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Simple preparation of graphene quantum dots with controllable surface states from graphite.

ABSTRACT: Graphite is economic and earth-abundant carbon precursor for preparing graphene quantum dots (GQDs). Here, we report a facile and green approach to produce GQDs from graphite flakes via a pulsed laser ablation (PLA) method assisted by high-power sonication. A homogeneous dispersion of graphite flakes, caused by high-power sonication during PLA, leads to the formation of GQDs following a laser fragmentation in liquid (LFL) rather than laser ablation in liquid (LAL) mechanism. The final product of GQDs exhibits the distinct structural, chemical, and optical properties of pristine graphene itself. However, graphene oxide quantum dots (GOQDs) with abundant surface oxygen-rich functional groups are readily formed from graphite flakes when high-power sonication is not employed during the PLA process. GQDs and GOQDs show a significantly different luminescence nature. Hence, selective production of either functional GQDs or GOQDs can be achieved by simply turning the high-power sonication during the PLA process on and off. We believe that our modified PLA process proposed in this work will further open up facile and simple routes for designing functional carbon materials.

SUBMITTER: Kang S

PROVIDER: S-EPMC9075865 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Simple preparation of graphene quantum dots with controllable surface states from graphite.

Kang Sukhyun S Jeong Young Kyu YK Jung Kyung Hwan KH Son Yong Y Choi Sung-Churl SC An Gae Seok GS Han Hyuksu H Kim Kang Min KM

RSC advances 20191125 66

Graphite is economic and earth-abundant carbon precursor for preparing graphene quantum dots (GQDs). Here, we report a facile and green approach to produce GQDs from graphite flakes <i>via</i> a pulsed laser ablation (PLA) method assisted by high-power sonication. A homogeneous dispersion of graphite flakes, caused by high-power sonication during PLA, leads to the formation of GQDs following a laser fragmentation in liquid (LFL) rather than laser ablation in liquid (LAL) mechanism. The final pro ...[more]

PMID: 35540206

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Project description:Graphene has unprecedented physical, chemical, and electronic properties, but need of the hour is to develop low-dimensional nanomaterials, such as graphene quantum dots (GQDs), that could be incorporated into nanoscale devices. This article depicts the production of GQDs from ultrafine, thin (0.8-1 nm), bilayer graphene sheets (GSs) possessing large micron-sized lateral dimension, low defect density (I D/I G: 0.1), and oxidation degree (C/O ratio: 27) of lowest level, in contrast to many other techniques where synthesis of GSs was done using analytical-grade expensive graphite electrodes. This low-cost manufacturing of GSs for industrial-scale applications was achieved by utilizing only 99%-purity graphite electrodes. The variants of such graphite electrodes (graphite rod, film, pencil) are etched in different pH electrolytes (H2SO4, NaCl, NaOH) via prompt electrochemical exfoliation, each giving more than 50% yield. Nowadays, semiconductor quantum dots (QDs) are utilized in smart device production industries, but their toxicity is a major issue of concern. Therefore, the dimension of this two-dimensional (2D) material is reduced to <10 nm to generate GQDs. A facile and highly reproducible approach has been reported for the large-scale generation of GQDs (size ca. 6-10 nm) with minimal surface defects. The protocol followed in this article to synthesize GQDs involves the use of ethylenediamine (en), which passivates the surface and reduces defects, thereby enhancing the optical properties. We demonstrate the correlation of the electrochemical and hydrothermal parameters with the growth mechanism and morphological, structural, chemical, and optical properties of the graphene nanomaterials. Raman spectroscopy and X-ray diffraction (XRD) reveal the structural configurations of GSs and GQDs to investigate the nature of defects. Field emission scanning electron microscopy (FESEM) confirms the morphological characteristics of the as-prepared GSs and GQDs with energy-dispersive X-ray (EDX) analysis determining the C/O ratio. The optical properties like UV-visible absorption and fluorescence assays show the quantum confinement effect phenomenon in GQDs. The obtained GSs and GQDs display enhanced solution stability in DI water and other solvents due to controllable oxidation degree as elucidated through Fourier transform infrared (FTIR) analysis.

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Simple preparation of graphene quantum dots with controllable surface states from graphite.

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Simple preparation of graphene quantum dots with controllable surface states from graphite.

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