Density Functional Theoretical Study Research Articles

DFT studies on vibrational spectra, HOMO–LUMO, NBO and thermodynamic function analysis of cyanuric fluoride

In this work, the theoretical vibrational spectral characteristics of cyanuric fluoride (C3N3F3) have been investigated and compared with existing experimental results. The density functional theoretical (DFT) computations were performed at the B3LYP level with the basis sets 6-31G(d,p) and 6-311++G(d,p) levels to derive the optimized geometry, vibrational wavenumbers with IR intensities of cyanuric fluoride. In addition, the molecular orbital calculations such as Natural Bond Orbitals (NBOs), HOMO–LUMO energy gap and Mapped molecular Electrostatic Potential (MEP) surfaces were also performed with the same level of DFT. Electronic stability of the compound arising from hyper conjugative interactions and charge delocalization were also investigated based on the natural bond orbital (NBO) analysis. Effective stabilization energy E(2) connected with the interactions of the π and the lone pair of electrons was determined by the NBO analysis. Mulliken population analysis on atomic charges is also calculated. The thermodynamic properties of the cyanuric fluoride at different temperatures have also been calculated for the range of temperature 50–1000K.

Formation mechanism and possible stereocontrol of bisphenol a derivatives: a computational study.

Density functional theoretical study elucidates two different pathways for metabolic activation of 2,2'-bis(4-hydroxyphenyl) propane (Bisphenol A; BPA) and consequential formation of 4-methyl-2,4-bis(p-hydroxyphenyl)pent-2-ene (M-1) and 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (M-2, the potential environmental estrogen). Selectivity toward M-1(nontoxic)/M-2(toxic) formation can be controlled by varying the polarity of the reaction medium. We also found the reversal of thermodynamic stability for M-1/M-2 in response to the static polarization of the medium. Moreover, stereocontrol of biologically active M-2 with static polarization as the switch (∼0.005 au) might affect the receptor binding. This analysis may be useful in dictating the prevention of the harmful action of BPA and its metabolites.

Interaction of anthranilic acid with silver nanoparticles: A Raman, surface-enhanced Raman scattering and density functional theoretical study

Raman and surface-enhanced Raman scattering (SERS) studies of anthranilic acid have been investigated in solid, aqueous solution and on silver colloid. Anthranilic acid plays a key role in the brain in the production of quinolinic acid which is a powerful excitant and convulsant substance. Due to its medicinal importance, the surface adsorption properties of anthranilic acid have been studied. The experimental Raman and SERS data is supported with DFT calculations using B3LYP functional with aug-cc-pvdz and LANL2DZ basis sets. The comparison of experimental and theoretical results infers that anthranilate is chemisorbed to the silver surface directly through the carboxylate group with a perpendicular orientation. The time-dependent SERS spectrum of anthranilate showed no observable change indicating no structural transformation with time. The SERS spectrum recorded at different excitation wavelengths helped in understanding the origin of the SERS mechanism.

Indigo adsorption on a silicate surface: a theoretical density functional study.

The applicability of naturally available low-cost and eco-friendly adsorbent materials for the removal of hazardous dyes from aqueous waste is of increasing environmental interest. Among the adsorption treatments available, clays seem to be economically attractive due to their abundance and adsorption capabilities. Indeed, many ancient coloring materials utilized clays mixed with natural dyes (e.g., indigo in Maya Blue). In this work, we performed a quantum-mechanical theoretical study of the adsorption of the indigo molecule onto the (001) surface of a phyllosilicate. Different methods and approaches were applied and compared. We found that the presence of a tetrahedral charge and a sodium counterion significantly increased the adsorption energy of the indigo molecule. The vibrational spectrum of the dye-surface system was also studied, and some interesting shifts in the frequencies of the main vibrational modes of indigo due to its interaction with the surface of the clay mineral were identified.

