Publications by authors named "Jayeon Hong"

2 Publications

  • Page 1 of 1

Chiral polymer hosts for circularly polarized electroluminescence devices.

Chem Sci 2021 Jul 21;12(25):8668-8681. Epub 2021 May 21.

Division of Chemical Engineering and Materials Science, Graduate Program in System Health Science and Engineering, Ewha Womans University Seoul 03760 Republic of Korea

Polymer electroluminescence devices producing circularly polarized luminescence (CP PLEDs) have valuable photonic applications. The fabrication of a CP PLED requires a polymer host that provides the appropriate chiral environment around the emitting dopant. However, chemical strategies for the design of chiral polymer hosts remain underdeveloped. We have developed new polymer hosts for CP PLED applications. These polymers were prepared through a free-radical polymerization of 3-vinylcarbazole with a chiral -alkyl unit. This chiral unit forces the carbazole repeat units to form mutually helical half-sandwich conformers with preferred ()-helical sense along the polymer main chain. Electronic circular dichroism measurements demonstrate the occurrence of chirality transfer from chiral monomers to achiral monomers during chain growth. The ()-helical-sense-enriched polymer interacts diastereoselectively with an enantiomeric pair of new phosphorescent ()- and ()-dopants. The magnitude of the Kuhn dissymmetry factor ( ) for the ()-helically-enriched polymer film doped with the ()-dopant was found to be one order of magnitude higher than that of the film doped with the ()-dopant. Photoluminescence dissymmetry factors ( ) of the order of 10 were recorded for the doped films, but the magnitude of diastereomeric enhancement decreased to that of . The chiral polymer host permits faster energy transfer to the phosphorescent dopants than the achiral polymer host. Our photophysical and morphological investigations indicate that the acceleration in the chiral polymer host is due to its longer Förster radius and improved compatibility with the dopants. Finally, multilayer CP PLEDs were fabricated and evaluated. Devices based on the chiral polymer host with the ()- and ()-dopants exhibit electroluminescence dissymmetry factors ( ) of 1.09 × 10 and -1.02 × 10 at a wavelength of 540 nm, respectively. Although challenges remain in the development of polymer hosts for CP PLEDs, our research demonstrates that chiroptical performances can be amplified by using chiral polymer hosts.
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July 2021

Deep-Red-Fluorescent Zinc Probe with a Membrane-Targeting Cholesterol Unit.

Inorg Chem 2020 Aug 27;59(16):11562-11576. Epub 2020 Jul 27.

Division of Chemical Engineering and Materials Science, Ewha Womans University, Seoul 03760, Republic of Korea.

Organelle-targeting fluorescence probes are valuable because they can provide spatiotemporal information about the trafficking of analytes of interest. The spatiotemporal resolution can be improved by using low-energy emission signals because they are barely contaminated by autofluorescence noises. In this study, we designed and synthesized a deep-red-fluorescent zinc probe (JJ) with a membrane-targeting cholesterol unit. This zinc probe consists of a boron-azadipyrromethene (aza-BODIPY) fluorophore and a zinc receptor that is tethered to a tri(ethylene glycol)-cholesterol chain. In aqueous solutions buffered to pH 7.4, JJ exhibits weak fluorescence with a peak wavelength of 663 nm upon excitation at 622 nm. The addition of ZnCl elicits an approximately 5-fold enhancement of the fluorescence emission with a fluorescence dynamic range of 141000. Our electrochemical and picosecond transient photoluminescence investigations indicate that the fluorescence turn-on response is due to the zinc-induced abrogation of the formation of a nonemissive intramolecularly charge-separated species, which occurs with a driving force of 0.98 eV. The fluorescence zinc response was found to be fully reversible and to be unaffected by pH changes or the presence of biological metal ions. These properties are due to tight zinc binding with a dissociation constant of 4 pM. JJ was found to be nontoxic to HeLa cells up to submicromolar concentrations, which enables cellular imaging. Colocalization experiments were performed with organelle-specific stains and revealed that JJ is rapidly internalized into intracellular organelles, including lysosomes and endoplasmic reticula. Unexpectedly, probe internalization was found to permeabilize the cell membrane, which facilitates the influx of exogens such as zinc ions. Such permeabilization does not arise for a control probe without the tri(ethylene glycol)-cholesterol chain (JJC). Our results show that the membrane-targeting cholesterol unit can disrupt membrane integrity.
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August 2020