Synthesis of YAP phase by a polymeric method and phase progression mechanisms

The phase formation kinetics of YAP (YAlO(3)) synthesized through the polymeric precursor method was investigated by thermal analysis, X-ray diffraction and FT-IR spectroscopy. We demonstrated that the YAP synthesis is highly dependent on the heat and mass transport during all stages of the synthesis route. In the first stages, during the preparation of amorphous precursor, ""hot spots"" need to be suppressed to avoid the occurrence of chemical inhomogeneities. Very high heating rates combined with small amorphous particles are advantageous in the last stage during the formation of crystalline phase. We were able to synthesize nanosized particles of YAP single phase at temperatures around 1100 A degrees C for future preparation of phosphors or ceramics for optics.

Preparation of Achiral and Chiral (E)-Enaminopyran-2,4-diones and Their Phytotoxic Activity

A short and efficient approach to a range of new chiral and achiral functionalized (E)-enaminopyran-2,4-diones starting with commercially available dehydroacetic acid is described. The phytotoxic properties of these (E)-enaminopyran-2,4-diones were evaluated by their ability to interfere with the growth of Sorghum bicolor and Cucumis sativus seedlings. A different sensitivity of the two crops was evident with the (E)-enaminopyran-2,4-diones. The most active compounds were also tested against two weeds, Ipomoea grandifolia and Brachiaria decumbens. To the best of our knowledge, this is the first report describing enaminopyran-2,4-diones as potential plant growth regulators.

Preparation and characterization of new glassy system As2P2S8-Ga2S3

Glasses having the composition (100 - x)As2P2S8-xGa(2)S(3) with x ranging from 0 to 50% were investigated to determine the compositional effect on properties and local structure. The glass transition temperature (T-g) and the stability parameter against crystallization (T-x - T-g) increased with the addition of Ga2S3. The structure of these glasses was probed by Raman scattering, Fourier transform infrared (FT-IR) and P-31 nuclear magnetic resonance. On the basis of the observed vibrations and the strength of the P-31-P-31 homonuclear magnetic dipolar coupling, two scenarios can be proposed for the structural evolution induced by the addition of Ga2S3. For x <= 20% we may have the formation of GaS4E- groups (E = nonbonding electron), and for x >= 30% we have depolymerization of the As2P2S8 units and the formation of a network of GaPS4 units with each PS4/2 unit (Q(4)) species carrying a single positive formal charge.

Solvothermal Preparation of Drug Crystals: Didanosine

For the first time, crystals of suitable size for X-ray diffractometry structure determination (Dian important anti-HI V drug were prepared under solvothermal conditions. In this study, the crystal structure of didanosine (2`,3`-dideoxyinosine, ddI) in the form of a hydrate was determined using single-crystal X-ray diffractometry. Powder X-ray diffraction analysis revealed that the solid-state phase of the drug incorporated into pharmaceutical solid dosage forms is isostructural to the solvothermally prepared ddI material, even though they do not exhibit an identical chemical composition due to different water fractions occupying hydrophobic channels formed within the crystal lattice. Two ddI conformers are present in the structure, in agreement with a previous structure elucidation attempt. Concerning the keto enol equilibrium of ddI, our crystal data and vibrational characterizations by Fourier transform infrared (FTIR) and FT-Raman spectroscopy techniques were conclusive to state that both conformers exist in the keto form, contrary to solid-state NMR spectroscopic assignments that suggested ddI molecules occur as enol tautomers. In addition, characterizations by thermal (differential scanning calorimetry) and spectroscopic techniques allowed us to understand the structural similarities and the differences related to the hydration pattern of the nonstoichiometric hydrates.

Protoporphyrin IX Nanoparticle Carrier: Preparation, Optical Properties, and Singlet Oxygen Generation

The present study is focused on developing a nanoparticle carrier for the photosensitizer protoporphyrin IX for use in photodynamic therapy. The entrapment of protoporphyrin IX (Pp IX) in silica spheres was achieved by modification of Pp IX molecules with an organosilane reagent. The immobilized drug preserved its optical properties and the capacity to generate singlet oxygen, which was detected by a direct method from its characteristic phosphorescence decay curve at near-infrared and by a chemical method using 1,3-diphenylisobenzofuran to trap singlet oxygen. The lifetime of singlet oxygen when a suspension of Pp IX-loaded particles in acetonitrile was excited at 532 nm was determined as 52 mu s, which is in good agreement with the value determined for methylene blue in acetonitrile solution under the same conditions. The Pp IX-loaded silica particles have an efficiency of singlet oxygen generation (eta Delta) higher than the quantum yield of free porphyrins. This high efficiency of singlet oxygen generation was attributed to changes on the monomer-dimer equilibrium after photosentisizer immobilization.

