Explicit and implicit modeling of nanobubbles in hydrophobic confinement

Abstract

Water at normal conditions is a fluid thermodynamically close to the liquid-vapor phase coexistence and features a large surface tension. This combination can lead to interesting capillary phenomena on microscopic scales. Explicitwater molecular dynamics (MD) computer simulations of hydrophobic solutes, for instance, give evidence of capillary evaporation on nanometer scales, i.e., the formation of nanometer-sized vapor bubbles (nanobubbles) between confining hydrophobic surfaces. This phenomenon has been exemplified for solutes with varying complexity, e.g., paraffin plates, coarse-grained homopolymers, biological and solid-state channels, and atomistically resolved proteins. It has been argued that nanobubbles strongly impact interactions in nanofluidic devices, translocation processes, and even in protein stability, function, and folding. As large-scale MD simulations are computationally expensive, the efficient multiscale modeling of nanobubbles and the prediction of their stability poses a formidable task to the 'nanophysical' community. Recently, we have presented a conceptually novel and versatile implicit solvent model, namely, the variational implicit solvent model (VISM), which is based on a geometric energy functional. As reviewed here, first solvation studies of simple hydrophobic solutes using VISM coupled with the numerical level-set scheme show promising results, and, in particular, capture nanobubble formation and its subtle competition to local energetic potentials in hydrophobic confinement.

A Deliberation on Nanobubbles at Surfaces and in Bulk

“…Simulations are already beginning to grapple with this challenge. [74] Furthermore, the nature of the nanobubble gas will be important; for example, nitrogen will be inert compared to oxygen, which may promote or interfere with biological functions.…”

Stabilization of Nanobubbles under Hydrophobic Confinement

“…This amazing property of nanobubbles has thus made them emerge as promising candidates for many applications, e.g., as high pressure nanoreactors with enhanced reaction kinetics 8 that could be employed within fuel cells without the need for expensive catalysts. Other potential applications include their use as ultrasound contrast agents, as transport for gas delivery to membranes and cells 9 which could have effects on transmembrane proteins and on membrane structures, in turn, modifying cell function and promoting biological functions. Furthermore, nanobubbles can serve as a seed for the growth of larger bubbles, responsible for decompression sickness 10 .…”

Formation of a Hydrogen Radical in Hydrogen Nanobubble Water and Its Effect on Copper Toxicity in Chlorella

“…It is also reported that NBs may provide a transport mechanism for gas delivery to a membrane and thus affect transmembrane proteins or the membrane structure. 28,29 Reducing hydrogen NBs may affect the conformation of redox-sensitive proteins on cell membranes.…”

“…Finally, it was confirmed that NBs can exist on both hydrophilic and hydrophobic surfaces. , Therefore, we speculate that NBs can provide a transport mechanism for gas transport to the cell membrane, which may affect the structure and conformation of redox-sensitive proteins, thereby affecting the intake of heavy metal pollutants. It is also reported that NBs may provide a transport mechanism for gas delivery to a membrane and thus affect transmembrane proteins or the membrane structure. , Reducing hydrogen NBs may affect the conformation of redox-sensitive proteins on cell membranes.…”