Hiromichi Hoshina

RIKEN | RIKEN AICS · Terahertz Sensing and Imaging Research Team

Terahertz spectroscopic images of paraffin-embedded cancer tissues have been measured by a terahertz time domain spectrometer. For the systematic identification of cancer tumors, the principal component analysis and the clustering analysis were applied. In three of the four samples, the cancer tissue was recognized as an aggregate of the data point...

This paper reviews our recent spectroscopic study on poly(3-hydroxybutyrate) (PHB) for the terahertz (THz) frequency region. Clear differences are observed between the absorption spectra of crystalline and amorphous PHB, indicating that the higher order conformation of PHB determines the THz spectra. The THz polarization spectra are measured for a...

The effect of terahertz (THz) radiation on deep tissues of human body has been considered negligible due to strong absorption by water molecules. However, we observed that the energy of THz pulses transmits a millimeter thick in the aqueous solution, possibly as a shockwave, and demolishes actin filaments. Collapse of actin filament induced by THz...

Terahertz (THz) spectroscopy was used to observe adsorbed water structure and dynamics within polymer films, ultimately providing a strong rationale for the observed rates of water desorption. The THz absorption spectra of nylon-6 films undergo drastic changes during the hydration and drying process. Additionally, the structural change from γ to α...

To elucidate the mechanism by which THz radiation non-thermally affects living organisms, the lateral diffusion constants of lipid molecules in the cell membranes of HeLa cells were measured using fluorescence recovery after photobleaching under THz wave irradiation (THz-FRAP) at frequencies of 0.10, 0.29, and 0.48 THz, with power densities ranging...

Three different cocoa butter polymorphs have been determined by X-ray diffraction (XRD) and terahertz spectroscopy in the range of 0–11 THz. Specific procedures to produce different types of crystallization were detailed. The results from XRD analysis showed that the three polymorphic forms of cocoa butter were α, β′ (III), and β (V) forms. Teraher...

DNA damage, which is constantly caused by exogenous and endogenous factors, is subject to immediate repair processes; delays in these repair processes cause diseases. Here, we demonstrated that terahertz irradiation enhances the repair processes of DNA double-strand break by a non-thermal effect. The modulation of DNA damage repair by terahertz irr...

Biological phenomena induced by terahertz (THz) irradiation are described in recent reports, but underlying mechanisms, structural and dynamical change of specific molecules are still unclear. In this paper, we performed time-lapse morphological analysis of human cells and found that THz irradiation halts cell division at cytokinesis. At the end of...

Our recent experimental research on terahertz (THz) irradiation of actin filaments, which serve as representative biopolymer materials, is summarized in this review. We found that pulsed THz waves with energy density of ∼10 ⁻⁴ J cm ⁻² (∼10 ⁸ W cm ⁻² at the peak) generate acoustic waves efficiently in the aqueous media. These acoustic waves propagat...

Biological phenomena induced by terahertz (THz) irradiation are described in recent reports, but underlying mechanisms, structural and dynamical change of specific molecules are still unclear. In this paper, we performed time-lapse morphological analysis of human cells and found that THz irradiation halts cell division at cytokinesis. At the end of...

During transcription in cells, the transcription complex consisting of RNA polymerase, DNA, and nascent RNA is exposed to fluctuating temperature and pressure. However, little is known about the mechanism of transcriptional homeostasis under fluctuating physical parameters. In this study, we generated these fluctuating parameters using pulsed local...

We demonstrate photoacoustic wave propagation with a plane wavefront in liquid water using a terahertz (THz) laser pulse. The THz light can effectively generate the photoacoustic wave in water because of strong absorption via a stretching vibration mode of the hydrogen bonding network. The excitation of a large-area water surface irradiated by loos...

Terahertz (THz) absorption spectra of cross-linked polyurethane films were observed at 30–180 °C. The obtained spectra displayed characteristic absorption bands. A band observed at 2.6 THz was assigned to the C=O···N-H hydrogen bond vibration using previously reported data. DFT calculation results confirmed that a band at 7.5 THz arises owing to th...

