S. Vallejos

Aerosol-Assisted CVD-Grown PdO Nanoparticle-Decorated Tungsten Oxide Nanoneedles Extremely Sensitive and Selective to Hydrogen

We report for the first time the successful synthesis of palladium (Pd) nanoparticle (NP)-decorated tungsten trioxide (WO3) nanoneedles (NNs) via a two-step aerosol-assisted chemical vapor deposition approach. Morphological, structural, and elemental composition analysis revealed that a Pd(acac)2 precursor was very suitable to decorate WO3 NNs with uniform and well-dispersed PdO NPs. Gas-sensing results revealed that decoration with PdO NPs led to an ultrasensitive and selective hydrogen (H2) gas sensor (sensor response peaks at 1670 at 500 ppm of H2) with low operating temperature (150 °C). The response of decorated NNs is 755 times higher than that of bare WO3 NNs. Additionally, at a temperature near that of the ambient temperature (50 °C), the response of this sensor toward the same concentration of H2 was 23, which is higher than that of some promising sensors reported in the literature. Finally, humidity measurements showed that PdO/WO3 sensors displayed low-cross-sensitivity toward water vapor, compared to bare WO3 sensors. The addition of PdO NPs helps to minimize the effect of ambient humidity on the sensor response.

Microsensors based on Pt–nanoparticle functionalised tungsten oxide nanoneedles for monitoring hydrogen sulfide

Gas microsensors based on non-functionalised and functionalised tungsten oxide nanoneedles with platinum nanoparticles, synthesised and integrated directly onto transducing microsensor platforms via Aerosol Assisted Chemical Vapour Deposition, are fabricated and tested towards various concentrations of hydrogen sulfide and some interfering gases (CO, H2, NH3, EtOH). Results show improved sensing characteristics in functionalised microsensors as a result of the incorporation of platinum nanoparticles of reduced size (<4 nm) with even distribution onto highly crystalline tungsten oxide nanoneedles. An arrangement of both non-functionalised and functionalised sensing films in an array of sensors shows the potential of these devices to selectively monitor hydrogen sulfide.

AA-CVD growth and ethanol sensing properties of pure and metal decorated WO3 nanoneedles

This paper reports the co–deposition, in a single step, of metal nanoparticles and tungsten oxide nanoneedles by aerosol–assisted chemical vapour deposition. The method leads to the growth of WO3 nanoneedles decorated with copper, gold or platinum metal nanoparticles, respectively. Scanning electron microscopy, transmission electron microscopy and energy–dispersive X–ray analysis have been used to investigate the morphology and composition of the different nanostructures grown on Al2O3 substrates. Gas sensors employing the different nanostructures have been fabricated and a preliminary characterisation of their sensing properties to ethanol vapours is shown. Our nanomaterials behave as n–type semiconductors in the presence of ethanol, and those decorated with metal nanoparticles show high stability, high reproducibility, high response and rapid detection of ethanol vapours at moderate operating temperatures (i.e. 250°C).