Kazuma Mawatari

The University of Tokyo, Tōkyō, Japan

Are you Kazuma Mawatari?

Claim your profile

Publications (129)507.27 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We aim to clarify the effects of size-confinement, solvent, and deuterium-substitution on keto-enol tautomerization of acetylacetone (AcAc) in solutions confined in 10 - 100 nm spaces (i.e., extended nanospaces) using 1H-NMR spectroscopy. The keto-enol equilibrium constants of AcAc (KEQ=[keto]/[enol]) in various solvents confined in extended nanospaces of 200 - 3,000 nm were examined using the area ratios of -CH3 peaks in keto to enol forms. The results showed that the keto form of AcAc in hydrogen-bonded solvents such as water and ethanol increased drastically with decreasing space sizes below about 500 nm, but the size-confinement didn't induce equilibrium shifts in aprotic solvents such as DMSO. The magnitudes of KEQ enhancement were well correlated with solvent proton donicity. It followed from the determination of thermodynamic parameters that the stabilization of intermolecular interactions between protons in water and carbonyl oxygen (C=O) in the keto form of AcAc were promoted by size-confinement, and that the keto form could be energetically and structurally favored in extended nanospaces vis-à-vis the bulk space. Furthermore, the measurements of deuterium-dependence of the KEQ values verified that the nanoconfinement-induced shifts of keto-enol tautomerization of AcAc are attributable to high proton mobility via a proton hopping mechanism of the confined water.
    The Journal of Physical Chemistry B 10/2015; 119(46). DOI:10.1021/acs.jpcb.5b08020 · 3.30 Impact Factor
  • Yan Xu · Kazuma Mawatari · Tomohiro Konno · Takehiko Kitamori · Kazuhiko Ishihara ·
    [Show abstract] [Hide abstract]
    ABSTRACT: Continuous culture/passage and cryopreservation are two major well-established methods to provide cultivated mammalian cells for experiments in laboratories currently. Due to the lack of flexibility, however, both laboratory-oriented methods are unable to meet the needs from rapid growing cell-based applications, which require cell supply in a variety of occasions outside of laboratories. Herein, we report spontaneous packaging and hypothermic storage of mammalian cells under a refrigerated condition (4 °C) and an ambient condition (25 °C) by using a cell-membrane-mimetic methacryloyloxyethyl phosphorylcholine (MPC) polymer hydrogel incorporated within a glass microchip. Its capability of hypothermic storage of cells was comparatively evaluated during 16 days. The results reveal that, the cytocompatible MPC polymer hydrogel in combination with the microchip structure enabled hypothermic storage of cells with quite high viability, high intracellular esterase activity, maintained cell membrane integrity, and small morphology change for more than one week at 4 °C and at least four days at 25 °C. Furthermore, the stored cells could be released from the hydrogel and exhibited ability to adhere to a surface and get to confluence under a standard cell culture condition. Both hypothermic storage conditions are ordinary flexible conditions which can be easily established in places outside of laboratories. Therefore, cell packaging and storage using the hydrogel incorporated within the microchip would be a promising miniature and portable solution for flexible supply and delivery of small amounts of cells from bench to bedside.
    ACS Applied Materials & Interfaces 10/2015; 7(41). DOI:10.1021/acsami.5b06796 · 6.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work we used reversed-phase chromatography in extended-nano channels to separate amino acids. A hydrophobic surface modification of extended-nano channels was established. A sample mixture of fluorescein and sulforhodamine B (0.5 and 0.05mM respectively) was used for the demonstration of a reversed-phase separation mode. A small amount of sample band (30fL) was injected into the separation channel, and two compounds were successfully separated. The maximum theoretical plate number of sulforhodamine B was 300,000plates/m. Two sets of 3 amino acids (3.75mM each) were separated using 0.01M citrate buffer (pH 5.5) with 0.01M sodium perchlorate and 12 and 25% of acetonitrile as a mobile phase. A successful separation (320,000plates/m with plate height of 3.2μm for serine) was accomplished.
    Journal of Chromatography A 09/2015; 1418. DOI:10.1016/j.chroma.2015.09.022 · 4.17 Impact Factor
  • Source

