Modulation of Analytical Performance of a Bifunctional Optical Probe at the Micelle‐Water Interface: Selective Sensing of Histidine in Biological Fluid

Abstract

AbstractBifunctional bis(indolyl)methane (BIM) derivatives with free carboxylic acid groups have been synthesized for the detection of heavy metal pollutants in the aqueous medium. Unlike in water, compounds in the presence of anionic micelle, showed color change from red to yellow specifically in the presence of Cu2+ ions. The incorporation of ionic surfactants could selectively block one of the binding sites, thereby improved the selectivity. In addition, large local concentration of metal ions (Cu2+) at micelle‐water interface of anionic surfactant improved the sensitivity. Metal ion binding at carboxylic acid (donor site) end not only alter the charge transfer state of the molecules, but also modify the self‐assembly property of probe molecules in the aqueous medium. The sensitivity as well as selectivity of the probes towards Cu2+ was found to be dependent on the number of carboxylic acid units on the central aryl ring. Further, the in‐situ formed Cu2+‐complex was involved for the ppb level recognition of histidine, an amino acid essential for protein biosynthesis and enzymatic activities. Finally, the present system was involved in the analysis of residual Cu2+ contents in natural water samples and histidine in the human urine sample.