Nitrogen-Doped Carbon Quantum Dots as Fluorescent Probes for Sensitive and Selective Detection of Nitrite

Abstract

Nitrites are the upstream precursors of the carcinogenic nitrosamines, which are widely found in the natural environment and many food products. It is important to develop a simple and sensitive sensor for detecting nitrites. In this work, a fluorescence probe based on nitrogen-doped carbon quantum dots (N-CQDs) was developed for the sensitive and selective determination of nitrites. At pH 2, the fluorescence of N-CQDs can be selectively quenched by nitrite due to the fact N-nitroso compounds can be formed in the reaction of amide groups with nitrous acid, which results in fluorescence static quenching. Under optimal conditions, fluorescence intensity quenching upon addition of nitrite gives a satisfactory linear relationship covering the linear range of 0.2–20 μM, and the limit of detection (LOD) is 40 nM. Moreover, this method has been successfully applied to the determination of nitrites in tap water, which indicates its great potential for monitoring of nitrites in environmental samples.

Carbon Dots Derived from the Maillard Reaction for pH Sensors and Cr (VI) Detection

“…As shown in Figure 2b, the UV-vis absorption spectrum showed two absorption bands at 270 nm and 350 nm, resulting from the π-π* electronic transition of C=C and the n-π* transition of surface groups (C=O and C=N, etc. ), respectively [36,37]. The fluorescence emission spectrum showed three absorption peaks at 258 nm (Ex A), 300 nm (Ex B) and 370 nm (Ex C), which were consistent with the results of the UV-visible absorption spectrum.…”

“…Nanomaterials 2020, 10, x FOR PEER REVIEW 6 of 14 groups existing on the surface of MR-CDs [37]. The sharp peak at 1610 cm −1 was attributed to the stretching vibration of C=C/C=N bonds [41].…”

Preparation of Multifunctional N-Doped Carbon Quantum Dots from Citrus clementina Peel: Investigating Targeted Pharmacological Activities and the Potential Application for Fe3+ Sensing

“…The most common method for CQDs purification is dialysis using membrane tubings [ 18 , 26 , 27 ]. However, the efficiency of the dialysis procedure is more or less disputable.…”

“…The presence of the main functional groups was demonstrated by FTIR spectroscopy measurements, as shown in Figure 1 B. The common characteristics for all prepared CQDs are the broad peaks at approximately 3267–3305 cm −1 which indicated the existence of O-H and N-H groups and the presence of functionalized groups [ 26 , 27 ]. The strong peaks centred at 1680 cm −1 and 1041 cm −1 could be attributed to C=O and C-O vibration modes.…”

Application of Graphene-Based Materials for Detection of Nitrate and Nitrite in Water—A Review

“…The concentration of nitrate and nitrite in water has become one of the indexes for evaluating water quality. Therefore, the detection of nitrate and nitrite in water samples at low concentrations has been the focus of research [11].So far, many methods have been used to detect nitrate and nitrite, such as spectrophotometry [12][13][14], chemiluminescence [15,16], chromatography [17], fluorescence [18,19] and electrochemical methods [20][21][22]. Among them, the electrochemical method is one of the most commonly used detection methods because of its advantages of being low cost, fast, direct and high efficiency [23].…”