Sheetlike gold nanostructures/graphene oxide composites via a one-pot green fabrication protocol and their interesting two-stage catalytic behaviors

Abstract

Au nanoarchitectures shaped with a sheetlike morphology have drawn great attention owing to their potential applications in diverse areas of paramount importance. While great achievements have been made in the fabrication of Au nanoplates, most of the currently existing synthesis protocols generally suffer from either the requirement of rigorous reaction conditions, the involvement of specific apparatus, the use of harmful chemicals, etc. The initiation of an easy, environmentally benign yet low cost method to avoid these issues is strongly desired. In this contribution, we find that Au nanoplates could be fabricated under ambient conditions simply by mixing an aqueous solution of potassium tetrachloroaurate(III), an aqueous dispersion of graphene oxide (GO), and ethanol. Interestingly, we show that the as-manufactured Au nanoplate/GO composite displays fascinating two-stage catalytic performance towards NaBH₄-induced reduction of 4-nitrophenol (4-NP), in which the catalytic reactivity of the latter stage exhibits a substantial enhancement by a factor of ca. 9 times compared to that of the former stage. Our investigation suggests that such fascinating catalytic behaviors could be ascribed to the NaBH₄-induced restoration of the π-conjugated aromatic network of GO during the first stage, which promotes electron transfer from GO to Au nanoplates and facilitates the anchoring of 4-NPs onto the composites, resulting in the dramatically boosted catalytic performance of the second stage. This work might not only introduce a facile, green yet low-cost protocol for the synthesis of Au nanoplates but also provide deep insights into the catalytic performances of GO-based hybrid catalysts in terms of an interesting two-stage catalytic behavior.