The effects of amino substituents on the enhanced ammonia sensing performance of PcCo/rGO hybrids

Abstract

Three reversible ammonia (NH₃) gas sensors were fabricated using tetra-α-(<i>p</i>-aminobenzyloxy)phthalocyanine cobalt (ABOPcCo), tetra-α-aminophthalocyanine cobalt (APcCo) and substituent-free phthalocyanine cobalt (FPcCo) functionalized reduced graphene oxide (rGO), with cost-efficient, highly sensitive and stable sensing performance. These hybrid materials were prepared <i>via</i> a facile physical solution mixing self-assembly reaction with rGO and PcCo solutions. The obtained PcCo/rGO hybrid sensors exhibit excellent sensing performance; especially the ABOPcCo/rGO sensor, whose response is about 23.3% (50 ppm), with a limit of detection as low as 78 ppb, and response and recovery times about as fast as 225 s and 250 s. The performance of the PcCo/rGO hybrid sensors can be optimized by adjusting the concentrations of the PcCo/rGO aqueous dispersions. More importantly, the NH₃-sensing performance of the PcCo/rGO sensors was tuned by adjusting the substituent structure of PcCo. The enhanced NH₃-sensing performance may be attributed to synergistic effects between PcCo and rGO, <i>e.g.</i>, stronger adsorption interactions between PcCo with an aminophenoxy substituent and NH₃, the high electrical conductivity of rGO, and fast charge transfer between PcCo and rGO. These are further confirmed <i>via</i> first-principle density functional theory (DFT) calculations and electrochemical impedance spectra (EIS) measurements.