Flexible gas sensor based on laser-induced graphene and cobalt phthalocyanine-MWCNTs composite for methanol detection at room temperature

Abstract Methanol, a toxic volatile compound, poses significant threats to human health and the environment. Traditional methanol sensors require high operating temperatures, exhibit poor selectivity, and have limited long-term stability, which restricts their application in portable methanol monitoring devices. This study proposes a flexible chemoresistive gas sensor based on laser-induced graphene (LIG) electrodes and a cobalt phthalocyanine (CoPc)- multi-walled carbon nanotubes (MWCNT) composite. Experimental results demonstrate that the sensor achieves an excellent sensitivity of 0.589 Ω/ppm and a low limit of detection of 165 ppb over a wide detection range of 10–1000 ppm, covering international methanol exposure limits. Moreover, the sensor exhibits high selectivity towards methanol in comparison to other interfering volatile organic compounds (e.g., ethanol, isopropanol, and acetone). Under 500 ppm methanol, the response time (τ45) is 5 s, the recovery time (τ85) is 108 s, and the hysteresis is only 2.77%. The synergistic effects of the three-dimensional porous structure of LIG, the high conductivity of MWCNT, and the electron transfer characteristics between CoPc and methanol molecules collectively optimize charge transport and gas adsorption efficiency, enabling the sensor to achieve excellent methanol sensing performance at room temperature. Additionally, it shows also outstanding long-term stability over 30 days, with a performance degradation rate of less than 4.25%. These attributes indicate that the LIG-CoPc/MWCNT sensor holds great potential in industrial safety and environmental monitoring applications while providing critical technological support for the development of high-performance, low-power methanol gas sensors.