Analytical Sciences

Microwave-assisted Synthesis of N,S-co-carbon Dots as Switch-on Fluorescent Sensor for Rapid and Sensitive Detection of Ascorbic Acid in Processed Fruit Juice

Sifan XU,* Shuqi YE,** Yunhui XU,** Feifan LIU,** Yushun ZHOU,** Qian YANG,* Hailong PENG,*,** Hua XIONG,* and Zhong ZHANG*,***

*State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China
**School of Resources, Environmental, and Chemical Engineering, Nanchang University, Nanchang 330031, China
***Shaanxi Engineering Laboratory for Food Green Processing and Safety Control, College of Food Engineering and Nutritional Science, Shaanxi Normal University, Xi’an 710119, China

To achieve a rapid, sensitive, and economical method for the detection of ascorbic acid (AA) in the presence of Fe³⁺, a nitrogen and sulfur co-doped carbon dots (N,S-co-CDs) based fluorescence sensing system was developed. In this work, N,S-co-CDs were successfully synthesized via a one-step microwave-assisted method within 2.5 min using ammonium citrate and L-cysteine as precursors. The fluorescence of N,S-co-CDs was quenched (off ) by Fe³⁺ through a static-quenching mechanism. Subsequently, the fluorescence was recovered (on) after introducing AA into the quenched system, which was attributed to the reduction effect of AA for Fe³⁺. Therefore, a switch-on sensor (N,S-co-CDs/Fe³⁺ system) was developed for AA detection. Under optimal conditions, the limit of detection (LOD) of 2.31 μmol/L for AA was obtained over a linear range from 0 to 150 μmol/L. Furthermore, the proposed sensing method was successfully applied to detect AA in processed fruit juice with satisfactory results. The most important is that the sensor derived from a microwave-assisted method has simple and eco-friendly synthesis processes, is rapid, and has high detection efficiency. Therefore, such a switch-on sensor may be a promising candidate sensor for AA detection in processed fruit samples.

J-STAGE: View this article in J-STAGE