AACVD and gas sensing properties of nickel oxide nanoparticle decorated tungsten oxide nanowires†
Here, we show that the aerosol assisted chemical vapor deposition process is suitable for growing single crystalline tungsten oxide nanowires loaded with nickel oxide nanoparticles. This method allows achieving of a wide range of nickel oxide loadings on tungsten oxide nanowires with high effectivity. It also allows for the direct growth of these nanomaterials onto application substrates for developing resistive metal oxide gas sensors. Different morphological and compositional analysis tools have been employed for the characterization of the nanomaterials, finding that nickel oxide nanoparticles are homogeneously distributed over the tungsten oxide nanowire surface. However, at high Ni loadings, even though the size of the nanoparticles remains unchanged, they form agglomerates, especially at the tips of tungsten nanowires. The gas sensing properties of the different nanomaterials grown towards methane, ethanol, nitrogen dioxide and hydrogen sulfide have been studied. The optimized loading of tungsten oxide with nickel oxide nanoparticles has a positive effect on increasing the sensitivity and selectivity of the resulting nanomaterial to hydrogen sulfide, reaching a five-fold increase in the response towards this species. This improvement is attributed to combined chemical and electronic sensitization effects. Therefore, these nanomaterials show good potential for developing inexpensive resistive sensors able to monitor the presence of hydrogen sulfide in the environment.