33 research outputs found

    Click Chemistry: Mechanistic Insights into the Role of Amines Using Single-Molecule Spectroscopy

    Get PDF
    Single-molecule spectroscopy is used to gain insights into the click chemistry reaction photocatalyzed by copper. We show that Cu<sub><i>x</i></sub>O@Nb<sub>2</sub>O<sub>5</sub> catalysts can act as truly heterogeneous photocatalysts and that the amine plays an important role in the complexation between the alkyne and the copper active site on the catalyst surface. For complex reactions occurring in the subnanomolar range, preassociation can be essential and cocatalysts (such as amines here) may play an enabling role facilitating the reagents “reunion” and prolonging the time available for reaction. This provides a rational analysis of the amine role in heterogeneous photocatalytic click chemistry

    AI-based optimization of PEM fuel cell catalyst layers for maximum power density via data-driven surrogate modeling

    No full text
    © 2020 Elsevier Ltd Catalyst layer (CL) is the core electrochemical reaction region of proton exchange membrane fuel cells (PEMFCs). Its composition directly determines PEMFC output performance. Existing experimental or modeling methods are still insufficient on the deep optimization of CL composition. This work develops a novel artificial intelligence (AI) framework combining a data-driven surrogate model and a stochastic optimization algorithm to achieve multi-variables global optimization for improving the maximum power density of PEMFCs. Simulation results of a three-dimensional computational fluid dynamics (CFD) PEMFC model coupled with the CL agglomerate model constitutes the database, which is then used to train the data-driven surrogate model based on Support Vector Machine (SVM), a typical AI algorithm. Prediction performance shows that the squared correlation coefficient (R-square) and mean percentage error in the test set are 0.9908 and 3.3375%, respectively. The surrogate model has demonstrated comparable accuracy to the physical model, but with much greater computation-resource efficiency: the calculation of one polarization curve will be within one second by the surrogate model, while it may cost hundreds of processor-hours by the physical CFD model. The surrogate model is then fed into a Genetic Algorithm (GA) to obtain the optimal solution of CL composition. For verification, the optimal CL composition is returned to the physical model, and the percentage error between the surrogate model predicted and physical model simulated maximum power densities under the optimal CL composition is only 1.3950%. The results indicate that the proposed framework can guide the multi-variables optimization of complex systems

    Direct, Rapid, Facile Photochemical Method for Preparing Copper Nanoparticles and Copper Patterns

    No full text
    We develop a facile method for preparing copper nanoparticles and patterned surfaces with copper stripes by ultraviolet (UV) irradiation of a mixture solution containing a photoinitiator and a copper–amine coordination compound. The copper–amine compound is formed by adding diethanol amine to an ethanol solution of copper chloride. Under UV irradiation, free radicals are generated by photoinitiator decomposition. Meanwhile, the copper–amine coordination compound is rapidly reduced to copper particles because the formation of the copper–amine coordination compound prevents the production of insoluble cuprous chloride. Poly­(vinylpyrrolidone) is used as a capping agent to prevent the aggregation of the as-prepared copper nanoparticles. The capping agent increases the dispersion of copper nanoparticles in the ethanol solution and affects their size and morphology. Increasing the concentration of the copper–amine coordination compound to 0.1 M directly forms a patterned surface with copper stripes on the transparent substrate. This patterned surface is formed through the combination of the heterogeneous nucleation of copper nanoparticles and photolithography. We also investigate the mechanism of photoreduction by UV–vis spectroscopy and gas chromatography–mass spectrometry

    Mechanism of Interaction of Water above the Methylammonium Lead Iodide Perovskite Nanocluster: Size Effect and Water-Induced Defective States

    No full text
    Water is often viewed as detrimental to organic halide perovskite stability. However, evidence highlights its efficacy as a solvent during organic perovskite liquid synthesis. This paradox prompts an investigation into water’s influence on perovskite nanoclusters. Employing first principle calculations and ab initio molecular dynamics simulations, surprisingly, we discover some subsurface layers of methylammonium lead iodide (MAPbI3) nanoclusters exhibit stronger relaxation than surface layers. Moreover, a strong quantum confinement effect enhances the band gap of MAPbI3 as the nanocluster size decreases. Notably, the water molecules above MAPbI3 nanoclusters induce rich localized defect states, generating low-lying shallow states above the valence band for the small amounts of surface water molecules and band-like deep states across the whole gap for large nanoclusters. This work provides insights into water’s role in the electronic structure and structural evolution of perovskite nanoclusters, aiding the design of water-resistant layers to protect perovskite quantum dots from ambient humidity

