Adsorption Of Pyrazine Research Articles

Effect of Heteroaromaticity on Adsorption of Pyrazine on the Ge(100)-2×1 Surface

The reaction of pyrazine with the Ge(100)-2×1 surface has been investigated by X-ray photoelectron spectroscopy (XPS) and density functional theory calculations. Results show that pyrazine reacts w...

Combined in- and ex situ studies of pyrazine adsorption into the aliphatic MOF Al-CAU-13: structures, dynamics and correlations.

The intercalation of different pyrazines (pyrazine, methylpyrazine, 2,5-dimethylpyrazine, 2,3-dimethylpyrazine, trimethylpyrazine and tetramethylpyrazine) into the trans-1,4-cyclohexanedicarboxylate (CDC2-) based Al-MOF [Al(OH)(CDC)], denoted as CAU-13, was investigated. The adsorption of the guest molecules into the flexible MOF was carried out from an aqueous solution or via vapour phase adsorption, starting with the hydrated narrow-pore form of the framework [Al(OH)(O2C-C6H10-CO2)]·H2O (CAU-13-np). The obtained host-guest systems were characterised by thermogravimetry and vibrational spectroscopy and their crystal structures were elucidated using powder X-ray diffraction (PXRD) data. The crystal structures indicate that guest molecules forming hydrogen-bonds with the host framework (pyrazine, methylpyrazine and 2,5-dimethylpyrazine) induce a slight opening of the channels, resulting in a semi-open framework conformation (CAU-13-so). For the bulkier guests 2,3-dimethylpyrazine, trimethylpyrazine and tetramethylpyrazine, only van der Waals interactions can be observed between the host and the guest molecules and a large pore conformation is observed (CAU-13-lp). We carried out in situ PXRD studies using synchrotron radiation during the adsorption of the respective guest molecules from aqueous solutions with various concentrations and at different temperatures. In general, stronger host-guest interactions required milder adsorption conditions while harsher conditions nevertheless accelerated the conversion. The kinetic parameters for the intercalation of pyrazine indicate that the rate limiting step differs, depending on the intercalation temperature.

Spin Crossover in the {Fe(pz)[Pt(CN)4]} Metal-Organic Framework upon Pyrazine Adsorption.

The spin-crossover behavior of the {Fe(pz)[Pt(CN)4]} metal-organic framework (MOF) upon pyrazine adsorption is investigated through hybrid Monte Carlo/molecular dynamics (MC/MD) simulations. In contrast to previous theoretical studies, which reported a transition temperature of ∼140 K, the present MC/MD simulations predict that the high-spin state is the most stable state at all temperatures, in agreement with the experimental observations. The MC/MD simulations also indicate that the pyrazine molecules adsorbed in the MOF pores lie nearly parallel but staggered by 60° relative to the pyrazine ligands of the framework. The analysis of the magnetization curve as a function of the temperature demonstrates that the staggered configuration assumed by the guest pyrazine molecules within the framework is responsible for the stabilization of the high-spin state. Both the guest pyrazine molecules and the pyrazine ligands of the framework are effectively locked into the minimum-energy configuration and do not display any rotational mobility.

Adsorption of Pyrazine on a Si(001) Surface Partially Covered with an Indium Dimer Structure

Adsorption of Pyrazine on a Si(001) Surface Partially Covered with an Indium Dimer Structure

Adsorption of Pyrazine on a Si(001) Surface Partially Covered with an Indium Dimer Structure

Pyrazine forms a molecular one-dimensional (1D) line on a bare Si(001)-2×1 surface across the Si dimer row. Indium also forms a 1D line across the Si dimer row. In this study, the adsorption of pyrazine on a Si(001)-2×1 surface on which the indium parallel dimer structure is formed was investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). It was found by STM that pyrazine adsorbates were predominantly located at the lateral neighboring sites of the indium line structure during the initial stage of adsorption. This preferential adsorption of pyrazine can enhance the formation of long linear chains of pyrazine along the indium lines.

Stepwise deposition of metal organic frameworks on flexible synthetic polymer surfaces

Thin films of [Cu(3)(btc)(2)](n) (btc = 1,3,5-benzenetricarboxylate) metal organic framework were deposited in a stepwise manner on surfaces of flexible organic polymers. The thickness of films can be precisely controlled. The deposition of the first cycles was monitored by UV-vis spectroscopy. The porosity was proven by the adsorption of pyrazine, which was monitored by FT-IR and thermogravimetric analysis. The deposition of MOF thin films on flexible polymer surfaces might be a new path for the fabrication of functional materials for different applications, such as protection layers for working clothes and gas separation materials in the textile industry.

