This paper reports the synthesis and characterization of Cr3+-doped alumina by the sol-gel non-hydrolytic methodology. The resulting sample was treated at different temperatures. X-ray diffraction revealed that the ruby phase emerged in the sample treated at 1100 ºC, which was later confirmed by absorption bands correspondent to Cr3+ ions allowed transitions at 4A2 → 4T1, 4T2, and forbidden at 4A2 → 2T1, 2E, observed by diffuse reflectance UV-Vis. The luminescence spectroscopy showed the intensity band at 694 nm in red region, characterized of the Cr3+ ion. The peaks at 702 and 705 nm correspond to N1 and N2 lines, respectively, which arose from the second and fourth nearest-neighbor exchange-coupled pairs of chromium(III) ion, respectively, ascribed to high chromium(III) concentration. The Cr3+ cluster formation was observed in electron paramagnetic resonance signal as discussed in this work. Nuclear magnetic resonance evidenced that the 27 Al symmetry changed in the samples treated between 900 and 1100 ºC.

The development of drug delivery systems for photodynamic therapy (PDT) is increasingly demanded due to the hydrophobicity presented by most of photosensitizers molecules. Bacterial cellulose (BC), a highly pure cellulose produced by bacteria, possesses the essential features for applications in drug delivery systems, such as large surface area and excellent loading capacity. BC membranes prepared containing a photosensitizer, chloroaluminum phthalocyanine (ClAlPc), were tested aiming applications as a drug delivery system for PDT skin cancer protocols. BC membranes production was optimized regarding thickness and optical transmission. Thinner membranes lead to higher relative incorporation efficiencies. Skin permeation and retention in vitro tests were performed by using pig's ears as a skin model. ClAlPc was retained at stratum corneum and epidermis/dermis, showing adequate properties for topical administration of ClAlPc. Photophysical studies showed that singlet oxygen production was not affected for ClAlPc compartmentalized in the BC array. BC-ClAlPc membranes did not present cytotoxic effects in vitro.

In this second part it will be discussed some photonic applications of glassy and glass ceramic thin films which can be used as planar waveguides. Some photonic applications require certain specifications of glass, which can be quantified by studying the nonlinear optical properties of the materials. Therefore, a brief introduction of these phenomena is discussed, as well as the use of femtosecond lasers to manipulate the composition or for the preparation of waveguides into glasses. Finally, the article will address a brief introduction on microstructured optical fibers and commercial application prospects for these devices.

2015 is the Year of Light, according to UNESCO. Chemistry has a close relationship with light and one of the materials that allows such synergy is glass. Depending on the chemical composition of the glass, it is possible to achieve technological applications for the whole range of wavelengths extending from the region of the microwave to gamma rays. This diversity of applications opens a large range of research where chemistry, as a central science, overlaps the fields of physics, engineering, medicine, etc., generating a huge amount of knowledge and technological products used for humanity. This review article aimed at discussing some families of glasses, illustrating some applications. Due to the extension of the theme, and all points raised, we thought it would be good to divide the article into two parts. In the first part we focus on the properties of heavy metal oxide glasses, fluoride glasses and chalcogenide glasses. In the second part we emphasize the properties of glassy thin films prepared by sol-gel methodology and some applications, of both glasses as the films in photonics, and more attention was given to the nonlinear properties and uses of photonic fibers.

New luminescent organic-inorganic hybrid particles based on Tb-doped aluminates and asparagine (Asn) surface modifiers were investigated. The Tb3+ doped inorganic core was obtained by spray pyrolysis, at 200 ºC γ-AlOOH (BOE:Tbx%) or at 700 ºC γ-Al2O3 (γTA:Tbx%). The reaction of Asn with boehmite in water disaggregated the sub-micronic boehmite particles to give stable dispersion of surface modified nanoparticles Asn:BOE:Tbx% (x = 1 or 5). Concerning the Asn:γTA:Tbx% system, an Asn film wrapping alumina particles was observed. Photoluminescence spectra exhibited the bands assigned to Tb3+5D4 → 7FJ = 6-3 transitions. A broad absorption band (240 nm) was assigned to the host (aluminate) to ion (Tb3+) energy transfer. Efficient energy transfer was observed when active ions are incorporated in the defect-spinel structure of γTA, whereas it was relatively weak for BOE:Tb where Tb3+ are bonded to the hydroxyls groups at nanocrystals surface. It is noticeable that Asn strengthens the linkage of Tb3+ with the aluminate matrix, enhancing the host to dopant energy transfer.