  • Source

  • Source

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Efficient photocatalytic water splitting requires effective generation, separation and transfer of photo-induced charge carriers that can hardly be achieved simultaneously in a single material. Here we show that the effectiveness of each process can be separately maximized in a nanostructured heterojunction with extremely thin absorber layer. We demonstrate this concept on WO3 /BiVO4 +CoPi core-shell nanostructured photoanode that achieves near theoretical water splitting efficiency. BiVO4 is characterized by a high recombination rate of photogenerated carriers that have much shorter diffusion length than the thickness required for sufficient light absorption. This issue can be resolved by the combination of BiVO4 with more conductive WO3 nanorods in a form of core-shell heterojunction, where the BiVO4 absorber layer is thinner than the carrier diffusion length while it's optical thickness is reestablished by light trapping in high aspect ratio nanostructures. Our photoanode demonstrates ultimate water splitting photocurrent of 6.72 mA cm −2 under 1 sun illumination at 1.23 V RHE that corresponds to ~90% of the theoretically possible value for BiVO4. We also demonstrate a self-biased operation of the photoanode in tandem with a double-junction GaAs/InGaAsP photovoltaic cell with stable water splitting photocurrent of 6.56 mA cm −2 that corresponds to the solar to hydrogen generation efficiency of 8.1%.
    Scientific Reports 06/2015; 5:11141. · 5.58 Impact Factor
  • Yutaka Kazoe · Kazuma Mawatari · Takehiko Kitamori ·
    [Show abstract] [Hide abstract]
    ABSTRACT: The transport and behavior of nanoparticles, viruses, and biomacromolecules in 10-1000 nm confined spaces (hereafter "extended nanospaces") is important for novel analytical devices based on nanofluidics. This study investigated the concentration and diffusion of 64-nm nanoparticles in a fused-silica nanochannel of 410 nm depth, using evanescent wave-based particle velocimetry. We found that the injection of nanoparticles into the nanochannel by pressure-driven flow was significantly inhibited and that the nanoparticle diffusion was hindered anisotropically. A 0.2-pN repulsive force induced by the interaction between the nanoparticles and the channel wall is proposed as the dominant factor governing the behavior of nanoparticles in the nanochannel, on the basis of both experimental measurements and theoretical estimations. The results of this study will greatly further our understanding of mass transfer in extended nanospaces.
    Analytical Chemistry 03/2015; 87(8). DOI:10.1021/acs.analchem.5b00485 · 5.64 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Understanding liquid structure and the electrical properties of liquids confined in extended nanospaces (10-1000 nm) is important for nanofluidics and nanochemistry. To understand these liquid properties requires determination of the dielectric constant of liquids confined in extended nanospaces. A novel dielectric constant measurement method has thus been developed for extended nanospaces using a streaming potential method. We focused on the non-steady-state streaming potential in extended nanospaces and successfully measured the dielectric constant of liquids within them without the use of probe molecules. The dielectric constant of water was determined to be significantly reduced by about 3 times compared to that of the bulk. This result contributes key information toward further understanding of the chemistry and fluidics in extended nanospaces.
    Analytical Chemistry 01/2015; 87(3). DOI:10.1021/ac504141j · 5.64 Impact Factor
  • Adelina SMIRNOVA · Hisashi SHIMIZU · Kazuma MAWATARI · Takehiko KITAMORI ·

