Biocompatible and degradable gelatin dielectric based low-operating voltage organic transistors for ultra-high sensitivity NH₃ detection

We developed an ultra-high sensitive ammonia (NH₃) gas sensor that incorporates a biocompatible/degradable gelatin dielectric layer in a top-contact organic thin-film transistor. The sensitivity study of the gas sensor involves detecting the saturation current change with analyte concentrations, exhibiting a saturation current changing from 17.6% to 45.1% for the concentration of NH₃ from 500 ppb to 30 ppm. Importantly, this type of sensing platform shows an excellent detecting limit of 174.0 ppb with a low operating voltage of 4 V. To understand the mechanism of this phenomenon, we fabricated another group of devices that incorporates an additional thin layer of polystyrene covered on top of the gelatin layer. The response sensitivity of this type of sensor is only 5.1% for the NH₃concentration of 30 ppm. Systematic studies including morphology analysis of the organic films and electrical properties of the sensors were performed. The results indicate that the functional groups on the gelatin dielectric surface groups have ability to adsorb NH₃ analyte, thereby leading to a superior sensing performance. This work demonstrates that the biocompatible/degradable gelatin with unique functional groups is applicable for readily manufacturable low-operating voltage and high-performance thin-film transistor-based gas sensors.