High sensitivity low-temperature ethanol and acetone gas sensors based on silver/titanium oxide decorated laser-induced graphene

The increasing environmental and safety concerns necessitate the development of advanced gas sensors capable of effectively identifying volatile and hazardous organic substances. Different sensors have been utilized to detect volatile organic compounds (VOCs). In this study, we report on the successful design of chemiresistive sensors based on porous laser-induced graphene (LIG) to effectively detect VOCs, including acetone and ethanol. Flexible 3D porous LIG has been produced using femtosecond laser texturing of polyimide tape. The 3D porous LIG primarily consists of multilayer graphene sheets comprising two or more monolayers. To enhance the sensors' capabilities, we created LIG-based heterojunction devices by decorating the LIG with Ag and TiOx (x <= 2) nanoparticles (NPs) using femtosecond pulsed laser deposition. Our experiments show that the sensitivity of LIG sensors increases when they are decorated with Ag and TiOx NPs. Among these, the LIG devices decorated with Ag NPs show the highest sensitivity and response compared to others. The sensor is reversibly responsive at ambient temperature towards the target VOCs in concentrations below 3000 ppm. Additionally, we introduce a mechanism to explain our findings. This mechanism relies on the distinction in the work function and energy level alignment linked to the interactions between adsorbates and adsorbents. The improved sensitivity of the Ag NPs-decorated porous LIG sensor is attributed to the favourable work function of Ag and the abundant availability of adsorption sites.