Evolution of Surface Functional Groups in a Series of Progressively Oxidized Graphite Oxides

Abstract

This study contributes to the sustained effort to unravel the chemical structure of graphite oxide (GO) by proposing a model based on elemental analysis, transmission electron microscopy, X-ray diffraction, 13C magic-angle spinning NMR, diffuse reflectance infrared Fourier transform spectroscopy, X-ray photoelectron spectroscopy, and electron spin resonance investigations. The model exhibits a carbon network consisting of two kinds of regions (of trans linked cyclohexane chairs and ribbons of flat hexagons with CC double bonds) and functional groups such as tertiary OH, 1,3-ether, ketone, quinone, and phenol (aromatic diol). The latter species give clear explanation for the observed planar acidity of GO, which could not be interpreted by the previous models. The above methods also confirmed the evolution of the surface functional groups upon successive oxidation steps.

Intercalation and Stitching of Graphite Oxide with Diaminoalkanes

“…This spectrum is reminiscent of pristine graphite, which has two IRactive modes: a signal at 1571 cm -1 , attributed to the in-plane E 1u mode, and a signal at 868 cm -1 , assigned to the out-of-plane A 2u mode. [34][35][36][37] The latter signal is not observed in the spectra presented in Figure 5 since it is generally of lower intensity and difficult to observe. The signal at 1571 cm -1 shows broadening toward lower energy, which has been attributed to increased disorder, bending of the graphite sheets, and a change in the interplanar bonding.…”

“…The Scholz-Boehm GO model 5 (recently advocated by Szabo et al 34 ) contains sp 2 ribbons with a rigid quinoidal structure (similar to R1 in Figure 5a). Since these ribbons are the narrowest possible, the double bonds are all isolated.…”

Unique synthesis of graphene-based materials for clean energy and biological sensing applications

“…Compared with GO made by Hummers' method, the mildly oxidized GO contains fewer defects and can be used to prepare highly conductive graphene by chemical reduction. GO is a nonstoichiometric compound of carbon, oxygen and hydrogen in variable ratio, which is dependent on the synthesis method and degree of oxidation [65,66]. The chemical structure of GO is often assumed to be a graphene sheet bonded to oxygen-containing functionalities including epoxide and hydroxyl groups on the basal plane and carbonyl and carboxyl groups at the edges [28,65].…”

“…GO is a nonstoichiometric compound of carbon, oxygen and hydrogen in variable ratio, which is dependent on the synthesis method and degree of oxidation [65,66]. The chemical structure of GO is often assumed to be a graphene sheet bonded to oxygen-containing functionalities including epoxide and hydroxyl groups on the basal plane and carbonyl and carboxyl groups at the edges [28,65]. These functional groups make GO hydrophilic, which allow it to disperse effectively in some polar solvents such as water, alcohol and DMF [67].…”

Removal of acridine orange from water by graphene oxide

“…GO is an oxygen-rich carbonaceous material obtained through the oxidation of graphite with strong oxidants [26]. It consists of randomly distributed regions of unoxidised (aromatic) graphene and regions of aliphatic six-membered rings, rich in oxygen-containing functional groups, including epoxies, hydroxyls and carboxylic groups [28][29][30], reported to be good adsorbent for water contaminated [18][19][20][21][22][23][24]. However, few investigations have been reported about adsorption of AO on graphene oxide.…”