Influência do método de síntese nas propriedades fotocatalíticas e fotoluminescentes do Ca1-xInxWO4
CaWO4 is a semiconductor that is currently being investigated for having good optical properties. These properties are related to some processing factors such as different synthesis methods that generate distinct crystal structures and morphologies. Such morphological and structural characteristi...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/47516 |
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| Resumo: | CaWO4 is a semiconductor that is currently being investigated for having good
optical properties. These properties are related to some processing factors such as
different synthesis methods that generate distinct crystal structures and morphologies.
Such morphological and structural characteristics will certainly affect the properties of
the synthesized material. In this work, the photocatalytic and photoluminescent properties
of CaWO4 doped with indium (0, 1, 2, 4 and 8% mol) were investigated for 30 minutes
by two different methods: the sonochemical method (MS) and the microwave-assisted
hydrothermal method (MHAM). The crystal structures of the pure and doped samples and
their morphologies were characterized by X-ray diffraction (XRD) and by field emission
scanning electron microscopy (MEV-FEG), respectively. The photocatalytic activity was
estimated from the degradation of methylene blue (MB) dye under UV light. CaWO4
powders were tested in 3 cycles of reuse. Optical and photoluminescence properties were
estimated from UV-Visible spectroscopy and the photoluminescence (FL) test. The
diffractograms indicated no formation of secondary phases and the Rietveld refinement
estimated the crystallite sizes where the samples synthesized by MS obtained a crystallite
size of 31,85 nm for the pure sample which varied to 31,23 nm with a maximum doping
(8% of In). For the samples synthesized by MHAM, the crystallite size varied between
35,98 nm for the pure sample and 36,73 nm for the 8% In sample. The average crystallite
sizes of MS and MHAM samples were 33.51 and 34.69 nm, respectively. The SEM-FEG
images indicated a clustered morphology with an irregular shape and in the form of rods
and kibes. The photocatalytic activity increased in efficiency with increasing doping, and
the samples doped with 4 and 8% of indium in each synthesis were the samples that
showed the best photocatalytic efficiencies and the lowest bandgaps values. The sample
synthesized by the hydrothermal method showed the smallest loss of efficiency during
the 3 cycles of reuse, being the best alternative for applications in photocatalysis. The
samples with 8% of In+3 ions showed lower FL intensities with maximum peak at 479 and
483 nm suggesting that there is a lower recombination pair e-/h+, which led these samples
to have a better photocatalytic performance. |
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