Synergistic g-C₃N₄@SnO₂ nano heterostructures and their application for enhanced humidity sensing

We report g-C₃N₄@SnO₂ nanocomposites as efficient humidity-sensing materials. SnO₂ nanoparticles synthesized via a facile solvothermal route were coupled in situ with g-C₃N₄ sheets through an economic solid-state process. XRD, FTIR, and XPS confirmed the tetragonal SnO₂ phase and successful composite formation, while FESEM and FETEM showed 20-50 nm SnO₂ nanoparticles anchored on g-C₃N₄. The composites exhibited a red-shifted optical absorption edge and suppressed photoluminescence, indicating enhanced charge separation. The sensors, fabricated by screen printing, exhibited stable operation in the 20-80% RH range. Humidity-sensing studies revealed outstanding performance for the 15 wt% g-C₃N₄@SnO₂ composite, with a sensitivity of 20.2 Ω/%RH as well as rapid response (25 s) and recovery (45 s) times. These results establish g-C₃N₄@SnO₂ as a promising platform for next-generation, ultrasensitive and fast-response humidity sensors.