Ammonia sensing using a fibre optic long period grating with a porous nanostructured coating formed from silica nanospheres
S. Korposh, W. Batty, Cranfield University at Kitakyushu (Japan); S. Kodaira, S-W. Lee, The University of Kitakyushu (Japan); S. W. James, S. M. Topliss, R. P. Tatam, Cranfield University (United Kingdom)
The transmission spectrum of a fibre optic long period grating (LPG) coated with a porous multilayer coating of thickness of order 400 nm formed from silica nanospheres is shown to exhibit a strong sensitivity to the infusion of a functional, chemically sensitive material into the coating. Subsequently, the transmission spectrum of the LPG shows sensitivity to changes in the properties of the functional material when exposed to a particular chemical species in an aqueous solution. The operation of such a device as an ammonia sensor is demonstrated, exhibiting 1 ppm sensitivity. The sensing mechanisms are discussed.
