Binding Energy on Graphene

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First principles investigation on the electronic efficiency and binding energy of the contacts formed by graphene and poly aromatic hydrocarbon anchoring groups

First principles investigation on the electronic efficiency and binding energy of the contacts formed by graphene and poly aromatic hydrocarbon anchoring groups

Nitrogen dopants a ff ect only slightly the adsorption of polyacenes in the interior or at the edge of graphene. Taking anthracene as an example, both the inter-planar distance and the binding energy are very close to those calculated for clean graphene, at least as long as the bonding sites are far away from a nitrogen atom. Even when the anthracene molecule is directly above a nitrogen atom, the inter-planar distance is only decreased by 0.03 Å and the binding energy is increased by 0.03 eV. Fig. 4(a) presents the device model for N-doped graphene electrodes, in which the two anthracene groups are located far away from the nitrogen dopants in order to minimize their e ff ects on the binding configuration. The equi- librium transmission spectra with naphthalene, anthracene, pentacene, and an infinite polyacene as the anchoring groups are, respectively, given in Figures 4(b)–4(e). As the number of fused benzene rings increases, the transmission coe ffi cient around the Fermi level increases substantially; for pentacene, T ( E F ) reaches 10 −3 . This is comparable to the measured low-

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Modeling Enhanced Adsorption of Explosive Molecules on a Hydroxylated Graphene Pore

Modeling Enhanced Adsorption of Explosive Molecules on a Hydroxylated Graphene Pore

The possibility of a graphene bilayer nanosensor for the detection of explosive molecules was modeled using computational chemistry. A pore was designed on a graphene bilayer structure with three strategically placed perimeter hy- droxyl (OH) groups built around the edge of an indented, two-dimensional hexagonal pore. This hydroxylated pore and models of various explosive mo- lecules were optimized using MM2 molecular mechanics parameters. Values were calculated for the molecule-surface interaction energy (binding energy), E, for 22 explosive molecules on a flat graphene bilayer and on the specially designed hydroxylated pore within the bilayer. The molecule-surface binding energy for trinitrotoluene (TNT) increased from 17.9 kcal/mol on the flat graphene bilayer to 42.3 kcal/mol on the hydroxylated pore. Due to the common functionality of nitro groups that exist on many explosive mole- cules, the other explosive molecules studied gave similar enhancements based on the specific hydrogen bonding interactions formed within the pore. Each of the 22 explosive adsorbate molecules showed increased molecule-surface interaction on the bilayer hydroxylated pore as compared to the flat bilayer. For the 22 molecules, the average E for the flat graphite surface was 15.8 kcal/mol and for the hydroxylated pore E was 33.8 kcal/mol. An enhance- ment of adsorption should make a detection device more sensitive. Nanosen- sors based on a modified graphene surface may be useful for detecting ex- tremely low concentrations of explosive molecules or explosive signature molecules.

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Analysis of energy gap opening in graphene oxide

Analysis of energy gap opening in graphene oxide

orbitals causes vertical displacement of the C atoms from their 2D hexagonal lattice sites, as shown in Fig. 1(b). The binding energy per O adatom, calculated relative to the energy of a free O atom, is 3.38 eV, which indicates the structure to be highly stable. The mean C-O bond length is 0.15 ˚ A, while the C atoms are displaced vertically by 0.16 ˚ A relative to their positions in the honeycomb lattice of graphene. The sp 2 to sp 3 bond rehybridisation also causes substantial changes to the band structure, depicted in Fig. 2(a), in comparison to that of pristine graphene. This, along with the total density of states plotted in Fig. 2(b), clearly identify fully oxidised graphene to be an insulator, with a band gap of 6.50 eV, as calculated using B3LYP. As can be expected, the gap predicted by pure ab initio theory, using the PBE functional, is much smaller at 4.09 eV. The effective masses along the direction Γ → M are predicted as m ∗ e = 1.36 m 0 and

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Double-sided F and Cl adsorptions on graphene at various atomic ratios: Geometric, orientation and electronic structure aspects

Double-sided F and Cl adsorptions on graphene at various atomic ratios: Geometric, orientation and electronic structure aspects

without barrier energy. This is supported by Nakada and Ishii’s calculation [29], which stated that migration energy for Cl-adsorbed graphene is minimal (0.02 eV). Our previous study [5] also supports this and we concluded that non-bonding Cl-adsorbed graphene is basically site- independent. Furthermore, Şahin and co-researchers also reported that bonding configuration is dynamically stable at 0 K and possibly at room temperature, but with graphene lattice expansion of more than 15%. Using the binding energy formula (Eq. 1), our results show that there is competition between bonding and non-bonding configuration, which non-bonding wins at 50% to 75% atomic ratios. At these atomic ratios, the adsorption becomes weak (physisorbed), as indicated by the decreasing binding energies, large adatom heights are approximately 3.50 Å, zero band gaps at Fermi energy and miniscule charge transfers (Fig. 9). As we did not calculate the migration energies, our calculation for CCl is in agreement with the non-bonding calculation of Medeiros and co-researchers.

