My Research History on the Chemical Standpoint—From Molecular Structure to Surface Science

The structure of molecules using gas electron diffraction (GED) was my graduate study. However, I was making a new apparatus for precise measurements by GED and formulated a scheme for the least‐squares analysis for a smooth continuous curve of scattering intensity. My research was completely shifted to the solid surface after moving to Gakushuin University, where I briefly studied the liquid structure of CCl₄ molecules, and I then moved to the Institute for Solid State Physics, the University of Tokyo. My studies of surface science were focused on the electronic properties and related phenomena, and various experimental methods were developed. The plasmon dispersions elucidated the initial oxidation of aluminum and one‐dimensional metal on Si(001)2 × 1–K. Irreversible phase transition was discovered on MgO(001) using the LEED Kikuchi pattern. The electronic structure of the dislocation was observed on MgO(001) by the electron time‐of‐flight method. The phase transition on Si(001) and the rotational epitaxy in a K monoatomic layer on Cu(001) were found. Next, I changed to studies of the dynamical phenomena on the surface, where very low energy reactive ion scattering on metal surfaces and laser‐induced desorption caused by electronic transition of NO and CO molecules from metal surfaces were observed, and the hydrogen atom location at the surface and interface was measured with a high depth resolution using a resonance nuclear reaction of ¹H + ¹⁵N²⁺ at 6.385 MeV. Finally, I moved to the University of Electro‐Communications and studied thin single‐crystal oxide layers on transition metals, in which the band‐gap narrowing was found, and then a Pt monoatomic layer was prepared on the α‐Al₂O₃ film.     

我国铀表面科学研究进展

金属铀在核能工业和国防领域有重要的应用,由于其化学活性大,在贮存环境中容易发生严重的腐蚀。为寻求有效的表面抗腐蚀方法,围绕铀及其合金的表面腐蚀行为,我国开展了大量的科学研究,摸索并改进铀材料的表面改性工作,为工程化应用提供相应的技术支撑。本文综述了近十年来我国在铀表面科学的研究进展,并对下一步研究方向进行了展望。     

Vacuum Surface Science Meets Heterogeneous Catalysis: Dehydrogenation of a Liquid Organic Hydrogen Carrier in the Liquid State

Ultrahigh vacuum (UHV) surface science techniques are used to study the heterogeneous catalytic dehydrogenation of a liquid organic hydrogen carrier in its liquid state close to the conditions of real catalysis. For this purpose, perhydrocarbazole (PH), otherwise volatile under UHV, is covalently linked as functional group to an imidazolium cation, forming a non‐volatile ionic liquid (IL). The catalysed dehydrogenation of the PH unit as a function of temperature is investigated for a Pt foil covered by a macroscopically thick PH‐IL film and for Pd particles suspended in the PH‐IL film, and for PH‐IL on Au as inert support. X‐ray photoelectron spectroscopy and thermal desorption spectroscopy allows us to follow in situ the catalysed transition of perhydrocarbazole to carbazole at technical reaction temperatures. The data demonstrate the crucial role of the Pt and Pd catalysts in order to shift the dehydrogenation temperature below the critical temperature of thermal decomposition.     

Highly Dense Isolated Metal Atom Catalytic Sites: Dynamic Formation and In Situ Observations

Atomically dispersed noble‐metal catalysts with highly dense active sites are promising materials with which to maximise metal efficiency and to enhance catalytic performance; however, their fabrication remains challenging because metal atoms are prone to sintering, especially at a high metal loading. A dynamic process of formation of isolated metal atom catalytic sites on the surface of the support, which was achieved starting from silver nanoparticles by using a thermal surface‐mediated diffusion method, was observed directly by using in situ electron microscopy and in situ synchrotron X‐ray diffraction. A combination of electron microscopy images with X‐ray absorption spectra demonstrated that the silver atoms were anchored on five‐fold oxygen‐terminated cavities on the surface of the support to form highly dense isolated metal active sites, leading to excellent reactivity in catalytic oxidation at low temperature. This work provides a general strategy for designing atomically dispersed noble‐metal catalysts with highly dense active sites.     

Recent progress in EPR study of spin labeled polymers and spin probed polymer systems

The EPR technique is commonly used for the detection and characterization of paramagnetic centers in chemical science. This method can provides a lot of information, such as identity, structure, dynamics, interaction, orientation, glass transition temperature, adsorption behavior, functionality, phase behavior, nano-inhomogeneities, and conformation of the free-radical portion of the polymer chain. Most polymers intrinsically possess diamagnetic properties, so in order to study polymers with EPR, paramagnetic centers need to be incorporated into the polymer systems. Spin labeling and spin probing are main methods of covalently attaching paramagnetic centers to polymer chains or embedding them in polymer matrices through non-covalent interactions, respectively. Spin labeling and spin probing techniques for polymers and polymer systems (especially with nitroxide radicals) have also been studied, which have a profound impact on polymer science. This review focuses on the continuous wave EPR technique and introduces the recent advances in spin labeled polymers and spin probed polymer systems in EPR research.     

Investigation of the Nature of Iron Oxide Species Present in Ruby Glasses Prepared by the Sol-Gel Method

Mössbauer spectroscopy in an external magnetic field, electron diffraction microscopy and electron spin resonance (ESR) measurements were used in an attempt to characterize the iron oxide particles present in ruby glasses prepared by the sol-gel method. The obtained results lead to the conclusion that particles are present as a ferromagnetic phase that shows superparamagnetic behaviour.     

