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.
keywords
EMISSION RED-SHIFT; MESOPOROUS ORGANOSILICAS; SELF-ORGANIZATION; HYBRID SILICA; SOLVENT; HYDROLYSIS; CONDENSATION; ALKOXYSILANE; MORPHOLOGY; CATALYSTS
subject category
Chemistry
authors
Pereira, RFP; Nunes, SC; Toquer, G; Cardoso, MA; Valente, AJM; Ferro, MC; Silva, MM; Carlos, LD; Ferreira, RAS; Bermudez, VD
our authors
Luís Carlos
Full professor
Maria Rute de Amorim e Sá Ferreira André
Vice Director
Marita Alves Cardoso
PhD Student
Marta Ascenção Carmona Ferro
Laboratory OfficerProjects
Luminescent electrochromic devices incorporating organic/inorganic (bio)hybrid electrolytes (LUMECD)
acknowledgements
This work was supported by Fundacao para a Ciencia e a Tecnologia (FCT)/MEC and FEDER (contracts UID/QUI/00616/2013, POCI-01-0145-FEDER-007491, and UID/Multi/00709/2013) and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement, project UniRCell (Ref. SAICTPAC/0032/2015, POCI-01-0145-FEDER-016422), and project LUMECD (Ref. PTDC/CTM/NAN/0956/20149 and POCI-01-0145-FEDER-016884). RP and MC acknowledge FCT for grants SFRH/BPD/87759/2012 and SFRH/BD/118466/2016, respectively. SN also acknowledges FCT for grants SFRH/BPD/63152/2009 and Post-PhD Fellowship of LUMECD project. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT-Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement.