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- An improvement of photocatalytic activity of TiO2 Degussa P25 powderPublication . Bessergenev, V.; Mateus, M. C.; Botelho do Rego, A. M.; Hantusch, M.; Burkel, E.The photocatalytic activities of Degussa P25 powders annealed at various temperatures in vacuum and air were studied together with investigations of their compositions by XPS, of their crystal structures by XRD and of their specific surface areas by BET. It is shown that the photocatalytic activity of P25 powders was remarkably enhanced after vacuum annealing; the kinetic coefficient can be raised by 75% during annealing at 400 degrees C. It is obvious that this enhancement is not related to the adhesion ability of the P25 powders. (C) 2015 Elsevier B.V. All rights reserved.
- TiO2:(Fe, S) Thin Films Prepared from Complex Precursors by CVD, Physical Chemical Properties, and PhotocatalysisPublication . Bessergenev, V.; Mateus, Maria da Conceição; Vasconcelos, D. A.; Mariano, José; do Rego, A. M. Botelho; Lange, R.; Burkel, E.The TiO2 thin films were prepared using Ti(dpm)(2)(OPri)(2) and Ti(OPri)(4) (dpm = 2,2,6,6-tetramethylheptane-3,5-dione, Pr-i = isopropyl) as the precursors. The volatile compounds Fe[(C2H5)(2)NCS2](3) and [(CH3)C](2)S-2 were used to prepare doped TiO2 films. The synthesis was done in vacuum or in the presence of Ar and O-2. The pressure in the CVD chamber was varied between 1.2 x 10(-4) mbar and 0.1 mbar, with the system working either in the molecular beam or gas flow regime. Physical, chemical, and photocatalytic properties of the (Fe, S)-doped TiO2 films were studied. Those TiO2:(Fe, S) films prepared from the Ti(OPri)(4) precursor show increased photocatalytic activities, very close to those of Degussa P25 powder in UV region.
- Electrical properties of thin-films wide-band gap semiconductor TiO(2) prepared by CVDPublication . Bessergenev, V.; Gomes, Henrique L.High dielectric constant TiO2 thin films are promising for gate insulator in 100-nm microelectronic technology. In this study rutile and anatase phase TiO2 thin films were prepared by Chemical Vapour Deposition (CVD) method. Bulk and surface chemical composition of thin films were characterized by high-resolution Laser Ionization Mass Spectrometry (LIMS) and by X-ray Photoemission Spectroscopy (XPS). Crystal structure was studied by (XRD). Silicon based Metal-Insulator semiconductor (MIS) capacitors formed on the high-k dielectric TiO2 were fabricated and characterized using small signal impedance studies as function of frequency and current vs voltage measurements. As it was shown from I–V characteristics, the Shockley equation adequately describes the conductivity mechanism in low field region. By analysis of I–V characteristics it was also found that there is change in carrier conduction mechanism from Shockley regime to the nonlinear Frenkel–Poole mechanism.
- Photocatalytic reactor, CVD technology of its preparation and water purification from pharmaceutical drugs and agricultural pesticidesPublication . Bessergenev, V.; Mateus, Maria da Conceição; Morgado, I. M.; Hantusch, M.; Burkel, E.A tubular photocatalytic reactor of the immersion type for water purification from organic pollutants has been developed. Few important principles were used in the construction of the reactor, namely, a symmetrical and uniform light distribution with direct incidence of UV irradiation on the photocatalyst surface, a highly active mixing of contaminated water as a result of an air bubbling flux, that simultaneously supplying oxygen that is necessary for a photocatalytic reaction. The implemented highly active thin film photocatalyst was prepared by the Chemical Vapor Deposition (CVD) technology using titanium(isopropoxide) (TTIP) as a precursor. The factor K = Surface/Volume of this reactor is about 255 m(-1). Together with an effective mixing, it creates excellent contacts between the contaminants and the photocatalyst which is very favorable for water purification. The efficiency of this reactor was proven by the decomposition of some pharmaceutical drugs (Ibuprofen, Acetylsalicylic acid, Sulphanilamide, Paracetamol, Caffeine) and of some pesticides (Dimethoate, Azoxystrobin, Iprodione, Propizamid, Isoproturon, Fenarimol). The relation between the kinetic constants of photocatalysis and of photolysis is K-photcat/K-photolysis = 2 divided by 18. These results demonstrate the feasibility of the developed photoreactor for the degradation of recalcitrant organic pollutants, such as pharmaceuticals and pesticides in water. (C) 2016 Elsevier B.V. All rights reserved.