N-Doped Carbon Dots Synthesized from Ethylene Glycol and β-Alanine for Detection of Cr(VI) and 4-Nitrophenol via Photoluminescence Quenching

Abstract

We present here a facile method for nonaqueous synthesis of highly crystalline nitrogen-doped carbon dots (N-CDs) via oligomerization of ethylene glycol while heating with βalanine at 170 °C for 30 min. It exhibited bright bluish photoluminescence (PL) at λ emission = 461 nm, corresponding to a relative PL quantum yield of 14.3% and an average PL lifetime of 7.4 ns. High-resolution transmission electron microscopy of N-CDs revealed systematically self-assembled transverse oligomeric chains of ethylene glycol doped with β-alanine to form hexagonal symmetry, and their crystalline nature was revealed from electron diffraction measurement. The structure and composition of N-CDs are deduced from 13 C nuclear magnetic resonance, highresolution mass spectrometry, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy measurements, which collectively suggested oligomerization of β-alanine-doped ethylene glycol. The N-CDs are then demonstrated as an efficient probe for quantitative detection of Cr(VI) species at different pHs and 4-nitrophenol (4-NP) via PL quenching. The limits of detection (LoD) are deduced from respective linear Stern−Volmer plots, e.g., 1.1 μM for H 2 CrO 4 (at pH 0.9), 2.5 μM for HCrO 4 − (at pH 3.5), and 0.29 μM for CrO 4 2− (at pH 9.0). The detection of Cr(VI) is highly selective against several cationic (e.g.

Fluorescent “on–off–on” sensor based on N,S co-doped carbon dots from seaweed (Sargassum carpophyllum) for specific detection of Cr(vi) and ascorbic acid

“…It indicated the FL quenching mechanism of N,S-CDs towards Cr(VI) was referred to the inner lter effect (IFE), which occurred between the uorophore and absorber due to the absorption of the emission and/or excitation light of the uorophore by the absorbers in detection system. 50,51 In addition, the UV-vis absorbance spectrum of N,S-CDs/Cr(VI) at different concentration of AA were recorded to research the mechanism of N,S-CDs/Cr(VI) towards AA. As shown in Fig.…”

Strategy to Synthesize Tunable Multiemission Carbon Dots and Their Multicolor Visualization Application

“…These sensitive probes can be used to quickly and conveniently identify targets using the naked eye with an ultraviolet (UV) lamp. To date, many single-wavelength probes have been established using single-emission CDs. − For example, Feng et al designed a “turn on” probe for the detection of endogenous ascorbic acid using near-infrared graphene quantum dots . Nitrogen-doped CDs can be an efficient probe for the quantitative detection of Cr­(VI) .…”

“…To date, many single-wavelength probes have been established using single-emission CDs. − For example, Feng et al designed a “turn on” probe for the detection of endogenous ascorbic acid using near-infrared graphene quantum dots . Nitrogen-doped CDs can be an efficient probe for the quantitative detection of Cr­(VI) . Histidine can effectively recover the FL of yellow CDs quenched by fluoroquinolones in the “turn off–on” mode .…”

“…10 Nitrogen-doped CDs can be an efficient probe for the quantitative detection of Cr(VI). 12 Histidine can effectively recover the FL of yellow CDs quenched by fluoroquinolones in the "turn off−on" mode. 13 However, a variety of interferences negatively affect the accurate quantification of analytes.…”

Polychromatic Carbon Dots Prepared from m-Phenylenediamine and Urea as Multifunctional Fluorescent Probes

“…Shang et al used basic fuchsin and citric acid to prepare CD-based fluorescent probes and applied them to the detection of intracellular pH . CD nanoprobes are also used to detect organic molecules such as caffeine, melamine, organophosphorus pesticide, and tartar yellow. − Wang et al prepared blue, green, and yellow CDs from l -cysteine and lactic acid by a one-step reflux method. Caffeine was detected by blue CDs, melamine was detected by green CDs combined with nanoscale silver, and organophosphorus pesticides were detected by yellow CDs .…”