Ammonia gas sensing property of gadolinium oxide using fiber optic gas sensor

The design of fiber optic sensor is based on a cladding modification methodology. A fiber-optic chemical sensor is developed by replacing a certain portion of the original cladding with a chemically sensitive material, specifically, calcinated gadolinium oxide (Gd2O3).Both the light absorption co-efficient and refractive index change upon exposure to chemical vapours of volatile organic compounds (VOCs) such as ammonia (NH3), ethanol (CH3CH2OH), and methanol (CH3OH). The spectral characteristics of the sensor were studied for different concentrations ranging from 0-500 ppm. These changes induced the optical intensity modulation of the transmitted optical signal. During interaction between the sensing material and VOCs, the output intensity is taken into account to detect the toxic VOCs present in the environment. This was systematically investigated by X-ray diffractometer (XRD) and SEM. The XRD analysis indicated that the calcinated Gd2O3 was formed in cubic structure with the crystallite size of 13 nm. The Gd2O3 nanorods with thickness ranging from 80 to 120 nm were confirmed from SEM. The ammonia gas response of the Gd2O3 sensor is presented. A model is proposed for understanding the spectral intensity variations.