On the way to eco-friendly fabrication of polyaniline-based ammonia sensors with high sensitivity and room temperature operation

Organic sensors based on conductive polyaniline (PAni) are a promising solution under development for detecting ammonia. The sensors are advantageous due to their performance, their low cost of production and ease of processing. During the fabrication of sensors, the polymer, and its doping agent are usually dispersed in an organic solvent (e.g., m-cresol or N-methyl-2-pyrrolidone), which does not meet the required safety and sustainability standards. The aim of this study is to report the remarkable detection performances of polyaniline-based sensitive layers elaborated in safer solvents. Herein, PAni doped with camphor-10-sulfonic acid (CSA) was mixed and mechanically dispersed in various solvents. Obtained PAni:CSA films were analyzed using infrared spectroscopy, while morphological characteristics were determined using Scanning Electron Microscopy. The analysis of detection performances shows that the solvent employed for the dispersion of PAni has a significant effect on the sensor's sensitivity. For instance, high sensitivities (about 300 %/ppm) and low limits of detection (approximately 2 ppb) are obtained for devices elaborated in ethanol and dl-limonene. After evaporation, these incompatible solvents lead to the formation of a porous active layer, facilitating the interactions with ammonia. The sensitivities of these devices remain stable after 5 months, independent of the humidity level. Thus, using non-stabilizing solvents to disperse polyaniline offers a promising approach to enhance the sensitivity and limit the detection of room-temperature organic ammonia sensors.