    Analytical Sciences 01/2015; 31(11):1201-1204. DOI:10.2116/analsci.31.1201 · 1.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An extended nanospace (10—100 nm scale) makes it possible to induce unique physicochemical properties, because scientific and technological concepts in this region are shifted from the bulk condensed phase to single molecule, and from microfluidic technology to conventional nanotechnology, respectively. In this study, the molecular structure and dynamics of water and nonaqueous solvents confined in extended nanospaces on a fused-silica substrate were examined by using NMR chemical spectra, relaxation times, and so on. The results showed that the collective properties of molecular clusters with a size range from 10 to 100 nm in a liquid phase were characterized due to the effects of charged surface SiOH groups, and that unique properties differing from bulk water and surface-adsorbing water could appear in extended nanospaces. In particular, we found that (1) inhibition of molecular translational motions, (2) localization of proton charge distribution along a linear O···H-O hydrogen bonding chain, and (3) an enhancement of proton transfer of water due to the Grotthuss mechanism; (∫SiO−···H+···H2O) + H2O→∫SiO− + (H3O+ + H2O)→∫SiO− + (H2O + H3O+), were induced in extended nanospaces. Such changes appeared for sizes smaller than 800 nm. These results suggested that a proton transfer phase, in which water molecules are loosely coupled within about 50 nm from the surface, exists in extended nanospaces. This model could be qualitatively supported by a three-phase theory invoking the bulk, proton transfer, and surface-adsorbing phases.
    Bunseki kagaku 01/2015; 64(4):261-271. DOI:10.2116/bunsekikagaku.64.261 · 0.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Previously, we developed a new functional device (μELISA) by applying microfluidics and thermal-lens microscope. It has been clarified from our research that μELISA exhibits excellent performance for measuring human serum. However, when the analysis is performed for a very small amount of various patient samples in microliter order, differences in the composition or viscosity of each sample may effect the measurement values. In this research, the measurement conditions were determined for real patient serum by utilizing CRP. As a result, it has been confirmed that there is some effect that originates from some difference of each patient’s serum. To obtain reliable measured values, it is necessary to dilute each sample by a buffer.
    Bunseki kagaku 01/2015; 64(6):461-468. DOI:10.2116/bunsekikagaku.64.461 · 0.27 Impact Factor
  • Kazuma Mawatari · Takehiko Kitamori ·

    Israel Journal of Chemistry (Online) 11/2014; 54(11‐12). DOI:10.1002/ijch.201410014 · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nanostructured photoanodes based on well-separated and vertically oriented WO3 nanorods capped with extremely thin BiVO4 absorber layers are fabricated by the combination of Glancing Angle Deposition and normal physical sputtering techniques. The optimized WO3-NRs/BiVO4 photoanode modified with Co-Pi oxygen evolution co-catalyst shows remarkably stable photocurrents of 3.2 and 5.1 mA/cm2 at 1.23 V versus a reversible hydrogen electrode in a stable Na2SO4 electrolyte under simulated solar light at the standard 1 Sun and concentrated 2 Suns illumination, respectively. The photocurrent enhancement is attributed to the faster charge separation in the electronically thin BiVO4 layer and significantly reduced charge recombination. The enhanced light trapping in the nanostructured WO3-NRs/BiVO4 photoanode effectively increases the optical thickness of the BiVO4 layer and results in efficient absorption of the incident light.
    Small 09/2014; 10(18). DOI:10.1002/smll.201400276 · 8.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a novel method to analysis clenbuterol based on a competitive microfluidic immunoassay scheme with micro-ELISA system, and obtained a limit of detection that is less than 0.1 ng/ml and a quantitative working range of 0.1 ng/ml to 27.0 ng/ml. The approach was envisaged to be a promising method for efficient onsite clenbuterol control with good sensitivity and portability.
    RSC Advances 08/2014; 4(75). DOI:10.1039/C4RA05386A · 3.84 Impact Factor
  • Christopher L Cassano · Kazuma Mawatari · Takehiko Kitamori · Z Hugh Fan ·
    [Show abstract] [Hide abstract]
    ABSTRACT: The small length scales that make microfluidics attractive are also the source of some very stringent constraints, especially with respect to the detection approach used. The low concentrations often analyzed in microfluidic devices require highly sensitive detection methods that are effective even in vanishingly small sample volumes. Over the years many detection approaches have been developed for microfluidics. The majority of these methods rely upon optical phenomena, with the most common being fluorescence detection. Fluorescence detection is well suited to microfluidics because it is both flexible and sensitive, however, it does have shortcomings. Weak fluorescence of targets, autofluorescence of materials, and photobleaching are a few of the issues that have to be dealt with when working with fluorescence detection. Another option that eliminates all of these problems is thermal lens microscopy (TLM), a photothermal spectroscopy technique. TLM is a flexible, sensitive detection approach for non‐fluorescent molecules that is capable of carrying out single molecule detection to label free in vivo quantification. Despite the potential benefits of TLM, it is still an underutilized detection approach. We hope this review will help broaden the use of TLM for microchip‐based CE, as well as a host of other microfluidic applications. This article is protected by copyright. All rights reserved.
    Electrophoresis 08/2014; 35(16). DOI:10.1002/elps.201300430 · 3.03 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate a new approach to plasmonic enhanced photocatalytic water splitting by developing a novel core-shell Ti@TiO2 brush nanostructure where an elongated Ti nanorod forms a plasmonic core that concentrates light inside of a nanotubular anodic TiO2 shell. Following the ubiquitous element approach aimed at providing an enhanced device functionality without the usage of noble or rare earth elements, we utilized only inexpensive Ti to create a complex Ti@TiO2 nanostructure with an enhanced UV and Vis photocatalytic activity that emerges from the interplay between the surface plasmon resonance in the Ti core, Vis light absorption in the Ti-rich oxide layer at the Ti/TiO2 interface and UV light absorption in the nanotubular TiO2 shell.
    Nanotechnology 07/2014; 25(31):315402. DOI:10.1088/0957-4484/25/31/315402 · 3.82 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We studied photocatalytic activity of highly porous nanotubular TiO2 films modified with nanoclusters of ubiquitous metal (Ti, Al, Zn, Sn, Cu, W) oxides prepared by chemical bath deposition and atomic layer deposition as well as nanoclusters of metal rich suboxides and mixed titania suboxides prepared by atomic layer deposition by following decomposition of methylene blue under simulated solar light. The mixed titania suboxide clusters constructed on the surface of TiO2 nanotubes by atomic layer deposition demonstrated significantly enhanced photocatalytic activity in comparison to the naked TiO2 nanotubes attributed to the better absorption of visible light due to the upward shift of the valence band near the TiO2 surface induced by the suboxide clusters that feature low valence states and metal-metal bonds.
    Journal- Ceramic Society Japan 06/2014; 122(1426):393-397. DOI:10.2109/jcersj2.122.393 · 0.70 Impact Factor

