School of Chemistry - Research Publications
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ItemA reflective display based on the electro-microfluidic assembly of particles within suppressed water-in-oil droplet array(SPRINGERNATURE, 2023-12-05)Reflective displays have stimulated considerable interest because of their friendly readability and low energy consumption. Herein, we develop a reflective display technique via an electro-microfluidic assembly of particles (eMAP) strategy whereby colored particles assemble into annular and planar structures inside a dyed water droplet to create "open" and "closed" states of a display pixel. Water-in-oil droplets are compressed within microwells to form a pixel array. The particles dispersed in droplets are driven by deformation-strengthened dielectrophoretic force to achieve fast and reversible motion and assemble into multiple structures. This eMAP based device can display designed information in three primary colors with ≥170° viewing angle, ~0.14 s switching time, and bistability with an optimized material system. This proposed technique demonstrates the basis of a high-performance and energy-saving reflective display, and the display speed and color quality could be further improved by structure and material optimization; exhibiting a potential reflective display technology.
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ItemUnravelling the mechanism of neurotensin recognition by neurotensin receptor 1(NATURE PORTFOLIO, 2023-12-09)The conformational ensembles of G protein-coupled receptors (GPCRs) include inactive and active states. Spectroscopy techniques, including NMR, show that agonists, antagonists and other ligands shift the ensemble toward specific states depending on the pharmacological efficacy of the ligand. How receptors recognize ligands and the kinetic mechanism underlying this population shift is poorly understood. Here, we investigate the kinetic mechanism of neurotensin recognition by neurotensin receptor 1 (NTS1) using 19F-NMR, hydrogen-deuterium exchange mass spectrometry and stopped-flow fluorescence spectroscopy. Our results indicate slow-exchanging conformational heterogeneity on the extracellular surface of ligand-bound NTS1. Numerical analysis of the kinetic data of neurotensin binding to NTS1 shows that ligand recognition follows an induced-fit mechanism, in which conformational changes occur after neurotensin binding. This approach is applicable to other GPCRs to provide insight into the kinetic regulation of ligand recognition by GPCRs.
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ItemNo Preview AvailableDirect measurement of the structural change associated with amorphous solidification using static scattering of coherent radiation(AIP Publishing, 2023-12-28)In this paper, we demonstrate that the weak temperature dependence of the structure factor of supercooled liquids, a defining feature of the glass transition, is a consequence of the averaging of the scattering intensity due to angular averaging. We show that the speckle at individual wavevectors, calculated from a simulated glass former, exhibits a Debye-Waller factor with a sufficiently large temperature dependence to represent a structural order parameter capable of distinguishing liquid from glass. We also extract from the speckle intensities a quantity proportional to the variance of the local restraint, i.e., a direct experimental measure of the amplitude of structural heterogeneity.
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ItemNo Preview AvailableSynergistic effects of hole blocking and Forster resonance energy transfer process in high-performance photomultiplication organic photodetectors(American Institute of Physics, 2023-12-04)Organic photodetectors (OPDs) are a potential next-generation photodetection technology because they are lightweight, flexible, and have customizable spectral responses. However, high dark currents with low detectability remain major challenges, limiting the widespread application of photomultiplication OPDs (PM-OPDs). This work describes a straightforward interface modification strategy based on the PBDB-T:N2200 bulk heterojunction (BHJ) structure to improve the PM-OPD performance. Introducing a thin rubrene layer achieves the synergistic effects of hole blocking and the Förster resonance energy transfer (FRET) process, resulting in a two-order-of-magnitude reduction in dark current density and an increased responsivity of 19.77 A W−1 at 660 nm. Moreover, the external quantum efficiency improves significantly through FRET, and a specific detectivity of 4.39 × 1013 Jones is demonstrated at 660 nm, which is the highest value among existing PM-OPDs, using BHJ structures. An impressive increase in the linear dynamic range from 91 to 144 dB was obtained due to the improved photocurrent density and balanced charge transport. The broad applicability of the strategy was verified through a PM6:Y6-based OPD system. Our approach offers more general application prospects by improving the detection capability of photodetectors for low-light environments.
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ItemThe physical and electronic properties of Metal-Organic Frameworks containing dipyridylthiazolo[5,4-d]thiazole(Royal Society of Chemistry, 2023-11-01)Five Metal–Organic Frameworks ({[M2(tdc)2(L)2]·2DMF}, tdc = 2,5-thiophenedicarboxylate, M = ZnII (1–Zn), CuII (1–Cu), MnII (1–Mn), {[Zn(oba)(L)]·DMF·H2O} (2–Zn), oba = 4,4′-oxybisbenzoate, and {[Zn2(bpdc)2(L)2]·L}, (3–Zn) bpdc = 4,4′-biphenyldicarboxylate) that incorporate the redox-active 2,5-dipyridylthiazolo[5,4-d]thiazole (DPTzTz) ligand (L) have been synthesised and their electronic properties elucidated. The ligand-based organic radicals were generated using in situ techniques and monitored using a suite of solid-state spectroelectrochemistry techniques. The absence of a near infra-red band (NIR), indicating through-space intervalence charge transfer (IVCT), in all analysed materials suggests that both the inter-ligand distance between cofacial TzTz moieties and the flexibility of the TzTz moiety affect the through-space IVCT.
