Antonio C. Bloise

Characterisation of PEO–Al2O3 composite polymer electrolytes

Abstract The behaviour of PEO 8 LiClO 4 with different quantities of α-Al 2 O 3 or γ-Al 2 O 3 was investigated using DSC, AC conductivity and 7 Li NMR experiments. DSC results showed that the presence of the filler does not change the glass transition temperature of the electrolyte but, on the other hand, modifies the quantity of its crystalline phase. From the AC impedance measurements, it was observed that the sample with the highest conductivity at room temperature is PEO 8 LiClO 4 5.3 wt.% α-Al 2 O 3 . The change in the quantity of crystalline phase cannot alone explain the conductivity data, and it is suggested that the space charge contribution in the interphase of the filler particles and the polymeric chains influences the behaviour of the samples. The 7 Li NMR results showed that line width narrowing begins at temperatures close to T g . From the hydrogen decoupling experiments it was possible to estimate the LiH average distances as 2.7 A. The LiLi distance was calculated as being between 2.6 and 3.5 A depending on the number of near neighbours lithium nuclei used in the model.

Nuclear magnetic resonance study of PEO-based composite polymer electrolytes

Abstract The effect of carbon black and ceramic (a-Al 2 O 3 and g-Al 2 O 3 ) particles on the cationic and polymer chain mobilityhave been investigated in poly(ethylene oxide)–lithium salt (LiClO 4 and LiBF 4 ) solid composite polymer electrolytesby using nuclear magnetic resonance (NMR) techniques. Proton ( 1 H) and lithium ( 7 Li) lineshapes and spin–latticerelaxation times were measured as a function of temperature. The 7 Li data indicates that the lineshape and relaxationis affected by the coupling of its quadrupolar moment to the surrounding electric field gradients. Activation energiesextracted from the 7 Li relaxation data are in the range 0.20–0.25 eV. Results show that the addition of a-Al 2 O 3 influenced both, the relative cation mobility and the polymer chain motion. Calculation shows that this result is inquantitative agreement with the conductivity data.

NMR and conductivity study of PEO-based composite polymer electrolytes

The influence of the space charge created by the presence of TiO2 nanoparticles on the lithium and polymer chain mobility have been investigated in solid composite polymer electrolytes (CPE), poly(ethylene oxide) (PEO) LiClO4, by using complex impedance spectroscopy and nuclear magnetic resonance (NMR). Special care was taken with the synthesis and the characterization of the TiO2 particles and with the composite preparation. The conductivity and NMR measurements were undertaken in composite samples nanoparticles having constant total surface area. Proton (1H) and lithium (7Li) lineshapes and spin-lattice relaxation times were measured as a function of temperature. Activation energies extracted from the 7Li relaxation data are in the range 0.20–0.22 eV. The NMR decoupling experiment suggests that the Li–Li interactions are stronger in the composites when compared with those of the ceramic free electrolytes.

Metabolic profile of dystrophic mdx mouse muscles analyzed with in vitro magnetic resonance spectroscopy (MRS)

Duchenne muscular dystrophy (DMD) is a recessive X-linked form of muscular dystrophy characterized by progressive and irreversible degeneration of the muscles. The mdx mouse is the classical animal model for DMD, showing similar molecular and protein defects. The mdx mouse, however, does not show significant muscle weakness, and the diaphragm muscle is significantly more degenerated than skeletal muscles. In this work, (1)H magnetic resonance spectroscopy (MRS) was used to study the metabolic profile of quadriceps and diaphragm muscles from mdx and control mice. Using principal components analysis (PCA), the animals were separated into groups according to age and lineages. The classification was compared to histopathological analysis. Among the 24 metabolites identified from the nuclear MR spectra, only 19 were used by the PCA program for classification purposes. These can be important key biomarkers associated with the progression of degeneration in mdx muscles and with natural aging in control mice. Glutamate, glutamine, succinate, isoleucine, acetate, alanine and glycerol were increased in mdx samples as compared to control mice, in contrast to carnosine, taurine, glycine, methionine and creatine that were decreased. These results suggest that MRS associated with pattern recognition analysis can be a reliable tool to assess the degree of pathological and metabolic alterations in the dystrophic tissue, thereby affording the possibility of evaluation of beneficial effects of putative therapies.

Characterization of organic matter in sediment cores of the Todos os Santos Bay, Bahia, Brazil, by elemental analysis and 13C NMR.

The impact of human activity on the sediments of Todos os Santos Bay in Brazil was evaluated by elemental analysis and 13C Nuclear Magnetic Resonance (13C NMR). This article reports a study of six sediment cores collected at different depths and regions of Todos os Santos Bay. The elemental profiles of cores collected on the eastern side of Frades Island suggest an abrupt change in the sedimentation regime. Autoregressive Integrated Moving Average (ARIMA) analysis corroborates this result. The range of depths of the cores corresponds to about 50 years ago, coinciding with the implantation of major onshore industrial projects in the region. Principal Component Analysis of the 13C NMR spectra clearly differentiates sediment samples closer to the Subaé estuary, which have high contents of terrestrial organic matter, from those closer to a local oil refinery. The results presented in this article illustrate several important aspects of environmental impact of human activity on this bay.

