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

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.