The Investigating R&D Committee on Nondestructive Testing by Terahertz Waves was established in April 2015 under the IEEJ Technical Committee on Instrumentation and Measurement. The aim of the committee was to survey the following items: the latest apparatus to generate and detect THz waves, THz wave application to non-destructive testing, and extr...

An intensive analysis of far-infrared (far-IR), low-frequency Raman, and wide angle X-ray diffraction (WAXD) data has been performed by two-dimensional correlation spectroscopy (2D-COS) as a function of the blend ratio of poly(3-hydroxybutyrate)/poly(4-vinylphenol) (PHB/PVPh). Homospectral 2D-COS revealed that a weak band at 128 cm-1 in the far-IR...

The effect of terahertz (THz) radiation on deep tissues of human body has been considered negligible due to strong absorption by water molecules. However, we observed that the energy of THz pulses transmits a millimeter thick in the aqueous solution, possibly as a shockwave, and demolishes actin filaments. Collapse of actin filament induced by THz...

We demonstrate shockwave propagation with a plane wave front in liquid water using terahertz (THz) laser pulses. The THz light effectively generates shockwaves in water due to strong absorption via stretching vibration of hydrogen bonding network. This produces a plane shockwave from large area excitation of the water surface with small THz irradia...

p>Terahertz (THz) spectroscopy was used to observe adsorbed water structure and dynamics within polymer films, ultimately providing a strong rationale for the observed rates of water desorption. The THz absorption spectra of nylon-6 films undergoes drastic changes during the hydration and drying process. Additionally, the structural change from g t...

Far-infrared (FIR) and low-frequency Raman bands in the 90-400 cm-1 region of crystalline nylon 6 in α form were assigned based on comparisons of experimental spectra and quantum mechanical calculations. A fragment methodology was applied in the calculations for explicit consideration of interchain interactions and crystal symmetry. The main featur...

Isothermal crystallization of poly(glycolic acid) (PGA) was carried out using terahertz (THz) and infrared (IR) spectroscopy and simultaneous small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) measurements. The intensity of the absorption peak at 192 cm−1 increased before the increase in intensity of the peak at 65 cm−1 during...

Polymerization of monomeric actin into filaments has pivotal roles in cell motility, growth, differentiation, and gene expression. Therefore, techniques of manipulating actin polymerization, including actin-binding chemicals, have been developed for understanding and regulating multiple biological functions. Here, we demonstrate that irradiation wi...

Poly (ethylene-vinylalcohol) copolymer (EVOH) films under different humidity conditions were studied by THz absorption spectroscopy to obtain information about the bound water. An intermolecular stretching mode of bound water was observed at around 6 THz, similar to that in liquid water; and the very weak libration mode indicates that this water is...

The long range structure of poly(ε-caprolactone) (PCL) has been studied by terahertz (THz) spectroscopy, infrared (IR) spectroscopy and quantum chemical calculations (QCCs). Natural bond orbital (NBO) analysis and the calculation of the interatomic distances between C-H and O=C groups in PCL crystalline indicate that the PCL chain has three kinds o...

Composition-, temperature-, and polarization-dependent low-frequency Raman and terahertz (far-infrared; FIR) spectra were measured for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(HB-co-HV)) with PHB-type crystal structure and PHV-type crystal structure to investigate their intermolecular interactions. Band assignments were attempted by comparin...

The distribution of crystallinity and the crystalline orientation of a poly(ɛ-caprolactone) (PCL) film have been studied using terahertz (THz) imaging. Terahertz images were developed by using the intensity ratio of the two spectral peaks at 1.42 and 2.03 THz that are assigned to the crystalline modes parallel and perpendicular to the c-axis (I⊥/I...

Low-frequency vibrational modes of lamellar crystalline poly(glycolic acid) (PGA) were measured on Raman and far-infrared (FIR) spectra. Among the observed bands, an FIR band at ∼70 cm–1 and a Raman band at 125 cm–1 showed a gradual lower-frequency shift with increasing temperature from 20 °C to the melting point at ∼230 °C. Their polarization dire...

