Synthesis of CdTe Quantum Dots-based Imprinting Fluorescent Nanosensor for Highly Specific and Sensitive Determination of Caffeic Acid in Apple Juices

Abstract

A facile method for the synthesis of molecularly imprinted polymers (MIPs) onto CdTe quantum dots (CdTe-QDs@MIPs) was successfully developed, and for the first time used as a sensitive fluorescent nanosensor for specific and rapid determination of caffeic acid (CA) in apple juices. Sol–gel polymerization was selected to fabricate hydrophilic MIPs layer using 3-(aminopropyl)triethoxysilane, tetraethyl orthosilicate, and CA as functional monomer, cross-linker and template, respectively. Under optimum experimental conditions, smaller CdTe-QDs@MIPs particles (48 nm) were synthesized with polymerization time at 2 min, which showed fast fluorescence quenching with response time at 3 min and high sensitivity with a limit of detection at 0.73 μg L−1. The fluorescence intensity of CdTe-QDs@MIPs presented excellent linearity with the concentration of CA in the range from 2 to 100 μg L−1 (R2, 0.9980). The developed method showed good repeatability with batch-to-batch relative standard deviation at 3.31%, and excellent selectivity over structural analogues. The practicability of the as-prepared CdTe-QDs@MIPs was confirmed by the analysis of CA in apple juices with satisfactory recoveries from 93.3% to 108.3%, and precisions <2.1%. Results demonstrated that a rapid, selective, and sensitive fluorescent method was successfully developed to detect CA in food samples.

Keywords

• CdTe quantum dots
• molecularly imprinted polymers
• sol–gel polymerization
• fluorescence detection
• caffeic acid
• apple juice