Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University , Hsinchu 30010, Taiwan.
Langmuir. 2017 Jan 24;33(3):755-763. doi: 10.1021/acs.langmuir.6b03780. Epub 2017 Jan 10.
Laser trapping in chemistry covers various studies ranging from single molecules, nanoparticles, and quantum dots to crystallization and liquid-liquid phase separation of amino acids. In this work, a supramolecular assembly of azobenzene-based biscalix[4]arene is generated in ethyl acetate using laser trapping; its nucleation and growth are elucidated. No trapping behavior was observed when a 1064 nm laser beam was focused inside of the solution; however, interesting assembling phenomena were induced when it was shined at the air/solution interface. A single disk having two layers was first prepared at the focal point of ∼1 μm and then expanded to the size of a few tens of micrometers, although no optical force was exerted outside of the focal volume. Upon switching the trapping laser off, needles were generated at the outer layer of the assembly, giving a stable sea urchin-like morphology to the generated assembly. At a 30-50% dilution of the initial solution in ethyl acetate, a mushroom-like morphology was also observed. Laser trapping-induced assembly of azobenzene-based biscalix[4]arene was quite different from the sharp-ellipsoidal aggregates obtained by the spontaneous evaporation of the solution. These trapping phenomena were specifically observed for biscalix[4]arene in the trans conformation of azo-benzene moiety but not for the cis-form, suggesting that the laser trapping of this azobenzene-based biscalix[4]arene is photocontrollable. Dynamics and mechanism of the supramolecular assembling are considered, referring to laser trapping-induced nucleation and liquid-liquid phase separation of amino acids.
激光捕获在化学领域涵盖了各种研究，包括从单个分子、纳米粒子和量子点到氨基酸的结晶和液-液相分离。在这项工作中，通过激光捕获在乙酸乙酯中生成了基于偶氮苯的双杯[4]芳烃的超分子组装体，并阐明了其成核和生长过程。当聚焦在溶液内部的 1064nm 激光束时，没有观察到捕获行为；然而，当它照射到空气/溶液界面时，会引起有趣的组装现象。首先在约 1μm 的焦点处制备了具有两层的单个圆盘，然后扩展到几十微米的尺寸，尽管在焦体积之外没有施加光学力。当关闭捕获激光时，组装体的外层会产生针状结构，从而使生成的组装体具有稳定的海胆状形态。在初始溶液在乙酸乙酯中的稀释度为 30-50%的情况下，也观察到了蘑菇状形态。基于偶氮苯的双杯[4]芳烃的激光捕获诱导组装与通过溶液自发蒸发获得的尖锐椭球聚集明显不同。这些捕获现象仅在偶氮苯部分处于反式构象的双杯[4]芳烃中观察到，而在顺式构象中则没有观察到，这表明这种基于偶氮苯的双杯[4]芳烃的激光捕获是光可控的。考虑到激光捕获诱导的氨基酸成核和液-液相分离，讨论了超分子组装的动力学和机制。
