Formation of CdTe core and CdTe@ZnTe core–shell quantum dots via hydrothermal approach using dual capping agents: deciphering the food dye sensing and protein binding applications†

Excessive use of food coloring agents in the food industry to make the food more attractive or improve the taste has caused various health and ecological problems. Therefore, it is necessary to develop a reliable, sensitive, and selective sensing probe to detect food dyes in different food products for future industrial processing and biosafety. In recent decades, surface-functionalized quantum dots (QDs), owing to their unique optical properties, have gained tremendous interest for a wide range of applications, including biomedical, bioimaging and sensing applications. Herein, we have reported the synthesis of excellent colloidal stable and highly luminescent CdTe core and CdTe@ZnTe core–shell QDs using dual functionalizing agents, polyvinyl pyrrolidone and vitamin C. The synthesized QDs were explored as excellent sensing probes for the food dyes carmoisine, Ponceau 4R and tartrazine with limit of detection (LOD) values of 0.097 ± 0.006, 0.147 ± 0.001 and 0.044 ± 0.001 μM for CdTe–PVP QDs and 0.079 ± 0.001, 0.114 ± 0.002 and 0.042 ± 0.001 μM for CdTe@ZnTe–PVP QDs, respectively. The sensitivity of the synthesized QDs for the food dyes was also investigated in real samples (soft drinks and medications). Moreover, considering the potential effects of QDs as therapeutics or nano-drug carriers, the interactions between the synthesized QDs and carrier protein human serum albumin (HSA) were investigated. The binding affinity was observed to be in the order of 10⁴ M⁻¹. QDs were found to quench the intrinsic fluorescence of HSA, and both types of quenching (static and dynamic) occur via electrostatic interactions in association with hydrophobic forces without any significant alteration in the protein structure.