Elucidating the absorption and performance of acetone gas sensor detection using ITO coated D-shape optical fiber at visible region

Acetone detection is essential in industrial, pharmaceutical, and environmental applications due to its toxicity at elevated concentrations. This study reports the fabrication and optical analysis of a D-shaped fiber optic sensor coated with indium tin oxide (ITO, 10 nm), gold (Au, 40 nm), and bilayer Au: ITO (40:10 nm) thin films for room-temperature acetone sensing. The D-shaped geometry was produced via controlled mechanical polishing, while thin films were deposited using high-vacuum electron-beam evaporation. The sensing mechanism is governed by evanescent-field absorption and wavelength-resolved spectral modulation induced by acetone adsorption. Under static testing conditions across 0–870 ppm, the ITO coating achieved a sensitivity of 16 at 350 ppm (LOD = 66 ppm), Au exhibited 14 at 350 ppm (LOD = 75 ppm), and Au: ITO demonstrated 10.2 at 700 ppm (LOD = 205.9 ppm). The bilayer structure enhanced spectral stability at higher gas concentrations. The proposed low-cost, compact, and non-electrical configuration demonstrates strong potential for selective, real-time acetone vapor monitoring in industrial and environmental settings.