Faculty Profiles - YASUDA, Keiji

Papers - YASUDA, Keiji

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Behavior of sonochemical reaction in a small pipe Reviewed

Vol. 64 ( 3 ) 2025.3

Size control of Au@Pt core-shell nanoparticles for enhanced catalytic activity using ultrafine bubbles and ultrasound Reviewed

Vol. 64 ( 3 ) 2025.3

Synthesis of Au@Pd core-shell nanoparticles by ultrafine bubbles and ultrasound without capping and reducing agents Reviewed

Vol. 53 ( 7 ) 2024.7

Dependence of reaction on vessel position, diameter, and liquid height in the sonochemical reactor with indirect irradiation Reviewed Open Access

Yasuda, K; Yamazaki, T; Asakura, Y

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 63 ( 4 ) 2024.4

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

To investigate the sonochemical reaction performance caused by the indirect irradiation at 500 kHz, the glass vessel and a KI aqueous solution were used. Both the ultrasonic power and reaction rate had maximum values at every half wavelength of ultrasound. When the vessel position was adjusted to a larger absolute value of transducer impedance, the reaction rate became higher. The reaction rate and ultrasonic power increased as the vessel position moved closer to the transducer. The reaction rate first increased as the electric power applied to the transducer increased, reached a maximum value, and then decreased. This decrease phenomenon is called quenching of the sonochemical reaction. Before the quenching occurrs, the reaction rate per unit volume almost linearly increased with ultrasonic power density. The effects of the vessel diameter and liquid height on the relationship between the reaction rate per unit volume and the ultrasonic power density were small.

DOI： 10.35848/1347-4065/ad2d09

Open Access

Web of Science

Scopus

Evaluation of solvent property of air-water interface based on the fluorescence spectra of 1,2′-dinaphthylamine in the aqueous solution of ultrafine bubbles Reviewed Open Access

Kodama, K; Hattori, S; Yasuda, K; Saitoh, T

ANALYTICAL SCIENCES Vol. 40 ( 2 ) page： 341 - 345 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Analytical Sciences

Solvent property of air–water interface was evaluated based on the fluorescence spectra of 1,2′-dinaphthylamine in water containing ultrafine bubbles (average diameter: 103 nm, standard deviation: 38 nm). Among naphthylamine derivatives whose fluorescence spectra were responsive to microscopic hydrophobicity, 1,2′-dinaphthylamine (DN) was selected because its wavelength of the maximum emission (λmax) was significantly dependent on the concentration and microenvironment of the ultrafine bubble. The λmax value of DN in water was 486 nm, while it shifted to shorter wavelength (408 nm) in the presence of 1.09 × 109 mL−1 of ultrafine bubbles. The shift of λmax value indicates that DN adsorbs on the surfaces of ultrafine bubbles and exists in hydrophobic region rather than in bulk water. By comparing with the λmax values in different solvents, the surface of ultrafine bubble was found to have similar solvent property to ethyl ether or ethyl acetate that are widely used as extracting solvents for hydrophobic organic compounds. Graphical abstract: (Figure presented.)

DOI： 10.1007/s44211-023-00454-x

Characteristics and Application of Ultrafine Bubbles Invited Reviewed

YASUDA Keiji

Vacuum and Surface Science Vol. 66 ( 11 ) page： 631 - 638 2023.11

Authorship：Lead author,　Last author,　Corresponding author Language：Japanese Publisher：The Japan Society of Vacuum and Surface Science

Ultrafine bubbles (bulk nanobubbles), small bubbles less than 1 µm in diameter, have attracted academic and industrial attention because they have numerous advantages, including chemical-free nature and extraordinarily long lifetime. Since Brownian motion velocity is much higher than buoyancy, ultrafine bubble lifetime is more than several months. But stable mechanism is still unclear, even though their inside is highly pressured. They have several characteristics, such as pH-dependent surface charge and reduction in friction. Ultrafine bubbles are generated and removed by selecting the ultrasonic frequency. This review discusses the fundamental characteristics of ultrafine bubbles and their applications. Ultrafine bubbles effectively remove proteins, dyes, and inorganic salts from solid surfaces. Ultrafine bubbles promote adsorption, desorption and extraction. Gold nanoparticles, nanocomposites of CaCO3 and pulp fiber, and follow nanoparticles are synthesized using ultrafine bubbles. Thus, ultrafine bubbles have been shown to be powerful, environmentally friendly, safe, clean, simple, and inexpensive methods.

