Supramolecular Hydrogel Capsules Based on PEG A Step towards Degradable Biomaterials with Rational Design

Supramolecular microgel capsules based on polyethylene glycol PEG are a promising class of soft particulate scaffolds with tailored properties. An approach to fabricate such particles with exquisite control by droplet based microfluidics is presented. Linear PEG precursor polymers that carry bipyridine moieties on both chain termini are gelled by complexation to iron II ions. To investigate the biocompatibility of the microgels, living mammalian cells are encapsulated within them. The microgel elasticity is controlled by using PEG precursors of different molecular weights at different concentrations and the influence of these parameters on the cell viabilities, which can be optimized to exceed 90 is studied. Reversion of the supramolecular polymer cross linking allows the microcapsules to be degraded at mild conditions with no effect on the viability of the encapsulated and released cell

Thiocyanate-free versus thiocyanate-containing dyes for TiO2-based dye-sensitized solar cells

The synthesis and properties of four new ruthenium dyes for TiO2-based dye-sensitized solar cells are presented. Bipyridine ligands with triarylamine or indoline moieties as donors, which differ both in the size of their conjugated systems and in their hydrophobicity, have been introduced into thiocyanate (SCN)-free and SCN-containing complexes. The structural changes affect the absorption and electrochemical properties. Extension of the conjugation leads to a shift in the absorption maximum to longer wavelengths, a broadening of the absorption spectra, and a decrease in the energy of the lowest unoccupied molecular orbital. The efficiency of TiO2-based solar cells that have been sensitized with the new complexes is mainly affected by the adsorption behavior of the dyes. The SCN-containing complex with the less-substituted or extended donor outperforms the other dyes