School of Chemistry - Research Publications
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ItemContinuous Flow Synthesis of Conjugated Polymers and Carbon Materials(WILEY-V C H VERLAG GMBH, 2017)The basic equipment associated with the synthesis of chemicals in the laboratory has remained essentially unchanged since the establishment of chemistry as a scientific discipline. Most techniques and apparatus are optimized for batch-by-batch processes. These traditional batch techniques have the benefit of familiar and time-tested methodology and low up-front cost, and therefore the shift to more modern apparatus requires some additional motivating factors. Continuous flow processing is a technique which involves a nontrivial initial investment of both time and finances, but which offers significant benefits to synthetic chemists. Continuous flow processing has been increasing in prominence in the research laboratory setting in the last decade, and a number of research groups now specialize in the development of methods for flow processing. This progress is buoyed by the commercial availability of the associated equipment, which can now be purchased from several vendors.
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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.
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ItemThe synthesis and purification of amphiphilic conjugated donor-acceptor block copolymers(NATURE PUBLISHING GROUP, 2017-01)
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ItemA Green Route to Conjugated Polyelectrolyte Interlayers for High‐Performance Solar Cells(Wiley, 2017-07-10)Abstract Synthesis of fluorene‐based conjugated polyelectrolytes was achieved via Suzuki polycondensation in water and completely open to air. The polyelectrolytes were conveniently purified by dialysis and analysis of the materials showed properties expected for fluorene‐based conjugated polyelectrolytes. The materials were then employed in solar cell devices as an interlayer in conjunction with ZnO. The double interlayer led to enhanced power conversion efficiency of 10.75 % and 15.1 % for polymer and perovskite solar cells, respectively.
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ItemHoch fluoreszierende Pyridiniumbetaine für die Lichtsammlung(Wiley, 2017-10-23)Abstract Die Ergebnisse experimenteller und theoretischer Untersuchungen der Eigenschaften von Pyridiniumenolaten werden vorgestellt, und ihre potenzielle Nutzbarkeit in Lichtsammelanwendungen, insbesondere lumineszierenden Solarkonzentratoren (LSCs), wird demonstriert. Synthesen, Strukturen, photophysikalische Charakterisierung und wellenfunktionsbasierte quantenchemische Studien für fünf Cyclobetaine werden präsentiert und die Leistungsfähigkeit einer LSC‐Apparatur, die eines dieser Cyclobetaine enthält, wird mit dem aktuellen Stand der Technik verglichen.
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ItemEmissive Molecular Aggregates and Energy Migration in Luminescent Solar Concentrators(American Chemical Society, 2017-01-17)Luminescent solar concentrators (LSCs) are light harvesting devices that are ideally suited to light collection in the urban environment where direct sunlight is often not available. LSCs consist of highly luminescent compounds embedded or coated on a transparent substrate that absorb diffuse or direct solar radiation over a large area. The resulting luminescence is trapped in the waveguide by total internal reflection to the thin edges of the substrate where the concentrated light can be used to improve the performance of photovoltaic devices. The concept of LSCs has been around for several decades, and yet the efficiencies of current devices are still below expectations for commercial viability. There are two primary challenges when designing new chromophores for LSC applications. Reabsorption of dye emission by chromophores within the waveguide is a significant loss mechanism attenuating the light output of LSCs. Concentration quenching, particularly in organic dye systems, restricts the quantity of chromophores that can be incorporated in the waveguide thus limiting the light absorbed by the LSC. Frequently, a compromise between increased light harvesting of the incident light and decreasing emission quantum yield is required for most organic chromophore-based systems due to concentration quenching. The low Stokes shift of common organic dyes used in current LSCs also imposes another optimization problem. Increasing light absorption of LSCs based on organic dyes to achieve efficient light harvesting also enhances reabsorption. Ideally, a design strategy to simultaneously optimize light harvesting, concentration quenching, and reabsorption of LSC chromophores is clearly needed to address the significant losses in LSCs. Over the past few years, research in our group has targeted novel dye structures that address these primary challenges. There is a common perception that dye aggregates are to be avoided in LSCs. It became apparent in our studies that aggregates of chromophores exhibiting aggregation-induced emission (AIE) behavior are attractive candidates for LSC applications. Strategic application of AIE chromophores has led to the development of the first organic-based transparent solar concentrator that harvests UV light as well as the demonstration of reabsorption reduction by taking advantage of energy migration processes between chromophores. Further developments led us to the application of perylene diimides using an energy migration/energy transfer approach. To prevent concentration quenching, a molecularly insulated perylene diimide with bulky substituents attached to the imide positions was designed and synthesized. By combining the insulated perylene diimide with a commercial perylene dye as an energy donor–acceptor emitter pair, detrimental luminescence reabsorption was reduced while achieving a high chromophore concentration for efficient light absorption. This Account reviews and reinspects some of our recent work and the improvements in the field of LSCs.
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ItemA Green Route to Conjugated Polyelectrolyte Interlayers for High-Performance Solar Cells(Wiley, 2017-07-10)Synthesis of fluorene‐based conjugated polyelectrolytes was achieved via Suzuki polycondensation in water and completely open to air. The polyelectrolytes were conveniently purified by dialysis and analysis of the materials showed properties expected for fluorene‐based conjugated polyelectrolytes. The materials were then employed in solar cell devices as an interlayer in conjunction with ZnO. The double interlayer led to enhanced power conversion efficiency of 10.75 % and 15.1 % for polymer and perovskite solar cells, respectively.
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ItemDeterminants of the efficiency of photon upconversion by triplet-triplet annihilation in the solid state: zinc porphyrin derivatives in PVA(ROYAL SOC CHEMISTRY, 2017-09-14)Spectroscopic, photophysical and computational studies designed to expose and explain the differences in the efficiencies of non-coherent photon upconversion (NCPU) by triplet-triplet annihilation (TTA) have been carried out for a new series of alkyl-substituted diphenyl and tetraphenyl zinc porphyrins, both in fluid solution and in solid films. Systematic variations in the alkyl-substitution of the phenyl groups in both the di- and tetraphenyl porphyrins introduces small, but well-understood changes in their spectroscopic and photophysical properties and in their TTA efficiencies. In degassed toluene solution TTA occurs for all derivatives and produces the fluorescent S2 product states in all cases. In PVA matrices, however, none of the di-phenylporphyrins exhibit measurable NCPU whereas all the tetraphenyl-substituted compounds remain upconversion-active. In PVA the NCPU efficiencies of the zinc tetraphenylporphyrins vary significantly with their steric characteristics; the most sterically crowded tetraphenyl derivative exhibits the greatest efficiency. DFT-D computations have been undertaken and help reveal the sources of these differences.
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ItemHighly Fluorescent Molecularly Insulated Perylene Diimides: Effect of Concentration on Photophysical Properties(AMER CHEMICAL SOC, 2017-10-10)
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ItemHighly Fluorescent Pyridinium Betaines for Light Harvesting(WILEY-V C H VERLAG GMBH, 2017-10-23)We report the findings of our experimental and theoretical investigations into the properties of pyridinium enolates and their potential utility in light-harvesting applications, such as in luminescent solar concentrators (LSCs). We present the synthesis, structures, photophysical characterization, and wavefunction-based quantum-chemical studies of five cyclobetaines. The performance of an LSC device incorporating one of these cyclobetaines is shown to be comparable to state-of-the-art devices.