Enhanced ethanol sensing performance of porous ultrathin NiO nanosheets with neck-connected networks

Porous ultrathin NiO nanosheets have been synthesized by a simplified chemical bath deposition method with subsequent thermal decomposition of a layered precursor of nickel hydroxide (Ni(OH)2). The crystalline and morphological structures of products, which were characterized by X-ray diffraction, field-emission scanning electron microscopy and high resolution transmission electron microscopy, show that the nanopores form with a phase transition at the calcination process. The pure cubic NiO phase, with an average grain size of 4.67 nm and a thickness less than 5 nm, forms at 450 °C for 2 h in air. Moreover, the NiO nanosheets synthesized here show an enhanced response to ethanol at a low temperature of 200 °C. The unique architecture with neck-connected networks and a high specific area was applied to explain the enhancement of the ethanol sensing performance. Furthermore, the sensor exhibits an excellent selectivity to ethanol against methanol, acetone, toluene, hydrogen, and methane by a cross-response test.