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Hiro-o Hamaguchi

Publications and source records attributed to Hiro-o Hamaguchi.

9 recordsLinked to original sources
PubMed2006

Charge resonance character in the charge transfer state of bianthryls: effect of symmetry breaking on time-resolved near-IR absorption spectra.

We study the effects of symmetry breaking on the photogenerated intramolecular charge transfer (CT) state of 9,9'-bianthryl (BA) with femtosecond time-resolved near-IR spectroscopy. The time-resolved near-IR spectra are measured in acetonitrile for a symmetric substituted derivative of 10,10'-dicyano-9,9'-bianthryl (DCBA) and asymmetric substituted derivatives of 10-cyano-9,9'-bianthryl (CBA) and 9-(N-carbazolyl)anthracene (C9A), as well as nonsubstituted BA. The transient near-IR absorption spectrum of each compound at 0 ps has a locally excited (LE) absorption band, which agrees with the transient absorption band of the corresponding monomer unit. At 3 ps after the photoexcitation, the symmetric compounds show a broad charge transfer (CT) absorption band, whereas no absorption peak appears in the spectra of the asymmetric compounds. The broad CT absorption at 1250 nm only observed for the symmetric compounds can be attributed to the charge resonance transition associated with two equivalent charge separated states.

Journal Article↗
PubMed2006

Three-dimensional vibrational imaging of a microcrystalline J-aggregate using supercontinuum-based ultra-broadband multiplex coherent anti-stokes Raman scattering microscopy.

Vibrational properties of a porphyrin J-aggregate microcrystal have been investigated by ultra-broadband multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopy using a supercontinuum light source generated from a photonic crystal fiber. Owing to a strong resonance effect due to an excitonic transition, clear spectral and spatial profiles of the CARS signal have been successfully obtained. On the basis of the comparison between the CARS and the fluorescence images, the spatial dependence of the CARS signal can be explained by the spatial inhomogeneity of the excitonic transition energy in the single J-aggregate microcrystal.

Journal Article↗
PubMed2006

Effect of water on the molecular structure and arrangement of nitrile-functionalized ionic liquids.

Water changes the physical properties of ionic liquids (ILs). In this paper, the effect of water on ILs is investigated at the molecular level. The molecular structure and arrangement of 1-butyronitrile-3-methylimidazolium halide, in the presence and absence of the intruded water molecule, have been elucidated by single-crystal X-ray crystallography and near-infrared Raman spectroscopy. Water molecule is found to change the conformation of the n-butyronitrile chain of the cation. The hydrogen bonding interaction between the anion and water molecule, leading to loose molecular packing, is most likely to be responsible for the change. Distinct molecular structures and arrangements of ILs with and without water molecule have been presented here for the first time. As the unique properties of ILs are related to their structures and molecular arrangements, the presence of water, wanted or unwanted, must be carefully examined in any kind of IL research and applications.

Crystallography, X-Ray↗
PubMed2006

Hyper-Raman microspectroscopy: a new approach to completing vibrational spectral and imaging information under a microscope.

We have developed hyper-Raman scattering microspectroscopy and applied it to a microcrystal of all-trans-beta-carotene. The hyper-Raman spectrum of all-trans-beta-carotene exhibits a Raman-inactive but infrared-active vibrational mode at 1564 cm(-1). Hyper-Raman imaging of a microcrystal was performed with this band. Infrared-active vibrational imaging was achieved with a spatial resolution much higher than that of conventional infrared microscopy. The combination of Raman and hyper-Raman spectroscopy opens up a new scope for high-spatial-resolution vibrational microspectroscopy that is not restricted by the selection rule.

Crystallography↗
PubMed2005

Molecular-level investigation of the structure, transformation, and bioactivity of single living fission yeast cells by time- and space-resolved Raman spectroscopy.

