Low-temperature detection of acetone gas using ZnO-TiO2 nanorod on tapered multimode fiber decorated with Au-Pd thin films

•Novel acetone gas optical sensor using ZnO-TiO2 nanorod on tapered multimode fiber.•Present the influence of titanium dioxide (TiO2) as a catalyst to the zinc oxide (ZnO) nanorods.•Low-temperature detection of acetone gas at 87 °C for the acetone concentrations of 1000, 5000 and 10,000 ppm.•Notable output intensity responses were observed for ZnO-TiO2 nanorods decorated with Au-Pd thin films (ZTNAP). This paper presents the influence of titanium dioxide (TiO2) as a catalyst to the zinc oxide (ZnO) nanorods coated on the tapered MMF fiber utilized as a sensing layer for the detection of acetone gas at low temperatures. To enhance the sensitivity of the sensor ZnO-TiO2 nanorods were decorated with Au-Pd film. Hydrothermal method was used to synthesize the ZnO nanorods while TiO2 powder was incorporated by using a simple doping procedure during fabrication. The decoration of the Au-Pd thin films is integrated with the ZnO-TiO2 by using DC sputtering method. The ZnO doped with 15 mM TiO2 shows a strong and significant peak based on XRD analysis which can be indexed to the hexagonal phase of ZnO. A few globular structures of TiO2 were randomly distributed as observed by the SEM image. Four different fiber sensing layers were prepared with respect to 10 mM ZnO precursor; ZnO nanorods (ZN), ZnO nanorods decorated with Au-Pd thin films (ZNAP), ZnO-15 mM TiO2 nanorods (ZTN) and ZnO-15 mM TiO2 nanorods decorated with Au-Pd thin films (ZTNAP). The spectrometry setup was used to measure the response of the sensor toward different concentrations of acetone gas in terms of intensity with respect to its wavelength. Notable output intensity responses were observed for ZTNAP in terms of sensitivity and standard deviation towards various acetone concentrations while the repeatability curve showed a high response of acetone gas at 10,000 ppm. All experiments were performed at the low temperature of 87 °C.