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Conductance of Graphene Nanoribbon Junctions and the Tight Binding Model

Conductance of Graphene Nanoribbon Junctions and the Tight Binding Model

In this paper, we simulate charge transport in a gra- phene nanoribbon and a nanoribbon junction using a NEGF based on a third nearest-neighbour tight binding energy dispersion. For transport studies in nanoribbons and junctions, the formulation of the problem differs from that required for bulk graphene. Third nearest- neighbour interactions introduce additional exchange and overlap integrals significantly modifying the Green ’ s function. Calculation of device characteristics is facili- tated by the inclusion of a Sancho-Rubio [11] iterative scheme, modified by the inclusion of third nearest- neighbour interactions, for the calculation of the self- energies. We find that the conductance is significantly altered compared with that obtained based on the nearest-neighbour tight binding dispersion even in an isolated nanoribbon. Hong et al. [12] observed that the conductance is modified (increased as well as decreased) by the presence of defects within the lattice. Our results show that details of the band structure can significantly modify the observed conductivities when defects are included in the structure.

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The dependence of the measured surface energy of graphene on nanosheet size

The dependence of the measured surface energy of graphene on nanosheet size

The advantage of the SEA is that it can accurately control the coverage of probe molecules on the surface. This is achieved by the controlling probe injection time which relates to the surface coverage. One must consider both the actual and targeted surface coverage, where the target is related to the ideal injection time (based on the specific surface area of the sample) and the actual is associated with the measured injected quantity. In the experiments carried out here, the difference between target and actual surface coverage is no more than 10%. This allows the SEA to measure so-called surface energy profiles, i.e. the surface energy as a function of probe coverage. This is termed finite-dilution IGC (FD-IGC),(33) and is important because it facilitates the characterisation of not just high energy sites but also sites with lower probe- surface binding energy. Such sites become important only as the probe coverage is increased. Thus, a typical surface energy profile shows a high surface energy value at low coverage due to the presence of high energy sites. However, at the coverage increases, the surface energy drops off, as the probe molecules begin to access the low energy sites.

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Electronic Properties and Stability of Graphene Oxyradical Systems

Electronic Properties and Stability of Graphene Oxyradical Systems

protections to the O-bonding compared with other noncentral positions, and moreover, this is also easily understandable obviously. In order to testify the opinion about “safe harbor” of central O-bonding position, we simulated the destroying of the zigzag edge central status by outer effect and then studied the stability changes of the new graphene oxyradical systems. Taking 6a6z graphene oxyradical as an example, we fold 6a6z graphene along an axis at z3 position perpendicular to zigzag edge as shown in Fig. 4 and the angle between two partial graphene planes is 90° after folding. Then, we calculate the current single point energy of z1-6 positions with O-bonding to zigzag edge. The result shows that the z3 position is no longer the lowest energy position and z4 position replaces it. The energy of 6a6z-z1 and 6a6z-z6 positions is still the highest indicating their most unstable status. The folding of graphene plane can be understood as the deformation caused by the outer force, defects or other factors. Although the present folding with angle of 90° is a special deformation case and not the practically models, it

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Adsorbate induced curvature and stiffening of graphene

Adsorbate induced curvature and stiffening of graphene

graphene. (e) TTC on G/mica. The lamellar structure runs continuously across several 100 nm and over terrace edges introduced by water layers. Scale bar: 60 nm (−1 V, 0.15 nA). (f) TTC on G/ mica. Strong anisotropy of the shape of trapped water is apparent in areas where more than three layers of water are trapped. Scale bar: 10 nm (−1 V, 0.15 nA). Inset: Fourier transform of image showing an elliptical central spot indicating deformation of underlying graphene; the molecular structure along the lamellae gives rise to the spots identi fi ed by arrows; inverse length scale bar 1 nm −1 . (g) Pro fi le along marked line in (e) showing step heights across water layer. (h) Histogram of heights for di ff erent number of water layers trapped at the G/mica interface indicating an increasing roughness for a higher number of trapped water layers. (i) Di ff erential image of TTC on G/ mica with >3 layers of water showing that the expected molecular arrangement within the lamellar rows; the undi ff erentiated image is included in Supporting Information. Scale bar: 6 nm (−1 V, 0.15 nA).

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Covalently binding atomically designed Au9 clusters to chemically modified graphene

Covalently binding atomically designed Au9 clusters to chemically modified graphene

minimize damage to the chemically modified graphene by the electron beam. At this acceleration voltage the clusters are fixed in each orientation for timescales of the order of seconds before switching to another orientation. This indicates that each observed orientation is metastable, corresponding to a local energy minimum. As each image shows well defined spots rather than blurred streaks, it is also clear that the transition between orientations must be relatively rapid.

