Single-Step Synthesis of Laser-Induced Graphene (LIG) Wood Impregnated SnO 2 –NiO for Room Temperature Methane Gas Sensor

The development of low-power, environmentally friendly gas sensors is critical for next-generation safety and environmental monitoring, yet it is constrained by energy-intensive operation and unsustainable fabrication processes. We present a one-step laser-induced method to fabricate a wood-based resistive methane sensor, where laser irradiation directly converts a natural wood precursor into a 3D conductive laser-induced graphene (LIG) network decorated with in situ-formed SnO2–NiO heterojunction nanoparticles. This integrated SnO2–NiO/LIG nanocomposite features a hierarchical, porous, polycrystalline structure, as characterized by SEM, TEM, Raman, XRD, and XPS. The sensor operates at ambient temperature, has a response time of 50 s, achieves a low theoretical detection limit of 7 ppm, and maintains robust performance under varying humidity of ≤70%. The sensing superiority is attributed to synergistic effects at the n-SnO2/p-NiO heterointerface within the conductive graphene matrix, which facilitates efficient charge separation and transfer upon gas exposure, validated by density functional theory (DFT) calculations. This direct laser-engraving, solvent free approach using wood establishes a new paradigm for designing sustainable, cost-effective, and eco-friendly, high-performance nanoarchitecture gas sensors.