A novel CdTe QDs-CoOOH "on-off-on" fluorescent sensor for ascorbic acid detection

Ascorbic acid (AA) is an essential water-soluble vitamin that regulates human antioxidant defense and immune homeostasis, and serves as a vital nutritional index for evaluating the nutritional value and antioxidant quality of fruits, vegetables and beverages. Reliable quantification of AA is therefore essential for food quality monitoring and human health maintenance. Herein, a novel "on-off-on" fluorescence sensor by integrating CdTe quantum dots with CoOOH for convenient and accurate detection of ascorbic acid was established. A series of experiments was preliminarily carried out to optimize influencing factors (dosage, quenching temperature and time, recovery time), with optimal conditions that 500 μL CoOOH (1 mg/L), quenching at 60 °C for 5 min, and 50 min fluorescence recovery was obtained. Moreover, the developed method demonstrated high selectivity and a certain linear response from 0 to 7.10 μM and a remarkable detection limit of 0.0193 μM, enabling convenient quantification of ascorbic acid in practical applications. The sensing mechanism relied on a typical fluorescence resonance energy transfer (FRET) effect, briefly, CoOOH effectively quenched the intrinsic fluorescence of CdTe QDs as an efficient FRET acceptor, the addition of AA triggered the redox conversion of Co 3+ to Co 2+ in CoOOH, which disrupted the FRET system and thereby achieved prominent fluorescence recovery of CdTe QDs. With the merits of simple operation and high sensitivity, this facile sensing strategy provides a promising platform for accurate AA determination in real complex samples.