Characterization of PEO-lithium triflate polymer electrolytes: Conductivity, DSC and Raman Investigations

Polymeric membranes to be used as electrolytic separators in lithium batteries were prepared from Poly Ethylene Oxide (PEO) and Lithium Triflate salt (LiTf) via a solventfree procedure. Several membranes, having different PEO/LiTf molar ratios, were characterized by Electrochemical Impedance Spectroscopy (EIS) to obtain their ionic conductivity. Most of the compositions exhibit an Arrhenius-like behaviour with two different activation energies above and below 60 °C. Only the sample having the highest LiTf concentration showed a non-Arrhenius trend. Differential Scanning Calorimetry (DSC) study was performed to determine the various phases present in the system. The degree of association of the mobile ions changes vs. composition and temperature was investigated by Raman spectroscopy, a powerful technique which allows to follow these changes in details by studying the spectral parameters of the SO₃ stretching vibration of triflate ions. These data were correlated with the conductivity and thermodynamic data. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Morphology and electronic structure of nanostructured carbon films embedding transition metal nanoparticles

Inclusions of metals in the growth process of carbon cluster assembled materials (ns-C) induce modifications in the structural and electronic properties of the material. A novel pulsed microplasma cluster source (PMCS) is able to deliver highly intense, collimated and stable beams suitable for producing bulk quantities of cluster-assembled nanocomposite films. Loading of metal nanoparticles into carbon cluster based films is obtained either by mixing a gas phase metallorganic compound with the carrier gas (He) before entering into the source (for example molybdenum (V) isopropoxide), or by using a double component sputtering target (metal (Ti, Ni)/graphite). The study of film morphology on nanometer scale, carried out by transmission electron microscopy (TEM), reveals the dispersion in a ns-C matrix of metallic particles and, in the case of molybdenum containing films, also of carbide particles. Spatially resolved ultraviolet photoemission spectroscopy confirms the segregation of metal particles and exhibits evident anisotropy in the Mo:ns-C films, mainly ascribable to the formation of carbide nanoparticles.     

Radiative coupling of high-order plasmonic modes with far-field

In the last few years, hybrid systems consisting of punctual sources and metallic nanostructures have been assembled and studied. Furthermore, the radiative coupling between the two counterparts has become a crucial aspect to be explored in nanophotonics and plasmonics. In this paper a numerical framework based on the Discrete Dipole Approximation is presented as a simple computational scheme to analyze the decay dynamics of an emitter when it is located in the near proximities of metallic nanoparticles. This approach allows to go beyond the analytically solved cases and to predict the optical response of more complex shaped nanoparticles. Here the excitation of dipole and higher-order modes is studied as a function of the applied radiation with a particular attention paid to the changes induced in the response by approaching the source to the metal. Numerical results, obtained for Ag spheroids and conically shaped nanoparticles, are explained by analyzing the charge density induced on the surface of the nanoparticles, this allowing to distinguish dark from radiative modes in a straightforward way.     

Spectroscopic and Molecular Docking Study of the Interaction between Neutral Re(I) Tetrazolate Complexes and Bovine Serum Albumin

Re(I) complexes have potential in biomedical sciences as imaging agents, diagnostics and therapeutics. Thus, it is crucial to understand how Re(I) complexes interact with carrier proteins, like serum albumins. Here, two neutral Re(I) complexes were used (fac-[Re(CO)₃(1,10-phenanthroline)L], in which L is either 4-cyanophenyltetrazolate (1) or 4-methoxycarbonylphenyltetrazole ester (2) , to study the interactions with bovine serum albumin (BSA). Spectroscopic measurements, calculations of thermodynamic and Förster resonance energy transfer parameters, as well as molecular modelling, were performed to study differential binding between BSA and complex 1 and 2 . Induced-fit docking combined with quantum-polarised ligand docking were employed in what is believed to be a first for a Re(I) complex as a ligand for BSA. Our findings provide a basis for other molecular interaction studies and suggest that subtle functional group alterations at the terminal region of the Re(I) complex have a significant impact on the ability of this class of compounds to interact with BSA.     

