Synthesis and characterization of PMMA/silylated MMTs

Commercially available Sodium clay (Dellite HPS) and organo-clay (Dellite 72T) are modified via a silylation reaction. These silylated clays are characterized by IR, XRD, thermogravimetric analyses, and their equilibrium contact angles are measured. They are used to prepare nanocomposites at different loading percentage (1, 3, 5% wt) by in situ intercalative polymerization of Methyl methacrylate and morphology and thermal properties of nanocomposites are examined. SEM images of nanocomposites fractured surface show the absence of clays aggregates, confirming a good dispersion and distribution of montmorillonites in the polymer matrix. The effects of modified clays on the thermal properties of nanocomposites are analyzed by differential scanning calorimetry and thermogravimetric analyses showing an increase of glass and decomposition temperatures of all nanocomposites respect to homopolymer ones. The best results are obtained in the presence of silylated montmorillonites, clearly the organosilane improves the compatibility between polymer matrix and clay and as effect the properties of nanocomposites.     

Instabilities in free diffusion boundaries of NaCl-sucrose-H2O solution at 25°C

The four diffusion coefficients for the system sucrose (0.097M)-NaCl-(0.291M)-water at 25°C have been measured by the Gouy interferometric technique. The cross terms D₁₂ and D₂₁ are small However, if sucrose or NaCl are chosen as component 3 instead of water, one of the cross terms becomes very large. Several runs were used to test the McDougall analysis of gravitational instability in diffusion boundaries for three component systems. Growth of convective motions at the center and at the edges of the boundary have been observed that confirm the McDougall model.     

Discovery of a new series of jatrophane and lathyrane diterpenes as potent and specific P-glycoprotein modulators

A new series of diterpenes, the jatrophanes euphoscopin M (1), euphoscopin N (2) and euphornin L (3), and the lathyrane euphohelioscopin C (7) were isolated from plants of Euphorbia helioscopia L., together with four other known analogues, euphoscopin C (4), euphornin (5), epieuphoscopin B (6) and euphohelioscopin A (8). The new compound stereostructures were elucidated by NMR analysis and computational data. The resulting isolated diterpenes were found to be potent inhibitors of P-glycoprotein (ABCB1), while showing an absence of significant activity against BCRP (ABCG2), despite the high substrate overlapping of these transporters, thus including them in the third-generation class of specific multidrug transporter modulators.     

Metal-mediated self-assembly of tetrapyridyl porphyrins by Na+ ions

In the presence of the sodium salt of a bulky anion, which allows the solubility of Na(+) in low polarity solvents, various tetra(4-pyridyl)porphyrin derivatives can spontaneously self-assemble from CH(2)Cl(2) into supramolecular nanostructures exhibiting a long-range order, through the coordination of Na(+) ions by the pyridyl moieties at the macrocycle periphery.     

Current fluctuations in polystyrene nano-compounds

The current fluctuations in a polystyrene matrix (PS) doped by gold nanoparticles (Au-NPs) and small conjugated molecules of 8-hydroxyquinoline (8HQ) have been characterized. The electrical properties of the PS composite allow using it as a responsive layer in non-volatile memory devices due to its switching capability between two well separated conducting states. The analysis of current fluctuations at fixed bias voltages showed the presence of two states in charge carrier transport regardless of the operating conducting state of the device. Moreover, noise spectra have been investigated in the low frequency region, allowing the estimation of charge relaxation times between current levels in the two memory states. The presence of these slow and large fluctuations can seriously affect the final electrical performances of this class of nanostructured memories.     

Diffusion of polyols in aqueous solution

The diffusion coefficients of aqueous solutions of the polyols CH₂OH-(CHOH)₄-CH₂OH (dulcitol, sorbitol, and myo-inositol) have been determinated using the Gouy interferometric method. Viscosity and density measurements have been carried out at the same temperature and concentration range for these and for mannitol. The concentration dependence of the diffusion coefficients are discussed in terms of solute-solute interactions with the help of thermodynamic literature data. Among the studied polyols, only dulcitol and myo-inositol exhibit a strong evidence for solute-solute interaction, whereas the other shows a preferential interaction with the solvent.     

First synthesis of 2,6-diazabicyclo[3.2.0]heptane derivatives

The first synthesis of 6-phenyl-2,6-diazabicyclo[3.2.0]heptane 1 and its orthogonally protected precursor 2 is herein reported. Our strategy enables to chemically address the two nitrogen atoms of 2,6-diazabicyclo[3.2.0]heptane core individually and selectively, thus allowing rapid access to several subsets of widely substituted fused azetidines.     

Rapid Access to 1-Benzyl 2-Substituted Piperazines: Application to the Synthesis of 1-Benzyl-2-difluoromethyl-Piperazine

A rapid and efficient synthesis of 1-benzyl-2-difluoromethyl-piperazine is herein described. The new pathway has the advantage of avoiding orthogonal protection at the two piperazine nitrogen atoms; therefore it is suitable for access to several 1-benzyl 2-substituted piperazines starting from the simple commercially available N,N′-dibenzylethylendiamine.     

Hybrid polymer-CdS solar cell active layers formed by in situ growth of CdS nanoparticles

The integration of semiconductor nanoparticles (NPs) into a polymeric matrix has the potential to enhance the performance of polymer-based solar cells taking advantage of the physical properties of NPs and polymers. We synthesize a new class of CdS-NPs-based active layer employing a low-cost and low temperature route compatible with large-scale device manufacturing. Our approach is based on the controlled in situ thermal decomposition of a cadmium thiolate precursor in poly(3-hexylthiophene) (P3HT). The casted P3HT:precursor solid foils were heated up from 200 to 300 °C to allow the precursor decomposition and the CdS-NP formation within the polymer matrix. The CdS-NP growth was controlled by varying the annealing temperature. The polymer:precursor weight ratio was also varied to investigate the effects of increasing the NP volume fraction on the solar cell performances. The optical properties were studied by using UV–Vis absorption and photoluminescence (PL) spectroscopy at room temperature. To investigate the photocurrent response of P3HT:CdS nanocomposites, ITO/P3HT:CdS/Al solar cell devices were realized. We measured the external quantum efficiency (EQE) as a function of the wavelength. The photovoltaic response of the devices containing CdS-NPs showed a variation compared with the devices with P3HT only. By changing the annealing temperature the EQE is enhanced in the 400–600 nm spectral region. By increasing the NPs volume fraction remarkable changes in the EQE spectra were observed. The data are discussed also in relation to morphological features of the interfaces studied by Focused Ion Beam technique.