Deep eutectic solvents (DES) as green extraction media for antioxidants electrochemical quantification in extra-virgin olive oils.

A new electroanalytical method has been developed for the determination of polar antioxidant compounds in extra virgin olive oils. This method is based on the extraction of polar antioxidant compounds from extra-virgin olive oils by means of a deep eutectic solvent and their determination by a modified screen-printed electrode platform. The platform sensitivity was increased by modifying the working electrode with MWCNT and TiO2 nanoparticles as modifiers and Nafion as a binder. The platform showed very good sensitivity in detecting polar antioxidant compounds in extra-virgin olive oils in a fairly wide range of concentrations. The measurements were performed by using square wave voltammetry. The extraction was performed without using organic solvents, making the method environmentally friendly. The proposed method has been compared with a common spectrophotometric one, the results appeared in good agreement. The method is sufficiently easy and quick to be used for screening analyses of polar antioxidant compounds in extra-virgin olive oils on the field.

Biologically friendly room temperature ionic liquids and nanomaterials for the development of innovative enzymatic biosensors: Part II.

A newly modified electrode based on glassy carbon (GC) has been prepared and characterized electrochemically for application in electroanalytical chemistry. In particular, a GC screen-printed electrode (SPE) has been modified with nanostructures, namely multi-walled carbon nanotubes (MWCNTs), and TiO2 nanoparticles, and combined with a new generation of eco-friendly room-temperature ionic liquids (RTILs). The green RTILs here used are suitable for the immobilization of enzymes on the electrode surface and, additionally, facilitate the kinetics of electron transfer due to their intrinsic electrical conductivity. Upon evaluation of these newly modified electrodes we found an improvement in terms of electrochemically active area (Aea) with respect to the electrodes we previously reported. The modified SPEs were then used as substrates for the construction of two enzymatic biosensors for analytical applications: the first is an enzymatic biosensor based on alcohol dehydrogenase (ADH) for the analysis of ethyl alcohol; the second biosensor is based on lipase enzyme and has been tested for the analysis and the classification of Extra Virgin Olive Oil (EVOO). The performances of the here projected sensors appear comparable with biosensors having similar finalities. It is here envisaged that such a kind of electrodes could represent the starting tool for the construction and the definition of new portable devices for screening and field analyses.

Structure and dynamics of propylammonium nitrate-acetonitrile mixtures: An intricate multi-scale system probed with experimental and theoretical techniques.

In this article, we report the study of structural and dynamical properties for a series of acetonitrile/propylammonium nitrate mixtures as a function of their composition. These systems display an unusual increase in intensity in their X-ray diffraction patterns in the low-q regime, and their 1H-NMR diffusion-ordered NMR spectroscopy (DOSY) spectra display unusual diffusivities. However, the magnitude of both phenomena for mixtures of propylammonium nitrate is smaller than those observed for ethylammonium nitrate mixtures with the same cosolvent, suggesting that the cation alkyl tail plays an important role in these observations. The experimental X-ray scattering data are compared with the results of molecular dynamics simulations, including both ab initio studies used to interpret short-range interactions and classical simulations to describe longer range interactions. The higher level calculations highlight the presence of a strong hydrogen bond network within the ionic liquid, only slightly perturbed even at high acetonitrile concentration. These strong interactions lead to the symmetry breaking of the NO3- vibrations, with a splitting of about 88 cm-1 in the ν3 antisymmetric stretch. The classical force field simulations use a greater number of ion pairs, but are not capable of fully describing the longest range interactions, although they do successfully account for the observed concentration trend, and the analysis of the models confirms the nano-inhomogeneity of these kinds of samples.

Overview of the main methods used to combine proteins with nanosystems: absorption, bioconjugation, and encapsulation.

