Theoretical X-ray absorption spectroscopy database analysis for oxidised 2D carbon nanomaterials.

Fabian Weber,Jian Ren,Tristan Petit,Annika Bande

doi:10.1039/c8cp06620e

Abstract

In this work we provide a proof of principle for a theoretical methodology to identify functionalisation patterns in oxidised carbon 2D nanomaterials. The methodology is based on calculating a large number of X-ray absorption spectra of individually excited carbon atoms in different chemical environments using density functional theory. Since each resulting spectrum gives a fingerprint of the local electronic structure surrounding the excited atom, we may relate each spectrum to the functionalisation pattern of that excited atom up to a desired neighbourhood radius. These functionalisation pattern-specific spectra are collected in a database, that allows fast composition of X-ray absorption spectra for arbitrary structures in density functional theory quality. Finally, we present an exemplary application of the database approach to estimate the relative amount of functional groups in two different experimental samples of carbon nanomaterials.

Highlights

The mission of finding possible local functionalisation patterns is ongoing research in various fields of physical, analytical and theoretical chemistry in which many different structural models have been proposed over the course of time.[15,16,17,18,19] Some of the milestones that show the complementary nature of this structural analysis can be summed up as follows: with its first reported syntheses, elemental analyses were conducted that confirmed the non-stoichiometric character of graphite oxide.[8]
With this work we present a proof of principle for a functionalisation dependent C K-edge X-ray absorption (XA) spectra database methodology based on quantum chemistry calculations with the aim to understand and predict XA spectra of graphitic materials
As the resulting spectra are approximately defined by the local environment of the excited carbon atoms, group descriptors are assigned to each carbon atom based on a cutoff radius

Summary

Introduction

The mission of finding possible local functionalisation patterns is ongoing research in various fields of physical, analytical and theoretical chemistry in which many different structural models have been proposed over the course of time.[15,16,17,18,19] Some of the milestones that show the complementary nature of this structural analysis can be summed up as follows: with its first reported syntheses, elemental analyses were conducted that confirmed the non-stoichiometric character of graphite oxide.[8] Following the advent of X-ray powder diffraction, the comparison with powder diffraction images of graphite lead to the conclusion that the carbon network of six-membered rings was mostly preserved. Further improvements to their structural model have been made since, by SSNMR of 13C enriched samples[12] and high-resolution transmission electron microscopy images.[26]

Methods

Results

Conclusion