Adsorption Of Coumarin Research Articles

Physico-chemical investigations of human olfactory receptors OR10G4 and OR2B11 activated by vanillin, ethyl vanillin, coumarin and quinoline molecules using statistical physics method

This research work is a contribution to understand the olfaction mechanism at a molecular level of vanillin, ethyl vanillin, coumarin and quinoline molecules using a modeling of a putative adsorption process by analytical model established by statistical physics formalism.A statistical physics modeling using the monolayer model with identical and independent binding sites of the responses of the two human olfactory receptors OR10G4 and OR2B11 showed that vanillin and quinoline were adsorbed with a mixed non-parallel and parallel orientation on OR10G4 and on OR2B11, respectively. However, ethyl vanillin and coumarin were anchored with a total non-parallel orientation. The adsorption energy values collected from data analysis, which were ranged from 12.51 to 20.91 kJ/mol, confirmed that the adsorption of vanillin and ethyl vanillin on OR10G4 and the adsorption of coumarin and quinoline on OR2B11were exothermic and were based on physical interactions.Furthermore, the dose-olfactory response curves of vanillin, ethyl vanillin, coumarin and quinoline provided access to OR10G4 and OR2B11 steric characterization via the calculation of the studied olfactory receptors site size distributions (RSDs). Indeed, vanillin, ethyl vanillin, coumarin and quinoline RSDs are spread from 0.3 to 12 nm, from 0.5 to 12 nm, from 0.40 to 12 nm and from 0.14 to 12 nm, respectively, with a maximum at 1.55 nm, 2.11 nm, 2.50 and 1.13 nm, respectively.Lastly, the physico-chemical model parameters can be used for the energetic characterization to confirm the physical nature of the vanillin/ethyl vanillin-OR10G4 and the coumarin/quinoline-OR2B11 interactions and to determine an olfactory band of order of 12 kJ/mol [11–23 kJ/mol], 10 kJ/mol [14–24 kJ/mol], 7 kJ/mol [9–16 kJ/mol], 15 kJ/mol [13–28 kJ/mol] for vanillin, ethyl vanillin, coumarin and quinoline, respectively, through the determination of the adsorption energy distributions (AEDs).

Silica Gel Supported Hydrophobic Ionic Liquid for Selective Extraction and Determination of Coumarin

In this study, a modified silica gel surface with a hydrophobic ionic liquid (SG-1,10-PhenanNTf2) was used as an adsorbent for a selective extraction of coumarin prior to its determination by use of high performance liquid chromatography. Results demonstrated that SG-1,10-PhenanNTf2 phase had a good adsorption capacity up to 85.29 mg?g?1, high selectivity, good site accessibility and fast binding kinetics toward coumarin. The adsorption capacity for coumarin was improved by 62.33% with the SG-1,10-PhenanNTf2 phase as compared to activated silica gel. Adsorption isotherm data displayed that the adsorption process was mainly monolayer on a homogeneous adsorbent surface, confirming the validity of Langmuir adsorption isotherm model. The adsorption of coumarin on the SG-1,10-PhenanNTf2 phase was accomplished after only 60 min contact time. Results of kinetic models showed that the adsorption of coumarin on the SG-1,10-PhenanNTf2 phase obeyed a pseudo second-order kinetic model. Finally, the efficiency of this methodology was confirmed by applying it to real water samples.

Potential‐controlled coordination of coumarin to an Au(210) electrode surface

AbstractAdsorption of coumarin on an Au(210) single‐crystal electrode was investigated using chronocoulometry and phase‐sensitive a.c. voltammetry. The adsorption parameters, such as the relative Gibbs surface excess, the Gibbs energies of adsorption and the electrosorption valencies, were calculated. The results suggest that coumarin molecules assume a flat, π‐bonded orientation on the Au(210) surface. The zero coverage Gibbs energy of adsorption at the potential of maximum adsorption is −42 kJ mol−1, which is a value typical of chemisorption. The adsorption of coumarin on the Au(210) surface was compared with adsorption at the (111) and (100) planes of gold. Copyright © 2003 John Wiley & Sons, Ltd.

Nickel Deposition in the Presence of Coumarin: An Electrochemical Impedance Spectroscopy Study

An electrochemical impedance spectroscopy study of nickel deposition onto a rotating disk from a coumarin‐containing Watts bath is presented. A model that assumes (i) adsorption of coumarin follows a Langmuir isotherm, (ii) that coumarin is consumed by incorporation into the deposit, and (iii) that metal‐ion intermediates compete with the leveling agent for surface sites is presented and shown to be in reasonable accord with experiment. However, discrepancies in the experimental and simulated dependence of the impedance data on coumarin concentration are noted. How impedance spectra may provide a more reliable means of determining kinetic parameters for the description of leveling agents than steady‐state polarization experiments is also discussed.

Two‐dimensional phase transitions in electrochemically formed adlayers on gold

AbstractTwo‐dimensional phase transitions occurring during electrodeposition of the first Cu monolayer onto Au(111) at underpotentials or during adsorption of coumarin from solution at Au(111) and the reconstructed Au(100)‐ (hex) electrodes have been studied by cyclic voltammetry and potential step experiments. Rising current transients were observed for both systems, indicating the presence of nucleation‐and‐growth phenomena during monolayer formation. However, phase transitions in the adlayers were observed only for the densely packed gold surfaces, and not for the more open surfaces of Au(100)‐(1×1) or Au(110). A comparison between experiment and classical model transients revealed that surface imperfections may have to be taken into account when working with solid electrodes, rather than with mercury for which these models have been derived.

Thermodynamics of Adsorption of Brighteners on Polarized Nickel from Watts Bath Solution

The adsorption of coumarin, nitrocoumarin, and p‐toluene sulfonamide on nickel from Watts bath solution has been studied using a polarization technique. The exchange current densities with and without additives were evaluated using a Tafel relation. The addition agents inhibited the deposition process. Surface coverages calculated from the values were fit into the Langmuir adsorption isotherm. Thermodynamic parameters (, , and ) for the adsorption of the addition agents have been evaluated using the Bockris‐Swinkles adsorption isotherm. The values of are negative indicating the strong interaction and reactive inhibition of the deposition process by these additives. The electrodeposition interaction is discussed from the viewpoint of the adsorption of the additive molecules on the metal solution interface.

Retardation of the Cd2+ and In3+ Reduction Processes at DME in Chloride Medium in Relation to Adsorption of Coumarin

The adsorption of coumarin on mercury in MKC1 has been determined from electrocapillary and capacitance measurements. At relatively high coumarin concentrations (≥ 10−3 M), the molecules reorient from the parallel to the vertical form at the more negative potentials. The results were found to fit the isotherm having a configurational term θ/ex-1(1-θ)x. From the values calculated for the standard free energy of adsorption and its variation with potential, it may be inferred that coumarin is not strongly adsorbed. In presence of coumarin, the Cd2+/Cd(Hg) and ln3+/ln(Hg) exchange reactions occur through the free surface, and the decrease in the rate constant is exponentially related to the surface coverage.

The adsorption of coumarin at a mercury electrode and its effect on metal-deposition potentials

The orientation of coumarin molecules adsorbed at a mercury surface depends on potential, coumarin concentration and ionic strength of the electrolyte. At positive potentials the adsorbed molecules are arranged with the plane of the ring parallel to the mercury surface; as the potential is made more negative, the molecules become perpendicular and finally desorb. The potentials at which these changes occur become more positive as the concentration of swamping electrolyte is increased. The effect of the adsorbed film on metal-deposition potentials has been interpreted quantitatively in terms of the transfer of charge through a layer of dipoles at the cathode/solution interface.