CLAD-MODIFIED FIBER OPTIC AMMONIA GAS SENSOR WITH NANOCRYSTALLINE TITANIUM DIOXIDE AND CERIUM DOPED ZING OXIDE

摘要

The present invention relates to a clad modified fiber optic type gas detecting apparatus for selectively detecting ammonia gas amongst plurality of gases and method of detection thereof. The apparatus comprising of a light source means for introducing an optical beam into the fiber optic core, a sensing means for selectively sensing ammonia and a detector means for providing transmission properties of the optical fiber which represents ammonia concentration. The sensing means is a selective sensing means which comprises of an optical transmission medium which includes plurality of layers arranged around the fiber optic core. The first layer which is arranged around the core is a first passive cladding layer and forms the surface of the transmission medium. A second nano crystalline selective sensing layer is coated around the core of the optic fiber in a removed portion of the passive cladding layer. Any change in the optical properties of the modified cladding material due to the presence of ammonia gas changes the transmission properties of the optical fiber which represents ammonia concentration. Nanocrystalline TiO2, and nanocrystalline cerium doped zinc oxide (Ce-ZnO) have been explored as second nanocrystalline selective sensing layer, for improving gas sensing properties as nanocrystalline materials exhibit a greater surface activity.