Fast synthesis and formation mechanism of γ-MnO2 hollow nanospheres for aerobic oxidation of alcohols

γ-MnO2 hollow nanospheres of about 300–800 nm in size have been synthesized by a fast 1-h 2-step process in the presence of an excess amount of Mn2+ in aqueous solution without using any templates, hydrothermal processes and catalytic routes. The evolution of morphologies evidenced that the fast formation mechanism of the γ-MnO2 hollow nanospheres in the presence of the excess amount of Mn2+ in solution followed the “Ostward ripening” process. The as-synthesized γ-MnO2 hollow nanospheres showed high catalytic activity and selectivity in aerobic oxidation of various alcohols which was attributed to their hollow nature and larger BET specific surface area.