Superhydrophilicity

Schematic representation of possibie hydrogen bonding interactions between the triblock copolymer and PVPh homopoiymer [41], 

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Upon excitation of a semiconductor, the electrons in the conduction band and the hole in the valence band are active species that can initiate redox processes at the semiconductor-electrolyte interface, including photocorrosion of the semiconductor, a change in its surface properties (photoinduced superhydrophilicity [13]), and various spontaneous and non-spontaneous reactions [14-19]. These phenomena are basically surface-mediated redox reactions. The processes are depicted in Fig. 16.1. Owing to the slow spontaneous kinetic of the reactions between the... 

Understand how energy-rich electron-hole pairs can be utilised to produce electricity in photovoltaic solar cells, to drive chemical reactions where water is split into hydrogen and oxygen, to take part in photocatalytic reactions and to change the surface of the semiconductor, resulting in the phenomenon of superhydrophilicity. 

Understand that a consideration of similar ideas about photo-excited Ti02 leads to an explanation of a variety of effects, such as removal of pollutants in water and air, destruction of cells of pathogens and cancers, and the concept of semiconductor-photoinduced superhydrophilicity. 

Change the surface of the semiconductor, resulting in the phenomenon of superhydrophilicity (see Section 11.5). 

Figure 11.13 Schematic mechanism of the photoinduced superhydrophilicity of Ti02...

Furthermore, titanium oxide thin films have been found to exhibit a unique and useful function (i.e., a superhydrophilic property). Usually, the contact angle of a water droplet on a surface is 50 -70° therefore, metal oxide surfaces become cloudy when water is dropped on them or if there is moisture in the atmosphere. However, under UV light irradiation of the titanium oxide surfaces, this contact angle of water droplets becomes smaller, even reaching zero (superhydrophil-icity), its extent depending on the UV irradiation time and irradiation intensity. Thus, under UV light irradiation, titanium oxide thin-film surfaces never become... 

Sun T, Wang G, Feng L et al (2004) Reversible Switching between superhydrophilicity and superhydrophobicity. Angew Chem Int Ed 43 357-360... 

Superhydrophilic and superhydrophobic surfaces are more effective at stabilizing two-phase microflows. These surfaces can be obtained by creating roughness utilizing titanium nanoparticles. Titanium modification of a microchannel yields nanometer-scale surface roughness, and subsequent... 

Photocatalysis is classified into two categories. One is of apphcation to the improvement of living environment such as anti stain, self-cleaning, and superhydrophilicity [1]. Ti02 photocatalysts are widely used for these applications and many industrial products have been made. Another direction of... 

Fig. 11.21 a) Schematic representation of the superhydrophilicity phenomenon, b) Water contact angle on Ti02-coated glass as dependent on time. 

Figure 18. Comparing ordinary float glass (a) with anti-fogging glass with superhydrophilicity effect (b), were the water forms a thin sheet, with no fogging effect.

M. Kang, The superhydrophilicity of Al-Ti02 nanometer sized material synthesized using a solvothermal method , Materials letters, 59, 3122-3127, (2005). 

Xia F, Feng L, Wang ST, Sun TL, Song WL, Jiang WH, et al. Dual-responsive surfaces that switch superhydrophilicity and superhydrophobicity. Adv Mater 2006 18(4) 432—6. 

Stratakis E, Mateescu A, Barberoglou M, Vamvakaki M, Fotakis C, Anastasiadis SH. From superhydrophobicity and water repellency to superhydrophilicity smart polymer-functionalized surfaces. Chem Commun 2010 46(23) 4136—8. 

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