The first successful approach to synthesizing ultrabright fluorescent mesoporous silica nanoparticles is reported. Fluorescent dye is physically entrapped inside nanochannels of a silica matrix created during templated sol-gel self-assembly. The problem of dye leakage from open channels is solved by incorporation of hydrophobic groups in the silica matrix. This makes the approach compatible with virtually any dye that can withstand the synthesis. The method is demonstrated using the dye Rhodamine 6G. The obtained 40-nm silica particles are about 30 times brighter than 30-nm coated water-soluble quantum dots. The particles are substantially more photostable than the encapsulated organic dye itself.

The synthesis of ultrabright fl uorescent mesoporous silica nanoparticles (UFSNPs) of various sizes loaded with different amounts of fl uorescent dye (Rhodamine 6G) is reported here. The dye is physically entrapped inside the nanochannels of the silica matrix created during templated sol-gel self assembly. Due to the specifi c nanoenvironment, the fl uorescence of the encapsulated dye molecules remains unquenched up to very high concentrations, which results in relatively high fl uorescence. The particle size (ranging from 20-50 nm) and dye loading (0.8-9.3 mg dye per g particles) are controlled by the timing of the synthesis and the concentration of several organotriethoxysilanes, which are coprecursors of silica. The quantum yields of the encapsulated dye range from 0.65 to 1.0. The relative brightness of a single particle is equivalent to the fl uorescence of 30-770 free nondimerized R6G dye molecules in water, or to that of 1.5-39 CdSe/ZnS quantum dots. Despite the presence of some hydrophobic groups on the particles' surfaces, colloidal suspensions of the particles are relatively stable (as monitored for 120 days).

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Hydrothermally stable mesoporous ethanesilica with a long-range hexagonal order (p6mm) and a relatively thick and micropore-free framework wall was synthesized by the core−shell approach using a nonionic PEO−PLGA−PEO triblock copolymer template and a 1,2-bis(triethoxysilyl)ethane (BTESE) organosilica precursor. The pore structure and morphology were characterized by SAXS, TEM, BET, and solid-state NMR measurement. The key parameters in the synthesis of mesoporous ethanesilica with a stable thick wall are the strong contrast between the hydrophilic PEO block and the hydrophobic PLGA block and the compatibility of PEO with the BTESE organosilicate precursor at an optimum reaction temperature of 323 K. The enhanced hydrothermal stability (i.e., the structural integrity was maintained for up to 25 days in boiling water of 373 K) is believed to be due to the thick pore wall (4.2 nm), the high degree of condensation and hydrophobicity of organosilica precursor used, and the significant reduction of micropores.

CO2 adsorption was investigated on amine-functionalized mesoporous silica (SBA-15) and periodic mesoporous organosilica (PMO) samples. Hexagonally (p6mm) ordered mesoporous SBA-15 and benzene-PMO (BPMO) samples were prepared in the presence of Pluronic P123 block copolymer template under acidic conditions. Three kinds of amine-containing organosilanes and polyethylenimine were used to functionalize SBA-15 and BPMO. Small-angle X-ray scattering and nitrogen adsorption isotherms showed that these samples featured ordered mesostructure, high surface area, and narrow pore size distributions. Solid-state (13)C- and (29)Si cross-polarization magic-angle spinning NMR spectra showed chemical linkage between amine-containing modifiers and the surface of mesoporous materials. The chemically linked amine-containing modifiers were found to be on both the inner and outer surfaces. N-[3-(trimethoxysilyl)propyl]ethylenediamine-modified BPMO (A2-BPMO) sample exhibited the highest CO2 uptake (i.e., ∼3.03 mmol/g measured on a volumetric adsorption analyzer) and the fastest adsorption rate (i.e., ∼13 min to attain 90% of the maximum amount) among all the samples studied. Selectivity and reproducibility measurements for the A2-BPMO sample showed quite good performance in flowing N2 gas at 40 mL/min and CO2 gas of 60 mL/min at 25 °C.