Synthesis and Solid-State NMR Structural Characterization of ¹³ C-Labeled Graphite Oxide

Abstract

The detailed chemical structure of graphite oxide (GO), a layered material prepared from graphite almost 150 years ago and a precursor to chemically modified graphenes, has not been previously resolved because of the pseudo-random chemical functionalization of each layer, as well as variations in exact composition. Carbon-13 (13C) solid-state nuclear magnetic resonance (SSNMR) spectra of GO for natural abundance 13C have poor signal-to-noise ratios. Approximately 100% 13C-labeled graphite was made and converted to 13C-labeled GO, and 13C SSNMR was used to reveal details of the chemical bonding network, including the chemical groups and their connections. Carbon-13-labeled graphite can be used to prepare chemically modified graphenes for 13C SSNMR analysis with enhanced sensitivity and for fundamental studies of 13C-labeled graphite and graphene.

Chemical structures of hydrazine-treated graphene oxide and generation of aromatic nitrogen doping

“…Raman spectroscopy confirmed that the as-grown graphite film was of high quality and highly enriched (99%) in the 13 C isotope ( Supplementary Fig. S1) 18 . As expected, the first-order G-band was observed at 1,518 cm − 1 , while the D-band typically detected at 1,297 cm − 1 was completely absent.…”

“…A 13 C-labelled graphite film was grown by CVD of 13 C-enriched methane on Ni foil as described previously 18 . Raman spectroscopy confirmed that the as-grown graphite film was of high quality and highly enriched (99%) in the 13 C isotope ( Supplementary Fig.…”

“…However, the low natural abundance (1.1%) of the 13 C isotope results in a low signal-to-noise ratio, which, along with the broad peaks typically observed from CMGs, precludes the use of multidimensional SSNMR. This was the motivation for our recent work, which used 99% 13 C-labelled graphite made by chemical vapour deposition (CVD) as the precursor to 13 C-labelled GO, which was studied using 13 C SSNMR 18,19 . This investigation revealed that hydroxyl, 1,2-epoxide and sp 2 carbons on the basal planes 20 are directly bonded to each other in GO.…”

“…13 C mAs ssnmR spectra of (a) 13 C-labelled Go and (b) 13 C-and 15 n-labelled RGo. The spectrum in a was reproduced from Figure 1a in our previous work by Cai et al 18 Reprinted with permission from AAAs. All the spectra were obtained with direct 13 C excitation by a π/2 pulse at a 13 C nmR frequency of 100.643 mHz and with 20 kHz mAs.…”

“…High-resolution SSNMR spectroscopy using MAS has been used to study the chemical structures of GO 3,18,22 . A spectrum of the labelled RGO sample (Fig.…”