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Nanomaterials 2018, 8(6), 372; https://doi.org/10.3390/nano8060372

Capacitively Coupled Plasma Discharge of Ionic Liquid Solutions to Synthesize Carbon Dots as Fluorescent Sensors

1
Department of Beauty and Health Care, Min-Hwei Junior College of Health Care Management, No. 1116, Sec. 2, Zhongshan E. Rd., Tainan 73658, Taiwan
2
School of Pharmacy, China Medical University, No. 91 Hsueh-Shih Road, Taichung 40402, Taiwan
*
Author to whom correspondence should be addressed.
Received: 25 April 2018 / Revised: 21 May 2018 / Accepted: 23 May 2018 / Published: 26 May 2018
(This article belongs to the Special Issue Plasma based Synthesis and Modification of Nanomaterials)
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Abstract

Oxygen and nitrogen capacitively coupled plasma (CCP) was used to irradiate mixtures of aliphatic acids in high boiling point solvents to synthesize fluorescent carbon dots (C-dots). With a high fluorescence intensity, the C-dots obtained from the O2/CCP radiation of a 1-ethyl-3-methylimidazolium dicyanamide ionic liquid solution of citric acid were characterized with an average diameter of 8.6 nm (σ = 1.1 nm), nitrogen and oxygen bonding functionalities, excitation-independent emissions, and upconversion fluorescence. Through dialysis of the CCP-treated C-dots, two emissive surface states corresponding to their respective functionalities and emissions were identified. The fluorescence spectrum of the CCP-treated C-dots was different from that of the microwave irradiation and possessed higher intensity than that of hydrothermal pyrolysis. By evaluation of the fluorescence quenching effect on flavonoids and metal ions, the CCP-treated C-dots showed a high selectivity for quercetin and sensitivity to Hg2+. Based on the Perrin model, a calibration curve (R2 = 0.9992) was established for quercetin ranging from 2.4 μM to 119 μM with an LOD (limit of detection) = 0.5 μM. The quercetin in the ethanol extract of the sun-dried peel of Citrus reticulata cv. Chachiensis was determined by a standard addition method to be 4.20 ± 0.15 mg/g with a matrix effect of 8.16%. View Full-Text
Keywords: capacitively coupled plasma; carbon dots; ionic liquid; mercury ion; quercetin; upconversion capacitively coupled plasma; carbon dots; ionic liquid; mercury ion; quercetin; upconversion
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Ke, C.-B.; Lu, T.-L.; Chen, J.-L. Capacitively Coupled Plasma Discharge of Ionic Liquid Solutions to Synthesize Carbon Dots as Fluorescent Sensors. Nanomaterials 2018, 8, 372.

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