Catalytic activity of unsupported gold nanoparticles

This article reviews some of the compelling evidence showing that colloidal gold nanoparticles without any solid support exhibit intrinsic catalytic activity for some of the typical gold-catalyzed reactions including CO oxidation, aerobic oxidation of alcohols and diols, borohydride reductions and carbon–carbon cross coupling reaction among other reactions. A critical view of the state-of-the-art indicating open issues such as the role of the nature and concentration of the ligand and the possibility of preparing colloidal samples with preferential crystallographic planes is provided.