Infrared optical sensors for water quality monitoring.

In-situ monitoring of water quality with particular emphasis on organic pollutants is a global priority topic in water analysis. Recent developments in optical sensor technology provide advanced analytical tools for continuous assessment of pollution levels in the liquid phase and in the gas phase. Infrared sensing schemes are among the most promising concepts due to inherent molecular specificity provided by absorption patterns of fundamental molecular vibrations of organic molecules. The advent of mid-infrared transparent optical fibers and waveguides, appropriate light source technology, such as quantum cascade lasers, and the potential for the development of highly integrated analytical devices based on microfabrication technology substantiates the trend towards spectroscopic sensing techniques. Chemical modification of the waveguide surface leads to enhanced analyte recognition based on tunable properties of enrichment or (bio)chemical recognition layers. Discussion of fundamental sensing technology is complemented by recent examples, highlighting the state-of-the-art in this dynamic research field.