Supramolecular Assembly Induced Emission of Thiazole Orange with Sulfobutylether β-cyclodextrin: A Stimuli-Responsive Fluorescence Sensor for Tyramine

Modulation and control of stimuli responsive features of molecular assemblies in organized assemblies/cavitand macrocycles have received immense attention in many areas. In this study, we have established the formation of a discrete molecular assembly of thiazole orange (TO) dyes at the portals of the sulfobutylether beta-cyclodextrin (SBE7 beta CD) macrocycle leading to the evolution of a strong and distinct emission band from aggregated TO. The supramolecular assembly promoted portal aggregation of TO in its 1 : 4 (SBE7 beta CD : TO) composition, characterized by absorption, fluorescence, circular dichroism, ITC and H-1 NMR measurements, was probed to be selectively responsive to tyramine among other biogenic amines/neurotransmitters. For the first time, the different extent of emission quenching of SBE7 beta CD : TO assembly in the presence of biogenic amines/neurotransmitters is translated to achieve a selective on-off fluorescence sensor for the detection of tyramine against other neurotransmitters with a limit-of-detection (LOD) as low as similar to 575 nM (79 ppb). The emission features of the assembly with changes in temperature is found to be highly reproducible even after several temperature cycles and is promising to design an optical supramolecular thermometer in the ambient temperature range.