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Density Functional Theory Study on Propane and Propene Adsorption on Pt(111) and PtSn Alloy Surfaces
2011
Density functional theory calculations were performed to investigate the adsorption of propane, propene, and C and H atoms on Pt and PtSn surfaces employing the revised Perdew–Burke–Ernzerhof (RPBE) and vdW-DF functionals. Propane adsorption was found to be mediated by van der Waals interactions without significant site preference on any of the studied surfaces. The adsorption characteristics of propene are different: On the Pt(111) and Pt3Sn(111) surfaces, propene adsorption is covalent, and the molecule prefers a di-σ site to a π site. Alloying Pt(111) with Sn leads to weaker adsorption owing to geometric and relaxation effects, whereas electronic effects are found to be small. On the PtS…
Solvent-Independent Electrode Potentials of Solids Undergoing Insertion Electrochemical Reactions: Part I. Theory
2012
A formally solvent-independent redox system can be theoretically defined using the Lovric and Scholz modeling of the voltammetry of microparticles for ion-insertion solids. The proposed theory is based on the extra-thermodynamic assumptions that no net charge accumulates at the solid|electrolyte interface and the assumption that the structure of the solid and the ion binding remain unaffected by the solvent. Under voltammetric conditions, the corresponding redox potential can be estimated from voltammetric and chronoamperometric data assuming electrochemical reversibility and diffusive charge transport in the solution and solid phases, also taking into account ion partition (electrolyte/sol…
Electrosynthesis of Poly(alanine)-Like Peptides in Concentrated Alanine Based Electrolytes, Characterization Coupled to DFT Study and Application to …
2014
The anodic oxidation of concentrated l-alanine on smooth electrodes such as platinum and glassy carbon electrodes was studied. Contrary to the previous studies performed up to now with diluted l-alanine, the electrochemical process generated here results in a completely different situation. The oxidation on smooth platinum was carried out by electrochemical quartz crystal microbalance (EQCM) coupled to cyclic voltammetry technique. The effects of concentration, scan rate, and pH (zwitterion at pH = 6 and alkaline media at pH = 13) on potential values were examined. Glassy carbon and smooth gold electrodes showed the same behavior as on smooth platinum electrode. Spectroscopic analysis such …
Investigations of TiO2 films deposited by different techniques
1991
High refractive TiO2 films deposited by reactive electron beam evaporation, reactive ion plating and dip coating have been characterized by optical spectroscopy, electron spectroscopy for chemical analysis, Rutherford backscattering spectroscopy, nuclear reaction analysis and Raman spectroscopy. The spectral refractive index n exhibits a strong dependence on the deposition conditions. These findings will be connected to variations in density, stoichiometry, hydrogen content (H2O) and binding structure of the layers. A strong correlation is found between optical quantities and microscopic properties of TiO2 films.
Photoinduced ultrafast dynamics of Ru(dcbpy)2(NCS)2-sensitized nanocrystalline TiO2 films:The influence of sample preparation and experimental condit…
2004
In most of the previous ultrafast electron injection studies of Ru(dcbpy)2(NCS)2-sensitized nanocrystalline TiO2 films, experimental conditions and sample preparation have been different from study to study and no studies of how the differences affect the observed dynamics have been reported. In the present paper, we have investigated the influence of such modifications. Pump photon density, environment of the sensitized film (solvent and air), and parameters of the film preparation (crystallinity and quality of the film) were varied in a systematic way and the obtained dynamics were compared to that of a well-defined reference sample: Ru(dcbpy)2(NCS)2−TiO2 in acetonitrile. In some cases, …
Chemical Reactivity in AOT Microemulsions: Kinetics of Water Replacement in a Square-Planar Palladium(II) Aquo Complex by Monoalkylthioureas
1998
The kinetics of water replacement in the cationic palladium(II) aquo complex [Pd(Et4dien)(H2O)]2+, where Et4dien = Et2N(CH2)2NH(CH2)2NEt2, by thiourea, methylthiourea, and ethylthiourea have been studied at 25.0 °C in heptane−AOT−water microemulsion over a wide range of the molar ratio R (=[H2O]/[AOT]) at the constant surfactant concentration of 0.13 mol dm-3. The reaction rates are significantly higher in microemulsions than in bulk water and decrease rapidly as the parameter R increases. The kinetic data, interpreted quantitatively by applying the pseudophase model to the microemulsion, indicate that there is a weak partitioning of the nucleophiles between the water core and the AOT inter…
Femtosecond Transient Absorption Study of the Dynamics of Acrylodan in Solution and Attached to Human Serum Albumin
2003
The excited-state relaxation dynamics of the protein-labeling dye acrylodan in solution and attached to human serum albumin has been studied by femtosecond transient absorption spectroscopy. Time-resolved spectra and kinetics of stimulated emission and excited-state absorption in the wavelength region from 400 to 800 nm were studied in ethanol and dimethylformamide. The excited-state solvation dynamics is characterized by multiexponential behavior in both solvents. In ethanol solution, the time dependence of the transient spectra is interpreted in terms of fast solvent relaxation followed by excited-state isomerization of the dye. Acrylodan attached to the protein shows a relaxation compone…
Understanding Digestive Ripening of Ligand-Stabilized, Charged Metal Nanoparticles
2017
Most syntheses of thiolate-protected metal nanoparticles (NPs) include a thermochemical step in which the as-prepared, polydisperse NPs are transformed to a narrower size distribution in a poorly understood process known as digestive ripening (DR). Previous theoretical approaches considered either surface and electrostatic contributions or surface and ligand-binding contributions. We show that the three contributions are needed to obtain theoretical predictions in agreement with experimental observations. Although statistical thermodynamics does not clarify mechanistic details, it certainly provides valuable insights on the DR process. Remarkably, a relatively simple theory with no fitting …
Paramagnetic aluminium β-diketiminate
2012
The β-diketiminate ligand framework is shown to undergo reduction to form a neutral main group radical stabilized by spiroconjugation of the unpaired electron over the group 13 element centre. The synthesized paramagnetic complex was characterized by EPR spectroscopy and computational chemistry.
Vibrational Circular Dichroism of Thiolate-Protected Au25 Clusters: Accurate Prediction of Spectra and Chirality Transfer within the Mixed Ligand She…
2019
We have prepared Au25(PET)18-2x((R)-FBI-NAS)x(PET = 2-phenylethylthiol, (R)-FBINAS = (R)-5,5',6,6',7,7',8,8'-octafluoro-[1,1'-binaphthalene]-2,2'-dithiol) mixed ligand shell clusters via ligand exchange. Two fractions with different composition of the ligand shell were separated using size-exclusion chromatography and studied by infrared (IR) spectroscopy and vibrational circular dichroism (VCD). Both IR and VCD spectra are dominated by FBINAS vibrations although PET is more abundant on the cluster. Calculated VCD spectra on a model cluster Au25(SH)16(FBINAS)1 depend on the charge state of the cluster, and the anion is in excellent agreement with the experimental spectra of the Au25(PET)18-…