Molecular approaches to catalysis: Naked gold nanoparticles as quasi-molecular catalysts for green processes

Gold nanoparticles smaller than ∼2 nm show interesting catalytic properties arising from their size-determined electronic and geometrical structures. They are able to dissociate molecular O2 with low activation barriers and become oxidized in a reversible way at low temperature. Several oxygen species adsorbed on the nanoparticle surface, as well as different gold sites including low coordinated neutral Au0 atoms and cationic AuI and Auδ+ species, are generated on the oxidized nanoparticles. The implication of these new sites in the mechanism of different gold-catalyzed reactions in which oxygen plays a crucial role is discussed here.