Graphene Quantum Dots Drive Spontaneous Metal Reduction to form Stable and Electroactive Core-Shell Nanocolloids

This work demonstrates a spontaneous synthesis of ∼8.0, ∼7.0, and ∼3.0 nm diameter Au, Ag, and Pt cores; respectively, wrapped by as-synthesized crystalline graphene-quantum dots (GQDs). Functional sp²- and sp³-hybridized carbons play a crucial role upon the synthesis, electronic distribution at the interface, and conductive sites for improving the electrocatalytic response. Au nanohybrids (NHs) demonstrated two-fold increase in current density with respect to conventional citrate-coated Au nanoparticles. This was attributed to conductive sp²- hybridized carbons and the gain of charge density at the surface of Au as demonstrated by DFT calculations. Due to the sp³-carbons at the shell, these NHs also behave like simple chemical compounds because they can be precipitated, stored for long periods of time, and redispersed without apparent changes in their properties. The resultant nanocolloids exhibit exceptional stability under harsh conditions. These attributes make them useful NHs with great potential for broad applications.