Flower-like FeWO4/f-MWCNTs Sphere for Triethylamine Gas Sensors Operating at Room Temperature: Sensing Performance, Mechanism Study, and Application to Detection of Fish Freshness

Triethylamine (TEA) is a colorless organic liquid known for its high volatility that poses significant irritation to the human respiratory tract; meanwhile, TEA can be released from decaying fish, which can be monitored by a gas sensor. However, conventional TEA gas sensors typically require high operating temperatures, leading to a substantial energy consumption. To address food safety concerns and promote environmental sustainability, the advancement of a TEA sensor that works at room temperature is urgently needed. In our work, an FeWO₄/f-MWCNTs-3 chemoresistive gas sensor was fabricated by the hydrothermal method, integrating FeWO₄ with multiwalled carbon nanotubes treated with mixed acids (f-MWCNTs). The sensor demonstrates superior performance, owing to its elevated specific surface area, total pore volume, and synergistic effect of p–p heterojunctions. FeWO₄/f-MWCNTs-3 demonstrates excellent reproducibility, moisture resistance, stability, a minimal detection threshold of 1 ppm, and relatively rapid response/recovery times of 15/63 s. It attains a 113% response at 100 ppm of TEA at 25 °C. The applicability of FeWO₄/f-MWCNTs-3 for assessing fish freshness via TEA concentration analysis from pomfret fish stored at ambient temperature for 14 days was validated, indicating its significance in fish freshness detection methodologies. Additionally, the gas-sensing mechanism of this sensor was further explored using density functional theory (DFT).