Eugenio Caponetti

The static dielectric constant of solutions of water inn-alcohols at 15, 25, 35, and 45°C

Dielectric constants (measured at 1 MHz) are reported for solutions of water (concentration range 0 to 0.2 mole fraction) in 1-propanol at 25°C, and in 1-butanol, 1-pentanol, and 1-hexanol at 15, 25, 35, and 45°C. These results, together with literature values for solutions of water in methanol, ethanol, 1-heptanol, and 1-octanol, show that water interacts with alcohols in at least two ways: (1) it can participate in the formation of dynamic hydrogen-bonded chains, thereby raising the polarizability; (2) it can form relatively stable structures such as H2O(ROH)4 which have zero net dipole moment and consequently diminish volume polarizability. For CnH2n+1OH alcohols,n≥4, most of the initially added water forms complexes: consequently, addition of water to these alcohols lowers the dielectric constant.

Ce:YAG Nanoparticles Embedded in a PMMA Matrix: Preparation and Characterization

A Ce:YAG-poly(methyl methacrylate) composite was prepared using in situ polymerization by embedding the Ce:YAG nanopowder in a blend of methyl methacrylate (MMA) and 2-methacrylic acid (MAA) monomers and activating the photopolymerization using a radical initiator. The obtained nanocomposite was yellow and transparent. Its characterization was performed using transmission electron microscopy, small angle X-ray scattering, (13)C cross-polarization magic-angle spinning nuclear magnetic resonance, and photoluminescence spectroscopy. Results showed that Ce:YAG nanoparticles are well dispersed in the polymeric matrix whose structure is organized in a lamellar shape. The luminescence properties of the nanocomposite do not show quenching or a significant spectral shift, indicating that the nanocomposite can be useful for advanced applications such as white LED construction.

Synthesis, size control, and passivation of CdS nanoparticles in water/AOT/n-heptane microemulsions

Abstract CdS nanoparticles have been synthesised by adding tetrabutylammonium hydrogen sulphide to water/sodium bis(2-ethylhexyl) sulfosuccinate/ n -heptane microemulsions containing CdSO 4 . Analysis of UV–Vis absorption spectra recorded at various times indicates that an initial rapid formation of CdS nanoparticles is followed by a very slow growth process which can be well described by a power law. The growth process is totally inhibited by the addition of an appropriate amount of bis(2-ethylhexyl)amine (BEA) leading to the formation of stable nanosized CdS particles coated by an oriented monolayer of chemically bonded BEA molecules. Depending on the BEA addition time, the growth inhibition can be achieved at any moment of the process leading to an easy and fine size control. The main advantage of this procedure is that the BEA-coated CdS nanoparticles can be easily separated from the reaction medium and dispersed in nonpolar media such as heptane and in polar media such as an aqueous surfactant solution.

Suzuki-Miyaura cross-coupling of arenediazonium salts catalyzed by alginate/gellan-stabilized palladium nanoparticles under aerobic conditions in water

The use of palladium nanoparticles stabilized by natural beads made of an alginate/gellan mixture in the Suzuki-Miyaura cross-coupling reaction of arenediazonium tetrafluoroborates with potassium aryltrifluoroborates (1 : 1 molar ratio) with loading as low as 0.01–0.002 mol% under aerobic, phosphine-, and base-free conditions in water is described. The catalyst system can be reused several times without significant loss of activity.

Viscosity studies of solutions of water inn-aliphatic alcohols at various temperatures

Viscosity measurements have been made at 25°C on solutions of water inn-propanol, and at 15, 25, 35, and 45°C on solutions of water inn-butanol,n-pentanol, andn-hexanol over the respective solubility ranges. For most of the systems, water decreases the viscosity of the dry alcohols, while for the lower members of the series literature data report an increase in viscosity on addition of water. These results are rationalized in terms of two kinds of interaction between water molecules and alcohols: participation of water molecules in chain formation for the lower alcohols and formation of water-centered complexes for butanol and higher alcohols.

Oxidized graphene in ionic liquids for assembling chemically modified electrodes: a structural and electrochemical characterization study.

