11 research outputs found

    Charge Recombination in Phosphorescent Organic Light-Emitting Diode Host–Guest Systems through QM/MM Simulations

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    Host–guest systems are crucial for achieving high efficiency in most organic light-emitting diode (OLED) devices. However, charge recombination in such systems is poorly understood due to complicated molecular environment, making the rational design of host–guest systems difficult. In this article, we present a computational study of a phosphorescent OLED with 2,8-bis­(triphenylsilyl)­dibenzofuran (BTDF) as the host and <i>fac</i>-tris­(2-phenylpyridine) iridium (<i>fac</i>-Ir­(ppy)<sub>3</sub>) as the guest, using a combined quantum mechanics/molecular mechanics (QM/MM) scheme. A new reaction coordinate is introduced to measure the electrostatic interactions between the host and guest molecules. Ionization potentials and electron affinities of the host show broader distributions as the host–guest interaction increases. On the basis of these distributions, we describe a molecular picture of charge recombination on the guest and find a direct charge trapping route for this system. Our results suggest several strategies for the design of more efficient host and guest combinations

    Self-Attractive Hartree Decomposition: Partitioning Electron Density into Smooth Localized Fragments

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    Chemical bonding plays a central role in the description and understanding of chemistry. Many methods have been proposed to extract information about bonding from quantum chemical calculations, the majority of them resorting to molecular orbitals as basic descriptors. Here, we present a method called self-attractive Hartree (SAH) decomposition to unravel pairs of electrons directly from the electron density, which unlike molecular orbitals is a well-defined observable that can be accessed experimentally. The key idea is to partition the density into a sum of one-electron fragments that simultaneously maximize the self-repulsion and maintain regular shapes. This leads to a set of rather unusual equations in which every electron experiences self-attractive Hartree potential in addition to an external potential common for all the electrons. The resulting symmetry breaking and localization are surprisingly consistent with chemical intuition. SAH decomposition is also shown to be effective in visualization of single/multiple bonds, lone pairs, and unusual bonds due to the smooth nature of fragment densities. Furthermore, we demonstrate that it can be used to identify specific chemical bonds in molecular complexes and provides a simple and accurate electrostatic model of hydrogen bonding

    Li<sub>1.4</sub>Al<sub>0.4</sub>Ti<sub>1.6</sub>(PO<sub>4</sub>)<sub>3</sub>‑Modified Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> Anode for Lithium-Ion Storage with Enhanced Rate and Cycling Performance

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    The capacity of Li4Ti5O12 (LTO) at high rates is limited due to the polarization caused by its modest Li-ion (Li+) diffusion coefficient and low electrical conductivity. Coating with ionic conductors is an available method to ameliorate charge transport. Li1+xAlxTi2–x(PO4)3 ion conductors with thermal, chemical, and electrochemical stabilities have been proven to be modification materials for electrodes. Herein, the Li1.4Al0.4Ti1.6(PO4)3 (LATP) precursor dispersion with optimized preparation is applied to the surface modification of LTO by a dynamic mix-drying method. A proper amount of LATP ultrafine particle coating could develop the ion transport rate in the electrode and restrain side reactions. The 2 wt % LATP–LTO anode exhibits an optimized capacity of 168.2 mA h g–1 at 0.1 A g–1 and retains 96.7% of its capacity after 5000 cycles at 5.0 A g–1, while the P-LTO anode retains 86.3% of the capacity. Improved Li+ transport and interface stability in the electrodes lead to the boosted rate and cycling stability. The LATP-modified LTO composites provide a possibility for the further application of related materials in the energy storage field

    Prediction of Excited-State Energies and Singlet–Triplet Gaps of Charge-Transfer States Using a Restricted Open-Shell Kohn–Sham Approach

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    Organic molecules with charge-transfer (CT) excited states are widely used in industry and are especially attractive as candidates for fabrication of energy efficient OLEDs, as they can harvest energy from nonradiative triplets by means of thermally activated delayed fluorescence (TADF). It is therefore useful to have computational protocols for accurate estimation of their electronic spectra in order to screen candidate molecules for OLED applications. However, it is difficult to predict the photophysical properties of TADF molecules with LR-TDDFT, as semilocal LR-TDDFT is incapable of accurately modeling CT states. Herein, we study absorption energies, emission energies, zero–zero transition energies, and singlet–triplet gaps of TADF molecules using a restricted open-shell Kohn–Sham (ROKS) approach instead and discover that ROKS calculations with semilocal hybrid functionals are in good agreement with experimentsunlike TDDFT, which significantly underestimates energy gaps. We also propose a cheap computational protocol for studying excited states with large CT character that is found to give good agreement with experimental results without having to perform any excited-state geometry optimizations

    Insights into the Enhanced Reversibility of Graphite Anode Upon Fast Charging Through Li Reservoir

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    Increasing the charging rate and reducing the charging time for Li-ion batteries are crucial to realize the mainstream of electric vehicles. However, it is formidable to avoid the Li plating on graphite anode upon fast charging. Despite the tremendous progress in Li detection techniques, the fundamental mechanism of Li plating and its chemical/electrochemical responses upon cycling still remains elusive. Herein, we present a comprehensive electrochemical method to investigate the fast charging behavior of graphite electrode. A detailed analysis is directed toward understanding the changes in phase, composition, and morphology of the fast-charged graphite. By applying a resting process, we scrutinize the further reactions of the plated Li, which readily transforms into irreversible (dead) Li. We further develop a modified graphite electrode with a thin Ag coating as the Li reservoir. The plated Li can be “absorbed” by the Ag layer to form the Li–Ag solid solution that suppresses the formation of dead Li and provides structural stability, thus promoting the further lithiation of graphite and enhancing the reversibility. This work not only provides additional insights into the fast charging behavior of graphite electrode but also demonstrates a potential strategy to improve the fast charging performance of graphite anode

