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Ito, Eisuke,Hara, Masahiko,Kanai, Kaname,Ouchi, Yukio,Seki, Kazuhiko,Noh, Jaegeun Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.8
Surface structure and molecular orientation of self-assembled monolayers (SAMs) formed by the spontaneous adsorption of tetrahydrothiophene (THT) and thiophene (TP) on Au(111) were investigated by means of scanning tunneling microscopy (STM) and carbon K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. STM imaging revealed that THT SAMs have a commensurate (3 ${\times}\;2\sqrt[]{3}$) structure containing structural defects in ordered domains, whereas TP SAMs are composed of randomly adsorbed domains and paired molecular row domains that can be described as an incommensurate packing structure. The NEXAFS spectroscopy study showed that the average tilt angle of the aliphatic THT ring and $\pi$-conjugated TP ring in the SAMs were calculated to be about $30^o\;and\;40^o$, respectively, from the surface normal. It was also observed that the $\pi$* transition peak in the NEXAFS spectrum of the TP SAMs is very weak, suggesting that a strong interaction between $\pi$-electrons and the Au surface arises during the self-assembly of TP molecules. In this study, we have clearly demonstrated that the surface structure and adsorption orientation of organic SAMs on Au(111) are strongly influenced by whether the cyclic ring is saturated or unsaturated.
Eisuke Ito,Masahiko Hara,Kaname Kanai,Yukio Ouchi,Kazuhiko Seki,노재근 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.8
Surface structure and molecular orientation of self-assembled monolayers (SAMs) formed by the spontaneous adsorption of tetrahydrothiophene (THT) and thiophene (TP) on Au(111) were investigated by means of scanning tunneling microscopy (STM) and carbon K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. STM imaging revealed that THT SAMs have a commensurate (3 × 2√3) structure containing structural defects in ordered domains, whereas TP SAMs are composed of randomly adsorbed domains and paired molecular row domains that can be described as an incommensurate packing structure. The NEXAFS spectroscopy study showed that the average tilt angle of the aliphatic THT ring and π-conjugated TP ring in the SAMs were calculated to be about 30o and 40o, respectively, from the surface normal. It was also observed that the π* transition peak in the NEXAFS spectrum of the TP SAMs is very weak, suggesting that a strong interaction between π-electrons and the Au surface arises during the self-assembly of TP molecules. In this study, we have clearly demonstrated that the surface structure and adsorption orientation of organic SAMs on Au(111) are strongly influenced by whether the cyclic ring is saturated or unsaturated.
Subdiffusion-assisted reaction kinetics in disordered media
Kim, Ji-Hyun,Huh, Dann,Lee, Jinuk,Lee, Sangyoub,Sung, Jaeyoung,Seki, Kazuhiko,Tachiya, M IOP Pub 2007 Journal of Physics, Condensed Matter Vol.19 No.6
<P>We present a theory for describing the reaction process occurring in disordered media with energetically disordered trapping sites and spatial constraints. The theory is based on a generalized fractional reaction–diffusion equation, which describes the time evolution of the mean distribution of a particle performing a continuous time random walk on a fractal network. The motion of a particle is subdiffusive because of the spatial constraints and/or the random detrapping times described by a waiting time distribution given by ψ(<I>t</I>)∼<I>t</I><SUP>−(1+α)</SUP> with 0<α<1. Assuming that the reaction occurs at a separation of contact, the reaction and transport processes are decoupled and the kinetic information for the reaction is expressed in terms of the reaction-free Green’s function obtained with the reflecting boundary condition at the separation of contact. The survival probability of a reactant pair is shown to decay asymptotically as τ<SUP>−α|<I>d</I><SUB>s</SUB>/2−1|</SUP>, where <I>d</I><SUB>s</SUB> is the fracton dimension of the fractal network under consideration. We also check the validity of the analytical results by comparison with Monte Carlo simulation results.</P>