Plasma Techniques for Preparation of Controlled Drug Release System

Plasma-induced surface radicals formed on a variety of organic polymers have been studied by electron spin resonance (ESR), making it possible to provide a sound basis for future experimental design of polymer surface processing, i.e., plasma treatment. On the basis of the findings from such studies, several pharmaceutical applications in the field of drug engineering have been devised, which include preparation of double-compressed tablets for reservoir-type drug delivery system (DDS) of sustained- and delayed-release, and fabrication of functionalized composite powders applicable for matrix-type DDS by a mechanical application of plasma-irradiated polymer powder.     

Ligand Control over the Electronic Properties within the Metallic Core of Gold Nanoparticles

The behavior of electrons within the metallic core of gold nanoparticles (AuNPs) can be controlled by the nature of the surface chemistry of the AuNPs. Specifically, the conduction electron spin resonance (CESR) spectra of AuNPs of diameter 1.8–1.9 nm are sensitive to ligand exchange of hexanethiol for 4‐bromothiophenol on the surface of the nanoparticle. Chemisorption of the aromatic ligand leads to a shift in the metallic electron’s g‐factor toward the value expected for pure gold systems, suggesting an increase in metallic character for the electrons within the gold core. Analysis by UV/Vis absorption spectroscopy reveals a concomitant bathochromic shift of the surface plasmon resonance band of the AuNP, indicating that other electronic properties of AuNPs are also affected by the ligand exchange. In total, our results demonstrate that the chemical nature of the ligand controls the valence band structure of AuNPs.     

Tunneling spectroscopy of single electron spin

The possibility of detection of the electron spin of a single paramagnetic species (an atom, a radical, or an ion) on the surface was discussed. The analysis was based on spin chemistry laws taking into account the statistics of the spin states of both the tunneling electron and paramagnetic center. The equations for the tunneling current as a function of temperature and magnetic field strength were derived. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1732–1734, September, 1998.     

Interaction of an Endosomolytic Polyamidoamine ISA23 with Vesicles Mimicking Intracellular Membranes: A SANS/EPR Study

The mechanism of ISA23 · HCl interaction with model membrane vesicles (80–100 nm in diameter) was investigated using EPR in conjunction with SANS. For EPR, 16‐DSE was dissolved in the vesicle membrane to measure its dynamics and polarity, whereas a spin‐labeled (Tempo)‐ISA 23 analogue was used to give a measure of the polymer flexibility. When ISA23 was added to the external vesicle surface, no interaction was found. This observation conflicts with the reported ability to lyse RBC, but is in agreement with recent studies that showed no effect on membrane permeability when a PAA was added to an incubation medium containing isolated lysosomal vesicles. The vesicle‐mimetic models used here provide a new and useful tool for studying endosomolytic polymer/membrane interactions.

     

利用ESR技术研究α-蒎烯,β-蒎烯光敏氧化反应机理

本文主要利用电子顺磁共振(ESR)自旋捕获技术研究9,10 二氰基蒽(DCA)敏化α-蒎烯(αP),β-蒎烯(βP)光氧化反应.提供了在乙腈中α-蒎烯和β-蒎烯的光氧化反应过程中存在超氧负离子基(O₂^-)和单重态氧(¹O₂)的直接证据;在四氯化碳溶剂中只捕获到¹O₂;在正己烷中没有捕获到O₂^-或¹O₂.ESR实验结果进一步证明在乙腈中光敏氧化反应的¹O₂可能来自O₂^-和反应底物α、β-蒎烯正离子自由基之间的电荷复合(CR).     

Catalytic Active Site for NO Decomposition Elucidated by Surface Science and Real Catalyst

Comprehensive studies combining surface science and real catalyst were performed to get further insight into catalytic active site and reaction mechanism for NO decomposition over supported palladium and cobalt oxide-based catalysts. On palladium single-crystal model catalysts, adsorption, dissociation and desorption behavior of NO was found to be closely related to the surface structures, the stepped surface palladium being active for dissociation of NO. In accordance with this result, the activity of powder Pd/Al₂O₃ catalysts for NO decomposition was directly related to the number of step sites exposed on the surface, suggesting that the step sites act as the catalytic active site for NO decomposition on Pd/Al₂O₃. NO decomposition over cobalt oxide was found to be significantly promoted by addition of alkali metals. Surface science study and catalyst characterization led to the same conclusion that the interface between the alkali metal and Co₃O₄ serves as the catalytic active site. From the results of in situ Fourier transform infrared (FT-IR) spectroscopy and isotopic transient kinetic analysis, a reaction mechanism was proposed in which the reaction is initiated by NO adsorption onto alkali metals to form NO₂⁻ species and then NO₂⁻ species react with the adsorbed NO species to form N₂ over the interface between the alkali metal and Co₃O₄.     

用电子自旋共振谱研究我国一些煤的自由基

本文用电子自旋共振谱(ESR)研究了我国十种不同变质程度的煤。电子自旋共振最重要的参数是g值、自由基的浓度、线宽和线形。用这些参数与煤中的碳、氧等元素相关联,发现ESR参数与煤的变质程度有密切关系。     

新型水溶性硫杂蒽酮类光引发剂的光化学性能研究

本文对8种水溶性硫杂蒽酮类光引发剂进行了紫外 可见光谱、荧光光谱以及电子自旋共振光谱(ESR)等测试。测定了最大吸收波长,计算了摩尔消光系数,荧光量子产率,测定了ESR信号强度等。并对其结构与光化学性能之间的关系进行了讨论。