How does an ion-selective optical fiber work?
An ion-selective optical fiber is an optical fiber with a coating that is sensitive to a specific ion, making it possible to determine concentrations of that ion in a given solution. This polymer fiber (optode) is made by replacing the standard cladding with a membrane composed of a polymer matrix, an ionophore specific to the target ion, and a dye indicator. The color (absorption) of the dye indicator depends on the presence of the specific ion bonded to the ionophore in the membrane. It is the variation of the spectrum of the light signal transmitted through the fiber that allows us to determine the amount of ions present in the membrane. When the ionic equilibrium is reached, a simple calculation based on the dye concentration in the membrane provides the concentration of ions in the solution into which the fiber has been placed.
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We have developed ion-selective optical fibers for positive ions like calcium, sodium, and potassium and can rapidly produce ion-selective fibers for any ion for which there exists a specific ionophore. We are presently working on a pH sensor and, in the medium term, we are also planning to offer units for negative ions and some neutral analytes.
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