DOI： 10.1380/vss.66.631

CiNii Research

Development of high efficiency sonochemical reactors Invited Reviewed

Yasuda Keiji, Asakura Yoshiyuki

THE JOURNAL OF THE ACOUSTICAL SOCIETY OF JAPAN Vol. 79 ( 11 ) page： 569 - 575 2023.11

超音波霧化とウルトラファインバブルによるアミノ酸の濃縮 Invited

安田啓司

超音波TECHNO Vol. 35 ( 5 ) page： 50 - 53 2023.9

Characteristics of Ultrafine Bubbles (Bulk Nanobubbles) and Their Application to Particle-Related Technology Invited Open Access

Yasuda Keiji

KONA Powder and Particle Journal Vol. 41 ( 0 ) page： 183 - 196 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Hosokawa Powder Technology Foundation

Ultrafine bubbles (bulk nanobubbles), small bubbles with a diameter of less than 1 μm, have attracted academic and industrial attention because of their numerous advantages, including their chemical-free nature and extraordinarily long lifetime. The long lifetime is related to the much higher Brownian motion velocity compared to buoyancy. The reason why ultrafine bubbles can endure under stable conditions is still unclear, even though their inside is highly pressured. They have several characteristics, such as pH-dependent surface charge and reduced friction. They are also closely related to ultrasound. Ultrafine bubbles are generated and removed by selecting the ultrasonic frequency. Reaction and separation using ultrasonic cavitation and atomization, respectively, are enhanced by ultrafine bubbles. They can produce hollow nanoparticles, enhance adsorption on activated carbon, and clean solid surfaces. This review discusses the fundamental and ultrasonic characteristics of ultrafine bubbles and their application in particle-related technology, encompassing fine particle synthesis, adsorption, desorption, extraction, cleaning, and prevention of fouling.

DOI： 10.14356/kona.2024004

液中プラズマ法によるナノグラフェン合成に及ぼす超音波の影響 Invited

安田啓司, 長谷川健太, 近藤博基, 堀勝

超音波TECHNO Vol. 34 ( 5 ) page： 42 - 46 2022.10

ウルトラファインバブルのソノケミストリーへの応用 Invited

Bulletin of the Japan Society of Sonochemistry Vol. 16 ( 2 ) page： 26 - 34 2022.9

ファインバブルの特徴 Invited

安田啓司

粉体技術 Vol. 14 ( 8 ) page： 597 - 601 2022.8

Enrichment of amino acids from its aqueous solution by ultrasonic atomization and ultrafine bubbles Reviewed Open Access

Vol. 61 ( SG ) page： SG10321 - SG10325 2022.7

ウルトラファインバブルによる超音波合成した金ナノ粒子の粒子径制御 Invited

安田啓司

超音波TECHNO Vol. 34 ( 3 ) page： 83 - 87 2022.6

Study on the efficiency of a transducer for sonochemistry by calorimetry Reviewed

Y. Asakura and K. Yasuda

Japanese Journal of Applied Physics Vol. 61 page： GS1032 2022.5

Curcumin-loaded liposome preparation in ultrasound environment under pressurized carbon dioxide Reviewed Open Access

Wahyudiono, J. He, X. Hu, S. Machmudah, K. Yasuda, S. Takami, H. Kanda, M. Goto

FOODS Vol. 11 ( 10 ) page： 1469 2022.5

Generation and Reduction of Ultrafine Bubbles by Ultrasonic Irradiation Invited

YASUDA Keiji, ASAKURA Yoshiyuki

JAPANESE JOURNAL OF MULTIPHASE FLOW Vol. 36 ( 1 ) page： 12 - 19 2022.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：THE JAPANESE SOCIETY FOR MULTIPHASE FLOW

Ultrasound was irradiated to ultrapure water. Ultrafine bubbles with a diameter of 90 - 100 nm were generated. Number concentration of ultrafine bubbles increased with time and approached asymptotically to an equilibrium value. Ultrafine bubble concentration increased with increasing ultrasonic power and decreasing frequency. For comparison, highly concentrated ultrafine bubble water was prepared by pressurized dissolution method, and ultrasound was also irradiated to the ultrafine bubble water. Reduction of ultrafine bubbles was observed and ultrafine bubble concentration decreased to the equilibrium value. Ultrafine bubble concentration decreased with increasing ultrasonic power and frequency. Generation and reduction of ultrafine bubbles by ultrasound was modeled to analyze experimental data. The results calculated by our model were in good agreement with the experimental data.

DOI： 10.3811/jjmf.2022.t002

CiNii Research

Frequency and power dependence of ultrasonic degassing Reviewed Open Access

Asakura Y., Yasuda K.

Ultrasonics Sonochemistry Vol. 82 page： 105890 - 1058908 2022.1

Frequency and power dependence of the sonochemical reaction Reviewed Open Access

Ultrasonics Sonochemistry Vol. 81 page： 105858 - 1058587 2021.12

超音波によるウルトラファインバブルの生成・消滅と高純度な金ナノ粒子の合成 Invited

安田啓司

化学工業 Vol. 72 ( 7 ) page： 441 - 446 2021.7

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Papers - YASUDA, Keiji