Effect of cerium on structure modifications of a hybrid sol–gel coating, its mechanical properties and anti-corrosion behavior

An organic–inorganic hybrid coating was developed to improve the corrosion resistance of the aluminum alloy AA 2024-T3. Organic and inorganic coatings derived from glycidoxypropyltrimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al(OsBu)3, with different cerium contents, were deposited onto aluminum by dip-coating process. Corrosion resistance and mechanical properties were investigated by electrochemical impedance measurements and nano-indentation respectively. An optimal cerium concentration of 0.01 M was evidenced. To correlate and explain the hybrid coating performances in relation to the cerium content, NMR experiments were performed. It has been shown that when the cerium concentration in the hybrid is higher than 0.01 M there are important modifications in the hybrid structure that account for the mechanical properties and anti-corrosion behavior of the sol–gel coating

Near-infrared/visible-emitting nanosilica modified with silylated Ru(II) and Ln(III) complexes

Three luminescent silica-based nanohybrids were fabricated by grafting of silylated Ru(II)andNd/Yb(III)complexes onto mesoporous silica nanoparticles obtained by microemulsion method.The prepared nanohybrids were characterized by Fourier transform-Raman spectroscopy, solidstate-nuclear magnetic resonance, high resolution-transmission electron microscopy andscanning and transmission electron microscopy techniques. The chemical integrity and thegrafting of all complexes inside MSNs nanopores as well as a good distribution of metalcomplexes onto MSNs surface were achieved for all nanohybrids. Photophysical results revealedthat by monitoring the excitation on Ru(II)moieties from SiO2–RuNd and SiO2–RuYb nanohybrids, the sensitization of NIR-emitting Nd/Yb(III)ions were successfully detected viaenergy transfer processes. Energy transfer rates(kEnT)of 0.20×107and 0.11×107s−1 and efficiencies of energy transfer(ηEnT)of 40% and 27.5% were obtained for SiO2–RuNd and SiO2–RuYb nanohybrids, respectively. These results confirm the preparation of promising dual(near-infrared/visible)-emitting silica-based nanohybrids as new nanotools for applications asnanosensores and nanomarkers

Luminescent nanohybrids based on silica and silylated Ru(II)—Yb(III) heterobinuclear complex: new tools for biological media analysis

Lanthanide (Ln) complexes emitting in the near-infrared (NIR) region have fostered great interest as upcoming optical tags owing to their high spatial and temporal resolution emission as well deeper light penetration in biological tissues for non-invasive monitoring. For use in live-cell imaging, lanthanide complexes with long-wavelength absorption and good brightness are especially critical. Light-harvesting ligands of Ln complexes are typically excited in the ultraviolet region, which in turn trigger simultaneously autofluorescence and long-exposition damage of living systems. The association of d-metalloligands rather than organic chromophores enables the excitation of NIR-emitting Ln complex occurs in the visible region. Taking advantage of the long-lived excited states and intense absorption band in the ultraviolet (UV) to NIR region of Ru(II), we successfully design a dual-emitting (in the visible and NIR region) d–f heterobinuclear complex based on Ru(II) metalloligand and Yb(III) complex. In addition, we developed luminescent nanohybrids by grafting of Ru(II)–Yb(III) heterobinuclear complexes containing silylated ligands on the surface of mesoporous and dense silica matrix. The nanomarkers were successfully applied for imaging of murine melanoma B16-F10 and neonatal human dermal fibroblast HDFn cell cultures by one-photon or two-photon absorption using laser scanning confocal microscopy. Great cellular uptake, low cytotoxicity and the possibility to achieve visible and NIR emission via two-photons excitation show that the nanohybrids are remarkable markers for in vitro and a potential tool for in vivo applications

Incorporação de tiofosfatos em vidros calcogenetos: estrutura e fenômenos fotoinduzidos

Neste trabalho descreve-se o estudo estrutural do sistema binário As2S3-P2S5, e o efeito da incorporação do Ga2S3 na composição vítrea 50As2S3-50P2S5. Para o sistema As2S3-P2S5 foram obtidos vidros com concentrações até 70% P2S5. As temperaturas características dos vidros foram determinadas através de análise térmica diferencial. A investigação estrutural foi realizada utilizando-se as técnicas espectroscópicas de infravermelho, Raman e Ressonância Magnética Nuclear do 31P. A distribuição dos átomos de fósforo na estrutura vítrea foi avaliada através da intensidade da interação dipolar magnética entre núcleos de 31P, obtendo-se valores experimentais do segundo momento M2, utilizando a técnica de spin eco de Hahn. Foram realizadas simulações numéricas de M2 para o sistema As-P-S, considerando três modelos estruturais diferentes de distribuição dos 31P nos vidros: distribuição homogênea, distribuição randômica em uma rede do tipo ZnS e a formação de arranjos moleculares como As2P2S8, P4S9 e P4S10. Através dos experimentos de 31P-MAS, Raman e Infravermelho e dos resultados experimentais e numéricos de M2 obtidos, conclui- se que os vidros são constituídos por unidades S=PS3/2 tetraédricas, encontrando-se principalmente nos arranjos As2P2S8 até 50% de P2S5, acima dessa concentração é evidenciado a presença de unidades moleculares de P4S9 e/ou P4 S10. Para o sistema Ga-As-P-S evidenciou-se através das técnicas espectroscópicas de infravermelho e Raman a diminuição do caráter p da ligação P=S, indicando uma interação com o Ga2S3, resultando na formação de arranjos GaPS4 sobre os arranjos As2P2S8. Esta suposição também foi evidenciada através da diminuição da interação dipolar do 31P-31P. Para aplicação desses vidros, os fenômenos fotoinduzidos foram avaliados nas composições vítreas As2S3 e 80As2S3-20P2S5...A structural study of the binary system As2S3-P2S5, and the effect of the incorporation of Ga2S3 in 50As2S3-50P2S5 glass are presented in this thesis. Starting from the As2S3 composition glasses, were obtained in the As2S3-P2S5 system for compositions up to 70 mol% P2S5. The characteristic temperatures of the glasses were obtained using differential thermal analysis. Infrared spectroscopy, Raman scattering and 31P Nuclear Magnetic Resonance were used in the structural study. The distribution of P atoms over the glass structure was investigated using a Hahn spin-echo sequence to evaluate the 31P-31P dipolar interactions through the measurement of the second moment M2. Numerical simulations of M2 were carried out assuming three different structural models for the glass: 1-P homogeneously dispersed on the As-S network, 2-P randomly distributed on the As-S network and 3-pseudomolecular As-P-S arrangements (as for example As2P2S8, P4S9 or P4S10). The spectroscopic results lead to the conclusion that the glasses are constituted by tetrahedral (S=PS3/2) units, mainly in As2P2S8 arrangements up to 50% of P2S5. Above this concentration the presence of molecular units of P4S9 and/or P4S10 is evidenced. For the Ga-As-P-S system the reduction of the double bond character (P=S) was deduced from Raman scattering and infrared absorption. The formation of GaPS4 groups on the base As2P2S8 groups was suggested. This assumption also is evidenced from the reduction of the dipole interaction of the 31P-31P. Photoinduced phenomena were evaluated for the As2S3 and 80As2S3-20P2S5 glass compositions. The samples were irradiated by different wavelengths (351, 488 e 514 nm) using a continuous Argon laser (CW), varying the power of irradiation and exposure time. A depression area was observed in the illuminated sample at 351 nm that could be due to either to etching either to vaporization...(Complete abstract click electronic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Photoinduced effects in As-S-P glasses

We report the photoinduced effects on the glass composition As(2)S(3) and As(29.6)P(7.4)S(63) when exposed to UV light. The morphology of the glass surface irradiated at different power densities was investigated by use of optical microscopy and scanning electron microscopy (SEM). A power density dependence on the photoexpansion (PE) and photoablation (PA) is observed. Raman measurement after irradiation shows the formation of As-O bonds in As(29.6)P(7.4)S(63). Also, the appearance of P=O bonds indicate the incorporation of oxygen at the glass surface during the irradiation process. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Understanding the Microstructure Connectivity in Photopolymerizable Aluminum-Phosphate-Silicate Sol–Gel Hybrid Materials for Additive Manufacturing

In this paper, we report the synthesis and structural characterization of transparent and photopolymerizable aluminum-phosphate-silicate hybrid materials obtained via the sol–gel route, with different aluminum/phosphate (Al/P) ratios. We explored the system Si(1–x)–(Al/P) (x) with x varying from 0.3 to 1, and atomic ratios of Al/P are 1:3, 1:1, and 3:1. All compositions contain high inorganic mass content (up to 40 wt %). Furthermore, they are compatible with vat-photopolymerization platforms. The structural evolution of the hybrid materials with the silicon concentration was investigated by SEM, phase-contrast AFM, and solid-state NMR techniques, using single- and double-resonance experiments. The structure follows the build-up principle using aluminum-phosphate species and alkoxysilane chains as fundamental building blocks. These aluminum-phosphate species were identified as monomeric and dimeric chain structures by comparing different parameters obtained from NMR data to compound models. Monomeric and dimeric aluminum-phosphate chain structures were predominant in 3:1 and 1:3 Al/P ratio samples, respectively, promoting and hindering the heterocondensation with the alkoxysilane precursor, respectively. The photopolymerization mechanism leads to the percolation of the inorganic networks through a parallel polymethylmethacrylate network, resulting in a material with structural heterogeneities in the range of 5 nm, evidenced by phase-contrast AFM

Ultraviolet Upconversion Luminescence in a Highly Transparent Triply-Doped Gd³⁺–Tm³⁺–Yb³⁺ Fluoride–Phosphate Glasses

We report near-infrared to ultraviolet (UV) upconversion emissions in triply-doped Gd³⁺–Tm³⁺–Yb³⁺ fluoride–phosphate glasses. Emission at 310 nm, originated from the Gd³⁺:⁶P_7/2 → ⁸S_7/2 transition, was observed for the first time in glasses. The high-purity glasses prepared exhibit extended transparency in the UV down to 200–250 nm. The mixed fluoride–phosphate environment of the rare-earth ions was characterized by means of NMR techniques using scandium as a diamagnetic mimic for the luminescent species, for which the ligand distribution was quantified by ⁴⁵Sc­{³¹P} rotational echo double-resonance NMR. Both the intensity of the Gd³⁺ emission as well as those of the UV emissions at 290, 347, and 363 nm increase with increasing ratio of fluoride to phosphate ligands coordinating to the rare-earth ion

Preparation and Characterization of Chitosan Nanoparticles for Zidovudine Nasal Delivery

Zidovudine (AZT) is the antiretroviral drug most frequently used for the treatment of Acquired Immunodeficiency Syndrome. Its low oral bioavailability demands the development of innovative strategies to overcome the first pass metabolism. The nasal route is an option for enhanced therapeutic efficacy and to reduce the extent of the first-pass effect. In this article, AZT loaded chitosan nanoparticles were prepared by a modified ionotropic gelation method with sodium tripolyphosphate. The increase proportion of CS (NP1 10:01 (w/w)) promoted the formation of smaller nanoparticles (260 nm), while raising the proportion of TPP (NP2 5:1 w/w) increased the nanoparticles size (330 nm). The incorporation of AZT increased the nanoparticles size for both AZT-loaded nanoparticles AZT-loaded NP1 (406 nm) and AZT-loaded NP2 (425 nm). The incorporation of AZT into NP1 did not change the electrophoretic mobility, however, in AZT-loaded NP2 there was a significant increase. The positive surface of the nanoparticles is very important for the mucoadhesive properties due interaction with the sialic groups of the mucin. Nuclear resonance magnetic data showed that the higher concentration of chitosan in the nanoparticles favored the interaction of few phosphate units (pyrophosphate) by ionic interaction Scanning electron microscopy, revealed that the nanoparticles are nearly spherical shape with porous surface. The entrapment efficiency of AZT, was 17.58%+/- 1.48 and 11.02%+/- 2.05 for NP1 and NP2, respectively. The measurement of the mucoadhesion force using mucin discs and nasal tissue obtained values of NP1 = 2.12 and NP2 = 4.62. In vitro permeation study showed that the nanoparticles promoted an increase in the flux of the drug through the nasal mucosa. In view of these results, chitosan nanoparticles were found to be a promising approach for the incorporation of hydrophilic drugs and these results suggest that the CS-containing nanoparticles have great potential for nasal AZT administration.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq