Wet chemical synthesis of diameter tuned NiO microrods: microstructural, optical and optical power limiting applications

Diameter tuned NiO microrods have been prepared by a wet chemical route. Individual microrods measured 9 mu m in length with a diameter of 350 nm, which could be increased by changing the annealing temperature. Crystalline and microstructural parameters were studied by Williamson-Hall (WH) analysis, showing a reduction of microstrain upon increase of temperature due to lattice relaxation. The absorption spectrum reveals the presence of peaks at 350 nm and 250 nm due to the transition from 2p states of oxygen to 3d states of Ni ions, and the transition from the defect band, respectively. Strong UV emission peaks (361, 392 nm) and visible emission bands (436, 467 and 560 nm) are observed in the steady state luminescence spectra. The time resolved photoluminescence spectra show a fast tri-exponential decay with lifetime components of 26, 74 and 670 ps. Open aperture Z-scan measurements conducted at 532 nm using 5 ns laser pulses reveal that the NiO nanorods are good optical limiters which may have potential device applications.