Basic Physicochemical Properties of Polyethylene Glycol Coated Gold Nanoparticles that Determine Their Interaction with Cells.

A homologous nanoparticle library was synthesized in which gold nanoparticles were coated with polyethylene glycol, whereby the diameter of the gold cores, as well as the thickness of the shell of polyethylene glycol, was varied. Basic physicochemical parameters of this two-dimensional nanoparticle library, such as size, ζ-potential, hydrophilicity, elasticity, and catalytic activity ,were determined. Cell uptake of selected nanoparticles with equal size yet varying thickness of the polymer shell and their effect on basic structural and functional cell parameters was determined. Data indicates that thinner, more hydrophilic coatings, combined with the partial functionalization with quaternary ammonium cations, result in a more efficient uptake, which relates to significant effects on structural and functional cell parameters.

Dithienopyrrole as a rigid alternative to the bithiophene π relay in chromophores with second-order nonlinear optical properties.

4H-Pyranylidene-containing push-pull chromophores built around a bithiophene (BT) π relay or a rigidified thiophene-based unit, namely cyclopenta[1,2-b:3,4-b']dithiophene (CPDT) or dithieno[3,2-b:2',3'-d]pyrrole (DTP), have been synthesized and characterized. The effect of these different relays on the polarization and the second-order nonlinear optical (NLO) properties has been studied. For the sake of comparison, the corresponding reported dithieno[3,2-b:2',3'-d]thiophene (DTT) derivatives have also been included in the discussion. Replacement of the BT core by a rigidified unit (CPDT, DTP) leads to more polarized systems. Calculated NBO charges and electrochemical measurements show that dithienopyrrole has a remarkable donor character that allows an important charge transfer between the donor and the acceptor. The influence of the rigidification of the BT relay on the NLO responses depends on the acceptor strength. For the weakest acceptor used (thiobarbituric acid), passing from the BT relay to the rigidified units always involves an increase in the µß0 figure of merit. Nevertheless, for the strongest acceptor (2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF)), a slight increase in µß0 with respect to the BT chromophore is only observed for the DTP derivative. Thus, rigidification of the BT core is not enough to improve the second-order nonlinearity and the incorporation of a DTP moiety has proven to be the most efficient approach for this purpose.

Synthesis, characterization, and optical properties of 4H-pyran-4-ylidene donor-based chromophores: the relevance of the location of a thiophene ring in the spacer.

A series of new 4H-pyran-4-ylidene donor-based chromophores with a thiophene ring in the spacer has been synthesized. The linear and nonlinear optical (NLO) properties of these compounds have been determined and compared with the results of computational calculations. The position of the thiophene ring proved essential to optimize the figure of merit µß, with the best results obtained when the heterocyclic system was closer to the donor moiety.

4H-Pyran-4-ylidenes: strong proaromatic donors for organic nonlinear optical chromophores.

Merocyanines where a polyenic spacer separates a 4H-pyran-4-ylidene moiety and different strong organic acceptors have been synthesized. According to NMR studies and X-ray diffraction data, these compounds have weakly alternated structures and remarkably zwitterionic ground states, with a partial aromatic character that is compared to those of other pyran derivatives. The proaromaticity of the 4H-pyran-4-ylidene donor lies behind the cyanine-like behavior and low (positive or negative) second-order optical nonlinearities of the shorter derivatives. On the other hand, lengthening the pi-spacer gives rise to rapidly increasing mubeta(1907) values up to 17,400 x 10(-48) esu.