High-Performance Hydrazine Gas Sensors Based on Electrohydrodynamic-Printed P3HT-SnO₂ Hybrid Films

Hydrazine (N₂H₄) is a highly toxic and strongly reducing compound extensively used in aerospace propulsion and industrial synthesis, necessitating its real-time detection essential for environmental and occupational safety. Here, an electrohydrodynamic printing (EHDP) strategy is reported to fabricate a uniform poly(3-hexylthiophene)-SnO₂ (P3HT-SnO₂) composite sensing film for room-temperature hydrazine sensing. Structural characterizations reveal homogeneous dispersion of ≈4 nm SnO₂ quantum dots (QDs) on the P3HT matrix and the formation of interface P-N heterojunctions. The P3HT-SnO₂ sensor delivers a remarkable response of 1550% toward 15 ppm N₂H₄, an ultralow detection limit of 500 ppb, excellent selectivity against common interfering gases (CO, H₂, CO₂, and C₂H₅OH), and long-term performance over 90 days. Compared with drop-cast films, the EHDP-printed devices exhibit superior uniformity, tunable thickness, and significantly enhanced response and recovery kinetics, arising from increased active sites, optimized morphology, and accelerated gas adsorption–desorption dynamics. Mechanistic investigations indicated that N₂H₄ molecules donate electrons, reducing hole density in P3HT and expanding the depletion region at the P3HT-SnO₂ interface, thereby amplifying the resistance change. These results establish EHDP-printed P3HT-SnO₂ hybrid films as a robust platform for highly sensitive, selective, and stable hydrazine detection at room temperature, offering a promising route toward advanced toxic hydrazine gas sensors.