Jing Jin

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.

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.