Hu Kadi, Luo Liang, Sun Xiaoming, Li Hui
Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemistry Technology Beijing 100029 PR China
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology Beijing 100029 PR China.
Nanoscale Adv. 2022 May 24;4(13):2893-2901. doi: 10.1039/d2na00009a. eCollection 2022 Jun 28.
The morphology of interfacial nanobubbles (INBs) is a crucial but controversial topic in nanobubble research. We carried out atomistic molecular dynamics (MD) simulations to comprehensively study the morphology of INBs controlled by several determinant factors, including gas species, surface wettability, and bubble size. The simulations show that H, O and N can all form stable INBs, with the contact angles (CAs, on the liquid side) following the order CA(H) < CA(N) < CA(O), while CO prefers to form a gas film (pancake) structure on the substrate. The CA of INBs demonstrates a linear relation with the strength of interfacial interaction; however, a limited bubble CA of ∼25° is found on superhydrophilic surfaces. The high gas density and high internal pressure of the INBs are further confirmed, accompanied by strong interfacial gas enrichment (IGE) behavior. The morphology study of differently sized INBs shows that the internal density of the gas is drastically decreased with the bubble size at the initial stage of bubble nucleation, while the CA remains almost constant. Based on the simulation results, a modified Young's equation is presented for describing the extraordinary morphology of INBs.
界面纳米气泡（INBs）的形态是纳米气泡研究中一个关键但颇具争议的话题。我们进行了原子分子动力学（MD）模拟，以全面研究由多种决定性因素控制的INBs形态，这些因素包括气体种类、表面润湿性和气泡大小。模拟结果表明，H、O和N都能形成稳定的INBs，其接触角（液体侧）顺序为CA(H) < CA(N) < CA(O)，而CO更倾向于在基底上形成气膜（薄饼）结构。INBs的接触角与界面相互作用强度呈线性关系；然而，在超亲水表面上发现有限的气泡接触角约为25°。进一步证实了INBs的高气密度和高内部压力，同时伴有强烈的界面气体富集（IGE）行为。不同大小INBs的形态研究表明，在气泡成核的初始阶段，气体的内部密度随着气泡大小急剧降低，而接触角几乎保持不变。基于模拟结果，提出了一个修正的杨氏方程来描述INBs的特殊形态。
