Graphene coated optical fiber tip sensor for nitrate sensing application

An optical fiber tip sensing probe coated with graphene is proposed for nitrate-sensing application. The sensor was coated with graphene using dip-casting method to detect nitrate at different concentrations ranging from 0 to 50 ppm. The graphene-coated fiber tip sensor was highly sensitive in detecting nitrate ion. When the concentration of the nitrate solution was dropped onto the sensing region, the reflected optical power decreased as the nitrate concentration increased. Without the graphene layer, the uncoated fiber tip sensor only had a sensitivity of 0.0076 dBm/ppm. However, the coated sensor's sensitivity was significantly enhanced to 0.0624 dBm/ppm, eight times higher than the uncoated fiber tip sensor, mainly due to the adsorption of nitrate on the graphene surface. This graphene-coated optical fiber tip sensor has a high potential to be used in nitrate-sensing applications