Upon exchanging long chain alkylamine ligands with a carbazole terminated fatty acid as 6-(N-carbazolyl)-hexanoic acid (C6) and 11-(N-carbazolyl) undecanoic acid (C11), efficient photoluminescence (PL) of CdSe/ZnS colloidal quantum dots (QDs) was observed upon excitation in the absorption band of the carbazole moiety at 330 nm. This effect, which occurred both in solution and in a poly(N-vinylcarbazole) (PVK) matrix doped with the QDs, is attributed to sensitization of the QDs by PVK and the ligands. More efficient energy transfer was observed in solution for the shorter ligand (C6) capped QDs, due to a shorter average distance between the donor (carbazole) and the acceptor (QD). The binding of C6 and C11 to the QDs was confirmed by 1H solution nuclear magnetic resonance, which showed line broadening of the carbazole signal due to a decrease of the mobility of the carbazoles upon binding to the QDs compared with the sharp lines observed for the free molecules in solution. In doped PVK films, the significant enhancement of the energy transfer to the QD core could also be related to a better miscibility between the QDs and the PVK as confirmed by optical transmission and confocal microscopy images. In contrast to the experiment in solution, the overall energy transfer in the doped films was found more efficient for QDs capped with C11. To study in more detail the energy transfer between the carbazole moieties and the QDs, time-resolved fluorescence measurements were performed for solutions of C6 and C11, capped QDs and PVK films doped with the QDs. In contrast to the large enhancement of the QD emission indicated by steady-state PL spectra, the latter experiments suggested only a relatively low efficiency (19.6% and 10.8%) for singlet transfer from the carbazole ligands to the QDs. This suggests that the enhancement of the QD emission must be largely due to triplet transfer.

A new synthesis method for preparing spherosilicates with a double-four-ring (D4R) silicate core (Si8O12) and functional siloxy substituents such as (OSi­(CH3)2Cl) on the vertices was discovered. Key to this achievement was the synthesis of [N­(n-C4H9)4]­H7[Si8O20]·5.33H2O D4R cyclosilicate hydrate precursor crystals having only 5.33 water molecules per D4R unit, which is much smaller than the number in the state-of-the-art tetramethylammonium- and choline-containing cyclosilicate hydrate crystals that have up to 65 water molecules per D4R. The low water content allows the use of bifunctional silylating agents such as dichlorodimethylsilane that lose their chloride functionality upon reaction with water molecules. Dissolution of [N­(n-C4H9)4]­H7[Si8O20]·5.33H2O crystals in acidified tetrahydrofuran liberates uncharged D4R [Si8O12]­[OH]8 cyclosilicate molecules, as shown by small angle X-ray scattering and 29Si nuclear magnetic resonance. A concentrated stable solution of [Si8O12]­[OSi­(CH3)2Cl]8 spherosilicate compound was obtained by silylation with Cl2(CH3)2Si. It is a unique way to prepare a stable solution of this attractive spherosilicate with dimethylsilyl chloride chemical functionality suited for derivatization or hybrid material synthesis. With the change in the silylating agent, the new synthesis pathway allows the quantitative synthesis of other spherosilicates such as [Si8O12]­[OSi­(CH3)2H]8 with high yield and purity.

Magnetohydrodynamic mixing yields carbomer dispersions with higher viscosity and higher storage modulus as compared to high shear mixing. 1H NMR reveals molecular level differences in water distribution, polymer degradation and charge stabilization.

Arabinoxylan oligosaccharides (AXOS) are a complex mixture of cereal derived, water soluble prebiotics, obtained by enzymatic hydrolysis of arabinoxylan, a group of dietary fibers exerting numerous nutritional and health-beneficial effects. Such complex biomolecular mixtures are notoriously difficult to characterize without initial physical fractionation. Here we present the in situ analysis of AXOS using a variety of state-of-the-art sensitivity-enhanced 13 C-DOSY methods, enabling virtual separation and identification of the components. Three dimensional correlation plots displaying 13 C diffusivity (DOSY), relaxation parameters (TOSY) and chemical shift offer a unique way to elucidate the composition of mixtures. We have demonstrated this multifaceted 13 C probed correlation strategy in standard mixtures of aliphatic and aromatic compounds, before implementing it on AXOS. These 3D-DOSY-TOSY plots in combination with 2D-NMR correlation experiments offer unprecedented clarity for assigning chemical functions, molecular size distribution and dynamics of oligosaccharide mixtures.

Upon liquid phase adsorption of C1-C5 primary alcohols on high silica MFI zeolites (Si/Al = 11.5-140), the concentration of adsorbed molecules largely exceeds the concentration of traditional adsorption sites: Brønsted...