This study investigates the mechanism of photosensitization and the recombination of excited electron-hole pairs affected by depositing platinum (Pt) on the surface of titanium dioxide (TiO 2 ). A new catalyst of Pt-TiO 2 was prepared by a photoreduction process. Being model reactions, the photocatalytic oxidation of methylene blue and methyl orange in aqueous solutions using the Pt-TiO 2 catalyst was carried out under either UV or visible light irradiation. The experimental results indicate that an optimal content of 0.75% Pt-TiO 2 achieves the best photocatalytic performance of methylene blue and methyl orange degradation and that the PtTiO 2 catalyst can be sensitized by visible light. The interaction of Pt and TiO 2 was investigated by means of UV-visible absorption spectra, photoluminescence emission spectra, and X-ray photoelectron emission spectroscopy. The Pt 0 , Pt 2+ and Pt 4+ species existing on the surface of PtTiO 2 , and the Ti 3+ species existing in its lattice may form a defect energy level. The Pt impurities, * Author whom all correspondence should be addressed to This is the Pre-Published Version.2 including Pt, Pt(OH) 2 , and PtO 2, and the defect energy level absorb visible light more efficiently in comparison with the pure TiO 2 and hinder the recombination rate of excited electron/hole pairs.

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The relationships between the catalyst physicochemical properties and its photocatalytic activity have been investigated and elucidated in the photodegradation of the organophosphate insecticide methylparathion. The photocatalytic degradation was investigated by using a sol-gel synthesized Bi 3+ -doped TiO 2 nanocatalyst (using doping concentrations up to 2 wt% Bi 3+ ) under UV-A light in aqueous suspension. The prepared photocatalysts were characterized by X-ray diffraction, (environmental) scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, IR-UV-visible absorption spectra, X-ray photoelectron emission spectroscopy and room-and low-temperature photoluminescence spectra. The photodegradation and mineralization products of methylparathion were analyzed by high performance liquid chromatography, dissolved organic carbon and ion chromatography techniques. The experiments demonstrated that the presence of Bi 3+ in TiO 2 catalysts substantially enhances the photocatalytic degradation of methylparathion in aqueous suspension.The degradation of methylparathion by these catalysts followed a first-order kinetic model and an optimal dosage between 0.7% and 1.5% Bi 3+ in TiO 2 achieved the fastest methylparathion degradation under the experimental conditions. This study has also investigated the mineralization of methylparathion in terms of carbon, sulphur and nitrogen conversion during the photocatlaytic reaction. The possible mechanisms of photoluminescence quenching and photodegradation are elucidated in the context of donor-acceptor interactions with Bi-O polyhedra acting as electron trapping centres which hinder electron-hole pair recombination. ; Endocrine disrupters; Methylparathion; Photocatalytic oxidation; Titanium dioxide; TiO 2 ; UV. IntroductionEndocrine disrupting chemicals (EDCs) have been shown to produce changes in the endocrine system of organism that may lead to increase in cancers and abnormalities in reproductive structure and function. Recent research has highlighted the existence of hormonally active compounds in sewage and industrial effluents and their potential for recycling back into the environment including drinking water supplied through point and non-point sources. On the other hand, surplus pesticides, even though within their expiration limits, will become a burden when their future use is prohibited by legislation due to toxicological or environmental concerns. The present work focuses on the preparation, characterization and application of Bi Experimental MaterialsTitanium tetra-n-butoxide (Ti(O-Bu) 4 ) and bismuth nitrate (both AR analytical grade, Aldrich Chemical Company, USA) were used as titanium and bismuth sources for the preparation of TiO 2 and Bi-TiO 2 photocatalysts. Methylparathion was obtained from the Pesticide Testing Laboratory, Tamil Nadu Agricultural University, India (AR grade) and used 4 without further purification. Deionised, doubly distilled water was used for the preparation of all solutions. Water and acetoni...

Multiporous TiO 2 /Ti film electrodes were prepared by different anodic oxidation processes at low voltage, in which the micro-structured TiO 2 thick films were prepared in H 2 SO 4 -H 2 O 2 -H 3 PO 4 -HF solution for 2 h and the nanostructured TiO 2 thin films were prepared in H 3 PO 4 -HF solution for 30 min with post-calcination. Both types of TiO 2 /Ti films were characterized by scanning electron microscopy and X-ray diffraction analysis. The photocatalytic (PC) and photoelectrocatalytic (PEC) reactivity of the TiO 2 /Ti electrodes were evaluated in terms of bisphenol A (BPA) degradation in aqueous solution. The experimental results demonstrated that the nano-structured TiO 2 /Ti thin-film electrodes had higher reactivity in the BPA degradation reaction. The PEC degradation of BPA was further studied using different cathodes, either a reticulated vitreous carbon (RVC) electrode or a platinum (Pt) electrode. The experimental results confirmed that the efficiency of BPA degradation could be significantly enhanced in the TiO 2 /Ti-RVC reaction system due to the generation of H 2 O 2 on the RVC cathode. It is believed that such a H 2 O 2 -assisted TiO 2 PEC oxidation process may have good potential for water and wastewater treatment.