Communications Chemistry最新文献

Lithium metal as a negative electrode material offers ten times the specific capacity of graphitic electrodes, but its rechargeable operation poses challenges like excessive and continuous interphase formation, high surface area lithium deposits and safety issues. Improving the lithium | electrolyte interface and interphase requires powerful surface analysis techniques, such as ToF-SIMS sputter depth profiling.This study investigates lithium metal sections with an SEI layer by ToF-SIMS using different sputter ions. An optimal sputter ion is chosen based on the measured ToF-SIMS sputter depth profiles and SEM analysis of the surface damage. Further, this method is adapted to lithium metal foil with an intermetallic coating. ToF-SIMS sputter depth profiles in both polarities provide comprehensive insights into the coating structure. Both investigations highlight the value of ToF-SIMS sputter depth profiling in lithium metal battery research and offer guidance for future studies.

The knowledge of phase relations of constitutive minerals is essential to investigate the structure, dynamics and evolution of the Earth and planetary interiors. This paper reviews the phase relations of bridgmanite, the most abundant mineral in the Earth's lower mantle, with an ideal composition of MgSiO₃. Bridgmanite has an orthorhombic structure with larger dodecahedral A and smaller octahedral B cation sites. The A-sites can incorporate Mg²⁺, Fe²⁺, Fe³⁺, and Al³⁺, while the B-sites accommodate Si⁴⁺, Al³⁺ and Fe³⁺. The incorporation of hydrogen and large cations like Ca is likely limited, although these issues are still debated. Al³⁺ and Fe³⁺, respectively, can form the charge-coupled components, AlAlO₃ and Fe³⁺Fe³⁺O₃ occupying both A- and B-sites. When both Al³⁺ and Fe³⁺ are present, Al³⁺ occupies B-sites, and Fe³⁺ occupies A-sites, forming Fe³⁺AlO₃. In systems with excess MgO, Al and Fe³⁺ also form the oxygen vacancy components MgAl³⁺O_2.5□_0.5 and MgFe³⁺O_2.5□_0.5. The phase relationships of bridgmanite with coexisting phases are discussed as a function of pressure, temperature, and oxygen fugacity from the simple MgSiO₃ system to the complex MgO-Fe²⁺O-Fe³⁺₂O₃-Al₂O₃-SiO₂ system.

Alkaline exchange membrane fuel cells (AEMFCs) offer a promising alternative to the traditional fossil fuel due to their ability to use inexpensive platinum group metal (PGM)-free catalysts, which could potentially replace Platinum-based catalysts. Iron coordinated in nitrogen-doped carbon (Fe-N-C) single atom electrocatalysts offer the best Pt-free ORR activities. However, most research focuses on material development in alkaline conditions, with limited attention on catalyst layer fabrication. Here, we demonstrate how the oxygen reduction reaction (ORR) performance of a porous Fe-N-C catalyst is affected by the choice of three different commercial ionomers and the ionomer-to-catalyst ratio (I/C). A Mg-templated Fe-N-C is employed as a catalyst owing to the electrochemical accessibility of the Fe sites, and the impact of ionomer properties and coverage were studied and correlated with the electrochemical performance in a gas-diffusion electrode (GDE). The catalyst layer with Nafion at I/C = 2.8 displayed the best activity at high current densities (0.737 ± 0.01 V_{RHE iR-free} at 1 A cm⁻²) owing to a more homogeneous catalyst layer, while Sustainion displayed a higher performance in the kinetic region at the same I/C. These findings provide insights into the impact of catalyst layer optimization to achieve optimal performance in Fe-N-C based AEMFCs.

The thiol-ene reaction between an alkene and a thiol can be exploited for selective labelling of cysteine residues in protein profiling applications. Here, we explore thiol-ene activation in systems from chemical models to complex cellular milieus, using UV, visible wavelength and redox initiators. Initial studies in chemical models required an oxygen-free environment for efficient coupling and showed very poor activation when using a redox initiator. When thiol-ene activation was performed in protein and cell lysate models, all three initiation methods were successful. Faster thiol-ene reaction was observed as the cysteine and alkene were brought into proximity by a binding event prior to activation, leading to quicker adduct formation in the protein model system than the chemical models. Furthermore, in the protein-protein coupling, none of the activators required an oxygen-free environment. Taken together, these observations demonstrate the broad potential for thiol-ene coupling to be used in protein profiling.