In this presentation, we succeed in altering polymer morphology using terahertz (THz) wave irradiation. Pulsed THz waves generated by a free electron laser (FEL) were irradiated to a poly(3-hydroxybutylate) (PHB) / chloroform solution during solvent casting crystallization. Morphological observation shows the formation of micrometer-sized crystals...

In this work, we report on the infrared spectroscopic study of clusters of CH4 molecules with up to N = 80 para-hydrogen molecules which have been assembled inside He droplets.Upon increase of the number of the added para-hydrogen molecules up to about N = 12, both the rotational constant, B, and the origin frequency of the υ3 band of CH4 decrease...

As terahertz (THz) frequencies correspond to those of the intermolecular vibrational modes in a polymer, intense THz wave irradiation affects the macromolecular polymorph, which determines the polymer properties and functions. THz photon energy is quite low compared to the covalent bond energy; therefore, conformational changes can be induced “soft...

A stilbazolium material comprising 4-dimethylamino-N′-methyl-4′-stilbazolium tosylate (DAST), which has a large nonlinear optical susceptibility, was studied for application in terahertz (THz)-wave generation. The temperature-dependent structure of the DAST crystal was measured by using powder X-ray diffraction from −100 to 200 °C, indicating a vol...

Nitrogen oxide clusters (NO)n have been studied in He droplets via infrared depletion spectroscopy and by quantum chemical calculations. The ν1 and ν5 bands of cis-ON-NO dimer have been observed at 1868.2 and 1786.5 cm(-1), respectively. Spectral bands of the trimer and tetramer have furthermore been located in the vicinity of the corresponding dim...

Methane is one of the very few substances that show rotation of individual molecules in the crystalline phase. Here we explore the evolution of the rotation spectrum of methane from single molecules to clusters containing up to about 4 × 10(3) molecules. The clusters were assembled in He droplets at T = 0.38 K and studied via infrared laser spectro...

Terahertz (THz) waves radiated from two noncollinear femtosecond plasma filaments with a crossing angle of 25° are investigated. The irradiated THz waves from the crossing filaments show a small THz pulse after the main THz pulse, which was not observed in those from single-filament scheme. Since the position of the small THz pulse changes with the...

In this study, we investigate THz pulses generated from optical rectification with tilted-pulse-front pumping scheme in which the laser beam is focused to a line in a stoichiometric lithium niobate (sLN) crystal. A cylindrical lens and a common lens are used to focus the pump laser beam to a line. The power law of THz pulse generation and the redsh...

This work reports on the study of the internal rotation of methane molecules in small clusters containing up to about five molecules. The clusters were assembled in helium droplets at T = 0.38 K by successive capture of single methane molecules and studied by infrared laser spectroscopy of the fundamental CH4 ν3 vibration around 3030 cm−1. The spec...

The α and γ crystals of polyamide-6 were examined by terahertz absorption spectroscopy from −90 to 230 °C. For the α crystals, the absorption band at 6.5 THz, assigned as a lattice vibration perpendicular to the molecular chain, decreased in intensity with increasing temperature, ending near the Brill transition temperature (TBrill ≈ 160 °C). The b...

In this review, the potential of terahertz spectroscopy as a new tool for the study of soft materials is discussed. We have succeeded in developing a method for the assignment of low-frequency vibrational modes of polymers and obtained information about their higher-order conformations. By the temperature dependent THz spectra of the polymers, the...

In this paper, potential of terahertz（THz）imaging and spectroscopy for monitoring frozen bio-materials has been demonstrated by using THz time domain spectroscopy. Frozen poke meat shows clear difference between muscle and fat in its refractive indices. Image of frozen salmon meat clearly shows a bone inside. The origin of the absorbance of frozen...

The phase behaviors and kinetics of the polymorphic transitions of cyclohexanol, C6H11OH, were investigated by terahertz absorption spectroscopy over the temperature range of 150-330 K. A new phase was found, labeled phase I', which is more stable than the previously observed phase I but less stable than phase III'. The kinetics of the irreversible...