Preparation and characterization of the novels terpolymers of poly-{trans-[RuCl(2)(vpy)(4)]-styrene-divinylbenzene} and styrene-divinylbenzene-vinylpiridine impregnated with silver nanoparticles

This paper reports the preparation and characterization of poly-{trans-[RuCl(2)(vpy)(4)]-styrene-divinylbenzene} and styrene-divinylbenzene-vinylpiridine filled with nanosilver. Theses materials were synthesized by non aqueous polymerization through a chemical reaction using benzoyl peroxide as the initiator. The nanosilver was obtained from chemical reduction using NaBH(4) as reducing agent and sodium citrate as stabilizer. The nanometric dimension of nanosilver was monitored by UV-visible and confirmed through TEM. The morphology was characterized by SEM and the thermal properties were done by TGA and DSC. The antimicrobial action of the polymers impregnated with nanosilver was evaluated using both microorganisms, Staphylococcus aureus and Escherichia coli. The antimicrobial activity of the poly-{trans-[RuCl(2)(vpy)(4)]-styrene-divinylbenzene} filled with nanosilver was confirmed by the presence of an inhibition halo of the bacterial growth in seeded culture media, but was not confirmed to the styrene-divinylbenzene-vinylpiridine. The present work suggest that trans - [RuCl(2)(vpy)(4)] complex facilitate the release of silver ion from the media.

Ligand-Assisted Preparation of Palladium Supported Nanoparticles: a Step toward Size Control

Supported nanoparticles (SNPs) with narrow size distribution were prepared by H(2) reduction of Pd(2+) previously bound, to ligand-modified silica surfaces. Interestingly, the size of the Pd SNPs was tuned by the ligand grafted on the support surface. Amino- and ethylenediamino-functionalized supports formed Pd(0) SNPs of ca. 6 and 1 nm, respectively. The catalytic properties of both Pd(0) SNPs were investigated.

Co catalysts supported on SiO(2) and gamma-Al(2)O(3) applied to ethanol steam reforming: Effect of the solvent used in the catalyst preparation method

Cobalt catalysts were prepared on supports of SiO(2) and gamma-Al(2)O(3) by the impregnation method, using a solution of Co precursor in methanol. The samples were characterized by XRD, TPR, and Raman spectroscopy and tested in ethanol steam reforming. According to the XRD results, impregnation with the methanolic solution led to smaller metal crystallites than with aqueous solution, on the SiO(2) support. On gamma-Al(2)O(3), all the samples exhibited small crystallites, with either solvent, due to a higher Co-support interaction that inhibits the reduction of Co species. The TPR results were consistent with XRD results and the samples supported on gamma-Al(2)O(3) showed a lower degree of reduction. In the steam reforming of ethanol, catalysts supported on SiO(2) and prepared with the methanolic solution showed the best H(2), CO(2) and CO selectivity. Those supported on gamma-Al(2)O(3) showed lower H(2) selectivity. (C) 2011 Elsevier Ltd. All rights reserved.

Preparation of alpha,beta-Unsaturated Diazoketones Employing a Horner-Wadsworth-Emmons Reagent

A new method for the preparation of alpha,beta-unsaturated diazoketones from aldehydes and a Horner-Wadsworth- Emmons reagent is reported. The method was applied to the short synthesis of two substituted pyrrolidines.

A novel nanostructured composite formed by interaction of copper octa(3-aminopropyl)octasilsesquioxane with azide ligands: Preparation, characterization and a voltammetric application

This study presents the preparation, characterization and application of copper octa(3-aminopropyl)octasilsesquioxane following its subsequent reaction with azide ions (ASCA). The precursor (AC) and the novel compound (ASCA) were characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), scanning electronic microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric analyses and voltammetric technique. The cyclic voltammogram of the modified graphite paste electrode with ASCA (GPE-ASCA), showed one redox couple with formal potential (E(1/2)(ox)) = 0.30 V and an irreversible process at 1.1 V (vs. Ag/AgCl; NaCl 1.0 M; v = 20 mV s(-1)). The material is very sensitive to nitrite concentrations. The modified graphite paste electrode (GPE-ASCA) gives a linear range from 1.0 x 10(-4) to 4.0 x 10(-3) mol L(-1) for the determination of nitrite, with a detection limit of 2.1 x 10(-4) mol L(-1) and the amperometric sensitivity of 8.04 mA/mol L(-1). (C) 2010 Elsevier Ltd. All rights reserved.

