Mechanically reliable PAN/PANI/SnO2 heterojunction nanofiber membranes for high-performance room-temperature NH3 sensing with humidity-modulated response

A self-supporting polyacrylonitrile (PAN)/polyaniline (PANI)/SnO 2  nanofiber membrane was fabricated. • The self-supporting structure endows the sensor with high mechanical reliability. • The p–n heterojunction constructed between PANI and SnO 2 enhances NH 3 adsorption and interfacial charge transfer. • Surface hydroxylation and the hydrogen-bond network promote the increase in the NH 3  response under high-humidity conditions. Flexible room-temperature ammonia (NH 3 ) sensors hold considerable promise for wearable environmental monitoring and industrial safety, yet their practical deployment remains constrained by insufficient sensing response, inadequate mechanical durability, and pronounced humidity interference. Herein, a flexible polyacrylonitrile (PAN)/polyaniline (PANI)/SnO 2 heterojunction sensor was fabricated. The sensor exhibited a response of 5.2 toward 100 ppm NH 3 at room temperature, approximately 2.3 times that of the pure PANI sensor, with response/recovery times of 126/296 s. Meanwhile, the sensor demonstrated excellent flexibility, with a bending-induced response variation of less than 5% and retained 95% of its initial response after 1000 folding cycles. Density functional theory (DFT) calculations revealed that, compared with pristine PANI, PANI/SnO 2 showed stronger NH 3 adsorption and greater charge transfer. Experimentally, humidity was found to exert a two-stage regulatory effect on the NH 3 sensing performance of PANI and PANI/SnO 2 sensors. Combined with ab initio molecular dynamics (AIMD) simulations, the results indicate that humidity plays a dual role in the sensing process: at low humidity, competitive adsorption dominates and leads to a decreased response, whereas at high humidity, hydrogen-bond-assisted interfacial regulation promotes response recovery. This work provides an effective strategy for developing flexible PANI-based NH 3 sensors and offers new insights into humidity-dependent sensing mechanisms. Download: Download high-res image (339KB) Download: Download full-size image