Improving Room Temperature Formaldehyde Sensitivity with Samarium-Doped Titanium Dioxide

Samarium (Sm)-doped titanium dioxide (TiO₂) thin films were synthesized using the spray pyrolysis technique at 400 °C, with Sm doping concentrations of 0, 2, 4, and 6 Wt% to enhance structural, optical, morphological, and gas-sensing properties. The films, deposited on ultrasonically cleaned glass substrates, were characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy (AFM), and UV–vis spectroscopy. Structural analysis revealed improved crystallinity and uniform surface morphology with Sm doping, while AFM indicated increased surface roughness, promoting gas adsorption. UV–vis analysis showed a reduced energy bandgap, enhancing visible light absorption and gas-sensing performance. Gas sensing evaluations demonstrated high sensitivity to formaldehyde, with notable selectivity over ethanol, toluene, and xylene at room conditions. The 6 Wt% Sm-doped TiO₂ film exhibited the highest response (17.4), with a detection limit of 5 ppm, and fast response (23 s) and recovery (27 s) times. These properties underline the potential of Sm-doped TiO₂ films for efficient room-temperature gas sensors. Their enhanced sensitivity, selectivity, and stability suggest promising applications in environmental monitoring and air quality management, particularly for formaldehyde detection and volatile organic compound discrimination.