Towards understanding the morphological, magnetic, optical and electrical properties of MnO2 nanowires for magneto-and optoelectronic applications

Abstract

Mixed solutions of manganese sulfate and potassium permanganate were hydrothermally used to synthesis α-MnO2 nanowires. Energy dispersive analysis of X-ray revealed the formation of stoichiometric MnO2 and X-ray diffraction revealed the formation of single crystalline α-MnO2. Examinations using both SEM and TEM yielded nanowires with diameters ranged from 40 to 50 nm and lengths ranged from 5 to 6 µm. The magnetic properties revealed that the α-MnO2 NWs exhibit ferromagnetic/antiferromagnetic characteristics at liquid nitrogen and room temperatures. This kind of materials may be find usage in electromagnetic shielding applications. Direct optical band gap of 2.6 eV, that was blue shifted from the bulk value, was reported. Photoluminescence examinations displayed a strong emission peak around 395 nm and broad peak around 477 nm. The α-MnO2 NWs showed a semiconducting behavior where the resistivity decreased with increasing temperature. Two activation energies were reported; the low temperature activation energy was 0.089 eV and the high temperature activation energy was 0.782 eV. Based on the observed high intensity UV emission peak, the obtained α-MnO2 NWs may find applications in UV light emitting diodes.