abstract
Transparent monoliths and films of urea cross-linked tripodal siloxane-based hybrids (named tri-ureasils) were prepared by the sol-gel process, under controlled atmosphere (inside a glove box) and ambient conditions and their structure and optical features were compared. X-ray diffraction data point out that all the materials are essentially amorphous and Si-29 NMR reveal an increase in the condensation degree (0.97) for the hybrids prepared under controlled atmosphere relatively to that found for those prepared under ambient conditions (0.84-0.91). The tri-ureasils are white light emitters under UV/Visible excitation (from 250 to 453 nm) being observed for the composites prepared inside the glove box a significant enhancement (60-80 %) of the absorption coefficient and higher emission quantum yield values (similar to 0.27 and similar to 0.20 for monoliths and films, respectively) relatively to those synthesized under ambient condition.
keywords
ORGANIC-INORGANIC NANOCOMPOSITES; CARBOXYLIC-ACID SOLVOLYSIS; METAL ACTIVATOR IONS; BRIDGED SILSESQUIOXANES; ORGANIC/INORGANIC HYBRIDS; LIGHT-EMISSION; TUNABLE PHOTOLUMINESCENCE; LAMELLAR STRUCTURE; ENERGY-TRANSFER; SILICA SPHERES
subject category
Materials Science
authors
Freitas, VT; Lima, PP; Ferreira, RAS; Carlos, LD; Pecoraro, E; Ribeiro, SJL; Bermudez, VD
our authors
Luís Carlos
Full professor
Maria Rute de Amorim e Sá Ferreira André
Full professor
Patrícia Pereira Lima
Post-doc Fellowship
Vânia Patrícia Castro Teixeira Freitas
Research FellowshipProjects
acknowledgements
This work was financed by FEDER, COMPETE, and FCT (PEst-C/CTM/LA0011/2013, PTDC/CTM/101324/2008, PTDC/CTM-BPC/112774/2009), COST Action MP1202