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Nanomaterials 2018, 8(10), 864; https://doi.org/10.3390/nano8100864

Investigation of the Microstructures of Graphene Quantum Dots (GQDs) by Surface-Enhanced Raman Spectroscopy

The Beijing Key Laboratory for Nano-photonics and Nano-structure, Department of Physics, Capital Normal University, Beijing 100048, China
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Received: 21 September 2018 / Revised: 17 October 2018 / Accepted: 19 October 2018 / Published: 22 October 2018
(This article belongs to the Special Issue Surface-Enhanced Raman Spectroscopy in the Nano-World)
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Abstract

Photoluminescence (PL) is the most significant feature of graphene quantum dots (GQDs). However, the PL mechanism in GQDs has been debated due to the fact that the microstructures, such as edge and in-plane defects that are critical for PL emission, have not been convincingly identified due to the lack of effective detection methods. Conventional measures such as high-resolution transmission electron microscopy and infrared spectroscopy only show some localized lattice fringes of GQDs and the structures of some substituents, which have little significance in terms of thoroughly understanding the PL effect. Here, surface-enhanced Raman spectroscopy (SERS) was introduced as a highly sensitive surface technique to study the microstructures of GQDs. Pure GQDs were prepared by laser ablating and cutting highly oriented pyrolytic graphite (HOPG) parallel to the graphite layers. Consequently, abundant SERS signals of the GQDs were obtained on an Ag electrode in an electrochemical environment for the first time. The results convincingly and experimentally characterized the typical and detailed features of GQDs, such as the crystallinity of sp2 hexagons, the quantum confinement effect, various defects on the edges, sp3-like defects and disorders on the basal planes, and passivated structures on the periphery and surface of the GQDs. This work demonstrates that SERS is thus by far the most effective technique for probing the microstructures of GQDs. View Full-Text
Keywords: graphene quantum dots; surface-enhanced Raman spectroscopy; photoluminescence; laser ablation; passivation graphene quantum dots; surface-enhanced Raman spectroscopy; photoluminescence; laser ablation; passivation
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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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Wu, J.; Wang, P.; Wang, F.; Fang, Y. Investigation of the Microstructures of Graphene Quantum Dots (GQDs) by Surface-Enhanced Raman Spectroscopy. Nanomaterials 2018, 8, 864.

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