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ItemPolarity-Tunable Field Effect Phototransistors(AMER CHEMICAL SOC, 2023-05-30)Field-effect phototransistors feature gate voltage modulation, allowing dynamic performance control and significant signal amplification. A field-effect phototransistor can be designed to be inherently either unipolar or ambipolar in its response. However, conventionally, once a field-effect phototransistor has been fabricated, its polarity cannot be changed. Herein, a polarity-tunable field-effect phototransistor based on a graphene/ultrathin Al2O3/Si structure is demonstrated. Light can modulate the gating effect of the device and change the transfer characteristic curve from unipolar to ambipolar. This photoswitching in turn produces a significantly improved photocurrent signal. The introduction of an ultrathin Al2O3 interlayer also enables the phototransistor to achieve a responsivity in excess of 105 A/W, a 3 dB bandwidth of 100 kHz, a gain-bandwidth product of 9.14 × 1010 s-1, and a specific detectivity of 1.91 × 1013 Jones. This device architecture enables the gain-bandwidth trade-off in current field-effect phototransistors to be overcome, demonstrating the feasibility of simultaneous high-gain and fast-response photodetection.
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ItemSize, Diffusion, and Sedimentation of Gold Nanorods(AMER CHEMICAL SOC, 2023-11-08)We have used four different analytical techniques (electron microscopy (TEM), dynamic light scattering (DLS), analytical ultracentrifugation (AUC), and small angle X-ray scattering (SAXS) to measure the length and width as well as the diffusion coefficients of gold nanorods of different aspect ratio. All four methods could reproduce the trends in aspect ratio, and both length and width could be extracted once the ligand shell was accounted for. The CTAB bilayer coating was determined to have a thickness of 3.34, 3.02, and 3.26 nm by SAXS, DLS, and AUC, respectively. TEM nevertheless yielded the best predictions for the nanorod ensemble surface plasmon resonance by using COMSOL simulations. All four methods yielded better fits when the rods were treated as spherically capped cylinders.
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ItemAmplifying the Negative Solvatochromism of Pyridinium Phenolates via Fluorene Conjugation(American Chemical Society, 2023-12-19)New chromophores carrying a donor phenolate group and an acceptor pyridyl moiety separated by a fluorene spacer are reported. A progressive elongation of the systems was achieved by the introduction of an additional phenyl ring and one or two vinyl linkers using Suzuki–Miyaura or Horner–Wadsworth–Emmons couplings. Zwitterionic forms FL1–FL5 of these donor–bridge–acceptor molecules were generated through consequent N-methylation and deprotonation reactions leading to large redshifts in absorbance maxima. UV–vis absorbance studies also revealed a negative solvatochromic behavior, with a smooth bathochromic shift observed upon decreasing the solvent polarity. Notably, examples FL1a and FL3 exhibited wide solvatochromic shifts of 235 and 297 nm, respectively, as the solvent polarity gradually lowered from polar water to less polar pyridine. Remarkably, the magnitude of the shift for FL3 was even greater than that of Reichardt’s dye (253 nm) in the same solvent range, which is known to be one of the best performing solvatochromic dyes reported. Apart from extending the conjugation, the fluorene moiety also allows facile side chain engineering, making these solvatochromic dyes attractive candidates for medium-polarity indicators and sensors.
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ItemElectrical conductivity and DFT investigations of a 2D CuI-TCNQII− framework(Royal Society of Chemistry, 2023-11-21)A stacked 2D Cu(i) coordination polymer displays electrical conductivity with DFT calculations revealing a band structure comprised of donor TCNQII− and acceptor 2,5-dimethylpyrazine p-orbitals.
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ItemSuppressing Kinetic Aggregation of Non-Fullerene Acceptor via Versatile Alloy States Enables High-Efficiency and Stable Ternary Polymer Solar Cells(Wiley, 2021-05-17)Despite considerable advances devoted to improving the operational stability of organic solar cells (OSCs), the metastable morphology degradation remains a challenging obstacle for their practical application. Herein, the stabilizing function of the alloy states in the photoactive layer from the perspective of controlling the aggregation characteristics of non‐fullerene acceptors (NFAs), is revealed. The alloy‐like model is adopted separately into host donor and acceptor materials of the state‐of‐the‐art binary PM6:BTP‐4Cl blend with the self‐stable polymer acceptor PDI‐2T and small molecule donor DRCN5T as the third components, delivering the simultaneously enhanced photovoltaic efficiency and storage stability. In such ternary systems, two separate arguments can rationalize their operating principles: (1) the acceptor alloys strengthen the conformational rigidity of BTP‐4Cl molecules to restrain the intramolecular vibrations for rapid relaxation of high‐energy excited states to stabilize BTP‐4Cl acceptor. (2) The donor alloys optimize the fibril network microstructure of PM6 polymer to restrict the kinetic diffusion and aggregation of BTP‐4Cl molecules. According to the superior morphological stability, non‐radiative defect trapping coefficients can be drastically reduced without forming the long‐lived, trapped charge species in ternary blends. The results highlight the novel protective mechanisms of engineering the alloy‐like composites for reinforcing the long‐term stability of NFA‐based ternary OSCs.