Enhanced CO₂ gas sensing at room temperature using Ag-plated Na-doped CuO thin films synthesized by successive ionic layer adsorption and reaction technique

In this study, we synthesized undoped, Zn-doped, and Na-doped CuO films using the Successive Ionic Layer Adsorption and Reaction (SILAR) method to enhance CO2 gas sensing capabilities. The characterization of the films revealed a monoclinic tenorite phase structure across all samples. The crystallite size was observed to decrease from 83.5 nm in pure CuO to 73.15 nm and 63.08 nm in Zn-doped and Na-doped CuO films, respectively. Notably, Na-doped CuO films exhibited a reduced band gap, increased specific surface area, enhanced surface roughness, and improved electrical conductivity compared to their counterparts. The gas sensing performance was assessed based on sensitivity, selectivity, recovery and response times, and the limit of detection for CO2. The Na-doped CuO films demonstrated superior sensitivity, with sensor responses at 3.3 %, 4.86 %, and 12.8 % for undoped, Zn-doped, and Na-doped films, respectively, at a CO2 flow rate of 100 SCCM. Further modification of the Na-doped CuO films with Ag plasmonics markedly increased the sensor response to 914.8 % under the same conditions at a standard room temperature of 30 degrees C. Additional evaluations of selectivity, consistency, repeatability, and both quantification and detection limits underscored the enhanced performance of the modified Na-doped CuO films, indicating their potential for efficient CO2 gas detection applications.