Publications by authors named "Yasutaka Suzuki"

Colloidal clay nanosheets obtained by the delamination of layered crystals of smectite-type clay minerals in water form liquid crystals because of their shape anisotropy. Loading of organic dyes onto the liquid crystalline clay nanosheets will enable novel photonic materials, where photofunctions of the loaded dye are controlled by the liquid crystallinity of the clay nanosheets. However, adsorption of organic dyes onto the nanosheets renders the nanosheet surfaces hydrophobic, and consequently, colloidal stability of the nanosheets is lost.

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Article Synopsis
  • - Inorganic nanotubes are gaining interest for their unique properties, and this study focuses on how they can be formed by scrolling nanosheets in colloidal solutions.
  • - Researchers directly observed the scrolling of niobate and clay nanosheets when organic cations were introduced, using a cationic dye for real-time visualization through color and structural changes.
  • - The study found that longer alkyl chains on the dye enhanced the scrolling process, highlighting the importance of specific interactions in nanotube formation and providing insights on choosing exfoliation reagents for nanosheet production.
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Distinguishing the luminescence contribution from the surface and bulk of a crystal is a long-standing challenge in crystal materials. Herein, three-dimensional, multiphoton, luminescence microscope imaging of the elastic molecular single crystal 1,4-bis(4-methylthien-2-yl)-2,3,5,6-tetrafluorobenzene, was conducted. Further, the luminescence contribution from the surface and bulk of the crystal was experimentally distinguished.

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A good appearance of food increases appetite. A new food product called iEat® resembles the appearance and softness of familiar foods. Previous studies have reported that iEat® foods increase appetite.

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For in vivo two-photon fluorescence microscopy (2PM) imaging, the development of techniques that can improve the observable depth and temporal resolution is an important challenge to address biological and biomedical concerns such as vascular dynamics in the deep brain (typically the hippocampal region) of living animals. Improvements have been achieved through two approaches: an optical approach using a highly tissue-penetrating excitation laser oscillating in the second near-infrared wavelength region (NIR-II, 1100-1350 nm) and a chemical approach employing fluorescent probes with high two-photon brightness (characterized by the product of the two-photon absorption cross section, σ, and the fluorescence quantum yield, Φ). To integrate these two approaches, we developed a fluorescent dye exhibiting a sufficiently high σΦ value of 68 Goeppert-Mayer units at 1100 nm.

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Formation of a desirable submillimeter-scaled assembled structure of particles in the colloid is a difficult subject in colloidal chemistry. Herein, a submillimeter-scaled ordered assembled structure consisting of highly anisotropic two-dimensional plate-like particles, niobate nanosheets, was obtained through an optical manipulation technique that was assisted by a scattering-force-induced stream. A 532 nm continuous wave laser beam with a power of 400 mW was used to illuminate a liquid crystalline niobate nanosheet colloid from the bottom side of a sample cell, inducing the stream of oriented nanosheets toward the upper side of the sample cell.

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Organic ferroelectrics, in which the constituent molecules retain remanent polarization, represent an important topic in condensed-matter science, and their attractive properties, which include lightness, flexibility, and non-toxicity, are of potential use in state-of-the-art ferroelectric devices. However, the mechanisms for the generation of ferroelectricity in such organic compounds remain limited to a few representative concepts, which has hitherto severely hampered progress in this area. Here, we demonstrate that a bowl-to-bowl inversion of a relatively small organic molecule with a bowl-shaped π-aromatic core generates ferroelectric dipole relaxation.

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Article Synopsis
  • Researchers developed new mono- and bis-BODIPY derivatives to study their structural, electrochemical, and photophysical properties, including Phena-Mono-BDP, Ant-Mono-BDP, and Ant-Bis-BDP.
  • Single-crystal X-ray analysis revealed different configurations: Ant-Mono-BDP is planar, while Phena-Mono-BDP is nonplanar, and Ant-Bis-BDP has a planar core with nonplanar ends.
  • The study found that Ant-Bis-BDP exhibits significant photophysical behavior, such as increased fluorescence quantum yield in less polar solvents and a high two-photon absorption cross-section, enhancing its potential applications.
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We report the development of a molecular ferroelectric material inspired by the hexamethylenetetramine (hmta) non-centrosymmetric molecular rotator. The bromide salt of diprotonated hmta (hmtaH ) crystalized as (hmtaH )(NH )Br in a metal-free ABX perovskite-type structure, in which the A and B sites are occupied by hmtaH and ammonium cations, respectively. The compound crystallized in the Pma2 polar space group.