An investigation of the adsorption of pyrazine and pyridine on nickel electrodes by in situ surface-enhanced Raman spectroscopy

This paper describes a surface-enhanced Raman spectroscopic study on nickel electrodes. The enhancement factor of the roughened Ni substrate was found to be from two to three orders, depending on the surface pre-treatment. High-quality SERS spectra of pyrazine and pyridine were obtained at different potentials. The bands assigned to Ni–N pyrazine and Ni–N pyridine were observed around 260 cm −1 in the low-frequency region of two sets of SERS spectra, respectively. The adsorption behaviour of pyrazine and pyridine on Ni electrode was studied and compared based on the surface selection rule. The result suggests that both pyrazine and pyridine were strongly adsorbed onto the substrates. It also implies that pyridine was adsorbed perpendicularly onto the substrate, while pyrazine adsorbed onto the substrate in a slightly tilted vertical configuration. The observation of forbidden bands of the pyrazine molecule is due to the lowering of the symmetry from D 2h to C 2V when adsorption onto the surface takes place. The electrochemical reduction of pyrazine on the Ni electrode was observed at extremely negative potentials in the presence of Cl −.

A comparison of surface-enhanced infrared and surface-enhanced Raman spectra of pyrazine adsorbed on polycrystalline gold electrodes

The adsorption of pyrazine at a polycrystalline Au film electrode has been investigated using in situ surface-enhanced infrared absorption spectroscopy (SEIRAS), chronocoulometry, and ac impedance. Combining the SEIRA data and the thermodynamic data (the surface charge density of the electrode and the relative Gibbs surface excess of pyrazine), pyrazine was found to adsorb on the surface with a vertical end-on configuration via one N atom. The SEIRA spectra were compared with published surface-enhanced Raman (SER) spectra of pyrazine in order to clarify the reason for the breakdown of the Raman selection rule in the SER spectra. The activation of originally Raman-forbidden modes in the SER spectra is well explained by a photo-driven charge-transfer mechanism. The charge-transfer is deduced to be from filled metal states near the Fermi level to the first and second excited states of pyrazine. It is emphasized that the comparative SEIRA and SER studies are important for a better understanding of the electrochemical interface.

Electrochemical and Raman spectroscopic studies of pyrazine adsorption at the Au(210) electrode surface

Chronocoulometry and Raman spectroscopy have been applied to study pyrazine adsorption at the Au(210) electrode surface. The adsorption isotherms, Gibbs energies of adsorption, and the electrosorption valency for pyrazine adsorption at the Au(210) electrode surface have been determined. Surface-enhanced Raman Scattering (SERS) spectra of pyrazine adsorbed on an "unroughened" Au(210) electrode surface have been obtained for the first time. The thermodynamic data and the SERS spectra indicate that pyrazine adsorbs on the Au(210) electrode via the nitrogen lone pair (N-bonded configuration) over the whole range of electrode potentials investigated. Consequently, the pyrazine molecule assumes only the vertical orientation at this surface of gold. The adsorption of pyrazine at the Au(210) and Au(111) surfaces is compared and the influence of the surface crystallography on the adsorption of this molecule at gold electrodes is discussed. Keywords: adsorption at Au(210), pyrazine, SERS, chronocoulometry.

Adsorption of pyrazine on Au(111) and Ag(111) electrodes an ex situ XPS study

The adsorption of pyrazine on Au(111) and Ag(111) electrodes from aqueous solutions has been studied ex situ by X-ray photo-electron spectroscopy (XPS). The well known structure transition of pyrazine on Au(111) from flat to vertical is clearly reflected in a change in the N 1s binding energy, while no such change in orientation has been noted for pyrazine on Ag(111), for which a flat-lying molecule is assumed at all potentials. Furthermore, distinctly different electrochemical shifts for the N 1s level were observed for the two orientations in the case of pyrazine on Au(111). This suggests that the electrochemical shift of adsorbed molecules may be successfully employed for sensing the electrostatic potential variation inside the electrochemical double layer. The surface concentration of pyrazine on Au(111) as a function of potential has been determined from XPS intensities and is compared with coulometric data.

Fourier transform Raman and fourier transform ir spectroscopic investigation of pyrazine adsorbed by sepiolite and bentonite from anatolia

AbstractThe adsorption of pyrazine by two different Anatolian sepiolites and by natural and ion‐exchanged (Fe, Co, Cu and Sn) bentonites was investigated by vibrational spectroscopy. The spectroscopic results indicate that the pyrazine molecules adsorbed on sepiolite and bentonites are coordinated to either surface hydroxyls by H‐bonding interaction (in the case of sepiolite) or to exchangeable cations (in the case of bentonites) through both nitrogen lone pairs as bidentate ligands. X‐ray diffraction patterns of the clays were also recorded and the basal spacings of pyrazine‐treated natural and ion‐exchanged bentonites were found to be around 14.7 Å. The results suggest that pyrazine molecules intercalate the interlayers of bentonite with a monolayer arrangement.

Adsorption of pyrazine on Au(111) and Ag(111): on the role of the electronic factor

XPS and AES investigations of the emersed Au(111) and Ag(111) electrodes have revealed that pyrazine is more weakly adsorbed on Ag than on Au. Whereas on Au, pyrazine is firmly bound on the surface and the increase in the positive charge of the electrode brings about the increase in the organic surface excess by changing the molecule orientation from a flat to a vertical position being then involved in the subsequent anodic oxidation processes, its bond with silver is so weak that anions remove it easily from the surface. The different behavior of the two electrodes to the pyrazine adsorption has been explained in terms of electronic interactions.

