Isolating metallophthalocyanine sites into graphene-supported microporous polyaniline enables highly efficient sensing of ammonia

Abstract

Although metallophthalocyanines (MPcs) have great potential in gas sensing, the strong π–π interaction between MPc molecules severely impairs the accessibility of the highly active central metal atoms, thus leading to unsatisfactory sensing performance. Herein, we overcome the inherent shortcomings of MPcs themselves by isolating them into reduced graphene oxide (RGO)-supported microporous polyaniline (PANI). The unique microporous structure of PANI enables the full exposure of active sites of tetra-β-sulfophthalocyanine cobalt(II) (CoTsPc) and unimpeded pathways for NH₃ diffusion. The structural conversion of PANI after exposure to NH₃ contributes to the improvement in the hybrid's NH₃-sensing. Moreover, RGO scaffolds can endow the hybrid with a large surface area and rapid electron transfer. Thus, due to the synergistic advantage of CoTsPc, PANI and RGO, the obtained RGO@PANI–CoTsPc-2 sensor displays an excellent room-temperature NH₃-sensing performance, including a high response (139.3% at 50 ppm NH₃), a fast response rate (8.0 s at 50 ppm NH₃), and a low detection limit (14 ppb) as well as remarkable stability over 30 days. The approach proposed in this work is potentially important not only to provide a demonstration for the design of an efficient NH₃-sensing material but also to give an idea for enhancing the application value of MPcs.