Kazufumi Kobashi

National Institute of Advanced Industrial Science and Technology

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Toshiya Okazaki

National Institute of Advanced Industrial Science and Technology

Takeo Yamada

National Institute of Advanced Industrial Science and Technology

Kenji Hata

National Institute of Advanced Industrial Science and Technology

Don N. Futaba

National Institute of Advanced Industrial Science and Technology

Shun Muroga

National Institute of Advanced Industrial Science and Technology

Takahiro Morimoto

National Institute of Advanced Industrial Science and Technology

A. Sekiguchi

National Institute of Advanced Industrial Science and Technology

H. Nakajima

National Institute of Advanced Industrial Science and Technology

Karolina Laszczyk

Wrocław University of Science and Technology

Yuichi Kato

National Institute of Advanced Industrial Science and Technology

Cooperative Institutions

National Institute of Advanced Industrial Science and Technology

Okayama University

The University of Tokyo

University of Tsukuba

Photonics Electronics Technology Research Association

Tohoku University

Japan Science and Technology Agency

Kyoto University

Osaka University

Nagoya University

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

A Microwave-Assisted, Solvent-Free Approach for the Versatile Functionalization of Carbon Nanotubes

ACS Nano (2023)

Dewu Lin Don N. Futaba Kazufumi Kobashi Minfang Zhang Shun Muroga

While the functionalization of carbon nanotubes (CNTs) has attracted extensive interest for a wide range of applications, a facial and versatile strategy remains in demand. Here, we report a microwave-assisted, solvent-free approach to directly functionalize CNTs both in raw form and in arbitrary macroscopic assemblies. Rapid microwave irradiation was applied to generate active sites on the CNTs while not inducing excessive damage to the graphitic network, and a gas-phase deposition afforded controllable grafting for thorough or regioselective functionalization. Using methyl methacrylate (MMA) as a model functional group and a CNT sponge as a model assembly, homogeneous grafting was exhibited by the increased robust hydrophobicity (contact angle increase from 30 to 140°) and improved structural stability (compressive modulus increased by 135%). Therefore, when our MMA-functionalized CNTs served as a solar absorber for saline distillation, high operating stability with a superior water evaporation rate of ∼2.6 kg m-2 h-1 was observed. Finally, to highlight the efficacy and versatility of this functionalization approach, we fabricated asymmetrically hydrophobic CNT sponges by regioselective functionalization to serve as a moisture-driven generator, which demonstrated a stable open-circuit voltage of 0.6 mV. This versatile, solvent-free approach can complement conventional solution-based techniques in the design and fabrication of multifunctional nanocarbon-based materials.

Surface Modification

10.1021/acsnano.2c12789

Cite

Citations (8)

Sub-millimeter arbitrary arrangements of monolithically micro-scale electrical double layer capacitors

Journal of Physics Conference Series (2015)

Karolina Laszczyk Kazufumi Kobashi Shunsuke Sakurai A. Sekiguchi Don N. Futaba

We report the investigation on the reproducibility of micro-scale electric double layer capacitors (micro-EDLCs). The micro-EDLC components were fabricated parallel using photolithography, wet and dry processing. Electrodes of the micro-EDLCs are highly dense packed Single Wall Carbon Nanotubes (SWCNTs) that form a mesh structure. The micro- EDLCs are connected 1-10 in series and in parallel being unified electrical circuits to tune the capacitance and the operational voltage. To confirm the reproducibility of the cells as well as the yield we performed electrochemical measurements in order to define the performance uniformity between cells strings and individual cells connected in a string. For 1-10 cells in series and in parallel the trends for the capacitance and operational voltage satisfied electrophysics rules governing cells addition. However, the measurements of the individual cells in a string revealed the significant performance discrepancy that might result in a shorten life cycling of a circuit.

