Undoped TiO2 Nanoparticles Research Articles

Enhanced photocatalytic activity for titanium dioxide by co-modification with copper and iron

A copper(II) and iron(III) co-modified titanium dioxide nano material was prepared by a simple sol–gel process using titanium(IV) isopropoxide plus copper(II) and iron(III) nitrates as raw materials. The as-prepared nanocomposites were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy and photoluminescence spectra. The XRD results showed that the undoped TiO2 nanoparticles mainly include anatase phase while the Cu, Fe-codoped TiO2 nanoparticles showed a mixture of anatase phase with a small fraction of rutile phase displaying higher activity than the pure anatase phase. Optical characterization showed that the codoping with copper(II) and iron(III) resulted in a red shift of adsorption and lower recombination probability between electrons and holes, which were associated with high photocatalytic activity of the Cu, Fe-codoped TiO2 nanoparticles under visible light (λ > 400 nm). The photocatalytic activity of the samples was tested by aqueous methyl orange degradation. The capability of the codoped catalyst was much higher than that of the pure TiO2 catalyst under visible irradiation. A mechanism is proposed in order to account for the enhanced catalytic activity.

Improved surface‐enhanced Raman scattering properties of TiO2 nanoparticles by Zn dopant

AbstractIn this paper, pure and Zn‐doped TiO2 nanoparticles (NPs) with various content of Zn were prepared by a sol–hydrothermal method and were employed as active substrates for surface‐enhanced Raman scattering (SERS). On the 3% Zn‐doped TiO2 substrate, 4‐mercaptobenzoic acid(4‐MBA) molecules exhibit a higher SERS intensity by a factor of 6, as compared with the native enhancement of 4‐MBA adsorbed on undoped TiO2 NPs. Moreover, the higher SERS activity was still observed on the 3% Zn‐doped TiO2 NPs at temperature even up to 125 °C. These results indicate that an appropriate amount of Zn doping can improve the SERS performances of TiO2 SERS‐active substrates. The introduction of Zn dopant can enrich the surface states (defects) of TiO2 and improve the separation efficiency of photo‐generated charge carriers (electrons and holes) in TiO2, according to measurements of X‐ray diffraction, UV‐visible diffuse reflectance spectroscopy, and photoluminescence, which are responsible for the influence of Zn dopant on the improved SERS performances of TiO2 NPs. Copyright © 2009 John Wiley & Sons, Ltd.

Preparation of Fe3+-doped TiO2 nanoparticles and its photocatalytic activity under UV light

The Fe3+-doped and undoped TiO2 nanoparticles have been prepared by sol–gel route using ferric nitrate aqueous solution and tetrabutyl titanate. The nanoparticles were characterized by XRD, SEM, EDX and UV–vis DRS techniques. The results showed that the Fe3+-doped TiO2 possess the anatase structures, which were composed of 8–11 nm of crystal sizes. The photocatalytic activity of the nanoparticles under UV light was investigated by measuring the photodegradation of phenol in aqueous dispersion. The 0.5 mol% Fe doping exhibited enhanced photocatalytic activity in this study. An attempt has been made to correlate the degradation of phenol with partition coefficient of phenol in sodium dodecyl sulfate micelles and water as a function of irradiation time.

Structure and size distribution of TiO2 nanoparticles deposited on stainless steel mesh

Doped and undoped TiO2 nanoparticles with narrow size distribution were deposited on stainless steel mesh substrates by metalorganic chemical vapor deposition. The chemical composition of TiO2 nanoparticles was measured by energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy. X-ray diffraction and transmission electron microscopy were performed to investigate the size and the size distribution of particles as well as the structural phase transitions. For pure TiO2, the results showed that anatase polycrystalline nanoparticles with average size from 23 to 31 nm were obtained for substrate temperatures between 350 and 600 °C. Particles deposited below 350 °C were x-ray amorphous and rutile began to precipitate at temperatures above 700 °C. The particles synthesized at 600 °C had the smallest size and narrowest size distribution. In order to study the dopant effects on the photocatalytic properties, growth temperature of 600 °C was selected to prepare 1 at. % Nd3+ doped TiO2 nanoparticles. The results of photodegradation of the pollutant 2-chlorophenol solution irradiated under ultraviolet light showed that 1 at. % of Nd3+ doped TiO2 had an enhanced degradation of the pollutant. The enhancement of photocatalytic efficiency by doped nanoparticles was ascribed to the large surface area and trapping induced prolonged lifetime of holes.