Room-Temperature NH3 Sensors Based on Polyaniline-Assembled Graphitic Carbon Nitride Nanosheets

To address the challenge of rapid detection of trace amounts of NH3 at room temperature, the NH3 gas sensor based on the PANI/g-C3N4 (graphitic carbon nitride) nanocomposite was fabricated via the hydrothermal exfoliation of g-C3N4 combined with in situ oxidative polymerization of PANI. The test results demonstrated that the sensor based on 30 mol % g-C3N4 nanosheet-doped PANI hybrid (PCN (30)) exhibited the highest sensitivity to NH3. The sensing response of the PCN (30) hybrid sensor (19.53) to 200 ppm of NH3 was improved by 50% compared to that of the pure PANI sensor (12.99) and reached the ppb-level detection limit at 25 °C. Meanwhile, the response time and recovery time of the PCN (30) hybrid sensor were also obviously shortened compared to the pure PANI sensor. Furthermore, the PCN (30) hybrid sensor displayed excellent reproducibility, long-term reliability, and selectivity at room temperature. The improved sensing properties were mainly attributed to the optimizing effect of g-C3N4 nanosheets on the structure and morphology of the hybrid. The formation of the p–n junction and π–π conjugate structure enhanced the capability and efficiency of carrier transport.