Solid state supramolecular optical sensors

We describe examples for an optical gas sensor (oxygen) and an optical ion sensor (pH), and discuss how the existing need for complete mass transfer in solid-state optical sensors determines the choice of the appropriate polymer. Examples are given for biomedical instrumentation based on mass-fabricated optical sensors for oxygen, carbon dioxide and pH. We also show that specific recognition of ions, particularly of the clinically important alkali ions, is much more difficult in solid-state sensors. We discuss existing schemes for ions and demonstrate that none of them satisfies the need for rapid, pH-independent determination of ions in whole blood at room temperature and without addition of any reagent. The photo-induced electron transfer (PET) effect represents an attractive alternative to the use of fluoro-ionophores, but it is shown that PET - while being extremely useful when studied in solution - not necessarily does not occur in solid-state sensor matrices to the extent it does in fluid solution, a fact that is explained mainly in terms of rotational restriction.