Quasi-Continuously Tuning the Size of Graphene Quantum Dots via an Edge-Etching Mechanism
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Quasi-Continuously Tuning the Size of Graphene Quantum Dots via an Edge-Etching Mechanism Shujun Wang1,2, Ivan S. Cole3 , Dongyuan Zhao4, and Qin Li1,2* 1
Queensland Miro- and Nanotechnology Centre, Griffith University, Nathan Campus, Brisbane, QLD 4111, Australia 2 School of Engineering (Environmental), Griffith University, Nathan Campus, Brisbane, QLD 4111, Australia 3 CSIRO Materials Science and Engineering, –Gate 5, Normanby Road, Clayton, VIC 3168, Australia 4 Department of Chemistry & Laboratory of Advanced Materials, Fudan University, Shanghai, 200433, P.R. China *Corresponding author at: Nathan campus Griffith University,170 Kessels Road, Nathan, QLD 4111, Au; E-mail address: [email protected]; Tel.: (07) 373 57514 ABSTRACT Graphene quantum dots (GQDs), a nano version of graphene whose interesting properties that distinguish them from bulk graphene, have recently received significant scientific attention. The quantum confinement effect referring to the size-dependence of physical and chemical properties opens great possibility in the practical applications of this material. However, tuning the size of graphene quantum dots is still difficult to achieve. Here, an edge-etching mechanism which is able to tune the size of GQDs in a quasi-continuous manner is discovered. Different from the ‘unzipping’ mechanism which has been adopted to cut bulk graphitic materials into small fragments and normally cut through the basal plane along the ‘zig-zag’ direction where epoxy groups reside, the mechanism discovered in this research could gradually remove the peripheral carbon atoms of nano-scaled graphene (i.e. GQDs) due to the higher chemical reactivity of the edge carbon atoms than that of inner carbon atoms thereby tuning the size of GQDs in a quasi-continuous fashion. It enables the facile manipulate of the size and properties of GQDs through controlling merely the reaction duration. It is also believed the as discovered mechanism could be generalized for synthesizing various sizes of GQDs from other graphitic precursors (e.g. carbon fibres, carbon nanotubes, etc). INTRODUCTION Recently, a nano-scaled carbon material, graphene quantum dots (GQDs) referring to graphene fragments or discs normally having lateral size less than 100nm [1] has been attracting increasing attention in a variety of fields including single-electron transistors [2-4], spintronics [5, 6], energy conversion [7, 8], memory [9, 10], optoelectronics [11], sensing [12-15] and bioimaging [16-20] etc. The emergence of this material could be attributed to its interesting properties such as tuneable electronic and magnetic properties, photoluminescence, low cytotoxity1 [21-27], etc. that distinguish themselves from bulk graphene.
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Although GQDs have been investigated theoretically even before the discovery of g
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