Jinbo Xue

The study on properties of CdS photocatalyst with different ratios of zinc-blende and wurtzite structure

The mixtures of zinc blende and wurtzite CdS nanoparticles were prepared via a solvothermal method by controlling the precursor ratio (Cd/S molar ratio). The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and ultraviolet-visible (UV-vis) spectroscopy. These results demonstrate that not only the morphology but also the phase composition of CdS nanostructures was sensitively altered by the precursor ratio (Cd/S molar ratio). Photocatalysis test results show that the photocatalytic activity was mainly dependent on the ratio between zinc blende and wurtzite phases in CdS samples. The product prepared with 1:2 Cd/S molar ratio exhibited higher photocatalytic activities in comparison with products prepared with other Cd/S molar ratios, which can be attributed to the improved charge separation at the zinc blende/wurtzite junction interface.

Shape-controlled synthesis of three-dimensional branched CdS nanostructure arrays: structural characteristics and formation mechanism

Through a combination of electrodeposition and subsequent solvothermal reaction, three-dimensional (3D) branched CdS nanostructure arrays were fabricated by nanowires self-assembly in ethanediamine solution containing thiourea and hexamethylenetetramine (HMTA) for the first time, where HMTA acted as a capping agent. In the absence of HMTA, only disordered CdS nanowires were obtained. The reaction conditions influencing the synthesis of 3D branched CdS nanostructure arrays, such as the concentration of HMTA and thiourea, reaction temperature and reaction time, were studied and optimized. The 3D branched CdS nanostructure arrays were characterized by X-ray diffraction, field emitting scanning electron microscopy and transmission electron microscopy. The results show that HMTA played an important role in the formation of 3D branched CdS nanostructure arrays. A growth process of HMTA-assisted gradual crystallization and subsequent oriented attachment was proposed as a plausible mechanistic interpretation for the formation of the 3D branched nanostructure arrays. In addition, the photoluminescence property of the novel 3D branched CdS nanostructure arrays was investigated.

Enhanced visible-light absorption in heavily nitrogen-doped TiO2

Heavy nitrogen doping of TiO2 thin films has been achieved by ion-beam-assisted deposition. The heavily doped films have a distorted anatase crystal structure and show an increase in visible-light absorption compared to films with only light nitrogen doping. The enhanced absorption is shown by a first-principles density-functional calculation to result from an electronic band-gap narrowing, in contrast to the appearance of isolated N 2p states above the valence-band maximum that occur with light nitrogen doping.

Electrochemical preparation and photoelectric properties of Cu2O-loaded TiO2 nanotube arrays

TiO2 nanotube (TNT) arrays were fabricated by anodic oxidation of titanium foil in a fluoridebased solution, on which Cu2O particles were loaded via galvanostatic pulse electrodeposition in cupric acetate solutions in the absence of any other additives. The structure and optical properties of Cu2O-loaded TiO2 nanotube arrays (Cu2O-TNTs) were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Vis absorption, and the photoelectrochemical performance was measured using an electrochemical work station with a three-electrode configuration. The results show that the Cu2O particles distribute uniformly on the highly ordered anatase TiO2 nanotube arrays. The morphologies of Cu2O crystals change from branched, truncated octahedrons to dispersive single octahedrons with increasing deposition current densities. The Cu2OTNTs exhibited remarkable visible light responses with obvious visible light absorption and greatly enhanced visible light photoelectrochemical performance. The I–V characteristics under visible light irradiation show a distinct plateau in the region between approximately −0.3 and 0 V, resulting in higher open-circuit voltages and larger short-circuit currents with increased Cu2O deposition.

Effects of annealing temperature on the properties of copper films prepared by magnetron sputtering

Copper oxide thin films were prepared by a direct-current magnetron sputtering method followed by a thermal annealing treatment at 100–500 °C. The obtained films were characterized by X-ray diffraction, UV-vis absorption spectroscopy, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. With the increase of the annealing temperature, it was found that the films transformed sequentially from amorphous to single-phase Cu (100 °C), mixed-phase of Cu and Cu2O (150 °C), single-phase Cu2O (200 °C), then to mixed-phase of Cu2O and CuO (300 °C), and finally to single-phase CuO (400–500 °C). Further analyses indicated that the Cu/Cu2O thin films and the Cu2O thin films presented no further oxidation even on the surface in air atmosphere. Additionally, the visible-light photocatalytic behavior of the copper oxide thin films on the degradation of methylene blue (MB) was also investigated, indicating that the films with pure Cu2O phase or Cu/Cu2O mixed phases have excellent photocatalytic efficiencies.

The surface wettability of TiO2 nanotube arrays: which is more important—morphology or chemical composition?

The wettability of TiO2 nanotube arrays (TiO2-NTAs) synthesized by electrochemical anodization was intensively investigated. It was found that annealing temperature of TiO2-NTAs has significant effect on the hydrophilicity of TiO2-NTAs. With the increase of annealing temperature, the fluorine element content on TiO2-NTAs surface decreases, which results in decrease in water contact angle and increase in hydrophilicity for TiO2-NTAs. The reason is that F− ions escape from the lattice and oxygen vacancies are created at the two coordinated oxygen bridging sites at TiO2-NTAs surface after annealing in argon atmosphere. And these defects can in turn increase the affinity for hydroxyl ions formed by dissociation of chemisorbed water molecules and thereby form hydrophilic domains. In addition, TiO2 crystal becomes well organized gradually with the increase of annealing temperature, F− ions are not favored to exist in the lattice and thus escape from the lattice. Less F element content results in better hydrophilicity of TiO2-NTAs.