Novel Highly Luminescent Amine-Functionalized Bridged Silsesquioxanes

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.

Ionic Liquid-Assisted Synthesis of Mesoporous Silk Fibroin/Silica Hybrids for Biomedical Applications

“…Comparison of the experimental conditions employed for the synthesis of samples H1, H2, and H4 (Table S1) leads us to suggest that the simultaneous use of a high concentration of HCl and the incorporation of NaOH may have caused the collapse of H2. The combined use of an acid and basic catalysts was expected to alter the kinetics of the sol–gel reactions (hydrolysis and condensation) of the TMOS precursor and ultimately affect the structure, morphology, and dimensional stability of the resulting material. , In general, the condensation reactions are rate-limiting in acid medium and the hydrolysis reaction is rate-limiting in basic media . Comparison of the synthesis procedures employed for the preparation of H3, H4, H3′, and H4′ (Table S1) strongly suggests that the curing process, the final step of the synthesis, was too long in the case of the latter two samples, presumably leading to the formation of cracks and ultimately to the disintegration of the xerogels.…”

Self-catalyzed Gelling Synthesis of Aerogels with Inorganic and Organic Nanocomponents for Thermal Insulation and CO2 Capture

“…Owing to the high alkalinity of amine groups from BTPA, the methoxyl groups can be swiftly hydrolyzed to produce active silicon hydroxyl groups in the presence of water. As the dehydration and condensation reactions progress, an interconnected skeleton is formed, and the phase separation between the solvent and the skeleton happens to form a gel . The hydrolysis reaction occurs rapidly for BTPA and MTES to form a homogeneous sol (Figure b).…”

“…As the dehydration and condensation reactions progress, an interconnected skeleton is formed, and the phase separation between the solvent and the skeleton happens to form a gel. 36 The hydrolysis reaction occurs rapidly for BTPA and MTES to form a homogeneous sol (Figure 1b). Then, the alkalinity continues to catalyze the dehydration polycondensation reaction to build a developed nanoporous architecture.…”