of the copper film and the CuO nanowires film was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), respectively. The CO and H 2 S sensing characteristics of the CuO nanowires array film were also investigated. The results show that CuO nanowires array film exhibited highest response to CO gas at 250°C. The response was significantly enhanced when the CO gas concentration was increased. There is a sensing response at low gas concentration for H 2 S at room temperature. While for the higher temperature, the resistance of the CuO nanowires array film decreased rapidly, which is different from the CO gas. The abnormal resistance change for the H 2 S was also illustrated in this article.