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Photonic Crystal Based Sensor for Organic Solvents and for Solvent-Water Mixtures
Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, 93040 Regensburg, Germany
* Author to whom correspondence should be addressed.
Received: 25 October 2012; in revised form: 28 November 2012 / Accepted: 5 December 2012 / Published: 12 December 2012
Abstract: Monodisperse polystyrene nanoparticles with a diameter of 173 nm were incorporated into a polydimethylsiloxane matrix where they display an iridescent color that can be attributed to the photonic crystal effect. The film is of violet color if placed in plain water, but turns to red in the presence of the non-polar solvent n-hexane. Several solvents were studied in some detail. We show that such films are capable of monitoring the water content of ethanol/water mixtures, where only 1% (v/v) of water leads to a shift of the peak wavelength of reflected light by 5 nm. The method also can be applied to determine, both visually and instrumentally, the fraction of methanol in ethanol/methanol mixtures. Here, a fraction of 1% of methanol (v/v) results in a wavelength shift of 2 nm. The reflected wavelength is not influenced by temperature changes nor impeded by photobleaching. The signal changes are fully reversible and response times are <1 s.
Keywords: photonic crystal; sensor; PDMS; solvent polarity; water sensor
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Fenzl, C.; Hirsch, T.; Wolfbeis, O.S. Photonic Crystal Based Sensor for Organic Solvents and for Solvent-Water Mixtures. Sensors 2012, 12, 16954-16963.
Fenzl C, Hirsch T, Wolfbeis OS. Photonic Crystal Based Sensor for Organic Solvents and for Solvent-Water Mixtures. Sensors. 2012; 12(12):16954-16963.
Fenzl, Christoph; Hirsch, Thomas; Wolfbeis, Otto S. 2012. "Photonic Crystal Based Sensor for Organic Solvents and for Solvent-Water Mixtures." Sensors 12, no. 12: 16954-16963.