Reaction of CH3CHO with Y+: A density functional theoretical study

The reaction mechanism of the Y+ cation with CH3CHO has been investigated with a DFT approach. All the stationary points are determined at the UB3LYP/ECP/6-311++G** level of the theory. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of a CH3CHO-metal complex followed by C-C, aldehyde C-H, methyl C-H and C-O activation. These reactions can lead to four different products (Y+CH4 + CO, Y+CO + CH4, Y+COCH2 + H2 and Y+O + C2H4). The minimum energy reaction path is found to involve the spin inversion in the different reaction steps, this potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

Ligand effect on the CuI-catalyzed C–S coupling reaction: A density functional theoretical study

The mechanism of C–S coupling reaction from benzenethiol and 1-bromo-4-methoxybenzene to (4-methoxyphenyl)(phenyl)sulfane catalyzed by CuI/BtH has been investigated by using density functional theory (DFT). The co-catalytic effect of the ligand benzotriazole (BtH) was analyzed in details based on a previous experiment reported by Verma that a general and efficient C–S coupling reaction by means of inexpensive catalysts CuI/BtH (Verma et al., 2007). In order to provide comparative data, the structures have been optimized at the B3LYP/6-31+G(d) level in the gas phase and in solution, N,N-dimethyl formamide being the solvent. Our calculated results interpreted that the ligand of BtH can significantly promote the C–S coupling reaction, i.e., reduce the energy barriers in the steps of the C–S coupling and the CuBr dissociation. Furthermore, the mechanism we proposed can be extended to other C–S coupling reaction catalyzed by Cu(I) complexes.

Stability of Pt-Ru Alloy for Anode Catalyst in PEFC Fuel Cell: A Density Functional Theory Study

Pt-based material are commonly used as electrocatalysts for low temperature fuel cells. The Pt metal surface is easily poisoned by trace amount of CO, especially in fuel cells [1]. CO is also present in H2produced by stream reforming of methanol, ethanol and hydrocarbon fuels, it is also a problem in hydrogen fuel cells [2]. Among the most studied catalysts, the supported platinum based particles have been exhibited a notable efficiency for limiting CO poisoning. Most practical anode fuel cell catalysts consist of platinum nanoparticles alloyed by a second components are Ru, Mo and Sn, which have been studied in many recent surface electrochemistry studies. Among the binary systems the Pt-Ru combination has proved to be most successful at enhancing electro-catalytic activity [3].The carbon CO itself is usually assumed to follow a so-called bifunctional mechanism, originally suggested by Watanbe and Motoo. [4]. In this mechanism, Ru sites act as adsorption centers for the oxygen-containing surface species reacting with the CO to produce CO2. Attempts have been made to develop catalysts that either enhance the oxidation of adsorbed CO or simply tolerate CO better, or both, by alloying Pt with other metals. The improvement of the catalytic performance requires an understanding of the reaction mechanism at the atomistic level. There are many studies have been performed for CO adsorption and oxidation on the Pt and Pt-based alloys in order to design highly CO tolerant bimetallic catalysts but there is few studies regarding atomistic scale and dynamical phenomena of the CO adsorption and oxidation mechanism. A combined molecular dynamics (MD)/density-functional theoretical (DFT) study of the electro-oxidation of CO at the Pt-Ru alloy interface is very important to provide insights into the reaction mechanism.All calculations were performed using DFT under the generalized gradient approximation with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional. A double numerical basis set augmented with polarization functions were used in the optimization. The computational method used in the present study is implemented in the DMol3 [5]. First-principles molecular dynamics is performed to know the dynamical properties of CO/Pt-Ru interface during the CO oxidation process.To simulate the mentioned first we determined the most stable initial state on each surface. The Pt(111)-(CO+O) and Pt-Ru (111)-(CO+O) system where O adsorbs on the hollow site and CO on the atop site with the carbon head closer to the surface. From previous findings it is assumed that Pt-metal alloy shows more reactivity than pure Pt for CO oxidation but very few studies regarding atomistic level and dynamical characteristics of this oxidation process. From our combined MD and DFT study we expect we will be able to examine electronic and geometric change of Pt-metal and its role of CO oxidation process. In our MD calculation we would be able to know temperature effect on Pt-Ru alloy surface as well as CO oxidation mechanism on this bimetallic surface. We also want to investigate how the Pt-Ru alloy structure change by CO and H2O adsorption using MD.Reference:H.A. Gasteiger, N. Markovic, P.N. Ross Jr., E.J. Cairns, J. Phys.Chem B. 98, 617 (1994)H. Gasteiger, N. Markovic, P. Ross, J. Phys. Chem. 99, 8945 (1995)M.Watanabe, M. Uchida, S. Motoo, J. Electroanal. Chem. 229, 395 (1987)M.Watanabe, S. Motoo, J. Electroanal. Chem. 60, 275 (1975)B. Delley, J. Chem. Phys. 92,508 (1990)

