Silicon nanostructures were realized using metal assisted chemical etching of silicon wafer (100) for two different etching times: 5 minute and 10 minute. Structural and optical properties of silicon nanostructures were investigated using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and photoluminescence (PL). XRD analysis probes the changes in crystallinity during etching and reveals reflection plane (220) of obtained silicon nanostructures. UV and visible spectra of photoluminescence from Si nanostructures suggest the optically active nature of Si at nanoscale and confinement of carrier. These results show that the structural and optical properties of Si nanostructures strongly depend on etching time of silicon wafer. © 2019 IOP Publishing Ltd. All rights reserved.