Heterogeneous bubble nucleation is one of the most fundamental interfacial processes ranging from nature to technology. There is excellent evidence that surface topology is important in directing heterogeneous nucleation; however, deep understanding of the energetics by which nanoscale architectures promote nucleation is still challenging. Herein, we report a direct and quantitative measurement of single-bubble nucleation on a single silica nanoparticle within a microsized droplet using scanning electrochemical cell microscopy. Local gas concentration at nucleation is determined from finite element simulation at the corresponding faradaic current of the peak-featured voltammogram. It is demonstrated that the criteria gas concentration for nucleation first drops and then rises with increasing nanoparticle radius. An optimum nanoparticle radius around 10 nm prominently expedites the nucleation by facilitating the special topological nanoconfinements that consequently catalyze the nucleation. Moreover, the experimental result is corroborated by our theoretical calculations of free energy change based on the classic nucleation theory. This study offers insights into the impact of surface topology on heterogenous nucleation that have not been previously observed.

中文翻译：

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表面拓扑介导的单异质气泡成核的直接测量

异质气泡成核是从自然到技术的最基本的界面过程之一。有极好的证据表明表面拓扑结构在指导异质成核中很重要；然而，深入了解纳米级结构促进成核的能量学仍然具有挑战性。在此，我们报告了使用扫描电化学电池显微镜对微型液滴内单个二氧化硅纳米颗粒上的单气泡成核的直接和定量测量。成核时的局部气体浓度由峰值特征伏安图的相应法拉第电流下的有限元模拟确定。结果表明，随着纳米粒子半径的增加，成核的标准气体浓度先下降后上升。10 nm 左右的最佳纳米粒子半径通过促进特殊的拓扑纳米限制显着加快成核，从而催化成核。此外，我们基于经典成核理论对自由能变化的理论计算证实了实验结果。这项研究提供了关于表面拓扑结构对以前未观察到的异质成核影响的见解。