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

Abstract

To achieve a rapid, sensitive, and economical method for the detection of ascorbic acid (AA) in the presence of Fe 3+ , 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 Fe 3+ 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 Fe 3+. Therefore, a switch-on sensor (N,S-co-CDs/Fe 3+ 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.

Facile Synthesis of N, S-Doped Carbon Quantum Dots from Food Waste as Fluorescent Probe for Sensitive Detection of Thiamphenicol and Its Analogues in Real Food Samples along with an Application in Bioimaging

“…The zeta potential of N, S-CDs was measured to be nearly −17.4 mV, which was attributed to the large number of nitrogen hydrogen bond and carbonyl groups present on the surface of N, S-CDs. However, the zeta-potential dropped to −26.70 mV after adding TAP to the N, S-CDs solutions, showing that the hydroxyl and hydrogen bonds in TAP interact with N, S-CDs to generate complexes such as carboxyl and amine groups, which is further validation of the static quenching results [ 36 ].…”

“…According to the Figure 4 a, a typical absorption peaks at 265 nm could be interpreted as the π-π* (C=C or C=O) [ 35 ] and n-π* (C=N or C-OH) electronic transitions. Studies have shown that doping properly could cause the change of local surface state and the recombination of excited-state energy, promoting the strong fluorescence emission of N, S-CDs in the form of main chromophore, which caused these characteristic absorptions to occur [ 31 , 36 ]. It can be found that the fluorescence intensity of N, S-CDs increased initially and then decreased, increasing the excitation wavelength ( Figure 4 b), and when excited at 372 nm, the N, S-CDs reflects the strongest blue fluorescence (inset of Figure 4 a) near the emission peak of 446 nm.…”

Accuracy improvement via novel ratiometry design in distance-based microfluidic paper based analytical device: instrument-free point of care testing

“…The color of the complex formed between Fe 3+ and phen is pale yellow, which changes to orange-red when the Fe 3+ is reduced to Fe 2+ . This principle was used herein as a probe for the detection of AA since AA can reduce Fe 3+ to Fe 2+ , 41,42 hence changing the color of the complex; the reaction between Fe 3+ -(phen) 3 and AA is given in eqn (1) in Fig. 1S.…”

Highly sensitive and selective fluorescence sensing and imaging of Fe3+ based on a novel nitrogen‐doped graphene quantum dots

“…[5][6][7][8] In addition, the content of Fe 3+ ions in environmental water is an important indicator for monitoring water pollution. [9][10][11][12] Therefore, it is very important to develop sensitive analytical methods for Fe 3+ in biological and environmental samples. Recently, GQDs have been used as an important fluorescence sensor platform for the detection of Fe 3+…”