29 research outputs found

    Stereoelectronic Effect-Induced Conductance Switching in Aromatic Chain Single-Molecule Junctions

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    Biphenyl, as the elementary unit of organic functional materials, has been widely used in electronic and optoelectronic devices. However, over decades little has been fundamentally understood regarding how the intramolecular conformation of biphenyl dynamically affects its transport properties at the single-molecule level. Here, we establish the stereoelectronic effect of biphenyl on its electrical conductance based on the platform of graphene-molecule single-molecule junctions, where a specifically designed hexaphenyl aromatic chain molecule is covalently sandwiched between nanogapped graphene point contacts to create stable single-molecule junctions. Both theoretical and temperature-dependent experimental results consistently demonstrate that phenyl twisting in the aromatic chain molecule produces different microstates with different degrees of conjugation, thus leading to stochastic switching between high- and low-conductance states. These investigations offer new molecular design insights into building functional single-molecule electrical devices

    Field-Induced Relaxation of Magnetization in a Three-Dimensional LnMOF with the Second Bridging Ligand Squarate

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    A three-dimensional (3D) dysprosium­(III) metal-organic framework with nicotinate <i>N</i>-oxide (NNO<sup>–</sup>) and squarate (C<sub>4</sub>O<sub>4</sub><sup>2–</sup>) mixed bridging ligands, [Dy­(NNO)­(C<sub>4</sub>O<sub>4</sub>)­(H<sub>2</sub>O)]<i><sub>n</sub></i> (<b>1</b>), has been hydrothermally synthesized. The dysprosium­(III) ions are linked to each other by the squarate anions to form a unique dysprosium­(III) squarate double-layered network; the NNO<sup>–</sup> anions then bridge such layers to complete the 3D framework. Complex <b>1</b> exhibits a two-step relaxation of magnetization under a dc field of 1000 Oe, with effective energy barrier values of 8.5 and 14.3 K, respectively

    Fluorogenic Enhancement of an in Vitro-Selected Peptide Ligand by Replacement of a Fluorescent Group

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    To prepare a fluorogenic peptide ligand which binds to an arbitrary target, we previously succeeded in seeking a fluorogenic ligand to calmodulin using in vitro selection. In this study the environment-sensitive fluorescent group in the selected peptide ligand was replaced with other fluorescent groups to find the possibility to increase the fluorogenic activity. Surface plasmon resonance measurement exhibited that the binding affinity was held even after the replacement. However, the replacement significantly affected the fluorogenic activity. It depended on the kind of incorporated fluorophors and linker length. As a result, the incorporation of 4-<i>N</i>,<i>N</i>-dimethylamino-1,8-naphthalimide enhanced the fluorescence intensity over 100-fold in the presence of target calcium-bound calmodulin. This study demonstrated that the functionality of in vitro selected peptide can be tuned with keeping the binding affinity

    1,6- and 2,7-<i>trans</i>-β-Styryl Substituted Pyrenes Exhibiting Both Emissive and Semiconducting Properties in the Solid State

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    Molecular materials that are both emissive and semiconducting are highly demanding for organic optoelectronics. In this article, we report the synthesis, emissive, and semiconducting properties of 1,6 and 2,7-<i>trans</i>-β-styryl substituted pyrenes (<b>16PyE</b> and <b>27PyE</b>). The results reveal that both <b>16PyE</b> and <b>27PyE</b> are emissive and semiconducting in the solid state. The fluorescence quantum yields of crystalline solids of <b>16PyE</b> and <b>27PyE</b> were determined to be 28.8% and 27.4%, respectively. Microrods of <b>16PyE</b> and microplates of <b>27PyE</b> were found to exhibit promising optical waveguilding behavior. Furthermore, on the basis of the transfer and output curves of the respective organic field effect transistors (OFETs), thin films of <b>16PyE</b> and <b>27PyE</b> were found to show <i>p</i>-type semiconducting properties with hole mobility up to 1.66 cm<sup>2</sup>V<sup>–1</sup>s<sup>–1</sup>. Such dual functions (emissive and semiconducting) of <b>16PyE</b> and <b>27PyE</b> can be ascribed to the unique intermolecular interactions and packing within crystals of <b>16PyE</b> and <b>27PyE</b>. Both 1,6 and 2,7-<i>trans</i>-β-styryl substituted pyrenes show relatively strong emissions in the solid state, and their microcrystalline samples exhibit promising optical waveguilding behavior. Moreover, their thin films exhibit <i>p</i>-type semiconducting property with hole mobilities up to 1.66 cm<sup>2</sup>V<sup>–1</sup>s<sup>–1</sup>

    High fat diet post-infarction has no affect on cardiac function.

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    <p>(<b>A</b>) Long axis m-mode utilizing the Vevo 770 imaging system. (<b>B</b>-<b>D</b>) Ejection fraction, diastolic volume, and systolic volume were calculated using Simpson’s method. (<b>E</b>) Left Ventricular pressure was assessed via Millar catheter. (<b>F</b>) Cardiac contractility as accessed by the minimum and maximum rate of pressure change (dP/dt). (<b>G</b>) The rate of relaxation (Tau) and (<b>H</b>) the cardiac work remained unchanged between the groups. Results are expressed as means ± S.E., *, p< 0.05.</p

    A high fat diet preceding and continued after infarction has no affect on cardiac function.

