Donor-acceptor polyenes of various lengths, and that combine aromatic electron-donating moieties with powerful heterocyclic electron-withdrawing terminal groups, have been synthesized and characterized as efficient nonlinear optical (NLO) chromophores. Their linear and nonlinear optical properties have been investigated, and variations in these properties have been related to ground-state polarization (dipole p ) and structure. In particular, unprecedented quadratic hyperpolarizabilities (p) have been achieved (up to p(0) =I500 x 10-30esu) by reduction of the bondlength alternation (BLA) in the polyenic chain. In each series of homologous com-
3D free‐standing and embedded metallic structures with a height of 100 μm (see Figure and also cover) have been microfabricated and characterized. Polymer nanocomposites containing metal nanoparticles, a metal salt, and an appropriate photoreducing dye are found to be efficient precursors for direct laser writing of continuous metal structures. The authors offer a versatile new approach to the 2D and 3D patterning of metals on different length scales.
The photophysical properties of 6-methoxyquinoline (6MeOQ) and 6-hydroxyquinoline (6HQ) in organic solvents and in neutral, acidic, and alkaline aqueous solutions have been studied by picosecond transient absorption spectroscopy. The dynamics of photoinduced tautomerization by excited state proton transfer(s) arising in the case of 6HQ has been analyzed. Hydroxyl deprotonation of the cationic (quinolinium) form in acidic solution (pH 1.5) is 1 order of magnitude faster (τ dp ∼ 2.2 ps) than imine protonation of the anionic (phenolate) form in 1 M KOH alkaline solution (τ p ∼ 30 ps). In neutral solution, our results suggest a twostep process of initial proton release from the hydroxyl group followed by proton capture by the nitrogen atom with characteristic times close to the τ dp and τ p values, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.