Síntese de polímeros condutores em matrizes sólidas hospedeiras

This review discusses the methods used to prepare conductive polymers in confined environments. This spatial restriction causes formation of defect-free polymer chains in the interlayer as porous cavities of inorganic hosts. The properties of the different composites obtained are a synergist combination of the characteristics of the inorganic host and the polymer. This opens new perspectives for the preparation of these materials and widens its potential applications.

Morphological study of Sr2CeO4 blue phosphor with fine particles

Morphological and spectroscopic studies of Sr2CeO4 blue phosphor in the form of fine particles prepared from a powdered multi-component precursor, via a combustion method, are reported. Samples were also prepared through a solid-state reaction and from a polymeric precursor for comparison. Citric acid or glycine as fuels in the combustion method lead to a mixture which is heated at 950 ºC for 4 h, resulting in spheroidal particles with a diameter between 250-550 nm. Samples from the polymeric precursor result in spheroidal particles (350-550 nm) and from the solid-state reaction in irregular particles (~ 5 mum). Therefore, the combustion method is adequate for preparation of Sr2CeO4 in the form of spherical fine particles.

Elucidando os estados de oxidação do nitrogênio através da espectroscopia de absorção de raios-X na borda K do nitrogênio

The potentialities of X-ray Absorption Near Edge Spectroscopy (XANES) of the N K edge (N K) obtained with the spherical grating monochromator beam line at the Brazilian National Synchrotron Light Laboratory are explored in the investigation of poly(aniline), nanocomposites and dyes. Through the analysis of N K XANES spectra of conducting polymers and many other dye compounds that are dominated by 1s®p* transitions, it was possible to correlate the band energy value with the nitrogen oxidation states. An extensive N K XANES spectral database was obtained, thus permitting the elucidation of the nature of different nitrogens present in the intercalated conducting polymers.

Descrições estruturais cristalinas de zeólitos

Crystalline structures of zeolites can be studied using different representations: the internal symmetry obtained by X-Ray or neutron diffraction crystallography techniques or a systematic analysis of the basic structural units which can be arranged to build the geometries of each kind of zeolite. In this work the basic concepts of three building units, SBU (Secondary Building Units), SSU (Structural SubUnits) and PBU (Periodic Building Units) are presented. The properties of the resulting crystalline structures are discussed (pores, cavities, channels), describing the influence of each one of these properties in processes of physical-chemical interest. Representative case studies of known zeolite crystalline structures are also discussed in terms of their space group classification.

Biomateriais: deposição de hidroxiapatita sobre superfície de Ti-cp modificada por aspersão térmica

The osseointegrated titanium implants are reliable and safe alternatives to treatments for long periods of time. For surface modification, thermal aspersion of TiO2 was used. The samples with and without TiO2 were treated with NaOH and SBF in order to obtain a layer of HA. Characterization was done by SEM and FTIR. The images of HA obtained by SEM show a uniform morphology and a porous structure with spherical particles. The IR spectra show that the surface of Ticp/ TiO2 is more favorable for the HA deposit, as can be seen by the increase of the crystalline structure and the very intense and defined bands of the OH group of HA that is verified about 3571 and 630 cm-1. Thus the Ticp/ TiO2 surface presents a satisfactory nucleation of HA when compared to Ticp.

Cucurbiturilas

This review article describes the properties and the main applications of the glicol[n]urils. These compounds are cavitands made of n glycolurilic units arranged in circles, giving rise to extremely symmetric toroidal molecules. The cucurbit[n]urils create this way variable-sized hydrophobic cavities and the glycolurilic carbonyles delimit two portals on these cavities, slightly narrower than their internal radii. Their structure, physical and chemical properties favor the formation of inclusion compounds, and turn them into important building blocks for supramolecular chemistry and nanotechnology.

Propriedades e aplicações recentes das ciclodextrinas

Cyclodextrins (CDs) are cyclic oligosaccharides comprised of six or more glucose units connected by alpha-1,4 bonds. They have hydrophobic cavities with a hydrophilic exterior, and are versatile receptors for a variety of substrates. This ability allows them to be applied in many fields, as distinct as supramolecular chemistry, nanotechnology, pharmaceuticals, green chemistry, agrochemicals, analytical chemistry, toiletries, foods, and cosmetics. This review summarizes several aspects related to the physico-chemical properties of CDs and discusses their potential applications illustrated by recent examples. The prospects for their use in several areas are also described.

Caracterización y clasificación geoquímica de asfaltitas cubanas

Traditional biomarker parameters and aromatic compounds were applied to characterize and classify ten Cuban asphaltites (asphaltene-rich petroleum occurring as seeps or filling veins, joints, cavities and fissures). Genetic molecular parameters were compared in order to establish oil-oil correlations between samples. Thermal evolution was investigated using saturated biomarker and aromatic maturity parameters. All samples seem to represent petroleum in the early catagenetic stage. Statistical procedures used as auxiliary techniques show that they represent oils of Family II (marine anoxic carbonate sourced oils), except for 2 samples interpreted as belonging to Family III oils (normal marine siliciclastic suboxic sourced oils).

Estudo da síntese da zeólita MCM-71

A new kind of material, denominated MCM-71, was synthesized and characterized by several complementary techniques: X Ray Diffractometry, textural analysis by nitrogen adsorption, Scanning electronic microscopy and infrared spectroscopy. MCM-71 zeolite was successfully synthesized by hydrothermal synthesis in the presence of triethanolamine. Mordenite phase as impurity was not detected, otherwise quartz was observed. The MCM-71 sample obtained presented a BET surface area of 20 m²/g in the as synthesized form and of 85 m²/g in protonic form. By SEM was observed crystals with rectangular shape with average size of 2 x 0,2 x 0,05 µm and this crystals were agglomerated in spherical particles with average diameter between 14 and 24 µm.

High encapsulation efficiency of sodium alendronate in eudragit S100/HPMC blend microparticles

The hydrophilic drug sodium alendronate was encapsulated in blended microparticles of Eudragit® S100 and Methocel® F4M or Methocel® K100LV. Both formulations prepared by spray-drying showed spherical collapsed shape and smooth surface, encapsulation efficiencies of 85 and 82% and mean diameters of 11.7 and 8.4 µm, respectively. At pH 1.2, in vitro dissolution studies showed good gastro-resistance for both formulations. At pH 6.8, the sodium alendronate release from the microparticles was delayed and was controlled by Fickian diffusion. In conclusion, the prepared microparticles showed high encapsulation efficiency of sodium alendronate presenting gastro-resistance and sustained release suitable for its oral administration.

Utilização do acetato de celulose produzido a partir da celulose extraída do caroço de manga como matriz para produção de sistemas microparticulados

Cellulose acetate produced from mango seed fibers cellulose was used as a matrix for preparation of microparticles empty and load with acetaminophen (Paracetamol) in order to evaluate the incorporation of an active agent during the formation of microparticles. The microparticles are characterized by Fourier Transformed Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). The incorporation of paracetamol can be confirmed by the change in value of glass transition temperature (Tg). The formation of microparticles spherical was observed by SEM and showed an average diameter of 1.010 and 0.950 mm for empty and load microparticles respectively.

Thermal and structural study of guava (Psidium guajava L) powders obtained by two dehydration methods

Two food products (powders) were obtained by hot-air drying or lyophilisation methods on the whole guava fruits. The powders were characterised by sensory and thermal analyses (TGA-DSC), infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermal, morphological and structural characterisations showed a similar behaviour for the two solids. TGA-DSC and IR showed the presence of pectin as the main constituent of solids. A semi-crystalline profile was evidenced by XRD, and lamellar/spherical morphologies were observed by SEM. Sensory analyses revealed an aroma highly related to guava. These value-added food products are an alternative to process guava and avoid loss during postharvest handling.

Encapsulation of naproxen in nanostructured system: structural characterization and in vitro release studies

Nanoparticles were produced by solvent emulsification evaporation method with the following characteristics: nanometric size (238 ± 3 nm), narrow polydispersity index (0.11), negative zeta potential (-15.1 mV), good yield of the process (73 ± 1.5%), excellent encapsulation efficiency (81.3 ± 4.2%) and spherical shape. X-rays diffraction demonstrated the loss of drug crystallinity after encapsulation; however, the profile of the diffractograms of the poly-ε-caprolactone (PCL) nanoparticles was kept. Differential scanning calorimetry thermograms, correspondingly, exhibited the loss of drug melting peak and the increasing of the melting point of the PCL nanoparticles, evidencing an interaction drug-polymer. Naproxen release was low and sustained obeying the Higuchi´s kinetic. The results show that nanoparticles are promising sustained release system to the naproxen.

Evaluation of chitosan microparticles containing curcumin and crosslinked with sodium tripolyphosphate produced by spray drying

The aim of this study was to encapsulate curcumin into chitosan, using sodium tripolyphosphate (TPP) as an ionic crosslinker by the spray drying method. The influence of TPP on the properties of the final product, such as solubility, morphology, loading efficiency, thermal behavior, swelling degree and release profiles, was evaluated. The microparticles had a spherical morphology (0.5-20 µm) with no apparent porosity or cracks. Results indicated the formation of a polymeric network, which ensures effective protection for curcumin. Controlled-release studies were carried out at pH 1.2 and 6.8, to observe the influence of pH on curcumin release while the mechanism was analyzed using the Korsmeyer-Peppas equation.

Desenvolvimento e caracterização de nanopartículas lipídicas destinadas à aplicação tópica de dapsona

In this work, theospheres (innovative lipid nanoparticles) were prepared by the high pressure homogenization technique using different surfactants for dapsone encapsulation. Mean particle size ranged from 105 to 153 nm and negative zeta potentials were obtained for all theosphere formulations. Atomic force microscopy images confirmed the spherical shape of theospheres. The HPLC method used to determine dapsone-loaded theospheres was selective, linear, exact and precise. The entrapment efficiency of dapsone was 91.4%. Theospheres provided controlled release of idebenone (52.7 ± 1.6%) in comparison to the free drug (103.1 ± 1.9%).