Electric double-layer capacitor

10.1088/1742-6596/660/1/012086

Cite

Citations (0)

Dual Self‐Assembling Polycondensation of p‐Acetoxybenzoic Acid and p‐Acetamidobenzoic Acid

Macromolecular Rapid Communications (2003)

Kunio Kimura Kazufumi Kobashi Hitoshi Maeda Yuhiko Yamashita

Abstract The dual self‐assembling polycondensation of p ‐acetoxybenzoic acid (ABA) and p ‐acetamidobenzoic acid in Therm S 800 was examined at 300 °C. Needle‐like crystals and lath‐like crystals were formed simultaneously through reaction‐induced crystallization of oligomers at a molar ratio of 30–50 mol‐% ABA in the feed. The needle‐like crystals comprised more p ‐oxybenzoyl units, whereas the lath‐like ones contained higher amounts of p ‐benzamide moieties. magnified image

Molar ratio

Benzamide

Lath

10.1002/marc.200390032

Cite

Citations (3)

Involvement of apoptosis in activation-induced cell death of bacteria-reactive human CD45RO+ T cells.

PubMed (1999)

M Kodera H Iwagaki Yasuhiro Morimoto Kazufumi Kobashi A Hizuta

Although the identity of the T cells that protect against bacteria in humans remains unknown, it is clear that patients with bacterial infection have reduced numbers of T cells in their blood. Here we have determined whether this T cell loss is a consequence of bacterial antigen-mediated activation-induced cell death (AICD). By flowcytometric analysis, less than 0.3% of freshly isolated T cells from healthy volunteers and patients with severe pneumonia were identified as apoptotic. However, during culture the rate of apoptosis in peripheral blood T cells from patients was 3.0 +/- 0.9%; and increased further in the presence of anti-CD3 (7.4 +/- 2.1%) and decreased when IL-2 was added (4.4 +/- 1.3%). In contrast, no changes were observed in healthy volunteers on addition of anti-CD3. Further, anti-CD3 significantly increased the susceptibility to apoptosis of CD45RO+ T cells, but not CD45RA+ T cells from patients, and the percentage of CD45RO+ T cells in patients was significantly higher than that in healthy volunteers. Flowcytometric analysis revealed the expression level of Fas to be higher in the patients than healthy volunteers. Collectively, these findings demonstrated that bacteria-reactive T cells were more susceptible to AICD and that Fas-FasL pathways of apoptosis were involved. AICD of CD45RO+ T cells, therefore, provides an explanation for the loss of bacteria-reactive T cells during bacterial infection.

Fas ligand

Source

Cite

Citations (3)

Indentation behavior of suspended single-walled carbon nanotube films

Carbon Trends (2021)

Yuichi Kato A. Sekiguchi Kazufumi Kobashi Y. Ono Takeo Yamada

Suspended thin film carbon nanotubes with suitable mechanical strength are in high demand for applications such as sensors, particle filters, or thermoacoustic speakers. However, researchers working on the production and development of applications for thin films have found difficulty in evaluating their mechanical strength. This research shows the nano-indentation behavior of thin (<26 nm thickness) single-walled carbon nanotube suspended films, to evaluate their mechanical strength. Indentation tests, scanning electron microscopy, and Raman, infrared, reflection spectroscopy showed that the high crystallinity of carbon nanotubes and film thickness uniformity are important for achieving high mechanical strength.

Indentation

Reflection

10.1016/j.cartre.2021.100112

Cite

Citations (5)

One hundred fold increase in current carrying capacity in a carbon nanotube–copper composite

Nature Communications (2013)

Chandramouli Subramaniam Takeo Yamada Kazufumi Kobashi A. Sekiguchi Don N. Futaba

Increased portability, versatility and ubiquity of electronics devices are a result of their progressive miniaturization, requiring current flow through narrow channels. Present-day devices operate close to the maximum current-carrying-capacity (that is, ampacity) of conductors (such as copper and gold), leading to decreased lifetime and performance, creating demand for new conductors with higher ampacity. Ampacity represents the maximum current-carrying capacity of the object that depends both on the structure and material. Here we report a carbon nanotube-copper composite exhibiting similar conductivity (2.3-4.7 × 10(5) S cm(-1)) as copper (5.8 × 10(5) S cm(-1)), but with a 100-times higher ampacity (6 × 10(8) A cm(-2)). Vacuum experiments demonstrate that carbon nanotubes suppress the primary failure pathways in copper as observed by the increased copper diffusion activation energy (~2.0 eV) in carbon nanotube-copper composite, explaining its higher ampacity. This is the only material with both high conductivity and high ampacity, making it uniquely suited for applications in microscale electronics and inverters.

