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A practical method for determining the frequency ratio correction is presented in this study, utilizing umbrella sampling without the computational burden of numerous geometry-optimized structure normal mode analyses. Conversely, the approach correlates the frequency ratio with the alteration in the mass-weighted coordinate depiction of the minimum free energy pathway at the transition state, brought about by isotopic replacement. Calculations of the primary kinetic isotope effect values for 16/18O and 32/34S were performed using the method for six non-enzymatic phosphoryl transfer reactions. Employing the conventional Bigeleisen-Mayer equation, we affirm the consistency between our findings and the geometrically optimized transition state ensemble analysis. This methodology, accordingly, presents a new, practical means for the effortless computation of kinetic isotope effect values in complicated chemical reactions taking place in the condensed phase.

A multitude of cutting-edge characterization methods have been designed to track the electrode-electrolyte interface, which governs the efficacy of electrochemical devices. Unfortunately, the combined use of multiple characterization techniques for in-situ, multi-dimensional electrochemical interface analysis is currently hampered by considerable difficulties. Via a custom-made electrochemical cell, we introduce a hyphenated analytical method combining differential electrochemical mass spectrometry and attenuated total reflection surface-enhanced infrared absorption spectroscopy. This method allows for simultaneous monitoring of volatile and deposited interface species under electrochemical reaction conditions, rendering it particularly useful for non-aqueous, electrolyte-based energy devices. To showcase the viability of our home-built system, we revealed its potential by investigating intriguing reactions, specifically focusing on the oxidation and reduction processes occurring in non-aqueous lithium-ion battery carbonate-based electrolytes on Li1+xNi0.8Mn0.1Co0.1O2 and graphite substrates, and the reversible oxygen reaction in lithium-oxygen batteries, thereby establishing valuable reaction pathways. By coupling and complementing existing methods, the research presented here is anticipated to offer significant insights into the interfacial electrochemistry of energy storage materials (i.e., in situ, multi-dimensional data from a single run) and generate considerable interest within and beyond the electrochemistry research community.

Functional groups in polymers are capable of establishing hydrogen bonds (H-bonds) with water molecules, fostering a strong network of H-bonds that have a pronounced impact on bulk properties. Molecular dynamics (MD) simulations, employed in this study, investigated the H-bonding dynamics of water molecules confined within poly(2-methoxyethyl acrylate) (PMEA), poly(2-hydroxyethyl methacrylate) (PHEMA), and poly(1-methoxymethyl acrylate) (PMC1A) poly(meth)acrylates. The results highlighted a notable decrease in the rate of hydrogen bonding dynamics when the water content was diminished. Furthermore, an analysis of water molecule diffusion and its connection to hydrogen bond disruption was conducted. Our findings point to the fact that when H-bonds between water molecules and the methoxy oxygen of PMEA are severed, the associated water molecules remain closely positioned, failing to exhibit picosecond-scale diffusion. Alternatively, the water molecules, bound by hydrogen bonds to the hydroxy oxygen of PHEMA and the methoxy oxygen of PMC1A, disperse synchronously with the breaking of those hydrogen bonds. The intricate mechanisms through which polymer functional groups affect H-bonding dynamics are explicitly revealed in these results.

On surfaces of identical composition, droplets can move because of external forces, like gravity; however, with wettability gradients, movement happens internally, without external forces, since the gradients create a propelling force. We investigate the more complex droplet dynamics through molecular dynamics simulations, which are driven by both external and internal forces. By way of comparison, the specific scenarios where only one driving force is active are also explored. The velocity remains almost constant for a significant period of the sliding movement that happens at the border of two substrates with diverse wettabilities. Mobility of the initial substrate, as perceived by the receding contact line, is the key determinant of effective mobility, which is ultimately the product of effective mobility and effective force. This observation harmonizes with the flow pattern’s characteristics, implying the desorption of particles at the receding contact line acts as the rate-determining step. Combining the external force with a renormalized internal force gives the effective force. This renormalization, driven by wettability gradients, is interpretable as having stronger dissipation effects.

