Molecular Packing Engineering Enables a High Performance ppb-Level Room-Temperature NO2 Sensor.

Nitrogen dioxide (NO2) is a representative air pollutant, and the development of sensors capable of accurate and stable ppb-level detection at room temperature remains highly desirable. Electrical sensors based on organic small molecules have attracted increasing interest due to their structural tunability, mechanical flexibility, facile integration, and suitability for in situ monitoring. However, despite extensive molecular design efforts, the dynamic evolution of nanostructures and the associated structure-sensitivity relationships remain insufficiently understood. Herein, the molecular spatial conformation is systematically regulated by introducing alkyl chains with different lengths into cyano-substituted distyrylbenzene (DSB) derivatives. Meanwhile, microcrystalline formation in the sensing films and the molecular packing lead to exposure of more surface-accessible functional groups, thereby enhancing the NO2 sensitivity. The optimized device achieves the lowest detection limit of 30 ppb. Notably, the humidity-enhanced sensing behavior is attributed to the synergistic interaction between NO2 and H2O. Furthermore, a wireless real-time vehicle exhaust monitoring system based on the flexible sensor demonstrates its promising potential for practical atmospheric environmental monitoring.