Effect of Contact Angle on droplet Evaporation. Control of Contact Angle by Photo-induced Hydrophilicity.

保之, 高田; 澄具, 日高; 弘志, 山本; 匡亨, 中村; 正孝, 増田; 猛宏, 伊藤

doi:10.1299/kikaib.68.1911

Cited by 1 publication

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“…(2) Certain humidity is required in ambient gas to take place of RISA hydrophilicity. (3) When the contact angle becomes smaller due to gamma ray irradiation, an XPS analysis indicates that the surface density of bridging oxygen becomes smaller.…”

Section: Resultsmentioning

confidence: 99%

Mechanism of Hydrophilicity by Radiation-Induced Surface Activation

Honjo

Furuya

Takamasa

et al. 2009

JPES

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When a metal oxide is irradiated by gamma rays, the irradiated surface becomes hydrophilic. This surface phenomenon is called as radiation-induced surface activation (RISA) hydrophilicity. In order to investigate gamma ray-induced and photoinduced hydrophilicity, the contact angles of water droplets on a titanium dioxide surface were measured in terms of irradiation intensity and time for gamma rays of cobalt-60 and for ultraviolet rays. Reciprocals of the contact angles increased in proportion to the irradiation time before the contact angles reached its super-hydrophilic state. The irradiation time dependency is equal to each other qualitatively. In addition, an effect of ambient gas was investigated. In pure argon gas, the contact angle remains the same against the irradiation time. This clearly indicates that certain humidity is required in ambient gas to take place of RISA hydrophilicity. A single crystal titanium dioxide (100) surface was analyzed by X-ray photoelectron spectrometry (XPS). After irradiation with gamma rays, a peak was found in the O1s spectrum, which indicates the adsorption of dissociative water to a surface 5-fold coordinate titanium site, and the formation of a surface hydroxyl group. We conclude that the RISA hydrophilicity is caused by chemisorption of the hydroxyl group on the surface.

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Section: Resultsmentioning

confidence: 99%