Synthesis, characterization and gas sensing properties of Ni1-xZnxO nanoparticles and Ni1-xZnxO/ZnO nanocomposites

The selectivity of oxide based resistive gas sensors remains a challenging issue as they suffer from low selectivity. Researchers have suggested various ways to overcome this problem of cross-sensitivity. Thus it was established that a significant improvement can be reached by using mixed metal oxide system [1], by microstructural modification and by the use of dopants and catalysts [2] or by controlling the size and the shape of the oxide grains. Among mixed metal oxides, the nanocomposite materials and the doped materials are very promising for gas sensor applications. Indeed, various authors have reported sensitive and selective gas sensing characteristics of composite oxide materials made by different methods [3]. According to our knowledge, reports on the NiO-ZnO systems are limited [4] and the literature on Zn doped NiO used as gas sensor is very scarce. In this work we report for the first time, the synthesis of Ni1-xZnxO nanoparticles and Ni1-xZnxO/ZnO nanocomposites at relatively low temperature using corresponding metal malonate as single batch precursors. These materials were obtained by thermal decomposition (~ 360°C) of the corresponding metal malonate presynthesized by coprecipitation in aqueous solution. All the precursors were characterized by ICP-AES, FTIR, and TGA and these analyses confirm the structure of the precursors as Ni1-xZnx(OOCCH2COO).2H2O. The presence of mixed phase nanoparticles after thermal decomposition of the precursor was confirmed by a combination of characterization techniques (SEM, XRD, XPS and ToF-SIMS). The gas sensing properties of the synthesized materials were examined using some reducing and oxidant gases showing significant changes in behavior in function of the doping.