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The Role of Pion Cloud in the Structure Function and the EMC Effect of 27Al, 56Fe, 63Cu and, 107Ag nuclei

The Role of Pion Cloud in the Structure Function and the EMC Effect of 27Al, 56Fe, 63Cu and, 107Ag nuclei

Where 34 2 ~ 678 6 is the fine structure constant, four-- momentum transfer squared is . Initial and scattered lepton energies are and , , respectively. Energy of the virtual photon is 1 * , , and 9 :; is Bjorken scal- ing variable. $ is the nucleon rest mass. < is the detected lepton scattering angle. # and are the deep inelastic structure functions.

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AN EVALUATION OF BINDING ENERGY OF NANO DOT AS A FUNCTION OF DOT RADIUS AT DIFFERENT CONCENTRATIONS

AN EVALUATION OF BINDING ENERGY OF NANO DOT AS A FUNCTION OF DOT RADIUS AT DIFFERENT CONCENTRATIONS

evaluated the binding energy as a function of dot size for different concentrations. Our theoretically evaluated result shows that binding energy decreases with increase of dot radius with fixed concentration. In another calculation, binding energy of quantum dots increases linearly with concentration x with fixed dot radius. These observations are compared with other theoretical workers. 22-25

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An experimental investigation of metal phthalocyanine germanium interfaces

An experimental investigation of metal phthalocyanine germanium interfaces

P hotoelectron spectroscopy (PES) is a well established technique which yields inform ation about electronic stru c tu re and bonding a t surfaces and in the near surface bulk. The energy spectrum of electrons em itted by the photoelectric effect, due to absorbed m onochrom atic photons yields inform ation ab o u t th e bound sta te of these electrons. PES is often divided into two m ain cate­ gories depending on the energy of photons used. W hen conducted w ith low energy photons it is typically called ultra-violet photoelectron spectroscopy (UPS), providing a tool for analysis of th e loosely bound valence states. W ith higher energies it is typically called X-ray photoelectron spectroscopy (X PS) or, historically, electron spectroscopy for chemical analysis (ESCA). This allows for the analysis of the tightly bound core states, and provides a elem entally sensitive technique for analysing surface and bulk electronic states. W hen conducted w ith synchrotron rad iatio n it is com m only referred to as soft X-ray photoelectron spectroscopy (SXPS).

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Critical Delocalization of Chiral Zero Energy Modes in Graphene

Critical Delocalization of Chiral Zero Energy Modes in Graphene

take a fine broadening η ¼ 2 . 5 meV so as to guarantee that L ( is sufficiently large to capture any marked localization trend near the Dirac point. Our results are summarized in Fig. 4. Away from the band center the conductivity is strongly decaying with n i as expected. For instance, at E ¼ 0 . 1 eV — a typical Fermi energy in experiments — the conductivity swiftly enters in the strong localized regime already for dilute concentrations n i ≈ 0 . 2% . The depend- ence of σðEÞ with L ( is well fitted by an exponential law σ ∝ e −L ( =ξ ( ; see top panel. (The dependence of ξ

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Dynamical tuning of energy transfer efficiency on a graphene monolayer

Dynamical tuning of energy transfer efficiency on a graphene monolayer

and it occurs between the energies ω = μ and ω = 2μ. This drop is due to interband transitions when the QE relaxes through lossy channels. At emission energies ω > 2μ the emission is determined by interband contributions and GP excitations become unimportant, as the dispersion relations in Fig. 2 show. At these energies the SE rate follows the same behavior as for the case of undoped graphene μ = 0 eV, as seen in Fig. 4(a). Moreover, we can see that the main contribution to the peak in the normalized SE rate ˜ γ comes from the GP contribution, which is denoted by the circular symbols in Fig. 4(a). The maximum value of D is 0.41 at μ = 0.4 eV, thus placing us within the weak coupling regime.

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Nitrate reduction using zero valent iron and effect of corrosion inhibitor on reduction

Nitrate reduction using zero valent iron and effect of corrosion inhibitor on reduction

nitrate. Therefore in these experiments an attempt has been made to retard the corrosion of ZVI using a concrete penetrating corrosion inhibiting admixture (CPCIA) EPCO- KP 200, designed for protecting the reinforcement bars in concrete against chloride attack. It is a bipolar inhibitor, which retards the corrosion process both at the cathodic and the anodic sites. The process is chemical and not physical. The electron density distribution causes the inhibitor to be attracted to both anodic and cathodic sites. EPCO KP-200 by virtue of its vapour pressure diffuses and gets deposited on the steel in a monomolecular layer. The molecules are water soluble and possess binding energy to metal surfaces higher than the binding energy of water dipoles and chlorides from the metal surface [8].Firstly, experiments were carried out to study the mechanism of oxidation of iron and its inhibition using cement admixture EPCO KP-200 and to determine the optimum dosage of the admixture by directly exposing steel to different concentration of EPCO-KP 200.Secondly, different experiments were conducted by varying dosage of ZVI to check nitrate reduction at regular time intervals. In addition to this, studies were undertaken to check the effect of EPCO-KP 200 on performance of ZVI in nitrate reduction.

