Ionic Liquids are enigmatic liquids they are salts in liquid phase in room temperature. They have many unique characteristics. Very low vapor pressure prevent ILs from evaporation even in vacuum. High ionic conductivity enable Ils to be an electrolyte in battery. Outstanding dissolution ability allows ILs to dissolve even celluloses and to be a new solvent for biomass conversion. In addition, some ILs form interface with both water and oil. For these unique characteristics, Ionic Liquids are now in the news as new materials beyond common sense of liquid science. While pure scientific researches reveals IL's unique properties applied scientific and engineering researches are utilize ILs for some novel applications: chemical reactants, heavy metal extraction solvent, lithium ion battery, biorefinery, etc.
With the help of some cutting-edge techniques on Spectroscopy, Chemical Calculations and so on, we are deeply studying their physicochemical properties particularly in terms of the correlation between interface/surface structure and electron energy structure, which are related to their unique characteristic and Madelung Energy respectively. Then we will establish new methods of surface property control for their novel function.
Different materials construct interface between them. By interactions of materials, the interface has various structures and characteristics that differ from bulk, and they are exactly souses of many chemical and physical functions like catalytic actions or electrochemical reactions.
The interfaces, which are constructed with gas (gas/liquid and gas/solid), are already studied and analyzed in detail, and elucidated macroscopically (thermodynamically) and microscopically (with nanolevel evaluations). It is included what we call “surface science”. On the other hand, the interfaces, which are constructed between high density layers (liquid/liquid, liquid/solid and solid/solid), are not microscopically elucidated enough. These interfaces, what we call “buried interfaces”, are not able to be analyzed by a usual way of surface science like an ultra-high vacuum environment, therefore it is very difficult to evaluate them microscopically.
We apply IV-SFG to evaluations of buried interfaces, and have aims to understand and to control the correlations between structures and functions.
Infrared-Visible Sum-Frequency Generation Vibrational Spectroscopy
Infrared-Visible Sum Frequency Generation Vibrational Spectroscopy (IV-SFG) is one of spectroscopies using second order non-linear optical effects. It uses the phenomenon: irradiating a sample with a visible light (ωVIS) and an infrared light (ωIR) simultaneously generate light which has energy conservation (ωSF = ωVIS + ωIR). Since this phenomenon is from second order process, it is not come from bulk layers which have spatial symmetry, it is only come from a surface/interface region. Besides, an increase of SFG intensity happens when the energy of the incident infrared light equals the energy of vibrational transition of molecules which are in surface/interface. Because of these phenomena, IV-SFG sweeps wavenumber of the incident infrared light and tells us vibrational spectra of molecules are there. Then, analyzing the data from them theoretically, we can get microscopic information of physical structures, e.g. molecular orientation and conditions of molecular interactions.
Inverse Photoelectron Spectroscopy
Other Experimental Tools
- Spectroscopic ellipsometer
- Surface resistive measurement system
- UV-visible light spectrometer
- FT-IR spectrometer
- Polarization microscope
- Interface tensiometer
- Vacuum deposition equipment
- Electrochemical analyzer