Production and characterization of fibroin hydrogel using waste silk fibers

The use of natural resources, especially processing wastes, as low cost and environmentally friendly alternative aiming high value-added applications is a subject of broad interest. Since the Brazilian silk production annually generates a large amount of waste during the silk fibers processing, this work explores the preparation and characterization of silk fibroin hydrogels using spinning waste silk fibers from textile processing and the processed ones. Hydrogels were obtained directly by dialyzing silk fibroin solutions against frequent changes of water until the gelation point and then lyophilized and characterized in terms of their morphology, crystallinity, thermal resistance and secondary structure. X-ray diffraction analysis revealed the presence of β-sheet conformation related to sol-gel transition. FT-IR spectra indicated the coexistence of random coil (silk I) and β-sheet (silk II) structures, with predominance of β-sheet conformation for hydrogels from processed silk fibers. From thermogravimetric analysis the presence of β-sheet secondary conformation was demonstrated by a degradation peak around 292 °C for both hydrogels. Freeze-dried hydrogels presented sheet or leaf like morphology and no significant change was observed among the hydrogels from waste silk fibers and processed ones. These characteristics suggest that silk fibroin hydrogels prepared from spinning waste silk fibers and obtained directly by dialysis can be potential candidates for biomaterials application, such as drug delivery systems and for wound dressings.

Metabolism under hypoxia in Tm1 murine melanoma cells is affected by the presence of galectin-3, a metabolomics approach

Metabolomics has proven an useful tool for systems biology. Here we have used a metabolomics approach to identify conditions in which de novo expression of an established tumor marker, galectin-3, would confer a potential selective advantage for melanoma growth and survival. A murine melanoma cell line (Tm1) that lacks galectin-3 was modified to express it or not (Tm1.G2 and Tm1.N3, respectively). These variant cell line were then exposed to conditions of controlled oxygen tensions and glucose levels. Metabolic profiling of intracellular metabolites of cells exposed to these conditions was obtained in steady state using high resolution 1H Magnetic Resonance Spectroscopy (1H-MRS) and multivariate statistical analysis. The Nuclear Magnetic Resonance (NMR) spectra contained a large number of absorption lines from which we were able to distinguish 20 metabolites, 3 fatty acids and some absorption lines and clusters were not identified. Principal Components Analysis (PCA) allowed for the discrimination of 2 experimental conditions in which expression of the tumor marker galectin-3 may play a significant role, namely exposure of cells to hypoxia under high glucose. Interestingly, under all other experimental conditions tested, the cellular system was quite robust. Our results suggest that the Metabolomics approach can be used to access information about changes in many metabolic pathways induced in tumorigenic cells and to allow the evaluation of their behavior in controlled environmental conditions or selective pressures.

Lithium dynamics in molybdenum disulfide intercalation compounds studied by nuclear magnetic resonance

Cluster architecture and lithium motion dynamics are investigated in nanocomposites formed by the intercalation of lithium and a dialkylamine (diethylamine, dibutylamine and dipentylamine) in molybdenum disulfide by means of 7Li Nuclear Magnetic Resonance (NMR) technique. The present contribution illustrates the potential of the NMR techniques in the study of both the short range atomic structure and the local dynamics of ions in these intercalation compounds. Structural information is gained through measurements of the various interactions (such as dipolar and quadrupolar) that affect the lineshapes of the NMR spectra, while ion dynamics information is gained through the study of the effects that ionic motion has on the nuclear relaxation times, which are modulated by these interactions. The formation of lithium clusters in these nanocomposites is suggested by the Li-Li dipolar interaction strength calculated from the 7Li NMR data. The lithium spin-lattice relaxation is mainly due to the interaction between the quadrupolar moment of the 7Li nuclei and the fluctuating electric field gradient at the site of the nucleus, produced by the surrounding charge distribution. The relaxation mechanism is consistent with a fast exchange motion of lithium ions between the coordination sites within the aggregates.

NMR Study of Lithium Dybutilamine Molybdenum Disulfide Nanocomposite

Measurements of 1 H and 7 Li Nuclear Magnetic Resonance (NMR) are reported for the nanocomposite formed by the intercalation of lithium and dibutylamine in molybdenum disulfide, Li 0.1 [(C 4 H 9 ) 2 NH] y MoS 2 . The temperature dependence NMR lineshapes and spin-lattice relaxation times ( T l ) measured exhibit the qualitative features associated with the lithium motions, namely the presence of a line narrowing at 230 K. The 1 H and the 7 Li longitudinal magnetization recovery was found to be non exponential. The T l values at each temperature was determined from the fit of a stretched exponential function. An activation energy for the lithium motion E a ≈0.18 eV was extracted from the 7 Li relaxation data. The dynamical parameters obtained from the 7 Li temperature dependence relaxation data indicate the mobility of the lithium in the nanocompositeis of the same order of magnitude as those obtained in other lithium intercalation compounds.