Effect of Different Solvent Ratios (Water/Ethylene Glycol) on the Growth Process of CaMoO(4) Crystals and Their Optical Properties

In this paper, calcium molybdate (CaMoO(4)) crystals (meso- and nanoscale) were synthesized by the coprecipitation method using different solvent volume ratios (water/ethylene glycol). Subsequently, the obtained suspensions were processed in microwave-assisted hydrothermal/solvothermal systems at 140 degrees C for 1 h. These meso- and nanocrystals processed were characterized by X-ray diffraction (X R I)), Fourier transform Raman (FT-Raman), Fourier transform infrared (FT-IR). ultraviolet visible (UV-vis) absorption spectroscopies, held-emission gun scanning electron microscopy (FEG-SEM). transmission electron microscopy (TEM). and photoluminescence (PL) measurements. X RI) patterns and FT-Raman spectra showed that these meso- and nanocrystals have a scheelite-type tetragonal structure without the presence of deleterious phases. FT-IR spectra exhibited a large absorption band situated at around 827 cm(-1), which is associated with the Mo-O anti-symmetric stretching vibrations into the [MoO(4)] clusters. FEG-SEM micrographs indicated that the ethylene glycol concentration in the aqueous solution plays an important role in the morphological evolution of CaMoO(4) crystals. High-resolution TEM micrographs demonstrated that the mesocrystals consist of several aggregated nanoparticles with electron diffraction patterns of monocrystal. In addition, the differences observed in the selected area electron diffraction patterns of CaMoO(4) crystals proved the coexistence of both nano- and mesostructures, First-principles quantum mechanical calculations based on the density functional theory at the B3LYP level were employed in order to understand the band structure find density of states For the CaMoO(4). UV-vis absorption measurements evidenced a variation in optical band gap values (from 3.42 to 3.72 cV) for the distinct morphologies. The blue and green PI. emissions observed in these crystals were ascribed to the intermediary energy levels arising from the distortions on the [MoO(4)] clusters clue to intrinsic defects in the lattice of anisotropic/isotropic crystals.

Structure and optical properties of [Ba(1-x)Y(2x/3)](Zr(0.25)Ti(0.75))O(3) powders

[Ba(1-x)Y(2x/3)](Zr(0.25)Ti(0.75))O(3) powders with different yttrium concentrations (x = 0, 0.025 and 0.05) were prepared by solid state reaction. These powders were analyzed by X-ray diffraction (XRD). Fourier transform Raman scattering (FT-RS), Fourier transform infrared (FT-IR) and X-ray absorption near-edge (XANES) spectroscopies. The optical properties were investigated by means of ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. Even with the addition of yttrium, the XRD patterns revealed that all powders crystallize in a perovskite-type cubic structure. FT-RS and FT-IR spectra indicated that the presence of [YO(6)] clusters is able to change the interaction forces between the O-Ti-O and O-Zr-O bonds. XANES spectra were used to obtain information on the off-center Ti displacements or distortion effects on the [TiO(6)] clusters. The different optical band gap values estimated from UV-vis spectra suggested the existence of intermediary energy levels (shallow or deep holes) within the band gap. The PL measurements carried out with a 350 nm wavelength at room temperature showed that all powders present typical broad band emissions in the blue region. (C) 2010 Elsevier Masson SAS. All rights reserved.

Synthesis, characterization, crystal structure, and biological studies of vanadium complexes with glycolic acid

Synthesis, characterization, crystal structure, and biological studies of two complexes with glycolic acid are described. The solid complexes were formulated as K2[VO(C2H2O3)(C2H3O3)2] H2O (1) and K2[{VO2(C2H2O3)}2] (2) and characterized by X-ray studies, Fourier transform infrared spectroscopy (FTIR), Electron paramagnetic resonance (EPR), and magnetic susceptibility. Conversion of 1 to 2 was studied in aqueous solution by UV-Vis spectroscopy and in the solid state by diffuse reflectance spectroscopy. Complex 2 contains dinuclear [{VO2(C2H2O3)}2]2- anions in which glycolate(2-) is a five-membered chelating ring formed by carboxylate and -hydroxy groups. The geometry around the vanadium in 2 was interpreted as intermediate between a trigonal bipyramid and a square pyramid. Vanadium(IV) is pentacoordinate in 1 as a distorted square pyramid. Complex 1 contains a vanadyl group (V=O) surrounded by two oxygens from deprotonated carboxylate and hydroxy groups forming a five-membered ring. Two oxygens from different glycolates(1-) are bonded to the (V=O) also. Biological analysis for potential cytotoxic effects of 1 was performed using Human Cervix Adenocarcinoma (HeLa) cells, a human cervix adenocarcinoma-derived cell line. After incubation for 48 h, 1 causes 90 and 95% of HeLa cells death at 20 and 200 mol L-1, respectively.

