Surface engineering of silica nanoparticles for oral insulin delivery: characterization and cell toxicity studies

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

Characteristics of PbO-BiO1.5-GaO1.5 glasses melted in SnO2 crucibles

PbO-BiO 1.5-GaO 1.5-based glasses are good candidates for optical applications, because of some of their interesting characteristics, such as high refraction indices and high transmission in the ultraviolet (UV), visible (VIS), and infrared (IR) regions. A limited stage in the processing of these glasses is the corrosion that is caused by the melt in all currently used conventional crucibles, such as noble metals (platinum or gold) and Al 2O 3. The absorption of crucible material by the glass composition may reduce the transmission level, the cutoff in the UV-VIS, and IR regions, and the thermal stability. In this study, a SnO 2 crucible has been tested for PbO-BiO 1.5-GaO 1.5 molten glass. Optical and thermal analyses show, in some cases, advantages over the use of platinum and Al 2O 3 crucibles. A visible cutoff value of 474 nm has been measured, and a longer melting time (850°C for 4 h) results in a significant reduction of the O-H absorption band at 3.2 μm.

Porous silica matrix obtained from pyrex class by hydrothermal treatment: Characterization and nature of the porosity

A novel porous silica matrix has been prepared from Pyrex glass, using hydrothermal treatment under saturated-steam condition. This process makes it possible to obtain, in one step, a silica support formed of a homogeneously distributed and interconnected macropore microstructure. The new matrix contains silanol groups that can be used in reactions of surface modification to provide a hybrid material and a selective macrofiltration membrane, and also it can improve chemical inertness. The porous matrix is noncrystalline as obtained and, after thermal treatment at temperatures higher than 950degreesC, exhibits an X-ray pattern characteristic of alpha-cristobalite and low volume contraction. The present samples were characterized by scanning electron microscopy, mercury intrusion porosimetry, nitrogen adsorption-desorption isotherms, infrared spectroscopy, X-ray powder diffractometry, atomic absorption, and high-resolution solid-state nuclear magnetic resonance. The results present a new way of producing a macroporous silica matrix.

IR-visible upconversion and thermal effects in Pr3+/Yb3+-codoped Ga2O3 : La2S3 chalcogenide glasses

IR-visible upconversion fluorescence spectroscopy and thermal effects in pr(3+)/Yb3+-codoped Ga2O3:La2S3 chalcogenide glasses excited at 1.064 mum is reported. Intense visible upconversion emission in the wavelength region of 480-680 nm peaked around 500, 550, 620 and 660 nm is observed. Upconversion excitation of the Pr3+ excited-state visible emitting levels is achieved by st combination of phonon-assisted absorption, energy-transfer and phonon-assisted excited-state absorption processes. A threefold upconversion emission enhancement induced by thermal effects when the codoped sample was heated in the temperature range of 20-200 degreesC is demonstrated. The thermal-induced enhancement is attributed to a multiphonon-assisted anti-Stokes process which takes place in the excitation of the ytterbium and excited-state absorption of the praseodymium. The thermal effect is modelled by conventional rate equations considering temperature-dependent effective absorption cross-sections for the F-2(7/2)-F-2(5/2) ytterbium transition and (1)G(4)-P-3(0) praseadymium excited-state absorption, and it is shown to agree very well with experimental results. Frequency upconversion in singly Pr3+-doped samples pumped at 836 nm and 1.064 mum in a two-beam configuration is also examined.

Luminescence properties of Eu-complex formations into ordered mesoporous silica particles obtained by the spray pyrolysis process

Ordered mesoporous, highly luminescent SiO2 particles have been synthesized by spray pyrolysis from solutions containing tetraethylorthosilicate (TEOS), Eu(NO3)3.6H2O, and cetyltrimethylammonium bromide (CTAB) as structure-directing agents. The 1,10-phenantroline (Phen) molecules were coordinated in a post-synthesis step by a simple wet impregnation method. In addition, other matrices were also prepared by the encapsulation of europium complex Eu(fod)3 (where fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) into mesoporous silica, and then the Phen molecules were encapsulated by different impregnation steps, after which the luminescence properties were investigated. The obtained materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder x-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Powders with polydisperse spherical grains were obtained, displaying an ordered hexagonal array of mesochannels. Luminescence results revealed that Phen molecules had been successfully coordinated as an additional ligand in the Eu(fod)3 complex into the channels of the mesoporous particles without disrupting the structure.

Propriedades ópticas de nanopartículas de halogenetos de cobre preparadas in situ em filmes híbridos de sílica

The sol-gel process is a technique based on the hydrolysis and polycondensation of metal alkoxides have been investigated as an alternative for the preparation of vitreous or glassceramic materials, for allowing the obtaining of high-purity materials at low temperatures, and to obtain hybrid materials with different compositions. When ORMOSILs are doped with nanoparticles, are called nanocomposites, and its functionality arises when electrons confined in scale three-dimensional structures near zero are excited. In principle, such materials exhibit discrete energy level, with peaks in the absorption spectrum. Therefore, the glasses doped semiconductor nanocrystals are important candidates for the preparation of optical filters with sharp cut-off, and are being exploited commercially for coloring glasses. This study evaluates the optical properties presented by hybrid films of silica doped with copper nanoparticles. The matrix was prepared using the alkoxides 3-glycidoxypropyltrimethoxysilane (GPTS) and tetraethylorthosilicate (TEOS) doped with Cu2O and hydrolyzed under reflux conditions in two different acidic conditions (HCl and HBr). After thermal treatment at temperatures between 100 °C and 170 °C and/or under the action of commercial black light radiation, CuCl and CuBr present in the hybrid film are transformed into nanoparticles of CuCl or CuBr. The UV-VIS absorption identified the absorption bands, and its variation

Structure of copper complexes adsorbed on a silica gel surface chemically modified with benzimidazole

Silica gel having a particle size between 0.2 and 0.05 mm and a specific surface area, S BET = 473 m 2 g -1, was chemically modified with benzimidazole. Adsorption isotherms of CuX 2 (X = Cl, Br or ClO 4) from ethanol and acetone solutions were studied at 298 K. The metal is bonded to the surface through the free nitrogen atom of the attached benzimidazole. The average number of ligands co-ordinated to the central metal ion was shown to depend on the solid surface loading by the solute. At low loading the electronic and ESR spectral parameters indicated that the copper ion is in a distorted-tetragonal symmetry field.

Técnica híbrida de plasma para a deposição de filmes de alumina

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização e utilização do resíduo de cerâmica vermelha como material pozolânico em matrizes cimentantes

Pós-graduação em Engenharia Civil - FEIS

Comparison among different pH values of Rhodamine B solution impregnated into mesoporous silica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of silica surface on luminescence properties of tb3+-glutamic acid.

We studied the effect of silica surface on luminescence properties of terbium complex by spectroscopy characterization, where microparticles of mesoporous silica type MSU-X was prepared. We used silica with different surface: calcined, washed, functionalized with 3- aminopropyl-triethoxysilane (APTES), and 3-glycidoxypropyl-trimethoxysilane (GPTMS); impregnated with Tb3+-glutamic acid complex. The obtained materials were characterized by scanning electron microscopy, porosity measurements, small-angle X-ray scattering, as structural characterization; Fourier transform infrared and luminescence spectroscopy, as spectroscopy characterization. Finally, we observed that functional groups at the silica surface lead to changes on luminescent properties of the final materials. The observed shift of the absorption and emission bands can be assigned to the effect of the functional groups of mesoporous silica.

Estudo da utilização de ferramentas a base de nitreto de silício (Si3N4) e alumina (Al2O3) na usinagem do ferro fundido vermicular

Machining is one of the most commonly manufacturing processes used in the modern world, consuming millions of dollars annually. Because of this, it is crucial for the automotive industry to reduce costs on their heat-resistant alloy machining processes, such as compacted graphite iron (CGI), which has shown an increasing trend of its application in diesel engine blocks, brakes disks, among other applications, due to its superior mechanical properties to gray cast iron. Despite this advantage, its use is still limited due to its difficulty of machining, moreover, cutting tools are displayed as the main factor in increasing the machining cost. Seeking an alternative to a better machinability of CGI, this paper aims to study two types of ceramic tools developed in Brazil, and benchmark their performance by dry turning. For this, were used CGI class 450 and two tools: ceramic of silicon nitride (Si3N4) and alumina-based (Al2O3), with a cutting speed (Vc) of 300, 400 and 500 m / min; feed (f) of 0.2 mm / rev and depth of cut (ap) of 0.5 mm, using three replicates and starting with new cutting edges. The results showed that the Al2O3 tool had the best performance in Vc of 500 m / min, while the Si3N4 tool had the best results in Vc of 300 m / min. This can be explained by the tool of Si3N4 based include soft intergranular phase, called amorphous, while alumina has higher abrasion resistance due to its high refractoriness. The results make it clear that the tools have significant potential for machining of compacted graphite iron, being necessary a strict control of the cutting parameters used

Preparação e caracterização de híbridos orgânico-inorgânicos à base de epoxí-silica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo da utilização de ferramentas a base de nitreto de silício (Si3N4) e alumina (Al2O3) na usinagem do ferro fundido vermicular

Machining is one of the most commonly manufacturing processes used in the modern world, consuming millions of dollars annually. Because of this, it is crucial for the automotive industry to reduce costs on their heat-resistant alloy machining processes, such as compacted graphite iron (CGI), which has shown an increasing trend of its application in diesel engine blocks, brakes disks, among other applications, due to its superior mechanical properties to gray cast iron. Despite this advantage, its use is still limited due to its difficulty of machining, moreover, cutting tools are displayed as the main factor in increasing the machining cost. Seeking an alternative to a better machinability of CGI, this paper aims to study two types of ceramic tools developed in Brazil, and benchmark their performance by dry turning. For this, were used CGI class 450 and two tools: ceramic of silicon nitride (Si3N4) and alumina-based (Al2O3), with a cutting speed (Vc) of 300, 400 and 500 m / min; feed (f) of 0.2 mm / rev and depth of cut (ap) of 0.5 mm, using three replicates and starting with new cutting edges. The results showed that the Al2O3 tool had the best performance in Vc of 500 m / min, while the Si3N4 tool had the best results in Vc of 300 m / min. This can be explained by the tool of Si3N4 based include soft intergranular phase, called amorphous, while alumina has higher abrasion resistance due to its high refractoriness. The results make it clear that the tools have significant potential for machining of compacted graphite iron, being necessary a strict control of the cutting parameters used