title: Europium-decorated graphene quantum dots as a fluorescent probe for label-free, rapid and sensitive detection of Cu(2+) and L-cysteine.
abstract: In this work, europium-decorated graphene quantum dots (Eu-GQDs) were prepared by treating three-dimensional Eu-decorated graphene (3D Eu-graphene) via a strong acid treatment. Various characterizations revealed that Eu atoms were successfully complexed with the oxygen functional groups on the surface of graphene quantum dots (GQDs) with the atomic ratio of 2.54%. Compared with Eu free GQDs, the introduction of Eu atoms enhanced the electron density and improved the surface chemical activities of Eu-GQDs. Therefore, the obtained Eu-GQDs were used as a novel "off-on" fluorescent probe for the label-free determination of Cu(2+) and l-cysteine (L-Cys) with high sensitivity and selectivity. The fluorescence intensity of Eu-GQDs was quenched in the presence of Cu(2+) owing to the coordination reaction between Cu(2+) and carboxyl groups on the surface of the Eu-GQDs. The fluorescence intensity of Eu-GQDs recovered with the subsequent addition of L-Cys because of the strong affinity of Cu(2+) to L-Cys via the Cu-S bond. The experimental results showed that the fluorescence variation of the proposed approach had a good linear relationship in the range of 0.1-10 μM for Cu(2+) and 0.5-50 μM for L-Cys with corresponding detection limits of 0.056 μM for Cu(2+) and 0.31 μM for L-Cys. The current approach also displayed a special response to Cu(2+) and L-Cys over the other co-existing metal ions and amino acids, and the results obtained from buffer-diluted serum samples suggested its applicability in biological samples.
authors.affiliation: College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
authors.forename: Liping
authors.initials: L
authors.lastname: Lin
authors.affiliation: Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
authors.forename: Xinhong
authors.initials: X
authors.lastname: Song
authors.affiliation: Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
authors.forename: Yiying
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
authors.forename: Mingcong
authors.initials: M
authors.lastname: Rong
authors.affiliation: Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
authors.forename: Yiru
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Xiamen Huaxia College, Xiamen, 361024, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Xiamen Huaxia College, Xiamen, 361024, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Zhao
authors.affiliation: Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China; State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, 361005, China. Electronic address: xichen@xmu.edu.cn.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
mesh_terms: D000818:Animals; D002413:Cations, Divalent / Q000032:analysis; D002417:Cattle; D003300:Copper / Q000032:analysis*; D003545:Cysteine / Q000032:analysis / Q000097:blood*; D005063:Europium / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry*; D006801:Humans; D057230:Limit of Detection; D008958:Models, Molecular; D045663:Quantum Dots / Q000737:chemistry* / Q000648:ultrastructure; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D002413:Cations, Divalent; D005456:Fluorescent Dyes; D005063:Europium; D006108:Graphite; D003300:Copper; D003545:Cysteine
keywords: Change of electron density and surface chemical activities; Detection of Cu(2+) and L-Cys; Europium-complexed graphene quantum dots; Strong acid treatment; Three-dimensional Eu-complexed graphene