Abstract
Sensitive and selective detection of ammonia (NH 3 ) is essential for ensuring safety in industrial facilities and environmental monitoring. However, simultaneously achieving a high response, rapid recovery, and long-term stability at room temperature (RT) remains challenging. In this work, a free-standing polypyrrole (PPy)-coated poly(vinylidene fluoride)/titanium (IV) oxide/graphitic carbon nitride (PVDF/TiO 2 /g-C 3 N 4 ) (PPTC) nanofiber-based chemoresistive gas sensor was fabricated and investigated. The proposed composite structure combines the high sensitivity of PPy to NH 3 , the ability of TiO 2 to form p-n heterojunctions and enhancement of charge carrier modulation, the adsorption properties of g-C 3 N 4 and a well-developed porous nanofibrous morphology with a relatively high surface area. The results of structural, morphological, thermal and surface characterizations confirmed the successful formation of the hybrid composite. The obtained gas-sensing characteristics demonstrated the efficiency of the developed multicomponent structure, representing one of the best performances among related PPy-based NH 3 sensors operating at RT. Gas measurement results showed NH 3 detection in the range of concentration from 1 to 100 ppm, with a maximum response of 101% toward 100 ppm of NH 3 . The limit of detection was 1 ppm. The PPTC-based sensor also demonstrated good linear response dependence (R 2 = 0.95), response and recovery times of 106 and 188 s, respectively, and high signal repeatability under multiple measurement cycles. Besides, the sensor showed marked selectivity to NH 3 compared to various target gases. The obtained gas-sensing characteristics demonstrated the efficiency of the developed multicomponent structure, representing one of the best performances among related PPy-based NH 3 sensors operating at RT (23°C).