Room-Temperature Trimethylamine Gas Sensor with Enhanced Performance Using Biomass-Derived Carbon Quantum Dot Modified Biochar

s This study presents an eco-friendly fabrication method for high-performance room-temperature (RT, 25 °C) gas sensors by integrating biomass-derived N-doped carbon quantum dots (N-CQDs) with biochar (BC). The N-CQDs were hydrothermally synthesized from waste milk and the BC substrate was devrived from carbonized Lyocell fiber mask waste. The constructed N-CQDs@BC heterostructure through simple mechanical mixing and milling exhibited better trimethylamine (TMA) sensing capabilities, achieving a remarkable response magnitude of 21k% to 500 ppm TMA gas at RT with a moderate response/recovery time of 82.24   s/10.71   s. The sensor demonstrated outstanding stability by maintaining 21k% response after 45 days of ambient storage and achieved a low detection limit of 1.07 ppm. Density functional theory calculations revealed that N-doping significantly enhanced the material’s adsorption capabilities for both O 2 and TMA. This improvement in adsorption energy, combined with increased charge transfer, underscores the effectiveness of N-doping in optimizing the material’s electronic structure and reactivity. By exclusively utilizing biomass waste resources, this work establishes a simple solution for developing eco-friendly semiconductor gas sensors that combine high sensitivity cost-effectiveness, and environmental sustainability with promising applications.