High‐Performance Hydrazine Gas Sensors Based on Electrohydrodynamic‐Printed P3HT‐SnO ₂ Hybrid Films

Hydrazine (N 2 H 4 ) 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)‐SnO 2 (P3HT‐SnO 2 ) composite sensing film for room‐temperature hydrazine sensing. Structural characterizations reveal homogeneous dispersion of ≈4 nm SnO 2 quantum dots (QDs) on the P3HT matrix and the formation of interface P‐N heterojunctions. The P3HT‐SnO 2 sensor delivers a remarkable response of 1550% toward 15 ppm N 2 H 4 , an ultralow detection limit of 500 ppb, excellent selectivity against common interfering gases (CO, H 2 , CO 2 , and C 2 H 5 OH), 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 N 2 H 4 molecules donate electrons, reducing hole density in P3HT and expanding the depletion region at the P3HT‐SnO 2 interface, thereby amplifying the resistance change. These results establish EHDP‐printed P3HT‐SnO 2 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.