Commercial copolymers based on styrene and divinylbenzene containing sulfonic acid groups were used as support for the incorporation of silver nanoparticles. These nanoparticles were obtained in situ by the reduction of Ag+ by using hydroxylamine in the presence of a protective agent. These materials were characterized with determination of the silver content and their morphological characteristics. The antibacterial activity of the final products against Escherichia coli was evaluated and the results show that the synthesized copolymers had antibacterial effect varying from 54 to 100%. The most efficient composite was made with small, well distributed particles.

O presente trabalho discute os recentes avanços na biossíntese e na produção de celulose bacteriana (CB) pela gram-negativa, aeróbia e aceto-ácida Gluconacetobacter. xylinus. A CB se difere de seu par vegetal, principalmente devido ao seu caráter de fibras nanométricas, contra o caráter micrométrico da vegetal, são extruídas através da parede celular de G. xylinus, com isso sua estrutura macroscópica é mecanicamente e fisicamente mais resistente, abrindo grandes oportunidades de aplicações tecnológicas e biológicas, muito além das obtidas pela celulose vegetal. O desafio atual está no aumento da produção de CB, que se debruça num maior entendimento de sua biossíntese para que seja possível uma posterior manipulação genético-bioquímica oriundas do recente avanço na biologia molecular e nos bioprocessos. São relacionados trabalhos utilizando a CB como base para produção de compósitos como também o que a está sendo feito de mais atual com este material biológico.

The present paper discusses the recent advances about the biosynthesis and production of bacterial cellulose (BC), from gram-negative, aerobic and acetic acid Gluconcetobacter xylinus (Gx). The BC differs from his vegetal pair, mainly due his feature of nanometric fibers, as opposed to micrometric feature of vegetal cellulose, are extruded through the cellular wall of Gx, thereby the macroscopic structure of BC is mechanically and physically more resistant, open big opportunities of biological and technological applications, apart from that obtained by vegetal cellulose. The actual challenge is in the grown of production of BC, which deals a superior understanding of his biosynthesis, to makes possible a later genetic-biochemical manipulation derived from recent advances in molecular biology. Are related works using the BC for production of composites and also what is being done of more actual with this biological material.

A simple method was developed to load a large amount of silver nanoparticles into bacterial cellulose (BC) produced by Gluconacetobacter xylinus in a controlled manner. Due to the high electron-rich oxygen density in the BC macromolecules and the large surface area of the BC nanoporous structure as an effective nanoreactor, the in situ direct metallization technique was successfully used to synthesize Ag nanoparticles with an average diameter of 30 nm and a loading content of at least 5 wt. (%), approximately. This novel procedure provides an easy and economical way to manufacture Ag nanoparticles supported on a porous membrane for various biomedical applications. These composite fibers showed nearly 100% antibacterial activity (elimination of microorganisms) against Escherichia coli because of the presence of the silver nanoparticles.

The electrochemical study of glass like tungsten oxide derivatives requires the construction of special electrodes due to the fact that these glasses are not conductive. Electrodes modified with WO3 change their color when submitted to some potential perturbation. The color change of the electrochromic materials was observed in situ by coupling an electrochemical cell to a stereomicroscope. The constructed cell is versatile and may represent a great contribution to the electrochemical studies of materials, especially in the systems where it is interest to observe the working electrode surface during the electrochemical experiment.

Esferas de poliestireno foram obtidas através da polimerização do estireno sem a presença de emulsificante. A suspensão foi caracterizada por Espalhamento de Luz e Microscopia Eletrônica de Transmissão apresentando monodispersidade com tamanho em torno de 463 nm. O método de deposição vertical foi utilizado para preparar filmes em substratos de vidro a partir da suspensão de esferas. Filmes de opalas de alta qualidade foram obtidos e caracterizados por Espectroscopia de Reflectância, Microscopia Eletrônica de Varredura e Microscopia Óptica.

Polystyrene latex spheres were obtained by free-emulsifier polymerization of styrene. Suspension was characterized by Photon Correlation Spectroscopy (PCS) and Transmission Electron Microscopy (TEM) and were observed to be monodisperse with sizes around 463 nm. A vertical deposition method was used in order to prepare films deposited on glass slides from the spheres suspension. High-quality opal-like films were obtained and characterized by Reflectance Spectroscopy, Scanning Electron Microscopy (SEM) and Optical Microscopy.

A análise espectral só se torna confiável se o espectro é detalhadamente analisado quanto a todos os picos sobrepostos e ocultos. Neste trabalho são descritas as etapas para revelar e separar esses picos na faixa de 3000-4000 cm-1 em três espectros de absorção de infravermelho colhidos na superfície vítrea de fibras ópticas de sílica hidrolizada. A revelação dos picos foi feita com a análise da segunda e quarta derivada dos dados experimentais digitalizados, juntamente com o conhecimento disponível de espectroscopia de infravermelho da interação sílica-água na faixa espectral investigada. A separação de picos foi realizada com ajuste de curva usando quatro modelos distintos. O melhor ajuste foi alcançado com um modelo que descrevia os espectros com uma soma de picos do tipo Gaussiano. Mapas descrevendo os limites de ombro ("shoulder limits") e de detecção foram utilizados para validar os detalhes espectrais revelados.

