Solid State NMR Study of the Mixing Degree Between Ginkgo Biloba Extract and a Soy-Lecithin-Phosphatidylserine in a Composite Prepared by the Phytosome® Method

Leaves extract of Ginkgo biloba, known in China since the most ancient times, has been widely used in the area of senile dementia thanks to its improving effects on cognitive function. A promising formulation of this botanical ingredient consists in a Ginkgo biloba-soy-lecithin-phosphatidylserine association obtained by the Phytosome® process. The precise assess- ment of the mixing degree between Ginkgo biloba and soy-lecithin-phosphatidylserine in this formulation is an important piece of information for understanding the reasons of its final performances. To this aim in the present study we carried out for the first time a Solid State Nuclear Magnetic Resonance investigation on Ginkgo biloba-soy-lecithin-phosphatidylserine association, on its constituents and on a mechanical mixture. The analysis of different observables highlighted a very intimate mixing (domains of single components not larger than 60 nm) of Ginkgo biloba and soy-lecithin-phosphatidylserine in their association obtained by Phytosome® process, together with a slight modification of their molecular dynamics, not observed in the case of the mechanical mixture

Thermochromic polyethylene films doped with perylene chromophores: experimental evidence and methods for characterization of their phase behaviour

We report on a thermochromic system suitable for sensing temperature changes in the 30-70 degrees C regime based on linear low density polyethylene (LLDPE) films doped with N,N'-bis-(1'-phenylethyl)-perylene-3,4,9,10-tetracarboxydiimide (PE-Pery), a fluorescent aggregachromic dye. At low PE-Pery concentration (0.01-0.02 wt%), the dye monomers were well dispersed in the polymer matrix showing their maximum fluorescence intensity at 525 nm. As the dye content was increased, monomers emission quenched whereas dye aggregates prevailed above 0.05 wt% as well as their red fluorescence band at 620-680 nm. Upon heating from 30 to 70 degrees C, all films displayed a thermochromic response, more evident for the less concentrated samples (<0.05 wt%) in which the emission of the dye as a monomer continuously increased with increasing temperature. This phenomenon promoted effective color changes from a dull red-violet at 30 degrees C to a bright yellow-green at 70 degrees C. Combined DSC and variable-temperature Solid State NMR (SSNMR) measurements addressed the thermochromic behavior to the increased amount of the available amorphous phase and to the increased mobility of both the interphase and amorphous components with temperature, which favored PE-Pery dispersion and diffusion, thus recovering their fluorescence. Overall, the present results support the use of PE-Pery-enriched LLDPE films as a chromogenic material suitable for the detection of temperature changes close to the physiological regime

Epoxy resin doped with Coumarin 6: Example of accessible luminescent collectors

We report on the preparation of luminescent collectors based on epoxy resins containing Coumarin 6 as fluorescent dye. Fluorescent epoxy slabs were obtained by carefully mixing from 60 to 150 ppm of the fluorophore with bisphenol A diglycidyl ether and 4,4′-methylenebis(2-methylcyclohexylamine) as curing agent. Spectroscopic (FT-IR, solid-state NMR, Raman) investigations and calorimetric analysis evidence the success of the preparation procedure in terms of slab homogeneity, fluorophore dispersibility and its role in promoting the crosslinking extent. The concentrating ability and the derived optical efficiencies of the epoxy-based collectors are determined with a properly designed set-up and result greater (∼10%) than that of poly(methyl methacrylate) concentrators with the same fluorophore and geometry. Optical efficiencies as high as 7.4% are obtained and enable the potential use of epoxy resins as bulk thermosetting materials for solar collectors

Solid-State Nuclear Magnetic Resonance of Triple-Cation Mixed-Halide Perovskites

Mixed-cation lead mixed-halide perovskites are the best candidates for perovskite-based photovoltaics, thanks to their higher efficiency and stability compared to the single-cation single-halide parent compounds. TripleMix (Cs0.05MA0.14FA0.81PbI2.55Br0.45 with FA = formamidinium and MA = methylammonium) is one of the most efficient and stable mixed perovskites for single-junction solar cells. The microscopic reasons why triplecation perovskites perform so well are still under debate. In this work, we investigated the structure and dynamics of TripleMix by exploiting multinuclear solid-state nuclear magnetic resonance (SSNMR), which can provide this information at a level of detail not accessible by other techniques. 133Cs, 13C, 1 H, and 207Pb SSNMR spectra confirmed the inclusion of all ions in the perovskite, without phase segregation. Complementary measurements showed a peculiar longitudinal relaxation behavior for the 1 H and 207Pb nuclei in TripleMix with respect to single-cation single-halide perovskites, suggesting slower dynamics of both organic cations and halide anions, possibly related to the high photovoltaic performances

Polymer-based black phosphorus (bP) hybrid materials by in situ radical polymerization: an effective tool to exfoliate bP and stabilize bP nanoflakes

Black phosphorus (bP) has been recently investigated for next generation nanoelectronic multifunctional devices. However, the intrinsic instability of exfoliated bP (the bP nanoflakes) towards both moisture and air has so far overshadowed its practical implementation. In order to contribute to fill this gap, we report here the preparation of new hybrid polymer-based materials where bP nanoflakes exhibit a significantly improved stability. The new materials have been prepared by different synthetic paths including: i) the mixing of conventionally liquid-phase exfoliated bP (in DMSO) with PMMA solution; ii) the direct exfoliation of bP in a polymeric solution; iii) the in situ radical polymerization after exfoliating bP in the liquid monomer (methyl methacrylate, MMA). This last methodology concerns the preparation of stable suspensions of bPn-MMA by sonication-assisted liquid phase exfoliation (LPE) of bP in the presence of MMA followed by radical polymerization. The hybrids characteristics have been compared in order to evaluate the bP dispersion and the effectiveness of the bPn interfacial interactions with polymer chains aimed at their long-term environmental stabilization. The passivation of bPn results particularly effective when the hybrid material is prepared by in situ polymerization. By using this synthetic methodology, the nanoflakes, even if with a gradient of dispersion (size of aggregates), preserve their chemical structure from oxidation (as proved by both Raman and 31P-Solid State NMR studies) and are particularly stable to air and UV light exposure

Comparison of the dielectric and NMR results for liquid crystals : dynamic aspects

Critical analysis of the results of studies of molecular rotational dynamics in liquid crystalline substances with the aid of the dielectric spectroscopy (DS) and nuclear magnetic resonance (NMR) is given. Both methods are known to be sensitive to different aspects of molecular rotations: the polarization vector and the relaxation time (DS) in the case of DS, a tensor describing a nuclear interaction and the correlation time (NMR) for NMR method. Furthermore, both methods provide correlation functions with different rank values. A common basis for the comparison between (DS) and (NMR) is postulated. Several examples of the temperature dependence of the correlation times coming from the two spectroscopic methods are presented. Qualitative agreements of the correlation times were achieved in most cases