Electrochemical Cutting in Weak Aqueous Electrolytes: The Strategy for Efficient and Controllable Preparation of Graphene Quantum Dots

Abstract

The controllable and efficient electrochemical preparation of highly crystalline graphene quantum dots (GQDs) in an aqueous system is still challenging. Here, we developed a weak electrolyte-based (typically an ammonia solution) electrochemical method to enhance the oxidation and cutting process and therefore achieve a high yield of GQDs. The yield of GQDs (3-8 nm) is 28%, approximately 28 times higher than the yield of GQDs prepared by other strong electrolytes. The whole preparation process can be accomplished within 2 h because of the effective free radical oxidation process and the suppressed intercalation-induced exfoliation in weakly ionized aqueous electrolytes. The GQDs also showed excellent crystallinity which is obviously better than the crystallinity of GQDs obtained via bottom-up approaches. Moreover, amino-functionalization of GQDs can be realized by manipulating the electrolyte concentration. We further demonstrate that the proposed method can also be expanded to other weak electrolytes (such as HF and HS) and different anode precursor materials (such as graphene/graphite papers, carbon fibers, and carbon nanotubes).

Synthesis of graphene quantum dots and their applications in drug delivery

“…In order to controllably and efficiently prepare highly crystalline GQDs in aqueous systems, researchers [76] have developed a weak electrolyte (such as ammonia solution) electrochemical method to enhance the oxidation and cutting process, thereby achieving high yield of GQDs. The af-GQDs were prepared using a circular graphene paper as the anode, a Pt sheet as the cathode, and an ammonia solution (nitrogen source) as the electrolyte and operated in a constant voltage mode (30 V) for 2 h in an electrochemical cell ( Fig.…”

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

“…GQDs have usually been fabricated via top-down cutting routes and bottom-up synthesis methods [ 27 ], such as hydrothermal methods [ 5 , 28 , 29 , 30 ], enhanced hydrothermal methods [ 31 , 32 ], carbonization [ 23 ], acidic exfoliation routes [ 33 ], and electrochemical strategies [ 34 , 35 ]. These methods suffer from complex and severe formation processes, including high temperature and concentrated acid environments [ 33 , 36 , 37 ], inevitably leading to the existence of chemical additives, residues and stabilizers.…”

Earth abundant colloidal carbon quantum dots for luminescent solar concentrators

“…The obtained C-dots have several advantages, such as relatively high purity, high product yield, low cost, easy control over the size and chemical composition, and good repeatability. 62,81,100 Deng et al prepared C-dots directly from low-molecular-weight alcohols via the electrochemical method. 81 The size of the as-prepared C-dots can be adjusted by varying the applied potential.…”

“…101 Compared with other synthesis methods of C-dots, the electrochemical method does not require further complicated purification procedures, 101 while the as-prepared C-dots have a lower QY than that of those synthesized by other approaches. 62,81,100,101 We summarized the synthesis of C-dots using different precursors and solvents through the above-mentioned methods. The hydro/solvothermal method is very simple to operate and the properties of the C-dots can be well controlled by controlling the degree of decomposition.…”