Propriedades estruturais e vibracionais de nanocristais de TiO2 dispersos em matriz vítrea porosa / Vibrational and structural properties of TiO2 nanocrystals dispersed into porous glass matrix
AUTOR(ES)
Bartolomeu Cruz Viana Neto
DATA DE PUBLICAÇÃO
2006
RESUMO
Nanostructured materials are the subject of intense investigation due to their remarkable properties as compared their bulk counterparts. The size-induced phenomena are interesting their own and open unique opportunities not only for using these properties in novel applications but also for improving the current technology. In this scenario integrated chemical systems (ICS) are set apart owing their complexity and the possibility ofcombining diferent nanosystems for getting materials with a designed functionality. For instance, nanocrystal growth in the cavities of a porous host is an attractive ICS because the porous is a restricted environment that can be used as nanoreactors. Besides the such system is very promising for catalysis it also important for studying the size-induced properties of the guest material as well. In this work we report the study of vibrational and structural properties of TiO2 nanocrystals dispersed into a porous vycor glass. We have obtained very small TiO2 nanocrystals in the anatase form. The nanocrystal size is controlled via the mass increment only thus preventing the growth through the coalescence process. The nanocrystal size as monitored through transmission electron microscope and Raman scattering. The Eg lowest frequency mode experiences an upshift and becomes broader as the nanocrystal size decreases. This phenomena is attributed to a size-induced eect and we analyzed it based on a phonon connement model. As the nanocrystal size gets smaller the q = 0 selection rule is relaxed and the phonon connement involves large q values contribute to the Raman intensity. The frequency follows the same trend of the phonon dispersion relation for the TiO2 bulk as the nanocrystal size decreases.
ASSUNTO(S)
tio2 nanocrystals photocatalysis espectroscopia raman fisica da materia condensada fotocatálise raman spectroscopy nanocristais de tio2
ACESSO AO ARTIGO
http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=45Documentos Relacionados
- TiO2 nanocrystals: relationship between morphological, structural parameters and photocatalysis
- Synthesis of TIO2 colloidal nanocrystals by solvothermal method
- EFEITO DE TiO2 K2O , E Na2 FASE VÍTREA E NAS PROPRIEDADES DE PORCELANAS TRIAXIAIS.
- Photocatalytic activity of TiO2 in siloxane matrices
- Estudo das propriedades acusticas do filme finode TiO2 usando SAW