Supramolecular strategy to construct quantum dot-based sensors for detection of paraoxon

The development of advanced tools for sensing specific materials remains an ongoing challenge. Detailed below is a new quantum dot (QD)-based sensor via supramolecular interactions, demonstrating a novel simplicity of design to obtain sensitive QDs while avoiding their covalent cross-linking. A simple label-free and turn-off method for the detection of paraoxon and its degradation products in aqueous media was proposed by using the fluorescent QD/surfactant/cyclodextrin supramolecular system. This nanocomposite was prepared from 3-mercaptopropionic acid-capped CdTe QDs coated with cetyltrimethylammonium bromide (CTAB) through electrostatic self-assembly. Further nanocomposite modification by beta-cyclodextrin (5-CD), thanks to hydrophobic interaction between cetyl tails of surfactants and inner cavity of macrocycle contributed to an increase in emission intensity and stability in aqueous solution. The strong fluorescence of CdTe/CTAB/beta-CD nano composite can be effectively quenched by the addition of paraoxon due to the host-guest complexation between beta-CD cavity and paraoxon degradation product. The functionality of the paraoxon sensor was also tested with blood samples of paraoxon-poisoned rats (1/2 x LD50). These fluorescent nanocomposites were obtained by using the simple supramolecular method to coat QDs with surfactant-cyclodextrin shells. This coating strategy potentially offers common method for the functionalization of QDs and avoids time-consuming synthesis procedures.