Preparation and structural characterization of rare-earth doped lead lanthanum zirconate titanate ceramics

A new preparation route towards rare-earth (RE) doped polycrystalline lead lanthanum zirconate titanate (PLZT) ceramics (RE = Y(3+), Nd(3+), Yb(3+)), based on the use of doped lanthanum oxide or zirconia, is reported. Structural characterization by X-ray powder diffraction reveals that secondary phase formation can be substantially diminished in comparison to conventional preparation methods. The distribution of the rare-earth dopants was investigated as a function of concentration by static (207)Pb spin echo NMR spectra, using Fourier Transformation of Carr-Purcell-Meiboom-Gill spin echo trains. For the Nd- and Yb-doped materials, the interaction of the (207)Pb nuclei with the unpaired electron spin density results in significant broadening and shifting of the NMR signal, whereas these effects are absent in the diamagnetic Y(3+) doped materials. Based on different concentration dependences of the NMR lineshape parameters, we conclude that the structural role of the Nd(3+) dopants differs significantly from that of Yb(3+). While the Nd(3+) ions appear to be statistically distributed in the PLZT lattice, incorporation of Yb(3+) into PLZT appears to be limited by the appearance of doped cubic zirconia as a secondary phase. (C) 2009 Elsevier Masson SAS. All rights reserved.

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.

Fluorescent AlPO(4) gels and glasses doped with Rhodamine 6G: Preparation, structural and optical characterization

Fluorescent AlPO(4) xerogels doped with different amounts of Rhodamine 6G (Rh6G) laser dye were prepared by a one-step sal-gel process. In addition, mesoporous AlPO(4) glasses obtained from undoped gels were loaded with different amounts of Rh6G by wet impregnation. Optical excitation and emission spectra of both series of samples show significant dependences on Rh6G concentration, revealing the influence of dye molecular aggregation. At comparable dye concentrations the aggregation effects are found to be significantly stronger in the gels than in the mesoporous glasses. This effect might be attributed to stronger interactions between the dye molecules and the glass matrix, resulting in more efficient dye dispersion in the latter. The interaction of Rh6G with the glassy AlPO(4) network has been probed by (27)Al and (31)P solid-state NMR techniques. New five- and six-coordinated aluminum environments have been observed and characterized by advanced solid-state NMR techniques probing (27)Al-(1)H and (27)Al-(31)P internuclear dipole couplings. The fractional area of these new Al sites is correlated with the combined fractional area of two new Q(3Al)((0)) and Q(2Al)((0)) phosphate species observed in the (31)P MAS NMR spectra. Based on this correlation as well as detailed composition dependent studies, we suggest that the new signals arise from the breakage of Al-O-P linkages associated with the insertion process. (C) 2010 Elsevier B.V. All rights reserved.

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.

Bond Strength and Etching Pattern of Adhesive Systems to Enamel: Effects of Conditioning Time and Enamel Preparation

Statement of the problem: The performance of self-etch systems on enamel is controversial and seems to be dependent on the application technique and the enamel preparation. Purpose of the Study: To examine the effects of conditioning time and enamel surface preparation on bond strength and etching pattern of adhesive systems to enamel. Materials and Methods: Ninety-six teeth were divided into 16 conditions (N = 6) in function of enamel preparation and conditioning time for bond strength test. The adhesive systems OptiBond FL (Kerr, Orange, CA, USA), OptiBond SOLO Plus (Kerr), Clearfil SE Bond (Kuraray, Osaka, Japan), and Adper Prompt L-Pop (3M ESPE, St. Paul, MN, USA) were applied on unground or ground enamel following the manufacturers` directions or doubling the conditioning time. Cylinders of Filtek Flow (0.5-mm height) were applied to each bonded enamel surface using a Tygon tube (0.7 mm in diameter; Saint-Gobain Corp., Aurora, OH, USA). After storage (24 h/37 degrees C), the specimens were subjected to shear force (0.5 mm/min). The data were treated by a three-way analysis of variance and Tukey`s test (alpha = 0.05). The failure modes of the debonded interfaces and the etching pattern of adhesives were observed using scanning electron microscopy. Results: Only the main factor ""adhesive"" was statistically significant (p < 0.001). The lowest bond strength value was observed for OptiBond FL. The most defined etching pattern was observed for 35% phosphoric acid and for Adper Prompt L-Pop. Mixed failures were observed for all adhesives, but OptiBond FL showed cohesive failures in resin predominantly. Conclusions: The increase in the conditioning time as well as the enamel pretreatment did not provide an increase in the resin-enamel bond strength values for the studied adhesives. CLINICAL SIGNIFICANCE The surface enamel preparation and the conditioning time do not affect the performance of self-etch systems to enamel. (J Esthet Restor Dent 20:322-336, 2008)

Novel immunoadjuvants based on cationic lipid: Preparation, characterization and activity in vivo

The interactions between three different protein antigens and dioctadecyldimethylammonium bromide (DODAB) dispersed in aqueous solutions from probe sonication or adsorbed its one bilayer onto particles was comparatively investigated. The three model proteins were bovine serum albumin (BSA), purified 18 kDa/14 kDa antigens from Taenia crassiceps (18/14-Tcra) and a recombinant, heat-shock protein hsp-18 kDa from Mycobacterium leprae. Protein-DODAB complexes in water solution were characterized by dynamic light scattering for sizing and zeta-potential analysis. Cationic complexes (80-100 nm of mean hydrodynamic diameter) displayed sizes similar to those of DODAB bilayer fragments (BF) in aqueous solution and good colloid stability over a range of DODAB and protein concentrations. The amount of cationic lipid required for attaining zero of zeta-potential at a given protein amount depended on protein nature being smaller for 18 kDa/14 kDa antigens than for BSA. Mean diameters for DODAB/protein complexes increased, whereas zeta-potentials decreased with NaCl or protein concentration. In mice, weak IgG production but significant cellular immune responses were induced by the complexes in comparison to antigens alone or carried by aluminum hydroxide as shown from IgG in serum determined by ELISA, delayed type hypersensitivity reaction from footpad swelling tests and cytokines analysis. The novel cationic adjuvant/protein complexes revealed good colloid stability and potential for vaccine design at a reduced DODAB concentration. (C) 2009 Elsevier Ltd. All rights reserved.

