Interfacial Nanobubbles on Atomically Flat Substrates with Different Hydrophobicities

Wang, Xingya; Zhao, Binyu; Ma, Wang-Guo; Wang, Ying; Gao, Xingyu; Tai, Renzhong; Zhou, Xingfei; Zhang, Lijuan

doi:10.1002/cphc.201402854

Cited by 29 publications

(26 citation statements)

References 40 publications

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“…from the well-established highly oriented 5 pyrolytic graphite to modified silicon wafer or glass. 11, 23,24,25,26 The only exception would be 6 carefully prepared and characterized silane layers on silicon or, as has been published previously 7 by our group, the use of self-assembled monolayers (SAMs) on ultraflat template stripped gold 8 (TSG). 27 By using binary SAMs of two thiols exposing different functional groups at their end, 9…”

Section: Introductionmentioning

confidence: 99%

AFM Study of Surface Nanobubbles on Binary Self-Assembled Monolayers on Ultraflat Gold with Identical Macroscopic Static Water Contact Angles and Different Terminal Functional Groups

et al. 2016

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All experimental findings related to surface nanobubbles, such as their pronounced stability and the striking differences of macroscopic and apparent nanoscopic contact angles, need to be addressed in any theory or model of surface nanobubbles. In this work we critically test a recent explanation of surface nanobubble stability and their consequences and contrast this with previously proposed models. In particular, we elucidated the effect of surface chemical composition of well-controlled solid-aqueous interfaces of identical roughness and defect density on the apparent nanoscopic contact angles. Expanding on a previous atomic force microscopy (AFM) study on the systematic variation of the macroscopic wettability using binary self-assembled monolayers (SAMs) on ultraflat template stripped gold (TSG), we assessed here the effect of different surface chemical composition for macroscopically identical static water contact angles. SAMs on TSG with a constant macroscopic water contact angle of 81 ± 2° were obtained by coadsorption of a methyl-terminated thiol and a second thiol with different terminal functional groups, including hydroxy, amino, and carboxylic acid groups. In addition, surface nanobubbles formed by entrainment of air on SAMs of a bromoisobutyrate-terminated thiol were analyzed by AFM. Despite the widely differing surface potentials and different functionality, such as hydrogen bond acceptor or donor, and different dipole moments and polarizability, the nanoscopic contact angles (measured through the condensed phase and corrected for AFM tip broadening effects) were found to be 145 ± 10° for all surfaces. Hence, different chemical functionalities at identical macroscopic static water contact angle do not noticeably influence the apparent nanoscopic contact angle of surface nanobubbles. This universal contact angle is in agreement with recent models that rely on contact line pinning and the equilibrium of gas outflux due to the Laplace pressure and gas influx due to gas oversaturation in the aqueous medium.

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Section: Introductionmentioning

confidence: 99%

AFM Study of Surface Nanobubbles on Binary Self-Assembled Monolayers on Ultraflat Gold with Identical Macroscopic Static Water Contact Angles and Different Terminal Functional Groups

et al. 2016

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“…surfactant, salinity, surface hydrophobicity and roughness) were also investigated. [21][22][23][24][25][26][27][28][29] Several models have been proposed to explain the remarkable stability of INBs, such as line tension, [30][31] contamination on the air/water interface, 32 and a dynamic equilibrium theory. [33][34] The presence of INBs was also reported to be an important factor influencing the interaction between hydrophobic solid surfaces in water.…”

