In-situ laser reduced LrGO-SnO2 chemoresistive sensor for highly selective and room-temperature isoprene detection

Abstract Isoprene, a volatile organic compound in human breath, has emerged as a promising biomarker for non-invasive monitoring of hypoglycemia. However, its low concentration (ppb level) and demands for low energyconsuming constituents pose significant challenges for realtime detection. In this work, we present a room-temperature chemoresistive gas sensor based on a nanocomposite of laserreduced graphene oxide (LrGO) and tin oxide nanoparticles (SnO2 NPs), fabricated via a photolithography-free in-situ laser patterning technique. The LrGO-SnO2 sensing film was optimized through controlled nanomaterial dispersion and in-situ laser reduction, enabling the construction of interdigitated electrode structures directly on flexible Kapton substrates. The sensor exhibits a wide detection range (0.5-100 ppm), a low detection limit of 189 ppb, and a strong nonlinear calibration fit (R2 = 0.9903). It achieves a response time of 90 s and recovery time of 137 s at 3 ppm isoprene, along with excellent selectivity-demonstrating 3-10 times higher response to isoprene compared to other VOCs. Additionally, it shows robust environmental stability and long-term repeatability under ambient conditions. This work contributes a low-power, scalable sensing strategy with potential for wearable, non-invasive health monitoring.