High-Performance Ammonia Sensing with Citrus Hystrix-Mediated ZnO Nanoparticles in TFT-Based Devices

We present a sustainable green synthesis approach for zinc oxide nanoparticles (ZnO NPs) utilizing Citrus hystrix leaf extract and their application as an active medium in a thin film transistor (TFT)-based ammonia gas sensor. For the first time, ZnO NPs derived from Citrus hystrix serve as a receptor layer in a thin film transistor (TFT) device, enabling selective ammonia detection at a significantly reduced initiation temperature. The synthesized ZnO NPs, with a wurtzite structure and an average crystallite size of approximately 14 nm, are deposited onto the TFT sensor without the need for an external conducting layer. The sensor demonstrates excellent sensitivity and selectivity, achieving a maximum response of ~85 % at 20 ppm, with a rapid response time of about 10 seconds at room temperature. Notably, the TFT device exhibits an electron mobility of ~10.2 cm²/V ⋅ s and a high on/off ratio (>10⁴) at room temperature. The sensing mechanism is attributed to the oxidation-reduction interactions between surface-adsorbed oxygen and NH₃ molecules on the ZnO NPs, which modulate the device's electrical conductivity. This work underscores the importance of eco-friendly fabrication of high-performance, durable devices, addressing contemporary environmental and economic concerns.