We present results on the development of nanocomposite NiO:Au thin-film hydrogen sensors, which are able to detect hydrogen concentrations as low as 2 ppm in air, operating at low temperatures in the range 125-150 degrees C. Thin NiO films were sputter-deposited on oxidized silicon substrates. The structural, morphological, and nanomechanical properties of the films were investigated with respect to post-deposition annealing. Au nanoparticles were added on the NiO surface via pulsed laser deposition and the films were tested as hydrogen sensors before and after Au deposition. The performance of the NiO films as hydrogen sensors improved significantly in the presence of Au nanoparticles on the surface. The detection limit (lowest detectable hydrogen concentration) decreased by two orders of magnitude, while the response time also decreased by a factor of three. (C) 2013 Elsevier Ltd. All rights reserved.