WO3 nano-rods sensitized with noble metal nano-particles for H2S sensing in the ppb range

•20 and 29 nm Pt and Au nano-particles were synthesised by reduction method.•Hexagonal WO3 nano-rods were sensitized with deposited noble metal nano-particles.•Sensitized WO3 nano-rod structures show improved gas sensitivity properties in terms of sensitivity, selectivity and response time.•Detection of 25 ppb H2S was demonstrated.

Hydrothermally grown hexagonal WO3 nano-rods were sensitized by additional Pt and Au nano-particles. The size of the 20–29 nm noble metal nano-particles were stabilized with methoxy-polyethylene glycol, and their solution was mixed with the tungsten-oxide nano-rod suspension. Controlled sized suspension drops of activated and pure reference material were deposited on the top of micro-hotplate with gold interdigital electrodes on top. The gas sensitive properties were measured for NH3 and H2S in a temperature range of 140–300 °C. Noble metal nano-particles multiplied the gas sensitivity for H2S, whereas no significant effect could be detected for NH3. With gold nano-particles a lower detection limit of 25 ppb could be achieved. The response time is in the range of 30–80 s, whereas typically 300 s is needed for complete recovery.

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