Chemical sensors may be designed with selective response to cations using various materials within thin organic liquid or polymeric films. However, the design of selective analogous anion sensors has been far more difficult due to the lack of suitable lipophilic host molecules that exhibit anion-specific interaction. Further, film type sensors with selective response to fluoride, in particular, may be difficult to achieve because of the negative Gibbs free energy of hydration of this anion relative to others. A variety of metal-ligand complexes have been examined as potential film ionophores to prepare useful anion sensors. However, the sensitivity is not adequate for certain applications and current fluoride ion-selective electrode based in LaF3 single crystal is expensive. It would be desirable to provide a film and sensor having relatively high selectivity for fluoride ions.
Researchers at the University of Michigan have developed lipophilic aluminum complexes as highly selective ionophores for fluoride ion. Aluminum complexes based optical films sensitive to fluoride ions were incorporated in plasticized polymer films. The film includes an organic matrix having a lipophilic aluminum compound incorporated therein. The lipophilic aluminum compound is adapted to selectively bind with fluoride ions. The optical films showed high selectivity and sensitivity toward fluoride ion compared to other anions as well as good reversibility in optical response properties. The film may be incorporated into an optical sensor and/or an electrochemical sensor configuration for the selective determination of fluoride in a wide range of samples.
Applications and Advantages
- In fluoride sensors to determine fluoride-nl-levels in a variety of real environmental-nl-and industrial samples
- Optical sensor to analysis gaseous (HF)-nl-or anionic species
- High fluoride ion selectivity