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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

Topographic images of the formation of gas-containing structures at a HOPG/water interface acquired with FM-AFM.Time points are relative to the time of water deposition (t = 0). Scale bar, 400 nm. Numbered regions in (a) exhibit a circular, thin layer covering the HOPG substrate that changed in morphology over time. The numbers in panel (a) are not shown in the other panels. (b) A higher-resolution image acquired inside the dashed box in (a) at a later time. The height profile measured along a white dashed line is shown in Supplementary Fig. S1a. (c) A high-resolution image of bright speckles (inside the dashed box in (b) at a later time), consisting of domains of a row-like pattern with three orientations (arrows) that are parallel to the orientations of the HOPG substrate. The domains with approximately horizontal row orientation (the fast scan direction) cannot be clearly resolved. A cap-shaped structure appeared in Region 4 in (e) and exhibited growth in both the vertical and lateral dimensions (f–h). The height profiles along a white dashed line across the INB from (e–h) are depicted in Supplementary Fig. S1b.
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f1: Topographic images of the formation of gas-containing structures at a HOPG/water interface acquired with FM-AFM.Time points are relative to the time of water deposition (t = 0). Scale bar, 400 nm. Numbered regions in (a) exhibit a circular, thin layer covering the HOPG substrate that changed in morphology over time. The numbers in panel (a) are not shown in the other panels. (b) A higher-resolution image acquired inside the dashed box in (a) at a later time. The height profile measured along a white dashed line is shown in Supplementary Fig. S1a. (c) A high-resolution image of bright speckles (inside the dashed box in (b) at a later time), consisting of domains of a row-like pattern with three orientations (arrows) that are parallel to the orientations of the HOPG substrate. The domains with approximately horizontal row orientation (the fast scan direction) cannot be clearly resolved. A cap-shaped structure appeared in Region 4 in (e) and exhibited growth in both the vertical and lateral dimensions (f–h). The height profiles along a white dashed line across the INB from (e–h) are depicted in Supplementary Fig. S1b.

Mentions: Figure 1 shows an example of our observations after chilled water (see Methods) was deposited onto a freshly cleaved HOPG surface. Several regions, several of which are numbered in Fig. 1a, exhibited a thin circular layer covering the HOPG substrate. Notice that several circular layers had a diameter as large as ~1 μm, and some had edges bounded by defects such as substrate step edges. The height of the circular layer was 0.3–0.4 nm (Supplementary Fig. S1a). In addition, bright speckles were scattered at the interface outside the circular layered regions (Fig. 1a). Higher-resolution images showed that the speckles were small domains with an ordered row-like structure (Fig. 1b,c) that increased in coverage of the interface over time (Fig. 1d–h). This structure and its nucleation and growth behaviours resemble the ordered pattern reported in our earlier studies of the HOPG/water interface using pre-degassed water under air or nitrogen25262728.


Nucleation processes of nanobubbles at a solid/water interface.

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

Topographic images of the formation of gas-containing structures at a HOPG/water interface acquired with FM-AFM.Time points are relative to the time of water deposition (t = 0). Scale bar, 400 nm. Numbered regions in (a) exhibit a circular, thin layer covering the HOPG substrate that changed in morphology over time. The numbers in panel (a) are not shown in the other panels. (b) A higher-resolution image acquired inside the dashed box in (a) at a later time. The height profile measured along a white dashed line is shown in Supplementary Fig. S1a. (c) A high-resolution image of bright speckles (inside the dashed box in (b) at a later time), consisting of domains of a row-like pattern with three orientations (arrows) that are parallel to the orientations of the HOPG substrate. The domains with approximately horizontal row orientation (the fast scan direction) cannot be clearly resolved. A cap-shaped structure appeared in Region 4 in (e) and exhibited growth in both the vertical and lateral dimensions (f–h). The height profiles along a white dashed line across the INB from (e–h) are depicted in Supplementary Fig. S1b.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Topographic images of the formation of gas-containing structures at a HOPG/water interface acquired with FM-AFM.Time points are relative to the time of water deposition (t = 0). Scale bar, 400 nm. Numbered regions in (a) exhibit a circular, thin layer covering the HOPG substrate that changed in morphology over time. The numbers in panel (a) are not shown in the other panels. (b) A higher-resolution image acquired inside the dashed box in (a) at a later time. The height profile measured along a white dashed line is shown in Supplementary Fig. S1a. (c) A high-resolution image of bright speckles (inside the dashed box in (b) at a later time), consisting of domains of a row-like pattern with three orientations (arrows) that are parallel to the orientations of the HOPG substrate. The domains with approximately horizontal row orientation (the fast scan direction) cannot be clearly resolved. A cap-shaped structure appeared in Region 4 in (e) and exhibited growth in both the vertical and lateral dimensions (f–h). The height profiles along a white dashed line across the INB from (e–h) are depicted in Supplementary Fig. S1b.
Mentions: Figure 1 shows an example of our observations after chilled water (see Methods) was deposited onto a freshly cleaved HOPG surface. Several regions, several of which are numbered in Fig. 1a, exhibited a thin circular layer covering the HOPG substrate. Notice that several circular layers had a diameter as large as ~1 μm, and some had edges bounded by defects such as substrate step edges. The height of the circular layer was 0.3–0.4 nm (Supplementary Fig. S1a). In addition, bright speckles were scattered at the interface outside the circular layered regions (Fig. 1a). Higher-resolution images showed that the speckles were small domains with an ordered row-like structure (Fig. 1b,c) that increased in coverage of the interface over time (Fig. 1d–h). This structure and its nucleation and growth behaviours resemble the ordered pattern reported in our earlier studies of the HOPG/water interface using pre-degassed water under air or nitrogen25262728.

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