19 research outputs found

    Why Should the Reaction Order of a Bimolecular Reaction be 2.33 Instead of 2?

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    Predicting the reaction kinetics, that is, how fast a reaction can happen in a solution, is essential information for many processes, such as industrial chemical manufacturing, refining, synthesis and separation of petroleum products, environmental processes in air and water, biological reactions in cells, biosensing, and drug delivery. Collision theory was originally developed to explain the reaction kinetics of gas reactions with no dilution. For a reaction in a diluted inert gas solution or a diluted liquid solution, diffusion often dominates the collision process. Thus, it is necessary to include diffusion in such a calculation. Traditionally, the classical Smoluchowski rate is used as a starting point to predict the collision frequency of two molecules in a diluted solution. In this report, a different collision model is derived from the adsorption of molecules on a flat surface. A surprising result is obtained, showing that the reaction order for bimolecular reactions should be 2 and 1/3 instead of 2, following a fractal reaction kinetics

    Monitoring Phase Separation and Dark Recovery in Mixed Halide Perovskite Clusters and Single Crystals Using <i>In Situ</i> Spectromicroscopy

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    Mixed halide perovskites (MHPs) are a group of semiconducting materials with promising applications in optoelectronics and photovoltaics, whose bandgap can be altered by adjusting the halide composition. However, the current challenge is to stabilize the light-induced halide separation, which undermines the device’s performance. Herein we track down the phase separation dynamics of CsPbBr1.2I1.8 MHP single cubic nanocrystals (NCs) and clusters as a function of time by in situ fluorescence spectromicroscopy. The particles were sorted into groups 1 and 2 using initial photoluminescence intensities. The phase separation followed by recovery kinetics under dark and photo blinking analysis suggests that group 1 behaved more like single NCs and group 2 behaved like clusters. Under the 0.64 W/cm2 laser illumination, the phase shifts for single NCs are 3.4 ± 1.9 nm. The phase shifts are linearly correlated with the initial photoluminescence intensities of clusters, suggesting possible interparticle halide transportation

    Influence of Defects on the Reactivity of Organic Surfaces

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    Molecular orientation within organic solids limits the range of applicable surface reactions, with reactive functionalities often recessed and inaccessible to adsorbates. To induce reactivity in heretofore inert orientations of acenes, a defect-mediated mechanism is utilized to functionalize thin-film phase pentacene. This mechanism was demonstrated via correlation of reaction data to defect density, determined via polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and atomic force microscopy (AFM). By controllably varying the amount of grain boundaries in the acene films, the reaction can be varied from near zero to coverage exceeding a monolayer. The extensive coverage suggests that the reaction propagates from the defects throughout the grains, a prediction borne out via direct observation of reaction progression along the surface from a single dislocation (via scanning electron microscopy). The results support a mechanism whereby the reaction is initialized at the defect sites, especially boundaries of crystal domains, which opens the unfavorable molecular orientation of the (001) pentacene to incoming adsorbates. This exact film configuration and its successful reaction is especially relevant to organic thin-film transistor (OTFT) devices

    Additional file 2 of Comprehensive DNA methylation profiling of COVID-19 and hepatocellular carcinoma to identify common pathogenesis and potential therapeutic targets

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    Additional file 2: Figure S2. Analyze the soft threshold power (β) of the scale-free topology model fitting index and the mean connectivity of the soft threshold power (β = 3)