Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.
Nanoscale. 2017 Nov 16;9(44):17284-17292. doi: 10.1039/c7nr06125k.
Photothermal reactions of metallic nanostructures, such as gold nanorods show appealing structural relaxations, such as bubble formation or particle modification. We have employed a pump-probe method to record the structural relaxations of a suspension of gold nanorods upon femtosecond laser excitation by pulsed X-ray scattering both with wide-angle and small-angle sensitivity. Single-pulse reactions include transient bubble formation at 20 J m and irreversible nanorod reshaping at 30 J m. Thus the window for reversible excitation is very narrow. Additionally we could map the time-domain and fluence behaviour in a wide range to characterize the relaxations comprehensively. The polarized laser pulse first selectively excites nanorods aligned with the laser electric field, but at higher fluence non-aligned rods are also transformed. At low fluence this transformation happens in the solid state, while at higher fluence the rods melt.
金属纳米结构的光热反应，如金纳米棒，表现出吸引人的结构弛豫，如气泡形成或颗粒修饰。我们采用泵浦-探测方法，通过飞秒激光激发金纳米棒悬浮液的脉冲 X 射线散射，在广角和小角灵敏度下记录结构弛豫。单脉冲反应包括在 20 J m 时瞬态气泡形成和在 30 J m 时不可逆的纳米棒重塑。因此，可逆激发的窗口非常窄。此外，我们可以在很宽的范围内绘制时域和剂量行为图，以全面表征弛豫过程。偏振激光脉冲首先选择性地激发与激光电场对齐的纳米棒，但在更高的剂量下，非对齐的纳米棒也会被转化。在低剂量下，这种转变发生在固态，而在更高的剂量下，纳米棒会熔化。
