Spotlights pubs.acs.org/JPCL
Spotlights: Volume 8, Issue 16
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CHEMICAL REACTIVITY DESCRIPTOR FOR THE OXIDE-ELECTROLYTE INTERFACE IN LI-ION BATTERIES
HOW DO METHYL GROUPS ENHANCE THE TRIPLET CHEMIEXCITATION YIELD OF DIOXETANE? Chemiluminescence, put simply, is the emission of light as a result of a chemical reaction. More specifically, chemiluminescence appears when a thermally activated molecule reacts and undergoes a nonadiabatic transition to an electronic excited state of the product, which then releases the excess energy in the form of light. When this phenomenon occurs in living organisms such as fireflies and fish, it is called bioluminescence, and organisms use this tool to attract partners, lure prey, and defend themselves against predators. Chemiluminescence is also a powerful tool in medicine, e.g., for real-time in vivo imaging and biosensing for environmental pollutants. Using state-of-the-art nonadiabatic dynamics simulations with multiconfigurational electronic structure theory, Vacher et al. (10.1021/acs.jpclett.7b01668) set out to better understand the dramatic increase in chemiluminescence yield upon methylsubstitution of dioxetane. Their findings show how the methyl groups slow down the decomposition process, partly due to a simple mass effect. The authors proposed a simple kinetic model and used it to fit the calculated dissociation half-lives to the experimental yields. The nice agreement demonstrates how an extended stay in the so-called entropic trap region enhances the population of excited states. The results add to our understanding of the chemiluminescence yields of dioxetane molecules and offer insights into bioluminescent systems such as those found in living organisms.
The debut of Tesla’s new, more affordable sedan has received a great deal of attention this year, but the Model 3 is far from the only game in town. Most of the major automobile manufacturers offer all-electric and hybrid models, and more and more cities are adding electric buses to their fleets. Lithium-ion (Li-ion) batteries are most commonly used in these vehicles, and work is ongoing to improve the efficiency and life expectancy of these power sources. The electrode/ electrolyte interface is a key factor affecting the performance and cycle life of Li-ion batteries, so understanding the reaction mechanisms at play is essential for improving their safety and durability. Giordano et al. (10.1021/acs.jpclett.7b01655) used density functional theory calculations to measure the interaction of ethylene carbonate with the surface for oxide layered and rocksalt materials. The study spanned a variety of reaction mechanisms on a series of electrode surfaces, where either the transition metal or the Li content was varied. The results allow for a direct comparison of the energetics of the different reaction mechanisms and provide insights into the role of oxide chemistries on the interfacial reactivity. The authors demonstrate that the interfacial reactivity is governed by the oxide electronic structure, providing design principles for the development of oxides to be used as electrode or coating to limit the decomposition of solvent molecules at their surfaces.
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NATURE-INSPIRED CONSTRUCTION OF TWO-DIMENSIONALLY SELF-ASSEMBLED PEPTIDE ON PRISTINE GRAPHENE Two-dimensional peptide assemblies offer tremendous potential for biomedical applications because of their remarkable properties and novel structures that can mimic natural systems. However, elucidating peptide self-assembly on two-dimensional nanomaterials has remained a challenge. No et al. (10.1021/ acs.jpclett.7b00996) studied the self-assembly of a twodimensional peptide on pristine graphene based on the optimization of both peptide−peptide and peptide−graphene interactions. They used statistical analyses of naturally occurring β-sheet protein structures as well as atomistic simulations to determine the optimal peptide sequence for stable peptide self-assembly on graphene, and they performed atomic force microscopy experiments to validate the formation of peptide assembly on graphene. The authors found that the experimentally measured structural and surface properties of the peptide self-assemblies formed on graphene were consistent with those predicted from molecular dynamics simulations. The results provide insights into the design principles of peptide self-assembly on a two-dimensional nanomaterial, which could open new avenues for developing novel biomimetic and biocompatible devices.
ATOMIC-LEVEL DESIGN OF WATER-RESISTANT HYBRID PEROVSKITES FOR SOLAR CELLS BY USING CLUSTER IONS
Organic−inorganic hybrid perovskites, exemplified by CH3NH3PbI3, hold the promise to become next-generation solar cell materials because of their simple synthetic route and high power-conversion efficiency. However, their intrinsic instability in the presence of moisture hampers their widespread commercial use. The hybrid perovskite readily decomposes with a trace amount of water, and research is ongoing to develop hybrid perovskites with enhanced water resistance and favorable photoelectric properties. Fang and Jena (10.1021/acs.jpclett.7b01529) report an atomic-level strategy to enhance the intrinsic water resistance of the hybrid perovskite while maintaining its preferred properties, including the optimal bandgap, the decent mobility of charge carriers, and the exceptionally long carrier lifetime. The authors used a special type of cluster ions known as pseudohalides to develop a promising set of water-resistant hybrid perovskites. The authors’ findings suggest that the development of oxygen-free cluster ions with the proper size and low vertical-detachment energy is essential for making hybrid perovskite solar cells with enhanced resistance to moisture. © 2017 American Chemical Society
Published: August 17, 2017 3926
DOI: 10.1021/acs.jpclett.7b02078 J. Phys. Chem. Lett. 2017, 8, 3926−3926
