Hydrothermal synthesis and characterization of silica nanowires using rice husk ash: an agricultural waste

One-dimensional structures are the smallest dimension structures that represent a unique system for analyzing phenomena at the Nanoscale. Nanowires, which can be used for space confined transport phenomena and enhanced optical properties, are believed to play significant role in the function and integration of Nano electronics and Nano optoelectronics devices. Nanowires with well controlled morphology and extremely high aspect ratio can be obtained by various complex techniques but the demand of upcoming future technology is to synthesize large scale 1D nanostructures with simple and efficient cost effective methods. With this view, in the present study, large scale amorphous silica nanowires (SiO₂ NWs) were synthesized from rice husk ash using Fe₂O₃ assisted hydrothermal method and characterizations of these nanowires along with rice husk ash (RHA) containing porous silica, were done using various techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis spectroscopy and photoluminescence (PL). The structural study of silica nanowires were studied using XRD, indicating the amorphous phases of silica in both RHA as well as nanowires. The chemical composition along with symmetric or anti-symmetric starching bonds of amorphous SiO₂ NWs and RHA was confirmed using FTIR. The morphological study was done using SEM and TEM. The SiO₂ NWs so obtained have diameter in the range from 15 to 35 nm and length about 0.5 µm. In optical study, the enhanced band gap of amorphous SiO₂ NWs as compared to RHA was observed using UV–Vis spectroscopy. PL spectroscopy shows strong blue light emission by silica nanowires as compare to RHA. This study opens up new areas for research to modulate optoelectronic properties of SiO₂ nanowires for the novel device application.