a1 State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200030, People’s Republic of China
a2 Spintronic and Electronic Materials Group, Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2522, Australia
a3 Coll. Chem. & Chem. Eng., State Key Lab Met Matrix Composites, Shanghai Jiao Tong University, Shanghai 200030, People’s Republic of China
One-dimensional α-MnO2 nanowires with a controlled width of 10–20 nm have been developed by means of ultrasonic waves from mesoporous carbon using KMnO4 as the precursor. The formation mechanism has been proposed based on the results. A peak around 100 K was detected in the temperature-dependence of magnetization curve, indicating the ferromagnetic state in nanocomposite mesoporous carbon-MnO2, which is in agreement with the transition temperature found from the magnetization versus applied magnetic field curve. The magnetization versus temperature curve of the obtained MnO2 nanowires showed a magnetic transition at about 50 K, illustrating that a parasitic ferromagnetic component is composed on the antiferromagnetic structure of MnO2. The advantage of the method reported here is that phase-controlled synthesis of α-MnO2 nanowires was implemented regardless of pH, temperature, and types of ions in the reaction system. A major advantage of this approach is the efficient, fast, and reproducible control of width and the facile strategy to synthesize nanowires MnO2, in addition to the high purity of the resultant material.
(Received March 16 2006)
(Accepted June 23 2006)
(Online publication March 03 2011)