Superwetting of TiO
            <sub>2</sub>
            by light-induced water-layer growth via delocalized surface electrons

Lee, Kunyoung; Kim, QHwan; An, Sangmin; An, JeongHoon; Kim, Jong-Woo; Kim, Bongsu; Jhe, Wonho

doi:10.1073/pnas.1319001111

Cited by 35 publications

(36 citation statements)

References 39 publications

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“…This friction reduction is attributed to the existence of the ordered water structures on the superhydrophilic surface with appropriate charge patterns, and the friction between this ordered water monolayer and the water molecules above is small. In practical applications, the ordered water monolayers have been observed on several real solid surfaces, 27,[36][37][38][39][40][41]44 suggesting that there is a high probability that materials associated with unique friction properties existing. Figure 1A, we have implemented the nonequilibrium Couette flow to investigate the surface friction based on molecular dynamics simulations.…”

Section: ■ Introductionmentioning

confidence: 99%

Friction Reduction at a Superhydrophilic Surface: Role of Ordered Water

Wang

Wen

et al. 2015

J. Phys. Chem. C

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Low-friction but superhydrophilic materials are urgently needed in biomedical and engineering fields because of their nonfouling property and biocompatibility, particularly when the surfaces are definitely superhydrophilic, such as metal or TiO 2 as the surface coatings of the intravascular stents. However, generally, there is a higher friction coefficient on the superhydrophilic surfaces than on the hydrophobic surfaces. On the basis of molecular dynamics simulations, we show that the friction on the superhydrophilic surface with appropriate charge patterns is evidently reduced, where the lower friction is similar to that of a rather hydrophobic surface with a contact angle of water droplet of ∼44°. This reduction is attributed to the existence of an ordered water monolayer on the superhydrophilic surface with appropriate charge patterns, and the friction between this ordered water monolayer and the water molecules above is small. ■ INTRODUCTIONThe nature of surface boundary friction, 1−14 related with the development of microfluidic and nanofluidic systems, 15−19 the surface lubrication and nanotribology, 3−7 and the motion of biological molecules, 20 has long been a subject of interest. One main challenge is how to effectively reduce the friction between materials and water, which is important in various applied fields, such as self-clearing materials with superhydrophobic porous nanostructures, 13 the biomedical materials, 7,9 and nanocoating materials of ships. 21 It is generally accepted that there is relatively low friction on hydrophobic surfaces but relatively high friction on hydrophilic or superhydrophilic surfaces. 15,22−26 However, hydrophobic materials are deficient in terms of biocompatibility and their nonfouling properties, which are exactly important for applications, such as the coatings of marine or ship surfaces to prevent fouling with nonspecific proteins. 9,21 Thus, when surfaces are definitely superhydrophilic, such as the TiO 2 27 or metal Ta 28 as the surface coatings of the intravascular stents, low-friction materials in merit of nonfouling are of urgent need in applications. 9 For example, implanted intravascular stents and catheters with high biocompatibility require low friction so they can be easily maneuvered within the patient's vasculature; 9,29 the surfaces coatings of marine or ship that can prevent the fouling with nonspecific proteins also require the low surface friction to save energy in the navigation of the ships. 21 In 2009, we predicted a unique wetting phenomenon with a water droplet on a water monolayer on a superhydrophilic surface with a water layer completely spreading over the surfaces with rather high surface water interactions at room temperature, which was termed an ordered water monolayer that does not completely wet water. 30−35 A similar phenomenon has also been observed on many real solid surfaces in experimental 27,36−38 or numerical studies. 39−41 However, whether this ordered water on the solid surface with charges results in friction reduction is still ...

