Fast and Reversible Wettability Transitions on ZnO Nanostructures

Zhang, Z.; Chen, H.; Zhong, Jiaming; Saraf, Gaurav; Lu, Yicheng

doi:10.1007/s11664-007-0126-4

Cited by 50 publications

(32 citation statements)

References 16 publications

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“…Water-droplet was spread equally in all directions instead of forming hilly-like dome once water droplet fixed on it [24]. In the present case, cobalt ferrite film showed hydrophilic surface with 41 (±2)…”

Section: Resultsmentioning

confidence: 53%

Cobalt Ferrite Nanocrystallites for Sustainable Hydrogen Production Application

Gaikwad

Chae

Mane

et al. 2011

International Journal of Electrochemistry

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Cobalt ferrite, CoFe 2 O 4 , nanocrystalline films were deposited using electrostatic spray method and explored in sustainable hydrogen production application. Reflection planes in X-ray diffraction pattern confirm CoFe 2 O 4 phase. The surface scanning microscopy photoimages reveal an agglomeration of closely-packed CoFe 2 O 4 nanoflakes. Concentrated solar-panel, a two-step water splitting process, measurement technique was preferred for measuring the hydrogen generation rate. For about 5 hr sustainable, 440 mL/hr, hydrogen production activity was achieved, confirming the efficient use of cobalt ferrite nanocrystallites film in hydrogen production application.

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Section: Resultsmentioning

confidence: 53%

Cobalt Ferrite Nanocrystallites for Sustainable Hydrogen Production Application

Gaikwad

Chae

Mane

et al. 2011

International Journal of Electrochemistry

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“…The water contact angles (CAs) of the as-grown ZnO NR and ZnO/ Si HR surfaces were below 5°, which indicated superhydrophilic wettability due to the -OH functional groups on the hydrothermally grown ZnO NR surface. 42 The bare Si MPs exhibited moderate hydrophilic wettability with water CAs of~50°. To reduce the surface energy and render the surfaces superhydrophobic, a Teflon AF solution (PTFE) was spin coated on the samples.…”

Section: Resultsmentioning

confidence: 97%

Combining the lotus leaf effect with artificial photosynthesis: regeneration of underwater superhydrophobicity of hierarchical ZnO/Si surfaces by solar water splitting

Lee

Yong

2015

NPG Asia Mater

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Fabrication of stable superhydrophobic surfaces in dynamic circumstances is a key issue for practical uses of non-wetting surfaces. However, superhydrophobic surfaces have finite lifetime in underwater conditions due to the diffusion of gas pockets into the water. To overcome this limited lifetime of underwater superhydrophobicity, this study introduces a novel method for regenerating a continuous air interlayer on superhydrophobic ZnO nanorod/Si micropost hierarchical structures (HRs) via the combination of two biomimetic properties of natural leaf: superhydrophobicity from the lotus leaf effect and solar water splitting from photosynthesis. The designed n/p junction in the ZnO/Si HRs allowed for highly stable gas interlayer in water and regeneration of the underwater superhydrophobicity due to the unique ability of the surface to capture and retain a stable gas layer. Furthermore, we developed a model to determine the optimum structural factors of hierarchical ZnO/Si surfaces that aid the formation of an air interlayer to completely regenerate the superhydrophobicity. We also verified that this model satisfactorily predicted the regeneration of underwater superhydrophobicity under various experimental conditions. The regenerative method developed in this work is expected to broaden the range of potential applications involving superhydrophobic surfaces and to create new opportunities for related technologies. NPG Asia Materials (2015) 7, e201; doi:10.1038/am.2015.74; published online 17 July 2015 INTRODUCTIONSuperhydrophobic surfaces that mimic lotus leaves have been extensively studied over the past several decades, and various micro/nanostructures have been developed to create bio-inspired superhydrophobic surfaces. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] In recent years, the non-wetting property of superhydrophobic surfaces submerged in water has attracted much attention because it has potential applications in drag reduction, anti-fouling, anti-corrosion, waterproof devices, microchannels, anti-icing and other non-wetting related applications. [16][17][18][19][20][21][22][23][24][25] Practical applications of non-wetting surfaces, however, have been impeded by the limited stability of their underwater superhydrophobicity. [26][27][28] According to the Cassie-Baxter model, the presence of an air interlayer on the submerged surface causes the non-wetting behavior, and thus, the stability of underwater superhydrophobicity is determined by the lifetime of the air (or gas) interlayer captured by the superhydrophobic surface. 29 However, the gas interlayer is unstable due to diffusion of the gas into the water. 30 According to previous studies, the gas diffusion rates are strongly affected by physical (hydrostatic pressure and micro/nanostructures of the surface) and chemical (surface energy) factors. 26,31

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“…[20] Reversible WCA changes on various oxide surfaces have also been described for TiO 2 , [12][13][14] SnO 2 , [15] and ZnO. [16][17][18][19] The WCA drops to a low value after several hours of UV-light irradiation and the initial high WCA is recovered after storage in the dark for more than a week. These treatment times are not compatible with smart device applications, for which the switch from one state to another should take only a few seconds or less.…”

mentioning

confidence: 94%