Highly Efficient Visible-Light-Induced Photocatalytic Activity of Fe-Doped TiO2 Nanoparticles

Bare TiO2 and nominal 5.0 at% Fe-doped TiO2 nanoparticles were synthesized by the modified sol-gel method. The samples were physically characterized in order to obtain the correlation between structure and photocatalytic properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer, Emmett and Teller (BET), and UV-vis diffuse reflectance spectrophotometry (UV-vis DRS). XRD results indicated that phase structures of bare TiO2 and Fe-doped TiO2 nanoparticles were the mixture of anatase and rutile phases. The content of rutile phase in 5.0 at% Fe-doped TiO2 nanoparticles decreased . TEM images revealed that the shape of bare and 5.0 at% Fe-doped TiO2 was almost spherical and the average particle size was in the range of 10-30 nm. Specific surface areas of the samples were found as 75 and 134 m2/g for bare TiO2 and nominal 5.0 at% Fe-doped TiO2, respectively. The results from UV-vis reflectance spectra clearly indicated the shift of absorption band edge towards visible region upon doping TiO2 with iron. Photocatalytic activity of bare TiO2 and 5.0 at% Fe-doped TiO2 nanoparticles was examined by studying the mineralization of oxalic acid under visible light irradiation and the results clearly showed that Fe-doped TiO2 sample exhibited higher activity than bare TiO2

Synthesis and Characterization of the Novel BiVO4/CeO2 Nanocomposites

Novel BiVO4/CeO2 nanocomposites were synthesized by the hydrothermal method combined with the homogeneous precipitation method. The mole ratios of BiVO4:CeO2 were 0.4:0.6, 0.5:0.5, and 0.6:0.4. The obtained BiVO4/CeO2 nanocomposites were characterized by X-ray diffraction (XRD) for phase composition and crystallinity. Particle sizes, morphology and elemental composition of BiVO4/CeO2 composites were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The Brunauer, Emmett and Teller (BET) adsorption-desorption of nitrogen gas for specific surface area determination at the temperature of liquid nitrogen was performed on all samples. UV-vis diffuse reflectance spectra (UV-vis DRS) were used to identify the absorption range and band gap energy of the composite catalysts. The results indicated that BiVO4/CeO2 samples retained monoclinic scheelite and fluorite structures. The morphologies of nanocomposite samples consisted of rod-like, plate-like and spheroidal shapes. Specific surface area (SSABET) of the novel synthesized catalysts drastically increased from 38 - 150 m2/g whereas an average BET-equivalent particle diameter (dBET) significantly decreased from 30 - 12 nm, upon increasing the amount of CeO2 in the BiVO4/CeO2 composite. The absorption spectra of all nanocomposite samples were shifted to the visible region, suggesting the potential application of this novel composite as an active visible-light driven photocatalyst

Flame-Made Nb-Doped TiO2 Ethanol and Acetone Sensors

Undoped TiO2 and TiO2 nanoparticles doped with 1–5 at.% Nb were successfully produced in a single step by flame spray pyrolysis (FSP). The phase and crystallite size were analyzed by XRD. The BET surface area (SSABET) of the nanoparticles was measured by nitrogen adsorption. The trend of SSABET on the doping samples increased and the BET equivalent particle diameter (dBET) (rutile) increased with the higher Nb-doping concentrations while dBET (anatase) remained the same. The morphology and accurate size of the primary particles were further investigated by high-resolution transmission electron microscopy (HRTEM). The crystallite sizes of undoped and Nb-doped TiO2 spherical were in the range of 10–20 nm. The sensing films were prepared by spin coating technique. The mixing sample was spin-coated onto the Al2O3 substrates interdigitated with Au electrodes. The gas sensing of acetone (25–400 ppm) was studied at operating temperatures ranging from 300–400 °C in dry air, while the gas sensing of ethanol (50–1,000 ppm) was studied at operating temperatures ranging from 250–400 °C in dry air