Phase formation in mixed TiO<Subscript>2</Subscript>-ZrO<Subscript>2</Subscript> oxides prepared by sol-gel method

Pure titania, zirconia, and mixed oxides (3–37 mol.% of ZrO₂) are prepared using the sol-gel method and calcined at different temperatures. The calcined samples are characterized by Raman spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption porosimetry. Measurements reveal a thermal stability of the titania anatase phase that slightly increases in the presence of 3–13 mol.% of zirconia. Practically, the titania anatase-rutile phase transformation is hindered during the temperature increase above 700°C. The mixed oxide with 37 mol.% of ZrO₂ treated at 550°C shows a new single amorphous phase with a surface area of the nanoparticles double with respect to the other crystalline samples and the formed srilankite structure (at 700°C). The anatase phase is not observed in the sample containing 37 mol.% of ZrO₂. The treatment at 700°C causes the formation of the srilankite (Ti_0.63Zr_0.37O_x) phase.     

Non-Porous versus Mesoporous Siliceous Materials for CO2 Capture

In this study, the adsorption properties of a Stöber silica-based material towards CO₂ were evaluated for the first time. The use of Stöber silica as support is interesting for real technological applications mainly due to economic factors. Furthermore, a direct comparison between the non porous Stöber sample with an ordered porous material (based on MCM-41 silica) allowed to evaluate the effect of the porosity on the CO₂ adsorption properties. In order to make silica materials reactive towards CO₂, they were functionalized by introducing amino groups via grafting of 3-[2-(2-aminoethyl)aminoethyl]aminopropyltrimethoxysilane. After a qualitative study of the CO₂ adsorption, the quantitative determination of CO₂ adsorption capacity at 35 °C revealed that the mesoporous material is more efficient compared to the Stöber-based one (adsorption capacity values of 0.49 and 0.58 mol/kg for Stöber-based and mesoporous samples). However, since the difference in the adsorption capacity is only about 15 % and the Stöber-based sample is considerably cheaper, the non-porous sample should be considered as a favourable adsorbent material for CO₂ capture applications.     

Validation of a new HPLC‐UV method for determination of the antibiotic linezolid in human plasma and in bronchoalveolar lavage

A rapid and selective HPLC‐UV method was developed for the quantification of linezolid (LNZ) in human plasma and bronchoalveolar lavage (BAL) at the concentrations associated with therapy. Plasma samples were extracted by solid‐phase extraction followed by evaporation to dryness and reconstitution in mobile phase solution. The chromatographic separation was carried out on a C₁₈ column with an isocratic mobile phase consisting of dihydrogen phosphate buffer 50 mm (pH 3.5) and acetonitrile (60:40 v/v). The detection was performed using a photodiode array. Under these conditions, a single chromatographic run could be completed within 12 min. The method was validated by estimating the precision and the accuracy for inter‐ and intra‐day analysis in the concentration range of 25–25600 ng/mL. The method was linear over the investigated range with all the correlation coefficients R > 0.999. The intra‐ and inter‐day precision was within 8.90% and the accuracy ranged from ?4.76 to +5.20%. This rapid and sensitive method was fully validated and could be applied to pharmacokinetic study for the determination of LNZ levels in human plasma and BAL samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Electronic energy transfer in a multiporphyrin-based molecular box.

The molecular box 1 comprises of two zinc-porphyrin metallacycles connected by two free-base 4'-trans-dipyridylporphyrins, axially coordinated to the zinc centers. The photophysics of 1 were studied in chloroform by emission and ultrafast absorption spectroscopy. In the molecular box, fast singlet energy transfer (main component, tau=32 ps) is observed to occur from the zinc-porphyrin metallacycles to the free-base chromophores. From wavelength-dependent spectrofluorimetric data, the efficiency of the energy-transfer (ET) process is estimated as 0.5. The lower-than-unity value is tentatively attributed to the possibility of a competing electron-transfer quenching pathway. Molecular box 1 can be considered to be a simple, self-assembling, six-chromophore antenna system. It has an inner cavity, 11.4 Angstrom wide, that could be used, in principle, to host a variety of guest molecules and obtain higher-order assemblies.     

Renormalization Group in the Uniqueness Region: Weak Gibbsianity and Convergence

We analyze the block averaging transformation applied to lattice gas models with short range interaction in the uniqueness region below the critical temperature. We prove weak Gibbsianity of the renormalized measure and convergence of the renormalized potential in a weak sense. Since we are arbitrarily close to the coexistence region we have a diverging characteristic length of the system: the correlation length or the critical length for metastability, or both. Thus, to perturbatively treat the problem we have to use a scale–adapted expansion. Moreover, such a model below the critical temperature resembles a disordered system in the presence of Griffiths' singularity. Then the cluster expansion that we use must be graded with its minimal scale length diverging when the coexistence line is approached. The authors acknowledge the support of Cofinanziamento MIUR.     

