Abstract
The detection of toxic gases at trace levels is crucial for environmental monitoring and human safety. In this work, we report the synthesis and gas-sensing performance of a novel redox-engineered nanocomposite comprising gold (Au \(^{0}\) ) nanoparticle cores encapsulated within benzene sulphonic acid (BSA) doped polypyrrole (PPy) shells, denoted as Au \(^{0}\) @PPy \(^{+}\cdot C_{6}H_{5}SO_{3}^{-}\) . The nanocomposites were synthesized via in situ oxidative polymerization of pyrrole in the presence of HAuCl \(_{4}\) and BSA, resulting in a uniform core–shell architecture with enhanced redox activity. The synergistic combination of catalytic Au \(^{0}\) cores, conductive PPy shells, and acid doping yielded a material with superior surface reactivity and charge transport properties. Chemiresistive sensors fabricated using this composite exhibited highly sensitive, reversible, and reproducible responses toward selected toxic gases, including Cl \(_{2}\) , NH \(_{3}\) , CO, SO \(_{2}\) , NO \(_{2}\) , and LPG under ambient conditions. Notably, the sensor displayed a rapid increase in resistance upon exposure to oxidizing gases (Cl \(_{2}\) , SO \(_{2}\) , NO \(_{2}\) ), and a sharp decrease upon interaction with reducing gases (NH \(_{3}\) , CO, LPG), confirming the p-type nature of the composite. The device demonstrated excellent sensitivity, long-term stability, and full recovery upon air purging, highlighting its potential for real-time, low-power toxic gas monitoring applications. This study provides valuable insight into redox modulation and core-shell engineering strategies for the design of high-performance gas-sensing materials.
Graphical abstract
