Infrared reflectance absorption spectroscopy (IRRAS). Study of the thermal stability of perfluorinated sulphonic acid ionomers on Pt

Spectroscopic profiling, DFT computations, molecular docking and molecular dynamic simulation of biologically active 5-isoquinolinesulfonic acid

The title compound 5-isoquinolinesulfonic acid (5IQSA) is characterized using the FT-IR, FT-Raman, NMR and UV-Vis spectra. The optimized molecular geometry, vibrational assignments, infrared intensities and Raman scattering are precisely calculated using Density Functional Theory (DFT) with the B3LYP/6-311++G(d,p) basis set. The ¹H and ¹³C NMR chemical shifts are computed and compared with the experimental data. The TD-DFT/M062X/6-311++G(d,p) method is used to compute UV-Vis for different solvents, and the results are compared to UV-Vis spectra obtained experimentally. The HOMO-LUMO band gap energy is calculated for various solvents and compared to the band gap of UV-Vis spectra. Molecular dynamics simulations are used to investigate the biomolecular stability. Non-Linear Optical (NLO) behaviour has been illustrated using hyperpolarizability calculations. Topological studies such as Reduced Gradient Density (RDG), Electron Localization Function (ELF) and Localized Orbital Locator (LOL) are performed. The Molecular Electrostatic Potential (MEP), Natural Bond Orbital (NBO) analysis, Fukui functions and thermodynamic properties were analysed. To explore the biological behaviour of the examined compound, molecular docking was performed to evaluate the hydrogen bond distance and binding energies with (2XA4) kinase inhibitor protein.Communicated by Ramaswamy H. Sarma.

Transport Properties of Perfluorosulfonate Membranes Ion Exchanged with Cations

In this work, the properties of univalent, that is, Li⁺, Na⁺, NH₄⁺, and TEA⁺ form perfluorosulfonate (PFSA) membranes are studied and compared to the properties of H⁺ form materials. Properties of these polymer membranes including water uptake, density and conductivity, were investigated for membranes exposed to various water activity levels. The water uptake by the membranes decreased in the order H⁺ > Li⁺ > Na⁺ > NH₄⁺ > TEA⁺, the same order as the hydration enthalpy (absolute values) of cations. Conductivity values did not strictly follow this order, indicating the importance of different factors besides the hydration level. The partial molar volume of water is derived from the density data as a function of water content for the various membrane forms. This provides further insight into the water, cation, and polymer interactions. Factors that contribute to the conductivity of these membranes include the size of cations, the electrostatic attraction between cations and sulfonate group, and the ion-dipole and hydrogen bonding interactions between cations and water. NH₄⁺ transport is surprisingly high given the low water uptake in NH₄⁺ form membranes. We attribute this to the ability of this ion to develop hydrogen bonded structures that helps to overcome electrostatic interactions with sulfonates. Pulsed-field gradient (PFG) nuclear magnetic resonance (NMR) was used to measure the diffusion coefficient of water in the membranes. FT-IR spectroscopy is employed to probe cation interactions with water and sulfonate sites in the polymer. Overall, the results reflect a competition between the strong electrostatic interaction between cation and sulfonate versus hydration and hydrogen bonding which vary with cation type.

Ligand effect of SnO2 on a Pt–Ru catalyst and the relationship between bond strength and CO tolerance

Pt–Ru/SnO₂/C catalysts were prepared by a rapid quenching method.

In situ Infrared Reflection Absorption Spectroscopy Studies of the Interaction of Nafion® with the Pt Electrode Surface

Infrared Reflection Absorption Spectroscopy (IRRAS) has been applied to study the nature of the co-ordination of Nafion® to a Pt electrode surface. The experiments have been carried out using a Pt electrode coated with a thin film of Nafion® assembled into a thin layer spectroelectrochemical cell. The potential modulation or the subtractively normalized interfacial Fourier transform infrared reflection spectroscopy (SNIFTIRS) experiments have been performed, in order to distinguish between the bulk properties of the Nafion® membrane and the properties of the membrane at the interace with the Pt electrode. The results showed that the interaction between the membrane and a Pt electrode resembles the interaction between a Pt electrode and a sulfuric acid solution.

Langmuir--Schaefer films of Nafion with incorporated TiO(2) nanoparticles

An easy method of incorporating TiO(2) nanoparticles into Nafion perfluorinated ionomer is proposed. Ultrathin films of Nafion were prepared by employing the Langmuir-Schaefer (LS) technique. The pressure-area isotherm study of a Langmuir monolayer of Nafion at the air-water interface on different concentrations of NaCl as the subphase allowed us to find the best experimental conditions for the deposition of stable Langmuir-Schaefer films. Incorporation of TiO(2) nanoparticles was performed by dipping Nafion LS films in a solution of TiO(2) nanoparticles. The uniformity of the TiO(2) incorporation was detected by UV-visible spectroscopy. The morphology of the Nafion, Nafion/TiO(2) nanoparticles thin films, and the changes due to the annealing procedure were investigated by atomic force microscopy. Interestingly, the AFM investigation showed that Nafion and Nafion/TiO(2) LS films have thermal stability up to 600 degrees C.