High-yield production of N-doped graphitic platelets by aqueous exfoliation of pyrolyzed chitosan

Abstract

Full exploitation of the properties of N-doped graphene and few-layers graphitic platelets will require a method for the mass production of this highly conductive material. Herein the preparation of few-layers graphitic platelet dispersions at concentrations up to 0.16mgml−1 is reported. These suspensions are produced by dispersion and exfoliation of N-doped graphitic carbons obtained from the chitosan biopolymer. This high concentration derives from the morphology of pyrolyzed chitosan constituted by a graphitic carbonaceous residue with loose stacking of the graphene sheets that is prone to undergo easy exfoliation. The presence of few layers graphitic sheets was confirmed by Raman spectroscopy, transmission electron microscopy, electron diffraction and atomic force microscopy. Our method results in the formation of N-doped graphitic platelet suspensions with a yield of 40wt.% of the initial graphitic carbon, which could potentially be improved to 90wt.% by four consecutive sonication–centrifugation cycles of the same pyrolyzed chitosan residue. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. Solution processing of graphene and few-layers graphitic flakes opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry.