Optical properties of polydisperse submicrometer aggregates of sulfur-containing zinc oxide consisting of spherical nanocrystallites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Spherical microparticles formed by agglomerated spherical nanocrystals of sulfur-containing ZnO were prepared by homogeneous precipitation of ZnS followed by thermal treatment under an air atmosphere. The samples were characterized by thermogravimetry (TG), X-ray diffraction (XRD) and Raman, UV-Vis diffuse reflectance (DRS) and photoluminescence (PL) spectroscopies. The particle morphologies were observed by transmission and scanning electron microscopies (TEM and SEM), showing that spherical microparticles of sulfur-containing ZnO are formed by aggregates of 25 nm spherical nanocrystallites. XRD and TEM results show the presence of ZnO and ZnS phases for short time thermal treatments and only the ZnO wurtzite phase for longer thermal treatments. The presence of Zn-S bonds in sulfur-containing zinc oxide decreases the ZnO band gap energy as verified by DRS, probably due to a valence band offset.354902908Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Viral Inhibition Mechanism Mediated By Surface-modified Silica Nanoparticles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Vaccines and therapies are not available for several diseases caused by viruses, thus viral infections result in morbidity and mortality of millions of people every year. Nanoparticles are considered to be potentially effective in inhibiting viral infections. However, critical issues related to their use include their toxicity and their mechanisms of antiviral action, which are not yet completely elucidated. To tackle these problems, we synthesized silica nanoparticles with distinct surface properties and evaluated their biocompatibility and antiviral efficacy. We show that nanoparticles exhibited no significant toxicity to mammalian cells, while declines up to 50% in the viral transduction ability of two distinct recombinant viruses were observed. We designed experiments to address the mechanism of antiviral action of our nanoparticles and found that their hydrophobic/hydrophilic characters play a crucial role. Our results reveal that the use of functionalized silica particles is a promising approach for controlling viral infection and offer promising strategies for viral control.81656416572FAPESP [2014/22322-2, 2012/05481-4, 2013/12190-9]LNLSFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Morphology and phase modifications of MoO3 obtained by metallo-organic decomposition processes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Molybdenum oxide samples were prepared using different temperatures and atmospheric conditions by metallo-organic decomposition processes and were characterized by XRD, SEM and DRS UV/Vis and Raman spectroscopies. Variation in the synthesis conditions resulted in solids with different morphologies and oxygen vacancy concentrations. Intense characteristic Raman bands of crystalline orthorhombic alpha-MoO3, occurring at 992 cm(-1) and 820 cm(-1), are observed and their shifts can be related to the differences in the structure of the solids obtained. The sample obtained under nitrogen flow at 1073 K is a phase mixture of orthorhombic alpha-MoO3 and monoclinic beta-MoO3. The characterization results suggest that the molybdenum oxide samples are non-stoichiometric and are described as MoOx with x < 2.94. Variations in the reaction conditions make it possible to tune the number of oxygen defects and the band gap of the final material. (C) 2010 Elsevier Ltd. All rights reserved.451117071712Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Catalytic activity and stability of a chromium containing silicate in liquid phase cyclohexane oxidation

A chromium containing silicate has been prepared by an acid-catalyzed sol-gel process. The material was characterized by FTIR, W-VIS and EPR spectroscopy as well as TPR, XRD and XRF analyses. The silicate is an efficient catalyst for the oxidation of cyclohexane with tert-butyl hydroperoxide. Leaching studies showed that catalysis is at least in part due to traces of Cr leached into the homogeneous phase. Weakly bound Cr species can be removed by soxhlet extraction, yielding a catalyst which is remarkably leaching resistant. The catalyst can be used at least four times without detectable loss of metal. (C) 2001 Elsevier Science B.V. All rights reserved.1714167125125

The chemical reactivity of some terpenes investigated by alumina catalyzed epoxidation with hydrogen peroxide and by DFT calculations

The selectivity of the alumina catalyzed epoxidation of (S)-limonene, citronelal, citral, citronelol and (1S)-(alpha)-pinene with aqueous 70 wt% and anhydrous 24 wt% hydrogen peroxide is described. DFT molecular orbital calculations were used aiming at a better understanding of the reactivity of these terpenes. The more nucleophilic carbon-carbon double bond, which has a higher molecular orbital energy, is preferentially epoxidized (site-selectivity). Furthermore, a preference for epoxidation in competition with other possible reactions is observed for citronelal, citral, citronelol and (IS)-(alpha)-pinene (chemo-selectivity). Nonetheless, we were not able to achieve a stereo-selective epoxidation of the terpenes using alumina and hydrogen peroxide. (c) 2006 Elsevier B.V. All rights reserved.2524167118619

