Facile Aqueous-Phase Synthesis of an Ultrasmall Bismuth Nanocatalyst for the Reduction of 4-Nitrophenol.

Bismuth metallic nanoparticles have evoked considerable interest in catalysis owing to their small size, high surface area-to-volume ratio, and low toxicity. However, the need for toxic reductants and organic solvents in their synthesis often limits their desirability for application development. Here, we describe a green strategy to synthesize bismuth nanodots via the redox reactions between bismuth nitrate and d-glucose, in the presence of poly(vinylpyrrolidone) in the basic aqueous phase. Both reagents play a crucial role in the formation of monodisperse bismuth nanodots acting as mild reducing and capping agents, respectively. We further demonstrate that the catalytic activity of these dots via the successful reduction of the environmental contaminant 4-nitrophenol to its useful 4-aminophenol analogue requiring only 36 μg/mL nanocatalyst for 20 mM of the substrate. Moreover, they can be recovered and recycled in multiple reactions before the onset of an appreciable loss of catalytic activity. The proposed facile synthetic route and inexpensive matrix materials lead the way to access bismuth nanodots for both the fundamental study of reactions and their industrial catalysis applications.