Abstract:Recently, aromatic molecules have been stacked on graphene for applications in biosensors and chemical sensors, although the interaction between them is not well understood. In this paper, we use electrostatic model, double charge rings, and its image charges model to simulate the π–π interaction between benzene and a graphene layer. Furthermore, the results of our model are confirmed by the numerical results from density functional theory and experimental reviews. This model has potential for use in predictin… Show more
“…In both graphene and GY, PAHs are adsorbed at intermolecular distances in the range of d inter = 3.4 − 3.6 Å. At these equilibrium distances, the adsorption of neutral aromatic molecules onto the aromatic and regular graphene lattices (in addition to the graphene/graphyne interactions) is due to the cooperative interplay between π⋅⋅⋅π, short‐range electrostatic Coulombic interactions, Pauli repulsion and van der Waals interactions . In this respect, the porous character of GY is expected to decrease the adsorption strength as a result of its decreased π−system compared to graphene.…”
Section: Resultsmentioning
confidence: 99%
“…Note that low density BCPs are associated with weak long‐range electrostatic interactions in the AIM scheme. Therefore, these BCPs give evidence that electrostatic interactions play a key role in the adsorption strength of PAHs onto graphyne and graphene surfaces, in agreement with theoretical studies of graphene systems …”
Density functional theory calculations were implemented to expand the knowledge about graphyne and its interaction with polycyclic aromatic hydrocarbons (PAHs). Due to the porous character of graphyne, the adsorption strength of PAHs onto graphyne surfaces is expected to be lower with respect to graphene (a perfect p-extended system). However, there are not quantitative evidences for this assumption. This work shows that the adsorption strength of adsorbed PAHs onto g-graphyne nanosheets (GY) is weakened in 12 2 23% with respect to the adsorption onto graphene, with a decrease of 10 2 20% in the dispersive interactions. The adsorption energies (in eV) of the GY-PAH systems can be straightforward obtained as E ads /eV%0.033N H 1 0.031N C , where N H and N C is the number of H and C atoms in the aromatic molecule, respectively. This equation predicts the binding energy of graphene-graphyne bilayers with a value of $31 meV/atom. Analysis of the electronic properties shows that PAHs behaves as n-dopants for GY, introducing electrons in GY and also reducing its bandgap in up to $0.5 eV. Strong acceptor or donor substituted PAHs decrease the bandgap of g-graphyne in up to $0.8 eV, with changes in its valence or conduction band, depending on the chemical nature of the adsorbate. Finally, these data will serve for future studies related to the bandgap engineering of graphyne surfaces by nonaggressive molecular doping, and for the development of graphyne-based materials with potential applications in the removal of persistent aromatic pollutants. K E Y W O R D S adsorption, bandgap, graphene, graphyne, polycyclic aromatic hydrocarbons Int J Quantum Chem 2017;117:e25346.
