The metal island coated swelling polymer over mirror system (MICSPOMS): a new principle for measuring ionic strength

Abstract

We propose a new optical sensor principle for cases where the sensor/analyte reaction results in the change of non-spectroscopic parameters and demonstrate this for the ionic strength-dependent swelling of special polymers. The sensor material is part of an optical thin-film system which transforms the variation in volume into spectral information. The metal island coated swelling polymer over mirror system (MICSPOMS) is a special kind of optical reflection interference filter, consisting of a metal mirror, followed by a thin layer of an optical transparent interlayer, represented by the ionic strength sensitive polymer. Therefore, by monitoring the slope of the narrow bandwidth reflection minimum of this layer system a high sensitivity for the analyte, which causes the swelling, is obtained. To obtain swellability and attachment to the metal surface as well as photostructuring properties a crosslinked polyvinylpyrrolidone photopolymer was developed.