Photodegradation of Indigo Carmine dye by CdS nanostructures under blue-light irradiation emitted by LEDs

Abstract

Two nanostructured CdS semiconductors were prepared by the precipitation method under ethylenediamine mild synthesis conditions. The ethylenediamine–acetonitrile solvent mixture induces the formation of CdS-1D-flexible nanofibers, whereas the ethylenediamine–ammonia solvent produces 3D-microflower morphology. Similar crystalline structure and optical–electronic properties were obtained by using both solvents; however, the photocatalytic activity strongly depends on both the CdS morphology and textural properties. In comparison with the commercial CdS, the flexible CdS nanofibers showed the highest photocatalytic activity in the photodegradation of Indigo Carmine (IC) dye by using pure blue light irradiation. The effect of the stirring rate, photocatalyst load and IC dye concentration was investigated under either the diffusive or kinetic controlled regime of the photoreaction. The influence of the pH solution and stability cycle on the nanofibers was also evaluated. The blue photoreduction of IC dye was also investigated in the presence of hydrazine as O2 scavenger. The possible oxidation or reduction mechanisms of the IC dye by the photogeneration of either the superoxide or hydrazil radicals on the surface of the CdS nanofibers are presented and discussed.