Organized and highly dispersed growth of MnO2 nano-rods by sonochemical hydrolysis of Mn(3)acetate

Highly dispersed and non-agglomerated alpha-MnO2 nano-needles of dimensions 20-30 nm have been synthesized by the application of ultrasound radiation on the aqueous solution consisting of manganese(3) acetate close to neutral pH followed by mild drying. With a similar reaction system, hot hydrolysis (non-sonochemical process) produced beta-MnO2 nano-rods of length 100-200 nm but with high degree agglomeration. Sonochemical cavitation phenomenon is suggested to have a pronounced effect for the formation of special phase and morphology. The effect is proved by the difference in the intermediate products which has difference in crystalinity and phase-purity. The intermediate phases are identified to be single-phase gamma-MnOOH for the non-sonochemical reaction and mixture of gamma-MnOOH, alpha-MnO2 and beta-MnO2 for the sonochemical products. (C) 2005 Elsevier B.V. All rights reserved.