Facile synthesis of silver and copper modified graphitic carbon nitride for volatile organic compounds sensing

Volatile organic compounds (VOCs) pose significant health risks when inhaled or ingested in large quantities. Metal oxide-based solid-state gas sensors are commonly utilized for VOCs detection, including methanol, however their high operating temperature and selectivity are both biggest challenges. In this context, graphitic carbon nitride (g-C₃N₄) has emerged as a promising alternative for VOCs sensing due to its superior sensing properties. In this work, Cu and Ag doped g-C₃N₄ was synthesized via the polycondensation method for VOCs sensing applications. All the samples showed a selective response to methanol at room temperature. Notably, the Ag/g-C₃N₄ sensor exhibited a significantly enhanced response (~27.5) compared to both undoped g-C₃N₄ (~3.58) and Cu/g-C₃N₄ (~9.82) sensors towards 200 ppm methanol. The Ag/C₃N₄ based sensor showed rapid response (21 s) and recovery (17 s) times, along with excellent short-term and long-term stability. It was found that Ag/C₃N₄ sensor exhibited a good response to humidity levels ranging from 9 % to 93 % RH, without any significant variation observed when deposited on the ceramic and flexible polyimide substrates. Further, considering its practical applicability, the Ag/C₃N₄ sensor showed successful detection of alcohol in human breath, highlighting its potential for real-world applications.