Traditional methane sensors based on metal oxide semiconductors typically require high operating temperatures (200–400 °C), which not only leads to high power consumption but also often results in detection limits that struggle to fall below 5 ppm. To achieve room-temperature operation with lower detection limit, this work proposed a surface acoustic wave (SAW) methane sensor using monolayer graphene oxide (GO) film. The GO material was prepared by a modified Hummers method combined with liquid-phase exfoliation and characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The sensor was constructed by drop-casting the GO dispersion onto the delay line region of a Y-cut quartz SAW device. Results showed that the GO sensor exhibited a low detection limit of 1 ppm and a sensitivity of 0.046 mV/ppm in the range of 100–1000 ppm, which was 2.2 times higher than that of multilayer graphite (0.021 mV/ppm). The response and recovery times for 500 ppm methane were 16.7 s and 66.4 s, respectively. Good repeatability and selectivity were also demonstrated. This work presents a simple and effective approach for room-temperature methane detection using monolayer GO on SAW devices.

The detection of nitrogen dioxide (NO2) at trace levels remains challenging, particularly under ambient conditions where selectivity and rapid response are critical. Existing room-temperature sensors often suffer from slow kinetics and inadequate gas discrimination. To address the need for room-temperature operation, we developed a surface acoustic wave (SAW) sensor functionalized with a platinum nanoclusters/graphene oxide (Pt-NC/GO) film. The ultra-small platinum nanoclusters (~ 2.4 nm) are uniformly dispersed on GO, enhancing both adsorption and charge transfer. The SAW platform then transduces these interactions into measurable signal variations via its acousto-electric coupling and mass loading effect. The optimized sensor exhibits a sensitivity of 45.4 mV/ppm and a low experimentally measured minimum detectable concentration of 0.02 ppm (20 ppb) and a theoretical limit of detection of 6.6 ppb calculated via the 3σ/k method, outperforming pristine GO (10.7 mV/ppm) and Pt nanoparticles/GO (Pt-NP/GO, 16.1 mV/ppm) references. It also achieves fast response/recovery (50.2/104.0 s) and excellent selectivity against common interferents (H2, NH3, CH4). Additionally, the sensor maintains stable operation over 30 days, with less than 10% signal degradation. The superior performance is attributed to the large surface-to-volume ratio and high density of active sites provided by the platinum nanoclusters, which are crucial for enhancing gas interaction and signal transduction. This work provides new insights into noble-metal-modified two-dimensional materials for environmental monitoring.