Cobalt complexes with pyrazole ligands as catalyst precursors for the peroxidative oxidation of cyclohexane: Z-ray absorption spectroscopy studies and biological applications

[CoCl(-Cl)(Hpz(Ph))(3)](2) (1) and [CoCl2(Hpz(Ph))(4)] (2) were obtained by reaction of CoCl2 with HC(pz(Ph))(3) and Hpz(Ph), respectively (Hpz(Ph)=3-phenylpyrazole). The compounds were isolated as air-stable solids and fully characterized by IR and far-IR spectroscopy, MS(ESI+/-), elemental analysis, cyclic voltammetry (CV), controlled potential electrolysis, and single-crystal X-ray diffraction. Electrochemical studies showed that 1 and 2 undergo single-electron irreversible (CoCoIII)-Co-II oxidations and (CoCoI)-Co-II reductions at potentials measured by CV, which also allowed, in the case of dinuclear complex 1, the detection of electronic communication between the Co centers through the chloride bridging ligands. The electrochemical behavior of models of 1 and 2 were also investigated by density functional theory (DFT) methods, which indicated that the vertical oxidation of 1 and 2 (that before structural relaxation) affects mostly the chloride and pyrazolyl ligands, whereas adiabatic oxidation (that after the geometry relaxation) and reduction are mostly metal centered. Compounds 1 and 2 and, for comparative purposes, other related scorpionate and pyrazole cobalt complexes, exhibit catalytic activity for the peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone under mild conditions (room temperature, aqueous H2O2). Insitu X-ray absorption spectroscopy studies indicated that the species derived from complexes 1 and 2 during the oxidation of cyclohexane (i.e., Ox-1 and Ox-2, respectively) are analogous and contain a Co-III site. Complex 2 showed low invitro cytotoxicity toward the HCT116 colorectal carcinoma and MCF7 breast adenocarcinoma cell lines.

Reversible Photorheology in Solutions of Cetyltrimethylammonium Bromide, Salicylic Acid, and trans-2,4,4 '-Trihydroxychalcone

We show photorheology in aqueous solutions of weakly entangled wormlike micelles prepared with cetyltrimethylammonium bromide (CTAB), salicylic acid (HSal), and dilute amounts of the photochromic multistate compound trans-2,4,4'-trihydroxychalcone (Ct). Different chemical species of Ct are associated with different colorations and propensities to reside within or outside CTAB micelles. A light-induced transfer between the intra- and intermicellar space is used to alter the mean length of wormlike micelles and hence the rheological properties of the fluid, studied in steady-state shear Bow and in dynamic rheological measurements. Light-induced changes of fluid rheology are reversible by a the relaxation process. at relaxation rates which depend on pH and which are consistent with photochromic reversion rates measured by UV-vis absorption spectroscopy. Parameterizing viscoelostic rheological states by their effective relaxation time tau(c) and corresponding response modulus G(c), we find the light and dark states of the system to fall onto a characteristic state curve defined by comparable experiments conducted without photosensitive components. These reference experiments were prepared with the same concentration of CTAB, but different concentrations of HSal or sodium salicylote (NaSal), and tested at different temperatures.

Photodiode with nanocrystalline Si/amorphous Si absorber bilayer

This letter reports a near-ultraviolet/visible/near-infrared n(+)-n-i-delta(i)-p photodiode with an absorber comprising a nanocrystalline silicon n layer and a hydrogenated amorphous silicon i layer. Device modeling reveals that the dominant source of reverse dark current is deep defect states in the n layer, and its magnitude is controlled by the i layer thickness. The photodiode with the 900/400 nm thick n-i layers exhibits a reverse dark current density of 3nA/cm(2) at -1V. Donor concentration and diffusion length of holes in the n layer are estimated from the capacitance-voltage characteristics and from the bias dependence of long-wavelength response, respectively. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3660725]

Homogeneous and heterogenised new gold C-scorpionate complexes as catalysts for cyclohexane oxidation

Gold(III) complexes of type [AuCl2{eta(2)-RC(R'pz)(3)}]Cl [R = R' = H (1), R = CH2OH, R' = H (2) and R = H, R' = 3,5-Me-2(3), pz = pyrazol-1-yl] were supported on carbon materials (activated carbon, carbon xerogel and carbon nanotubes) and used for the oxidation of cyclohexane to cyclohexanol and cyclohexanone, with aqueous H2O2, under mild conditions.