Adsorption of pyrazine at the Au(111) | aqueous solution interface

Cyclic voltammetry, differential capacity and chronocoulometry have been employed to study pyrazine adsorption quantitatively at the Au(111) | aqueous solution interface. The adsorption isotherms, Gibbs energies of adsorption and the electrosorption valency for pyrazine adsorption at the Au(111) surface have been determined. The results indicate that pyrazine adsorption at gold has the character of weak chemisorption which involves either the interaction of π orbitals of the aromatic ring with free electrons at the metal surface or a mixing of the n orbital at the nitrogen atom with d electronic states in the metal. Consequently the pyrazine molecule may assume either the π-bonded flat or the N-bonded vertical surface coordinations. The flat orientation is stabilized at the negatively charged surface, the vertical orientation is stabilized at the positively charged surface. A reorientational phase transition in the monolayer of adsorbed pyrazine was observed at the potential of zero charge.

The adsorption of pyrazine, hydrogen sulfide and thiophene on copper: A quantum-chemical study

The bonding of pyrazine (C 4H 4N 2), hydrogen sulfide (H 2S) and thiophene (C 4H 4S) to copper surfaces has been examined employing semi-empirical MO-SCF calculations (INDO/S) and metal clusters of limited size (Cu n n = 14, 16, 17 and 18). The C 4H 4N 2Cu, H 2SCu and C 4H 4SCu adsorption bonds are mainly a product of the interaction of the 4s and 4p orbitals of the substrate with the LUMO and the sulfur or nitrogen lone pairs of the adsorbate. Based on these INDO/S results, the UPS spectra of pyrazine, H 2S and thiophene on copper surfaces are discussed and compared with experimental results. For each adsorbed molecule, charge transfers important to the change in work function are presented. The effects of chemisorption upon the CN, CC and CH bonds of pyrazine, the CS, CC and CH bonds of thiophene, and the SH bonds of H 2S are examined. The large reactivity of H 2S on copper surfaces is explained in terms of a thermochemical analysis.

Adsorption of pyrazine at the polycrystalline gold-solution interface

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdsorption of pyrazine at the polycrystalline gold-solution interfaceAnna Iannelli, Jocelyn Richer, and Jacek LipkowskiCite this: Langmuir 1989, 5, 2, 466–473Publication Date (Print):March 1, 1989Publication History Published online1 May 2002Published inissue 1 March 1989https://doi.org/10.1021/la00086a031RIGHTS & PERMISSIONSArticle Views123Altmetric-Citations22LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (901 KB) Get e-Alerts Get e-Alerts

ChemInform Abstract: COMPARISON OF DROP‐TIME AND ELECTROCAPILLARY METHODS FOR STUDY OF ADSORPTION OF A NEUTRAL MOLECULE AT THE MERCURY ELECTRODE

Abstract The question of the reliability of the electrocapillary technique for measurement of relative changes of surface tension is investigated for the case of aqueous. 0·03N NaClO 4 and for solutions containing the rigid symmetrical molecule pyrazine. Surface tension and adsorption measurements have been made by drop-time and electrocapillary techniques. Only very small differences of surface tension changes, due to adsorption of pyrazine at various electrode charges, can be detected between the two methods. The surface excess/chemical potential relations derived from the results of the two methods are almost identical. It is concluded that systematic errors in the study of electrochemical adsorption by the electrocapillary method do not normally arise.

Compensation effects in the thermodynamics of electrochemical adsorption of organic substances

Isosteric entropies and enthalpies of adsorption of pyrazine, pyridine andn-amyl alcohol at the mercury electrode have been measured at various constant charges. The “TΔS” component of the free energy of adsorption is relatively large for pyrazine and pyridine but is compensated by a comparable “ΔH” component that makes the free energy of adsorption relatively less sensitive to changes of surface charge and coverage. The variations of ΔS are discussed in terms of field-dependent orientation and displacement of water molecules in the Hg-water interphase. The entropies of adsorption for pyrazine and pyridine are found to vary linearly with the respective enthalpies of adsorption over a wide range of values of surface charge and coverage. The compensation temperatures, Tc, in the relation ΔH= α + TcΔS are in the range 292–317 °K, indicating a large degree of compensation at ambient temperatures (298°K). The compensation effects observed provide further evidence for the very important role of water orientation and displacement in electrochemical adsorption of organic substances at electrodes. Similar compensation effects are found for many physical and biochemical processes in the water solvent and reflect the important role of H′-bonding and structural effects in that medium.

Comparison of drop-time and electrocapillary methods for study of adsorption of a neutral molecule at the mercury electrode

The question of the reliability of the electrocapillary technique for measurement of relative changes of surface tension is investigated for the case of aqueous. 0·03N NaClO 4 and for solutions containing the rigid symmetrical molecule pyrazine. Surface tension and adsorption measurements have been made by drop-time and electrocapillary techniques. Only very small differences of surface tension changes, due to adsorption of pyrazine at various electrode charges, can be detected between the two methods. The surface excess/chemical potential relations derived from the results of the two methods are almost identical. It is concluded that systematic errors in the study of electrochemical adsorption by the electrocapillary method do not normally arise.