Recent advances in the development of two-dimensional (2D) materials have facilitated a wide variety of surface chemical characteristics obtained by composing atomic species, pore functionalization, etc. The present study focused on how chemical characteristics such as hydrophilicity affects the water transport rate in hexagonal 2D membranes. The membrane–water interaction strength was tuned to change the hydrophilicity, and the sub-nanometer pore was used to investigate single-file flux, which is known to retain excellent salt rejection. Due to the dewetting behavior of the hydrophobic pore, the water flux was zero or nominal below the threshold interaction strength. Above the threshold interaction strength, water flux decreased with an increase in interaction strength. From the potential of mean force analysis and diffusion coefficient calculations, the proximal region of the pore entrance was found to be the dominant factor degrading water flux at the highly hydrophilic pore. Furthermore, the superiority of 2D membranes over 3D membranes appeared to depend on the interaction strength. The present findings will have implications in the design of 2D membranes to retain a high water filtration rate.

Aromatic π–π interaction in the presence of a metal atom has been investigated experimentally and theoretically with the model system of bis(η6-benzene)chromium–benzene cluster (Cr(Bz)2–Bz) in which a free solvating benzene is non-covalently attached to the benzene moiety of Cr(Bz)2. One-photon mass-analyzed threshold ionization (MATI) spectroscopy and first principles calculations are employed to identify the structure of Cr(Bz)2–Bz which adopts the parallel-displaced configuration. The decrease in ionization potential for Cr(Bz)2–Bz compared with Cr(Bz)2, resulting from the increase of the cation–π stabilization energy upon ionization, is consistent with the parallel-displaced structure of the cluster. Theoretical calculations give the detailed cluster structures with associated energetics, thus revealing the nature of π–π–metal or π–π–cation interactions at the molecular level. Graphic AbstractThe nature of the aromatic π–π interaction in the presence of a metal atom has been revealed by the combined study of ionization spectroscopy and first principles calculations for the model system of the Cr(C6H6)2–C6H6 cluster.

A novel anthraquinone-imidazole based colorimetric and fluorogenic probe 1 is synthesized, which can discriminate the oxidation states of palladium (Pd0 and Pd2+) by naked eye with high selectivity in aqueous media owing to the difference in coordination within the right sized pocket of the probe molecule. The experimental results (fluorescence, UV/Vis and 1H NMR spectroscopy) aided by density functional theory (DFT) calculations reveal that charge transfer (CT) is the main cause of the selective detection of the oxidation states of palladium. In the 1-Pd2+ complex, which is deficient in electrons, all the electron transitions represent electron transfers from the probe molecule to the central metal atom i.e. partial ligand-to-metal transition excitation while electronically filled Pd0 shows electron transfers from the metal atom to the probe ligand i.e. partial metal-to-ligand transition excitation.

We theoretically elucidate the origin of unintentional doping in two-dimensional transition-metal dichalcogenides (TMDs), which has been consistently reported by experiment, but which still remains unclear. Our explanation is based on the charge transfer between TMDs and the underlying SiO2 in which hydrogen impurities with a negative-U property pin the Fermi level of the SiO2 as well as adjacent TMD layers. Using first-principles calculations, we obtain the pinning point of the Fermi level from the charge transition level of the hydrogen in the SiO2, epsilon(+/-), and align it with respect to the band-edge positions of monolayer TMDs. The computational results show that the Fermi levels of TMDs estimated by epsilon(+/-) successfully explain the conducting polarity (n-or p-type) and relative doping concentrations of thin TMD films. By enlightening on the microscopic origin of unintentional doping in TMDs, we believe that the present work will contribute to precise control of TMD-based electronic devices.

Shear is an effective method to create long-range order in micro- or nanostructured soft materials. When simple shear flow is applied, particles or polymer microdomains tend to align in the shear direction to minimize viscous dissipation; thus, transverse alignment (so-called log-rolling) is not typically favored. This is the first study to report the transverse alignment of cylinder-forming coil coil block copolymers. Poly(styrene-b-methyl methacrylate), PS PMMA, where the PS blocks form the matrix, can adopt a metastable PMMA hemicylindrical structure when confined in a thin film, and this hemicylindrical structure can orient either along the shear direction or transverse to the shear direction depending on the shearing temperature. A monolayer of PS PMMA forming full cylinders exhibits log-rolling alignment. This unusual log-rolling behavior is explained by the low chain mobility of the cylinder-forming PMMA block at low temperatures, which is direction of shear alignment. the critical quantity determining the