Density-Functional Theoretical Study on the Role of Lewis and Brønsted Acid Sites on CeO2(110) Surfaces for Nitrile Hydration

Hydration of cyanopyridine on CeO2(110) surfaces was studied using periodic DFT+U calculations. One of two adsorption modes of 2-cyanopyridine occurs with two-point interaction which causes substrate specificity. A catalytic cycle for the hydration of 2-cyanopyridine was proposed. Cooperativity of Lewis and Bronsted acid sites was found to stabilize the intermediates for the hydration.

Design and screening of suitable ligand/diluents systems for removal of Sr2+ ion from nuclear waste: Density functional theoretical modelling

Density functional theoretical (DFT) calculation has been used for the design and screening of ligand/solvent systems for the selective and efficient extraction of Sr2+ ion from aqueous solution using free energy analysis. Present DFT study has shown that the metal ion selectivity cannot be predicted using intrinsic gas phase interaction energy alone. Even implicit solvation employing conductor like screening model (COSMO) approach unable to predict the correct trend of experimental selectivity. The COSMO solvation model when used explicitly by considering first solvation sphere around the metal ion it captures the correct trend of experimental selectivity. Organic solvent of high dielectric constant was found to be suitable for the extraction of the metal ion. Further, COSMO for real solvent (COSMO-RS) was successfully used to predict the solubility and partition coefficients of the ligands for screening. Presence of nitrate anion in the complexation reaction was shown to increase the gas as well as solvent phase complexion energy. The calculated theoretical extraction energy was found to be well correlated to the experimentally observed distribution constant of Sr2+ ion in the biphasic systems. The preferential selectivity of Sr2+ ion over other competing ions towards macrocyclic ligands was demonstrated by calculating free energy of extraction in the biphasic systems. Natural bond order (NBO) analysis was also performed to investigate the nature of bonding in Sr2+ ion-crown ether interaction.

Combined Mössbauer spectroscopic, multi-edge X-ray absorption spectroscopic, and density functional theoretical study of the radical SAM enzyme spore photoproduct lyase.

Spore photoproduct lyase (SPL), a member of the radical S-adenosyl-L-methionine (SAM) superfamily, catalyzes the direct reversal of the spore photoproduct, a thymine dimer specific to bacterial spores, to two thymines. SPL requires SAM and a redox-active [4Fe-4S] cluster for catalysis. Mössbauer analysis of anaerobically purified SPL indicates the presence of a mixture of cluster states with the majority (40%) as [2Fe-2S](2+) clusters and a smaller amount (15%) as [4Fe-4S](2+) clusters. On reduction, the cluster content changes to primarily (60%) [4Fe-4S](+). The speciation information from Mössbauer data allowed us to deconvolute iron and sulfur K-edge X-ray absorption spectra to uncover electronic (X-ray absorption near-edge structure, XANES) and geometric (extended X-ray absorption fine structure, EXAFS) structural features of the Fe-S clusters, and their interactions with SAM. The iron K-edge EXAFS data provide evidence for elongation of a [2Fe-2S] rhomb of the [4Fe-4S] cluster on binding SAM on the basis of an Fe···Fe scatterer at 3.0Å. The XANES spectra of reduced SPL in the absence and presence of SAM overlay one another, indicating that SAM is not undergoing reductive cleavage. The X-ray absorption spectroscopy data for SPL samples and data for model complexes from the literature allowed the deconvolution of contributions from [2Fe-2S] and [4Fe-4S] clusters to the sulfur K-edge XANES spectra. The analysis of pre-edge features revealed electronic changes in the Fe-S clusters as a function of the presence of SAM. The spectroscopic findings were further corroborated by density functional theory calculations that provided insights into structural and electronic perturbations that can be correlated by considering the role of SAM as a catalyst or substrate.