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    <p>(<b>A</b>) Long axis m-mode utilizing the Vevo 770 imaging system. (<b>B</b>-<b>D</b>) Ejection fraction, diastolic volume, and systolic volume were calculated using Simpson’s method. (<b>E</b>) Left Ventricular pressure was assessed via Millar catheter. (<b>F</b>) Cardiac contractility as accessed by the minimum and maximum rate of pressure change (dP/dt). (<b>G</b>) The rate of relaxation (Tau) and (<b>H</b>) the cardiac work remained unchanged between the groups. Results are expressed as means ± S.E., *, p< 0.05.</p

    Comparison of the appearance of CECT and clinical severity of AP.

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    <p>(A) The incidence of ANP in AP patients with AFL or NAFL; (B) The clinical severity of AP in AP patients with AFL or NAFL. CECT: contrast-enhanced computed tomography; AP: acute pancreatitis; AFL: alcoholic fatty liver; NAFL: non- alcoholic fatty liver; AEP: acute edematous pancreatitis; ANP: acute necrotizing pancreatitis; MAP: mild acute pancreatitis; MSAP: moderately severe acute pancreatitis; SAP: severe acute pancreatitis.</p

    Self-Assembled Nanostructures Based on Activatable Red Fluorescent Dye for Site-Specific Protein Probing and Conformational Transition Detection

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    Smart and versatile nanostructures have demonstrated their effectiveness for biomolecule analysis and show great potential in digging insights into the structural/functional relationships. Herein, a nanoscale molecular self-assembly was constructed for probing the site-specific recognition and conformational changes of human serum albumin (HSA) with tunable size and emission. A tetraphenylethylene derivative TPE-red-COOH was used as the building block for tailoring fluorescence-silent nanoparticles. The highly specific and sensitive response to HSA was witnessed by the fast turn-on of the red fluorescence and simultaneous disassembly of the nanostructures, whereas various endogenous biomolecules cannot induce such response. The mechanism investigation indicates that the combination of multiple noncovalent interactions is the driving force for disassembling and trapping TPE-red-COOH into HSA. The resultant restriction of intramolecular rotation of TPE-red-COOH in the hydrophobic cavity of HSA induces the significant red emission. By using the fluorescence activatable nanosensor as the structural indicator, the stepwise conformational transitions of HSA during denaturing and the partial refolding of subdomain IIA of HSA were facilely visualized. Benefiting from its activatable signaling, sensitivity, and simplicity, such molecular assembly provides a kind of soft nanomaterial for site-specific biomolecule probing and conformational transition detection concerning their structure, function, and biomedical characteristics

    New Donor–Acceptor–Donor Molecules with Pechmann Dye as the Core Moiety for Solution-Processed Good-Performance Organic Field-Effect Transistors

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    In this paper, we report the synthesis and characterization of two new D-A-D molecules (<i>E</i>)-5,5′-bis­(5-(benzo­[<i>b</i>]­thiophen-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethyl- hexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BTBPD</b>) and (<i>E</i>)-5,5′-bis- (5-(benzo­[<i>b</i>]­furan-2-yl)­thiophen-2-yl)-1,1′-bis­(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BFBPD</b>). They entail bipyrrolylidene-2,2′(1<i>H</i>,1′<i>H</i>)-dione (<b>BPD</b>, known as Pechmann dye) as the electron-accepting core that is flanked by two benzo­[<i>b</i>]­thiophene moieties and two benzo­[<i>b</i>]­furan moieties, respectively. Crystal structures of <b>BTBPD</b> and <b>BFBPD</b> provide solid evidence for the intermolecular donor–acceptor (D-A) interactions, which are favorable for improving charge transport performance. Organic field-effect transistors (OFETs) were prepared based on thin films of <b>BTBPD</b> and <b>BFBPD</b> through solution-processed technique. OFETs of <b>BTBPD</b> exhibit relatively high hole mobility up to 1.4 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> with high on/off ratio up to 10<sup>6</sup>. In comparison, the hole mobility of OFETs with <b>BFBPD</b> (0.14 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>) is relatively low, because of the poor thin-film morphology and low molecular ordering, even after annealing. Thin-film morphological and XRD studies were carried out to understand the variation of hole mobilities after annealing at different temperatures. The present studies clearly demonstrate the potentials of <b>BPD</b> that is planar and polar as the electron-acceptor moiety to build D-A molecules for organic semiconductors with good performance

    Alternating Conjugated Electron Donor–Acceptor Polymers Entailing Pechmann Dye Framework as the Electron Acceptor Moieties for High Performance Organic Semiconductors with Tunable Characteristics

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    In this paper, we report the design, synthesis and semiconducting behavior of two conjugated D–A polymers <b>P-BPDTT</b> and <b>P-BPDBT</b> which entail <b>BPD</b>, a Pechmann dye framework, as electron accepting moieties, and thieno­[3,2-<i>b</i>]­thiophene and 2,2′-bithiophene as electron donating moieties. Their HOMO/LUMO energies and bandgaps were estimated based on the respective cyclic voltammgrams and absorption spectra of thin films. <b>P-BPDTT</b> possesses lower LUMO level and narrower bandgap than <b>P-BPDBT</b>. On the basis of the characterization of the field-effect transistors, a thin film of <b>P-BPDTT</b> exhibits ambipolar semiconducting properties with hole and electron mobilities reaching 1.24 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> and 0.82 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>, respectively, after thermal annealing. In comparison, thin film of <b>P-BPDBT</b> only shows <i>p</i>-type semiconducting behavior with hole mobility up to 1.37 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>. AFM and XRD studies were presented to understand the interchain arrangements on the substrates and the variation of carrier mobilities
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