Publicação
Electron microscopy and spectroscopy study of modified titanate nanowires and nanotubes
| Resumo: | One dimensional titanate nanostructures, such as titanate nanowires (TNWs) and nanotubes (TNTs), are promising alternatives to TiO2 in various applications including photocatalysis. They combine the properties of TiO2 nanoparticles with the properties of layered titanates such as ion exchange ability and higher speci c surface area, due to their open mesoporous morphology. In this thesis, investigations on cobalt doped and intercalated titanate nanowires and nanotubes using various characterization techniques are presented. Aberration corrected electron microscopy along with energy dispersive x-ray spectroscopy (EDX), is employed to ascertain the morphology, structure and chemical composition of the titanate nanostructures. In order to minimize electron beam induced damage, electron microscopy was carried out at 80 kV. EDX mapping revealed the distribution of the various elements including the dopant intercalant cobalt in both nanotubes and nanowires. L3/ L2 white line ratio in energy loss spectroscopy (EELS) is used to determine the oxidation state of cobalt in the modi ed titanate nanostructures, from single nanowire/nanotube. This analysis indicates the presence of cobalt in mixed oxidation state (2+ and 3+) in doped samples and 2+ oxidation state in intercalated samples. These findings were further confirmed by X-ray photoelectron spectroscopy (XPS) measurements. Raman analysis showed notable changes in the characteristic Raman peaks in the case of cobalt doped and intercalated titanate nanowires and nanotubes in comparison to the reference titanate nanowires and nanotubes. Cobalt incorporation was better achieved in the intercalated TNT and TNW samples in comparison to that of doped TNTs and TNWs. The findings in this work are very relevant because they can contribute to better understand, and even anticipate, the performance of such metal modified nanostructures, since they make possible to relate the performance with the amount, position and oxidation state of the metal in the nanostructure. |
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| Autores principais: | Sathyanath, Sharath Kumar Manjeshwar |
| Ano: | 2018 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | One dimensional titanate nanostructures, such as titanate nanowires (TNWs) and nanotubes (TNTs), are promising alternatives to TiO2 in various applications including photocatalysis. They combine the properties of TiO2 nanoparticles with the properties of layered titanates such as ion exchange ability and higher speci c surface area, due to their open mesoporous morphology. In this thesis, investigations on cobalt doped and intercalated titanate nanowires and nanotubes using various characterization techniques are presented. Aberration corrected electron microscopy along with energy dispersive x-ray spectroscopy (EDX), is employed to ascertain the morphology, structure and chemical composition of the titanate nanostructures. In order to minimize electron beam induced damage, electron microscopy was carried out at 80 kV. EDX mapping revealed the distribution of the various elements including the dopant intercalant cobalt in both nanotubes and nanowires. L3/ L2 white line ratio in energy loss spectroscopy (EELS) is used to determine the oxidation state of cobalt in the modi ed titanate nanostructures, from single nanowire/nanotube. This analysis indicates the presence of cobalt in mixed oxidation state (2+ and 3+) in doped samples and 2+ oxidation state in intercalated samples. These findings were further confirmed by X-ray photoelectron spectroscopy (XPS) measurements. Raman analysis showed notable changes in the characteristic Raman peaks in the case of cobalt doped and intercalated titanate nanowires and nanotubes in comparison to the reference titanate nanowires and nanotubes. Cobalt incorporation was better achieved in the intercalated TNT and TNW samples in comparison to that of doped TNTs and TNWs. The findings in this work are very relevant because they can contribute to better understand, and even anticipate, the performance of such metal modified nanostructures, since they make possible to relate the performance with the amount, position and oxidation state of the metal in the nanostructure. |
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