Improvement in gas-sensing properties of TiO2 nanofiber sensor by UV irradiation

Abstract In this study, a TiO2 nanofiber sensor is made at different crystalline phases by the electro-spinning method. The Sol used for spinning nanofibers consisted of titanium tetraisopropoxide (C12H28O4Ti), acetic acid (CH3COOH), ethanol (C2H5OH) and polyvinylpyrrolidone (PVP). PVP was applied in the final solution at different weight ratios (9, 12, 19 and 26 wt%). Electro-spun fibers were placed on alumina ceramic with Pt interdigitated contacts. Then nanofibers were calcined at 300 to 900 C and analyzed by FESEM, XRD and spectrophotometry techniques. The sensor demonstrated the highest response in PVP with the concentration of 12 wt% and sintering temperature of 500 °C. The average diameter of the fibers was 80 nm. The response and recovery times were 12.3 and 22.5 s, respectively, for the responses of 1.8–10.1 at 25–200 ppm of hydrogen gas. However, under UV illumination of 360–380 nm wavelengths, the response increased to 18–96, and the response and recovery times were reduced to 2 and 6.9 s, respectively. Higher sintering temperature and PVP concentration increased the rutile phase percentage and stability of sensors. Obtained anatase phase percentages were approximately 100%, 75%, 25% and 0% for the samples calcined at 300, 500, 700 and 900 C, respectively. By UV irradiation, the response was enhanced 10-fold, reducing the response and recovery times by a factor of 3–6. Thenwe coated a thin layer of Au on the pure TiO2 nanofibers sample and tested its sensing performances. For CO the response of Au/TiO2/UV (390–410 nm) in comparison to the pure one under dark condition is increased by a factor of about 20. In addition, the operating temperature is lowered about 120 °C from 290 °C to 170 °C.