CuO/rGO doped with silver nanoparticles for humidity sensing applications

Determination of the relative humidity in the surrounding environment is essential for numerous industrial and technological applications. In this work, we successfully prepared CuO-rGO doped with varied Ag concentrations (0-1.5 wt%). The XRD measurements demonstrated that the structures were successfully developed with an average crystallite size of 30-40 nm as reflected from the (111) plane, with a dominating cubic phase. The SEM morphological characteristics demonstrated that the cubic structure was Cu-based, whilst the sheet-like structure was attributable to 2D rGO. The cubic structure tended to lose its regular shape, while the size tended to be reduced as the Ag doping ratio increased. Elemental analysis was confirmed through EDX for CuO-rGO doped with 1.5 wt% Ag, reflecting 35, 13, 1.4, and 50.6 wt% of C, O, Ag, and Cu, respectively. Assessment of the antimicrobial assets of the nanostructures versus G^+ve (Staphylococcus), and G^-ve bacteria (Escherichia coli) presented the highest activity for CuO-rGO doped with 1 wt% Ag. The humidity sensing evaluations were revealed throughout a wide set of frequencies (50-10 kHz) and humidity levels (11-97% RH). The optimum frequency was optimized as 50 Hz. The acquired response and recovery times were 154, and 172 s, respectively, while the sensitivity was 2 × 10⁶ Ω per RH for CuO-rGO doped with 1.0 wt% Ag. Remarkably, the recovery time for CuO-rGO doped with 1.5 wt% Ag was 17 s. The sensor demonstrate decent repeatability for four cycles between 11% and 75% RH at a testing frequency of 50 Hz. The results nominate this structure as an affordable, low-cost, and applicable humidity sensor valid for nanotechnological and materials science routes.