Time-and Space-resolved Optical Diagnostics for Discharge Plasmas Separately Formed in Aqueous Solution

Banno, Motohiro; Takakuwa, H.; Yui, Hiroharu

doi:10.2116/analsci.33.1053

Cited by 2 publications

(1 citation statement)

References 23 publications

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“…From these results, two SPs with different properties were simultaneously generated by utilizing the separate-mode discharge and our system enables us to observe these differences separately with microscopic spatial resolution. 30)…”

Section: Extending Of the Application Of Sp Towards Chemical Reaction...mentioning

confidence: 99%

Microspectroscopic imaging of solution plasma: How do its physical properties and chemical species evolve in atmospheric-pressure water vapor bubbles?

Yui

Banno

2017

Jpn. J. Appl. Phys.

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In this article, we review the development of scientific instruments for obtaining information on the evolution of physical properties and chemical species of solution plasma (SP). When a pulsed high voltage is applied between electrodes immersed in an aqueous solution, SP is formed in water vapor bubbles transiently generated in the solution under atmospheric pressure. To clarify how SP emerges in water vapor bubbles and is sustained in solutions, an instrument with micrometer spatial resolution and nanosecond temporal resolution is required. To meet these requirements, a microscopic system with a custom-made optical discharge cell was newly developed, where the working distance between the SP and the microscopic objective lens was minimized. A hollow electrode equipped in the discharge cell also enabled us to control the chemical composition in water vapor bubbles. To study the spatial and temporal evolutions of chemical species in micrometer and nano-to microsecond regions, a streak camera with a spectrometer and a CCD detector with a time-gated electronic device were combined with the microscope system. The developed instrument is expected to contribute to providing a new means of developing new schemes for chemical reactions and material syntheses.

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Section: Extending Of the Application Of Sp Towards Chemical Reaction...mentioning

confidence: 99%

Microspectroscopic imaging of solution plasma: How do its physical properties and chemical species evolve in atmospheric-pressure water vapor bubbles?

Yui

Banno

2017

Jpn. J. Appl. Phys.

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Atmospheric discharge plasma in aqueous solution: Importance of the generation of water vapor bubbles for plasma onset and physicochemical evolution

Yui

Someya

Kusama

et al. 2018

Journal of Applied Physics

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Discharge plasma formed in aqueous solutions has attracted much attention for its applications in environmental purification and material syntheses. The onset and evolution of the discharge plasma in an aqueous solution and transient reactive species formed in it are successfully monitored with micrometer spatial resolution and nanosecond temporal resolution. The combination of a custom-made microscopic discharge system and a high-speed camera provides direct evidence that water vapor bubbles form before the discharge with the thermal phase transition of aqueous solution at the electrode tip. The water vapor bubbles, i.e., locally formed space in the gas phase, connect the gap between the tips of the opposed electrodes. The local gas area formed in aqueous solution plays a crucial role in the ignition and continuance of the discharge plasma. It is also found that the initially formed plasma lasts for under 100 ns and quenches rapidly. However, plasma regenerates in the water vapor bubble and successively bridges the opposing electrodes during the pulsed-voltage application (ca. 1 μs). These two temporally distinct generations of plasma, i.e., the initial plasma (IP) and the following successive plasma (SP), can be seen to correspond to the dielectric breakdown and glow-like plasma, respectively. These results provide an important picture for the proposed mechanism for plasma evolution in water and also important information for the efficient control of the discharge plasma with its applications in waste-water treatments, nanomaterial syntheses with plasma oxidation–reduction reactions, and the chemical modification of the material surfaces in aqueous solutions as a form of “green chemistry.”

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Time-and Space-resolved Optical Diagnostics for Discharge Plasmas Separately Formed in Aqueous Solution

Cited by 2 publications

References 23 publications

Microspectroscopic imaging of solution plasma: How do its physical properties and chemical species evolve in atmospheric-pressure water vapor bubbles?

Microspectroscopic imaging of solution plasma: How do its physical properties and chemical species evolve in atmospheric-pressure water vapor bubbles?

Atmospheric discharge plasma in aqueous solution: Importance of the generation of water vapor bubbles for plasma onset and physicochemical evolution

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