Ampacity

Microscale chemistry

10.1038/ncomms3202

Cite

Citations (482)

Liquid sensing of melt-processed poly(lactic acid)/multi-walled carbon nanotube composite films

Sensors and Actuators B Chemical (2008)

Kazufumi Kobashi Tobias Villmow T Aguayo Andres Petra Pötschke

Tetrahydrofuran

Hildebrand solubility parameter

10.1016/j.snb.2008.06.035

Cite

Citations (100)

Sublimable Surfactant for Carbon Nanotube Dispersion: Study on a Flavin Compound

Chemistry Letters (2020)

Yuichi Kato Kazufumi Kobashi Takeo Yamada Kenji Hata

We describe the sublimation property of a flavin molecule as a solution to the surfactant residue problem of single-walled carbon nanotubes. Thermogravimetric analysis, UV-vis spectroscopy, and NMR indicate our flavin has sublimability. The saturated vapor pressure of the flavin was calculated to be 0.08 Pa at 250 °C. Careful vacuum and temperature control or further modification of the molecular structure is necessary to avoid competing thermal reactions. We describe the sublimation property of a flavin molecule which is known as a surfactant for chirality-sorting of single-walled carbon nanotubes as a solution to the surfactant residue problem. Thermogravimetric analysis in vacuum indicate the flavin has a sublimability.

Thermogravimetric analysis

Sublimation

10.1246/cl.190807

Cite

Citations (2)

Torsion-Sensing Material from Aligned Carbon Nanotubes Wound onto a Rod Demonstrating Wide Dynamic Range

ACS Nano (2013)

Takeo Yamada Yuki Yamamoto Yuhei Hayamizu A. Sekiguchi Hiroyuki Tanaka

A rational torsion sensing material was fabricated by wrapping aligned single-walled carbon nanotube (SWCNT) thin films onto the surface of a rod with a predetermined and fixed wrapping angle without destroying the internal network of the SWCNTs within the film. When applied as a torsion sensor, torsion could be measured up to 400 rad/meter, that is, more than 4 times higher than conventional optical fiber torsion sensors, by monitoring increases in resistance due to fracturing of the aligned SWCNT thin films.

10.1021/nn305593k

Cite

Citations (19)

Nonuniform functional group distribution of carbon nanotubes studied by energy dispersive X-ray spectrometry imaging in SEM

Nanoscale (2019)

H. Nakajima Takahiro Morimoto Ying Zhou Kazufumi Kobashi Seisuke Ata

Functionalization is a key technique to improving the dispersibility of carbon nanotubes (CNTs) in solvents and polymer matrices for producing versatile CNT-based materials. Therefore, a robust and efficient characterization method is required to confirm that the functionalization on the CNT surface is spatially uniform. Although several imaging techniques for transmission electron microscopes can characterize the spatial localization of elements chemically bound to an isolated CNT surface, they are unsuitable for examinations on a practical scale because of their limited scanning area. Here, we present high spatially resolved energy dispersive X-ray spectrometry (EDS) imaging of functionalized single-walled CNTs (SWCNTs) in scanning electron microscopy (SEM). Highly sensitive EDS detection and drift-free operation enables our technique to image the light elements of SWCNTs with sufficient spatial resolution (<10 nm). We describe an experimental visualization of the spatial distribution of the functionalization on individual SWCNT bundle structures and discuss the CNT de-bundling mechanism via surface modification and the uniformity of the CNT dispersion state.

Carbon fibers

10.1039/c9nr07619k

Cite

Citations (13)