Surface-enhanced Raman scattering on silver nanostructured films prepared by spray-deposition

Silver nanostructured films were directly prepared by spray deposition of preformed polyol-based Ag-PVP nanoparticles. These homogeneous films of high optical quality were tested as SERS-active substrates. Laser excitation at 514.5 nm within the red part of the plasmon band leads to intense and reproducible SERS spectra of acridine, used as the probe molecule. From SERS measurements at different pH values, it was possible to determine the apparent pK(a) of acridine and to obtain specific surface properties of the film. Finally, these SERS titrations along with enhancement factor estimates allowed us to further depict the nature of the films.     

Magnetostructural Correlations in Tetrairon(III) Single‐Molecule Magnets

Tunable single‐molecule magnets : The spin‐level landscape in a series of Fe^III₄ single‐molecule magnets with propeller‐like structure was analyzed by means of high‐frequency EPR spectroscopy. The zero‐field splitting parameter D of the ground S=5 spin state correlates strongly with the pitch of the propeller γ (see picture), and thus provides a simple link between molecular structure and magnetic behavior.

     

Multivariate optimization by exploratory analysis applied to the determination of microelements in fruit juice by inductively coupled plasma optical emission spectrometry

A method for the direct determination (without sample pre-digestion) of microelements in fruit juice by inductively coupled plasma optical emission spectrometry has been developed. The method has been optimized by a 2³ factorial design, which evaluated the plasma conditions (nebulization gas flow rate, applied power, and sample flow rate). A 1:1 diluted juice sample with 2% HNO₃ (Tetra Packed, peach flavor) and spiked with 0.5 mg L^− 1 of Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Sn, and Zn was employed in the optimization. The results of the factorial design were evaluated by exploratory analysis (Hierarchical Cluster Analysis, HCA, and Principal Component Analysis, PCA) to determine the optimum analytical conditions for all elements. Central point condition differentiation (0.75 L min^− 1, 1.3 kW, and 1.25 mL min^− 1) was observed for both methods, Principal Component Analysis and Hierarchical Cluster Analysis, with higher analytical signal values, suggesting that these are the optimal analytical conditions. F and t-student tests were used to compare the slopes of the calibration curves for aqueous and matrix-matched standards. No significant differences were observed at 95% confidence level. The correlation coefficient was higher than 0.99 for all the elements evaluated. The limits of quantification were: Al 253, Cu 3.6, Fe 84, Mn 0.4, Zn 71, Ni 67, Cd 69, Pb 129, Sn 206, Cr 79, Co 24, and Ba 2.1 µg L^− 1. The spiking experiments with fruit juice samples resulted in recoveries between 80 and 120%, except for Co and Sn. Al, Cd, Pb, Sn and Cr could not be quantified in any of the samples investigated. The method was applied to the determination of several elements in fruit juice samples commercialized in Brazil.     

A novel use of the recyclable polymer-supported IBX: an efficient chemoselective and regioselective oxidation of phenolic compounds. The case of hydroxytyrosol derivatives.

A useful and novel application of polymer-supported IBX for the chemoselective and regioselective oxidation of phenolic compounds has been described. Hydroxytyrosol and carboxymethylated hydroxytyrosol have been prepared in good conversions and yields under green chemistry conditions in the presence of dimethyl carbonate as the solvent. Polymer-supported reagent has been recovered by simple filtration, regenerated and reused for more cycles of oxidation reactions without loss of efficiency.     

Surface functionalization with phosphazene substrates—part VII. Silicon‐based materials functionalized with hexachlorocyclophosphazene

This paper investigates by means of XPS analysis the surface functionalization of soda‐lime and fused quartz glass substrates with hexachlorocyclophosphazene (HCCP), obtained by simple immersion in solutions of phosphazene in anhydrous solvents. Several experimental parameters like reaction solvent, temperature and treatment duration were studied, together with the influence of physisorbed water on the surface of the substrates. Phosphazene‐derived deposits resistant to tetrahydrofuran (THF) washing and vacuum drying were obtained. They presented P:N:Cl stoichiometric ratios close to 1:1:1 when the reaction and the final drying of the samples were performed at room temperature; use of higher temperatures resulted in lower nitrogen and chlorine content. The chemical nature of the films was studied by XPS peaks deconvolution which enabled us to propose a possible, temperature‐enhanced hydrolytical degradation mechanism. Copyright © 2008 John Wiley & Sons, Ltd.     

