Induced ion-pair formation/ de-aggregation of rhodamine B octadecyl ester for anion optical sensing: Towards ibuprofen selective optical sensors.

A novel approach is explored to result in anion selective nanostructural optodes, that do not require the presence of selective ionophore. The sensing principle proposed is based on interactions of polarity sensitive dye with anions, leading to change of the chromophore group environment, resulting in increase of emission for increase of analyte concentration. To induce interactions of the analyte with the dye precise matching of properties of analyte and receptor is required. It is shown that the careful balancing of composition of nanostructural probes allows fine tuning of linear response range to cover lower concentration range. The model analyte studied was ibuprofen, due to its clinical and environmental relevance, lack of ionophore. As model probes rhodamine B octadecyl ester based nanostructures were prepared and applied. For optimized system turn-on responses were obtained for ibuprofen concentration change from 10-4.3 M to 10-2 M, with no effect of other anti-inflammatory drugs such as naproxen or salicylate.