Spontaneous deposition of Pt‐nanoparticles on HOPG surfaces

Pt nanoparticles were spontaneously generated by immersion of a highly ordered pyrolytic graphite substrate in a 1 mM H₂PtCl₆ + 0.05 M H₂SO₄ plating solution using different immersion times, modifying both size and density of the deposits. Atomic force microscopy images show Pt particles distributed preferentially on surface defects of the electrode, increasing their size and density with deposition time. Scanning electronic microscopy/energy‐dispersive X‐ray spectroscopy images confirmed the formation of Pt deposits after 2 h immersion, forming irregular agglomerates with different sizes distributed over the surface. The open circuit potential studies showed potentials close to the corresponding PtCl₆^2?/Pt and PtCl₄^2?/Pt couples, which would indicate that some of these processes took place at the interface. The voltammetric response of the supported Pt nanoparticles showed an increase in current density towards the hydrogen evolution reaction being more pronounced for deposits formed after an immersion time of 2 h. In this case, the voltammetric behavior was similar to polycrystalline Pt. Copyright © 2015 John Wiley & Sons, Ltd.     

ChemInform Abstract: Prediction and Synthesis of a Non‐Zintl Silicon Clathrate.

High‐throughput DFT calculations are used to predict the thermodynamic stability of ternary type I Si clathrates.     

Analysis of adenosine by RP-HPLC method and its application to the study of adenosine kinase kinetics

An RP-HPLC method for the analysis of adenosine (ADO) has been developed and validated. In the present study, we report an RP-HPLC-based method with modifications of mobile phase and shorter retention time that substantially improved the efficiency of ADO analysis. The HPLC separation of the ADO was achieved on a C18 column, using a mobile phase consisting of water, containing 7% v/v ACN, at a flow rate of 0.8 mL/min. The column effluent was monitored by UV detection at 260 nm. A linear response was achieved over the concentration range of 0.25-100.00 micromol/L. The analytical method inter- and intra-run accuracy and precision were better than +/- 15%. The LOQ was 0.25 micromol/L, with ADO detection in the range of 6.25 pmol per sample. The method has been applied to the study of adenosine kinase (AK) kinetics.     

Development of an analytical method for the determination of the residues of four pyrethroids in meat by GC–ECD and confirmation by GC–MS

The development of an analytical method for the determination of four selected pyrethroid insecticides at residue level in beef meat is presented. Acetone and petroleum ether at 40-60 degrees C were chosen as extraction solvents. A two-step clean-up was performed using an Extrelut NT3-C(18) system followed by a Florisil column, with disposable, ready-to-use cartridges. Instrumental analysis was carried out on a gas chromatograph equipped with an electron capture detector (GC-ECD), using matrix-matched and internal standard calibration techniques. Confirmatory analysis by GC-MS was performed. Recoveries at the EU Maximum Residue Limit (MRL), 0.5 x MRL and 1.5 x MRL levels and the repeatabilities were widely satisfactory. The main advantage of the method was the reduction of analysis time as compared with previously published works. The applicability of the method to different matrices and pesticide classes will be investigated.     

A2A Adenosine Receptor Antagonists: Are Triazolotriazine and Purine Scaffolds Interchangeable?

The A_2A adenosine receptor (A_2AAR) is one of the four subtypes activated by nucleoside adenosine, and the molecules able to selectively counteract its action are attractive tools for neurodegenerative disorders. In order to find novel A_2AAR ligands, two series of compounds based on purine and triazolotriazine scaffolds were synthesized and tested at ARs. Compound 13 was also tested in an in vitro model of neuroinflammation. Some compounds were found to possess high affinity for A_2AAR, and it was observed that compound 13 exerted anti-inflammatory properties in microglial cells. Molecular modeling studies results were in good agreement with the binding affinity data and underlined that triazolotriazine and purine scaffolds are interchangeable only when 5- and 2-positions of the triazolotriazine moiety (corresponding to the purine 2- and 8-positions) are substituted.     

