Studies of Surface Wettability Conversion on TiO<sub>2</sub> Single-Crystal Surfaces

Wang, Rong; Sakai, Nobuyuki; Fujishima, Akira; Watanabe, and Toshiya; Hashimoto, Kazuhito

doi:10.1021/jp983386x

Cited by 651 publications

(518 citation statements)

References 40 publications

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“…In this work, UV light can create controllable number of defects by controlling irradiation time or photon flux from low concentration (<4%) to high concentration (more than 20%, not shown here), similar to previous ESD results [4,11] and PSD results as gauged by X-ray photoemission spectroscopy (XPS) [12,13]. However, due to the high photo energy of X-ray, it can also make bridging oxygen desorbed from the surface, the results is not so accurate.…”

Section: Discussionsupporting

confidence: 87%

“…TiO 2 has been well known because of its important roles in catalytic activity, occurrence of the strong metal-support interaction, oxide growth rates in electrochemical cells, and so on [4,5]. Surface defects can be created by thermal annealing in UHV [6,7], evaporation of excess Ti [8,9], Ar + sputtering [6,7,10,11], electron stimulated desorption (ESD) [4,11], and ultraviolet (UV) photo-stimulated desorption (PSD) [12,13]. It is well established that thermal annealing in UHV usually creates relatively small quanti-ties of point defects (reduced Ti(Ti 3+ )), whereas, Ar + sputtering can produce much higher quantities of defects with mixed Ti oxidation states (Ti 3+ , Ti 2+ , and Ti + ).…”

Section: Introductionmentioning

confidence: 99%

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Suppression of Photoinduced BBO Defects Generation on TiO2(110) by Water

Yang

Guo

et al. 2013

Chinese Journal of Chemical Physics

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We have investigated creation of variable concentrations of defects on TiO 2 (110)-(1×1) surface by 266 nm laser using temperature programmed desorption technique. Oxygen-vacancy defects can be easily induced by ultraviolet light, the defects concentration has a linear dependence on power density higher than 50 mW/cm 2 for 90 s irradiation. No observation of O 2 molecule and Ti atom desorption suggests that UV induced defects creation on TiO 2 (110)-(1×1) is an effective and gentle method. With pre-dosage of thin films of water, the rate of defects creation on TiO 2 (110)-(1×1) is slower at least by two orders of magnitude than bare TiO 2 (110)-(1×1) surface. Further investigations show that water can be more easily desorbed by UV light, and thus desorption of bridging oxygen is depressed.

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Section: Discussionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Suppression of Photoinduced BBO Defects Generation on TiO2(110) by Water

Yang

Guo

et al. 2013

Chinese Journal of Chemical Physics

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“…It has been demonstrated that the surface becomes energetically unstable after the hydroxyl adsorption, while the oxygen adsorption is thermodynamically favored, and it is more strongly bonded on the defect sites than the hydroxyl group [18]. A similar result has also been observed on the TiO 2 surface [22,23]. Therefore, the hydroxyl groups adsorbed on the defective sites can be replaced gradually by oxygen atoms when the UV-irradiated films were placed in the dark.…”

Section: -P3mentioning

confidence: 67%

“…The former provides a photosensitive surface, which can be switched between hydrophilicity and hydrophobicity, and the latter further enhances these properties. In addition, the reversible conversions of the surface wettability proceed only by the adsorption and desorption of surface hydroxyl groups at the outmost layer of oxide films [22], while the structure below the outmost layer remains stable, free from changes in chemical conditions. Therefore, it is reasonable that the reversible wettability switching properties of the as-prepared films exhibit long-term durability.…”

Section: -P3mentioning

confidence: 99%

Photon-induced tunable and reversible wettability of pulsed laser deposited W-doped ZnO nanorods

Ngom

Sakho

Ndiaye

et al. 2011

Eur. Phys. J. Appl. Phys.

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Abstract. ZnO nanorods arrays were prepared on soda lime glass substrate by pulsed laser deposition method. Hexagonal rod-like ZnO rods were obtained under different conditions. Well-defined ZnO nanorods arrays were selected among different samples having various morphologies and sizes already studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). Here, we report on the contact angle measurement (CAM) of one of these samples. A systematic change of the surface wettability is observed in W-doped ZnO nanostructures. The water contact angle (WCA) of a 1 wt.% of WO 3 target content was found to be the transition doping level from hydrophilic surface to a hydrophobic surface. We attributed the transition in surface wettability of the film with the doping to incorporation increase of tungsten into the film. Such characteristic surface wettability can play a key role in the adhesion of various layers on W-ZnO nanorods arrays for optoelectronic device applications.

