Nickel hydroxide samples were deposited onto glass substrates using Ni(NO3)(2)center dot 6H(2)O and aqueous ammonia by chemical bath deposition technique. The influence of pH of solution was investigated by means of X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared, Raman spectroscopy, optical absorption and BET analysis. The as-deposited samples were identified as beta-Ni(OH)(2), were transformed into NiO after heat treatment in air at 500 degrees C for 2 h. Porous nickel oxide nanosheets are obtained by heating nickel hydroxide nanosheets. The optical transitions observed in the absorbance spectra below optical band gap is due to defects or Ni2+ vacancies in NiO samples. The band gap energy of NiO samples changes between 3.37 and 3.52 eV depending on the pH values. (C) 2015 Elsevier Ltd. All rights reserved.