Reliable spectral analysis is only achieved if the spectrum is thoroughly investigated in regard to all hidden and overlapped peaks. This paper describes the steps undertaken to find and separate such peaks in the range of 3000 to 4000 cm-1 in the case of three different infrared absorption spectra of the glass surface of hydrolyzed silica optical fibers. Peak finding was done by the analysis of the second and fourth derivatives of the digital data, coupled with the available knowledge of infrared spectroscopy of silica-water interaction in the investigated range. Peak separation was accomplished by curve fitting with four different models. The model with the best fit was described by a sum of pure Gaussian peaks. Shoulder limit and detection limit maps were used to validate the revealed spectral features.

Guias de luz planares foram obtidos a partir de um sol de um novo híbrido Ti4+-acetilacetona (acac)-Ureasil depositado na forma de filmes finos sobre substratos de vidro. A estrutura foi investigada por medidas espectroscópicas (absorção no infravermelho, fotoelétrons de raios-X e espalhamento Raman) e espalhamento de raios-X a baixos ângulos (SAXS). Para a adição do complexo Ti-acac ao ureasil na razão molar Ti:Si de 1:1 interações entre o complexo Ti-acac e grupos siloxanos foram identificadas. Quantidades maiores de Ti4+ (razão molar Ti:Si de 5:1) levam também à formação de nanoagregados ricos em titânio. Os parâmetros ópticos dos guias, como índice de refração, espessura, modos propagados e coeficiente de atenuação foram medidos para 632,8, 543,5 e 1550 nm pela técnica de acoplamento de prisma. O índice de refração pode ser controlado pela quantidade relativa de titânio. Guias de poucos micra de espessura suportam modos de propagação com baixas perdas para todas as composições.

Hybrid planar waveguides were prepared from Ti4+-acetylacetone (acac)-Ureasil sols deposited on glass substrates. Structural features have been investigated by spectroscopic measurements (Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Raman scattering) and Small Angle X-ray Scattering (SAXS). Addition of Ti4+-acac to the ureasil (Ti:Si molar ratio 1:1) leads to the formation of bonds between the Ti complex and the siloxane groups, whereas further addition of Ti4+ (Ti:Si molar ratio 5:1) leads to the additional formation of titanium-rich nanoclusters. The optical parameters of the waveguides such as refractive index, thickness, propagating modes and attenuation coefficient were measured at 632.8, 543.5 and 1550 nm by the prism coupling technique. The refractive index can be tuned by the Ti4+ relative content. The few microns thick planar waveguides support well confined propagating modes with low attenuation loss for all compositions.

In this work we report some aspects of the chemistry involved in the preparation of modified silicon oxide by the sol-gel process. Europium III compounds were used as luminescent probe. An organic-inorganic hybrid was obtained by hydrolysis of tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (APTS). The Eu III compounds were added in different ways. In the first, silica was prepared in the presence of Eu III, and in the second, Eu III was added on the silica surface. These materials were studied by luminescence, infrared spectroscopy and termogravimetric analysis. The results obtained for the hybrid material show different behavior for Eu III emission, which could be excited by the antenna effect and the influence of the surrounding in the luminescence quenching. The thermogravimetric data present different mass loss in samples to range temperature 50 - 150 °C. Thermogravimetric and infrared spectra showed that inorganic polymers incorporated the organic part.

The conditions for the preparation of luminescent materials, consisting of Eu3+ ions entrapped in a titanium matrix, in the forma of a thin film, using the sol-gel process, are described. The films were obtained from sols prepared with TEOS and TEOT, in the presence of acetylacetone as the hidrolysis-retarding agent, using the dip-coating and spin-coating techniques. The influence of these techniques on the films based on titanium and silicon are presented. The Eu3+ was used as a luminescent probe. The films have been characterized by luminescence, reflection and transmittance. The thickness of the films could be related to the preparation procedure. Transparent thin films have been prepared by dip-coating technique.

The ferroelectric compound LiNbO3 was prepared by the polymeric precursors method in the polycrystalline form containing different concentrations of Eu3+. The compounds were characterized by X-ray diffraction, vibrational and electronic spectroscopy. Electronic spectroscopy was shown to be sensitive to small concentrations of contaminating phases allowing a good control of the compound purity. The presence of Eu3+ ions leads to the formation of the LiNb3O8 phase in the range of 500 to 800 °C. Above this temperature range LiNbO3 and tetragonal (T') EuNbO4 were obtained.