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Section: ■ Introductionmentioning

confidence: 99%

Friction Reduction at a Superhydrophilic Surface: Role of Ordered Water

Wang

Wen

et al. 2015

J. Phys. Chem. C

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“…The interaction between water and oxides is important to control function in many technological applications, including water splitting 1,2,3,4,5,6,7 , rechargeable metal-air batteries 8,9,10,11,12 , surface wetting and self-cleaning 13,14,15,16 , photocatalysis 15,17,18,19,20 , sensors 15 , and proton-conducting oxide membranes 21,22,23,24 . Recent studies have shown that decreasing coverage of hydroxyl groups on a perovskite oxide surface at the water/oxide interface not only reduces wetting and but also enhances oxygen reduction kinetics in a basic solution 14 atom and hydroxyl group in the lattice oxygen site, respectively).…”

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confidence: 99%

Nanoscale structural oscillations in perovskite oxides induced by oxygen evolution

et al. 2016

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Understanding the interaction between water and oxides is critical for many technological applications, including energy storage, surface wetting/self-cleaning, photocatalysis and sensors. Here, we report observations of strong structural oscillations of BaSrCoFeO (BSCF) in the presence of both HO vapour and electron irradiation using environmental transmission electron microscopy. These oscillations are related to the formation and collapse of gaseous bubbles. Electron energy-loss spectroscopy provides direct evidence of O formation in these bubbles due to the incorporation of HO into BSCF. SrCoO was found to exhibit small oscillations, while none were observed for LaSrCoO and LaCoO. The structural oscillations of BSCF can be attributed to the fact that its oxygen 2p-band centre is close to the Fermi level, which leads to a low energy penalty for oxygen vacancy formation, high ion mobility, and high water uptake. This work provides surprising insights into the interaction between water and oxides under electron-beam irradiation.

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“…water layer, which is attributed to the ''water wets water'' mechanism, affected the application of TiO2 film in a dark or non-UV environment [21,22]. Surface-engineered silica materials (SESMs) possessing surface activity successfully removed organic pollutants and bacteria from water [23][24][25][26].…”

Section: Resultsmentioning

confidence: 99%

Application of Super-Amphiphilic Silica-Nanogel Composites for Fast Removal of Water Pollutants

et al. 2016

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This work first reports the preparation of super-amphiphilic silica-nanogel composites to reduce the contact angle of water to increase the diffusion of pollutant into adsorbents. In this respect, the silica nanoparticles were encapsulated into nanogels based on ionic and nonionic polyacrylamides by dispersion polymerization technique. The morphologies and the dispersion stability of nanogel composites were investigated to clarify the ability of silica-nanogel composites to adsorb at different interfaces. The feasibility of silica polyacrylamide nanogel composites to act as a high-performance adsorbent for removal of methylene blue (MB) dye and heavy metals (Co 2+ and Ni 2+ ) from aqueous solution was investigated. The surface tension, contact angle, average pore size, and zeta potential of the silica-nanogel composites have been evaluated. The MB dye and heavy metal adsorption capacity achieved Q max = 438-387 mg/g which is considerably high. The adsorption capacity results are explained from the changes in the morphology of the silica surfaces as recorded from scanning electron microscopy (SEM).

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Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons

Cited by 35 publications

References 39 publications

Friction Reduction at a Superhydrophilic Surface: Role of Ordered Water

Friction Reduction at a Superhydrophilic Surface: Role of Ordered Water

Nanoscale structural oscillations in perovskite oxides induced by oxygen evolution

Application of Super-Amphiphilic Silica-Nanogel Composites for Fast Removal of Water Pollutants

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Superwetting of TiO 2 by light-induced water-layer growth via delocalized surface electrons

Cited by 35 publications

References 39 publications

Friction Reduction at a Superhydrophilic Surface: Role of Ordered Water

Friction Reduction at a Superhydrophilic Surface: Role of Ordered Water

Nanoscale structural oscillations in perovskite oxides induced by oxygen evolution

Application of Super-Amphiphilic Silica-Nanogel Composites for Fast Removal of Water Pollutants

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Product

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Superwetting of TiO ₂ by light-induced water-layer growth via delocalized surface electrons