  • International Conference on Modern Problems of Surface Chemistry, Kiev, Ukraine; 05/2014
  • T H H Le · K Mawatari · H Shimizu · T Kitamori ·
    [Show abstract] [Hide abstract]
    ABSTRACT: Nanofluidics in 10(1) nm space, whose scale is comparable to the electric double layer (EDL) and the size of biomolecules, promises novel functional analytical devices. However, the detection, which is indispensable to the integrated chemical system, is still challenging in such an ultra-small space. Previously, we reported a differential interference contrast thermal lens microscope (DIC-TLM) based on the photothermal interferometry principle and succeeded in detection of nonfluorescent molecules in 10(2) nm spaces. However, the thermal diffusion into substrates becomes a problem for detection in 10(1) nm spaces. The DIC-TLM signals are significantly cancelled out in spaces much smaller than the confocal length (∼10(2) nm), which makes DIC-TLM detection in 10(1) nm space quite difficult. To overcome this problem, we propose a new channel structure that benefits the thermal diffusion and sensitivity enhancement in DIC-TLM by employing TiO2 as a substrate material for compensating the signal cancellation effect. As a result, DIC-TLM detection of nonfluorescent molecules (800 molecules) was successfully demonstrated in a nanochannel with a depth of 50 nm. The developed detection method will contribute to the functional nanofluidic devices utilizing 10(1) nm spaces.
    The Analyst 04/2014; 139(11). DOI:10.1039/c4an00344f · 4.11 Impact Factor

Publication Stats

1k Citations
507.27 Total Impact Points


  • 1998-2015
    • The University of Tokyo
      • Department of Applied Chemistry
      Tōkyō, Japan
  • 2010-2014
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan
  • 2006-2010
    • Kanagawa Academy of Science and Technology
      Kawasaki Si, Kanagawa, Japan