Externally-triggerable optical pump-probe scanning tunneling microscopy with a time resoloution of tens-picosecond.

Photoinduced carrier dynamics of nanostructures play a crucial role in developing novel functionalities in advanced materials. Optical pump-probe scanning tunneling microscopy (OPP-STM) represents distinctive capabilities of real-space imaging of such carrier dynamics with nanoscale spatial resolution. However, combining the advanced technology of ultrafast pulsed lasers with STM for stable time-resolved measurements has remained challenging.

Versatile Post-Doping toward Two-Dimensional Semiconductors.

We have developed a simple and straightforward way to realize controlled postdoping toward 2D transition metal dichalcogenides (TMDs). The key idea is to use low-kinetic-energy dopant beams and a high-flux chalcogen beam simultaneously, leading to substitutional doping with controlled dopant densities. Atomic-resolution transmission electron microscopy has revealed that dopant atoms injected toward TMDs are incorporated substitutionally into the hexagonal framework of TMDs.

Continuous Heteroepitaxy of Two-Dimensional Heterostructures Based on Layered Chalcogenides.

The in-plane connection and layer-by-layer stacking of atomically thin layered materials are expected to allow the fabrication of two-dimensional (2D) heterostructures with exotic physical properties and future engineering applications. However, it is currently necessary to develop a continuous growth process that allows the assembly of a wide variety of atomic layers without interface degradation, contamination, and/or alloying. Herein, we report the continuous heteroepitaxial growth of 2D multiheterostructures and nanoribbons based on layered transition metal dichalcogenide (TMDC) monolayers, employing metal organic liquid precursors with high supply controllability.

Microscopic basis for the band engineering of Mo1-xWxS2-based heterojunction.

Transition-metal dichalcogenide layered materials, consisting of a transition-metal atomic layer sandwiched by two chalcogen atomic layers, have been attracting considerable attention because of their desirable physical properties for semiconductor devices, and a wide variety of pn junctions, which are essential building blocks for electronic and optoelectronic devices, have been realized using these atomically thin structures. Engineering the electronic/optical properties of semiconductors by using such heterojunctions has been a central concept in semiconductor science and technology. Here, we report the first scanning tunneling microscopy/spectroscopy (STM/STS) study on the electronic structures of a monolayer WS2/Mo1-xWxS2 heterojunction that provides a tunable band alignment.

KDR inhibitor with the intramolecular non-bonded interaction: conformation-activity relationships of novel indole-3-carboxamide derivatives.

We previously reported that compound 1, having a similar conformation to PTK787 (2) by forming a pseudo ring structure with an intramolecular non-bonded S-O interaction, exhibited a potent inhibitory activity against VEGFR2 tyrosine kinase (KDR). Applying the ideas of pseudo ring formations, we have designed three types of novel indole carboxamide derivatives 5-7 with an intramolecular hydrogen bonding or non-bonded S-O interaction. We describe the design and synthesis of 5-7, and also discuss the relationships of their KDR inhibitory activity and conformations that were stabilized by their intramolecular non-bonded interactions.

Solid-phase combinatorial synthesis of aeruginosin derivatives and their biological evaluation.

A 24-member combinatorial library based on the structure of aeruginosin 298-A (1a) was synthesized utilizing solid-phase, and their inhibitory activity against trypsin was evaluated. Among the library, we found that D-Hpla-D-Leu-L-Choi-Agma (1h) is 300 times more potent than the parent natural product 1a.