Dissymmetric Chiral Poly(diphenylacetylene)s: Secondary Structure Elucidation and Dynamic Luminescence.

The secondary structure of a dissymmetric and chiral poly(diphenylacetylene) (PDPA) is elucidated by combining the data from NMR experiments (regioregular head to tail structure), Raman and IR studies (E configuration of the polyene double bonds), and high-resolution AFM images (helical pitch, packing angle and orientation of the external helix). As a result, an E-transoidal polyene backbone describing three coaxial helices is obtained. Theoretical electronic circular dichroism (ECD) studies of the structure show a good correspondence between experimental and theoretical data and allow one to decipher that the first Cotton band is generated by the poly(diphenylacetylene) core and not only by the polyene backbone. The dynamic behavior of poly-(S)-2 is also demonstrated by a helix inversion effect produced by conformational changes at the pendant groups when annealed in solvents with different donor abilities. This phenomenon is accompanied by an inversion of the circular polarized luminescence of the PDPA (CPL switch).

Redox luminescence switch based on Mn2+ -doped NaYF4 :Yb,Er upconversion nanorods.

An redox luminescence switch was developed for the sensing of glutathione (GSH), l-cysteine (Cys) or l-ascorbic acid (AA) based on redox reaction. The Mn2+ -doped NaYF4 :Yb,Er upconversion nanorods (UCNRs) with an emission peak located in the red region were synthesized. The luminescence intensity of the UCNRs could be quenched due to the Mn2+ could be oxidized to MnO2 by KMnO4 . Subsequently, when the AA, GSH or Cys was added into the MnO2 modified upconversion nanosystem, which could reduced MnO2 to Mn2+ and the luminescence intensity was recovered. The concentration ranges of the nanosystem are 0.500-3.375 mM (R2  = 0.99) for AA, 0.6250-11.88 mM (R2  = 0.99) for GSH and 0.6250-9.375 mM (R2  = 0.99) for Cys, respectively.

Multistimuli-Responsive Lanthanide-Containing Smart Luminescent Hydrogel Actuator.

Stimuli-responsive hydrogels are flourishing; however, a multiresponsive luminescent hydrogel actuator in which the stimuli do not interfere with each other is still difficult to produce. Here, a smart luminescent bilayer hydrogel actuator with shape memory and reversible luminescence switch behaviors under the co-stimulation of pH and heating is reported. Under alkaline condition, chitosan-containing layer generates physical microcrystals to fix the temporary shape of the actuator while lanthanide emits bright luminescence. Upon acid treatment, the actuator recovers to its original shape and the luminescence is quenched since the "antenna effect" between organic ligand and lanthanide ions is disrupted. It is to be noticed that this multiresponsive cycle can be repeated several times without interfering each other. This work is expected to have potential application prospects in the fields of biomimetic soft robots, sensors, and camouflage.