Ultra-high Density of Gas Molecules Confined in Surface Nanobubbles in Ambient Water
Ultra-high Density of Gas Molecules Confined in Surface Nanobubbles in Ambient Water
复制标题
环境水中被限制在表面纳米气泡中的超高密度气体分子
DOI：
10.1021/jacs.9b11303
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发表时间：
2020
影响因子：
15
通讯作者：
Lijuan Zhang
中科院分区：
文献类型：
--
作者：
Limin Zhou;Xingya Wang;Hyun-Joon Shin;Jian Wang;Renzhong Tai;Xuehua Zhang;Haiping Fang;Wei Xiao;Lei Wang;Chunlei Wang;Xingyu Gao;Jun Hu;Lijuan Zhang
要理解纳米尺度气泡出乎意料和令人费解的长期稳定性，关键是要探索它们的本质和内在属性。在此，我们报告了基于同步加速器的扫描透射式X射线显微镜(STXM)证据，证明高度凝聚的氧气分子被捕获为表面纳米气泡。值得注意的是，对单个纳米气泡的吸收光谱分析表明，其中的氧密度比大气压下的高1-2个数量级，并且这些气泡是在高度饱和的液体环境中发现的，估计的氧浓度比已知的平衡氧溶解度高数百倍。用分子动力学模拟方法研究了气体过饱和水中非均质衬底表面纳米气泡的稳定性。这些结果表明，限制条件下的气体分子，如纳米气泡，只要其周围的液体是过饱和的，就可以保持致密状态，而不是理想的气体状态。我们的发现应该有助于解释纳米气泡令人惊讶的长寿命，并揭示纳米尺度的气体聚集行为。
To understand the unexpected and puzzling long-term stability of nanoscale gas bubbles, it is crucial to probe their nature and intrinsic properties. We report herein synchrotron-based scanning transmission X-ray microscopy (STXM) evidence of highly condensed oxygen gas molecules trapped as surface nanobubbles. Remarkably, the analysis of absorption spectra of a single nanobubble revealed that the oxygen density inside was 1–2 orders of magnitude higher than that in atmospheric pressure, and these bubbles were found in a highly saturated liquid environment with the estimated oxygen concentration to be hundreds of times higher than the known oxygen solubility in equilibrium. Molecular dynamics simulations were performed to investigate the stability of surface nanobubbles on a heterogeneous substrate in gas-oversaturated water. These results indicated that gas molecules within confinement such as the nanobubbles could maintain a dense state instead of the ideal gas state, as long as their surrounding liquid is supersaturated. Our findings should help explain the surprisingly long lifetime of the nanobubbles and shed light on nanoscale gas aggregation behaviors.