Quantum Efficiency of Hydroxyl Radical Formation in a Composite Containing Nanocrystalline TiO2 e Zinc Phthalocyanine, and the Nature of the Incident Radiation

Abstract

In this study, we investigate the generation of hydroxyl radicals mediated by a composite containing TiO 2 and 1.6% m/m of zinc phthalocyanine (TiO 2 /ZnPc) in aqueous suspensions containing methanol as oxidisable substrate. The composite features a specific surface 20% less than the value estimated for TiO 2 P25, probably due to the covering of the surface of the oxide by ZnPc and the pH of the isoelectric point of this composite equal of 5.5, about two units of pH lower than the value estimated for TiO 2 P25, are probably related to the difference in photocatalytic activity found for these materials. To assess the influence of different spectral bands of electromagnetic radiation on the production of hydroxyl radicals, we used different sources of radiation in experiments conducted to estimate the quantum efficiency of hydroxyl radical formation (HO•), via photocatalytic oxidation of methanol. The association between zinc phthalocyanine and TiO 2 has allowed the formation of a light absorber material with absorption spectral range extended to the visible region. Our results suggest that, despite the higher values of  HO• for TiO 2 P25, the combination of visible and ultraviolet radiation furnished by a high pressure mercury lamp without the protective bulb, or solar radiation, causes the composite to present good values for the same parameter.

Zn(II)-tetracarboxy-phthalocyanine-Sensitized TiO2 Thin Films as Antimicrobial Agents under Visible Irradiation: a Combined DFT and Experimental Study

“…The dye anchored on the TiO 2 surface (TcPcZn–TiO 2 films) has a band gap value of 1.58 eV. As observed, after the sensitizing process, the optical properties of TcPcZn–TiO 2 films in the visible region improved significantly, which also suggests that after the sensitizing process this type of film could work as a catalyst under visible irradiation …”

“…As observed, after the sensitizing process, the optical properties of TcPcZn−TiO 2 films in the visible region improved significantly, which also suggests that after the sensitizing process this type of film could work as a catalyst under visible irradiation. 77 2.5. Antimicrobial Activity against MRSA.…”

Produção fotocatalítica de hidrogênio utilizando catalisadores baseados no dióxido de titânio

“…Afim de contornar esta limitação, podem ser introduzidas modificações na estrutura cristalina do TiO2 capazes de ampliar a sensibilidade deslocando a absorção para o VIS. Dentre estas modificações podem ser citadas a dopagem (Zhang et al, 2011;Bloh et al, 2013;Pattanaik e Sahoo, 2014) e/ou associação com fotossensitizadores (Machado et al, 2008b;Kim et al, 2011;Batista et al, 2013).…”

“…Batista e colaboradores reportaram uma Eg igual a 2,7 eV para compósitos contendo diferentes percentagens em massa de ftalocianina de zinco, e uma banda de absorção acentuada a partir de 460 nm, estendendo-se para o infravermelho próximo, e com uma absorção intensa a 683 nm, relacionada a um deslocamento para o vermelho da banda Q da FtZn (Batista et al, 2013).…”

“…de FtZn e os óxidos TiO2 P25, M02 e M19, tiveram, para comparação, o pH ajustado para 6,2, pHpcz do P25 (Hoffmann et al, 1995), já que, dentre os compósitos estudados, o pHpcz só foi estimado, até o momento, para o P25/FtZn (Batista et al, 2013), que apresenta um valor igual a 5,5. Um estudo do efeito do pH sobre a evolução de H2, bem como a determinação do pHpcz para estes outros compósitos, faz-se, portanto, necessário, de modo que os parâmetros de evolução de H2 para esses compósitos sejam otimizados.…”