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Identification of Linked NS2B-NS3 Protease Conformation of the Zika Virus with Allosteric Bioactive Compound Antagonists

Identification of Linked NS2B-NS3 Protease Conformation of the Zika Virus with Allosteric Bioactive Compound Antagonists

Niclosamide has the same binding energy of protein before and after refinement which is -9.3 kcal/mol, but there is more hydrophobic bonding interactions of surrounding proteins after refinement (His51 and Ser135) than before refinement (His51). It is a bit similar to quinacrine, which has the same interaction catalytic triad related residue. 4-nitrophenyl 4-guanidinobenzoat and quercetin are noncompetitive inhibitors that have the highest affinity value

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Influence of Ca Content on Binding Energy and Cooper Pairing in Y1 xCaxBa2Cu3O7 δ Compound

Influence of Ca Content on Binding Energy and Cooper Pairing in Y1 xCaxBa2Cu3O7 δ Compound

tance between layers which can be calculated using the Equation (3) and the result are shown in the Table 1. The calculation of the binding energy was done by using Equation (9), for solving the integration we apply the math lab program to determine each value of binding energy which corresponding to concentration of Ca content in the compound. The results are shown in the Table 2. Which shows that Ca content increases the dis- tance between the two layers decrease as a result the binding energy will be decreased as seen in the Figure 4 and Figure 5 in the Y Ca Ba Cu O 1 x 2 3 7 − δ compound. The following experimental values were inserted in Equa-

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Study on adsorption and desorption of ammonia on graphene

Study on adsorption and desorption of ammonia on graphene

Theoretically, the density functional theory (DFT) calcu- lations were performed with CASTEP [12]; the general- ized gradient approximation (GGA) was used to deal with the exchange and correlation term. It is well known that the local density approximation (LDA) is normally in- accurate in describing the van der Waals-like interaction, and the advantage of GGA over LDA in this work is that the GGA will not lead to a strong bonding of the mole- cules as LDA does [13]. A plane wave basis set with a cutoff energy of 800 eV and pseudopotentials of the Troul- lier–Martins type and non-spin-polarized calculations were used in this study. The total system consisted of a 3 × 3 graphene supercell (18 C atoms) with a single mol- ecule adsorbed and a distance of 16 Å between adjacent graphene layers. The Brillouin zone integration was per- formed within the Monkhorst–Pack scheme using 5 × 5 × 1 k points [14]. For the calculation of the density of states (DOS), a 20 × 20 × 1 Monkhorst–Pack grid and a Gaussian smearing of 0.05 eV were used [15].

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Graphene Synthesis Methods for Graphene Based Supercapacitors of the Solar Energy Systems

Graphene Synthesis Methods for Graphene Based Supercapacitors of the Solar Energy Systems

[20] Wendt, H., & Kreysa, G. (1999). Electrochemical engineering: science and technology in chemical and other industries. Springer Science & Business Media. [21] Low, C. T. J., Walsh, F. C., Chakrabarti, M. H., Hashim, M. A., & Hussain, M. A. (2013). Electrochemical approaches to the production of graphene flakes and their potential applications. Carbon, 54, 1-21. [22] Su, C. Y., Lu, A. Y., Xu, Y., Chen, F. R., Khlobystov, A. N., & Li, L. J. (2011). High- quality thin graphene films from fast electrochemical exfoliation. ACS nano, 5(3), 2332-2339.

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First Principles Investigation of Technologically and Environmentally Important Nano-Structured Materials and Devices

First Principles Investigation of Technologically and Environmentally Important Nano-Structured Materials and Devices

The honeycomb lattice of graphene has two carbon atoms per unit cell. Each atom has one s and three p orbitals. The s orbital and two in-plane p orbitals are tied up in grapehen’s strong covalent bonding and do not contribute to it’s conductivity. The remaining p orbital, oriented perpendicular to the molecular plane, is odd under inversion in the plane and hybridizes to form π (valence) and π* (conduction) bands 11 . In the Bloch band description of graphene’s electronic structure, orbital energies depend on the momentum of charge carriers in the crystal Brillouin zone. First, the band structure of the single layer graphene (SLG) is reproduced in Figure 4.1 12 . SLG is then characterized by the linear dispersion of the π bands near Fermi level (E F ) represent massless fermions. The Fermi energy separates occupied and

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