Dynamic of water molecule in the nano-porous silica and its surface effect

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In this research, an in-situ water adsorption system was constructed and neutron quasi-elastic had been performed. New information concerning adsorbed water molecule in the nano-porous silica (FSM) were obtained by analysis based on Jump Diffusion Model.1) The dynamics of water molecules in the nano-pore can be analyzed by separating two types of molecules ; one is confined on the pore surface (monolayer water) and the other is free from the surface.2) The diffusion constant (～10^<-9>m^2s^<-1>) and activation energy (～2.5kcal/mol) of the monolayer water are about half of bulk water.3) The residential time before diffusion jumping is 5 times longer than bulk water.4) The other water shows similar diffusion behavior (～2.7×10^<-8>m^2s^<-1> and ～4.7kcal/mol) to bulk water.To understand the diffusion behavior in atomic level, neutron and X-ray diffraction had been performed. Diffraction profiles measured by in-situ adsorption technique show water adsorption behavior into the nano-pores but the structural analysis has not been finished yet. The glassy structure of FSM skeleton need to be investigated as well as controlling the content of hydrogen atoms and/or substitution to deuterium in the FSM. Inelastic scattering of FSM skeleton itself may be useful to understand the glassy structure.