Abstract
Methane (CH 4 ) and carbon monoxide (CO) are key gases associated with combustion processes, fire hazards, and fuel leakage events, making their early detection at room temperature critically important for fire safety and low-power monitoring systems. In the current study, a PANI/Co 3 O 4 core–shell nanocomposite was developed and investigated as a chemiresistive sensing material for room-temperature detection of CO and CH 4 . Cobalt oxide nanoparticles were synthesized by solution combustion synthesis (SCS), providing a defect-rich, porous Co 3 O 4 with enhanced redox activity, and subsequently integrated into a conducting polyaniline matrix through polymerization. Structural and spectroscopic characterization (SEM/EDS, XRD, BET, FTIR) confirmed the formation of phase-pure spinel Co 3 O 4 and a doped PANI (emeraldine salt) shell, resulting in a porous core–shell architecture favorable for gas diffusion and interfacial charge transfer. The PANI/Co 3 O 4 nanocomposite exhibited a measurable and reversible decrease in resistance upon exposure to reducing gases at room temperature, with initial responses of 8.73% toward 500 ppm CH 4 and 7.28% toward 500 ppm CO. The observed sensing behavior can be explained by the synergistic interplay between oxygen activation on Co 3 O 4 via the reversible Co 3+ /Co 2+ redox couple, modulation of the protonation–redox equilibrium of polyaniline, and efficient polaron/bipolaron-mediated charge transport within the conducting polymer shell. The results demonstrate that the use of SCS as a targeted approach for Co 3 O 4 preparation enables effective room-temperature gas sensing without external thermal activation, highlighting the potential of PANI/Co 3 O 4 nanocomposites for low-power fire-related gas monitoring applications.