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Nucleation processes of nanobubbles at a solid/water interface.

Fang CK, Ko HC, Yang CW, Lu YH, Hwang IS - Sci Rep (2016)

Bottom Line: Experimental investigations of hydrophobic/water interfaces often return controversial results, possibly due to the unknown role of gas accumulation at the interfaces.These ordered domains may be the interfacial hydrophilic gas hydrates and/or the long-sought chemical surface heterogeneities responsible for contact line pinning and contact angle hysteresis.The gradual nucleation and growth of hydrophilic ordered domains renders the original homogeneous hydrophobic/water interface more heterogeneous over time, which would have great consequence for interfacial properties that affect diverse phenomena, including interactions in water, chemical reactions, and the self-assembly and function of biological molecules.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan.

ABSTRACT
Experimental investigations of hydrophobic/water interfaces often return controversial results, possibly due to the unknown role of gas accumulation at the interfaces. Here, during advanced atomic force microscopy of the initial evolution of gas-containing structures at a highly ordered pyrolytic graphite/water interface, a fluid phase first appeared as a circular wetting layer ~0.3 nm in thickness and was later transformed into a cap-shaped nanostructure (an interfacial nanobubble). Two-dimensional ordered domains were nucleated and grew over time outside or at the perimeter of the fluid regions, eventually confining growth of the fluid regions to the vertical direction. We determined that interfacial nanobubbles and fluid layers have very similar mechanical properties, suggesting low interfacial tension with water and a liquid-like nature, explaining their high stability and their roles in boundary slip and bubble nucleation. These ordered domains may be the interfacial hydrophilic gas hydrates and/or the long-sought chemical surface heterogeneities responsible for contact line pinning and contact angle hysteresis. The gradual nucleation and growth of hydrophilic ordered domains renders the original homogeneous hydrophobic/water interface more heterogeneous over time, which would have great consequence for interfacial properties that affect diverse phenomena, including interactions in water, chemical reactions, and the self-assembly and function of biological molecules.

No MeSH data available.


Related in: MedlinePlus

Apparent height profiles of the fluid structure indicated by a white arrow in Fig. 2. (a) Profiles acquired from t = 20 min to t = 31 min, during the initial stages of INB formation. (b) Overall profiles acquired from t = 20 min to t = 55 min.
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f3: Apparent height profiles of the fluid structure indicated by a white arrow in Fig. 2. (a) Profiles acquired from t = 20 min to t = 31 min, during the initial stages of INB formation. (b) Overall profiles acquired from t = 20 min to t = 55 min.

Mentions: The apparent height of the fluid region highlighted with a white arrow in Fig. 2 gradually increased over time (Fig. 3a). The real thickness of the fluid structures (the thin layer and the cap-shaped structure) should be larger than the apparent height due to the effect of tip-penetration depth; thus, the fluid layer in Fig. 2c,d is more than one molecule thick. After a protrusion appeared at t = 28 min, both the lateral size and the apparent height of the protrusion continued to grow until t = 37 min, after which growth mainly occurred in the vertical dimension (the lateral size remained roughly the same) (Fig. 3b). The growth behaviour of INBs after t = 37 min resembled that reported by Zhang et al. (who changed the air-supersaturation level), which Zhang et al. attributed to the pinning of the three-phase contact line31. The apparent height of the fluid region indicated with a white arrow in Fig. 2 continued to increase over time (Supplementary Fig. S4); the lateral area initially increased, but gradually decreased at later times (Supplementary Fig. S4), in contrast to the rapid reduction in the lateral size of the fluid layer evident in Fig. 1 and Supplementary Fig. S3.


Nucleation processes of nanobubbles at a solid/water interface.

Fang CK, Ko HC, Yang CW, Lu YH, Hwang IS - Sci Rep (2016)

Apparent height profiles of the fluid structure indicated by a white arrow in Fig. 2. (a) Profiles acquired from t = 20 min to t = 31 min, during the initial stages of INB formation. (b) Overall profiles acquired from t = 20 min to t = 55 min.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835695&req=5

f3: Apparent height profiles of the fluid structure indicated by a white arrow in Fig. 2. (a) Profiles acquired from t = 20 min to t = 31 min, during the initial stages of INB formation. (b) Overall profiles acquired from t = 20 min to t = 55 min.
Mentions: The apparent height of the fluid region highlighted with a white arrow in Fig. 2 gradually increased over time (Fig. 3a). The real thickness of the fluid structures (the thin layer and the cap-shaped structure) should be larger than the apparent height due to the effect of tip-penetration depth; thus, the fluid layer in Fig. 2c,d is more than one molecule thick. After a protrusion appeared at t = 28 min, both the lateral size and the apparent height of the protrusion continued to grow until t = 37 min, after which growth mainly occurred in the vertical dimension (the lateral size remained roughly the same) (Fig. 3b). The growth behaviour of INBs after t = 37 min resembled that reported by Zhang et al. (who changed the air-supersaturation level), which Zhang et al. attributed to the pinning of the three-phase contact line31. The apparent height of the fluid region indicated with a white arrow in Fig. 2 continued to increase over time (Supplementary Fig. S4); the lateral area initially increased, but gradually decreased at later times (Supplementary Fig. S4), in contrast to the rapid reduction in the lateral size of the fluid layer evident in Fig. 1 and Supplementary Fig. S3.

Bottom Line: Experimental investigations of hydrophobic/water interfaces often return controversial results, possibly due to the unknown role of gas accumulation at the interfaces.These ordered domains may be the interfacial hydrophilic gas hydrates and/or the long-sought chemical surface heterogeneities responsible for contact line pinning and contact angle hysteresis.The gradual nucleation and growth of hydrophilic ordered domains renders the original homogeneous hydrophobic/water interface more heterogeneous over time, which would have great consequence for interfacial properties that affect diverse phenomena, including interactions in water, chemical reactions, and the self-assembly and function of biological molecules.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan.

ABSTRACT
Experimental investigations of hydrophobic/water interfaces often return controversial results, possibly due to the unknown role of gas accumulation at the interfaces. Here, during advanced atomic force microscopy of the initial evolution of gas-containing structures at a highly ordered pyrolytic graphite/water interface, a fluid phase first appeared as a circular wetting layer ~0.3 nm in thickness and was later transformed into a cap-shaped nanostructure (an interfacial nanobubble). Two-dimensional ordered domains were nucleated and grew over time outside or at the perimeter of the fluid regions, eventually confining growth of the fluid regions to the vertical direction. We determined that interfacial nanobubbles and fluid layers have very similar mechanical properties, suggesting low interfacial tension with water and a liquid-like nature, explaining their high stability and their roles in boundary slip and bubble nucleation. These ordered domains may be the interfacial hydrophilic gas hydrates and/or the long-sought chemical surface heterogeneities responsible for contact line pinning and contact angle hysteresis. The gradual nucleation and growth of hydrophilic ordered domains renders the original homogeneous hydrophobic/water interface more heterogeneous over time, which would have great consequence for interfacial properties that affect diverse phenomena, including interactions in water, chemical reactions, and the self-assembly and function of biological molecules.

No MeSH data available.


Related in: MedlinePlus