    Metallocene-Containing Homopolymers and Heterobimetallic Block Copolymers via Photoinduced RAFT Polymerization

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    We report the synthesis of cationic cobaltocenium and neutral ferrocene containing homopolymers mediated by photoinduced reversible addition–fragmentation chain transfer (RAFT) polymerization with a photocatalyst fac-[Ir­(ppy)<sub>3</sub>]. The homopolymers were further used as macromolecular chain transfer agents to synthesize diblock copolymers via chain extension. Controlled/“living” feature of photoinduced RAFT polymerization was confirmed by kinetic studies even without prior deoxygenation. A light switch between ON and OFF provided a spatiotemporal control of polymerization

    Salt Effect Accelerates Site-Selective Cysteine Bioconjugation

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    Highly efficient and selective chemical reactions are desired. For small molecule chemistry, the reaction rate can be varied by changing the concentration, temperature, and solvent used. In contrast for large biomolecules, the reaction rate is difficult to modify by adjusting these variables because stringent biocompatible reaction conditions are required. Here we show that adding salts can change the <i>rate constant over 4 orders of magnitude</i> for an arylation bioconjugation reaction between a cysteine residue within a four-residue sequence (π-clamp) and a perfluoroaryl electrophile. Biocompatible ammonium sulfate significantly enhances the reaction rate without influencing the site-specificity of π-clamp mediated arylation, enabling the fast synthesis of two site-specific antibody–drug conjugates that selectively kill HER2-positive breast cancer cells. Computational and structure–reactivity studies indicate that salts may tune the reaction rate through modulating the interactions between the π-clamp hydrophobic side chains and the electrophile. On the basis of this understanding, the salt effect is extended to other bioconjugation chemistry, and a new regioselective alkylation reaction at π-clamp cysteine is developed

    Trio Act of Boronolectin with Antibiotic-Metal Complexed Macromolecules toward Broad-Spectrum Antimicrobial Efficacy

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    Bacterial infections, particularly by Gram-negative pathogens, have become a serious threat to global healthcare due to the diminishing effectiveness of existing antibiotics. We report a nontraditional therapy to combine three components in one macromolecular system, in which boronic acid adheres to peptidoglycan or lipopolysaccharide via boron-polyol based boronolectin chemistry, cationic metal polymer frameworks interact with negatively charged cell membranes, and β-lactam antibiotics are reinstated with enhanced vitality to attack bacteria via evading the detrimental enzyme-catalyzed hydrolysis. These macromolecular systems exhibited high efficacy in combating pathogenic bacteria, especially Gram-negative strains, due to synergistic effects of multicomponents on interactions with bacterial cells. <i>In vitro</i> and <i>in vivo</i> cytotoxicity and hemolysis evaluation indicated that these multifunctional copolymers did not induce cell death by apoptosis, as well as did not alter the phenotypes of immune cells and did not show observable toxic effect on red blood cells

    Photoinduced Metal-Free Atom Transfer Radical Polymerization of Biomass-Based Monomers

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    Well-defined polymers derived from biomass feedstock (e.g., soybean oil, rosin acid, and furfural) were successfully prepared by metal-free atom transfer radical polymerization (ATRP). In the presence of photoredox catalysts and UV irradiation, three biomass-based methacrylate monomers were efficiently polymerized with good control over molecular weight and dispersity. NMR and MALDI-TOF MS confirmed high fidelity of chain end groups originated from initiators. Furthermore, block copolymers from these monomers were also achieved through chain extension by metal-free ATRP

    Data_Sheet_1_Effect of angiotensin receptor-neprilysin inhibitor on atrial electrical instability in atrial fibrillation.docx

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    Background and objectiveAround 33.5 million patients suffered from atrial fibrillation (AF), causing complications and increasing mortality and disability rate. Upstream treatment for AF is getting more popular in clinical practice in recent years. The angiotensin receptor-neprilysin inhibitor (ARNI) is one of the potential treatment options. Our study aimed to investigate the effect of ARNI on atrial electrical instability and structural remodeling in AF.MethodsOur research consisted of two parts – a retrospective real-world clinical study and an animal experiment on calmness to verify the retrospective founding. In the retrospective study, we reviewed all patients (n = 110) who had undergone the first AF ablation from 1 August 2018 to 1 March 2022. Patients with ARNI (n = 36) or angiotensin II receptor antagonist (ARB) (n = 35) treatment were enrolled. Their clinical data, ultrasound cardiogram (UCG) and Holter parameters were collected before radiofrequency catheter ablation (RFCA) as baseline and at 24-week follow-up. Univariate and multivariate logistic regression analysis were performed. In the animal experiment, we established an AF model (n = 18) on canines by rapid atrial pacing. After the successful procedure of pacing, all the 15 alive beagles were equally and randomly assigned to three groups (n = 5 each): Control group, ARB group, and ARNI group. UCG was performed before the pacing as baseline. Physiological biopsy, UCG, and electrophysiological study (EPS) were performed at 8-week.ResultsClinical data showed that the atrial arrhythmia rate at 24-week was significantly lower in ARNI group compared to ARB group (P ConclusionARNI could reduce atrial electrical instability in AF in comparison with ARB in both retrospective study and animal experiment.</p
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