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Although inorganic nanosheets prepared by exfoliation (delamination) of layered crystals have attracted great attention as 2D nanoparticles, in situ real space observations of exfoliated nanosheets in the colloidally dispersed state have not been conducted. In the present study, colloidally dispersed inorganic nanosheets prepared by exfoliation of layered niobate are directly observed with bright-field optical microscopy, which detects large nanosheets with lateral length larger than several micrometers. The observed nanosheets are not strictly flat but rounded, undulated, or folded in many cases.

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Since mitochondrial dysfunction was discovered to be the underlying cause of several severe diseases, fluorescent probes with excellent optical properties for visualising and monitoring the mitochondrial membrane potential (MMP) (a parameter of mitochondrial vitality) have been in high demand. Herein, we present novel pyrene-based dyes exhibiting remarkably large two-photon absorption around 900 nm and bright red emission around 620 nm (two-photon brightness (Φσ) = 425-525 GM), with selective localisation to the mitochondria or nucleus in response to changes in the MMP, providing several advantages over traditional MMP-monitoring probes such as Rhodamine 123 (Φσ = 64 GM). The intracellular behavior of the new dyes was investigated in detail.

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A new strategy for controlling the electron-accepting ability of an anthraquinone (AQ)-based π-molecular system is proposed to take advantage of intramolecular hydrogen bonding interactions. The electron-accepting properties of AQ are enhanced by the introduction of bulky arylsulfonamide groups into AQ derivatives due to the formation of effective intramolecular N-HO hydrogen bonding interaction and stabilization of the anion radical state even in solution.

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Article Synopsis
  • The study introduces a method to apply pseudo uniaxial pressure to organic molecules, specifically through intercalation into smectites like synthetic saponite (SSA).
  • The impact of this pseudo pressure on biphenyl derivatives is measured by examining the changes in their molecular structure, specifically the averaged dihedral angle, which indicates a corresponding pressure of approximately 0.99 GPa when loaded at 27%.
  • The technique allows for control over the applied pseudo pressure by adjusting the charge density of the smectite layers or the loading level of the biphenyl, enabling the modulation of high-pressure properties in organic molecules at standard temperature and pressure.
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A newly prepared tetraazulene-fused tetracene diimide (TA-fused TDI) showed absorption in the near-IR region owing to the effective extension of the π-conjugated system as well as a large two-photon absorption cross-section (σ =2140 GM) at 950 nm. Four reversible reduction processes and n-type semiconductivity were also confirmed as attractive electronic properties of this compound.

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Lemierre syndrome (LS) is a rare life-threatening disease that is often caused by an acute oropharyngeal infection with a secondary thrombophlebitis of the internal jugular vein. LS rarely manifests as cranial nerve palsy. To the best of our knowledge, this is the second case report of LS associated with recurrent laryngeal nerve palsy.

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Ferroelectrics are used in a wide range of applications, including memory elements, capacitors and sensors. Recently, molecular ferroelectric crystals have attracted interest as viable alternatives to conventional ceramic ferroelectrics because of their solution processability and lack of toxicity. Here we show that a class of molecular compounds-known as plastic crystals-can exhibit ferroelectricity if the constituents are judiciously chosen from polar ionic molecules.