In this study, the terahertz (THz) absorption spectra of poly(3-hydroxybutyrate) (PHB) were measured during isothermal crystallization at 90-120 degrees C. The temporal changes in the absorption spectra were analyzed using two-dimensional correlation spectroscopy (2DCOS). In the asynchronous plot, cross peaks were observed around 2.4 THz, suggestin...

Terahertz (THz) absorption spectra of organogels consisting of (1R,2R)-1,2-bis(dodecanoylamino) cyclohexane/2-nitrophenyl octyl ether (RR-BDC/NPOE) and RR-BDC/n-dodecane were measured by Fourier-transform far-infrared (FT-FIR) spectroscopy. The vibrational peaks of the gels were observed at the same frequencies as those of the pure gelator, suggest...

Ethane and ethane clusters (N ~ 10(3)-10(4)) were studied inside He droplets with infrared laser spectroscopy. The spectra were measured in the 2880-3000 cm(-1) range, which covers the ν5, ν8+11, and ν7 vibrational bands of ethane. Partially resolved rotational fine structure in the spectrum of the monomer reveals solvent-induced band origin blue s...

Terahertz (THz) absorption spectra of supramolecular gels ((1R,2R)-1,2-bis(dodecanoylamino)cyclohexane/2-nitrophenyl octyl ether) were measured by Fourier transform far-infrared spectroscopy (FT-FIR). The spectra were measured by changing concentration and temperature of gels. The absorption intensities of the peaks around 8.6 THz show drastic chan...

Terahertz absorption spectra of poly(3-hydroxybutylate) (PHB) and nylon were measured by a terahertz time domain spectrometer and a Fourier transform far-infrared spectrometer. Clear differences were observed between the spectra of crystalline and amorphous PHB, indicating that the absorption peaks observed in the THz spectra originated in the high...

Low-frequency vibrational bands observed in Raman and THz spectra in the region of 50-150 cm(-1) of crystalline powder poly-(R)-3-hydroxybutyrate (PHB) were assigned based on comparisons of the Raman and THz spectra, polarization directions of THz absorption spectra, and their congruities to quantum-mechanically (QM) calculated spectra. This combin...

Terahertz absorption spectra were measured for nylon-6/6, nylon-6, nylon-11 and nylon-12 by Fourier transform far-infrared spectroscopy. Different spectral features among the four species were interpreted as the characteristics of crystalline conformations of nylons.

The terahertz attenuated total reflectance spectra of Poly(N-isopropylacrylamide) (P-NIPAAm) solutions were measured in the range of 26.5–47.3 °C. The phase-change in P-NIPAAm was observed via the temperature dependence of the spectra. The collapse of hydrogen bonds in solution was confirmed by the decrease in the signal intensities around 62 cm−1,...

The isothermal crystallization of poly(3-hydroxybutylate) (PHB) was studied by monitoring the temporal evolution of terahertz absorption spectra in conjunction with spectral analysis using two-dimensional correlation spectroscopy. Correlation between the absorption peaks and the sequential order of the changes in spectral intensity extracted from s...

Terahertz (THz) absorption spectra of poly(3-hydroxyalkanotes) (PHA) were measured by a terahertz timedomain spectrometer and Fourier transform far-infrared spectrometer. Clear differences were observed between the spectra of crystalline and amorphous PHA, indicating that the absorption peaks observed in the THz spectra originated in the higher-ord...

Isothermal crystallization of poly(3-hydroxy-butyrate) was studied by terahertz time-domain spectroscopy. The temporal change of the ratio between the crystalline and amorphous structure was estimated by the integrated absorption intensity. The crystallization process was discussed by using Avrmi's equation.

The ν3 and ν4 vibrational transitions of CH3 and CD3 isolated in solid parahydrogen were studied by high-resolution infrared spectroscopy. The radicals were produced by in situ UV photolysis of methyl iodides trapped in solid parahydrogen. The observed spectra showed clear rotational fine structures, which were subjected to further splitting due to...

