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Open AccessArticle

Core Level Spectra of Organic Molecules Adsorbed on Graphene

1
Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via Cozzi, 55, 20125 Milano, Italy
2
Dipartimento di Fisica, Università degli Studi di Milano, via Celoria, 16, 20133 Milano, Italy
*
Author to whom correspondence should be addressed.
Materials 2018, 11(4), 518; https://doi.org/10.3390/ma11040518
Received: 15 March 2018 / Revised: 27 March 2018 / Accepted: 27 March 2018 / Published: 29 March 2018
(This article belongs to the Special Issue Hard and Soft Hybrid Functional Materials)
We perform first principle calculations based on density functional theory to investigate the effect of the adsorption of core-excited organic molecules on graphene. We simulate Near Edge X-ray absorption Fine Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) at the N and C edges for two moieties: pyridine and the pyridine radical on graphene, which exemplify two different adsorption characters. The modifications of molecular and graphene energy levels due to their interplay with the core-level excitation are discussed. We find that upon physisorption of pyridine, the binding energies of graphene close to the adsorption site reduce mildly, and the NEXAFS spectra of the molecule and graphene resemble those of gas phase pyridine and pristine graphene, respectively. However, the chemisorption of the pyridine radical is found to significantly alter these core excited spectra. The C 1s binding energy of the C atom of graphene participating in chemisorption increases by ∼1 eV, and the C atoms of graphene alternate to the adsorption site show a reduction in the binding energy. Analogously, these C atoms also show strong modifications in the NEXAFS spectra. The NEXAFS spectrum of the chemisorbed molecule is also modified as a result of hybridization with and screening by graphene. We eventually explore the electronic properties and magnetism of the system as a core-level excitation is adiabatically switched on. View Full-Text
Keywords: core excited spectra; organic molecules on graphene; magnetism in graphene core excited spectra; organic molecules on graphene; magnetism in graphene
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MDPI and ACS Style

Ravikumar, A.; Brivio, G.P.; Fratesi, G. Core Level Spectra of Organic Molecules Adsorbed on Graphene. Materials 2018, 11, 518.

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