Serum trace elements in dysphagic gastrostomy candidates before endoscopic gastrostomy for long term enteral feeding

Background & aims - Patients who underwent endoscopic gastrostomy (PEG) present protein-energy malnutrition, but little is known about Trace Elements (TE), Zinc (Zn), Copper (Cu), Selenium (Se), Iron (Fe), Chromium (Cr). Our aim was the evaluation of serum TE in patients who underwent PEG and its relationship with serum proteins, BMI and nature of underlying disorder. Methods - A prospective observational study was performed collecting: patient's age, gender, underlying disorder, NRS-2002, BMI, serum albumin, transferrin and TE concentration. We used ferrozine colorimetric method for Fe; Inductively Coupled Plasma-Atomic Emission Spectroscopy for Zn/Cu; Furnace Atomic Absorption Spectroscopy for Se/Cr. The patients were divided into head and neck cancer (HNC) and neurological dysphagia (ND). Results - 146 patients (89 males), 21–95 years: HNC-56; ND-90. Low BMI in 78. Low values mostly for Zn (n = 122) and Fe (n = 69), but less for Se (n = 31), Cu (n = 16), Cr (n = 7); low albumin in 77, low transferrin in 94 and 66 with both proteins low. Significant differences between the groups of underlying disease only for Zn (t140.326 = −2,642, p < 0.01) and a correlation between proteins and TE respectively albumin and Zn (r = 0.197, p = 0.025), and albumin and Fe (r = 0.415, p = 0.000). Conclusions - When gastrostomy was performed, patients display low serum TE namely Zn, but also Fe, less striking regarding others TE. It was related with prolonged fasting, whatever the underlying disease. Low proteins were associated with low TE. Teams taking care of PEG-patients should use Zn supplementation and include other TE evaluation as part of the nutritional assessment of PEG candidates.

Catalytic activity of a benzoyl hydrazone based dimeric dicopper(II) complex in catechol and alcohol oxidation reactions

The benzoyl hydrazone based dimeric dicopper(II) complex [Cu2(R)(CH3O)(NO3)]2(CH3O)2 (R-Cu2+), recently reported by us, catalyzes the aerobic oxidation of catechols (catechol (S1), 3,5- itertiarybutylcatechol (S2) and 3-nitrocatechol (S3)) to the corresponding quinones (catecholase like activity), as shown by UV–Vis absorption spectroscopy in methanol/HEPES buffer (pH 8.2) medium at 25 C. The highest activity is observed for the substituted catechol (S2) with the electron donor tertiary butyl group, resulting in a turnover frequency (TOF) value of 1.13 103 h1. The complex R-Cu2+ also exhibits a good catalytic activity in the oxidation (without added solvent) of 1-phenylethanol to acetophenone by But OOH under low power (10 W) microwave (MW) irradiation. 2014 Elsevier B.V. All rights reserved.

Selenium in dysphagic patients who underwent endoscopic gastrostomy for long term enteral feeding

Background and aims - Endoscopic gastrostomy (PEG) patients usually present protein-energy malnutrition, but little is known about selenium deficiency. We aimed to assess serum selenium evolution when patients underwent PEG, after 4 and 12 weeks. We also evaluated the evolution of albumin, transferrin and Body Mass Index and the influence of the nature of the underlying disease. Methods - A blood sample was obtained before PEG (T0), after 4 (T1) and 12 (T3) weeks. Selenium was assayed using GFAAS (Furnace Atomic Absorption Spectroscopy). The PEG patients were fed through homemade meals. Patients were studied as a whole and divided into two groups: head and neck cancer (HNC) and neurological dysphagia (ND). Results - We assessed 146 patients (89 males), between 21-95 years old: HNC-56; ND-90. Normal values of selenium in 79% (n=115); low albumin in 77, low transferrin in 94, low values for both serum proteins in 66. Low BMI in 78. Selenium has slow evolution, with most patients still displaying normal Selenium at T3 (82%). Serum protein levels increase from T0 to T3, most patients reaching normal values. The nature of the underlying disease is associated with serum proteins but not with selenium. Conclusions - Low serum selenium is uncommon when PEG is performed, after 4 and 12 weeks of enteral feeding and cannot be related with serum proteins levels or dysphagia cause. Enteral nutrition using customized homemade kitchen meals is satisfactory to prevent or correct Selenium deficiency in the majority of PEG patients.