Sliding experiments on rectangular rubber, polyethylene, and silica glass blocks over ice surfaces are conducted to analyze friction, where temperatures range from -40°C to 0°C and sliding speeds range from 3 meters per second to 1 centimeter per second. Our investigation focuses on a winter tire rubber compound, existing in two distinct states: a compact block and a foam, with a void volume of 10%. A similar frictional effect on ice was consistently seen for both rubber compounds at all the temperatures that were investigated. As evidenced by previous low-temperature, low-sliding-velocity studies, our hypothesis is that a key contribution to friction force involves the slip between the ice surface and ice pieces affixed to the rubber. The occurrence of a thin pre-melted water film at the rubber-ice interface is facilitated by temperatures around 0 degrees Celsius (or by high enough sliding speeds), with the contribution to friction from shearing the area of true contact being relatively small. The dominant friction force in this case arises from the viscoelastic deformation of the rubber material, provoked by the sharp projections on the ice. Polyethylene (PE) and silica glass (SG) blocks, when sliding on ice, exhibit a considerably different sliding friction compared to the friction of rubber. The friction coefficient for PE, spanning the range of 0.004 to 0.015, generally displays a low sensitivity to velocity. However, this relationship is inverted around the melting point of ice. In the vicinity of this transition, a marked increase in friction is observed as sliding speeds decrease. Silica glass, displaying similar low friction as polyethylene (PE) at temperatures higher than -10 degrees Celsius, contrasts this trend with very significant friction coefficients (approximately unity) at lower temperatures. In both PE and SG scenarios, the friction force is directly correlated with the position ‘x’ on the sliding track, provided the ice surface is not extraordinarily smooth. The friction force’s plowing component arises from the ice surface’s bumps, which the elastically stiff PE and SG blocks shear off. hedgehog signaling Friction coefficients, which are quite large in localized areas 1, are produced as a result, and visual inspection of the ice surface after the sliding motion reveals ice wear particles (white powder) in regions where ice bumps are present. Comparable effects are to be anticipated in the case of rubber blocks lying beneath the rubber glass transition temperature, which renders the rubber in its (rigidly elastic) glassy phase.

Organometallic phosphors are a key part of high-efficiency organic light-emitting devices, functioning as emissive materials. The photostability of blue-emitting phosphors is hampered by problems of low photostability, caused by chemical and environmental degradation, and triplet quenching effects. Numerous techniques have been adopted for improving the light-resistance of these luminescent materials, which include the design of innovative organometallic complexes and the manipulation of host-dopant composition within thin film layers. A new technique is proposed for improving the photostability of blue organometallic phosphors, employing localized surface plasmon resonances to increase the efficiency of triplet recombination. A higher recombination rate leads to greater photostability in the phosphor, owing to a reduction in the number of triplet quenching routes. We find that nanoparticle-based plasmonic surfaces substantially diminish the phosphorescence lifetime, thereby improving the photostability of the blue organometallic phosphor to a level that increases up to 36-fold. Studies on various plasmonic surfaces also revealed less substantial improvements in photostability, due to a reduced overlap of the plasmon modes with the emitter’s spectrum and a reduced concentration of the plasmonic modes. Methods for enhancing phosphor photostability at blue wavelengths using plasmonic surfaces differ significantly from other techniques that involve modifications to the phosphor’s molecular structure or the emitting material’s composition; instead, this approach targets the local electromagnetic environment.

We posit a Markovian quantum model describing the time-dependent pressure-induced decoherence of rotational wave packets in gas-phase molecules, transcending the secular approximation. The model rests upon a collisional relaxation matrix, formulated using the energy-corrected sudden approximation. This enhancement surpasses the prior infinite order sudden approximation by incorporating molecular rotation during collisions. The model is critically examined by comparing its predictions to time-domain measurements of pressure-induced decays in molecular-axis alignment features (revivals and echoes) from HCl and CO2 gases, either pure or diluted with helium. In the HCl-He and CO2-He Markovian systems, a comparison of calculated and experimental data underscores the robustness of our method, even with substantial breakdown of the secular approximation. Differing significantly from other scenarios, the model underestimates the speed at which alignment decays for pure HCl and CO2 in the initial time periods. This result arises from the non-Markovian nature of HCl-HCl and CO2-CO2 interactions, importantly influenced by collisions occurring during the excitation of the system by the aligning laser pulse.