Thermodynamic and Kinetics Aspects of Spherical MnO 2 Nanoparticle Synthesis in Isoamyl Alcohol: An Ex Situ Study of Particles to One-Dimensional Shape Transformation

Thermodynamically stable and robust α-MnO 2 nanowire has been obtained in gram quantity from low cost starting materials KMnO 4 and isoamyl alcohol. Here KMnO 4 acts as an oxidizing agent and eventually produces the corresponding acid which caps the spherical MnO 2 particles. The MnO 2 nanoparticle formation is monitored by UV−visible spectrophotometry, and the activation energy of the reaction is reported to be 44−49 kJ mol −1 . The particles upon modified hydrothermolysis (MHT) reaction produce nanofibrils and the nanofrabrils finally evolved stable α-MnO 2 nanowires by heat treatment. The spherical MnO 2 nanoparticles under MHT conditions undergo oriented attachment and result in MnO 2 nanofibrils, i.e., the shape transformation takes place from spherical MnO 2 nanoparticles to nanofibrils. This has been documented in this study. The nanofibrils, being thermally unstable, upon heat treatment easily change to robust single-crystalline defect-free α-MnO 2 nanowires with an exact angle of 90° between (200) and (002) crystal planes.