A fast-neutron coincidence collar using liquid scintillators for fresh fuel verification

Journal of Radioanalytical and Nuclear Chemistry - The IAEA has developed a liquid scintillator-based system for the non-destructive assay of 235U in fresh fuel assemblies. The fast neutron...     

Potassium-doped FePc thin-film on metal surfaces: observation of different empty state occupation

Iron-Phthalocyanine molecules deposited on the Cu(119) vicinal surface form molecular chains along the vicinal surface steps, as deduced by the low-energy electron diffraction (LEED) reconstruction pattern. The work-function lowers at the FePc single-layer completion, due to the formation of an interface dipole. Further FePc deposition induces a different growth morphology, as suggested by the slope discontinuity in the work function variation. Upon depositing potassium onto the FePc thin-film prepared on Cu(119), the K-injected electrons fill up the Fe-d-associated and ligand-π-related orbitals, as observed by means of high-resolution ultraviolet photoelectron spectroscopy.     

Bulk CO oxidation on platinum electrodes vicinal to the Pt(111) surface

Bulk CO oxidation has been studied on platinum stepped surfaces belonging to the series Pt(S)[n(111) × (111)], using a hanging meniscus rotating disk electrode (HMRDE) configuration. The general shape of the voltammograms is not significantly affected by the presence of the steps. However, the curves shift towards negative values as the step density increases. Thus, in the positive-going scan, a linear relationship is observed for the dependence of the potential for the ignition peak vs the step density for surfaces with terraces wider than five atoms, shorter terraces deviate from this behavior. In the negative-going scan, a similar situation is observed for the potential where the current drops to zero. In this case, Pt(111) electrode also deviates from the expected behavior because of the formation of the ordered bisulfate adlayer on the electrode. The anion readsorption process is also observed by recording the HRMDE voltammograms at a high scan rate. All these results have been analyzed in light of a common mechanism, discussing the possible role of the steps in the stability and reactivity of the CO adlayer. In memoriam of Francisco C. Nart, an excellent scientist, colleague, and friend.     

Effects of Ni catalyst–substrate interaction on carbon nanotubes growth by CVD

An investigation of the effects of substrate type and various treatments on carbon nanotubes (CNT) growth, using an evaporated Ni thin film as a catalyst, is presented. Barrier layers of SiO₂, Si₃N₄, and TiN on Si were used as substrates. The catalyst-insulating substrate systems have been processed in several gaseous atmospheres (Ar, NH₃ and H₂) and in the temperature range 700–900 °C, in order to obtain the most appropriate morphology, size and density of catalyst particles as seeds for the subsequent CNT growth. On this kind of substrates, the smallest nanoparticles were obtained on SiO₂ layers, in H₂ or NH₃ atmosphere even at 700 °C. However, the best vertically aligned and well-graphitized CNT resulted from the NH₃ annealing process, followed by the CNT deposition at 900 °C in C₂H₂ and H₂.On TiN conducting substrates, the best vertically aligned CNT were deposited using a shorter annealing step and a deposition process at reduced pressure. The samples were characterized by means of scanning electron microscopy (SEM) and Raman spectroscopy analysis.     

Regiospecific total synthesis of 6-deoxyanthracyclines

Regiospecific approaches to 6-deoxyanthracyclinones, which have resulted in the synthesis of the novel anthracyclines 4-demethoxy-6-deoxydaunorubicin (2) and 6-deoxycarminomycin (3), are reported. The construction of the aglycone 4 is based on the coupling of l,4-dimethoxy-2-lithionaphthalene (10) to 1 formyl-2-carbomethoxy-4-acetylcyclohexane thioketal (11). A new improved regioselective route, which allows the preparation of 6-deoxyanthracyclinones bearing also substituents in ring Das illustrated by 5, 'a based on the coupling of 10a and of l,4,5-trimethoxy-3-lithionaphthalene (10b) to lactone 28.     

The role of adsorbates in electrocatalytic systems: An analysis of model systems with single crystals

The use of single crystal electrodes as model catalysts has been widely applied for the study of several reactions. The known structure of the surface provides a system with controlled electronic properties that helps in the understanding of the mechanism of reactions. In this model system, any modification, including the adsorption of anions, organic molecules or foreign atoms, generate changes in the electronic properties of the surface and, thus, in the adsorption energy of the species involved in the studied reaction. The adsorbate can hinder the surface and diminish the activity or prevent the oxidation of the surface and improve the catalysis. The changes in electronic properties can modify the adsorption energy and enhance or worsen the catalytic activity. The effect of any adsorbed species will depend on the structure of the surface, the nature of the species and the studied reaction.     

Stereospecific epoxidation of anthracyclinones: a route to 8(r)-methoxydaunomycinone

Stereoselective epoxidation of $\text{1}$, the 7,8-unsaturated derivative of daunomycinone, followed by $\text{trans}$ opening of the epoxide $\text{2}$, afforded 8(R)-methoxydaunomycinone $\text{6a}$; its configuration at C-8 was determined by chemical correlation and PMR studies.