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.

gamma-zein secondary structure in solution by circular dichroism

The proline-rich N-terminal domain of gamma-zein has been reported in relevant process, which include its ability to cross the cell membranes. Evidences indicate that synthetic hexapeptide (PPPVHL), naturally found in N-terminal portion of gamma-zein, can adopt the polyproline II (PPII) conformation in aqueous solution. The secondary structure of gamma-zein in maize protein bodies had been analyzed by solid state Fourier transform infrared and nuclear magnetic resonance spectroscopies. However, it was not possible to measure PPII content in physiological environment since the beta-sheet and PPII signals overlap in both solid state techniques. Here, the secondary structure of gamma-zein has been analyzed by circular dichroism in SDS aqueous solution with and without ditiothreitol (DTT), and in 60% of 2-propanol and water with DTT The results show that gamma-zein has high helical content in all solutions. The PPII conformation was present at about 7% only in water/DTT solution. (c) 2007 Wiley Periodicals, Inc.

Highly Stable, Edible Cellulose Films Incorporating Chitosan Nanoparticles

The need for biodegradable polymers for packaging has fostered the development of novel, biodegradable polymeric materials from natural sources, as an alternative to reduce amount of waste and environmental impacts. The present investigation involves the synthesis of chitosan nanoparticles-carboxymethylcellulose films, in view of their increasing areas of application in packaging industry. The entire process consists of 2-steps including chitosan nanoparticles preparation and their incorporation in carboxymethylcellulose films. Uniform and stable particles were obtained with 3 different chitosan concentrations. The morphology of chitosan nanoparticles was tested by transmission electron microscopy, revealing the nanoparticles size in the range of 80 to 110 nm. The developed film chitosan nanoparticles-carboxymethylcellulose films were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis, solubility tests, and mechanical analysis. Improvement of thermal and mechanical properties were observed in films containing nanoparticles, with the best results occurring upon addition of nanoparticles with 110 nm size in carboxymethylcellulose films. Practical Application Carboxymethylcellulose films containing chitosan nanoparticles synthesized and characterized in this article could be a potential material for food and beverage packaging applications products due to the increase mechanical properties and high stability. The potential application of the nanocomposites prepared would be in packaging industry to extend the shelf life of products.

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.

Hybrid materials from intermolecular associations between cationic lipid and polymers

Intermolecular associations between a cationic lipid and two model polymers were evaluated from preparation and characterization of hybrid thin films cast on silicon wafers. The novel materials were prepared by spin-coating of a chloroformic solution of lipid and polymer on silicon wafer. Polymers tested for miscibility with the cationic lipid dioctadecyldimethylammonium bromide (DODAB) were polystyrene (PS) and poly(methyl methacrylate) (PMMA). The films thus obtained were characterized by ellipsometry, wettability, optical and atomic force microscopy, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and activity against Escherichia coli. Whereas intermolecular ion-dipole interactions were available for the PMMA-DODAB interacting pair producing smooth PMMA-DODAB films, the absence of such interactions for PS-DODAB films caused lipid segregation, poor film stability (detachment from the silicon wafer) and large rugosity. In addition, the well-established but still remarkable antimicrobial DODAB properties were transferred to the novel hybrid PMMA/DODAB coating, which is demonstrated to be highly effective against E. coli.

Immobilization of liposomes in nanostructured layer-by-layer films containing dendrimers

Artificial vesicles or liposomes composed of lipid bilayers have been widely exploited as building blocks for artificial membranes, in attempts to mimic membrane interaction with drugs and proteins and to investigate drug delivery processes. In this study we report on the immobilization of liposomes of 1,2-dipalmitoyi-sn-Glycero-3-[Phospho-rac-(1-glycerol)] (Sodium Salt) (DPPG) in layer-by-layer (LbL) films, alternated with poly (amidoamine) G4 (PAMAM) dendrimer layers. The average size of the liposomes in solution was 120 nm as determined by dynamic light scattering, with their spherical shape being inferred from scanning electron microscopy (SEM) in cast films. LbL films containing up to 20 PAMAM/DPPG bilayers were assembled onto glass and/or silicon wafer substrates. The growth of the multilayers was achieved by alternately immersing the substrates into the PAMAM and DPPG solutions for 5 and 10 min, respectively. The formation of PAMAM/DPPG liposome multilayers and its ability to interact with BSA were confirmed by Fourier transform infrared spectroscopy (FTIR). The structural features and film thickness were obtained using X-ray diffraction and surface plasmon resonance (SPR). (c) 2007 Elsevier B.V. All rights reserved.

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.

