Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO4 nanocrystals

This communication is a report of our initial research to obtain iron tungstate (FeWO4) nanocrystals by the microwave-hydrothermal method at 170 degrees C for 45 min. X-ray diffraction patterns showed that the FeWO4 nanocrystals prepared with polyethylene glycol-200 have a partial preferential orientation in the (011) plane in relation to other nanocrystals prepared with sodium bis(2-ethylhexyl) sulfosuccinate and water. Rietveld refinement data indicates that all nanocrystals are monophasic with wolframite-type monoclinic structures and exhibit different distortions on octahedral [FeO6]/[WO6] clusters. High resolution transmission electron microcopy revealed an oriented attachment mechanism for the growth of aggregated FeWO4 nanocrystals. Finally, we observed that the photoluminescence properties of these nanocrystals are affected by partial preferential orientation in the (011) plane and distortions on [FeO6]/[WO6] clusters.Brazilian research financing institution FAPESPBrazilian research financing institution: FAPESP [2009/53189-8, 2009/50303-4]Brazilian research financing institution: CNPq [159710/2011-1]Brazilian research financing institution: CNPqBrazilian research financing institution: CAPESBrazilian research financing institution: CAPE

Facile synthesis and characterization of ZrO2 nanoparticles prepared by the AOP/hydrothermal route

We report on the synthesis and characterization of ZrO2 nanoparticles prepared from zirconium(IV) butoxide in the absence of base or acid mineraliser by an advanced oxidation processes (AOP) and subsequent hydrothermal treatment which involves mixing and dissolution of the precursor for different temperatures. The structure, morphology and properties of the nanoparticles were characterized using XRD, FE-SEM, TEM, HRTEM, Raman spectroscopy, FT-IR spectroscopy, BET measurements and TGA measurements. The structural analysis by XRD and Raman spectroscopy confirms the ZrO2 specimens synthesized at 100 degrees C for 1 hour are amorphous and those treated at 150 degrees C and 200 degrees C for 1 hour were crystalline. Structural analysis by Raman spectroscopy confirms tetragonal ZrO2 specimens obtained at temperatures higher than 100 degrees C as a majority phase. From FE-SEM images, the AOP/hydrothermal route mainly produced microspheres comprised of primary nanoparticles. HRTEM images of ZrO2 microspheres, after treatment at 100 degrees C, show the beginning of crystallization, with only a few clear lattice fringes dispersed in the specimens. TEM and HRTEM images of ZrO2, after treatment at 150 degrees C and 200 degrees C indicate that the microspheres are the aggregation of small nanoparticles with a size of approximately 5-8 nm, and FFT analysis confirms the high crystallinity of the specimens. TGA analyses show a distinctive behavior for each of the ZrO2 specimens, after treatment at 100 degrees C, 150 degrees C and 200 degrees C. FT-IR analysis of ZrO2 specimens after hydrothermal treatment revealed the presence of groups, such as -OH, -CH2, and -CH at the surface. In addition, FT-IR spectra show a decrease in the amount of functional groups attached to the surface of the nanoparticles when the reaction temperature is increased. This result was also confirmed by TGA analysis. The ZrO2 specimens prepared by the AOP/hydrothermal route exhibited a high surface area of 511-184 m(2) g(-1).Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Semiconducting Sn(3)O(4) nanobelts: Growth and electronic structure

The study of structures based on nonstoichiometric SnO(2-x) compounds, besides experimentally observed, is a challenging task taking into account their instabilities. In this paper, we report on single crystal Sn(3)O(4) nanobelts, which were successfully grown by a carbothermal evaporation process of SnO(2) powder in association with the well known vapor-solid mechanism. By combining the structural data and transport properties, the samples were investigated. The results showed a triclinic semiconductor structure with a fundamental gap of 2.9 eV. The semiconductor behavior was confirmed by the electron transport data, which pointed to the variable range hopping process as the main conduction mechanism, thus giving consistent support to the mechanisms underlying the observed semiconducting character.FAPESPCNPqCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Chemical modification of the surface of alumina with alkaline earth metal oxides using the polymeric precursor method for catalysis application

