Fabio Furlan Ferreira

X-ray powder diffraction beamline at D10B of LNLS: application to the Ba2FeReO6 double perovskite

A new beamline, fully dedicated to X-ray powder diffraction (XPD) measurements, has been installed after the exit port B of the bending magnet D10 at the Brazilian Synchrotron Light Laboratory (LNLS) and commissioned. The technical characteristics of the beamline are described and some performance indicators are listed, such as the incoming photon flux and the angular/energy resolutions obtainable under typical experimental conditions. The results of a Rietveld refinement for a standard sample of Y2O3 using high-resolution data are shown. The refined parameters match those found in the literature, within experimental error. High-resolution XPD measurements on Ba2FeReO6 demonstrate a slight departure from the ideal cubic double-perovskite structure at low temperatures, not detected by previous powder diffraction experiments. The onset of the structural transition coincides with the ferrimagnetic ordering temperature, Tc approximately equal to 315 K. Subtle structural features, such as those reported here for Ba2FeReO6, as well as the determination and/or refinement of complex crystal structures in polycrystalline samples are ideal candidate problems to be investigated on this beamline.

Electrochromic nickel oxide thin films deposited under different sputtering conditions

Abstract In this work, non stoichiometric nickel oxide (NiO x ) thin films were deposited by r.f. reactive sputtering of a metallic nickel target in an O 2 -Ar atmosphere. A systematic variation of two deposition parameters was done: the oxygen flux (φ) and the r.f. power ( P ). The electrochemical characterization of the films was performed in aqueous electrolyte. The spectral transmittance measurements, as well as the X-ray diffraction analysis were performed ex-situ, while monochromatic transmittance and stress measurements were performed in situ. Samples deposited at low oxygen flux (or high power) are transparent, in contrast to those deposited at high oxygen flux (or low power), which are dark brown. The films were cubic NiO, with preferred orientation in the (111) direction. Lattice parameters increase with increasing oxygen flux during deposition, but decrease with increasing power. For all samples, the ratio O Ni was greater than 1, as determined by Rutherford back-scattering analysis. Also, an important hydrogen content was found in the films. The relationship between optical, electrochemical, mechanical, structural and morphological behaviour of the above mentioned films will be reported and discussed in this work.

Theoretical and experimental results on Au-NiO and Au-CoO electrochromic composite films

Abstract This paper reports on the theoretical calculations and experimental results on the optical properties, between 400 and 1000 nm, of Au–NiO and Au–CoO composite films. The calculations were based on the Maxwell Garnett effective medium theory, with Au fill factors f varying from 0.0 to 0.05. The results for both media are very similar. The Au configuration in the insulating matrix was modeled to be isolated single spheres (ISS), single linear chain (SLC) and fcc cluster (FCC), as examples of selective absorption in these composite films. Variations in transmission and reflection can be obtained either by thickness variation, as well as from Au incorporation, as seen from theoretical and experimental results. Au–NiO films with different reflected colors (blue, green, yellow and orange-red) and same Au content were obtained by varying the pressure inside the sputtering deposition chamber. Green colored Au–CoO films with different Au content were deposited.

Lithium insertion and electrochromism in polycrystalline molybdenum oxide films

In this work, molybdenum oxide thin films were deposited by r.f. reactive sputtering of metallic molybdenum target in an Ar + O 2 atmosphere. Thin films with different compositions and crystal structures were obtained by varying the oxygen flow (o). All samples, with the exception of the MoO 2 film, showed an electrochromic behavior, due to the reversible Li + /e insertion or extraction process. The transmittance change (λ = 632.8 nm), for the best sample, was ∼ 70%. The film having the best optical behavior is mostly formed by the β-MoO 3 phase. The composition, optical and mechanical properties were determined and analyzed in as-grown and in Li intercalated films. The local order structure was analyzed by X-ray absorption spectroscopy measurements at the Mo L 2,3 -edges. The valence band was studied by Photoelectron Spectroscopy.

Crystal structure determination of mebendazole form A using high‐resolution synchrotron x‐ray powder diffraction data

The crystal structure determination of mebendazole form A, an anthelmintic drug, was performed for the first time by applying the DASH software program to synchrotron X-ray powder diffraction data, and supported by a satisfying Rietveld fit. This polymorph of mebendazole crystallizes in a triclinic (P1) space group, with unit-cell parameters a = 5.5044(2) A, b = 11.2872(2) A, c = 12.5276(5) A, alpha = 66.694(2) degrees, beta = 82.959(2) degrees, gamma = 78.443(2) degrees, V = 699.52(5) A(3), Z = 2, M = 295.293 g mol(-1), rho(calc) = 1.4021 g cm(-3), and rho(meas) = 1.3935(66) g cm(-3), which were obtained by means of the unit-cell formula weight and a picnometric measurement, respectively. The goodness-of-fit and R-factors were, respectively: chi(2) = 1.746, R(F)(2) = 1.69%, R(wp) = 5.72%, and R(p) = 4.37%. A weak nonclassical hydrogen bond involving the atoms N(3)-H(23)...O(11) may be responsible for the greater stability of the polymorphic form A of mebendazole due to the strongest electronegativity of nitrogen.