The healing of N-vacancy in boron nitride nanotube by using NO and NO2 molecules: a density functional theoretical study

Download options Please wait... Article information DOI https://doi.org/10.1039/C4RA02833C Article type Paper Submitted 31 Mar 2014 Accepted 29 Apr 2014 First published 01 May 2014 Download Citation RSC Adv., 2014,4, 22688-22696 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions The healing of N-vacancy in boron nitride nanotube by using NO and NO2 molecules: a density functional theoretical study B. Xiao, X. Yu and Y. Ding, RSC Adv., 2014, 4, 22688 DOI: 10.1039/C4RA02833C To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Bo Xiao Xue-fang Yu Yi-hong Ding

The hapticity of octafluorocyclooctatetraene in its first-row mononuclear transition metal carbonyl complexes: effect of perfluorination

The iron tricarbonyl complex of octafluorocyclooctatetraene was synthesized by Hughes and co-workers and shown by X-ray crystallography to have a trihapto–monohapto structure (η3,1-C8F8)Fe(CO)3 in contrast to the tetrahapto structure (η4-C8H8)Fe(CO)3 formed by the non-fluorinated cyclooctatetraene. This difference has stimulated a comprehensive density functional theoretical study of the octafluorocyclooctatetraene metal carbonyl complexes (C8F8)M(CO)n (n = 4, 3, 2, 1 for M = Ti, V, Cr, Mn, and Fe; n = 3, 2, 1 for M = Co, Ni) for comparison with their hydrogen analogues (C8H8)M(CO)n. In most such systems, the substitution of fluorine for hydrogen leads to relatively small changes in the preferred structures. However, for the iron carbonyl derivatives (C8X8)Fe(CO)3 (X = H, F), the difference observed experimentally has been confirmed by theory with (η3,1-C8F8)Fe(CO)3 and (η4-C8H8)Fe(CO)3 being the lowest energy structures by 4 and 14 kcal/mol, respectively. The ligand exchange reactions C8H8 + (C8F8)M(CO)n → C8F8 + (C8H8)M(CO)n are predicted to be exothermic for almost all of the systems considered, with the (η3,1-C8X8)Fe(CO)3 system being the main exception. This suggests that the C8F8 ligand generally bonds more weakly to transition metals than the C8H8 ligand in accord with the electron-withdrawing effect of the ligand fluorine atoms.

Density functional theoretical study on the preferential selectivity of macrocyclic dicyclohexano-18-crown-6 for Sr+2 ion over Th+4 ion during extraction from an aqueous phase to organic phases with different dielectric constants

The preferential selectivity of dicyclohexano-18-crown-6 (DCH18C6) for bivalent Sr(+2) ion over tetravalent Th(+4) ion was investigated using generalized gradient approximated (GGA) BP86 and the hybrid B3LYP density functional, employing split valence plus polarization (SV(P)) and triple-zeta valence plus polarization (TZVP) basis sets in conjunction with the COSMO (conductor-like screening model) solvation approach. The calculated theoretical selectivity of DCH18C6 for Sr(+2) ion over Th(+4) ion was found to be in accord with the selectivity for Sr(+2) ion over Th(+4) ion observed when performing liquid-liquid extraction experiments in different organic solvents. While 1:1(M:L) stoichiometric complexation reactions can be used to predict the preferential selectivity of Sr(2+) ion over Th(4+) ion, the results obtained are not consistent with the experimental results observed upon increasing the dielectric constant of the solvent. The calculated theoretical gas-phase data for the free energy of complexation, ∆G, fail to explain the selectivity for Sr(+2) ion over Th(+4) ion. However, when 1:2 (M:L) stoichiometric complexation reactions (reported in previous X-ray crystallography studies) are considered, correct and consistent results for the selectivity for Sr(+2) ion over a wide range of dielectric constants are predicted. The distribution constant for Sr(2+) and Th(4+) ions was found to gradually increase with increasing dielectric constant of the organic solvent, and was found to be highest in nitrobenzene. The selectivity data calculated from ∆∆G ext are in excellent agreement with the results obtained from solvent extraction experiments.

