Reversible NO(2) Optical Fiber Chemical Sensor Based on LuPc(2) Using Simultaneous Transmission of UV and Visible Light

In this paper, an NO(2) optical fiber sensor is presented for pollution monitoring in road traffic applications. This sensor exploits the simultaneous transmission of visible light, as a measurement signal, and UV light, for the recovery of the NO(2) sensitive materials. The sensor is based on a multimode fiber tip coated with a thin film of lutetium bisphthalocyanine (LuPc(2)). The simultaneous injection of UV light through the fiber is an improvement on the previously developed NO(2) sensors and allows the simplification of the sensor head, rendering the external UV illumination of the film unnecessary. Coatings of different thicknesses were deposited on the optical fiber tips and the best performance was obtained for a 15 nm deposited thickness, with a sensitivity of 5.02 mV/ppm and a resolution of 0.2 ppb in the range 0–5 ppm. The response and recovery times are not dependent on thickness, meaning that NO(2) does not diffuse completely in the films.