Highly (101) oriented MnO2 nanofibers synthesized using novel spray pyrolysis technique

Abstract

In the present work, nanofibrous MnO2 thin films were prepared on glass substrate by a novel spray pyrolysis deposition route for different manganese acetate solution concentration from 0.5 to 2 M. The effect of solution concentration on the structural, optical and morphological properties of the films was investigated. X-ray diffraction results revealed highly (101) oriented tetragonal phase of α-MnO2 without the formation of any secondary phase. The crystallinity of the films was found to be greatly improved with increase in precursor concentration. A strong photoluminescence (PL) emission with a peak at 375 nm was detected upon excitation of the MnO2 nanofibers at room temperature, confirming that the film exhibit less defect density signifying the high crystal quality of the films. The blue shift in the PL emission caused by increasing solution concentration reveal the tunable band gap of MnO2 nanofibers, which is also confirmed from the optical absorption results which show increase in energy gap value from 2.56 to 2.77 eV. Scanning electron microscopy images revealed the formation of MnO2 nanofibers with high crystalline quality, which assemble to be honey comb like structures for the film prepared at 1.5 M concentration, suitable for super capacitor device applications.