Total-Internal-Reflection-Fluorescence Microscopy for the Study of Nanobubble Dynamics

Chan, Chon U; Ohl, Claus‐Dieter

doi:10.1103/physrevlett.109.174501

Cited by 180 publications

(169 citation statements)

References 17 publications

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“…As the pressure of the liquid is lowered, the vapor phase will bulge out from the entrance of the nanopores. However, if the remainder of the surface is solvophilic, these incipient surface nanobubbles [3][4][5][6][7][8] are pinned at the perimeter of the nanopore [9][10][11]. The radius of curvature of the metastable nanobubble is, as is shown here, the same as (or very close to) the one of the critical nucleus in homogeneous nucleation.…”

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What experiments on pinned nanobubbles can tell about the critical nucleus for bubble nucleation

et al. 2017

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Abstract. The process of homogeneous bubble nucleation is almost impossible to probe experimentally, except near the critical point or for liquids under large negative tension. Elsewhere in the phase diagram, the bubble nucleation barrier is so high as to be effectively insurmountable. Consequently, there is a severe lack of experimental studies of homogenous bubble nucleation under conditions of practical importance (e.g., cavitation). Here we use a simple geometric relation to show that we can obtain information about the homogeneous nucleation process from Molecular Dynamics studies of bubble formation in solvophobic nanopores on a solid surface. The free energy of pinned nanobubbles has two extrema as a function of volume: one state corresponds to a free-energy maximum ("the critical nucleus"), the other corresponds to a free-energy minimum (the metastable, pinned nanobubble). Provided that the surface tension does not depend on nanobubble curvature, the radius of the curvature of the metastable surface nanobubble is independent of the radius of the pore and is equal to the radius of the critical nucleus in homogenous bubble nucleation. This observation opens the way to probe the parameters that determine homogeneous bubble nucleation under experimentally accessible conditions, e.g. with AFM studies of metastable nanobubbles. Our theoretical analysis also indicates that a surface with pores of different sizes can be used to determine the curvature corrections to the surface tension. Our conclusions are not limited to bubble nucleation but suggest that a similar approach could be used to probe the structure of critical nuclei in crystal nucleation.Bubble nucleation is a very common process but the observation of truly homogenous bubble nucleation is very rare [1]. The reason is that the free-energy barrier for homogenous bubble nucleation tends to be very high (order 10 3 -10 4 eV), except near the critical point (typical T > 0.9T c ) where the surface tension is very low, or under conditions of extreme under-pressure [2]. For this reason, bubble nucleation under less extreme circumstances (e.g., bubble formation in boiling water) is always dominated by heterogeneous nucleation. The rate of heterogeneous nucleation is normally extremely sensitive to the properties of the surface, in particular to the value of the solid-liquid and solid-vapor surface free energies. Hence, normally, heterogeneous bubble nucleation does not provide direct information about the homogenous nucleation process.Supplementary material in the form of a .pdf file available from the Journal web page at http://dx.doi.org/10.1140/epje/i2017-11604-7 a e-mail: df246@cam.ac.uk b e-mail: jd489@cam.ac.uk c e-mail: zhangxr@mail.buct.edu.cnThe situation is very different in the case of welldefined hydrophobic (or, more generally, "solvophobic") nanopores in a hydrophilic ("solvophilic") surface. Inside these pores, vapor may nucleate easily, sometimes even at a pressure where the bulk liquid is still thermodynamically stable. As the pressure of t...

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What experiments on pinned nanobubbles can tell about the critical nucleus for bubble nucleation

et al. 2017

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“…There have been intensive efforts to characterize the nanobubbles in liquid phase [3][4][5][6][7][8][9][10] , which includes ion conductance measurement through a solid-state nanopore 11 , topographic imaging by atomic force microscopy (AFM) 12 and direct visualization by optical methods 13,14 . None of these, however, is capable of imaging the liquid-phase nanobubbles in real time with sub-10 nm resolution.…”

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Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells

et al. 2015

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Formation, evolution and vanishing of bubbles are common phenomena in nature, which can be easily observed in boiling or falling water, carbonated drinks, gas-forming electrochemical reactions and so on. However, the morphology and the growth dynamics of the bubbles at nanoscale have not been fully investigated owing to the lack of proper imaging tools that can visualize nanoscale objects in the liquid phase. Here, we demonstrate for the first time that the nanobubbles in water encapsulated by graphene membrane can be visualized by in-situ ultra-high vacuum transmission electron microscopy. Our microscopic results indicate two distinct growth mechanisms of merging nanobubbles and the existence of a critical radius of nanobubbles that determines the unusually long stability of nanobubbles. Interestingly, the gas transport through ultrathin water membranes at nanobubble interface is free from dissolution, which is clearly different from conventional gas transport that includes condensation, transmission and evaporation.

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“…Since their existence was first detected at the solid-water interface by atomic force microscopy (AFM) 1 twenty years ago, nanobubbles (or nanopancakes) have been produced via various formation procedures: solvent-exchange [2][3][4] , substrate heating 5,6 and electrical chemical formation 7,8 as imaged or detected by AFM [9][10][11] and recently by optical microscopy visualization 12,13 . The interfacial nanobubbles exhibit a number of peculiar properties compared to macro or micro sized bubbles, including unusually large contact angle values on the liquid side (about 150 degrees) and longer lifetimes (hours to days) than expected 10,11,14 .…”

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confidence: 99%

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

2013

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Interfacial gas enrichment (IGE) covering the entire area of hydrophobic solid-water interface has recently been detected by atomic force microscopy (AFM) and hypothesized to be responsible for the unexpected stability and anomalous contact angle of gaseous nanobubbles, and the significant change from DLVO to non-DLVO forces. In this paper, we provide further proof of the existence of IGE in the form of a dense gas layer (DGL) by molecular dynamic simulation.Nitrogen gas adsorption at the water-graphite interface is investigated using molecular dynamic simulation at 300 K and 1 atm normal pressure. The results show that a DGL with a density equivalent to a gas at pressure of 500 atm is formed and equilibrated with a normal pressure of 1 atm. By varying the number of gas molecules in the system, we observe several types of dense gas domains: aggregates, cylindrical cap gas domains and DGLs. Spherical cap gas domains form during the simulation but are unstable and always revert to another type of the gas domains.Furthermore, the calculated surface potential of the DGL-water interface, -17.5 mV, is significantly closer to 0 than the surface potential, -65 mV, of normal gas bubble-water interface. This result supports our previously stated hypothesis that the change in surface potential causes the switch from repulsion to attraction for an AFM tip when the graphite surface is covered by an IGE layer. The change in surface potential comes from the structure change of water molecules at the DGL-water interface as compared with the normal gas-water interface. In addition, the contact angle of the cylindrical cap high density nitrogen gas domains is 141degrees. This contact angle is far greater 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 than 85 degrees observed for water on graphite at ambient conditions and much closer to the 150 degrees contact angle observed for nanobubbles in experiments.

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Total-Internal-Reflection-Fluorescence Microscopy for the Study of Nanobubble Dynamics

Cited by 180 publications

References 17 publications

What experiments on pinned nanobubbles can tell about the critical nucleus for bubble nucleation

What experiments on pinned nanobubbles can tell about the critical nucleus for bubble nucleation

Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells

Origin of Interfacial Nanoscopic Gaseous Domains and Formation of Dense Gas Layer at Hydrophobic Solid–Water Interface

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