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

Three reversible ammonia (NH ₃ ) gas sensors were fabricated using tetra-α-(p-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 via 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 NH ₃ -sensing performance of the PcCo/rGO sensors was tuned by adjusting the substituent structure of PcCo. The enhanced NH ₃ -sensing performance may be attributed to synergistic effects between PcCo and rGO, e.g., stronger adsorption interactions between PcCo with an aminophenoxy substituent and NH ₃ , the high electrical conductivity of rGO, and fast charge transfer between PcCo and rGO. These are further confirmed via first-principle density functional theory (DFT) calculations and electrochemical impedance spectra (EIS) measurements.