One-pot synthesis of graphene quantum dots using humic acid and its application for copper (II) ion detection
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One-pot synthesis of graphene quantum dots using humic acid and its application for copper (II) ion detection Xiao Liu1 , Juan Han1, Xiaodong Hou2, Furkan Altincicek3 Xu Wu1,*, and Julia Xiaojun Zhao1,*
, Nuri Oncel3, David Pierce1,
1
Department of Chemistry, University of North Dakota, Grand Forks, ND 58202, USA Institute for Energy Studies, University of North Dakota, Grand Forks, ND 58202, USA 3 Department of Physics & Astrophysics, University of North Dakota, Grand Forks, ND 58202, USA 2
Received: 20 August 2020
ABSTRACT
Accepted: 17 November 2020
A new carbon source, humic acid, has been used in fabricating graphene quantum dots by a facial one-pot hydrothermal reaction. The morphology of the cyan emission graphene quantum dots has been characterized by high-resolution transmission electron microscopy (HRTEM). The result showed well-displayed crystalline with a lattice spacing of 0.286 nm. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) have demonstrated the diverse functional groups on GQDs, like carboxylic groups, which will cause significant fluorescence quenching by Cu2? because of the strong chelating interactions. The optical properties of GQDs were characterized by photoluminescence (PL) spectra and ultraviolet–visible (UV–Vis) spectroscopy; it showed that GQDs have an excitation-dependent fluorescence behavior and a large stoke shift with maximum excitation/emission wavelength at 360/470 nm. Furthermore, GQDs showed a good photostability by the kinetic analysis of irradiation for 1500 s and a relatively high quantum yield of 20%, which could be applied in bioimaging. Besides, the selectivity study of metal ions indicates that the GQDs could be used in Cu2? detection. The linear range is from 1 to 40 lM with the limit of detection (LOD) of 0.44 lM. Overall, this work provided a simple method to produce GQDs with low-cost raw material humic acid, which could be also used in Cu2? monitoring in river water.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
Handling Editor: Christopher Blanford.
Address correspondence to E-mail: [email protected]; [email protected]
https://doi.org/10.1007/s10853-020-05583-6
J Mater Sci
Introduction Fluorescent nanomaterials, due to their unique chemical, physical and optical properties, have been proved to be pivotal tools in sensing, imaging and some other biomedical applications [1–9]. In the past few decades, a number of fluorescence nanomaterials, including organic nanomaterials and inorganic nanomaterials, have been designed and synthesized to serve as bioimaging agents instead of organic dyes. Comparing with organic dyes, the excellent photostability, bright fluorescence intensity and low synthetic cost make fluorescent nanomaterials as effective fluorescent probes for sensing and imaging of biomolecules, cells, tissues and organisms [10–22]. For example, heavy metal-based semiconducting quantum dots (QDs) such as CdSe, CdTe have been successfully produced with broad adsorption, narrow, adjustab
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