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.

Iron oxyhydroxide nanostructured in montmorillonite clays: Preparation and characterization

Akaganeite is a very rare iron oxyhydroxide in nature. It can be obtained by many synthetic routes, but thermohydrolysis is the most common method reported in the literature. In this work, akaganeite-like materials were prepared through the thermohydrolysis of FeCl(3)center dot 6H(2)O in water and suspensions containing clay minerals. X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) data show that the clays determine the crystal phase and size of the iron oxyhydroxide crystals. According to XRD and FTIR data, beta-FeO(OH) (akaganeite) is the main metal oxyhydroxide phase. Considering the small basal spacing (d(0 0 1)) displacement observed when comparing the XRD patterns of pristine clays with the composites containing beta-FeO(OH), the iron oxyhydroxide should be mostly located on the basal and edge surfaces of the clay minerals. UV-Vis electronic absorption spectra indicate that the preferred phase of the iron oxyhydroxide is determined by the nature of the clay minerals. (C) 2010 Elsevier Inc. All rights reserved.

Preparation and photoluminescence properties of functionalized silica materials incorporating europium complexes

In the present work, the surface of the Eu-BTC = [Eu(EMA)(H(2)O)(2)], [Eu(TLA)(H(2)O)(4)] and [Eu(TMA)(H(2)O)(6)] complexes (EMA = 1,2,3-benzenetricarboxylate, TLA = 1,2,4-benzenetricarboxylate and TMA = 1,3,5-benzenetricarboxylate) was modified using 3-aminopropyltriethoxysilane (APTES) by a new microwave assisted method that proved to be simple and efficient. According to our observations, the most efficient luminescence is the material based on APTES incorporating [Eu(TMA)(H(2)O)(6)] complexes, denoted as Eu-TMA-Si, shows the highest emission efficiency. Therefore, it is proposed as a promising material for molecular conjugation in clinical diagnosis. (C) 2011 Elsevier B.V. All rights reserved.

Functionalized organozincates and organocuprates derived from gamma-hydroxytellurides in the preparation of 1,4-hydroxyketones

A C-O-dianionic zincate was generated by a Te/Li exchange reaction of an alkyltelluride, followed by Li/Zn transmetallation and reaction with methyllithium. The reaction between the enantiomerically pure (99% ee) (R)-dianionic zincate and benzoyl chloride led to 3-hydroxy-1-phenyl pentanone with total retention of the carbon configuration (99% ee). Similar results were obtained using the corresponding Lipshutz cyanocuprates. (C) 2009 Elsevier Ltd. All rights reserved.

Preparation of supported Pt(0) nanoparticles as efficient recyclable catalysts for hydrogenation of alkenes and ketones

A magnetically recoverable Pt(0) catalyst was prepared by in situ H(2) reduction of Pt(2+) species bound to an amino modified silica-coated magnetic nanoparticles. Compared to ordinary silica (maximum uptake Pt 0.03 wt%), the amino-functionalized silica surfaces were loaded with 1.95 wt% of metal. The supported Pt(0) nanoparticles exhibit high catalytic activity in the hydrogenation of alkenes and ketones under solventless mild reaction conditions. Partially hydrogenated products could also be isolated. The magnetic property of the catalyst grants a fast and efficient product isolation compared to traditional methods used in heterogeneous systems that generally make use of time- and solvent-consuming procedures. (C) 2009 Elsevier B.V. All rights reserved.

Host-guest system of 4-nerolidylcatechol in 2-hydroxypropyl-beta-cyclodextrin: preparation, characterization and molecular modeling

The interaction of 4-nerolidylcatechol (4-NRC), a potent antioxidant agent, and 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was investigated by the solubility method using Fourier transform infrared (FTIR) methods in addition to UV-Vis, (1)H-nuclear magnetic resonance (NMR) spectroscopy and molecular modeling. The inclusion complexes were prepared using grinding, kneading and freeze-drying methods. According to phase solubility studies in water a B(S)-type diagram was found, displaying a stoichiometry complexation of 2:1 (drug:host) and stability constant of 6494 +/- A 837 M(-1). Stoichiometry was established by the UV spectrophotometer using Job`s plot method and, also confirmed by molecular modeling. Data from (1)H-NMR, and FTIR, experiments also provided formation evidence of an inclusion complex between 4-NRC and HP-beta-CD. 4-NRC complexation indeed led to higher drug solubility and stability which could probably be useful to improve its biological properties and make it available to oral administration and topical formulations.

Preparation and characterization of colloidal Ni(OH)(2)/bentonite composites

A conductive and electrochemically active composite material has been prepared by the combination of bentonite and nickel hydroxide precursor sol. This material exhibits the characteristic intercalation properties of the clay component and the electrochemical and optical properties of nickel hydroxide. The clay particles seem to induce the aggregation of nickel hydroxide, leading to the formation of a layer of alpha-Ni(OH)(2) exhibiting needle like morphology. The composite forms stable films and has been conveniently used for the preparation of modified electrodes exhibiting intercalation and electrochemical properties, thus providing an interesting material for the development of amperometric sensors. (C) 2008 Elsevier Ltd. All rights reserved.