    Exotic Quartic Anharmonicity Induced by Rattling Effect in Layered Isostructural Compounds

    No full text
    Anharmonicity of phonons correlates with less dispersive potential surfaces and usually governs the thermal transport of low-dimensional materials. Here, we demonstrate the significant role of the so-called “rattling” action in affecting lattice anharmonicity, originating from the ease of freedom of confined but loose atoms in two-dimensional space. Based on calculations of X2Si2Te6 (X = Sb and Bi) within the Peierls–Boltzmann framework, the degree of high-order four-phonon scattering differs strikingly despite their isostructural feature. Upon switching on four-phonon scattering, a significant drop of thermal conductivity (κph) occurs in Bi2Si2Te6 up to 43.15% (71.62%) at 300 K (1000 K), while a moderate reduction occurs for Sb2Si2Te6. This arises from a stronger quartic anharmonicity of Bi2Si2Te6 than Sb2Si2Te6, dominated by the redistribution four-phonon process (λ + λ′ → λ″ + λ‴). We show that the strong quartic anharmonicity is more likely to occur in systems with flat phonon bands, large atoms, and rattling atomic units. These new insights provide perspectives in the design of materials with low κph through introducing rattling units in layered materials or interfaces

    Additional file 2 of LINC00240 in the 6p22.1 risk locus promotes gastric cancer progression through USP10-mediated DDX21 stabilization

    No full text
    Additional file 2: Supplementary Figure 1. The relative expression levels of LINC00240 in human GES-1, MKN-28, MKN-45, AGS, BGC-823, HGC-27 and MGC-803 cell lines. ***P < 0.001. Supplementary Figure 2. Silencing of LINC00240 significantly promoted apoptosis of gastric cancer cells (A), but did not impact cell cycle (B). Supplementary Figure 3. Expression of apoptotic proteins (A), DDX21 and USP10 (B) in gastric cancer xenografts

    Additional file 1 of LINC00240 in the 6p22.1 risk locus promotes gastric cancer progression through USP10-mediated DDX21 stabilization

    No full text
    Additional file 1: Supplementary Table 1. Primers for RT-qPCR. Supplementary Table 2. Sequences of shRNAs and siRNAs. Supplementary Table 3. Antibodies used in the study. Supplementary Table 4. Mass spectrometry of proteins pulled-down by LINC00240 in MGC80-3 cell

    Additional file 1 of Automatic evaluation of atlantoaxial subluxation in rheumatoid arthritis by a deep learning model

    No full text
    Additional file 1: Sup Fig. 1. Distribution of ADI and SAC. a Atlantodental interval (ADI, mm). b Space available for the spinal cord (SAC, mm)

    Unimolecular Micelle-Based Hybrid System for Perivascular Drug Delivery Produces Long-Term Efficacy for Neointima Attenuation in Rats

    No full text
    At present, there are no clinical options for preventing neointima-caused (re)­stenosis after open surgery such as bypass surgery for treating flow-limiting vascular disease. Perivascular drug delivery is a promising strategy, but in translational research, it remains a major challenge to achieve long-term (e.g., > 3 months) anti­(re)­stenotic efficacy. In this study, we engineered a unique drug delivery system consisting of durable unimolecular micelles, formed by single multiarm star amphiphilic block copolymers with only covalent bonds, and a thermosensitive hydrogel formed by a poly­(lactide-co-glycolide)–poly­(ethylene glycol)–poly­(lactide-co-glycolide) triblock copolymer (abbreviated as triblock gel) that is stable for about 4 weeks <i>in vitro</i>. The drug-containing unimolecular micelles (UMs) suspended in Triblock gel were able to sustain rapamycin release for over 4 months. Remarkably, even 3 months after perivascular application of the rapamycin-loaded micelles in Triblock gel in the rat model, the intimal/medial area ratio (a restenosis measure) was still 80% inhibited compared to the control treated with empty micelle/gel (no drug). This could not be achieved by applying rapamycin in Triblock gel alone, which reduced the intimal/medial ratio only by 27%. In summary, we created a new UM/Triblock gel hybrid system for perivascular drug delivery, which produced a rare feat of 3-month restenosis inhibition in animal tests. This system exhibits a real potential for further translation into an anti­(re)­stenotic application with open surgery
    corecore