Reversible wettability control of TiO 2 surface by light irradiation

Miyauchi, Masahiro; Kieda, Nobuo; Hishita, Shunichi; Mitsuhashi, T.; Nakajima, Akira; Watanabe, Toshiya; Hashimoto, Kazuhito

doi:10.1016/s0039-6028(02)01551-0

Cited by 203 publications

(173 citation statements)

References 30 publications

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“…The mechanism of the former phenomenon, photocatalytic oxidative decomposition, has been almost clarified and that of the latter, photoinduced superhydrophilicity, has been partly clarified, i.e., changes in the structure of the photocatalyst surface due to photogenerated positive holes [2]. action spectra of photoinduced changes in WCA were measured for titania-coated glass substrates in the present study.…”

Section: Introductionmentioning

confidence: 84%

“…10 deg., relatively low compared with that of single crystal titania [2]. WCA depends on not only the chemical composition of the solid surface, e.g., density of surface hydroxyls, but also macroscopic structure, e.g., surface roughness; it is well known that porosity of solids enhances both hydrophilicity and hydrophobicity.…”

Section: Change In Wca For Titania-coated Glass Plates Without Low-tementioning

confidence: 99%

“…On the other hand, as far as we know, there have been no such action spectrum analyses of photoinduced superhydrophilicity. In order to confirm that redox reactions by photogenerated positive holes or electrons initiate the photoinduced superhydrophilicity, ] and has been applied practically, e.g., for decomposition of organic and inorganic contaminants in air and water [2]. Coating of window-glass plates and outdoor walls with a photocatalyst is effective for keeping the surface clean.…”

Section: Introductionmentioning

confidence: 99%

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Action spectrum analyses of photoinduced superhydrophilicity of titania thin films on glass plates

et al. 2008

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Samples of titania-thin-film-coated glass plates were prepared by spin coating of commercial titania-coating liquids using a home-made spin coater (1000 rpm, 30 s) and then calcined in air at 673 K for 2 h. In a part of experiments, samples were stored in an oven at 393 K overnight. A piece of sample was set in a 10-mm rectangular quartz cell, and monochromatic light (FWHM of ca. 17 nm, intensity of ca. 10 8 einstein s -1 ) was irradiated in ambient air using a grating multiple-wavelength photoirradiation instrument (Jasco CRM-FD).Water contact angle (WCA) of samples before and after monochromatic irradiation was measured by a contact angle analyzer. Changes in WCA, as a function of wavelength of monochromatic irradiation, a kind of action spectrum, of several titania samples showed that the sample surfaces became superhydrophilic, i.e., WCA became almost zero, only under irradiation with a wavelength shorter than the absorption edge, corresponding to the band gap, of samples. Analysis of changes in WCA showed that there are at least two stages when the samples stored at 393 K overnight before irradiation to give relatively high WCA of ca. 40 deg. were used: first stage of WCA > 10 deg. and second stage of WCA < 10 deg.. The action spectra of WCA change in these two stages are discussed.

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Section: Introductionmentioning

confidence: 84%

Section: Change In Wca For Titania-coated Glass Plates Without Low-tementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Action spectrum analyses of photoinduced superhydrophilicity of titania thin films on glass plates

et al. 2008

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“…Heat treatment can accelerate the elimination of surface hydroxyl groups 34. As a result, the surface reverts back to its original state (before UV irradiation) by means of dark storage (or heat treatment), and the wettability is reconverted from hydrophilicity to hydrophobicity again [35]. We did not apply heating or other actions in order to stimulate the reconverting of the ZnO surfaces from hydrophilicity to hydrophobicity.…”

Section: Uv Irradiation Effect On the Wettability Of Zno Nanostructuresmentioning

confidence: 99%

Surface morphology effects on the light-controlled wettability of ZnO nanostructures

Khranovskyy

Ekblad

Yakimova

et al. 2012

Applied Surface Science

116

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ZnO nanostructures of diverse morphology with shapes of corrals and cabbages as well as open and filled hexagons and sheaves prepared by APMOCVD technique, are investigated with water contact angle (CA) analysis. The as-grown ZnO nanostructures exhibit pure hydrophobic behavior, which is enhanced with the increase of the nanostructure's surface area. The most hydrophobic structures (CA = 124°) were found to be the complex nanosheaf, containing both the macro-and nanoscale features. It is concluded that the nanoscale roughness contributes significantly to the hydrophobicity increase. The character of wettability was possible to switch from hydrophobic to superhydrophilic state upon ultra violet irradiation. Both the rate and amplitude of the contact angle depend on the characteristic size of nanostructure. The observed effect is explained due to the semiconductor properties of zinc oxide enhanced by increased surface chemistry effect in nanostructures.

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“…As a result, the surface evolves back to its original state (before UV irradiation), and the wettability is reconverted from hydrophilicity to hydrophobicity again. [19] 4. CONCLUSIONS Microstructure, surface topography and wettability of ZnO thin films deposited at different solution concentrations were measured by XRD, FE-SEM, AFM and home-made water contact angle apparatus.…”

Section: +mentioning

confidence: 99%

Influence of solution concentrations on surface morphology and wettability of ZnO thin films

Liu

Wang

et al. 2013

Electron. Mater. Lett.

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ZnO thin films were grown on silicon substrates using a hydrothermal method. The XRD patterns show that all of the peaks can be attributed to the wurtzite structures of ZnO. The TC value of (002) plane and average crystal size increase first and then decrease with the increase of solution concentration. SEM and AFM results show that many dense hexagonal cylinder particles have been observed on the surface of the thin films, which grown at 0.08 and 0.10 mol/L. The surface roughness of the thin films deposited at 0.06, 0.08, 0.10, and 0.12 mol/L are 24.5, 38.3, 32.0, and 39.4 nm, respectively. Surface wettability results show that the preferential orientation along c-axis and surface roughness contribute significantly to the hydrophobicity. The reversible switching between hydrophobicity and hydrophilicity is related to the synergy of the transition of wetting model, surface crystal structure, and surface roughness.

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Reversible wettability control of TiO 2 surface by light irradiation

Cited by 203 publications

References 30 publications

Action spectrum analyses of photoinduced superhydrophilicity of titania thin films on glass plates

Action spectrum analyses of photoinduced superhydrophilicity of titania thin films on glass plates

Surface morphology effects on the light-controlled wettability of ZnO nanostructures

Influence of solution concentrations on surface morphology and wettability of ZnO thin films

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