A colorimetric and fluorimetric three-input inverted enabled or logic array by self-assembly of a rhodamine probe in micelles

Abstract

A rhodamine B derivative appended with a hexyl chain has been synthesized as a colorimetric and fluorimetric probe and studied in three different micelles, sodium dodecyl sulfate (SDS), Triton X-100, and cetyltrimethylammonium chloride (CTAC) in 1:4 (v/v) methanol/water solutions. UV/vis and fluorescence spectroscopic studies suggest that the hydrophobic hexyl chain anchors the probe in the vicinity of the water/membrane interface rather than in the bulk solution. A significant pKa shift of 4.5 units is observed in CTAC and Triton X-100 relative to aqueous methanol solution, whereas no significant difference is observed in SDS. In CTAC and basic solution a nine-fold decrease in the fluorescence intensity and absorbance are observed. These observations are rationalized by a spiro-ring-closing mechanism via lactam formation, which disrupts the conjugated xanthene chromophore. A three-input inverted enabled OR (iEnOR) logic circuit is demonstrated in absorbance and fluorescence mode with CTAC, Triton X-100 and alkali as the inputs via supramolecular assembly