title: Simultaneously fabrication of free and solidified N, S-doped graphene quantum dots via a facile solvent-free synthesis route for fluorescent detection.
abstract: A facile one-step solvent-free synthesis approach is proposed for the simultaneous fabrication of free and solidified N, S-doped graphene quantum dots (N, S-GQDs) by using citric acid as precursor and L-cysteine as dopant. Graphene nucleus is firstly formed via the intermolecular dehydration of citric acid. N and S are then incorporated into the graphene structure by attacking the margin of graphene nucleus. The cross-linking among the graphene nucleus via the intermolecular condensation leads to the generation of free N, S-GQDs, while the intermolecular amidation between L-cysteine molecules and graphene nucleuses contributes to the solid-state fluorescence graphene quantum dots (SSF-GQDs). The free N, S-GQDs exhibit favorable photoluminescence behaviors such as high fluorescent quantum yield of 74.5%, stable photoluminescence within a wide range of pH and high tolerance to external ionic strength of up to 1.0molL-1NaCl, making it excellent fluorescence probe for the sensitive detection of Fe3+with a linear range of 0.01-3μM and a detection limit of 3.3nM. The solidification of GQDs prevents the aggregation of GQDs efficiently and offers the solidified N, S-GQDs yellow-green fluorescence, with a fluorescence quantum yield of 10.6%. This proposed protocol provides a novel avenue to fabricate diverse fluorescent graphene materials for different practical applications.
authors.affiliation: Research Center for Analytical Sciences, College of Sciences, Northeastern University, Box 332, Shenyang 110819, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Xia
authors.affiliation: Research Center for Analytical Sciences, College of Sciences, Northeastern University, Box 332, Shenyang 110819, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Hai
authors.affiliation: Research Center for Analytical Sciences, College of Sciences, Northeastern University, Box 332, Shenyang 110819, China. Electronic address: chenxuwei@mail.neu.edu.cn.
authors.forename: Xu-Wei
authors.initials: XW
authors.lastname: Chen
authors.affiliation: Research Center for Analytical Sciences, College of Sciences, Northeastern University, Box 332, Shenyang 110819, China. Electronic address: jianhuajrz@mail.neu.edu.cn.
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Wang
keywords: Citric acid; Graphene quantum dots; L-cysteine; N; S-doping; Solvent-free synthesis