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Synthesis of Large Area Graphene Flakes with Low Defect Density Using the Electrochemical Exfoliation Technique

Thursday, 2 June 2016: 17:00
Aqua 311 A (Hilton San Diego Bayfront)
A. Mir and A. Shukla (Indian Institute of Technology Delhi)
Ever since the discovery of graphene in 2004 by Novoselov and Geim, the researchers across the globe have been in search for a cheap scalable method for bulk production of good quality graphene films. Electrochemical exfoliation has lately emerged as one of the strongest contenders for large scale production of graphene with focus being on the production of uniformly distributed monolayer graphene flakes preferably covering a larger area [Max reported flake size of 10 µm (Parvez et al, JACS, 2014)]. In this work, we demonstrate a method for synthesis of monolayer graphene films with flake sizes as large as 30 × 30 µm2. This can be achieved by making a proper choice of solvent for dispersing the graphene flakes. Over 25 solvents have been studied to determine the factors affecting the greater dispersibility of electrochemically exfolaited graphene flakes and hence achieving a larger flake size. UV-vis spectroscopy was performed to find the concentration of dispersed graphene flakes. Raman spectroscopy was done to determine the defects present in the sample as well as to rule out any oxidation of graphene layers in the presence of strong oxidants during the electrochemical exfoliation. In order to further reduce the defects in the graphene films, ultrasonication times for dispersing graphene flakes in the solvent have been reduced to as low as 2 min. Using this technique the best results were obtained for Propylene Carbonate in which single layer graphene flakes with 20 × 20 µm2 area with low defect ratio (ID/IG = 0.16) was synthesized as shown in the figure. Graphene produced via his route finds huge applications in various fields like synthesis of highly conductive electrodes.