Lehmkühler Felix, Valerio Joana, Sheyfer Dina, Roseker Wojciech, Schroer Martin A, Fischer Birgit, Tono Kensuke, Yabashi Makina, Ishikawa Tetsuya, Grübel Gerhard
Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22607 Hamburg, Germany.
The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany.
IUCrJ. 2018 Oct 19;5(Pt 6):801-807. doi: 10.1107/S2052252518013696. eCollection 2018 Nov 1.
The application of X-ray photon correlation spectroscopy (XPCS) at free-electron laser (FEL) facilities enables, for the first time, the study of dynamics on a (sub-)nanometre scale in an unreached time range between femtoseconds and seconds. For soft-matter materials, radiation damage is a major limitation when going beyond single-shot applications. Here, an XPCS study is presented at a hard X-ray FEL on radiation-sensitive polymeric poly(-isopropylacrylamide) (PNIPAM) nanoparticles. The dynamics of aqueous suspensions of densely packed silica-PNIPAM core-shell particles and a PNIPAM nanogel below the radiation-damage threshold are determined. The XPCS data indicate non-diffusive behaviour, suggesting ballistic and stress-dominated heterogeneous particle motions. These results demonstrate the feasibility of XPCS experiments on radiation-sensitive soft-matter materials at FEL sources and pave the way for future applications at MHz repetition rates as well as ultrafast modes using split-pulse devices.
在自由电子激光（FEL）设施中应用X射线光子相关光谱（XPCS），首次能够在飞秒到秒之间尚未达到的时间范围内，对（亚）纳米尺度的动力学进行研究。对于软物质材料，在单次应用之外，辐射损伤是一个主要限制。本文展示了在硬X射线自由电子激光上对辐射敏感的聚合物聚（N-异丙基丙烯酰胺）（PNIPAM）纳米颗粒进行的XPCS研究。确定了紧密堆积的二氧化硅-PNIPAM核壳颗粒和低于辐射损伤阈值的PNIPAM纳米凝胶的水悬浮液的动力学。XPCS数据表明存在非扩散行为，这表明存在弹道和应力主导的异质颗粒运动。这些结果证明了在FEL源上对辐射敏感的软物质材料进行XPCS实验的可行性，并为未来以兆赫兹重复率以及使用分脉冲装置的超快模式的应用铺平了道路。
