New Cu-Based Catalysts Supported on TiO2 Films for Ullmann SNAr-Type C-O Coupling Reactions

New routes for the preparation of highly active TiO2-supported Cu and CuZn catalysts have been developed for C-O coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt%. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, Cu-63 nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the C-O Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO2 catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64% on the Cu/nonporous TiO2 at 120 degrees C. The highest product yield of 84% was obtained on the Cu/mesoporous TiO2 at 140 degrees C, corresponding to an initial reaction rate of 104 mmol g(cat)(-1) s(-1). The activation energy on the Cu/mesoporous TiO2 catalyst was found to be (144 +/- 5) kJ mol(-1), which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123 +/- 3 kJ mol(-1)) and almost twice the value observed over the catalysts deposited onto the non-porous TiO2 support (75 +/- 2 kJ mol(-1)).

Photobactericidal effects of TiO 2 thin films at low temperatures - A preliminary study

The efficacy of TiO ₂ photocatalysis for the destruction of pathogenic bacteria has been demonstrated by a number of groups over the past two decades. Pathogenic bacteria represent a significant hazard for the food and drink industry. Current practices in this industry dictate that rigorous sanitizing regimes must be regularly implemented resulting in lost production time. The incorporation of a TiO ₂ antibacterial surface coating in this setting would be highly desirable. In this paper we report a preliminary study of the efficacy of a TiO ₂ coating, doped with the lanthanide, neodymium, at low temperature conditions such as those utilised in the food and drink sector. The rapid destruction of Staphylococcus aureus, a common foodborne pathogen, was observed using TiO ₂ films coated to glass and steel substrates. 

Híbridos orgânicos-inorgânicos para aplicações de baixo custo em óptica integrada

O objectivo desta tese é a utilização de materiais híbridos orgânicos-inorgânicos, designados por di-ureiasis modificados pela adição de tetra-propóxido de zircónio (Zr(i-OPr)4) estabilizado com ácido metacrílico (CH2=C(CH3)COOH), obtidos pela via sol-gel, para aplicações em dispositivos ópticos integrados de baixo custo. A estrutura local dos di-ureiasis com diferentes concentrações de propóxido de zircónio (20 a 80 % mol) foi estudada por difracção de raios-X, espalhamento de raios X a baixos ângulos, microscopia de força atómica, ressonância magnética nuclear dos núcleos dos átomos de 29Si e 13C, espectroscopia no infravermelho por transformada de Fourier, espectroscopia de Raman por transformada de Fourier e termogravimetria. A influência dos parâmetros de síntese, concentração de tetra propóxido de zircónio e rácio tetra propóxido de zircónio: ácido metacrilico na estrutura e propriedades das amostras em monólito e filmes finos (depositados pela técnica de deposição por rotação do substrato) foram avaliadas, permitindo obter amostras transparentes, fotopolimerizáveis e estáveis termicamente até aos 100 ºC. Foram determinadas as propriedades dos guias planares em substratos de vidro borosilicato e silício oxidado (1

Synchrotron structural characterization of electrochemically synthesized hexacyanoferrates containing K(+): A revisited analysis of electrochemical redox

