Plasmonic sensor for on-site detection of diclofenac molecules

The monitoring of water treatment plants concerning the concentration of noxious organic molecules is a pressing issue as more and more species are not removed during the treatment process. However, especially the on-site monitoring of molecules present in low concentrations (µg/L range) is currently not possible due to the lack of suitable measurement systems. Here we report on a robust and cost-effective approach for a chemical sensor which perspectively may be used directly at a water treatment plant. In our study we demonstrate the capabilities of the sensor by detecting diclofenac molecules as guiding substance for water quality assessment. A nanostructured, plasmonically active metal surface is surface-functionalized with diclofenac molecules and used as optical transducer in a simple transmittance setup. In an inverse immunoassay, binding events between anti-diclofenac antibodies (preincubated with diclofenac molecules) and the sensor surface are detected optically. We demonstrate a measurement range between 1 to 10 µg/L diclofenac concentration and at least 30fold regeneration of the sensor surface.