Hierarchical urchin-like WO2.72 microspheres decorated by uniform Au nanoparticles were synthesized via a two-step deposition process. The two-step deposition process, including weak reduction deposition and photo-deposition, ensures uniform size and well-dispersed Au nanoparticles. The gas-sensing properties of WO2.72 and Au/WO2.72 for trimethylamine (TMA) were investigated. The results show that Au/WO2.72 has more outstanding gas-sensing performances, especially 3 wt% Au-loaded WO2.72 (A3/WO2.72). A3/WO2.72 not only has superior selectivity and response for TMA gas but also exhibits fast response and recovery time. The response of A3/WO2.72–100 ppm of TMA at 260 °C can attain 87.3, which is approximately 6.1 times of pure WO2.72. Besides, the good long-term effectiveness of A3/WO2.72-based sensor also can be observed. The mechanism of enhanced gas-sensing performances derived from the synergy of morphology, composition, and the sensitization effect of Au nanoparticles is proposed, which will facilitate the design and development of sensors decorated by noble metal.