Ethene/propene copolymerisations with rac-EBTHIZrR2/alumoxane: σ-ligands effect

We report here about the role played by the σ-ligands of a metallocene in ethene/propene (E/P) copolymerisations promoted by rac-[ethylenebis(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride 1, and its corresponding dimethyl derivative rac-EBTHIZrMe₂ 2 and binaphtholate rac-EBTHIZr(BNP) 3 derivative, in the presence of several alumoxanes.

Alumoxanes alternative to the traditional polymethylalumoxane (MAO) were synthesised and characterised. They are based on Al(2,4,4-trimethylpentyl)₃ (TIOA) 4 and were prepared by reaction of 4 with water to give either tetraisooctylalumoxane (TIOAO) 5 or polyisooctylalumoxane (TAO) 6 depending on the stoichiometry of the reaction. ¹H NMR spectra of these products are characterised by the presence of broad bands and of resolved multiplets. Their relative amount in the region between 1.9 and 2.5 ppm was identified as the “fingerprint” of the polymerisation activity. A comparison of the results obtained in polymerisation with metallocenes having different σ-ligands allowed us to shed more light on the role played by those species.

In conclusion, the nature of the σ-ligands of a metallocene affects its catalytic activity in polymerisation, as a function of the alumoxane employed and of the relative ratio with the metallocene, and this effect is enhanced in “critical conditions,” i.e. with a weakly activating cocatalyst or at a low Al/Zr ratio.     

Electrochemical sensors for oxidative stress monitoring

Electrochemical sensors are ideally suited for the detection of reactive oxygen and nitrogen species (ROS and RNS) generated during biological processes. This review discusses the latest work in the development of electrochemical microsensors for ROS/RNS and their applications for monitoring oxidative stress in biological systems. The performance of recent designs of microelectrodes and electrode materials is discussed along with their functionality in preclinical models of drug efficacy, mitochondrial distress, and endothelial dysfunction. Challenges and opportunities in translating this methodology to study the pathophysiology associated with various diseases are discussed.     

A New Photoactivatable Ruthenium(II) Complex with an Asymmetric Bis-Thiocarbohydrazone: Chemical and Biological Investigations

The synthesis, photoactivation and biological activity of a new piano-stool Ru(II) complex is herein reported. The peculiarity of this complex is that its monodentate ligand which undergoes the photodissociation is an asymmetric bis-thiocarbohydrazone ligand that possesses a pyridine moiety binding to Ru(II) and the other moiety contains a quinoline that endows the ligand with the capacity of chelating other metal ions. In this way, upon dissociation, the ligand can be released in the form of a metal complex. In this article, the double ability of this new Ru(II) complex to photorelease the ligand and to chelate copper and nickel is explored and confirmed. The biological activity of this compound is studied in cell line A549 revealing that, after irradiation, proliferation inhibition is reached at very low half maximal inhibitory concentration (IC₅₀) values. Further, biological assays reveal that the dinuclear complex containing Ni is internalized in cells.     

High-pressure structures of disilane and their superconducting properties

A systematic ab initio search for low-enthalpy phases of disilane (Si2H6) at high pressures was performed based on the minima hopping method. We found a novel metallic phase of disilane with Cmcm symmetry, which is enthalpically more favorable than the recently proposed structures of disilane up to 280 GPa, but revealing compositional instability below 190 GPa. The Cmcm phase has a moderate electron-phonon coupling yielding a superconducting transition temperature T(c) of around 20 K at 100 GPa, decreasing to 13 K at 220 GPa. These values are significantly smaller than previously predicted T(c))s for disilane at equivalent pressure. This shows that similar but different crystalline structures of a material can result in dramatically different T(c)'s and stresses the need for a systematic search for a crystalline ground state.     

Dirichlet‐to‐Neumann Map for a Nonlinear Diffusion Equation

A nonlinear diffusive equation with moving boundaries is analyzed by constructing the corresponding Dirichlet‐to‐Neumann map. In particular, the Dirichlet boundary value and the initial condition are used to derive the unknown Neumann boundary value. Then, a contraction‐mapping technique is used to prove existence and uniqueness of the solution for small times.