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Polar crystals exhibiting second-order harmonic generation (SHG) were designed by adjusting the intermolecular interactions of mononuclear Cu(ii) complexes in which one H2O, two pyridines (py), and two p-substituted benzoate (p-RBA) ligands (R = F, Cl, Br, I, CH3, and OCH3) were coordinated to a Cu(ii) ion, forming a penta-coordinated asymmetric [Cu(ii)(p-RBA)2(py)2(H2O)] mononuclear structure with a permanent dipole moment along the direction of the Cu-OH2 coordination axis. Each asymmetric [Cu(ii)(p-RBA)2(py)2(H2O)] complex formed a polar one-dimensional hydrogen-bonded chain, [Cu(ii)(p-RBA)2(py)2(H2O)]∞, between the non-coordinated carboxylate oxygen atom of the p-RBA ligand and the hydrogen atom of the H2O molecule. The formation of a polar crystal depended on the arrangement of polar hydrogen-bonded chains; the parallel arrangement of each polar chain resulted in a polar crystal.

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The development of two-photon (TP) active fluorophores remains an important issue. Dyes that can be excited and fluoresce efficiently in the 'tissue optical window' (650-1100 nm) are especially in demand to maximize the underlying performance of two-photon fluorescence microscopy (TPFM) as an advanced optical technique. Ideally, such dyes would be compatible with the 1050 nm femtosecond fibre laser, which has recently been developed as an inexpensive excitation source to make the TPFM technique universal.

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Here we describe the design and synthesis of a bifunctional two-photon fluorescence probe, N,N'-‍dimethyl-4,4'-(biphenyl-2,1-ethenediyl)dipyridinium hexafluorophosphate (BP6). HeLa, Hek293, and Paramecium caudatum cells were stained with BP6. BP6 accumulated on the mitochondria of all three cell types when the mitochondrial membrane potential was high.

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Molecular structures of dicyanomethylenated quinacridone (1) as a solid and in solution were examined on the basis of single-crystal X-ray structural analysis, temperature-dependent (1)H NMR in CD2Cl2, and theoretical calculations. Crystal 1 had a curved, butterfly-shaped molecular structure. Thermally activated flipping between the curved, butterfly-shaped structure and an armchair structure occurred in solution.

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Background: Osteogenesis imperfecta (OI) is a heterogeneous group of inherited disorders that occur owing to the abnormalities in type 1 collagen, and is characterized by increased bone fragility and other extraskeletal manifestations. We report the case of a patient who was diagnosed with OI following subarachnoid hemorrhage (SAH) secondary to a ruptured saccular intracranial aneurysm (IA).

Case Presentation: A 37-year-old woman was referred to our hospital because of sudden headache and vomiting.

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Organic molecules adsorbed on an inorganic nanosheet often form a nanometer-sized cluster. In this study, we propose novel strategy for controlling the cluster size. We fabricated hybrid Langmuir-Blodgett (LB) films consisting of N-n-octadecyl-4-[2-(4-dimethylaminophenyl)ethenyl]-pyridinium bromide and a clay mineral, sodium montmorillonite, with varying subphase temperature.

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There are still few studies of low-dose recombinant tissue plasminogen activator (rtPA) therapy (0.6 mg/kg) for acute ischemic stroke (AIS) patients ≥ 80 years old, though most strokes occur in elderly people. The safety and effectiveness of this form of thrombolysis without endovascular therapy were evaluated in AIS patients ≥ 80 years old at our hospital.

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Introduction: We envisage the efficacy and safety of intra-arterial infusion of fasudil hydrochloride (IAF) for symptomatic vasospasm (SVS) after subarachnoid hemorrhage (SAH). We compared results obtained from the groups that received selective IAF (a microcatheter inserted in intracranial arteries) and nonselective IAF (a microcatheter inserted in the cervical arteries). Glasgow Outcome Scale (GOS) value and computed tomographic (CT) score were used to evaluate clinical outcome and the extent of infarction due to delayed vasospasm.

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Nonlinear optical (NLO) responses from organic dyes can be maximized when the dyes are aligned in appropriate manners in bulk materials. The use of restricted nanospaces provided by interlayer spacing of inorganic layered materials is a promising strategy for imposing suitable molecular alignments for NLO materials on dyes. The hybrid materials thus obtained exhibit salient NLO responses owing to the improved molecular orientation.

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