Temperature-dependent terahertz (THz) absorption spectra of poly(3-hydroxyalkanoate)s (PHAs) were measured by using a Fourier transform far-infrared (FT-FIR) spectrometer and a THz time-domain spectrometer over a temperature range of 10 K to 465 K with a liquid helium cryostat and a heating cell. Clear differences were observed between the spectra...

The aim of this study was to apply terahertz (THz) technology to security applications, and in particular, for screening and identification of drugs-of-abuse in mail. Comparison was made of transmission spectra obtained with both THz time-domain spectroscopy and a tunable THz source, and the effects of sample configuration on the resulting spectra...

Terahertz absorption spectra of poly(3-hydroxyalkanoates) with different conformations were measured by using a terahertz time domain spectrometer. Sharp absorption peaks were observed in the spectrum of crystalline samples. The orientation direction of the transition dipole moment was investigated by the polarization spectra. The peak at 2.92 THz...

Terahertz transmission spectra of frozen gelatin solution were measured. The observed spectrum shows that the scattering of ice crystal is negligibly small. The absorbance of liquid water in the sample was confirmed by subtracting those of ice and freeze dried gelatin from the observed spectra.

The infrared spectra of ethane molecules embedded in He droplets have been studied via depletion spectroscopy in the $\nu$ = 2880-3000 cm$^{-1}$ spectral range. Four features observed in the spectra are assigned as the $\nu$$_{5}$, $\nu$$_{8+11}$(perpendicular and parallel components), and $\nu$$_{7}$ vibrational bands. Band origins and rotational...

This work studies the renormalization of the molecular moments of inertia I(G) in liquid helium. For this purpose we have measured the rotational-vibrational spectra of the nu(3) modes of a series of homologous light spherical top molecules such as CH(4), CD(4), SiH(4), and SiD(4) in He droplets. The spectra were fitted to an empirical gas phase Ha...

Carbon dioxide (CO2) induced pressure broadening coefficients of water vapor (H2O) lines have been determined using a terahertz time-domain spectrometer (TDS). Thirty-two rotational transitions of H2O were observed in the spectral range of 18– (550–3050 GHz) for the first time. Using TDS allows one to measure absorption spectra with one order of ma...

Recently, terahertz wave imaging has been shown to have potential in medical and biological applications. However, absorption by liquid water in tissues hinders the measurement of thick samples. In this study, porcine tissue was frozen to temperatures below -33 °C to prevent this absorption. Consequently, the striated muscle and adipose tissue coul...

Using the high penetrability of the terahertz waves and the characteristic absorption spectra in this frequency range, we have built a noninvasive mail inspection system targeting drugs and explosives. The system is composed of two stages; in the first stage, the scattering of a continuous terahertz wave is used for selecting mail that contains con...

The ortho-to-para nuclear spin ratio of cyclopropenylidene (cyclic C3H2) in TMC-1 cores was investigated using the 45 m radio telescope at Nobeyama Radio Observatory. We have observed four ortho lines (J = 212-101, 312-303, 321-312, and 330-321) and four para lines (J = 202-111, 211-202, 220-211, and 322-313) of cyclic C3H2 in six cores in TMC-1. A...

The pressure broadening parameters γN2 and γO2of pure rotational transitions of water vapor with nitrogen and oxygen as foreign gases, respectively, were measured with a terahertz time-domain spectrometer (THz-TDS) in the frequency region from 0.5 to 3.5 THz. A White-type multi-pass cell was introduced in the THz-TDS system to precisely measure the...

The air induced broadening coefficients of the pure rotational transitions of H22O at 556.936 GHz (110←101)(110←101), and 752.033 GHz (211←202)(211←202) were measured by terahertz time-domain spectroscopy. The air broadening coefficient was determined to be 4.012(30)MHzTorr-1 for the 556.936 GHz line and 3.964(40)MHzTorr-1 for the 752.033 GHz line,...