Mass measurements of short-lived nuclides using the Isoltrap preparation Penning trap

For exotic nuclear species, short decay half-lives make precision mass measurements particularly challenging. Combining isobaric purification and the mass measurement in the same trap may offer an interesting compromise between losses due to half-life and measurement precision. Here we discuss a mass measurement performed in a preparation Penning trap, and perform a study of the resonance lineshape.     

Microwave-assisted hydrolysis and extraction of tricyclic antidepressants from human hair

The objective of this research was to develop, optimize, and validate a modern, rapid method of preparation of human hair samples, using microwave irradiation, for analysis of eight tricyclic antidepressants (TCADs): nordoxepin, nortriptyline, imipramine, amitriptyline, doxepin, desipramine, clomipramine, and norclomipramine. It was based on simultaneous alkaline hair microwave-assisted hydrolysis and microwave-assisted extraction (MAH–MAE). Extracts were analyzed by high-performance liquid chromatography with diode-array detection (HPLC–DAD). A mixture of n-hexane and isoamyl alcohol (99:1, v/v) was used as extraction solvent and the process was performed at 60°C. Application of 1.0 mol L⁻¹ NaOH and microwave irradiation for 40 min were found to be optimum for hair samples. Limits of detection ranged from 0.3 to 1.2 μg g⁻¹ and LOQ from 0.9 to 4.0 μg g⁻¹ for the different drugs. This enabled us to quantify them in hair samples within average therapeutic concentration ranges.     

p‐Nitrobenzoic Acid Adsorption on Nanostructured Gold Surfaces Investigated by Combined Experimental and Computational Approaches

Adsorption of guest molecules on host surfaces can lead to dramatic changes in the spectral properties of the guest. One such effect is surface‐enhanced infrared absorption (SEIRA), observed when the guest is adsorbed on, for example, thin films, metal surfaces, or nanotubes. p‐Nitrobenzoic acid (p‐NBA) exhibits a SEIRA effect when adsorbed on Ag and Au. Herein, the IR spectra of p‐NBA adsorbed on a homemade rough Au surface, recorded in reflection mode with an angle of incidence of 16.5°, are reported. This SEIRA experiment reveals more bands than found by previous SEIRA studies. The intensities of both symmetric and asymmetric COO^? and NO₂ stretching, in‐plane CH, and C?C ring stretching modes are enhanced. Theoretical models constructed on the basis of density functional theory reveal the binding mode of p‐NBA to gold “particles”. The p‐NBA anion binds to gold much more strongly than the neutral form, and interaction via the carboxylic oxygen atoms is preferred over the nitro group–gold contact. A significant charge transfer during chemisorption is found, which is considered to be crucial in leading to a high SEIRA enhancement factor.     

Oligomerization oscillations of L-lactic acid in solution

We employ high-performance liquid chromatography with diode array, evaporative light scattering, and mass spectrometric detection to monitor the oligomerization of L-lactic acid in pure acetonitrile and in 70% aqueous ethanol. The production of higher oligomers appears to proceed in an oscillatory fashion. A model is presented that involves the formation of aggregates (micelles), which catalyze the oligomerization.     

Tuning the hydrogen-bonding strength in 2,6-bis(cycloalkylcarbonylamino)pyridine assemblies by variable flexibility. Association constants measured by hydrogen-bonded vs. non-hydrogen-bonded protons

The association of 2,6-bis(cycloalkylcarbonylamino)pyridines with rigid and non-rigid counterparts in chloroform solution was studied using ¹H NMR and computational methods. The angles within the cycloalkyl ring and the rotation of these substituents determine the strength of the association via triple hydrogen bonding. The dimerisation and methyl–methyl repulsion have been addressed as mechanisms restricting heterocomplexation of diacetamide. The association constants obtained by the shift changes of hydrogen-bonded protons are in agreement with those of methine protons. This ‘dual shift’ method was proposed as an additional verification of association constants obtained generally by amino protons.     