In vitro enhancement of anticancer activity of paclitaxel by a Cremophor free cyclodextrin-based nanosponge formulation

A severe limitation for cancer therapy is the poor water solubility of many important therapeutic anticancer drugs. The development of novel delivery systems is therefore currently ongoing. We propose the use of β-cyclodextrin based nanosponges to deliver paclitaxel as an alternative to classical formulation in Cremophor EL. They are solid nanoparticles with mean diameter lower than 500?nm and spherical shape. Nanosponges show a safe profile being non-hemolytic and non cytotoxic. Nanosponges dissolved and encapsulated paclitaxel up to 2?mg/ml. The paclitaxel-loaded nanosponges formed a water stable colloidal system avoiding the recrystallization of paclitaxel. The in vitro release studies showed an almost complete release in 2?h without initial burst effect. Our study demonstrates that delivery of paclitaxel via nanosponges increased the amount of paclitaxel entering cancer cells and lowers paclitaxel IC50, therefore enhancing its pharmacological effect. β-Cyclodextrin based nanosponges can therefore be considered an alternative system to solubilize and deliver the paclitaxel.     

Investigation of photocatalytic activity of metal-doped TiO2 nanoparticles prepared by Pechini method

M-doped TiO₂ (M = Ag²⁺, Al³⁺, Ce⁴⁺, Nb⁵⁺) with different dopant contents have been prepared by the Pechini method using titanium IV isopropoxide as precursor. The effect of doping concentration on the photocatalytic activity for methyl orange (MO) photodegradation was investigated using UV radiation. The photocatalysts were characterized by surface area, X-ray diffraction and UV–Vis diffuse reflectance spectroscopy. An increase in the photoactivity of TiO₂ nanoparticles was confirmed by MO photocatalytic degradation experiments, when the transition metal ions were incorporated into the semiconductor crystalline lattice, which could be attributed to an increase in the charge separation and reduction of e^?/h⁺ recombination as a function of the substitutional defect generated at very low levels.     

CO2 capture by metal-organic frameworks with van der Waals density functionals

We use density functional theory calculations with van der Waals corrections to study the role of dispersive interactions on the structure and binding of CO(2) within two distinct metal-organic frameworks (MOFs): Mg-MOF74 and Ca-BTT. For both classes of MOFs, we report calculations with standard gradient-corrected (PBE) and five van der Waals density functionals (vdW-DFs), also comparing with semiempirical pairwise corrections. The vdW-DFs explored here yield a large spread in CO(2)-MOF binding energies, about 50% (around 20 kJ/mol), depending on the choice of exchange functional, which is significantly larger than our computed zero-point energies and thermal contributions (around 5 kJ/mol). However, two specific vdW-DFs result in excellent agreement with experiments within a few kilojoules per mole, at a reduced computational cost compared to quantum chemistry or many-body approaches. For Mg-MOF74, PBE underestimates adsorption enthalpies by about 50%, but enthalpies computed with vdW-DF, PBE+D2, and vdW-DF2 (40.5, 38.5, and 37.4 kJ/mol, respectively) compare extremely well with the experimental value of 40 kJ/mol. vdW-DF and vdW-DF2 CO(2)-MOF bond lengths are in the best agreement with experiments, while vdW-C09(x) results in the best agreement with lattice parameters. On the basis of the similar behavior of the reduced density gradients around CO(2) for the two MOFs studied, comparable results can be expected for CO(2) adsorption in BTT-type MOFs. Our work demonstrates for this broad class of molecular adsorbate-periodic MOF systems that parameter-free and computationally efficient vdW-DF and vdW-DF2 approaches can predict adsorption enthalpies with chemical accuracy.     

A carbon-rich ruthenium decorated dysprosium single molecule magnet

The association of a carbon-rich ruthenium complex with an anisotropic dysprosium ion leads to a unique complex showing SMM behaviour with multiple relaxation processes.