A Novel Route to High-Quality Graphene Quantum Dots by Hydrogen-Assisted Pyrolysis of Silicon Carbide

Abstract

Graphene quantum dots (GQDs) can be highly beneficial in various fields due to their unique properties, such as having an effective charge transfer and quantum confinement. However, defects on GQDs hinder these properties, and only a few studies have reported fabricating high-quality GQDs with high crystallinity and few impurities. In this study, we present a novel yet simple approach to synthesizing high-quality GQDs that involves annealing silicon carbide (SiC) under low vacuum while introducing hydrogen (H) etching gas; no harmful chemicals are required in the process. The fabricated GQDs are composed of a few graphene layers and possess high crystallinity, few defects and high purity, while being free from oxygen functional groups. The edges of the GQDs are hydrogen-terminated. High-quality GQDs form on the etched SiC when the etching rates of Si and C atoms are monitored. The size of the fabricated GQDs and the surface morphology of SiC can be altered by changing the operating conditions. Collectively, a novel route to high-quality GQDs will be highly applicable in fields involving sensors and detectors.

Recent Advances on Graphene Quantum Dots for Bioimaging Applications

“…Meanwhile, the longer laser treatment yields bigger-size GQDs. Recently, a facile approach to design highly pure GQDs in the absence of any toxic chemical was presented by Lee et al (2020). Briefly, they annealed SiC followed by etching with low vacuum H 2 gas, resulting in highly crystalline and pure GQDs with fewer defects and the lack of surface functional groups of oxygen.…”

Carbon Quantum Dots Derived from Different Carbon Sources for Antibacterial Applications

“…Poor size control [19,[37][38][39][40][41][42][43][44] Avoids use of strong acids or alkalis, cost effective, suitable for widely different carbon sources…”

“…Poor size control [19,[37][38][39][40][41][42][43][44] Hydrothermal synthesis "Top-down" synthesis methods break down large carbon-rich materials as a carbon source, whereas "bottom-up" methods synthesize carbon quantum dots from small precursor molecules. Both the method applied as well as the carbon source or precursor used are determinant factors for the final physico-chemical and functional properties of carbon "Top-down" synthesis methods break down large carbon-rich materials as a carbon source, whereas "bottom-up" methods synthesize carbon quantum dots from small precursor molecules.…”

“…Pyrolysis can be applied to synthesize carbon quantum dots by heating carbon sources to reaction temperatures up to 1500 °C [ 42 ]. Pyrolysis allows one to synthesize carbon quantum dots within several hours, but with a highly variable yield ranging from 0.01% [ 37 ] to 51% [ 19 ], depending on the carbon source and treatment conditions applied.…”

“…Pyrolysis allows one to synthesize carbon quantum dots within several hours, but with a highly variable yield ranging from 0.01% [ 37 ] to 51% [ 19 ], depending on the carbon source and treatment conditions applied. Pyrolysis can typically use widely different carbon sources, ranging from silicon carbide [ 42 ], flour [ 43 ], gentamicin sulfate [ 39 ], ammonium citrate [ 19 ] or dopamine [ 38 ], together with spermidine, citric acid or dicyandiamide [ 41 ]. In pyrolysis, carbon quantum dots result from intermolecular dehydration, carbonization and condensation, and the resulting carbon skeleton is held together by chemical groups such as –SO 2 , –HSO 3 and –H 2 PO 4 [ 44 ].…”