Structural, optical, and gas sensing characterization of nanostructured MgS thin films prepared via spray pyrolysis technique for high-sensitivity CO2 detection

Magnesium sulfide (MgS) thin films were synthesized and developed via the spray pyrolysis technique for enhanced detection of CO₂ gas in ambient environments. The developed thin films demonstrated a high sensitivity of 82.13 % at an operational temperature of 70 °C of 500 ppm CO₂ gas concentration. Comprehensive electrical, structural, optical, and gas sensing characterizations were conducted using standard analytical tools. The electrical properties were evaluated using the half-bridge method. Structural analyses via X-ray diffraction (XRD) confirmed the formation of crystalline MgS films with preferred orientations and matched with JCPDS data No.01-075-0262. The crystallite size was found to be 25.54 nm. FESEM results of MgS thin films developed by the spray pyrolysis technique reveal nanostructured grains, porosity, and smooth surfaces, which are influenced by the spray process parameters. The optical characterizations were carried out using FTIR and UV–Vis spectroscopy. The functional group and bonds of MgS were analyzed using FTIR. The band gap was estimated using a Tauc plot and it was found to be 3.1 eV. Gas sensing performance was systematically investigated using a static gas sensing setup, demonstrating rapid response (∼8 s), recovery (∼53 s) times, and excellent selectivity towards CO₂ gas. The results indicate the potential of MgS thin films for practical applications in environmental monitoring and gas detection systems.