In this study, modifications of alumina surface with of alkaline earth metal oxides were studied, using the polymeric precursor method. The modified compounds were characterized by X-ray diffraction, nitrogen adsorption-desorption and scanning electron microscopy. The catalytical properties of these new catalysts were evaluated for the transesterification reaction of babassu oil. It is observed that the transesterification reaction of babassu oil with methanol was successfully carried out using the modified alumina samples.Neste trabalho foram estudadas modificações da superfície de alumina com óxidos de metais alcalino-terrosos, usando o método dos precursores poliméricos. Os compostos modificados foram caracterizados por difração de raios X, adsorção-dessorção de nitrogênio e microscopia eletrônica de varredura. As propriedades catalíticas desses novos catalisadores foram avaliadas para a reação de transesterificação de óleo de babaçu. Foi observado que a reação de transesterificação de óleo de babaçu com metanol ocorreu com sucesso na presença das aluminas modificadas

A oralidade vista a partir dos manuais de Português do Ensino Básico

As orientações programáticas de Português para o Ensino Básico têm sublinhado a importância do trabalho explícito sobre a oralidade e, consequentemente, sobre a sua avaliação, indo ao encontro do destaque que é dado à capacidade do bom uso da palavra na sociedade atual. Por sua vez, os manuais escolares, ao fazerem a transposição das orientações programáticas, acabam também por poder influenciar a prática pedagógica. A oralidade é, muitas vezes, entendida exclusivamente como realização informal, fruto de uma atividade inteiramente espontânea, automática e inconsciente, em vez de ser entendida como o resultado de um esforço de planificação deliberado, estruturado e consciente. Apesar de a aquisição da oralidade decorrer da capacidade biológica para a linguagem, a consciência das propriedades deste sistema não existe da mesma forma no falante, exigindo o seu ensino explícito. Espera-se, assim, que, na Escola, seja estabelecida uma relação com a língua, norteada pelo rigor em todos os momentos do processo de ensino e de aprendizagem, contribuindo decisivamente para aumentar o capital linguístico dos alunos. Os manuais escolares são objetos complexos que desempenham funções muito diversas, estando constantemente sob apertado escrutínio. Agregam um vasto conjunto de materiais, em vários suportes, que são também usados pelos professores como guias para a estruturação da aula. Partindo deste enquadramento, pretende-se, com este trabalho, apresentar uma reflexão sobre a abordagem à oralidade nos manuais escolares de Português do Ensino Básico, tendo como base um relatório sobre as repercussões das “Metas Curriculares de Português” na sua organização, complementado com as conclusões de outro estudo centrado nesta problemática. Os resultados deste trabalho mostram que as alterações programáticas não conduzem a mudanças significativas nos manuais quanto à abordagem da oralidade, nomeadamente no que diz respeito à dimensão processual da mesma. Por outro lado, verifica-se que o trabalho proposto no âmbito da leitura e da escrita prevalece sobre as atividades ao nível da oralidade.Instituto Politécnico de Viseu. Centro de Estudos em Educação, Tecnologias e Saúde (CI&DETS

Doped Tin Dioxide (d-SnO₂) and Its Nanostructures: Review of the Theoretical Aspects, Photocatalytic and Biomedical Applications

Nanomaterials based on metal oxides are extensively studied for several applications due to their versatility. Improvements in their performances can be obtained due to specific structural modifications. One possible modification is by doping the crystal structure, which can affect the materials structure and properties, especially in nanosized particles. Electronic features are among the properties that can be modified through the doping process, consequently morphological and optical parameters can also be controlled by this process. In this sense, this review presents some modifications to tin dioxide (SnO2), one the most studied materials, mainly through the doping process and their impact on several properties. The article starts by describing the SnO2 structural features and the computational models used to explain the role of the doping process on these features. Based on those models, some applications of doped SnO2, such as photocatalytic degradation of pollutants, CO2 reduction, and desulfurization of fossil fuels are presented and discussed. Additionally, the review describes many biological applications related to antimicrobial activity for doped SnO2 and its nanostructures. Although most of the examples presented in this article are based on the doped SnO2, it also presents examples related to SnO2 composites with other nanomaterials forming heterojunctions. The metal oxides SnO2, doped-SnO2 and their nanostructures are promising materials, with results reported in many fields presented in this review, such as theoretical and computational chemistry, environmental remediation, nanoparticle morphology control, fossil fuels improvement, and biomedical applications. Although widely explored, there are still fields for innovation and advances with tin dioxide nanostructures, for example, in transparent conducting oxides, in forensics as materials for latent fingerprints visualization, and sensors in medicine for detection of exhaled volatile organic compounds. Therefore, this article aims to be a reference regarding correlating the doping processes and the properties presented by the SnO2 nanostructures