Heterostructural Cyano-Functionalized Nanofilm Sensors via Interfacially Confined Dynamic Condensation toward High-Performance Hydrazine Vapor Detection.

Sensitive and selective detection of hydrazine (N2H4) remains a significant challenge for practical gas-phase monitoring. Herein, a functional nanofilm was prepared via an interfacially confined condensation strategy, using tetraphenylaldehyde (TFPE) and acylhydrazide derivatives as the building blocks. Incorporating electron-withdrawing cyano moieties into the acylhydrazone backbone enables the simultaneous formation of both dynamic C═N bonds and conjugated C═C bonds within a single conjugated framework. The designed asymmetric building block, a 1,4-phenylene linker bearing an acylhydrazide and a cyanomethyl group at the para positions, effectively modulates π-electron delocalization and creates cyano-enriched N2H4-reactive sites in the conjugated donor-acceptor (D-A) system, thereby promoting intramolecular charge transfer (ICT) and producing a large Stokes shift. These structural features also significantly influence the fluorescence turn-off sensing of the obtained nanofilms for gaseous N2H4. Performance screening identifies the heterostructural TFPE-CN nanofilm as the optimal candidate, featuring a free-standing, defect-free morphology, a favorable photoluminescence quantum yield of 30.8%, and exceptional stability. Integrated into a home-built portable sensing platform, the TFPE-CN nanofilm enables real-time, in situ detection of N2H4 vapor, delivering ultrahigh sensitivity (detection limit ≈ 130 ppt), rapid response (<11 s), excellent selectivity, and robust stability. This work offers an asymmetric molecular engineering strategy for fabricating interfacial nanofilms and lays a foundation for developing high-performance and portable sensing platforms for N2H4 vapor.