Annealing temperature effects on sol-gel nanostructured mesoporous TiO2/SiO2 and its photocatalytic activity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Mesoporous TiO2/SiO2 (5 wt% TiO2) was synthesized by the sol-gel method and thermally treated up to 1273 K. The materials obtained were characterized by N-2 adsorption/desorption isotherms, XRD, TEM, Raman and UV-vis diffuse reflectance spectroscopies. The results indicate the presence of thermally stable anatase TiO2 nanoparticles (similar to 20 nm) highly dispersed in the SiO2 matrix, with no evidence of particle growth for materials treated up to 1073 K. Important features related to the number of structural defects and short-distance ordering of TiO2 nanoparticles were found and they have a direct relationship with the photocatalytic performance of the materials. Higher photocatalytic activity toward methylene blue decolourisation was observed for solids annealed at higher temperatures. (C) 2010 Elsevier B.V. All rights reserved.12641671188194Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

TiO2- and CeO2-Based Biphasic Core-Shell Nanoparticles with Tunable Core Sizes and Shell Thicknesses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)A layer-by-layer methodology was used for synthesizing CeO2/TiO2 and TiO2/CeO2 core shell nanoparticles supported in Vycor glass pores. The layers were deposited by cerium- or titanium-based metalloorganic precursor decomposition. Sequential depositions promoted linear mass increases of the Vycor pieces and a linear decrease of both total pore size and total surface area, confirmed by N-2 adsorption-desorption isotherms. Alternation in the metalloorganic precursors used results in the formation of spherelike nanoparticles (as observed by HRTEM) with core shell architecture. Raman spectroscopy data showed that CeO2 is crystallized in the fluorite structure and TiO2 in the anatase phase. Shifts in the frequency and changes in line width of TiO2 E-g and CeO2 T-2g Raman bands were used for monitoring changes in core size and shell thickness based on the quantum size effect and on the phonon confinement theory. Our results show that nanoparticle core sizes and the shell thicknesses can be tuned by changing the number of depositions used in the synthesis process.115211038010387Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Size controlled synthesis of highly dispersed anatase/rutile nanoparticles with photocatalytic activity toward salicylic acid degradation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)TiO2 nanocrystals supported in SBA-15 pores were prepared by a simple route of successive cycles of impregnation of SBA-15 with titanium(IV) di-(n-propoxy)-di-(2-ethylhexanoate) followed by thermal treatment. Anatase and rutile phases were identified by XRD in the materials obtained after cycles 1, 3, 5, 7 and 10. Raman scattering combined with XRD and TEM shows that titania is in a nanometric regime. Increases in the size of the titania nanocrystals, as well as increases in the TiO2 content in the final material (XRF), occur after successive cycles. SAXS and N-2 sorption indicate that the nanocrystals are formed inside the SBA-15 mesopores, which remain unblocked even after 10 cycles. UV-Vis (DRS) spectroscopy indicates important changes in electronic properties. The ability of SBA-15- supported titania nanocrystals to photodegrade salicylic acid was tested. There is a clear relation between the TiO2 nanoparticle size and the photocatalytic activity. Among all samples tested, the best result was obtained for the materials with the highest band-gaps and with the smallest sized titania.21253905397Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Synthesis and structural characterization of nanometric ceria highly dispersed in SBA-15 with oxygen exchange capacity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Nanometric ceria-decorated SBA-15 was prepared using a route involving the impregnation of SBA-15 pores by a solution of cerium(III) 2-ethylhexanoate, followed by its thermal decomposition. According to XRF analysis, the number of successive impregnation-decomposition cycles (IDC) allows control of the CeO(2)/SiO(2) ratio in the final material, and also the tailoring of the nanoparticle size of the fluorite CeO(2) nanoparticles supported in the SBA-15, as confirmed by XRD, Raman and UV-Vis spectroscopies. The mean pore size of the SBA-15 decreases with successive IDC, as observed by N(2) adsorption-desorption, suggesting that CeO(2) nanoparticles are located inside the SBA-15 mesopores, as confirmed by TEM and HRTEM analyses. The degree of oxygen storage capacity (OSC) was measured by the number of hydrogen uptake from the temperature programmed reduction (H(2)-TPR). It was found that the value of hydrogen uptake of SBA-15 submitted to one IDC corresponds to 3344 mmol of O(2) per gram of CeO(2), whereas those of SBA-15 submitted to five and ten IDC were 1324 and 2769 mu mol of O(2) per gram of CeO(2), respectively.21391567815685Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)electron microscopy laboratory from the Cesar Lattes Nanoscience and Nanotechnology Center (C2Nano)LNLSMolecular Spectroscopy Laboratory from the University of Sao Paulo (USP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES