Novel Highly Luminescent Amine-Functionalized Bridged Silsesquioxanes

authors	Pereira, RFP; Nunes, SC; Toquer, G; Cardoso, MA; Valente, AJM; Ferro, MC; Silva, MM; Carlos, LD; Ferreira, RAS; Bermudez, VD
nationality	International
journal	FRONTIERS IN CHEMISTRY
author keywords	bis[(3-trimethoxysilyl) propyl] amine; sol-gel chemistry; solvent-assisted structuring; morphology; luminescence
keywords	EMISSION RED-SHIFT; MESOPOROUS ORGANOSILICAS; SELF-ORGANIZATION; HYBRID SILICA; SOLVENT; HYDROLYSIS; CONDENSATION; ALKOXYSILANE; MORPHOLOGY; CATALYSTS
abstract	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 = NH2+/= 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.
publisher	FRONTIERS MEDIA SA
issn	2296-2646
year published	2018
volume	5
digital object identifier (doi)	10.3389/fchem.2017.00131
web of science category	Chemistry, Multidisciplinary
subject category	Chemistry
unique article identifier	WOS:000419875000001