Giant and explosive plasmonic bubbles by delayed nucleation
Giant and explosive plasmonic bubbles by delayed nucleation
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通过延迟成核产生巨大且爆炸性的等离子体气泡
DOI：
10.1073/pnas.1805912115
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发表时间：
2018-07-24
影响因子：
11.1
通讯作者：
Lohse, Detlef
中科院分区：
文献类型：
--
作者：
Wang, Yuliang;Zaytsev, Mikhail E.;Lohse, Detlef
等离子体微泡是许多应用的中心，包括微操作/纳米操纵、生物医学诊断和治疗以及太阳能收集。控制这些微泡的动力学是在越来越多的应用中成功开发其潜力的关键。文献极大地忽略了这些微泡产生的成核和早期微秒动力学。了解这个早期阶段是至关重要的，因为它显示了最激烈的动态，是许多应用所依赖的所有后续动态的先驱和起源。当被激光照射时，浸没在水中的等离子体纳米颗粒可以非常迅速和强烈地加热，导致所谓的等离子体气泡的成核。虽然这种气泡的长期行为已经得到了很好的研究，但在这里，使用超高速成像，我们揭示了这些气泡的成核和早期生命阶段。在从照明开始的一段延迟时间之后，一个巨大的气泡爆炸性地增长，并在200 μs内再次崩溃（气泡生命阶段1）。最大气泡体积Vmax随着激光功率的减小而显著增大，导致总倾倒能量E减小。这种倾倒的能量显示出与Vmax的普遍线性比例关系，而与周围水的气体浓度无关。这一发现支持了最初的巨气泡是一个纯粹的汽泡。相比之下，延迟时间确实取决于水的气体浓度，因为水中的气穴促进更早的蒸汽气泡成核，这导致更小的延迟时间和更低的气泡成核温度。在最初的巨大气泡崩溃之后，首先，从剩余的气体核中形成小得多的振荡气泡（气泡生命阶段2）。随后，已知的蒸发占主导地位的生长阶段接管，并且气泡稳定（寿命阶段3）。在最终寿命阶段4中，由于周围环境的加热，气泡通过气体排出而缓慢生长。我们的研究结果的爆炸性增长和崩溃的早期生命阶段的等离子体汽泡有很强的轴承可能的应用程序，这样的气泡。
Significance Plasmonic microbubbles are at the center of numerous applications, including micromanipulation/nanomanipulation, biomedical diagnosis and therapy, and solar energy harvesting. Controlling the dynamics of these microbubbles is key to successfully exploiting their potential in the growing number of applications. Literature has vastly overlooked the nucleation and early microsecond dynamics by which these microbubbles arise. It is of utmost importance to understand this early phase, as it displays the most violent dynamics and is the precursor and origin of all subsequent dynamics, on which the many applications rely. When illuminated by a laser, plasmonic nanoparticles immersed in water can very quickly and strongly heat up, leading to the nucleation of so-called plasmonic vapor bubbles. While the long-time behavior of such bubbles has been well-studied, here, using ultrahigh-speed imaging, we reveal the nucleation and early life phase of these bubbles. After some delay time from the beginning of the illumination, a giant bubble explosively grows, and collapses again within 200 μs (bubble life phase 1). The maximal bubble volume Vmax remarkably increases with decreasing laser power, leading to less total dumped energy E. This dumped energy shows a universal linear scaling relation with Vmax, irrespective of the gas concentration of the surrounding water. This finding supports that the initial giant bubble is a pure vapor bubble. In contrast, the delay time does depend on the gas concentration of the water, as gas pockets in the water facilitate an earlier vapor bubble nucleation, which leads to smaller delay times and lower bubble nucleation temperatures. After the collapse of the initial giant bubbles, first, much smaller oscillating bubbles form out of the remaining gas nuclei (bubble life phase 2). Subsequently, the known vaporization dominated growth phase takes over, and the bubble stabilizes (life phase 3). In the final life phase 4, the bubble slowly grows by gas expelling due to heating of the surrounding. Our findings on the explosive growth and collapse during the early life phase of a plasmonic vapor bubble have strong bearings on possible applications of such bubbles.