Author(s): Pereira, Rui F. P. ; Nunes, Sílvia C ; Toquer, Guillaume ; Cardoso, Marita A ; Valente, Artur J. M. ; Ferro, Marta C. ; Silva, Maria M. ; Carlos, Luís D. ; Ferreira, Rute A. Sá ; de Zea Bermudez, Verónica
Date: 2017
Persistent ID: https://hdl.handle.net/10316/107607
Origin: Estudo Geral - Universidade de Coimbra
Subject(s): bis[(3-trimethoxysilyl)propyl]amine; luminescence; morphology; sol-gel chemistry; solvent-assisted structuring
Amine-functionalized bridged silsesquioxanes (BSs) were synthesized from bis[(3-trimethoxysilyl)propyl] amine via a solvent-mediated route. BS-1 and BS-2 were obtained at neutral pH with sub- and stoichiometric amounts of water, respectively, and high tetrahydrofuran content. BS-3 was prepared with hyperstoichiometric water concentration, high tetrahydrofuran content, and hydrochloric acid. BS-4 was synthesized with hyperstoichiometric water concentration, high ethanol content, and sodium hydroxide. BS-1 and BS-2 were produced as transparent films, whereas BS-3 and BS-4 formed white powders. Face-to-face stacking of flat or folded lamellae yielded quasi-hydrophobic platelets with emission quantum yields of 0.05 ± 0.01 (BS-1 and BS-2) or superhydrophilic onion-like nanoparticles with exciting emission quantum yields of 0.38 ± 0.03 (BS-3) and 0.33 ± 0.04 (BS-4), respectively. The latter two values are the largest ever reported for amine-functionalized siloxane-based hybrids lacking aromatic groups. Fast Grotthus proton hopping between = [Formula: see text]/ = NH groups (BS-3) and = N-/ = NH groups (BS-4), promoted by H+ and OH- ions, respectively, and aided by short amine-amine contacts provided by the onion-like morphology, account for this unique optical behavior.