The latest development of protein engineering allows the production of proteins having desired properties and large potential markets, but the clinical advances of therapeutical proteins are still limited by their fragility. Nanotechnology could provide optimal vectors able to protect from degradation therapeutical biomolecules such as proteins, enzymes or specific polypeptides. On the other hand, some proteins can be also used as active ligands to help nanoparticles loaded with chemotherapeutic or other drugs to reach particular sites in the body. The aim of this review is to provide an overall picture of the general aspects of the most successful approaches used to combine proteins with nanosystems. This combination is mainly achieved by absorption, bioconjugation and encapsulation. Interactions of nanoparticles with biomolecules and caveats related to protein denaturation are also pointed out. A clear understanding of nanoparticle-protein interactions could make possible the design of precise and versatile hybrid nanosystems. This could further allow control of their pharmacokinetics as well as activity, and safety.

Hydration of diazoles in water solution: pyrazole. A theoretical and X-ray diffraction study.

The local structure of the hydration of pyrazole has been analysed through static and dynamical microsolvation models described by quantum mechanical methods. Then, a reliable classical force field of pyrazole has been obtained on the basis of the quantum mechanical results and the dynamical properties of aqueous pyrazole solutions have been studied by molecular dynamics simulations. Finally, the structure of pyrazole-water solutions at different concentrations has been investigated by energy dispersive X-ray diffraction and experimental results have been compared to calculations. This comparison provides both a tool for interpretation of experiments and a way to validate the computational protocol.

Overcoming the inadequacy of X-ray powder diffraction in reliable hydrogen location with the aid of first principles calculations: crystal structure determination of orotaldehyde monohydrate.

First principle calculations of periodic crystal structure were successfully combined with powder X-ray diffraction measures to determine the structure of orotaldehyde monohydrate. This approach was particularly helpful to overcome the inadequacy of powder X-ray diffraction to reliably locate the hydrogen atoms of the intermolecular bond network of the crystal molecules. Density functional calculations were accomplished for the free molecule and its cyclic dimers showing that the most stable centrosymmetric dimer is the building block of the molecular crystal.

Supramolecular organization of toluidine blue dye in solid amorphous phases.

Toluidine blue (TB) dye molecules are intensively utilized for large-area photophysics applications such as carcinoma detection, photoinactivation of bacteria, biosensors, and photovoltaic cells. Understanding the nature of the TB aggregation state becomes an essential point of the research process in order to know the structure-function relationship and to foresee technological applications of this class of metachromatic-dye molecules. However, no structural information on toluidine blue is available in the literature, maybe because of the poor crystalline character of the aggregate. Here, we present the first structural determination of TB organic molecules using the energy dispersive X-ray diffraction technique. The investigation highlights dimeric arrangements of stacked molecules in antiparallel fashion, forming a superstructure of two dimers in a transverse arrangement. The behavior of the TB higher aggregates indicates that these dye molecules, in spite of repulsion due to similar charge (cationic dyes), undergo self-aggregation to form helical conformations.

Physicochemical characterization of ultrasmall superparamagnetic iron oxide particles (USPIO) for biomedical application as MRI contrast agents.

Ultrasmall superparamagnetic iron oxide (USPIO) particles are maghemite or magnetite nanoparticles currently used as contrast agent in magnetic resonance imaging. The coatings surrounding the USPIO inorganic core play a major role in both the in vitro stability and, over all, USPIO's in vivo fate. Different physicochemical properties such as final size, surface charge and coating density are key factors in this respect. Up to now no precise structure--activity relationship has been described to predict entirely the USPIOs stability, as well as their pharmacokinetics and their safety. This review is focused on both the classical and the latest available techniques allowing a better insight in the magnetic core structure and the organic surface of these particles. Concurrently, this work clearly shows the difficulty to obtain a complete physicochemical characterization of USPIOs particles owing to their small dimensions, reaching the analytical resolution limits of many commercial instruments. An extended characterization is therefore necessary to improve the understanding of the properties of USPIOs when dispersed in an aqueous environment and to set the specifications and limits for their conception.

Structural characterization of ultrasmall superparamagnetic iron oxide (USPIO) particles in aqueous suspension by energy dispersive X-ray diffraction (EDXD).