Experimental and theoretical NMR and IR studies of the side-chain orientation effects on the backbone conformation of dehydrophenylalanine residue

Conformation of N-acetyl-(E)-dehydrophenylalanine N', N'-dimethylamide (Ac-(E)-ΔPhe-NMe(2)) in solution, a member of (E)-α, β-dehydroamino acids, was studied by NMR and infrared spectroscopy and the results were compared with those obtained for (Z) isomer. To support the spectroscopic interpretation, the Φ, Ψ potential energy surfaces were calculated at the MP2/6-31 + G(d,p) level of theory in chloroform solution modeled by the self-consistent reaction field-polarizable continuum model method. All minima were fully optimized by the MP2 method and their relative stabilities were analyzed in terms of π-conjugation, internal H-bonds and dipole interactions between carbonyl groups. The obtained NMR spectral features were compared with theoretical nuclear magnetic shieldings, calculated using Gauge Independent Atomic Orbitals (GIAO) approach and rescaled to theoretical chemical shifts using benzene as reference. The calculated indirect nuclear spin-spin coupling constants were compared with available experimental parameters.     

Secondary electron microscopy and transmission electron microscopy studies of carbon nanotubes in C-Ni films

Carbon nanotubes films have been studied with SEM and TEM. The studied films were obtained using a two step method: PVD process and CVD process. Strongly defected and curled carbon nanotubes containing Ni nanoparticles formed the film with thickness of about 300–400 nm. Observed carbon nanotubes were of lengths from 100 nm to 300 nm and did not stick to each other.     

Indirect Raman identification of the proton insertion in the high‐temperature [Ba/Sr][Zr/Ti]O3‐modified perovskite protonic conductors

OH⁻ and H₃O⁺ species in hydrates and simple oxides are rather well characterised from their IR, Raman and inelastic neutron points of view. For the H⁺ (H₂O) species in solid state the variability is well established and assignment remains discussed. The question of the vibrational signature of isolated proton (e.g. the ionic proton, a proton sharing its interaction with more than two acceptors) and its dynamic nature (proton gas, polaron,…) is open. H⁺‐containing modified perovskites A(Ba,Sr,…) B(Zr,Ce,Ti,…) O₃ are potential ceramic membranes for fuel cell and medium temperature water electrolysis (300–800 °C). Comparison studies of the protonated and non‐protonated lanthanide/rare earth‐modified perovskites of type Ba(Sr)Zr(Ti)O₃ as well as Al‐modified BaTiO₃ show that a broad component centred at 2500 cm⁻¹ is observed after ‘proton insertion’. Its intensity is correlated to the protonic species content as well as to the conductivity of the materials. The mixed nature of this feature is discussed: fluorescence related to the dangling bonds, A, B, C bands or new phenomena related to the ionic protons and associated electronic defect. Copyright © 2008 John Wiley & Sons, Ltd.     

Partial Methane Oxidation to Methanol on Ru-Porphyrins – on the Role of Non-Innocent Ligands and Spin Crossover

The partial oxidation reaction of CH₄ led to the formation of CH₃OH in the presence of Ru-porphyrin oxo complexes (denoted as POR, POR-O and POR-OH where in the case of the last two, oxygen atom and the OH group were attached to the active site, respectively), in which Ru was present on different oxidation states. The simulations were performed based on Density Functional Theory (DFT) with extended geometric and electronic structure analyses of each reaction step. Moreover, the reaction pathways were investigated in different spin states. The Spin Crossover (SCO) phenomenon was found to play an important role in the kinetics of the reaction in the presence of POR and POR-O. Harmonic Oscillator Model of Aromaticity (HOMA) index was applied for different spin states to estimate the aromaticity changes of the pyrrole rings in the Ru-porphyrin complexes. In order to characterize the nature of bonding, the Natural Bond Orbitals (NBO) analysis including the Wiberg Bond Index (WBI) and Natural Population Analysis (NPA) was carried out. Finally, the Non-Covalent Interactions (NCI) index was employed to gain insight into interactions between the components of the reaction. It was found that the non-covalent interactions cannot be neglected in the studied reaction paths.