The effects of water molecules on the electronic and structural properties of peptide nanotubes

The self-assembly of short amino acid chains appears to be one of the most promising strategies for the fabrication of nanostructures. Their solubility in water and the possibility of chemical modification by targeting the amino or carboxyl terminus give peptide-based nanostructures several advantages over carbon nanotube nanostructures. However, because these systems are synthesized in aqueous solution, a deeper understanding is needed on the effects of water especially with respect to the electronic, structural and transport properties. In this work, the electronic properties of L-diphenylalanine nanotubes (FF-NTs) have been studied using the Self-Consistent Charge Density-Functional-based Tight-Binding method augmented with dispersion interaction. The presence of water molecules in the central hydrophilic channel and their interaction with the nanostructures are addressed. We demonstrate that the presence of water leads to significant changes in the electronic properties of these systems decreasing the band gap which can lead to an increase in the hopping probability and the conductivity.

Quillaja brasiliensis saponins are less toxic than Quil A and have similar properties when used as an adjuvant for a viral antigen preparation

In this study, a preparation of saponins (QB-90U) extracted from leaves of Quillaja brasiliensis collected in Uruguay was evaluated as a vaccine adjuvant by comparison with alum and the well known saponin-based adjuvant, Quil A. The haemolytic activity and cellular toxicity of the saponin preparations were also evaluated. QB-90U was only slightly haemolytic and showed a low cytotoxicity when compared to Quil A. The adjuvant properties of QB-90U were assayed by sub-cutaneous immunization of mice with a preparation of inactivated bovine herpesvirus 5 (BoHV-5) either with no adjuvant or adjuvanted with QB-90U, Quil A or alum. Serum levels of anti-BoHV-5 IgG, IgG1, IgG2a, IgG2b and also IgG3 were significantly increased by QB-90U and were of the same order as those elicited by Quil A. Furthermore, high titres of neutralizing antibodies were found to be present in the serum of immunized animals from both groups. The cellular response induced by QB-90U did also reproduce the one elicited by Quil A. In fact, a robust DTH response was observed in mice immunized with both saponin preparations; as well as increased splenocytes levels of Th1-type cytokines, namely IFN-γ and IL-2. Taken together, the above results confirm and extend our previous observation regarding the similarity of the responses elicited by Quil A and the saponin preparation from Q. brasiliensis (Fleck et al., 2006) and indicate that QB-90U is worth of further studies as a safe and potent vaccine adjuvant.

Electronic Perspective on the Electrochemistry of Prussian Blue Films

The derivative of the voltabsommetric scans, together with previous nano-electrogravimetric and X-ray diffraction results, allow different electrochemical processes to be distinguished during the Prussian blue (PB) voltammetric scan. Potassium, proton, and hydrated proton counterions involved in PB electrochemistry are related here to the electrochemical reactions of specific Fe sites. Potassium counterions show two different sites for their insertion: one located in the crystalline framework and another in ferrocyanide vacancies. From the monitoring of electroactive Fe sites, the covalent-exchange model is suggested as one of the first approaches to explain the origin of the PB magnetic ordering observed at room temperature during voltammetric scanning.

Novel Orally Active Analgesic and Anti-Inflammatory Cyclohexyl-N-Acylhydrazone Derivatives

The N-acylhydrazone (NAH) moiety is considered a privileged structure, being present in many compounds with diverse pharmacological activities. Among the activities attributed to NAH derivatives anti-inflammatory and analgesic ones are recurrent. As part of a research program aiming at the design of new analgesic and anti-inflammatory lead-candidates, a series of cyclohexyl-N-acylhydrazones 10–26 were structurally designed from molecular modification on the prototype LASSBio-294, representing a new class of cycloalkyl analogues. Compounds 10–26 and their conformationally restricted analogue 9 were synthetized and evaluated as analgesic and anti-inflammatory agents in classical pharmacologic protocols. The cyclohexyl-N-acylhydrazones 10–26 and the cyclohexenyl analogue 9 showed great anti-inflammatory and/or analgesic activities, but compound 13 stood out as a new prototype to treat acute and chronic painful states due to its important analgesic activity in a neuropathic pain model.

Morphological and structural evolution from akaganeite to hematite of nanorods monitored by ex situ synchrotron X-ray powder diffraction

Hematite (α-Fe2O3) is one of the most abundant minerals in nature and a thermodynamically-stable phase of iron oxide. One-dimensional (1D) hematite nanostructures have attracted, due to their fundamental characteristics such as excellent chemical stability in aqueous environments and low cost, considerable interest for a series of technical applications (as sensors, catalysis, lithium ion batteries and solar energy production and storage). Our study describes the phase evolution of iron oxide nanorods, from β-FeOOH to α-Fe2O3, with increasing temperatures of thermal treatment monitored by ex situ synchrotron X-ray powder diffraction data. These data used in conjunction with the Rietveld method allowed us to infer the phase concentration, elucidate the influence of temperature on the unit cell parameters and preferred growth orientation of the nanorods. Only the use of synchrotron radiation allowed us to precisely identify and quantify the presence of a minor Fe2O3 phase, which has never before been reported for those systems. Moreover, the formation of one-dimensional nanorods was accompanied by using scanning and transmission electron microscopies (SEM and TEM). At the highest temperatures of thermal treatments the hematite nanorods exhibited changes that varied from a quasi-perfect crystal up to polycrystalline rods (>500 °C). These findings were used for discussing and explaining recent results using this kind of nanostructure synthesized under hydrothermal conditions. Changes in the preferred orientation of the crystal faces of the rods could be responsible for a low photocatalytic performance reported by this strategy.