Development of sol–gel-based fiber optic nitrogen dioxide gas sensors

We report herein the development of sol–gel-based fiber optic sensors to monitor gaseous nitrogen dioxide based on two different indicating chemistry encapsulations. The first consists of the immobilization of a ruthenium complex, [Ru(bpy)3]Cl2, within a silica sol–gel matrix, while the second design is based on the co-immobilization of the dye Acridine orange and the Saltzman reagent encapsulated within a silica sol–gel matrix. The sensors are placed in a manifold test chamber and nitrogen dioxide gas at various concentrations is flowed into the chamber. A miniature optoelectronics package was developed to acquire data from the sensors. The nitrogen dioxide sensor encapsulating the [Ru(bpy)3]Cl2 demonstrates sensitivity in the hundreds parts per million range with reversibility while the nitrogen dioxide sensor utilizing the Acridine orange dye demonstrates sensitivity in the parts per million range; however, it is not reversible.