Laser-driven phase transitions in aqueous colloidal gold nanoparticles under high pressure: picosecond pump-probe study
Laser-driven phase transitions in aqueous colloidal gold nanoparticles under high pressure: picosecond pump-probe study
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DOI：
10.1039/c5cp07395b
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发表时间：
2016-02-14
影响因子：
3.3
通讯作者：
Miyasaka, Hiroshi
中科院分区：
文献类型：
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作者：
Hashimoto, Shuichi;Katayama, Tetsuro;Miyasaka, Hiroshi
利用泵浦-探测瞬态消光光谱技术研究了60 MPa高压下355 nm皮秒激光对直径为60 nm的金纳米粒子水溶液的热诱导现象。动力学光谱表明，超临界层周围的金纳米粒子成核的寿命约为1 ns，在其动态膨胀和衰减的能量密度为19.6 mJ cm（-2）。此外，在死后的透射电子显微照片中，我们观察到一些碎片，一小部分尺寸减小的核心，并在60次射击后在完整的颗粒中爆发出颗粒，这表明在激光照射下发生了蒸发。粒子温度的计算表明，蒸发开始于在低于金的沸点的温度下由超临界层包围的液滴AuNP。通过施加高压，我们获得了蒸发事件的清晰图像，这在环境压力下是不可能的，因为气泡的形成导致颗粒温度不受控制地上升。在这项研究中，我们揭示了超临界层的关键作用，在高压下形成的AuNP在激光诱导蒸发。
Pump-probe transient extinction spectroscopy was used to analyze 355 nm picosecond laser heating-induced phenomena in 60 nm-diameter aqueous gold nanoparticles (AuNPs) under a high pressure of 60 MPa. Kinetic spectroscopy revealed that a supercritical layer surrounding the AuNP nucleated with a lifetime of approximately 1 ns during its dynamic expansion and decay for a fluence of 19.6 mJ cm(-2). Moreover, in the post-mortem transmission electron micrographs we observed a number of fragments, a small percentage of size-reduced cores, and erupted particles among the intact particles after 60 shots, suggesting that evaporation occurred under laser illumination. The particle temperature calculation indicated that evaporation begins with a liquid droplet AuNP surrounded by a supercritical layer at temperatures below the boiling point of gold. By applying high pressure, we obtained a clear picture of the evaporation event, which was not possible at ambient pressure because bubble formation caused particle temperatures to rise uncontrollably. In this study, we shed light on the critical role of the supercritical layer formed around the AuNP under high pressure during laser-induced evaporation.