Hiro-o Hamaguchi

Structural Change of 1-Butyl-3-methylimidazolium Tetrafluoroborate + Water Mixtures Studied by Infrared Vibrational Spectroscopy

Mixtures of ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]) and water with varying concentrations were studied by attenuated total reflection infrared absorption and Raman spectroscopy. Changes in the peak intensities and peak positions of CHx (x = 1, 2, 3) vibration modes of the cation of the IL and OH vibration modes of the water molecules were investigated. Peaks from normal-mode stretch vibrations of CH bonds belonging to the imidazolium ring of the cation did not change their positions, while those from the terminal methyl group of the butyl chain blueshifted by approximately 10 cm-1 with the addition of water. On the other hand, change in the spectral shape in the OH stretch vibration region shows hydrogen-bonding network of water molecules breaking down rapidly as the IL is added. Trends in the change of the peak positions and the peak intensities suggested qualitative change of the intermolecular structure in the [BMIM][BF4] + H2O mixture at 32 +/- 2 and 45 +/- 2 mol/L of water concentration.

Vibrationally resonant imaging of a single living cell by supercontinuum-based multiplex coherent anti-Stokes Raman scattering microspectroscopy

Supercontinuum-based multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopy has been applied to vibrational imaging of a living fission yeast cell. We have successfully extracted only a vibrationally resonant CARS image from a characteristic spectral profile in the C-H stretching vibrational region. Using our simple but sensitive analysis, the vibrational contrast is significantly improved in comparison with a CARS imaging at a fixed Raman shift. The CARS image of a living yeast cell indicates several areas at which the signal is remarkably strong. They are considered to arise from mitochondria.

A new class of magnetic fluids: bmim[FeCl/sub 4/] and nbmim[FeCl/sub 4/] ionic liquids

The responses to a magnet of two room-temperature ionic liquids containing tetrachloroferrate(III) ions, 1-butyl-3-methylimidazolium tetrachloroferrate (bmim[FeCl/sub 4/]) and 1-butyronitrile-3-methylimidazolium tetrachloroferrate (nbmim[FeCl/sub 4/]) are compared. Although their magnetic susceptibilities are similar, the observed responses are distinct from each other, suggesting that the response is determined not only by the magnetic susceptibility but also by the other factors including density, viscosity, and surface tension. The two magnetic ionic liquids constitute a new class of magnetic fluids that hold many attractive physical properties for practical applications.

Ultrabroadband (>2500cm−1) multiplex coherent anti-Stokes Raman scattering microspectroscopy using a supercontinuum generated from a photonic crystal fiber

We have developed ultrabroadband multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopy using a coherent supercontinuum in the near-infrared region generated from a photonic crystal fiber. Owing to the ultrabroadband Stokes radiation obtained from the supercontinuum, multiple vibrational modes can be excited simultaneously in the wave-number range of more than 2500cm−1. A CARS imaging of a lipid vesicle is demonstrated with a high vibrational contrast.

Quantitative coherent anti-Stokes Raman scattering (CARS) microscopy.

The ability to observe samples qualitatively at the microscopic scale has greatly enhanced our understanding of the physical and biological world throughout the 400 year history of microscopic imaging, but there are relatively few techniques that can truly claim the ability to quantify the local concentration and composition of a sample. We review coherent anti-Stokes Raman scattering (CARS) as a quantitative, chemically specific, and label-free microscopy. We discuss the complicating influence of the nonresonant response on the CARS signal and the various experimental and mathematical approaches that can be adopted to extract quantitative information from CARS. We also review the uses to which CARS has been employed as a quantitative microscopy to solve challenges in material and biological science.

Nanosecond Time-Resolved Infrared Spectroscopy with a Dispersive Scanning Spectrometer

A nanosecond time-resolved infrared spectroscopic system based on a dispersive scanning spectrometer has been constructed. This is an advanced version of a similar system reported in a previous paper; the time resolution has been improved from 1 μs to 50 ns and the sensitivity from 10−4 in intensity changes to 10−6. These have been achieved by the use of a high-temperature ceramic infrared light source, a photovoltaic MCT detector, and a low-noise, wide-band preamplifier developed specifically for the present purpose. Time-resolved infrared spectra of a few samples of photochemical and photobiological interests are presented to show the capability of the system. The origin of the thermal artifacts, which have been found to hamper the time-resolved infrared measurements seriously, is shown to be due to the transient reflectance change induced by a small temperature jump. The future prospect of time-resolved infrared spectroscopy is discussed with reference to other methods including infrared laser spectroscopy and Fourier transform infrared spectroscopy.

Magnetic manipulation of materials in a magnetic ionic liquid

Nonmagnetic materials in a magnetic ionic liquid, which has a very large magnetic susceptibility, respond to a magnet as if they are strongly diamagnetic. The trajectory of deflected nitrogen gas bubbles in 1-butyl-3-methylimidazolium tetrachloroferrate has been measured. It shows a good agreement with theory. Nonmagnetic materials can be transported and separated in a magnetic ionic liquid, according to their density and magnetic susceptibility by regulating magnetic field and its gradient.

Quantitative CARS Molecular Fingerprinting of Single Living Cells with the Use of the Maximum Entropy Method

This work was supported by the SENTAN project (Program-S) of the Japan Science and Technology Agency (JST). H. Kano gratefully acknowledges financial support from the Precursory Research for Embryonic Science and Technology (PRESTO) program of JST. The authors thank C. Onogi for providing the spontaneous Raman spectrum of yeast mitochondria, Leukos and Horus Laser companies for technical support, and Dr. F. Omura and H. Yomo (Suntory Co., Ltd.) for providing us with the yeast sample. We gratefully acknowledge J. Ukon (HORIBA, Ltd.) for assisting in the collaboration between the Japanese and French groups.

Femtosecond coherent anti-Stokes Raman scattering spectroscopy using supercontinuum generated from a photonic crystal fiber

Femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy is demonstrated using a Ti:Sapphire oscillator and a photonic crystal fiber. A spectrally dispersed CARS signal of cyclohexane exhibits well-defined beats with a period of 430fs, which agrees well with a frequency difference between the symmetric and antisymmetric CH2-stretching vibrational modes.

Construction of a Versatile Microsecond Time-Resolved Infrared Spectrometer

A time-resolved scanning infrared spectrometer has been constructed which consists of a globar light source, a monochromator, an MCT detector, a boxcar integrator, a cw Q-switched Nd:YAG laser, and a personal computer. Both the time-resolved spectra (in the frequency-scanning mode) and the temporal change of the transient signals (in the time-scanning mode) can be observed with this spectrometer. It covers the spectral range of 700 to 4200 cm−1 with the time resolution of 1 μs. Intensity changes as small as one part in 104 can be detected with a slit width of 5 mm (6 cm−1 at 700 cm−1 and 60 cm−1 at 4000 cm−1) and with a typical scanning rate of 20 cm−1/min. High performance of this spectrometer has been achieved by the use of a high-repetition-rate (750 Hz) laser for the actinic light source combined with an ac-coupled detection scheme.