La‐Doped Mullite Bi ₂ Fe ₄ O ₉ Chemiresistive Gas Sensor for Ultra‐Highly Selective Detection of Ethylene Glycol

The detection of ethylene glycol (EG) vapor is critical for industrial safety and environmental monitoring, yet existing chemiresistive sensors suffer from limited selectivity and stability. Herein, a facile synthesis of lanthanum-doped mullite bismuth ferrite mullite (La-Bi₂Fe₄O₉) is presented. Atomic-resolution imaging and microchemical analysis, in combination with theoretical calculations, confirm uniform Bi-site doping, increased oxygen vacancy concentration, and enhanced gas adsorption. The optimized BLFO-5 sensor demonstrates exceptional EG-sensing performance, with ultrahigh selectivity, outstanding reproducibility and long-term stability, and an ultralow detection limit. By integrating in situ infrared spectroscopy and density functional theory (DFT) calculations, we elucidate the EG surface oxidization reaction mechanism, revealing significantly enhanced dehydrogenation kinetics and a complete oxidation pathway. Moreover, we develop a wearable real-time gas monitoring platform for practical validation and incorporate deep learning algorithms to improve gas recognition accuracy. This work presents an integrated strategy for chemical gas sensing that combines material defect engineering, mechanistic understanding, and functional device development, enabling wireless EG quantification in complex environments.