Bilayer Au nanoparticle-decorated WO3 porous thin films: On-chip fabrication and enhanced NO2 gas sensing performances with high selectivity.

Graphical abstract On-chip fabricated bilayer Au NP-decorated WO 3 porous thin films with high sensing selectivity to NO 2. Highlights • Bilayer Au nanoparticle decorated WO 3 porous film were one-step fabricated on commercial ceramic tube substrate. • The film consists of hexagonally ordered WO 3 bowl with a homogeneous thickness of ca. 1.5 μm. • Au nanoparticles decoration increases sensitivity of the sensor from 5.0 to 96.0 towards 1 ppm NO 2 at 150 °C. • The Au decorated WO 3 film shows perfect selectivity to NO 2 gas. • A combined surface chemical and interbedded electronic sensitization mechanism was proposed. Abstract We present the on-chip fabrication of bilayer Au NP-decorated WO 3 nanoporous thin films (B-Au/WO 3) via layer-by-layer stacking of a sacrificial colloidal template with periodic Au sputtering deposition. Technical analysis shows that the B-Au/WO 3 film is homogeneous and consists of a hexagonally ordered bowl-like structure, whose surface is uniformly decorated with crystalline Au NPs. The B-Au/WO 3 sensing film shows a sensitivity of 96.0, a response time of 9.0 s and a recovery time of 16.0 s for 1 ppm NO 2 at a low operating temperature of 150 °C. This significantly exceeds performances of bare WO 3 counterpart. Also, the B-Au/WO 3 sensor demonstrates obviously enhanced sensing responses over operating temperature ranges of 75–225 °C and perfect selectivity to NO 2 gas. We proposed a combined sensing mechanism, the surface Au NPs dominated chemical sensitization and inter-bedded Au NP-induced electronic sensitization, to explain the perfect sensing performances in sensitivity, response, and selectivity. The template-mediated approach focuses on precise single-layer control and facilitates direct integration of the sensing film onto the required sensor substrate. The addressed on-chip fabrication strategy along with Au NPs decoration technique might provide promising applications in construction of advanced chemiresistive gas sensors, photocatalysts and electrochromic smart windows. [ABSTRACT FROM AUTHOR]