Optical demultiplexer device operating in the visible spectrum

In this paper, we present results on the use of multilayered a-SiC:H heterostructures as a device for wavelength-division demultiplexing of optical signals. These devices are useful in optical communications applications that use the wavelength division multiplexing technique to encode multiple signals into the same transmission medium. The device is composed of two stacked p-i-n photodiodes, both optimized for the selective collection of photo generated carriers. Band gap engineering was used to adjust the photogeneration and recombination rate profiles of the intrinsic absorber regions of each photodiode to short and long wavelength absorption in the visible spectrum. The photocurrent signal using different input optical channels was analyzed at reverse and forward bias and under steady state illumination. A demux algorithm based on the voltage controlled sensitivity of the device was proposed and tested. An electrical model of the WDM device is presented and supported by the solution of the respective circuit equations.

Structural characterization and immunogenicity in wild-type and immune tolerant mice of degraded recombinant human interferon Alpha2b

Purpose: This study was conducted to study the influence of protein structure on the immunogenicity in wild-type and immune tolerant mice of well-characterized degradation products of recombinant human interferon alpha2b (rhIFNα2b). Methods: RhIFNα2b was degraded by metal-catalyzed oxidation (M), cross-linking with glutaraldehyde (G), oxidation with hydrogen peroxide (H), and incubation in a boiling water bath (B). The products were characterized with UV absorption, circular dichroism and fluorescence spectroscopy, gel permeation chromatography, reverse-phase high-pressure liquid chromatography, sodium dodecyl sulfate polyacrylamide gel electrophoresis, Western blotting, and mass spectrometry. The immunogenicity of the products was evaluated in wild-type mice and in transgenic mice immune tolerant for hIFNα2. Serum antibodies were detected by enzyme-linked immunosorbent assay or surface plasmon resonance. Results: M-rhIFNα2b contained covalently aggregated rhIFNα2b with three methionines partly oxidized to methionine sulfoxides. G-rhIFNα2b contained covalent aggregates and did not show changes in secondary structure. H-rhIFNα2b was only chemically changed with four partly oxidized methionines. B-rhIFNα2b was largely unfolded and heavily aggregated. Nontreated (N) rhIFNα2b was immunogenic in the wild-type mice but not in the transgenic mice, showing that the latter were immune tolerant for rhIFNα2b. The anti-rhIFNα2b antibody levels in the wild-type mice depended on the degradation product: M-rhIFNα2b > H-rhIFNα2b ∼ N-rhIFNα2b ≫ B-rhIFNα2b; G-rhIFNα2b did not induce anti-rhIFNα2b antibodies. In the transgenic mice, only M-rhIFNα2b could break the immune tolerance. Conclusions: RhIFNα2b immunogenicity is related to its structural integrity. Moreover, the immunogenicity of aggregated rhIFNα2b depends on the structure and orientation of the constituent protein molecules and/or on the aggregate size.

Métodos "verdes" de produção de nanomateriais que promovem nanotecnologias sustentáveis

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Química

Visible range plasmonic effect produced by aluminium nanoparticles embedded in amorphous silicon

We present results, obtained by means of an analytic study and a numerical simulation, about the resonant condition necessary to produce a Localized Surface Plasmonic Resonance (LSPR) effect at the surface of metal nanospheres embedded in an amorphous silicon matrix. The study is based on a Lorentz dispersive model for a-Si:H permittivity and a Drude model for the metals. Considering the absorption spectra of a-Si:H, the best choice for the metal nanoparticles appears to be aluminium, indium or magnesium. No difference has been observed when considering a-SiC:H. Finite-difference time-domain (FDTD) simulation of an Al nanosphere embedded into an amorphous silicon matrix shows an increased scattering radius and the presence of LSPR induced by the metal/semiconductor interaction under green light (560 nm) illumination. Further results include the effect of the nanoparticles shape (nano-ellipsoids) in controlling the wavelength suitable to produce LSPR. It has been shown that is possible to produce LSPR in the red part of the visible spectrum (the most critical for a-Si:H solar cells applications in terms of light absorption enhancement) with aluminium nano-ellipsoids. As an additional results we may conclude that the double Lorentz-Lorenz model for the optical functions of a-Si:H is numerically stable in 3D simulations and can be used safely in the FDTD algorithm. A further simulation study is directed to determine an optimal spatial distribution of Al nanoparticles, with variable shapes, capable to enhance light absorption in the red part of the visible spectrum, exploiting light trapping and plasmonic effects. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.