A numerical study of planar arrays of correlated spin islands

We analyze a system of interacting islands of XY spins on a triangular lattice. This model has been introduced a few years ago by Eley et al. [Nat. Phys. 8, 59 (2012)] to account for the phenomenology in experiments on tunable arrays of proximity coupled long superconductor-normal metal-superconductor junctions. The main features of the model are the separation of a local and a global interaction energy scale and the mesoscopic character of the spin islands. Upon lowering the temperature the model undergoes two crossovers corresponding to an increasing phase coherence on a single island and to the onset of global coherence across the array; the latter is a thermodynamical phase transition in the Ising universality class. The dependence of the second transition on the island edge-to-edge spacing is related to the proximity-effect of the coupling constant.     

Structural and photophysical characterization of multichromophoric pyridylporphyrin-rhenium(i) conjugates

Four porphyrin-Re(I) conjugates, in which a pyridylporphyrin chromophore is directly coordinated to the electron-acceptor fragment [ fac-Re(CO) 3(bipy)] (+), were prepared: the dimeric and pentameric compounds [ fac-Re(CO) 3(bipy)(4'MPyP)](CF 3SO 3) ( 1) (4'MPyP = 4'-monopyridylporphyrin) and [ fac-{Re(CO) 3(bipy)} 4(mu-4'TPyP)](CF 3SO 3) 4 ( 2) (4'TPyP = 4'-tetrapyridylporphyrin), and the corresponding compounds with 3' rather than 4' porphyrins, [ fac-Re(CO) 3(bipy)(3'MPyP)](CF 3SO 3) ( 3) and [ fac-{Re(CO) 3(bipy)} 4(mu-3'TPyP)](CF 3SO 3) 4 ( 4). These adducts proved to be very stable in solution and were also structurally characterized in the solid state by X-ray crystallography. A detailed photophysical study was performed on the zincated adducts of the conjugates 1- 3, labeled 5, 6, and 7, respectively. In all adducts the typical fluorescence of the zinc-porphyrin unit was reduced in intensity and lifetime by the presence of the peripheral rhenium-bipy fragment(s) (heavy-atom effect). For the dyads 5 and 7 the photoinduced charge transfer process from the zinc-porphyrin to the Re(I)-bipy unit is only slightly exoergonic. Ultrafast spectroscopy experiments showed no evidence for electron transfer quenching in the dyads as such, whereas the addition of pyridine (that binds axially to zinc and thus affects the porphyrin redox potential) led to a moderately efficient photoinduced electron transfer process. In perspective, an appropriate functionalization of the bipy ligand and/or of the porphyrin chromophore might improve the thermodynamics and, thus the efficiency, of the photoinduced electron transfer process.     

Structural and collisional relaxations in liquids and supercritical fluids

The dynamic structure factor S(Q,omega) of both associated (water and ammonia) and simple fluids (nitrogen and neon) has been determined by high-resolution inelastic x-ray scattering in the 2-14 nm(-1) momentum transfer range. A line-shape analysis with a generalized hydrodynamic model was used to study the involved relaxation process and to characterize its strength and time scale. We observe that in the liquid phase such a process is governed by rearrangements of intermolecular bonds, whereas in the supercritical region it assumes a collisional nature.     

Asymmetric dihydroxylation of drim-7-en-11-ol: synthesis of diastereomerically pure driman-7α,8α,11-triol and its elaboration into novel chlorinated norlabdanic compounds

The asymmetric dihydroxylation of drim-7-en-11-ol was studied in detail and diastereomerically pure driman-7α,8α,11- and driman-7β,8β,11-triols were prepared. Further elaboration of driman-7α,8α,11-triol afforded 14,15-bisnorlabd-7α,8α-isopropylidenedioxy-11,13-dione from which a novel chlorinated bisnorlabdanic compound (14,15-bisnorlabd-12-ene-12-chloro-8α,13-epoxy-7α-ol-11-one) and an unusual dichloro-derivative, 13,14,15,16-tetranorlabd-12-dichloro-7α-acetoxy-8α-ol-11-one, were obtained.     

Development of a reference solution for the pH of seawater

A method that uses a Harned cell to perform potentiometric pH measurements has been optimized and applied to an aqueous solution of simulated seawater that contains sodium perchlorate, sodium sulfate, sodium hydrogen carbonate and boric acid and has an ionic strength I of 0.57 mol kg⁻¹. The standard metrological approach developed for the measurement of pH in low ionic strength aqueous solutions was maintained, but a few modifications were necessary, and measurement procedures and calculations were modified ad hoc from those adopted in conventional protocols. When determining the standard potential of the cell, E°, NaClO₄ salt was added to a 0.01 mol/kg HCl solution to attain the same ionic strength as the test solution and to investigate possible specific effects related to the high levels and the nature of the background electrolyte. An appropriate value of γ _±HCl (0.737) was then selected from the literature, based on a realistic value for I. Finally, in order to convert the acidity function at zero chloride molality into pH, a suitable value of γ _Cl (0.929) was calculated. As a result, we obtained pH = 8.18 (T = 25 °C) with an associated expanded uncertainty U = 0.01 (coverage factor k = 2). The aim was to establish a sound basis for the pH measurement of seawater by identifying the critical points of the experimental and theoretical procedure, and to discuss further possible developments that would be useful for achieving a reference solution.