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“…To confirm this, we need further investigation. Wang et al 16) studied the surface wettability conversion of rutile TiO 2 single crystal surfaces. Using (110), (100) and (001) surfaces, they concluded that bridging site oxygen played an important role in the surface wettability conversions.…”

Section: )mentioning

confidence: 99%

Relationship between the photocatalytic activity and crystallographic orientation of rutile TiO<sub>2</sub> single crystals

Ikuma

Ogoe

Watanabe

et al. 2013

J. Ceram. Soc. Japan

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Although photocatalytic activity of TiO 2 is mainly discussed in terms of the band gap energy, the importance of surface oxygen for the decomposition of chemicals on the photocatalyst is emphasized in several reports. The availability and stability conditions of the surface oxygen atoms on TiO 2 crystals depend on the surface orientation of the crystals. In this study, rutile TiO 2 single crystals with different orientations are used and we evaluate the progress of photocatalytic decomposition reactions by the weight loss of the salad oil and linoleic acid due to formation of gaseous species. If the surface of rutile TiO 2 single crystals is not reconstructed and surface oxygen is involved, the orientation of the surface affects the photocatalytic activity of TiO 2 ; the photocatalytic activity increases in the order of (114) < (100) < (101) < (001).©2013 The Ceramic Society of Japan. All rights reserved.Key-words : Photocatalyst, Surface orientation, Rutile TiO 2 , Single crystal [Received August 15, 2012; Accepted October 15, 2012] When titanium dioxide (TiO 2 ) crystal is exposed to UV light, it exhibits photocatalytic activity 1) and hydrophilic behavior 2) at the crystal surface. The photocatalytic activity of TiO 2 is mainly discussed in terms of the band gap energy, 3),4) because a light with a certain energy is required to promote electrons from the valence band to the conduction band. The electronhole pairs created are used to reduce and oxidize chemicals that are near the photocatalyst.There are, however, other factors that are also important for the photocatalytic activity of TiO 2 . The importance of surface oxygen for the decomposition of chemicals on the photocatalyst is emphasized in some reports. 5),6) Wilson and Idriss 5),6) have shown that the oxygen of TiO 2 is involved in the decomposition reaction of acetic acid at the surface. An electron at the surface reacts with an oxygen molecule in the gas phase to produce O 2 minus radical (O 2 ¹ •) which then reacts with chemicals on the surface to form other intermediates. The final reaction products are CH 4 /C 2 H 6 and CO 2 . The main reactions are as follows:CH 3 COOH ðAds:Þ ! CO 2 ðgÞ þ CH 4 ðgÞ ð 1Þ 2CH 3 COOH ðAds:Reaction (2) suggests that surface oxygen atoms (O s ) on TiO 2 crystals play an important role in the decomposition (or oxidation) of acetic acid. Although surface atoms or ions, which are energetically unstable, are surrounded by fewer atoms or ions compared to bulk atoms or ions, the availability and stability conditions of the surface oxygen atoms on TiO 2 crystals depend on the surface orientation of the crystals. Lowekamp et al. 8) have reported the orientation dependence of photocatalytic reactions on TiO 2 film surfaces and the anisotropic photocatalytic reaction on polycrystalline TiO 2 . 9) In the two papers, they studied the following reaction:Their findings showed that TiO 2 grains with the (100) and (110) rutile TiO 2 surfaces have lower photoreduction rates than those with the (101), (111) and (001) surfaces, and ...

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Studies of Surface Wettability Conversion on TiO₂ Single-Crystal Surfaces

Cited by 651 publications

References 40 publications

Suppression of Photoinduced BBO Defects Generation on TiO2(110) by Water

Suppression of Photoinduced BBO Defects Generation on TiO2(110) by Water

Photon-induced tunable and reversible wettability of pulsed laser deposited W-doped ZnO nanorods

Relationship between the photocatalytic activity and crystallographic orientation of rutile TiO<sub>2</sub> single crystals

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Studies of Surface Wettability Conversion on TiO2 Single-Crystal Surfaces

Cited by 651 publications

References 40 publications

Suppression of Photoinduced BBO Defects Generation on TiO2(110) by Water

Suppression of Photoinduced BBO Defects Generation on TiO2(110) by Water

Photon-induced tunable and reversible wettability of pulsed laser deposited W-doped ZnO nanorods

Relationship between the photocatalytic activity and crystallographic orientation of rutile TiO<sub>2</sub> single crystals

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Studies of Surface Wettability Conversion on TiO₂ Single-Crystal Surfaces