A wireless gas sensing system enabling real-time seafood freshness monitoring based on Ru-In2O3 microtubes with dual-enhanced sensitivity and selectivity

Abstract

The growing demand for seafood safety necessitates smart sensors with real-time monitoring capability for the biomarker triethylamine (TEA). However, it still faces tremendous challenges due to the limited sensitivity and selectivity of the sensing material. This study develops a topological transformation from a Ru-MIL-68 precursor to a Ru-doped In₂O₃ hollow hexagonal prism. These structural merits, including hierarchical porosity, uniform Ru dispersion, and abundant oxygen vacancies, endow this material with enhanced gas adsorption-diffusion kinetics and surface reactivity. The optimized Ru-In₂O₃-0.8 sensor exhibits exceptional TEA sensing performance: ultrahigh response (R_a/R_g = 493–100 ppm), fast recovery (τ_rec = 22 s), and a low detection limit (LOD = 11.3 ppb). Density functional theory calculations delineate that TEA binds preferentially to the Ru-In₂O₃ surface with a much larger adsorption energy than that of TEA on bare In₂O₃ or other gas molecules on Ru-In₂O₃, supporting the enhanced sensitivity and selectivity achieved by introducing Ru. Furthermore, a smart gas sensing system based on the Ru-In₂O₃-0.8 material demonstrates a real-time half-fin anchovy freshness monitoring application on mobile phones. This work not only proposes the structural modulations for exploration of advanced sensing materials but also guides the potential for real-time analysis, monitoring and diagnosis.