The presumably soluble KFe(+3)[Fe(2+)(CN)(6)] structure of electrochemically synthesized hexacyanoferrate materials (Prussian Blue) containing K(+) ions was determined for the first time in this study. Prior to drawing conclusions from a structural analysis, the main goal was to make a precise analysis of the inferred soluble structure, that is, KFe(+3) [Fe(2+)(CN)(6)], which is frequently referred to in the literature as the final stable electrochemically synthesized structure. Indeed, a successful X-ray powder diffraction experiment using X-ray synchrotron radiation was made of a powder placed in a 0.5 mm diameter borosilicate glass capillary, which was obtained by removing sixty 90 nm thin films from the substrates on which they were prepared. However, the conclusions were highly unexpected, because the structure showed that the [Fe(CN)61 group was absent from similar to 25% of the structure, invalidating the previously presumed soluble KFe(+3)[Fe(2+)(CN)(6)] structure. This information led to the conclusion that the real structure of Prussian Blue electrochemically synthesized after the stabilization process is Fe(4)[Fe(CN)(6)](3)center dot mH(2)O containing a certain fraction of inserted K(+) ions. In fact, based on an electrogravimetric analysis (Gimenez-Romero et al., J. Phys. Chem. B 2006, 110, 2715 and 19352) complemented by the Fourier maps. it is possible to affirm that the K(+) was part of the water crystalline substructure. Therefore, the interplay mechanism was reexamined considering more precisely the role played by the water crystalline substructure and the K+ alkali metal ion. As a final conclusion, it is proposed that the most precise way to represent the structure of electrochemically synthesized and stabilized hexacyanoferrate materials is Fe(4)(3+) Fe(2+)(CN)(6)](3)center dot[K(h)(+)center dot OH(h)(-)center dot mH(2)O]. The importance of this result is that the widespread use of the terms soluble and insoluble in the electrochemical literature could be reconsidered. Indeed, only one type of structure is insoluble, and that is Fe(4)[Fe(CN)(6)](3)center dot mH(2)O hence, the use of the terms soluble and insoluble is inappropriate from a structural point of view. The result of the presence of the [Fe(CN)61 vacancy a, roup is that the water Substructure cannot be ignored in the ionic interplay mechanism which controls the intercalation and redox process, as was previously confirmed by electrogravimetric analyses (Gimenez-Romero et al., J. Phys. Chem. B 2006, 110, 2715 Garcia-Jareno et al., Electrochim. Acta 1998, 44, 395: Kulesza, Inorg. Chem. 1990, 29, 2395).

Titania-based organic-inorganic hybrid planar waveguides

Eu3+ -doped titania-silica planar waveguides were prepared from tetraethylorthotitanate (TEOT) and modified silane 3-amino-propyltriethoxysilane (APTS). Films were deposited on borosilicate glass substrates by a dip-coating technique. The refractive index, the thickness and the total attenuation coefficient of the waveguides were measured at 632.8 and 1550 nm by prism coupling technique. Starting from pure titania films, the addition of modified silane leads to a decrease in the refractive index and an increase in thickness. Squared electric field simulation has shown that the light confinement in the waveguide increases with the silane content of the so]. Emission spectra present a broad emission band due to the modified silane and EU emission transitions arising mainly from the D-5(0) level to the F-7(J) (J = 0-4) manifolds. The dependence of transition intensities and excited state lifetimes on the initial composition and also on the heat treatment performed was interpreted in terms of structural changes occurring during the preparation process. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Photodesorption and electron trapping in n-type SnO2 thin films grown by dip-coating technique

Thin films of undoped and Sb-doped (2 atg%) SnO2 have been prepared by sol-gel dip-coating technique on borosilicate glasses. Variation of photoconductivity excitation with wavelength and optical absorption indicate indirect bandgap transition with energy of ≅ 3.5 eV. Conductance as function of temperature indicates two levels of capture with 39 and 81 meV as activation energies, which may be related to an Sb donor and oxygen vacancy respectively. Electron trapping by these levels are practically destroyed by UV photoexcitation (305 nm) and heating in vacuum to 200°C. Gas analysis using a mass spectrometer indicates an oxygen related level, which may not be desorbed in the simpler O2 form.

Deposição e caracterização de filmes finos de GaAs e 'Al IND. 2''O IND. 3' para potencial utilizado em transistores

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Construção de um interferômetro de Bath para análise do comportamento da superfície de vidros usados na confecção de espelhos côncavos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

High-throughput sugarcane leaf analysis using a low cost closed-vessel conductively heated digestion system and inductively coupled plasma optical emission spectroscopy

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

Nitric Oxide in the Exhaled Breath Condensate of Healthy Volunteers Collected With a Reusable Device

