Manifesting Epoxide and Hydroxyl Groups in XPS Spectra and Valence Band of Graphene Derivatives

Abstract

The derivatization of graphene to engineer its band structure is a subject of significant attention nowadays, extending the frames of graphene material applications in the fields of catalysis, sensing, and energy harvesting. Yet, the accurate identification of a certain group and its effect on graphene’s electronic structure is an intricate question. Herein, we propose the advanced fingerprinting of the epoxide and hydroxyl groups on the graphene layers via core-level methods and reveal the modification of their valence band (VB) upon the introduction of these oxygen functionalities. The distinctive contribution of epoxide and hydroxyl groups to the C 1s X-ray photoelectron spectra was indicated experimentally, allowing the quantitative characterization of each group, not just their sum. The appearance of a set of localized states in graphene’s VB related to the molecular orbitals of the introduced functionalities was signified both experimentally and theoretically. Applying the density functional theory calculations, the impact of the localized states corresponding to the molecular orbitals of the hydroxyl and epoxide groups was decomposed. Altogether, these findings unveiled the particular contribution of the epoxide and hydroxyl groups to the core-level spectra and band structure of graphene derivatives, advancing graphene functionalization as a tool to engineer its physical properties.

Toward On-Chip Multisensor Arrays for Selective Methanol and Ethanol Detection at Room Temperature: Capitalizing the Graphene Carbonylation

“…This resonance is either not presented or hardly distinguishable in the X-ray absorption spectra of the pristine rGO or the initial GO. In turn, π*- and σ*-resonances of the C–OH groups centered at hv = 286.2 eV and at hv = 289.6 eV, respectively, initially presented in the GO spectrum disappear, verifying the aforementioned elimination of basal plane oxygen groups …”

“…Despite the almost entire absence of basal-plane oxygen groups, the degree of π-conjugation in C-ny graphene is found to be substantially low. This fact is captured in a low-intensive and broadened π* resonance of CC bonds centered at hv = 285.1 eV and the absence of a distinguishable σ*-exciton resonance centered at hv = 291.65 eV, which are two common signs of graphene network to be presented by localized domains with a low π-conjugation length. , Conversely, the rGO spectrum is composed of prominent π*-resonance and a well-defined σ*-exciton owing to the presence of extensive areas of the π-conjugated graphene network.…”

Graphene Amination towards Its Grafting by Antibodies for Biosensing Applications

“…Figure 2a displays the C K-edge X-ray absorption spectra of the studied materials. The reductive amination of the GO resulted in the vanishing of a set of resonances contributed by the C 1s-π* or C 1s-σ* electron transitions in the edge-located C-OH, basal-plane C-OH and C=O/COOH groups and centered at hv = 286.5 eV, hv = 289.8 eV and hv = 288.2 eV, respectively [42,45,46]. In turn, the C 1s-π* resonance at hv = 284.8 eV, which matures from the electron transitions in the C = C bonds at pristine sp 2 -domains, shifts towards hv = 285.1 eV with an increase in its ratio to the σ*-resonance of the graphene lattice (C 1s-σ* peak) from 0.57 to 0.78.…”

Advanced Carbon Nanostructures: Synthesis, Properties, and Applications

“…The papers presented with discuss aspects of synthesis, sorting, functionalization, and characterization of chemical and physical properties, leading to many interesting applications being highlighted and experimental, theoretical, and modelling aspects being discussed. In the Special Issue, 15 papers were published, consisting of 2 reviews [ 4 , 5 ] and 13 research papers [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”

“…In [ 7 ], the authors performed photoemission spectroscopy studies of graphene. The contribution of epoxide and hydroxyl groups in C 1s X-ray photoelectron spectra were experimentally revealed.…”