Role of a cationic surfactant in mediating interaction of flavonoids with 3-mercaptopropanoic acid capped CdTe quantum dots (3MPA-CdTe QDs)

Flavonoids (biologically relevant hydroxyphenols) are natural antioxidants. Analytical sensing of flavonoids using quantum dots (QDs) is a result of the electron-withdrawing properties of carbonyl and hydroxyl groups in flavonoid structure that promotes effective photoluminescence quenching of QDs. In this article, the influence of a cationic surfactant organized media on interactions between five flavonoids (i.e. flavone, 3-hydroxyflavone, 5-hydroxyflavone, 7-hydroxyflavone and quercetin) and 3MPA-CdTe quantum dots (QDs) was studied. Investigation was based on results achieved by photoluminescence and electronic absorption spectroscopies, complemented by electrophoretic mobility and conductivity studies. The results showed that quercetin produces significant photoluminescence quenching of QDs in water, compared to the response in the presence of either flavone or the single-hydroxylated flavones, likely due to the increased hydrophilicity of the former. In contrast, in aqueous media containing cationic surfactant cetytrimethylammonium bromide (CTAB), interactions are modulated by solubilization of flavonoids in the microenvironments with different polarity of surfactant aggregates around the QDs. The results suggest that the photoluminescence response of 3MPA-CdTe QDs is related not only to the chemical structure of the flavonoids, but also to the nature of environment surrounding the dispersed particles.