School of Chemistry - Research Publications
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ItemMolecularly isolated perylene diimides enable both strong exciton-photon coupling and high photoluminescence quantum yield(Royal Society of Chemistry, 2019-03-14)Strong coupling in organic media holds the promise of efficient room temperature polariton lasing with solution-processed materials. Currently, however, only five pure-organic materials have been shown to demonstrate polariton lasing. A major challenge is to achieve high exciton–photon coupling while maintaining high photoluminescence quantum yield. Here, we utilize a series of diimide perylene materials that possess sterically hindered substituents, dispersed within a polymer matrix. The rigid structures prevent aggregation and allow high photoluminescence quantum yield (PLQY) at large dye loadings. We demonstrate that these systems can exhibit substantial Rabi splittings at dye loadings that yield film PLQYs of up to 85%, making these perylene derivatives promising materials for polariton lasers.
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ItemHighly Efficient Luminescent Solar Concentrators by Selective Alignment of Donor-Emitter Fluorophores(AMER CHEMICAL SOC, 2019-04-23)Vertically aligning fluorophores to the surface of a waveguide is known to be an effective approach to improve the optical quantum efficiency (OQE) of luminescent solar concentrators (LSCs). While the chromophore alignment assists waveguiding of the emitted photons to the LSC edges, it also significantly reduces the light-harvesting properties of the LSC. We report here a fluorophore pair consisting of a sphere-shaped energy donor and a rod-shaped emitter that was incorporated in LSCs to provide selective fluorophore alignment to address the reduced incident-light absorption issue. A liquid-crystal polymer matrix was used to perpendicularly align the rod-shaped acceptors to a favorable orientation for light guiding, while the sphere-shaped donor was randomly oriented to maintain its light-absorbing properties. The OQE of LSC devices with this selectively aligned donor-acceptor fluorophore system is 78% without significant loss of light-harvesting capability.
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ItemTetrabenzo[5.7]fulvalene: a forgotten aggregation induced-emission luminogen(ROYAL SOC CHEMISTRY, 2019-10-04)Tetrabenzo[5.7]fulvalene, one of the first recognized stable members of mixed fulvalenes, has attracted widespread interest for its remarkable structure. However, little has been known about its photoactivity, most likely owing to its very weak luminescence in the solution state. Here we show for the first time that this compound exhibits aggregation-induced emission (AIE) properties. Its photoluminescence and X-ray crystal structure reveal an interesting mechanism of the AIE phenomenon.
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ItemIntramolecular Versus Intermolecular Triplet Fusion in Multichromophoric Photochemical Upconversion(AMER CHEMICAL SOC, 2019-08-22)Photon upconversion is a process that creates high-energy photons under low photon energy excitation. The effect of molecular geometry on the triplet fusion upconversion process has been investigated in this work through the design and synthesis of four new 9,10-diphenylanthracene (DPA) derivatives by employing platinum octaethylporphyrin as the triplet sensitizer. These new emitter molecules containing multiple DPA subunits linked together via a central benzene core exhibit high fluorescence quantum yields. Interestingly, large differences in the triplet fusion upconversion performance were observed between the derivatives with the meta-substituted dimer showing the closest performance to the DPA reference. The differences are discussed in terms of the statistical probability for obtaining a high-energy singlet excited state from triplet fusion, f, for both inter- and intramolecular processes and the effect of magnetic field on the upconversion efficiency. These results demonstrate the challenges to be overcome in improving triplet fusion upconversion efficiency based on multichromophoric emitter systems.
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ItemTetraphenylethene 9,10-Diphenylanthracene Derivatives - Synthesis and Photophysical Properties(WILEY-V C H VERLAG GMBH, 2019-06)A series of tetraphenylethene 9,10-diphenylanthracene (TPE-DPA) derivatives have been synthesized, and their photophysical properties studied. Photoluminescence measurements in PMMA, neat films and nanoparticle dispersions reveal that different aggregation states are formed, which leads to different photophysical behavior. The triplet excited state properties were studied using Pt(II) octaethylporphyrin (PtOEP) as triplet sensitizer. Upconverted emission from the DPA moiety is observed in nanoparticle dispersions of each derivative. A higher upconverted emission intensity is observed in aerated (compared to deaerated) solutions of the derivatives following irradiation, which is attributed to oxidation of the TPE moiety. These results provide valuable insight for the design of AIE luminogens for triplet-triplet annihilation upconversion (TTA-UC).
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ItemA Maleimide-functionalized Tetraphenylethene for Measuring and Imaging Unfolded Proteins in Cells(WILEY-V C H VERLAG GMBH, 2019-03-15)Collapse of the protein homeostasis (proteostasis) can lead to accumulation and aggregation of unfolded proteins, which has been found to associate with a number of disease conditions including neurodegenerative diseases, diabetes and inflammation. Here we report a maleimide-functionalized tetraphenylethene (TPE)-derivatized fluorescent dye, TPE-NMI, which shows fluorescence turn-on property upon reacting with unfolded proteins in vitro and in live cells under proteostatic stress conditions. The level of unfolded proteins can be measured by flow cytometry and visualized with confocal microscopy.
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ItemFullerene peapod nanoparticles as an organic semiconductor-electrode interface layer(ROYAL SOC CHEMISTRY, 2016)A syndiotactic poly(methyl methacrylate) bottlebrush polymer has been shown to complex with C60 fullerene and assemble into nanoparticles that can be dispersed in polar organic solvents. This composite material was used as an electrode interlayer in organic solar cell (OSC) devices leading to enhanced device performance.
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ItemPlasma deposition of organic polymer films for solar cell applications(ELSEVIER SCIENCE BV, 2016-05)
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ItemAIE conjugated polyelectrolytes based on tetraphenylethene for efficient fluorescence imaging and lifetime imaging of living cells(ROYAL SOC CHEMISTRY, 2017-07-14)
New conjugated polyelectrolytes based on tetraphenylethene are prepared, which show good performance in fluorescence imaging and fluorescence lifetime imaging of living cells.