Abstract
In this work, it is presented for the first time that nitrogen and chlorine co-doped carbon nanodots (N,Cl-CDs) were synthesized by simply mixing glucose, concentrated hydrochloric acid (HCl), and 1,2-ethylenediamine (EDA). No external heat was employed; the neutralization reaction served as the heat source. The glucose served as the carbon source while EDA and HCl were the N and Cl dopants, respectively. The fluorescence of N,Cl-CDs was adequately quenched by hexavalent chromium Cr(VI) based on a combination of dynamic quenching and inner filter effect (IFE). Accordingly, an efficient N,Cl-CDs-based fluorescence probe was established for sensitive and selective detection of Cr(VI). The proposed fluorescence sensor provides a linear recognition range for Cr(VI) determination from 3 to 40 µM with a limit of detection (LOD) of 0.28 µM (14.6 µg/L). The proposed fluorescence method was successfully utilized to detect Cr(VI) in different water samples with satisfactory results. The spike recoveries vary from 97.01% to 103.89% with relative standard deviations (RSDs) of less than 0.82%. This work highlights the development of a simple, ultrafast, and energy-saving one-step synthetic route to fabricate N,Cl-CDs for highly selective and sensitive detection of Cr(VI) in real water samples. It is anticipated that the proposed fluorescence method could be further explored and widely used for Cr(VI) detection in the environmental industry.
Highlights
Fluorescent carbon nanodots (CDs) with typical sizes below 10 nm have received considerable attention due to their excellent optical features such as upconversion photoluminescence (PL), tunable excitation/emission, high photostability, low cytotoxicity, and excellent biocompatibility [1].The PL property of C-dots has generated numerous publications on various applications such as bioimaging [2,3] and nanosensors [4,5]
The results show that the lifetime of N,Cl-CDs decreases when Cr(VI) is introduced, indicating that fluorescence sensing belongs to the dynamic quenching process [9]
A simple, ultrafast, and energy-efficient approach was for the first time presented to fabricate highly fluorescent N,Cl-CDs by mixing glucose, concentrated hydrochloric acid (HCl), and EDA with the neutralization reaction as the heat source
Summary
Fluorescent carbon nanodots (CDs) with typical sizes below 10 nm have received considerable attention due to their excellent optical features such as upconversion photoluminescence (PL), tunable excitation/emission, high photostability, low cytotoxicity, and excellent biocompatibility [1].The PL property of C-dots has generated numerous publications on various applications such as bioimaging [2,3] and nanosensors [4,5]. Numerous accounts of efforts have been devoted to enhancing the PL performance of CDs [6,7,8] and extending their applications in analysis and sensing. Heteroatoms doping is considered to be the most useful approach to improve fluorescence properties of Sensors 2018, 18, 3416; doi:10.3390/s18103416 www.mdpi.com/journal/sensors. Nitrogen (N) doping was the first approach employed to improve the PL performance of CDs. N doping could introduce defect sites and provide potential active sites to CDs, leading to substantial fluorescence enhancement of CDs; some reported N-CDs are restricted from low aqueous dispersity or weak resistance to metal ion interference, acid or base [10,11,12]. Doping other heteroatoms in combination with N was found to be useful in overcoming these shortcomings [12,13,14]
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