Drastically Enhanced Ammonia Sensing of Pt/ZnO Ordered Porous Ultra-Thin Films

Two-dimensional ordered thin films hold promise for high performance gas sensors owing to their controllable morphology. In this work, Pt/ZnO ordered porous sub-micrometer films were synthesized by polystyrene sphere monolayer colloidal crystal template method, and their gas-sensing properties were systematically studied. The ordered porous films presented a honeycomb-like morphology with a thickness of 500 nm. Pristine ZnO exhibited an unusual p-type like response to NH3 with resistance increase and low sensitivity, while Pt-loaded samples showed n-type sensing with remarkably enhanced sensor performance. Pt loading led to a 200-times larger response of 324 to 100 ppm NH3 and a high sensitivity of 10.5 ppm(-1) at 330 degrees C. Significantly reduced response time and depressed the cross-sensitivity to common interfering gases were also achieved. These render the Pt/ZnO ordered porous films much superior NH3 sensing performance to state-of-the-art ZnO based sensors. The excellent performance may be attributed to the synergistic effects of the catalytic and electronic promotion of Pt and unique nano-morphology of the porous films.