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Title: N-Doped Carbon Dots Synthesized from Ethylene Glycol and β-Alanine for Detection of Cr(VI) and 4-Nitrophenol via Photoluminescence Quenching
Authors: Das D.
Dutta, Raj Kumar
Published in: ACS Applied Nano Materials
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 β-alanine at 170 °C for 30 min. It exhibited bright bluish photoluminescence (PL) at λemission = 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 13C nuclear magnetic resonance, high-resolution 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 H2CrO4 (at pH 0.9), 2.5 μM for HCrO4- (at pH 3.5), and 0.29 μM for CrO42- (at pH 9.0). The detection of Cr(VI) is highly selective against several cationic (e.g., Na+, K+, Mg2+, Ca2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and Pb2+) and anionic (Cl-, F-, PO43-, SO42-, NO3-, CO32-, HCO3-, and AsO43-) interfering agents. Similarly, the LoD of 4-nitrophenol was determined to be 0.4 μM, which is significantly better than structurally similar compounds, e.g., phenols, benzene, and their derivatives. The mechanism of detecting Cr(VI) and 4-NP by N-CDs has been attributed to a combination of static-type PL quenching and an inner filter effect. Finally, practicality of the detection strategy by our method was assessed by analyzing spiked real samples, e.g., municipality tap water and river water. The accuracy and precision of measuring Cr(VI) and 4-nitrophenol by our method are comparable with those measured by inductively coupled plasma optical emission spectroscopy and high-performance liquid chromatography, respectively. © 2021 American Chemical Society.
Citation: ACS Applied Nano Materials, 4(4): 3444-3454
Issue Date: 2021
Publisher: American Chemical Society
Keywords: limit of detection
nitrogen-doped carbon dots
photoluminescence quenching
real sample analysis
sensing of Cr(VI) and 4-NP
ISSN: 25740970
Author Scopus IDs: 56723357200
Author Affiliations: Das, D., Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, 247667, India
Dutta, R.K., Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, 247667, India, Centre of Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
Funding Details: D.D. is grateful to the Ministry of Human Resource Development (MHRD), Government of India for providing a Senior Research fellowship. R.K.D. is grateful to the UGC-DAE-CSR Kolkata Centre for financial support (grant no. UGC-DAE-CSR-KC/CRS/19/TE09/1077/1093). The authors acknowledge Mr. Nabojit Kar, an undergraduate student of IISER Kolkata, who did preliminary study in our group as an IIT Roorkee-sponsored SPARK summer intern scholar. The authors are thankful to the Centre of Nanotechnology, Department of Chemistry, and Institute Instrumentation Centre of IIT Roorkee for instrumental facilities. UGC-DAE-CSR-KC/CRS/19/TE09/1077/1093; Ministry of Human Resource Development, MHRD
Corresponding Author: Dutta, R.K.; Department of Chemistry, India; email:
Appears in Collections:Journal Publications [CY]

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