Generative models have revolutionized de novo drug design, allowing to produce molecules on-demand with desired physicochemical and pharmacological properties. String based molecular representations, such as SMILES (Simplified Molecular Input Line Entry System) and SELFIES (Self-Referencing Embedded Strings), have played a pivotal role in the success of generative approaches, thanks to their capacity to encode atom- and bond- information and ease-of-generation. However, such 'atom-level' string representations could have certain limitations, in terms of capturing information on chirality, and synthetic accessibility of the corresponding designs.In this paper, we present fragSMILES, a novel fragment-based molecular representation in the form of string. fragSMILES encode fragments in a 'chemically-meaningful' way via a novel graph-reduction approach, allowing to obtain an efficient, interpretable, and expressive molecular representation, which also avoids fragment redundancy. fragSMILES contributes to the field of fragment-based representation, by reporting fragments and their 'breaking' bonds independently. Moreover, fragSMILES also embeds information of molecular chirality, thereby overcoming known limitations of existing string notations. When compared with SMILES, SELFIES and t-SMILES for de novo design, the fragSMILES notation showed its promise in generating molecules with desirable biochemical and scaffolds properties.

Superoxide dismutase 1 (SOD1) aggregation is implicated in the development of Amyotrophic Lateral Sclerosis (ALS). Despite knowledge of the role of SOD1 aggregation, the mechanistic understanding remains elusive. Our investigation aimed to unravel the complex steps involved in SOD1 aggregation associated with ALS. Therefore, we probed the aggregation using ThT fluorescence, size-exclusion chromatography, and surface-enhanced Raman spectroscopy (SERS). The removal of metal ions and disulfide bonds resulted in the dimers rapidly first converting to an extended monomers then coming together slowly to form non-native dimers. The rapid onset of oligomerization happens above critical non-native dimer concentration. Structural features of oligomer was obtained through SERS. The kinetic data supported a fragmentation-dominant mechanism for the fibril formation. Quercetin acts as inhibitor by delaying the formation of non-native dimer and soluble oligomers by decreasing the elongation rate. Thus, results provide significant insights into the critical steps in oligomer formation and their structure.

Photoinduced metal-to-ligand (or ligand-to-metal) charge-transfer (CT) states in metal complexes have been extensively studied toward the development of luminescent materials. However, previous studies have mainly focused on CT transitions between d- and π-orbitals. Herein, we report the demonstration of CT emission from 4f- to π-orbitals using a trivalent europium (Eu(III)) complex, supported by both experimental and theoretical analyses. The Eu(III) complex exhibits an eight-coordination structure, comprising three anionic nitrates and two neutral electron-donating ligands containing a carbazole unit. The diffuse reflectance spectrum of the complex displays an absorption band at 440 nm and time-resolved emission analyses reveal a characteristic emission band at 550 nm. Comparative studies employing a trivalent gadolinium (Gd(III)) complex, alongside quantum chemical analyses, confirm that the observed absorption and emission bands are associated with CT transitions between π- and 4f-orbitals. The observation of CT emission based on the 4f-orbital offers novel insights into the field of molecular luminescence science and technology.

The interplay between attractive London dispersion forces and steric effects due to repulsive forces resulting from the Pauli principle often determines the geometry and stability of nanostructures. Aromatic polyimides (PI) and carbon nanotubes (CNT) were chosen as building blocks as two components in the hetero delocalized electron nanostructures. Two PIs, having the same diamine part and different linkage substituents between two phenyl rings of dianhydride part, one linked with ether bond (C-O-C) (OPI), the other with C-(CF3)2 (FPI), were investigated. Surprisingly, two CNT/PI nanocomposites show distinct failure mode from CNT yielding to CNT pull-out failure. Calculation of the interaction energy and chain conformations of each PI upon CNT was performed by accurate density functional theory (DFT) calculations and molecular dynamic simulation (MDS). OPI chain adopt helically wrapping conformation around CNT with relatively strong interaction energy. FPI chain take the one-side wavelike conformation upon CNT with relatively weak interaction energy.

Aqueous Zn batteries are gaining increasing research attention in the energy storage area due to their intrinsic safety, potentially low cost and environmental friendliness; however, the zinc dendrite formation, zinc corrosion, passivation and the hydrogen evolution reaction induced by water at the anode side, and materials dissolution as well as intrinsic poor reaction kinetics at cathode side in aqueous systems, seriously shorten the cycling life and decrease energy density of batteries and greatly hinder their development. Recent advancements in asymmetric electrolytes with various functions are promising to overcome such challenges for zinc batteries at the same time. It has been proved that the applications of asymmetric electrolytes show significant contributions in the field of zinc-based batteries in suppressing side reactions while maintaining electrochemical performance to satisfy both anode and cathode. Therefore, this perspective summarizes recent advancements in asymmetric electrolytes' design and applications for zinc batteries and outlines opportunities and future challenges, expecting continued research attention in this area.