Shifting Towards αVβ6 Integrin Ligands Using Novel Aminoproline-Based Cyclic Peptidomimetics

In recognition of the key role played by integrins in several life-threatening dysfunctions, the search for novel small-molecule probes that selectively recognize these surface receptors is still open and widely pursued. Inspired by previously established aminoproline (Amp)-RGD based cyclopeptidomimetics with attracting α_Vβ₃ integrin affinity and selectivity, the design and straightforward synthesis of 18 new AmpRGD chemotypes bearing additional structural variants were herein implemented, to shift toward peptide-like α_Vβ₆ integrin targeted binders. The ligand competence of the synthesized products toward α_Vβ₆ was evaluated in competitive binding assays on isolated receptors, and α_Vβ₆/α_Vβ₃ selectivity was determined for a subgroup of compounds, resulting in the identification of four very promising candidates. SAR considerations and docking simulations allowed us to appreciate the key structural features responsible for the observed activity.     

Antimicrobial Activity of MgB2 Powders Produced via Reactive Liquid Infiltration Method

We report for the first time on the antimicrobial activity of MgB₂ powders produced via the Reactive Liquid Infiltration (RLI) process. Samples with MgB₂ wt.% ranging from 2% to 99% were obtained and characterized, observing different levels of grain aggregation and of impurity phases. Their antimicrobial activity was tested against Staphylococcus aureus ATCC BAA 1026, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. A general correlation is observed between the antibacterial activity and the MgB₂ wt.%, but the sample microstructure also appears to be very important. RLI-MgB₂ powders show better performances compared to commercial powders against microbial strains in the planktonic form, and their activity against biofilms is also very similar.     

Chaotic phenomena of charged particles in crystal lattices

In this article, we have applied the methods of chaos theory to channeling phenomena of positive charged particles in crystal lattices. In particular, we studied the transition between two ordered types of motion; i.e., motion parallel to a crystal axis (axial channeling) and to a crystal plane (planar channeling), respectively. The transition between these two regimes turns out to occur through an angular range in which the particle motion is highly disordered and the region of phase space spanned by the particle is much larger than the one swept in the two ordered motions. We have evaluated the maximum Lyapunov exponent with the method put forward by Rosenstein et al. [Physica D 65, 117 (1993)] and by Kantz [Phys. Lett. A 185, 77 (1994)]. Moreover, we estimated the correlation dimension by using the Grassberger-Procaccia method. We found that at the transition the system exhibits a very complex behavior showing an exponential divergence of the trajectories corresponding to a positive Lyapunov exponent and a noninteger value of the correlation dimension. These results turn out to be linked to a physical interpretation. The Lyapunov exponents are in agreement with the model by Akhiezer et al. [Phys. Rep. 203, 289 (1991)], based on the equivalence between the ion motion along the crystal plane described as a "string of strings" and the "kicked" rotator. The nonintegral value of the correlation dimension can be explained by the nonconservation of transverse energy at the transition.     

Effects of predosed oxygen and hydrogen on CO adsorption on Ni(1 0 0)

We present the results of high-resolution electron energy loss experiments on (CO/O)/Ni(1 0 0) and (CO/H)/Ni(1 0 0) systems. Oxygen and hydrogen interact differently with Ni(1 0 0) surface, nevertheless, both species do not affect to a great extent the vibrational properties of CO. A phase of CO molecules weakly bonded to the surface and unaffected by coadsorbed oxygen and hydrogen, is found. Coverage of 0.5 ML of predosed oxygen chemically passivates the Ni(1 0 0) surface and inhibits any CO adsorption at room temperature. CO sites are unambiguously determined for each predosed Ni(1 0 0) surface.