High-Resolution Electrochemical Mapping of the Hydrogen Evolution Reaction on Transition-Metal Dichalcogenide Nanosheets

High-resolution scanning electrochemical cell microscopy (SECCM) is used to image and quantitatively analyze the hydrogen evolution reaction (HER) catalytically active sites of 1H-MoS₂ nanosheets, MoS₂, and WS₂ heteronanosheets. Using a 20 nm radius nanopipette and hopping mode scanning, the resolution of SECCM was beyond the optical microscopy limit and visualized a small triangular MoS₂ nanosheet with a side length of ca. 130 nm. The electrochemical cell provides local cyclic voltammograms with a nanoscale spatial resolution for visualizing HER active sites as electrochemical images. The HER activity difference of edge, terrace, and heterojunction of MoS₂ and WS₂ were revealed. The SECCM imaging directly visualized the relationship of HER activity and number of MoS₂ nanosheet layers and unveiled the heterogeneous aging state of MoS₂ nanosheets. SECCM can be used for improving local HER activities by producing sulfur vacancies using electrochemical reaction at the selected region.     

A Tray‐Shaped,PdII‐Clipped Au3 Complex as a Scaffold for the Modular Assembly of [3×n] Au Ion Clusters

A tray‐shaped Pd^II₃Au^I₃ complex ( 1 ) is prepared from 3,5‐bis(3‐pyridyl)pyrazole by means of tricyclization with Au^I followed by Pd^II clipping. Tray 1 is an efficient scaffold for the modular assembly of [3×n] Au^I clusters. Treatment of 1 with the Au^I₃ tricyclic guest 2 in H₂O/CH₃CN (7:3) or H₂O results in the selective formation of a [3×2] cluster ( 1 ? 2 ) or a [3×3] cluster ( 1 ? 2 ? 1 ), respectively. Upon subsequent addition of Ag^I ions, these complexes are converted to an unprecedented Au₃–Au₃–Ag–Au₃–Au₃ metal ion cluster.     

Theoretical Modeling of Low‐Energy Electronic Absorption Bands in Reduced Cobaloximes

The reduced Co^I states of cobaloximes are powerful nucleophiles that play an important role in the hydrogen‐evolving catalytic activity of these species. In this work we analyze the low‐energy electronic absorption bands of two cobaloxime systems experimentally and use a variety of density functional theory and molecular orbital ab initio quantum chemical approaches. Overall we find a reasonable qualitative understanding of the electronic excitation spectra of these compounds but show that obtaining quantitative results remains a challenging task.     

Laser spectroscopy of atoms in superfluid helium for the measurement of nuclear spins and electromagnetic moments of radioactive atoms

A new laser spectroscopic method named “OROCHI (Optical RI-atom Observation in Condensed Helium as Ion catcher)” has been developed for deriving the nuclear spins and electromagnetic moments of low-yield exotic nuclei. In this method, we observe atomic Zeeman and hyperfine structures using laser-radio-frequency/microwave double-resonance spectroscopy. In our previous works, double-resonance spectroscopy was performed successfully with laser-sputtered stable atoms including non-alkali Au atoms as well as alkali Rb and Cs atoms. Following these works, measurements with ^84?87Rb energetic ion beams were carried out in the RIKEN projectile fragment separator (RIPS). In this paper, we report the present status of OROCHI and discuss its feasibility, especially for low-yield nuclei such as unstable Au isotopes.     

DNA Terminal Mismatch‐Induced Stabilization of Polymer Micelles from RAFT‐Generated Poly(N‐isopropylacrylamide)‐DNA Block Copolymers

Temperature‐responsive diblock copolymers made of poly(N‐isopropylacrylamide) (PNIPAAm) generated by reversible addition‐fragmentation chain transfer (RAFT) polymerization and a single‐stranded DNA (ssDNA) self‐assembled into polymer micelles. The micelles consisted of the PNIPAAm core surrounded by the ssDNA corona with a hydrodynamic diameter up to 300 nm in an aqueous medium above the lower critical solution temperature. In a medium of high ionic strength, the formation of the fully matched duplex with the complementary ssDNA on the surface of the polymer micelles induced rapid and spontaneous aggregation. By contrast, the micelles remained dispersed under the identical conditions when single‐base‐substituted ssDNA was added to form the corresponding terminal‐mismatched duplex on the micellar surface. This highly sequence‐selective process took place irrespective of the size of the PNIPAAm core.     

Mesogenic Unsymmetric dimers containing cholesteryl ester and tolane moieties

Among unsymmetric oligomesogens, chiral dimers formed by connecting a cholesteryl ester fragment with various aromatic mesogenic cores through a polymethylene spacer have been attracting much attention due to their remarkable thermal behaviour. In particular, dimers containing a diphenylacetylene segment having an alkoxy chain have shown interesting mesomorphic behaviour. In view of this a new series of unsymmetric dimers consisting of a diphenylacetylene moiety having an alkyl chain and a cholesteryl ester unit joined through a paraffinic spacer have been synthesized and their liquid crystalline properties characterized. The lengths of the central methylene spacer (C₃, C₄, C₅ and C₇) as well as that of the alkyl chain (n-butyl, n-pentyl, n-hexyl and n-heptyl) have been varied to establish structure–property relationships. These investigations have revealed that all the dimers exhibit smectic A, twist grain boundary and chiral neamtic (N*) phases with the exception of one of the dimers for which only the N* phase was observed. Some differences in the mesomorphic properties of the unsymmetric dimers containing odd or even parity methylene spacers have been observed. The majority of dimers having an even (C₄) parity paraffinic spacer show a blue phase while the dimers with odd (C₃, C₅ and C₇) parity spacers exhibit the chiral smectic (SmC*) phase. In some cases, the SmC* phase exists well below (?60°C) and above room temperature.