Time-dependent density functional theoretical studies on the photo-induced dynamics of an HCl molecule encapsulated in C60 under femtosecond laser pulses

By using first-principles simulations based on time-dependent density functional theory, the chemical reaction of an HCl molecule encapsulated in C60 induced by femtosecond laser pulses is observed. The H atom starts to leave the Cl atom and is reflected by the C60 wall. The coherent nuclear dynamic behaviors of bond breakage and recombination of the HCl molecule occurring in both polarized parallel and perpendicular to the H—Cl bond axis are investigated. The radial oscillation is also found in the two polarization directions of the laser pulse. The relaxation time of the H—Cl bond lengths in transverse polarization is slow in comparison with that in longitudinal polarization. Those results are important for studying the dynamics of the chemical bond at an atomic level.

Diels–Alder reaction of β-chloro-α,β-unsaturated aldehydes with cyclopentadiene: an experimental and theoretical study

The Diels–Alder cycloaddition reactions of four β-chloro-α,β-unsaturated aldehydes 1–4 with cyclopentadiene were carried out. Only two of these aldehydes (3 and 4) were reactive and afforded highly functionalized norbornene isomers 5–10 in good yields. The Z-ethyl-2-chloro-3-formylacrylate 3 gave two diastereomers endo(COOEt)–exo(CHO) 5 and exo(COOEt)–endo(CHO) 6, whereas a mixture of Z and E of ethyl 3-chloro-2-formyl-4,4,4-trifluorobut-2-enoate 4 afforded the four diastereomers 7–10. These new cycloadducts (CAs) were characterized by NMR, IR, and mass spectrometry. Structural assignments for different isomers were made on the basis of NMR chemical shifts and coupling constants using 1D, 2D, and heteroNOE NMR techniques. A density functional theoretical study on reactants, transition state structures, and CAs was also undertaken in order to support the experimental data.

Synthesis, spectral, thermal, optical, electrical, mechanical and structural characterisations and quantum chemical study of 4-nitrophenol: Urea molecular adduct crystals

Organic non-linear single crystals of 4-Nitrophenol: Urea Adduct (NPUA) have been grown by slow evaporation-solution growth technique. The elemental analysis of the compound satisfies the stoichiometric expectations. Vibrational frequencies of the grown crystals have been identified by using FT-IR analysis. The presence of different protons and carbon atoms of the grown adduct was ascertained by 1H and 13C NMR analyses. The UV–Visible spectroscopy study revealed that the grown crystal has excellent transmittance and has wide band gap in the visible province. The fluorescence emission spectrum has also been recorded. Photoconductivity studies confirm positive photoconductivity nature of the crystals. The crystal belongs to the triclinic system with space group P1. The complete structural analysis of the grown crystal has been done using single crystal X-ray diffraction technique. Thermogravimetry (TG), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC) were carried out to characterise the thermal behaviour and stability of NPUA. Dielectric studies have been carried out at room temperature. Mechanical behaviour of NPUA was studied by Vickers’s microhardness test. The nonlinear optical (NLO) activity test using a Q-switched and pulsed Nd: YAG laser confirms the generation of second harmonics. The Density Functional Theoretical (DFT) study affords further insight on the properties of the compound. Quantum Chemical Calculations (QCC) have been performed through DFT method at B3LYP/6-31G(d) level of theory. The optimised geometric parameters such as bond lengths, bond angles, dipole moment, optimisation energy and vibrational frequencies were reported and compared with the experimental data.

CO Oxidation on Supported Single Pt Atoms: Experimental and ab Initio Density Functional Studies of CO Interaction with Pt Atom on θ-Al2O3(010) Surface

