Estudo da fotodegradação no visível do corante Reactive Black 5 por catalisadores plasmônicos híbridos Ag∕ZnO e Cu∕ZnO

Abstract

The present work consisted in the synthesis and characterization of plasmonic nanostructured hybrids metal∕semiconductor catalysts, for application on photodegradation of the Reactive Black 5 (RB5) textile dye using visible irradiation. Nanoparticles consisting of zinc oxide, copper (CuNPs) and silver (AgNPs) were synthesized, as well as plasmonics catalysts of Cu∕ZnO and Ag∕ZnO types. The materials underwent several characterizations using techniques such as Raman Spectroscopy, UV-VIS, polycrystal DRX, SEM and TEM. Photodegradation processes were carried out in a labmade reactor, in which a dye solution (1×10-5mol L-1) was irradiated using fluorescent (11W) and∕or glowing (100W) lamp bulb as sources of radiation in the visible range. The photodegradation of the RB5 dye was monitored through electronic spectroscopy UV-VIS, and vibrational spectroscopies resonant Raman (RR) and surface enhanced Raman spectroscopy (SERS). UV-VIS allowed observing changes related to the photodegradation process, as a drop in intensity of the absorption band of the chromophoric group. RR and SERS techniques results presented the formation of fluorescent species and changes in the vibrational spectral profile. The photolysis of the dye didn’t occur under any of the sources of irradiation used. AgNPs didn’t promote the photodegradation of the RB5, but nanoparticles of ZnO degraded about 66% of the dye molecules, under the visible radiation (incandescent lamp). Plasmonics photocatalysts Ag∕ZnO were used in the processes of degradation of the RB5 using both sources of irradiation in the visible range, but it was added to the dye solution in different ways. When used directly in suspension and under fluorescent lamp irradiation the photodegradation percentage was 97%. With the addition of the catalyst in the solid state to the dye solution and under fluorescent lamp irradiation 72% of the RB5 molecules were degraded. This last result can be compared to that achieved using ZnO as catalyst and shows a 22% gain in catalytic efficiency under visible light in the presence of the plasmonic material AgNP/ZnO.