Highly Sensitive Surface Acoustic Wave Sensors for Ammonia Gas Detection at Room Temperature Using Gold Nanoparticles-Cuprous Oxide/Reduced Graphene Oxide/Polypyrrole Hybrid Nanocomposite Film.

Gold nanoparticles-cuprous oxide/reduced graphene oxide/polypyrrole (AuNPs-CuO/rGO/PPy) hybrid nanocomposites were synthesized for surface acoustic wave (SAW) sensors, achieving high sensitivity (2 Hz/ppb), selectivity, and fast response (~2 min) at room temperature. The films, deposited via spin-coating, were characterized by SEM, EDS, and XRD, revealing a rough, wrinkled morphology beneficial for gas adsorption. The sensor showed significant frequency shifts to NH, enhanced by AuNPs, CuO, rGO, and PPy. It had a 6.4-fold stronger response to NH compared to CO, H, and CO, confirming excellent selectivity. The linear detection range was 12-1000 ppb, with a limit of detection (LOD) of 8 ppb. Humidity affected performance, causing negative frequency shifts, and sensitivity declined after 30 days due to resistivity changes. Despite this, the sensor demonstrated excellent NH selectivity and stability across multiple cycles. In simulated breath tests, it distinguished between healthy and patient-like samples, highlighting its potential as a reliable, non-invasive diagnostic tool.