Abstract 1,4-dihydro-1,2,4,5-tetraarylpyrrolo[3,2-b]pyrroles are a versatile class of materials with simple synthesis and promising application in organic electronic devices. In this work we present a method of synthesis of new 1,4-dihydro-1,2,4,5-tetraarylpyrrolo[3,2-b]pyrrole derivatives, with ester and carboxylic acid groups as anchoring groups, by multicomponent reactions using niobium pentachloride as catalyst. The new materials were structurally and optically characterized. Also, it was compared the bonding of different moieties to the titanium dioxide mesoporous film. The preliminary tests as dyes in standard configuration in dye-sensitized solar cells have shown a potential performance in the energy conversion.

The microwave-assisted hydrothermal method was used to obtain α-Ag2WO4. Rietveld refinement confirmed that α-Ag2WO4 is stable in the orthorhombic phase, without secondary phase. However, field-effect scanning electron microscope analysis showed that α-Ag2WO4 nanorods surfaces contain silver nanoparticles, confirmed by the X-ray photoelectron spectroscopy by the peak observed at 374.39 eV. In addition to metallic Ag, other Ag oxidation states were also observed on the surface. Hence, Ag (I) as Ag2O and Ag (I) as Ag2WO4 also were identified. DC measurements exhibited a high capacity of charge storage, nevertheless, with a large loss tangent (0.12 µC.cm-2.V-1) and no residual polarization for the voltage range between -100 V and +100 V. AC measurements at frequencies less than 275 Hz, revealed that ionic polarization is dominant, whereas at frequencies higher than 275 Hz, the electronic behavior predominates. The potential of electromagnetic energy conversion in thermal was observed from loss tangent analysis.

The aim of this study was to develop a novel, simple and fast route to prepare ZnO nanorods (NRs) -Au nanoparticles (NPs) hybrids directly supported on a substrate to be used in gas sensor devices. The ZnO NRs were promptly grown on interdigitated Au electrodes Al2O3 substrates by chemical bath deposition at a low temperature. After that, Au NPs were deposited by sputtering. Results obtained by XRD, SEM, EDX and TEM showed the perpendicularly aligned growth of the ZnO NRs with a hexagonal base on the substrate and the Au NPs homogeneously covered the ZnO NRs surface. The ZnO NRs-Au NPs hybrids-based sensor exhibited an improved sensor response for H2 and O2 gases compared to the ZnO NRs at 300 ºC. Due to the ability to prepare homogeneous hybrids with high surface directly supported on the substrate; the developed route might provide a convenient approach to preparing gas sensor devices.

Glass ionomer cements (GICs) are products of the acid-base setting reaction between an finely fluoro-alumino silicate glass powder and poly(acrylic acid) in aqueous solution. The sol gel method is an adequate route of preparation of the glasses used to obtain the GICs. The objective of this paper was to compare two powders: a commercial and an experimental and to investigate the structural changes during hardening of the cements by FTIR and Al MAS NMR. These analyses showed that the experimental glass powder reacted with organic acid to form the GICs and it is a promising material to manufacture dental cements.

Glass ionomer cements are glass and polymer composite materials. These materials currently find use in dentistry. The purpose of this work is to obtain glass powders based on the composition 4.5SiO2 - 3Al2O3 - 2CaO to be used in dentistry. The powders were prepared by a chemical route at 700 0C. The properties of glass ionomer cements obtained from powders prepared at 700 ºC were studied. Diametral tensile strength and microhardness were evaluated for the experimental glass ionomer cements and a commercial material. It was concluded that the properties of experimental cements were similar to those of the commercial ones.

This paper reports a study of the influence of Cr concentration and preparation method in the electrical conductivity and microstructure of SnO2-based powders doped with Mn and Nb, prepared by an organic route (Pechini method) and a mixture of oxides. All the samples were compacted into discs and sintered at 1300 °C for 3h, resulting in ceramics with relative density varying between 81 and 99%. The powders were morphologically characterized by X-ray diffraction and their specific surface area was determined by N2 adsorption/desorption isotherms. Electrical conductivity characterization indicated that the conductivity decreases as Cr concentration increases, probably due to Cr segregation at grain boundaries, which reduces grain size, increasing the number of resistive boundaries, thus limiting the passage of current.

Neste trabalho foi estudada resistência de cadinhos de SnO2 dopados com 1%mol de ZnO frente a corrosão na fusão de vidro contendo metais pesados. Os cadinhos foram obtidos através do processo de colagem de barbotina, e a sinterização foi realizada até a temperatura de 1400ºC por 4 horas. Os vidros foram fundidos uma única vez por 1 hora, sendo que o vidro de composição 50B2O3-50PbO à 700 ºC, o de composição 60B2O3-40BaO à 1150 ºC e o de composição 66,67B2O3-33,33PbO à 700 ºC, sendo resfriados no interior dos cadinhos. Estes cadinhos foram então preparados e analisados por MEV-EDS.

In this work it was studied resistance of crucibles of SnO2 doped with 1%mol of ZnO when they are submitted to thermal treatment for melting glass with heavy metals. The crucibles were obtained through the slip casting process, and the sintering temperature was 1400ºC by 4 hours. The glass composition of 50B2O3-50PbO, 60B2O3-40BaO and 66,67B2O3-33,33PbO was melted at 700ºC, 1150ºC and 700ºC respectively. All these glasses compositions were melted only one time for 1h and chilled inside the crucibles. These crucibles were analyzed by SEM-EDS.