gamma-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 gamma-MnO2 hollow nanospheres in the presence of the excess amount of Mn2+ in solution followed the "Ostward ripening" process. The as-synthesized gamma-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. (C) 2010 Elsevier Ltd. All rights reserved.