“…In both graphene and GY, PAHs are adsorbed at intermolecular distances in the range of d inter = 3.4 − 3.6 Å. At these equilibrium distances, the adsorption of neutral aromatic molecules onto the aromatic and regular graphene lattices (in addition to the graphene/graphyne interactions) is due to the cooperative interplay between π⋅⋅⋅π, short‐range electrostatic Coulombic interactions, Pauli repulsion and van der Waals interactions . In this respect, the porous character of GY is expected to decrease the adsorption strength as a result of its decreased π−system compared to graphene.…”
Section: Resultsmentioning
confidence: 99%
“…Note that low density BCPs are associated with weak long‐range electrostatic interactions in the AIM scheme. Therefore, these BCPs give evidence that electrostatic interactions play a key role in the adsorption strength of PAHs onto graphyne and graphene surfaces, in agreement with theoretical studies of graphene systems …”
Density functional theory calculations were implemented to expand the knowledge about graphyne and its interaction with polycyclic aromatic hydrocarbons (PAHs). Due to the porous character of graphyne, the adsorption strength of PAHs onto graphyne surfaces is expected to be lower with respect to graphene (a perfect p-extended system). However, there are not quantitative evidences for this assumption. This work shows that the adsorption strength of adsorbed PAHs onto g-graphyne nanosheets (GY) is weakened in 12 2 23% with respect to the adsorption onto graphene, with a decrease of 10 2 20% in the dispersive interactions. The adsorption energies (in eV) of the GY-PAH systems can be straightforward obtained as E ads /eV%0.033N H 1 0.031N C , where N H and N C is the number of H and C atoms in the aromatic molecule, respectively. This equation predicts the binding energy of graphene-graphyne bilayers with a value of $31 meV/atom. Analysis of the electronic properties shows that PAHs behaves as n-dopants for GY, introducing electrons in GY and also reducing its bandgap in up to $0.5 eV. Strong acceptor or donor substituted PAHs decrease the bandgap of g-graphyne in up to $0.8 eV, with changes in its valence or conduction band, depending on the chemical nature of the adsorbate. Finally, these data will serve for future studies related to the bandgap engineering of graphyne surfaces by nonaggressive molecular doping, and for the development of graphyne-based materials with potential applications in the removal of persistent aromatic pollutants. K E Y W O R D S adsorption, bandgap, graphene, graphyne, polycyclic aromatic hydrocarbons Int J Quantum Chem 2017;117:e25346.
“…In contrast, the TEM image shows rGO sheets have stacked together and form thick clusters (Supplementary Figure S1). It is worth mentioning that there is no covalent bonding between pyranine and graphene in the supramolecular assembly because the π-π interaction is a physical phenomenon driven by the electrostatic force rather than chemical reaction 25 , i.e . the modification would not disrupt the structure and electronic conjugation of graphene 26 .Figure 1( a ) The schematic of the aggregation by stacked rGO sheets and the supramolecular assembly of Pyr-rGO sheets with corresponding physical images in dispersion.…”
A facile one-step supramolecular assembly method is adopted to modify reduced graphene oxide (rGO) with functional organic molecule pyranine for achieving comprehensive humidity sensing performance. The fabricated humidity sensor based on pyranine modified-reduced graphene oxide (Pyr-rGO) exhibits excellent sensing performance with ultrafast (<2 s) and ultrahigh response of IL/IH = 6000 as relative humidity (RH) consecutively changes between 11% and 95%; small hysteresis of 8% RH; reliable repeatability and stability. In addition, a detailed mechanism analysis is performed to investigate the difference in water adsorption and ions transfer under various RH levels. Notably, the one-step supramolecular assembly method to prepare Pyr-rGO provides a new insight into developing novel functional humidity sensing materials with enhanced device performance.
“…[13,14] A new scientific frontier has been explored since the discovery of graphene. This nanomaterial attracts researchers, in both fundamental science and applied technology, [15][16][17] for several reasons. Graphene is the first truly 2D material, [12,18] which can serve as an ideal platform for realizing low-dimensional physics and applications.…”
A review work is done for the electronic and optical properties of graphene nanoribbons in magnetic, electric, composite, and modulated fields. Effects due to the lateral confinement, curvature, stacking, non-uniform subsystems and hybrid structures are taken into account. The special electronic properties, induced by complex competitions between external fields and geometric structures, include many one-dimensional parabolic subbands, standing waves, peculiar edge-localized states, width- and field-dependent energy gaps, magnetic-quantized quasi-Landau levels, curvature-induced oscillating Landau subbands, crossings and anti-crossings of quasi-Landau levels, coexistence and combination of energy spectra in layered structures, and various peak structures in the density of states. There exist diverse absorption spectra and different selection rules, covering edge-dependent selection rules, magneto-optical selection rule, splitting of the Landau absorption peaks, intragroup and intergroup Landau transitions, as well as coexistence of monolayer-like and bilayer-like Landau absorption spectra. Detailed comparisons are made between the theoretical calculations and experimental measurements. The predicted results, the parabolic subbands, edge-localized states, gap opening and modulation, and spatial distribution of Landau subbands, have been identified by various experimental measurements.
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