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This report shows the synthesis of a new family of "core-shell" carbon nitride (CN)-based electrocatalysts (ECs) for the oxygen reduction reaction (ORR) in acid medium. The ECs comprise "cores" of carbon black nanoparticles (NPs) that are covered by a CN "shell" embedding the active sites. The latter include Pt as the "active metal" and Co as the "co-catalyst." The interplay between the synthesis parameters, the chemical composition, and the ORR performance of the final ECs is elucidated. In particular, the ORR performance and reaction mechanism are studied both in an: (i) "ex-situ" setup, by means of cyclic voltammetry with thin-film rotating ring-disk electrode (CV-TF-RRDE) measurements; and (ii) "in-situ" experiment, i.e., in single proton exchange membrane fuel cells (PEMFCs) tested under operating conditions. A structural hypothesis is proposed that explains both the "ex situ" and the "in situ" ORR results on the basis of: (i) the relative amounts of the reactants used in the precursor synthesis; and (ii) the main temperature of the pyrolysis process (Tf) adopted in the preparation of the ECs. It is shown that the understanding of the fundamental features of the physicochemical processes involved in the preparation of the ECs is crucial in order to improve the proposed synthesis route and to yield ORR ECs exhibiting a performance level beyond the state of the art. [ABSTRACT FROM AUTHOR]

Silver-iron carbon nitride, which has been prepared by pyrolysis (under inert atmosphere) of silver hexacyanoferrate(II) deposited on graphene nanoplatelets, is considered here as electrocatalyst for oxygen reduction in alkaline medium (0.1 M potassium hydroxide electrolyte) in comparison to simple silver nanoparticles and iron carbon nitride (prepared separately in a similar manner on graphene nanoplatelets). The performance of catalytic materials has been examined using such electrochemical diagnostic techniques as cyclic voltammetry and rotating ring-disk electrode voltammetry. Upon application of the graphene nanoplatelet-supported mixed silver-iron carbon nitride catalyst, the reduction of oxygen proceeds at more positive potentials, as well as the amounts of hydrogen peroxide (generated during reduction of oxygen at potentials more positive than 0.3 V) are lower relative to those determined at pristine silver nanoparticles and iron carbon nitride (supported on graphene nanoplatelets), when they have been examined separately. The enhancement effect shall be attributed to high activity of silver toward the reduction/decomposition of H2O2 in basic medium. Additionally, it has been observed that the systems based on carbon nitrides show considerable stability due to strong fixation of metal complexes to CN shells.ᅟ [ABSTRACT FROM AUTHOR]

To cite some of his research activities, it should be mentioned that Roberto Marassi was a pioneer in the field of electrochemical energy storage for more than 40 years, pursuing research in such areas as molten salts or ionic liquids, Na-S batteries, Li-ion batteries, low-temperature fuel cells, and vanadium redox flow batteries, in addition to his interests in electroanalytical chemistry. But Roberto is remembered mainly for his availability to interact with other people, especially the young scientists, as well as for his sincere enthusiasm for the progress in electrochemical science and technology. Roberto Marassi was one of the scientists who, by developing new or by extending existing methods or materials, significantly advanced the understanding of electrochemical energy conversion processes as well as of the fundamentals of electrocatalysis and electroanalysis. [Extracted from the article]

ZnO nanoparticles are recently attracting a lot of interest due to their novel optical, electrical, mechanical, and chemical properties, due to surface and quantum confinement effects. A stable dispersion of ZnO nanoparticles with a uniform particle diameter of 5 nm has been synthesized via chemical precipitation. The surface of the particles has been functionalized with dodecanethiol for enhanced compatibility and dispersion in polymethylmethacrylate (PMMA). Transparent luminescent nanocomposite powders were obtained using solution mixing and solvent casting of ZnO nanoparticles in PMMA. This powder was used to produce injection-molded luminescent nanocomposites plaques. The effect of the ZnO nanoparticles on the polymer structure has been investigated by employing thermomechanical and dielectric spectroscopy analyses. [ABSTRACT FROM AUTHOR]

Agmatine, a divalent diamine with two positive charges at physiological pH, is transported into the matrix of liver mitochondria by an energy-dependent mechanism, the driving force of which is the electrical membrane potential. Its binding to mitochondrial membranes is studied by applying a thermodynamic treatment of ligand-receptor interactions on the analyses of Scatchard and Hill. The presence of two mono-coordinated binding sites S and S, with a negative influence of S on S, has been demonstrated. The calculated binding energy is characteristic for weak interactions. S exhibits a lower binding capacity and higher binding affinity both of about two orders of magnitude than S. Experiments with idazoxan, a ligand of the mitochondrial imidazoline receptor I, demonstrate that S site is localized on this receptor while S is localized on the transport system. S would act as a sensor of exogenous agmatine concentration, thus modulating the transport of the amine by its binding to S. [ABSTRACT FROM AUTHOR]

Silica-based inorganic–organic hybrid thin films embedding the organically modified oxohafnium clusters (Hf4O2(O Mc)12, O Mc=OC(O)–C(CH3)=CH2) were obtained by photo-activated free radical copolymerisation of the methacrylate groups of the cluster with those of the pre-hydrolysed (methacryloxypropyl)trimethoxysilane ( MAPTMS, (CH2=C(CH3)C(O)O)(CH2)3Si(OCH3)3). By this route, a covalent anchoring of the cluster to the forming silica network was achieved. Samples characterized by two different Si/Hf compositions (18:1, 5:1) were prepared. The surface and in-depth composition of the thin films were investigated through Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). XPS depth profiles performed on the thin layers evidenced a homogenous in depth distribution of the hafnium guest species within the whole silica films and sharp film-substrate interfaces. Broad band dielectric spectroscopy (BDS) measurements permitted to investigate the electric response of the obtained films in the frequency and temperature range of 40 Hz – 1 MHz and 0–160°C. [ABSTRACT FROM AUTHOR]

The synthesis of a new, highly photosensitive, phosphazene copolymer containing an almost-equimolecular quantity of benzophenone and methoxyethoxyethoxy substituents is reported in this paper, together with the photochemical behavior of this material when irradiated in film both in oxygen and in an argon atmosphere. It has been detected that the photoreactivity of the phosphazene material strongly depends on the light absorption process by the benzophenone moieties, whose selective excitation predominantly brings about an intramolecular hydrogen abstraction reaction from the ethylene oxide units, thus producing highly reactive phosphazene macroradicals. The coupling reactions of these species results in the complete cross-linking of the polyphosphazene substrate and in its total insolubilization. Moreover, the influence of molecular oxygen on the overall photochemical process of the benzophenone/ethyleneoxide-substituted phosphazene copolymer is investigated. The implications of the light-induced reticulation process in the controlled insolubilization of poly[ bis (methoxyethoxyethoxy)phosphazene] are also discussed. [ABSTRACT FROM AUTHOR]