Ultrasmall superparamagnetic iron oxide (USPIO) particles were structurally characterized in situ in an aqueous dilute suspension by energy dispersive X-ray diffraction (EDXD) and ex situ as powders obtained by lyophilization of the suspension by angular dispersive X-ray diffraction (ADXD) at 20 degrees C. Structural parameters obtained by the Rietveld method on ADXD data were used as starting parameters for modeling the structure of the particles in suspension. Although each particle is a single crystal, as evidenced by conventional X-ray diffraction, our results indicate that the structural order, specific to a crystal, does not extend to the entire volume of the particle. In fact, each individual particle, averagely, has a crystalline structural extension ca. 4.0 nm smaller than the apparent dimensions obtained by both ADXD and TEM (ca. 8.0 nm).

Structural analysis of the solid amorphous binuclear complexes of iron(III) and aluminum(III) with chromium(III)-DTPA chelator using energy dispersive X-ray diffraction.

This paper is concerned with the structural data obtained for two amorphous binuclear complexes of iron(III) and aluminum(III) with chromium(III)-diethylentriaminepentaacetic acid (chromium(III)-DTPA, CrL(2)(-)) using the energy-dispersive X-ray diffraction technique. Fe(OH)CrL(H(2)O)(6) and Al(OH)CrL(H(2)O)(6) are binuclear complexes, the metals ions being bridged via oxygen atoms. The metal ions are all octahedrally coordinated.

Preparation and structural characterization of polymer-supported methylrhenium trioxide systems as efficient and selective catalysts for the epoxidation of olefins.

Novel heterogeneous compounds of methylrhenium trioxide (MTO) were prepared with poly(4-vinylpyridine) and polystyrene as polymeric supports. The wide-angle X-ray diffraction (WAXS.) analysis, performed by the application of the difference method, showed, in a representative case of the poly(4-vinylpyridine)/MTO derivatives, a slightly distorted octahedral conformation on the metal's primary coordination sphere. The Re-O and Re-C bond distances were not influenced by the polymeric nature of the ligand, while the Re-N bond distance was abnormally shorter than those previously observed for homogeneous MTO/L(n) complexes, showing a strong coordination of the rhenium atom to the support. A set of scanning electron microscopy (SEM) photographs showing the morphology of the surface of particles of poly(4-vinylpyridine)/MTO and polystyrene/MTO systems are reported. The reticulation grade of the polymer was a crucial factor for the morphology of the particles surface. Poly(4-vinylpyridine) 2% cross-linked systems were characterized by particles with very irregular shape and surface. Poly(4-vinylpyridine) 25% cross-linked systems showed particles with regular spherical shape, which morphology was similar to microcapsules obtained with polystyrene. All novel MTO compounds were efficient and selective heterogeneous catalysts for the epoxidation of olefins using environmentally friendly H2O2 as oxygen atom donor. The catalyst activity was maintained for at least five recycling experiments.

Dimeric Osmium Phthalocyanine Organized in Discrete Columnarly Stacked Assemblies: Structure, Magnetism, and Electrical Conductivity Properties.

Solid pure osmium phthalocyanine, as obtained from its adduct [PcOs(py)(2)], is an air-stable solid amorphous material. Its structure has been examined by the wide-angle X-ray scattering (WAXS) technique. Experimental data are best fitted by assuming the molecule to consist of a dimeric unit, (PcOs)(2), held together by a direct metal-metal linkage. The short Os-Os distance (2.38(1) Å) is consistent with the presence of a double bond between the two Os(II) atoms. Each Pc skeleton has a domed conformation with displacement of the respective Os atom from the plane of the four coordinating nitrogen atoms (0.40 Å) toward the other Os atom. The solid-state structure consists of disordered couples of parallel chains of (PcOs)(2). On average, six dimeric units are aligned along the stacking direction within each chain. The relative orientation of the two intradimer Pc units is 30 degrees, eclipsing occurring for the interdimer adjacent Pc units along the chain. Magnetic susceptibility measurements in the temperature range 5-300 K indicate a strong spin-spin coupling for the two metal centers in the dimer and suggest an electronic energy level sequence sigma(2)pi(4)delta(2)delta(2)pi(2) and a nonmagnetic ground state for the complex. Room-temperature electrical conductivity measurements show a sigma(RT) value of 1 x 10(-)(5) Omega(-)(1) cm(-)(1).