Preparation, Testing and Characterization of Doped TiO₂ Active in the Peroxidation of Biomolecules under Visible Light

Abstract

Doped TiO2 samples using different preparative procedures were synthesized using either urea or thiourea leading to N- or S-doped TiO2. Photocatalytic peroxidation and oxidation (mineralization) of phosphatidylethanolamine (PE) lipid with doped TiO2 were carried out under light irradiation lambda > 410 nm. The formation of conjugated double bonds in PE molecules was followed to detect the formation of peroxy radicals (peroxidation index) under light excitation (lambda > 410 nm) when doped TiO2 was used. The kinetics of CO2 production was monitored during the mineralization of PE. Colored TiO2 powders were studied in detail by different and complementary physicochemical techniques. The band gap energies of colored TiO2 were determined by diffuse reflectance spectroscopy (DRS). The visible absorption shoulder of TiO2 was observed to follow Urbach's law. The variation of the transient decay after 354 nm laser pulse excitation does not correlate with the different N- and S-TiO2 doping levels introduced by the addition of urea or thiourea. This suggests that the states (recombination centers or traps) introduced by the doping are not effective in varying the decay kinetics within the nanosecond and microsecond time scale. Elemental analysis shows comparable amounts of S- and N-doping of TiO2 when thiourea is used as dopant. X-ray diffraction reveals no rutile in S-TiO2 samples heated to 600 degrees C, suggesting that the addition of sulfur precludes rutilization during sample crystallization. X-ray photoelectron spectroscopy (XPS) of the S-TiO2 samples confirms the preferential localization of S on the 20 topmost layers of S-TiO2 upon calcination at 500 degrees C for 2 h.

ZrNO–Ag co-sputtered surfaces leading to E. coli inactivation under actinic light: Evidence for the oligodynamic effect

“…Recently, we have reported the mechanism of the damage induced by TiO 2 photocatalysis on the bilayer cell-envelope of Escherichia coli in several studies [20][21][22][23]. Other groups working in the disinfection field have also addressed the mechanism of disinfection [24][25][26][27].…”

Insight into the catalyst/photocatalyst microstructure presenting the same composition but leading to a variance in bacterial reduction under indoor visible light

“…6, traces 3) and 4) show that higher loadings of Cu did not lead to a faster bacterial inactivation kinetics due to their higher Cu-content, but that the bacterial inactivation was essentially due to Cu-ions. Some recent reports have addressed bacterial inactivation mediated by TiO 2 doped by N and S under light [58,59]. The faster bacterial inactivation kinetics induced by the co-sputtered CuOx-TiO 2 -PET samples compared to N, S-doped TiO 2 is partly due to the effective binding of CuOx/TiO 2 with E. coli.…”

“…The pattern of the Cu and Ti sputtered on PET is complicated by the surface diffusion controlling the mass transport of Cu (II)/Cu (I) and Ti on PET [58,59]. Fig.…”

Chemical modification of TiO2 by H2PO4−/HPO42− anions using the sol-gel route with controlled precipitation and hydrolysis: enhancing thermal stability

“…These species tend to retard the phase transition of anatase to rutile and crystallite growth. Recently, phosphate/titanium dioxides have been obtained through different preparative * E-mail: K.elghniji@yahoo.fr routes entailing either surface modification of titanium oxide or hydroxide hydrate by anions, such as phosphates or sulfates [1][2][3][4][5][6][7][8] or hydrolysis of TiO 2 from corresponding titanium alkoxides in presence of phosphoric acid [9][10][11][12]. Ramadan et al [13] reported a study on titanium dioxide obtained from the hydrolysis of titanium ethoxide and phosphate by impregnation with ammonium hydrogen phosphate.…”

“…The authors argued that the bidentated phosphate groups HPO 2− 4 were persistent up to 800°C, indicating the stability of these groups within the titanium oxide structure to high temperatures. Gong [14] identified two species on the surface, namely the bridging bidentate surface complex (TiO) 2 The number of papers on phosphorus/phosphate-TiO 2 is undergoing an exponential increase. As it often occurs in case of a rapidly growing subject, a certain degree of confusion due to conflicting evidences and interpretations is present in the literature.…”