Dispersions of graphene oxide (GO) nanoribbons in ionic liquids, ILs (either 1-butyl-3-methylimidazolium chloride (BMIM-Cl-) or 1-butylpyridinium chloride (-Bupy-Cl-)) have been used to assemble modified screen printed electrodes (SPEs). The graphene oxide/ionic liquid dispersions have been morphologically and structurally characterized by the use of several techniques: X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared (FT-IR) spectroscopy, high-resolution-transmission electron microscopy (HR-TEM). The assembled modified SPEs have then been challenged with various compounds and compared to several electro-active targets. In all cases high peak currents were detected, as well as significant potential shifts, especially in the detection of catecholamines and NADH, compared with the bare SPE and the conventional electrodes, such as glassy carbon (GC) and highly oriented pyrolitic graphite (HOPG). This opens the way to the assembly of new types of sensors and biosensors. The enhanced performances observed are attributed to electrocatalytic effects related to the high electrode surface area, to oxygen-assisted electron transfer, as well as to the disordering effect of the ILs, this latter related to the favorable π-π interactions with the ILs and the GO plane.

Small angle scattering study of the structure of isotactic polypropylene-hydrogenated oligo(cyclopentadiene) blends☆

Abstract Blends of isotactic polypropylene ( i PP) and hydrogenated oligo cyclopentadiene (HOCP) have been studied by means of small angle X-ray scattering in the temperature range 70–160°C. The structure of blends containing less than 25% HOCP is very similar to the one of plain i PP, i.e. lamellae whose thickness increases by increasing the temperature. Blends containing more than 25% HOCP are characterized by two kinds of lamellae formed by layers of i PP and amorphous material rich in i PP and in HOCP, respectively. The crystallizable i PP present in both phases crystallizes from the melt, in analogy to what happens in HDPE/HOCP blends and in agreement with the values of the crystallinity referred to the crystallizable polymer, that is almost constant with composition for both blends.

Physicochemical characterization of metal hexacyanometallate–TiO2 composite materials

The paper describes the synthesis and characterization of novel TiO2–metal hexacyanometallates (MHCMs) composite materials. The starting material, TiO2, was modified by addition of cobalt-hexacyanoferrate (CoHCF) or iron-hexacyanocobaltate (FeHCC) at various concentrations. The resulting composites were characterized as follows: cyclic voltammetry (CV) followed the formation of TiO2–MHCM clusters, TEM micrographs studied their morphology, XAS and XPS data indicated that MHCM bonds to TiO2 through the nitrogen atom of its –CN group and modifies the environment of Ti compared to that of pure anatase. As expected, and confirmed by UV-Vis and XP-valence band data, the electronic properties of TiO2 were substantially modified: the edge in the composite materials shifted by about −2.0 eV relative to TiO2.

FT-IR and dielectric study of water/AOT liquid crystals

Abstract In order to explore the influence of microwave radiation on highly viscous microheterogeneous systems, the evolution of structural and dynamical properties of the water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT) liquid crystals as a function of the molar ratio R ( R =[water]/[AOT]) has been investigated by FT-IR spectroscopy and time domain reflectometry. The study emphasises how the progressive hydration of the surfactant head groups is mainly responsible for the structural and dynamical evolution of water/AOT liquid crystals. In particular, it has been found that the state of water at lower R values is strongly perturbed, bulk-like water appears only at R >23 and the water/AOT interface polarisation is controlled by the fast translational dynamics of sodium counterions and the slow orientational dynamics of the AOT ionic head groups.

Luminescence Properties of Neodymium-Doped Yttrium Aluminium Garnet Obtained by the Co-Precipitation Method Combined with the Mechanical Process

Nanopowders of yttrium aluminium garnet Y3Al5O12 (YAG) doped with neodymium ions were obtained by the co-precipitation method from the reaction of aluminium and yttrium nitrate and neodymium oxide with ammonia. After washing and drying the hydroxide precursors were calcined at 500, 700, 800 and 900 °C for 1 hour and at 1000 °C for 3 hours. This product was treated by ball milling in a zirconia vial for 0.5, 1.5 and 10 h in order to achieve smaller nanoparticles. The structure, microstructure, morphology and optical properties were investigated by means of diffractometric, microscopic and spectroscopic techniques. The course of the amorphous-to-crystalline transformation was complete after calcining the powder for 1 hour at 900 °C. In the sample calcined for 3 hours at 1000 °C, the mean size of crystallite microdomains was reduced from 600 Å to 300, 250 and 160 Å after 0.5, 1.5 and 10 h of mechanical treatment respectively. The treated product was found to be contaminated with ZrO2. This contamination, from the vial and hardened ZrO2 balls reaches ca. 30 wt % after 10 h of mechanical treatment but causes only a slight reduction of the neodymium luminescence life-time, thus maintaining significant applicative properties.