Metal-free catalysis for efficient reduction of 4-nitrophenol by graphene quantum dots controlled by the surface trapped water molecules

Abstract

We report the synthesis of environment-friendly and water-soluble metal-free functional carbon materials, graphene quantum dots (GQDs), applied as catalysts for efficient reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in aqueous solution at room temperature and ambient condition. The one-pot and easily synthesized GQDs show excellent variation in catalytic property in reducing 4-NP. While the unprotected GQDs demonstrate relatively slow conversion of 4-NP to 4-AP, the protein-protected and thiolate-coated GQDs show enhancement in the reduction rate by two orders of magnitude. The heterogeneous catalytic activity by the three variants of GQDs appears to depend on the extent of core surface-trapped water molecules.