First Principles NMR Signatures of Graphene Oxide

TL;DR

This study uses first principles $^{13}$C NMR calculations to elucidate the relationship between NMR spectral features and the atomic structure of graphene oxide, providing insights into its structural configurations.

Contribution

The paper introduces a first-principles approach to connect NMR chemical shifts with specific atomic environments in graphene oxide, clarifying structural ambiguities.

Findings

Chemical shifts are highly sensitive to local atomic environments.

Hydroxy chain structures are unlikely in real GO samples.

Epoxy pair configurations are supported by chemical shift calculations.

Abstract

Nuclear magnetic resonance (NMR) has been widely used in the graphene oxide (GO) structure study. However, the detailed relationship between its spectroscopic features and the GO structural configuration has remained elusive. Based on first principles $^{13}$C chemical shift calculations using the gauge including projector augmented waves (GIPAW) method, we provide a spectrum-structure connection. Chemical shift of carbon is found to be very sensitive to atomic environment, even with an identical oxidation group. Factors determining the chemical shifts for epoxy and hydroxy groups have been discussed. GO structures previously reported in the literature have been checked from the NMR point of view. The energetically favorable hydroxy chain structure is not expected to be widely existed in real GO samples according to our NMR simulations. The epoxy pair we proposed previously is also supported by chemical shift calculations.