New ketocyanine-based fluorescent optodes for the development of integrated waveguide sensors

Twenty ketocyanine dyes are evaluated as potential pH fluoroionophores to be used in the development of new integrated waveguide fluorescence optodes (IWFOs). Its fluorescence characterization, as well as the pH response is first undertaken in ethanolic solution and then in plasticized PVC membranes with a conventional spectrofluorimeter. Analytical parameters such as basicity, reversibility, leaching and calibration curves are determined in both media and finally, photostability is also measured. Besides, some photophysical fluorescent parameters, such as the emission wavelength, are evaluated for both species, the acidic and the basic form, and quantum yields are calculated in ethanolic solution. Ketocyanine dyes have demonstrated their suitability for being used as acidochromic fluoroionophores in bulk optodes for the development of new IWFOs. They exhibit high fluorescence intensities in the far-visible region, an adequate photostability and an optimum pH response.