234 resultados para STABILIZED CDTE NANOCRYSTALS


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Tungsten oxide/titania (WO3/TiO2) nanopowders were synthesized by the polymeric precursor method which varied the WO3 content between 0 and 10 mol%. The powders were thermally treated in a conventional furnace and their structural, microstructural and electric properties were evaluated by X-ray diffraction (XRD), Raman spectrometry, N 2 physisorption, NH3 chemisorption, temperature-programmed reduction (TPR), X-ray absorption near-edge spectroscopy (XANES) in situ XANES and extended X-ray absorption fine structure spectroscopy (EXAFS) and transmission electron microscopy (TEM). XRD and Raman spectrometry confirmed the homogeneous distribution of an amorphous WO3 phase in the TiO 2 matrix which stabilized the anatase phase through the generation of [TiO5·V0] or [TiO5·V 0] complex sites. Conventional TPR-H2 (temperature programmed reduction) along with XANES TPR-H2 and XANES TPR-EtOH showed that WO3/TiO2 sample reduction occurs through the formation of these complex clusters. Moreover, the addition of WO3 promoted an increase in the surface acidity of doped samples as revealed by NH3 chemisorption. The WO3/TiO2 bulk-ceramic samples were further used to estimate their potential application in a humidity sensor in the range of 15-85% relative humidity. Probable reasons that lead to the different humidity sensor responses of samples were given based on the structural and surface characterizations. Correlation between the sensing performance of the sensor and its structural features are also discussed. Although all samples responded as a humidity sensor, the W2T sample (2 mol% added WO3) excelled for sensitivity due to the increase in acid sites, optimum mean pore size and pore size distribution. © 2013 Elsevier B.V.

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Breast cancer is a public health problem throughout the world. Moreover, breast cancer cells have a great affinity for hydroxyapatite, leading to a high occurrence of bone metastasis. In this work we developed a bio-nanocomposite (bio-NCP) in order to use such affinity in the diagnosis and treatment of breast cancer. The bio-NCP consists of magnetic nanoparticles of Mn and Zn ferrite inside a polymeric coating (chitosan) modified with nanocrystals of apatite. The materials were characterized with synchrotron X-ray Powder Diffraction (XPD), Time-of-Flight Neutron Powder Diffraction (NPD), Fourier Transformed Infra-red Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and magnetic measurement with a Physical Property Measurement System (PPMS). We obtained ferrite nanoparticles with a high inversion degree of the spinel structure regarding the Fe and Mn, but with all the Zn in the A site. The coating of such nanoparticles with chitosan had no notable effects to the ferrite microstructure. In addition, the polymeric surface can be easily modified with apatite nanocrystals since the hydration of the bio-NCP during synthesis can be controlled. The resulting bio-NCP presents a spherical shape with a narrow size distribution and high magnetic response at room temperature and is a very promising material for early diagnosis of breast cancer and its treatment. © 2013 Elsevier B.V.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Ciências Odontológicas - FOAR

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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

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Pós-graduação em Agronomia (Energia na Agricultura) - FCA

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Pós-graduação em Física - FEG

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)