A carbohydrate-based hydrogel containing vesicles as responsive non-covalent cross-linkers

In this edge article we report the preparation of a supramolecular carbohydrate hydrogel containing cyclodextrin vesicles as 3D junctions. A cellulose polymer is randomly modified with hydrophobic side groups that act as guests for the cyclodextrin hosts on the surface of the vesicles. Hence, the vesicles interconnect the polymer chains into a three-dimensional network and act as multivalent linkages. The resulting gel shows significant shear-thinning and self-healing properties, which make it highly suitable for applications that require injectability. Furthermore, SAXS and cryo-TEM measurements indicate that intact vesicles are present in the gel matrix

Diffusion Limited Photoluminescence Quantum Yields in 1-D Semiconductors: Single-Wall Carbon Nanotubes

Photoluminescence quantum yields and nonradiative decay of the excitonic S-1, state in length fractionated (6,5) single-wall carbon nanotubes (SWNTs) are studied by continuous wave and time-resolved fluorescence spectroscopy. The experimental data are modeled by diffusion limited contact quenching of excitons at stationary quenching sites including tube ends. A combined analysis of the time-resolved photoluminescence decay and the length dependence of photoluminescence quantum yields (PL QYs) from SWNTs in sodium cholate suspensions allows to determine the exciton diffusion coefficient D = 10.7 +/- 0.4 cm(2)s(-1) and lifetime T-pL for long tubes of 20 +/- 1 ps. PL quantum yields Phi(pL) are found to scale with the inverse diffusion coefficient and the square of the mean quenching site distance, here I-d = 120 +/- 25 nm. The results suggest that low PL QYs of SWNTs are due to the combination of high-diffusive exciton mobility with the presence of only a few quenching sites

Size-Selective Permeation of Water-Soluble Polymers through the Bilayer Membrane of Cyclodextrin Vesicles Investigated by PFG-NMR

Cyclodextrin vesicles (CDVs) consist of a bilayer of amphiphilic cyclodextrins (CDs). CDVs exhibit CD cavities at their surface that are able to recognize and bind hydrophobic guest molecules via size-selective inclusion. In this study, the permeability of α- and β-CDVs is investigated by pulsed field gradient-stimulated echo (PFG-STE) nuclear magnetic resonance. Diffusion experiments with water and two types of water-soluble polymers, polyethylene glycol (PEG) and polypropylene glycol (PPG), revealed three main factors that influence the exchange rate and permeability of CDVs. First, the length of the hydrophobic chain of the CD amphiphile plays a crucial role. Reasonably, vesicles consisting of amphiphiles with a longer aliphatic chain are less permeable since both membrane thickness and melting temperature <i>T</i>_m increase. Second, the exchange rate through the bilayer membrane depends on the molecular weight of the polymer and decreases with increasing weight of the polymer. Most interestingly, a size-selective distinction of permeation due to the embedded CDs in the bilayer membrane was found. The mechanism of permeation is shown to occur through the CD cavity, such that depending on the size of the cavity, permeation of polymers with different cross-sectional diameters takes place. Whereas PPG permeates through the membrane of β-CD vesicles, it does not permeate α-CD vesicles

Diffusion Limited Photoluminescence Quantum Yields in 1-D Semiconductors: Single-Wall Carbon Nanotubes

Photoluminescence quantum yields and nonradiative decay of the excitonic S-1, state in length fractionated (6,5) single-wall carbon nanotubes (SWNTs) are studied by continuous wave and time-resolved fluorescence spectroscopy. The experimental data are modeled by diffusion limited contact quenching of excitons at stationary quenching sites including tube ends. A combined analysis of the time-resolved photoluminescence decay and the length dependence of photoluminescence quantum yields (PL QYs) from SWNTs in sodium cholate suspensions allows to determine the exciton diffusion coefficient D = 10.7 +/- 0.4 cm(2)s(-1) and lifetime T-pL for long tubes of 20 +/- 1 ps. PL quantum yields Phi(pL) are found to scale with the inverse diffusion coefficient and the square of the mean quenching site distance, here I-d = 120 +/- 25 nm. The results suggest that low PL QYs of SWNTs are due to the combination of high-diffusive exciton mobility with the presence of only a few quenching sites