Annealing-induced enhancement of TiO 2-ZnO nanocomposites for high-performance room-temperature air pollutant detection in fiber optic sensors

Abstract

Fiber optic sensors, promising for their compactness and remote sensing abilities, are explored in this study as a platform for detecting volatile organic compounds (VOCs) using nanocrystalline metal oxide composites like TiO 2 -doped ZnO. Hydrothermally synthesized (S1 sample)and annealed composites (500 degrees C (S2 sample) and 1200 degrees C (S3 sample) annealing) were investigated for their gas-sensing properties towards inorganic gas like ammonia and VOCs like acetone, and isopropyl alcohol. Remarkably, annealing at 1200 degrees C yielded S3 sample with higher response (7.5 %) towards ammonia at room temperature for 500 ppm concentration. This superior performance is attributed to increased surface area, narrowed bandgap, and faster response/recovery times (18/ 15 s) compared to other samples. The proposed sensing mechanism involves the adsorption and desorption of oxygen molecules on the sensor surface, altering refractive index and light scattering, ultimately modulating the transmitted light intensity. X-ray diffraction, SEM imaging, and UV - Vis absorption techniques confirmed the structure and morphology of the nanocomposites.