Influência do método de síntese e caracterização de pós compósitos de NiO- Ce1-xEuxO2-δ para anodos catalíticos de células a combustível

Fuel cells are electrochemical devices that convert chemical energy into electricity. Due to the development of new materials, fuel cells are emerging as generating clean energy generator. Among the types of fuel cells, categorized according to the electrode type, the solid oxide fuel cells (SOFC) stand out due to be the only device entirely made of solid particles. Beyond that, their operation temperature is relatively high (between 500 and 1000 °C), allowing them to operate with high efficiency. Another aspect that promotes the use of SOFC over other cells is their ability to operate with different fuels. The CeO2 based materials doped with rare earth (TR+3) may be used as alternatives to traditional NiO-YSZ anodes as they have higher ionic conductivity and smaller ohmic losses compared to YSZ, and can operate at lower temperatures (500-800°C). In the composition of the anode, the concentration of NiO, acting as a catalyst in YSZ provides high electrical conductivity and high electrochemical activity of reactions, providing internal reform in the cell. In this work compounds of NiO - Ce1-xEuxO2-δ (x = 0.1, 0.2 and 0.3) were synthesized from polymeric precursor, Pechini, method of combustion and also by microwave-assisted hydrothermal method. The materials were characterized by the techniques of TG, TPR, XRD and FEG-SEM. The refinement of data obtained by X-ray diffraction showed that all powders of NiO - Cex-1EuxO2-δ crystallized in a cubic phase with fluorite structure, and also the presence of Ni. Through the characterizations can be proved that all routes of preparation used were effective for producing ceramics with characteristics suitable for application as SOFC anodes, but the microwave-assisted hydrothermal method showed a significant reduction in the average grain size and improved control of the compositions of the phases

Estudo dos óxidos A2B2O7 e ABO3 a base de terras raras, para aplicações térmicas e catalíticas a altas temperaturas

Rare earth elements have recently been involved in a range of advanced technologies like microelectronics, membranes for catalytic conversion and applications in gas sensors. In the family of rare earth elements like cerium can play a key role in such industrial applications. However, the high cost of these materials and the control and efficiencies associated processes required for its use in advanced technologies, are a permanent obstacle to its industrial development. In present study was proposed the creation of phases based on rare earth elements that can be used because of its thermal behavior, ionic conduction and catalytic properties. This way were studied two types of structure (ABO3 and A2B2O7), the basis of rare earths, observing their transport properties of ionic and electronic, as well as their catalytic applications in the treatment of methane. For the process of obtaining the first structure, a new synthesis method based on the use of EDTA citrate mixture was used to develop a precursor, which undergone heat treatment at 950 ° C resulted in the development of submicron phase BaCeO3 powders. The catalytic activity of perovskite begins at 450 ° C to achieve complete conversion at 675 ° C, where at this temperature, the catalytic efficiency of the phase is maximum. The evolution of conductivity with temperature for the perovskite phase revealed a series of electrical changes strongly correlated with structural transitions known in the literature. Finally, we can establish a real correlation between the high catalytic activity observed around the temperature of 650 ° C and increasing the oxygen ionic conductivity. For the second structure, showed clearly that it is possible, through chemical processes optimized to separate the rare earth elements and synthesize a pyrochlore phase TR2Ce2O7 particular formula. This "extracted phase" can be obtained directly at low cost, based on complex systems made of natural minerals and tailings, such as monazite. Moreover, this method is applied to matters of "no cost", which is the case of waste, making a preparation method of phases useful for high technology applications

Preparation and structural characterization of vulcanized natural rubber nanocomposites containing nickel-zinc ferrite nanopowders

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Praziquantel-loaded PLGA nanoparticles: preparation and characterization

Nanoparticles containing praziquantel made of Poly (D,L-lactide-co-glycolide) were designed by an emulsion-solvent evaporation method. Two organic solvents were separately utilized as disperse phase: methylene chloride and ethyl acetate. The size of the particles prepared with the former solvent was bigger than the particles prepared with the latter. The entrapment efficiency was bigger when methylene chloride was used, 79.82% in comparison with 29.27% by using ethyl acetate. DSC and infrared studies showed that no strong chemical interaction between drug and polymer occurred. Release kinetics of praziquantel, used as a model drug, was governed not only by actual drug loading but also by particles size. The higher the drug content and the smaller the particle size resulted in faster drug release.

Thermal study and physico-chemical characterization of some functional properties of guava seeds protein isolate (Psidium guajava)

The guava seed protein isolate ( PI) was obtained from the protein precipitation belonging to the class of the gluteline (Ip 4.5). The conditions for the preparation of the PI were determined by both the solubility curve and simultaneous thermogravimetry-differential thermal analysis (TG-DTA): pH 11.5, absence of NaCl and whiteners and T=( 25 +/- 3) degrees C. Under these conditions a yield of 77.0 +/- 0.4%, protein content of 94.2 +/- 0.3, ashes 0.50 +/- 0.05% and thermal stability, T= 200 degrees C, were obtained. The TG-DTA curves and the PI emulsification capacity study showed the presence of hydrophobic microdomains at pH 11.5 and 3.0 suggesting a random coil protein conformation and, to pH 10.0, an open protein conformation. The capacity of emulsification (CE), in the absence of NaCl, was verified for: 1 - pH 3.0 and 8.5, using the IP extracted at pH 10.0 and 11.5, CE >= 343 +/- 5 g of emulsified oil/g of protein; 2 - pH 6.60 just for the PI obtained at pH 11.5, CE >= 140 +/- 8 g of emulsified oil/g of protein.