Polyaniline/Bismuth Oxychloride Heterojunction-Inspired Wireless and Passive Ammonia Sensors for Exhaled Air...

Ammonia ranks as the most typical biomarker in the analysis of exhaled breath. However, developing ammonia gas sensors remains challenging for noninvasive exhaled human breath monitoring. In this work, a polyaniline/bismuth oxychloride (PANI/BiOCl) heterojunction-inspired ammonia gas sensor was reported for real-time exhaled biomarker analysis. The PANI/BiOCl heterojunction-enabled gas sensor exhibits a very short response time (11 s), an ultralow limit of detection (0.5 ppm), a high response value (1.5%, even at 1 ppm), and excellent stability under ambient conditions. The intimate contact across the interface between BiOCl and PANI can greatly promote the charge carrier migration and separation. A wireless passive device was further developed by integrating a PANI/BiOCl heterojunction and a near-field communication tag, validating the feasibility of its use for expiratory disease monitoring. This work establishes an innovative pathway for the systematic development of high-performance wireless gas sensors.