High Sensitive Ambipolar Response towards Oxidizing NO2 and Reducing NH3 Based on Bis(phthalocyaninato) Europium Semiconductors

Abstract

AbstractHigh sensitive chemical sensors towards NO2 and NH3 based on the self‐assembled nanostructures of the heteroleptic and homoleptic bis(phthalocyaninato) europium complexes with octanaphthoxy phthalocyaninato ligands named Eu(Pc)[Pc(ONh)8] (1) and Eu[Pc(ONh)8]2 (2) [Pc=unsubstituted phthalocyaninate; Pc(ONh)8=2,3,9,10,16,17,23,24‐octanaphthoxy phthalocyaninate] have been developed. The good conductivity, high crystallinity and large specific surface area for the self‐assemblies of 1 render it excellent sensing property for either electron‐accepting gas NO2 in 50–250 ppb range or electron‐donating gas NH3 in 2.5–12.5 ppm range due to the optimized molecular packing in the uniform‐sized nanoparticles depending on the effective intermolecular interaction between double‐decker molecules, among the best results of phthalocyanine‐based chemical sensors for detection of NO2 and NH3 at room temperature. Interestingly, self‐assemblies of 1 exhibited n‐type response to NO2 and p‐type response to NH3, which is the first example of ambipolar charge‐transporting gas sensors fabricated from single‐component organic semiconductors. However, the self‐assemblies of 2 with sixteen bulky naphthoxy groups at the periphery of two Pc rings only present an n‐type response to strong oxidant gas NO2 in a relatively high concentration of 0.5–1.5 ppm, while are insensitive to weak reducing gas NH3 due to the existence of great steric hindrance from bulky naphthoxy groups and more traps and/or defects in self‐assemblies.