A hybrid structure of platinum nanoparticles (Pt NPs) and a Pt thin film are employed to fabricate a new Pt NP/Pt thin film/GaN-based Schottky diode-type ammonia sensor. Pt NPs are formed by a drop coating and UV illumination approach. The increased surface-area-to-volume ratio and "spillover" effect of Pt NPs are beneficial in ammonia sensing. Due to the synergistic catalytic activity of Pt NPs and Pt thin film, the studied device shows good ammonia sensing properties, including a high sensing response of 522.1 under 1000-ppm NH3/air gas at 473 K and an extremely low detecting level of 0.4-ppm NH3/air. A thermodynamic analysis is employed to study the related ammonia sensing mechanism. Furthermore, a Kalman filter and the related algorithm are introduced to effectively reduce the redundant data without affecting the original sensing results. Based on the good performance and advantages of a relatively simple structure and easy fabrication, the studied device is promising for ammonia sensing and wireless transmission applications.
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