Section: Introductionmentioning

confidence: 99%

Probing Interactions between Air Bubble and Hydrophobic Polymer Surface: Impact of Solution Salinity and Interfacial Nanobubbles

et al. 2016

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The interactions between air bubbles and hydrophobic polymer surfaces in aqueous media play important roles in many industrial and engineering processes. In this work, the interaction forces between air bubble and a model hydrophobic polymer-polystyrene (PS) in NaCl solutions (1 mM to 1000 mM) were directly measured using a bubble probe atomic force microscope (AFM) technique, and the measured forces were analyzed by a theoretical model based on Reynolds lubrication theory and augmented Young-Laplace equation including the influence of disjoining pressure. It was found that the theoretical analysis, by assuming that the PS surface was a pristine and bare polymer surface in aqueous solutions, could not fully agree with the experimental force measurements at intermedium salinity condition (i.e., 100 mM NaCl), and the discrepancy could not be described by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory even including the effects of non-DLVO interactions such as hydrophobic interaction. Atomic force microscope (AFM) imaging demonstrated that the above discrepancy was caused by the presence of interfacial nanobubbles (INBs) on the hydrophobic PS surface. The solution salinity was found to significantly affect the size and surface coverage of INBs on the PS surface, thereby influencing the surface forces. At high NaCl concentration (e.g., 500 and 1000 mM), the INB formation (and its impact on the surface interactions) and electric double layer repulsion were highly suppressed, and the bubble-PS attachment was observed attributing to their hydrophobic attraction with a decay length of ∼0.75 ± 0.05 nm. The results agree with our previous surface force measurements between two PS surfaces using a surface forces apparatus. This work provides useful insights into the interaction mechanism between air bubbles and hydrophobic polymer surfaces, as well as the influence of solution salinity and interfacial nanobubbles on the bubble-polymer interaction.

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“…One of the earliest approaches to produce surface nanobubbles is called solvent exchange, where a good solvent of gas is slowly replaced by a poor one and the resulting gas oversaturation leads to formation of nanobubbles on the immersed substrates [21,22,17,[23][24][25][26]. As adapted by several different research groups, solvent exchange has been successfully employed to produce surface nanobubbles on various substrates such as hydrophobic silicon surface, HOPG, and mica [27][28][29][30][31]. Moreover, solvent exchange is also applied to produce nanodroplets of many kinds of liquids on solid surfaces.…”

Section: Introductionmentioning

confidence: 99%

Growth dynamics of microbubbles on microcavity arrays by solvent exchange: Experiments and numerical simulations

Peng

Spandan

Verzicco

et al. 2018

Journal of Colloid and Interface Science

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Solvent exchange is a flow process to induce a transient oversaturation for forming nanobubbles or nanodroplets on solid surfaces by displacing the solution of gases or droplet liquids with a controlled flow of a poor solvent. In this work, we experimentally and numerically investigate the effect of the flow rate and other control parameters on the formation of microbubbles on hydrophobic cavity arrays during the solvent exchange process. We find that the growth rate, location, and number density of microbubbles are closely related to flow rate, solvent concentration, cavity distance, and spatial arrangement. Higher growth rates and number densities of the bubbles were obtained for faster solvent exchange flow rates. The competition of neighbouring growing bubbles for dissolved gas is greatly alleviated when the inter-cavity distance is increased from 13 μm to 40 μm. The effects of the flow rate and the cavity spacing on the bubble growth are in agreement with the observations from our three-dimensional numerical simulations. The findings reported in this work provide important insight into the formation of multiple interacting surface microbubbles under various flow conditions. The understanding may be extended to a smaller scale for the growth of surface nanobubbles during solvent exchange, which is much harder to visualize in experiments.

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Interfacial Nanobubbles on Atomically Flat Substrates with Different Hydrophobicities

Cited by 29 publications

References 40 publications

AFM Study of Surface Nanobubbles on Binary Self-Assembled Monolayers on Ultraflat Gold with Identical Macroscopic Static Water Contact Angles and Different Terminal Functional Groups

AFM Study of Surface Nanobubbles on Binary Self-Assembled Monolayers on Ultraflat Gold with Identical Macroscopic Static Water Contact Angles and Different Terminal Functional Groups

Probing Interactions between Air Bubble and Hydrophobic Polymer Surface: Impact of Solution Salinity and Interfacial Nanobubbles

Growth dynamics of microbubbles on microcavity arrays by solvent exchange: Experiments and numerical simulations

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