Enhanced photocatalytic activity in the reverse type-I QD through the shell-oriented cascadal charge transfer

Abstract

Here, we demonstrate an inverse gradient flow of the potential energy at the core/shell interface in ZnS@CdS QD offering higher solar conversion efficiency. The developed band lineup extracts the photogenerated charges into the nanohybrid surface (shell) via a cascadal way along the gradient and hence rises the charge migration quantum efficiency, which leads to the superior photocatalytic efficiency for photoredox reactions over the hybrid photocatalyst. In order to confirm bandgap engineering and exciton delocalization, we exploited steady-state and time-dependent emission and absorption methodologies in the presence and absence of electron/hole quenchers. The suppression of emission intensities together with the decline of the lifetimes verified the crucial role of shell on the migration of energetic electron/hole pairs from the core to the catalyst surface. Besides, surveys of the photocatalytic properties of the as-prepared photocatalysts and kinetic investigation of the reactions were accomplished under solar light irradiation, without using sacrificial agents. The role of reactive oxygen species to photocatalysis reactions revealed via the luminol luminescence and photoluminescence of terephthalic acid. Probable mechanisms of decomposition of organic dyes including direct photo-reduction and/or -oxidation, reactive oxygen or free radicals species creation and the photosensitization degradation pathways, based on inverse ZnS@CdS type-I QDs were discussed, too.