Synthesis and Characterization of Magnetic Composites Based on Cis-Polyisoprene and CoFe(2)O(4) Nanoparticles

CoFe(2)O(4) nanoparticles were obtained by the co-precipitation method. They were further modified by the adsorption of ricinoleic acid (RA). The non-modified and modified CoFe(2)O(4)/RA nanoparticles were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman, and Fourier transform infrared (FTIR) spectroscopy. The modified particles present a mean diameter < 20 nm. The adsorption of RA on the CoFe(2)O(4) surface is characterized by the IR absorptions of the RA while in the Raman spectrum the predominant signals are those from the CoFe(2)O(4). The cis-polyisoprene (PI) composite was prepared by dissolving PI in cyclohexane followed by the addition of a magnetic fluid based on CoFe(2)O(4)/RA nanoparticles dispersed in cyclohexane. After solvent evaporation a magnetic composite was obtained and characterized by AFM, Raman, and FTIR measurements. AFM images show uniformly CoFe(2)O(4)/RA particles distributed in the PI matrix. Raman spectra obtained for the composites reveal the characteristic Raman peaks of PI and CoFe(2)O(4) nanoparticles.

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.

Structural Investigation of MFe(2)O(4) (M = Fe, Co) Magnetic Fluids

Ferrites of the type M(II)Fe(2)O(4) (M = Fe and Co) have been prepared by the traditional coprecipitation method. These ferrites were modified by the adsorption of fatty acids derived from soybean and castor oil and were then dispersed in cyclohexane, providing very stable magnetic fluids, readily usable in nonpolar media. The structural properties of the ferrites and modified ferrites as well as the magnetic fluids were characterized by XRD (X-ray powder diffraction), TEM (transmission electron microscopy), DRIFTS (diffusion reflectance infrared Fourier transform spectroscopy), FTMR (Fourier transform near-infrared), UV-vis, normal Raman spectroscopy, and surface-enhanced Raman scattering (SERS). XRD and TEM analysis have shown that the magnetic nanoparticles (nonmodified and modified) present diameters in the range of 10-15 nm. DRIFTS measurements have shown that the carboxylate groups of soybean and castor oil fatty acids adsorb on the ferrite surface, forming three different structures: a bridging bidentate, a bridging monodentate, and a bidentate chelate structure. The FTIR and Raman spectra of nonmodified Fe(3)O(4) and CoFe(2)O(4) nanoparticles have shown that the number of observed phonons is not compatible with the expected O(h)(7) symmetry, since IR-only active phonons were observed. in the Raman spectra and vice versa. SERS measurements of a CoFe(2)O(4) thin film on a SERS-active gold electrode at different applied potentials made possible the assignment of the signals near 550 and 630 cm(-1) to Co-O motions and the signals near 470 and 680 cm(-1) to Fe-O motions.

Flexural properties, microleakage, and degree of conversion of a resin polymerized with conventional light and argon laser

Objective: To evaluate the flexural strength, microleakage, and degree of conversion of a microhybrid resin polymerized with argon laser and halogen lamp. Method and Materials: For both flexural test and degree of conversion analysis, 5 bar samples of composite resin were prepared and polymerized according to ISO 4049. The halogen light-curing unit was used with 500 MW/cm(2) for 20 seconds and the argon laser with 250 mW for 10 and 20 seconds. Samples were stored in distilled water in a dark environment at 37 degrees C for 24 hours. The flexural property was quantified by a 3-point loading test. For the microleakage evaluation, 60 bovine incisors were used to prepare standardized Class 5 cavities, which were restored and polished. Specimens were stored in distilled water for 24 hours at 37 degrees C and thermocycled 500 times (6 degrees C to 60 degrees C). Specimens were then immersed in art aqueous solution of basic fuchsin for 24 hours. Longitudinal sections of each restoration were obtained and examined with a stereomicroscope for qualitative evaluation of microleakage. Fourier transform (FT)-Raman RFS 100/S spectrometer (Bruker) was used to analyze the degree of conversion. Results: ANOVA showed no statistically significant differences of flexural strength between the photoactivation types evaluated in the flexural study. Microleakage data were statistically analyzed by Mann-Whitney and Kruskal-Wallis tests. Enamel margins resulted in a statistically lower degree of leakage than dentin margins. No statistically significant difference was found among the 3 types of photocuring studied. ANOVA also showed no statistically significant difference in the degree of conversion among the studied groups. Conclusion: According to the methodology used in this research, the argon laser is a possible alternative for photocuring, providing the same quality of polymerization as the halogen lamp. None of the photocured units tested in this study completely eliminated microleakage.

Compatibility studies between captopril and pharmaceutical excipients used in tablets formulations

Captopril (CAP) was the first commercially available angiotensine-converting enzyme (ACE) inhibitor. In the anti-hypertensive therapy is considered the selected drug has to be therapeutically effective together with reduced toxicity. CAP is an antihypertensive drug currently being administered in tablet form. In order to investigate the possible interactions between CAP and excipients in tablets formulations, differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis completed by X-ray powder diffraction (XRPD) and Fourier transform infrared spectroscopy (FTIR) were used for compatibility studies. A possible drug-excipient interaction was observed with magnesium stearate by DSC technique.