Although there are only a few known examples of supported single-atom catalysts, they are unique because they bridge the gap between homogeneous and heterogeneous catalysis. Here, we report the CO oxidation activity of monodisperse single Pt atoms supported on an inert substrate, θ-alumina (Al2O3), in the presence of stoichiometric oxygen. Since CO oxidation on single Pt atoms cannot occur via a conventional Langmuir-Hinshelwood scheme (L-H scheme) which requires at least one Pt-Pt bond, we carried out a first-principles density functional theoretical study of a proposed pathway which is a variation on the conventional L-H scheme and inspired by the organometallic chemistry of platinum. We find that a single supported Pt atom prefers to bond to O2 over CO. CO then bonds with the oxygenated Pt atom and forms a carbonate which dissociates to liberate CO2, leaving an oxygen atom on Pt. Subsequent reaction with another CO molecule regenerates the single-atom catalyst. The energetics of the proposed mechanism suggests that the single Pt atoms will get covered with CO3 unless the temperature is raised to eliminate CO2. We find evidence for CO3 coverage at room temperature supporting the proposed mechanism in an in situ diffuse reflectance infrared study of CO adsorption on the catalyst's supported single atoms. Thus, our results clearly show that supported Pt single atoms are catalytically active and that this catalytic activity can occur without involving the substrate. Characterization by electron microscopy and X-ray absorption studies of the monodisperse Pt/θ-Al2O3 are also presented.

Photoelectron spectroscopic and density functional theoretical studies of the 2′-deoxycytidine homodimer radical anion

The intact (parent) 2'-deoxycytidine homodimer anion, (dC)2 (●-), was generated in the gas phase (in vacuo) using an infrared desorption∕photoemission source and its photoelectron spectrum was recorded using a pulsed, magnetic bottle photoelectron spectrometer. The photoelectron spectrum (PES) revealed a broad peak with the maximum at an electron binding energy between 1.6 and 1.9 eV and with a threshold at ∼1.2 eV. The relative energies and vertical detachment energies of possible anion radicals were calculated at the B3LYP/6-31++G(∗∗) level of theory. The most stable anion radicals are the complexes involving combinations of the sugar[middle dot][middle dot][middle dot]base and base[middle dot][middle dot][middle dot]base interactions. The calculated adiabatic electron affinities and vertical detachment energies of the most stable (dC)2 (●-) anions agree with the experimental values. In contrast with previous experimental-computational studies on the anionic complexes involving nucleobases with various proton-donors, the electron-induced proton transferred structures of (dC)2 (●-) are not responsible for the shape of PES.

Solvent Effect and Hydrogen Bond Interaction on Tautomerism, Vibrational Frequencies, and Raman Spectra of Guanine: A Density Functional Theoretical Study

Stable structures and Raman spectra of guanine have been investigated by density functional theory (DFT). Focusing on solvent effect and hydrogen bonding interaction, we have calculated the two keto-amino tautomers G17K and G19K as well as their guanine-water complexes and tetramers. The results show G17K is more stable than G19K in the gas phase, whereas in polar solvents G19K dominates. The vibrational fundamentals of G17K have been reassigned based on normal-mode analysis, since the previous assignment was limited to the G19K only. In the Raman spectra, the modes of the ring breathing vibration and those in the fingerprint region (from 1000 to 1600 cm(-1)) affected by the solvent effect and the hydrogen bonding interaction dramatically. The band at 1163 cm(-1) of G17K in gas has a large blue shift when water molecule forms hydrogen bonds with N7-H16 and C6═O13 sites. The blue shift can be explained by the influence of hydrogen bonding interaction along with shortening the N1-C6 bond distance. In addition, the dominant existing tautomer in polycrystalline and powder guanine is proposed to be G17K, whose calculated vibrational frequencies agree with the experimental Raman spectra reported before.

Density Functional Theoretical Study of Graphene on Transition-Metal Surfaces: The Role of Metal d-Band in the Potential-Energy Surface

The nature of graphene/substrate interfaces needs to be understood to improve the crystalline quality of graphene films grown with chemical vapor deposition (CVD). We have theoretically investigated the potential-energy surface (PES) of graphene on catalyst transition-metal surfaces. The profile of PES highly depends on the type of underlying metals; the orders of the peak-to-valley (PV) values of PES are Cu < Ni < Co (3d), Pd < Rh < Ru (4d), and Pt < Ir < Os (5d). High PV values were found to be provided by metals with d-band close to the Dirac point of graphene. Our results indicate that the d-band of catalyst metals greatly influences the PES profile of graphene on the metals, which should be helpful for further understanding of the graphene/metal interfaces and its behavior in CVD growth process.