Predictable Synthesis of 3D Polymer Networks Using Crystal Component-Linking

Controlled synthesis of 3D polymer networks presents a significant challenge because of the complexity of the polymerization reaction in solution. In this study, a polymerization system that facilitates the prediction of a polymer network structure via percolation simulations is realized. The most significant difference between general percolation simulations and experimental polymerization systems is the mobility of the molecules during the reaction. A crystal component-linking method that connects the precisely arranged monomer as a supramolecular crystalline state to imitate the simple percolation theory is adopted. The percolation simulation based on the crystal structure of the arranged monomers is used to accurately calculate the gelation point, gel fraction, degree of swelling, and atomic formula, which correspond with the experimental results. This suggests that the network structures polymerized via the crystal component-linking method can be predicted precisely by a simple percolation simulation. Further, the percolation simulation predicts the structures of the loop, branched polymer, and crosslinking point, which are difficult to measure experimentally. The polymerization of precisely-arranged immobilized monomers in supramolecular structures is promising in synthesizing precisely controlled polymer networks.

Dynamic Variation of Rectification Observed in Supramolecular Mixed Mercaptoalkanoic Acid

Functionality in molecular electronics relies on inclusion of molecular orbital energy level within a transmission window. This can be achieved by designing the active molecule with accessible energy levels or by widening the window. While many studies have adopted the first approach, the latter is challenging because defects in the active molecular component cause low breakdown voltages. Here, it is shown that control over the packing structure of monolayer via supramolecular mixing transforms an inert molecule into a highly tunable rectifier. Binary mixed monolayer composed of alkanethiolates with and without carboxylic acid head group as a proof of concept is formed via a surface-exchange reaction. The monolayer withstands high voltages up to |4.5 V| and shows a dynamic rectification-external bias relationship in magnitude and polarity. Sub-highest occupied molecular orbital (HOMO) levels activated by the widened transmission window account for these observations. This work demonstrates that simple supramolecular mixing can imbue new electrical properties in electro-inactive organic molecules.

Moiré-Assisted Realization of Octahedral MoTe2 Monolayer

A current key challenge in 2D materials is the realization of emergent quantum phenomena in hetero structures via controlling the moiré potential created by the periodicity mismatch between adjacent layers, as highlighted by the discovery of superconductivity in twisted bilayer graphene. Generally, the lattice structure of the original host material remains unchanged even after the moiré superlattice is formed. However, much less attention is paid for the possibility that the moiré potential can also modify the original crystal structure itself. Here, it is demonstrated that octahedral MoTe2 which is unstable in bulk is stabilized in a commensurate MoTe2 /graphene hetero-bilayer due to the moiré potential created between the two layers. It is found that the reconstruction of electronic states via the moiré potential is responsible for this stabilization, as evidenced by the energy-gap opening at the Fermi level observed by angle-resolved photoemission and scanning tunneling spectroscopies. The present results provide a fresh approach to realize novel 2D quantum phases by utilizing the moiré potential.

Chiral Van Der Waals Superlattices for Enhanced Spin-Selective Transport and Spin-Dependent Electrocatalytic Performance

The emergence of the chiral-induced spin-selectivity (CISS) effect offers a new avenue for chiral organic molecules to autonomously manipulate spin configurations, thereby opening up possibilities in spintronics and spin-dependent electrochemical applications. Despite extensive exploration of various chiral systems as spin filters, one often encounters challenges in achieving simultaneously high conductivity and high spin polarization (SP). In this study, a promising chiral van der Waals superlattice, specifically the chiral TiS2 crystal, is synthesized via electrochemical intercalation of chiral molecules into a metallic TiS2 single crystal. Multiple tunneling processes within the highly ordered chiral layered structure of chiral TiS2 superlattices result in an exceptionally high SP exceeding 90%. This remarkable observation of significantly high SP within the linear transport regime is unprecedented. Furthermore, the chiral TiS2 electrode exhibits enhanced catalytic activity for oxygen evolution reaction (OER) due to its remarkable spin-selectivity for triplet oxygen evolution. The OER performance of chiral TiS2 superlattice crystals presented here exhibits superior characteristics to previously reported chiral MoS2 catalysts, with an approximately tenfold increase in current density. The combination of metallic conductivity and high SP sets the stage for the development of a new generation of CISS materials, enabling a wide range of electron spin-based applications.

Suppression of Methanol and Formate Crossover through Sulfanilic-Functionalized Holey Graphene as Proton Exchange Membranes

Proton exchange membranes with high proton conductivity and low crossover of fuel molecules are required to realize advanced fuel-cell technology. The selective transportation of protons, which occurs by blocking the transportation of fuel molecules across a proton exchange membrane, is crucial to suppress crossover while maintaining a high proton conductivity. In this study, a simple yet powerful method is proposed for optimizing the crossover-conductivity relationship by pasting sulfanilic-functionalized holey graphenes onto a Nafion membrane. The results show that the sulfanilic-functionalized holey graphenes supported by the membrane suppresses the crossover by 89% in methanol and 80% in formate compared with that in the self-assembled Nafion membrane; an ≈60% reduction is observed in the proton conductivity. This method exhibits the potential for application in advanced fuel cells that use methanol and formic acid as chemical fuels to achieve high energy efficiency.

A Closed Cavity Strategy for Selective Dipeptide Binding by a Polyaromatic Receptor in Water

Precise recognition of peptides is a daunting task owing to the substantial number of available amino acids and their combination into various oligo/polymeric structures in addition to the high hydration of their flexible frameworks. Here, we report the selective recognition of a dipeptide through a closed cavity strategy, in contrast to previous synthetic receptors with open cavities. A polyaromatic receptor with a virtually isolated, hydrophobic cavity exclusively binds one molecule of phenylalanine dipeptide from a mixture with its amino acid and tripeptide in water via multiple CH-π and hydrogen-bonding interactions in the complementary cavity. The binding selectivity persists even in the presence of other dipeptides, such as leucine-leucine, leucine-phenylalanine, tyrosine-phenylalanine, tryptophan-tryptophan, and aspartame, revealed by NMR/MS-based competitive binding experiments. ITC studies reveal that the selective binding of the phenylalanine dipeptide is relatively strong (Ka = 1.1 × 105 M-1) and an enthalpically and entropically favorable process (ΔH = -11.7 kJ mol-1 and TΔS = 17.0 kJ mol-1). In addition, the present receptor can be used for the emission detection of the dipeptide through a combination with a fluorescent dye in water.

Dopamine stimulation of the septum enhances exercise efficiency during complicated treadmill running in mice

We aimed to identify the neurotransmitters and brain regions involved in exercise efficiency in mice during continuous complicated exercises. Male C57BL/6J mice practiced treadmill running with intermittent obstacles on a treadmill for 8 days. Oxygen uptake (VO2) during treadmill running was measured as exercise efficiency. After obstacle exercise training, the VO2 measured during treadmill running with obstacles decreased significantly. Obstacle exercise-induced c-Fos expressions and dopamine turnover (DOPAC/dopamine) in the septum after obstacle exercise training were significantly higher than that before training. The dopamine turnover was correlated with exercise efficiency on the 3rd day after exercise training. Furthermore, the training effect on exercise efficiency was significantly decreased by injection of dopamine receptor antagonists into the septum and was associated with decreased c-Fos expressions in the septum and hippocampus of the mice. These results suggest that dopaminergic function in the septum is involved in exercise efficiency during continuous complicated exercises.