Background: The analysis of exhaled breath condensate (EBC) is a non-invasive technique that enables the determination of several volatile and nonvolatile substances produced in the respiratory tract, whose measurement may be useful for the diagnosis and monitoring of several respiratory diseases. Objective: The aim of this study was to produce a low-cost reusable device in order to sample exhaled breath condensate in healthy adult volunteers, and to determine the concentration of nitric oxide in the sample collected. Material and methods: The apparatus was made with a U-shaped tube of borosilicate glass. The tube was placed in a container with ice, and unidirectional respiratory valves were fitted to the distal end. Afterwards, nitric oxide was measured in the exhaled breath condensate (EBC) by chemiluminescence. Results: The total cost of the device was $120.20. EBC samples were obtained from 116 volunteers of both sexes, aged between 20 and 70. The mean volume of exhaled breath condensate collected during 10 minutes was 1.0 +/- 0.6 mL, and the mean level of nitric oxide was 12.99 +/- 14.38 mu M (median 8.72 mu M). There was no correlation between the nitric oxide levels in the exhaled breath condensate and age or gender. Conclusion: We demonstrate that it is possible to fabricate a low-cost, efficient, reusable device in order to collect and determine nitric oxide levels in EBC. We have identified no correlation between the nitric oxide levels present in the EBC obtained with this method with either age or sex. (C) 2011 SEPAR. Published by Elsevier Espana, S.L. All rights reserved.

In-situ and Ex-situ characterization of III-V semiconductor materials and solar cells upon 10 MEV proton irradiation

In this work we present the results and analysis of a 10 MeV proton irradiation experiment performed on III-V semiconductor materials and solar cells. A set of representative devices including lattice-matched InGaP/GaInAs/Ge triple junction solar cells and single junction GaAs and InGaP component solar cells and a Ge diode were irradiated for different doses. The devices were studied in-situ before and after each exposure at dark and 1 sun AM0 illumination conditions, using a solar simulator connected to the irradiation chamber through a borosilicate glass window. Ex-situ characterization techniques included dark and 1 sun AM0 illumination I-V measurements. Furthermore, numerical simulation of the devices using D-AMPS-1D code together with calculations based on the TRIM software were performed in order to gain physical insight on the experimental results. The experiment also included the proton irradiation of an unprocessed Ge solar cell structure as well as the irradiation of a bare Ge(100) substrate. Ex-situ material characterization, after radioactive deactivation of the samples, includes Raman spectroscopy and spectral reflectivity.

Low-loss waveguides fabricated by femtosecond chirped-pulse oscillator

Recent results on direct femtosecond inscription of straight low-loss waveguides in borosilicate glass are presented. We also demonstrate lowest ever losses in curvilinear waveguides, which we use as main building blocks for integrated photonics circuits. Low-loss waveguides are of great importance to a variety of applications of integrated optics. We report on recent results of direct femtosecond fabrication of smooth low-loss waveguides in standard optical glass by means of femtosecond chirped-pulse oscillator only (Scientific XL, Femtolasers), operating at the repetition rate of 11 MHz, at the wavelength of 800 nm, with FWHM pulse duration of about 50 fs, and a spectral widths of 30 nm. The pulse energy on target was up to 70 nJ. In transverse inscription geometry, we inscribed waveguides at the depth from 10 to 300 micrometers beneath the surface in the samples of 50 x 50 x 1 mm dimensions made of pure BK7 borosilicate glass. The translation of the samples accomplished by 2D air-bearing stage (Aerotech) with sub-micrometer precision at a speed of up to 100 mm per second (hardware limit). Third direction of translation (Z-, along the inscribing beam or perpendicular to sample plane) allows truly 3D structures to be fabricated. The waveguides were characterized in terms of induced refractive index contrast, their dimensions and cross-sections, mode-field profiles, total insertion losses at both 633 nm and 1550 nm. There was almost no dependence on polarization for the laser inscription. The experimental conditions – depth, laser polarization, pulse energy, translation speed and others, were optimized for minimum insertion losses when coupled to a standard optical fibre SMF-28. We found coincidence of our optimal inscription conditions with recently published by other groups [1, 3] despite significant difference in practically all experimental parameters. Using optimum regime for straight waveguides fabrication, we inscribed a set of curvilinear tracks, which were arranged in a way to ensure the same propagation length (and thus losses) and coupling conditions, while radii of curvature varied from 3 to 10 mm. This allowed us to measure bend-losses – they less than or about 1 dB/cm at R=10 mm radius of curvature. We also demonstrate a possibility to fabricate periodical perturbations of the refractive index in such waveguides with the periods using the same set-up. We demonstrated periods of about 520 nm, which allowed us to fabricate wavelength-selective devices using the same set-up. This diversity as well as very short time for inscription (the optimum translation speed was found to be 40 mm/sec) makes our approach attractive for industrial applications, for example, in next generation high-speed telecom networks.

