Xishun Jiang

Microstructure, optical properties, and catalytic performance of Cu2O-modified ZnO nanorods prepared by electrodeposition

Cu2O-modified ZnO nanorods are prepared by a two-step electrodeposition method on ITO substrates, and the deposition time of Cu2O is 0, 1, 5, and 10 min, respectively. Cu2O particles are embedded in the interspaces of the ZnO nanorods, and the amounts of the Cu2O particles increase obviously when the deposition time lasts longer. The peaks corresponding to ZnO nanorods and Cu2O particles are detected from scanning electron microscope (SEM) and X-ray diffraction (XRD) results. UV-vis absorption spectra measurements have shown the bandgaps of ZnO nanorods shift from 3.22 to 2.75 eV. The methyl orange (MO) concentration can be reduced to around 15% in 100 min with Cu2O electrodeposition time for 10 min.

Capability of coupled CdSe/TiO2 heterogeneous structure for photocatalytic degradation and photoconductivity

Highly ordered TiO2 nanotube arrays (TiO2-NTAs), with a uniform tube size on titanium substrate, were obtained by means of reoxidation and annealing. A composite structure, CdSe quantum dots@TiO2 nanotube arrays (CdSe QDs@TiO2-NTAs), was fabricated by assembling CdSe quantum dots into TiO2-NTAs via cyclic voltammetry electrochemical deposition. The X-ray diffractometer (XRD), field-emission scanning electron microscope (SEM), and transmission electron microscope (TEM) were carried out for the determination of the composition and structure of the tubular layers. Optical properties were investigated by ultraviolet-visible spectrophotometer (UV-Vis). Photocurrent response under visible light illumination and photocatalytic activity of samples by degradation of methyl orange were measured. The results demonstrated that the photo absorption of the composite film shifted to the visible region, and the photocurrent intensity was greatly enhanced due to the assembly of CdSe QDs. Especially, photocurrent achieved a maximum of 1.853 μA/cm2 after five voltammetry cycles of all samples. After irradiation under ultra violet-visible light for 2 h, the degradation rate of composition to methyl orange (MO) reached 88.20%, demonstrating that the CdSe QDs@TiO2-NTAs exhibited higher photocatalytic activity.

TiO2 nanotube arrays: hydrothermal fabrication and photocatalytic activities

Titanium dioxide nanotube arrays (TiO2 NTAs) with rutile phase have been fabricated successfully via a two-step hydrothermal method. TiO2 nanorod arrays (TiO2 NRAs) are first hydrothermally grown on FTO substrate. Then the TiO2 NTAs can be obtained by controlling the HCl concentration of the hydrothermal etching process. The TiO2 NTAs have been characterized by X-ray diffractometer, scanning electron microscope, transmission electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet–visible spectroscope. Evolution of TiO2 nanoarrays are accompanied by enhanced of the surface area and optical properties. Compared with TiO2 NRAs, the prepared TiO2 NTAs is more efficient in the photodegradation of methyl orange. These results reveal that the hydrothermal chemical etching provide a flexible and straightforward route for design and preparation of TiO2 NTAs, promising for new opportunities in photocatalysts and other fields.

Enhanced photoelectrochemical properties of nanocrystalline TiO 2 electrode by surface sensitization with Cu x O quantum dots

Nanoporous anatase TiO2 films were fabricated by a screen-printing method, and CuxO quantum dots (QDs) were deposited on the TiO2 films through successive ionic layer adsorption and reaction (SILAR). The amount of CuxO QDs on the TiO2 films are controlled by changing the number of SILAR cycles. The morphology, microstructure, optical, and photoelectrochemical properties of different CuxO sensitized TiO2 films (CuxO/TiO2) were investigated in detail. The nanoporous TiO2 film offers a large surface area for anchoring QDs. QD deposited samples exhibited a significant improvement in photoelectrochemical performance than the bare of TiO2. CuxO/TiO2, prepared with 7 SILAR cycles, showed the best photoelectrochemical properties, where the photocurrent density was enhanced to 500.01 μA/cm2 compared with 168.88 μA/cm2 of bare TiO2 under visible light. These results indicate that the designed CuxO/TiO2 structure possesses superior charge separation efficiency and photoelectrochemical properties.

Influence of Ag volume fraction on microstructure and optical constants of Ag-WO3 thin films

The WO3 film and Ag-WO3 nanocomposite films with Ag volume fractions (3.0, 6.0, and 12.0 vol. %) were deposited on Si substrates by radio-frequency cosputtering. X-ray diffractometer analyses show that the microstructure of WO3 films transforms from the tetragonal phase to monoclinic phase when the metal Ag was embedded into the WO3 matrix. Scanning electron microscope images demonstrate that the density of particles on Ag-WO3 films surface increases as the Ag volume fraction increases. X-ray photoelectron spectroscopic measurements display that Ag is in the form of Ag atom clusters in the film. Optical constants confirmed by ellipsometric spectroscopy indicate that the value of refractive index decreases from 2.1 to 1.1 at 300 nm with the increase in Ag content. The extinction coefficient increases with the increase in Ag content.

EFFECT OF MOLYBDENUM DOPING AND ANNEALING ON PHOTOLUMINESCENCE OF SPUTTERING-DERIVED ZINC OXIDE FILMS

The molybdenum-doped ZnO (MZO) films were deposited on quartz substrates by radio frequency magnetron sputtering. All films have a polycrystalline hexagonal wurtzite structure. Mo doping influences the grain size of the MZO films and leads to a compressive stress in the films. The valence of Mo in the MZO films is hexavalence. Mo doping enhances the emissions at 380 and 412 nm. Annealing significantly influences the photoluminescence (PL) spectra of the MZO films. The PL spectral intensity of the annealed films is much higher than that of the unannealed films. The emissions at 400 and 525 nm enhanced dramatically with the rising of annealing temperature while the emissions at 380 and 412 nm became weak or disappeared. Mo doping is beneficial for the enhancement of the emissions at 400 and 525 nm of the annealed MZO films. The origins of these emissions were discussed in detail.