The structure, transformation, and bioactivity of single living Schizosaccharomyces pombe cells at the molecular level have been studied in vivo by time- and space-resolved Raman spectroscopy. A time resolution of 100 s and a space resolution of 250 nm have been achieved with the use of a confocal Raman microspectrometer. The space-resolved Raman spectra of living S. pombe cells at different cell cycle stages were recorded in an effort to elucidate the molecular compositions of organelles, including nuclei, cytoplasm, mitochondria, and septa. The time- and space-resolved measurement of the central part of a dividing yeast cell showed continuous spectral evolution from that of the nucleus to those of the cytoplasm and mitochondria and finally to that of the septum, in accordance with the transformation during the cell cycle. A strong Raman band was observed at 1602 cm(-)(1) only when cells were under good nutrient conditions. The effect of a respiration inhibitor, KCN, on a living yeast cell was studied by measuring the Raman spectra of its mitochondria. A sudden disappearance of the 1602 cm(-)(1) band followed by the change in the shape and intensity of the phospholipid bands was observed, indicating a strong relationship between the cell activity and the intensity of this band. We therefore call this band "the Raman spectroscopic signature of life". The Raman mapping of a living yeast cell was also carried out. Not only the distributions of molecular species but also those of active mitochondria in the cell were successfully visualized in vivo.

Cell Cycle↗
PubMed2005

Ion association dynamics in aqueous solutions of sulfate salts as studied by Raman band shape analysis.

A new perspective is shown on the interaction between the sulfate ion and its counter cation in aqueous solutions. We propose the dynamic exchange model of ion association instead of the conventional static equilibrium model. The concentration dependence of the Raman band shape of the totally symmetric (a(1)) SO stretch mode of the sulfate ion is investigated systematically for four sulfate ions, MgSO(4), (NH(4))(2)SO(4), K(2)SO(4), and Li(2)SO(4). The concentration dependence of the a(1) Raman band shape in the MgSO(4) system is successfully reproduced by the analysis based on the dynamic exchange model. As a result, quantitative information about the extremely dynamic nature of the ion association has been obtained: the mean time between associations is a few picoseconds and the mean lifetime of association is several hundred femtoseconds.

Journal Article↗
PubMed2003

Characterization of a supercontinuum generated from a photonic crystal fiber and its application to coherent Raman spectroscopy.

The temporal and spectral profiles of supercontinuum radiation generated from a photonic crystal fiber are evaluated with a polarization-gate frequency-resolved optical gating technique. The supercontinuum is then applied to coherent inverse Raman spectroscopy. A stimulated Raman signal of cyclohexane is observed as an induced absorption signal with an instantaneous response. The Raman signal has a peak at a slight negative delay time, which is explained by perturbed Raman-induced coherence.

Journal Article↗
PubMedDate not supplied

The diagnosis of lung cancer using 1064-nm excited near-infrared multichannel Raman spectroscopy.

PURPOSE: Raman spectroscopy is based on Raman scattering of light from molecules. Because the wavelength of Raman scattered light depends on molecular composition, Raman spectra provide highly useful information about molecular composition. It has already been shown that Raman spectroscopy is potentially useful for the clinical diagnosis of malignant tumors. However, this technique had never been applied to the diagnosis of lung cancers, primarily because of interference from the strong fluorescence emitted from lung tissues. Our purpose was to examine the effectiveness of near-infrared Raman spectroscopy for the diagnosis of lung cancers. METHODS: We constructed a new near-infrared multichannel Raman system that is capable of measuring high signal-to-noise ratio, fluorescence-free Raman spectra of lung tissues within a measurement time of 1 second. Using this system, we collected a total of 210 Raman spectra from cancerous and non-cancerous lung tissues and analyzed these spectra by a least-squares fitting procedure for cancer diagnosis. RESULTS: The resultant sensitivity of cancer prediction was as high as 91%, with 97% specificity and an error margin of p<0.0001 according to Fisher's exact test. CONCLUSIONS: A method of diagnosing lung cancer efficiently and objectively using Raman spectroscopy has thus been established.

Adenocarcinoma↗