Important atmospheric and environmental processes involve radical/atom reactions at aqueous interfaces. The mechanisms of interfacial radical/atom reactions are, however, not fully understood, due to the lack of experimental techniques for in-situ monitoring of the intermediates of fast interfacial radical reactions. Here, products and intermediates of the prompt reactions of a variety of aqueous species, including atmospherically relevant carboxylic acids and antioxidant of human epithelial lining fluids, initiated by hydroxyl radicals, iodine atoms, and Criegee intermediates at air-aqueous interfaces are detected by a newly-developed mass spectrometry under ambient conditions. Exposure of sub-millimolar reactant aqueous microjets to gas-phase reactants yielded interfacial species, including peroxyl radicals, that are simultaneously identified in situ by mass spectrometry. Interface-specific mechanisms for the heterogeneous reactions are proposed.
Nanoclusters composed of several to hundreds of atoms exhibit novel, size-specific properties, which cannot be found in their bulk materials. Although the unique characters of nanoclusters encourage utilization of them to functional nanomaterials, the small yield in the conventional nanocluster source limits the applications. We have developed two large-scale synthesis methods with bottom-up approaches; (1) scaling up yield of nanocluster ions enhanced with a high-power impulse magnetron-sputtering under clean reaction environment and (2) refining reaction field of the wet process by a highly miniaturized microfluidic mixer. Size-exclusive synthesis of metal nanoclusters was demonstrated by these methods.
Stimulated by the discovery of high-TC superconductivity in 1986, band-filling-control of strongly-correlated electron systems have been a persistent challenge for past three decades in condensed matter science. Especially, recent efforts have been focused on electrostatic carrier doping of such materials utilizing field-effect transistor (FET) structures to find novel superconductivity. In this paper, recent results on the development of novel superconducting (SC) organic FETs, such as strain-tunable SC FET and light-controllable SC FET are summarized. The techniques and knowledge described here will contribute to the advances in future superconducting electronics as well as the understanding of superconductivity in strongly-correlated electron systems.
Electron spectroscopy combined with a scattering experiment offers a powerful means to study spatial characteristics of a one-electron wavefunction in molecules or in continuum states. Here we review recent developments in such multi-dimensional electron spectroscopy studies which utilize atomic, photonic, and electronic collisions. Particular emphasis is placed on the following three techniques. Firstly, it has been shown that two-dimensional Penning ionization electron spectroscopy, with the help of classical trajectory simulations, leads to a determination of electron distributions of outer valence orbitals extending outside the molecular surface of diatomics. Secondly, an extension of core-level photoelectron angular distribution studies to oriented triatomic non-linear molecules investigated unimolecular photoelectron scattering and diffraction phenomena which can visualize directional information of a photoelectron wave ejected from the core orbital. Thirdly, a recent instrumental development in (e, 2e) electron momentum spectroscopy has made it possible to study the phase, spatial extent, and chemical bonding nature of the molecular orbital of H2 in momentum-space. In addition to the above-mentioned topics, we review our recent efforts towards development of time-resolved electron momentum spectroscopy that employs femtosecond laser and picosecond electron pulses in a pump-probe scheme. In spite of the low data statistics as well as of the limited experimental resolutions, it has been clearly demonstrated that (e, 2e) electron momentum spectroscopy measurements of short-lived transient species are feasible, opening the door to time-resolved orbital imaging in momentum space.
Atomic structures of proteins, nucleic acids, and their complexes are determined using X-ray crystallography, NMR, or cryo-Electron Microscopy. These structures are essential to understand their structure-function relationships. However, the experimental conditions are totally different from the actual cellular environments and it is hard to understand how biomolecules behave in such cellular environments, just using the atomic structures. We have recently built protein crowding systems in computers and carried out all-atom molecular dynamics (MD) simulations of the systems to understand biomolecular dynamics in the crowded environments. The largest simulations we have ever performed were the all-atom MD simulations of a bacterial cytoplasm using K computer. By analyzing the simulation trajectories, we observed that non-specific protein-protein and protein-metabolite interactions play important roles in biomolecular dynamics and stability in a cell. The new insight from the simulations is useful not only for basic life science in molecular and cellular biology but also drug discovery in future for introducing the effect of non-specific protein-drug interactions.
During the past 20 years, the author has made effort to expand the region of time- and space-resolved measurements to contribute to physical chemistry. Although his achievements are yet very far from his initially intended goals, the author describes the background of his ideas to begin new research subjects: 1) how fast liquid phase separation occurs; 2) availability of pulsed x-ray to time-resolved measurements; 3) possibility of sub-molecular spectroscopy for chemical reactions. Problems he faced and suggestions for improvements are also presented.