Colorimetric Sensor for Fine Differentiation of Organic Solvents Based on Only One Kind of Polydiacetylene Coated on Polymer Optical Fiber

The hydrogen-bonding complexes of poly (4-vinylpyridine) and diacetylene derivatives 10, 12-tricosadiynoic acid are deposited outside of the side-polished optical fiber as part of the cladding. In the evanescent field of the optical fiber, the blue-to-red colorimetric transition can be monitored by the change of the propagating light in the fiber when the polydiacetylene (PDA) overlay is exposed to organic solvents. As the organic solvents have different diffusivities which cause different colorimetric transition in the evanescent field, when the coated fiber is put in different solvent atmospheres the change trends of optical intensity in the fiber are different accordingly. Using this kind of structure, the colorimetric differentiation of some organic solvents in the vapor state based on just one DA monomer is realized. Together with the remote measurement character of the fiber sensor, it has potential applied value in the future.