High-selective room-temperature NO2 sensors based on a coumarin-substituted tris(phthalocyaninato) europium

A novel coumarin-substituted phthalocyaninato triple-decker complex, Eu-2[Pc(Cou)(4)](3) is designed and synthesized successfully. Introduction of the coumarin substituents onto the periphery of a phthalocyanine ring in the sandwich-type phthalocyaninato triple-decker not only increased the solubility and improved the film-forming ability, but also importantly ensured the suitable HOMO and LUMO energy levels. The solution-processed thin film of the Eu-2[Pc(Cou)(4)](3) was prepared by a simple and low-cost quasi-Langmuir-Shafer (QLS) method and applied as the gas sensor for the detection of NO2. Importantly, within the dynamic exposure period of 1 min, balanced, stable, a reproducible n-type response to electron-accepting gas NO2 in the range of 4-35 ppm, was revealed, based on the QLS film of Eu-2[Pc(Cou)(4)](3) complex at room temperature, dependant on the optimized molecular packing in J-aggregation mode with a large specific surface area and good film conductivity.