Low-loss waveguides fabricated by femtosecond chirped-pulse oscillator

Recent results on direct femtosecond inscription of straight low-loss waveguides in borosilicate glass are presented. We also demonstrate lowest ever losses in curvilinear waveguides, which we use as main building blocks for integrated photonics circuits. Low-loss waveguides are of great importance to a variety of applications of integrated optics. We report on recent results of direct femtosecond fabrication of smooth low-loss waveguides in standard optical glass by means of femtosecond chirped-pulse oscillator only (Scientific XL, Femtolasers), operating at the repetition rate of 11 MHz, at the wavelength of 800 nm, with FWHM pulse duration of about 50 fs, and a spectral widths of 30 nm. The pulse energy on target was up to 70 nJ. In transverse inscription geometry, we inscribed waveguides at the depth from 10 to 300 micrometers beneath the surface in the samples of 50 x 50 x 1 mm dimensions made of pure BK7 borosilicate glass. The translation of the samples accomplished by 2D air-bearing stage (Aerotech) with sub-micrometer precision at a speed of up to 100 mm per second (hardware limit). Third direction of translation (Z-, along the inscribing beam or perpendicular to sample plane) allows truly 3D structures to be fabricated. The waveguides were characterized in terms of induced refractive index contrast, their dimensions and cross-sections, mode-field profiles, total insertion losses at both 633 nm and 1550 nm. There was almost no dependence on polarization for the laser inscription. The experimental conditions – depth, laser polarization, pulse energy, translation speed and others, were optimized for minimum insertion losses when coupled to a standard optical fibre SMF-28. We found coincidence of our optimal inscription conditions with recently published by other groups [1, 3] despite significant difference in practically all experimental parameters. Using optimum regime for straight waveguides fabrication, we inscribed a set of curvilinear tracks, which were arranged in a way to ensure the same propagation length (and thus losses) and coupling conditions, while radii of curvature varied from 3 to 10 mm. This allowed us to measure bend-losses – they less than or about 1 dB/cm at R=10 mm radius of curvature. We also demonstrate a possibility to fabricate periodical perturbations of the refractive index in such waveguides with the periods using the same set-up. We demonstrated periods of about 520 nm, which allowed us to fabricate wavelength-selective devices using the same set-up. This diversity as well as very short time for inscription (the optimum translation speed was found to be 40 mm/sec) makes our approach attractive for industrial applications, for example, in next generation high-speed telecom networks.

Uniquely Identifiable Tamper-Evident Device Using Coupling between Subwavelength Gratings

Reliability and sensitive information protection are critical aspects of integrated circuits. A novel technique using near-field evanescent wave coupling from two subwavelength gratings (SWGs), with the input laser source delivered through an optical fiber is presented for tamper evidence of electronic components. The first grating of the pair of coupled subwavelength gratings (CSWGs) was milled directly on the output facet of the silica fiber using focused ion beam (FIB) etching. The second grating was patterned using e-beam lithography and etched into a glass substrate using reactive ion etching (RIE). The slightest intrusion attempt would separate the CSWGs and eliminate near-field coupling between the gratings. Tampering, therefore, would become evident. Computer simulations guided the design for optimal operation of the security solution. The physical dimensions of the SWGs, i.e. period and thickness, were optimized, for a 650 nm illuminating wavelength. The optimal dimensions resulted in a 560 nm grating period for the first grating etched in the silica optical fiber and 420 nm for the second grating etched in borosilicate glass. The incident light beam had a half-width at half-maximum (HWHM) of at least 7 µm to allow discernible higher transmission orders, and a HWHM of 28 µm for minimum noise. The minimum number of individual grating lines present on the optical fiber facet was identified as 15 lines. Grating rotation due to the cylindrical geometry of the fiber resulted in a rotation of the far-field pattern, corresponding to the rotation angle of moiré fringes. With the goal of later adding authentication to tamper evidence, the concept of CSWGs signature was also modeled by introducing random and planned variations in the glass grating. The fiber was placed on a stage supported by a nanomanipulator, which permitted three-dimensional displacement while maintaining the fiber tip normal to the surface of the glass substrate. A 650 nm diode laser was fixed to a translation mount that transmitted the light source through the optical fiber, and the output intensity was measured using a silicon photodiode. The evanescent wave coupling output results for the CSWGs were measured and compared to the simulation results.