Evolving Crystal Morphology of Potassium Chloride Controlled by Optical Trapping
Evolving Crystal Morphology of Potassium Chloride Controlled by Optical Trapping
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DOI：
10.1021/acs.jpcc.9b11651
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发表时间：
2020-03-26
影响因子：
3.7
通讯作者：
Sugiyama, Teruki
中科院分区：
文献类型：
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作者：
Cheng, An-Chieh;Masuhara, Hiroshi;Sugiyama, Teruki
用聚焦连续波近红外激光表面光学捕获技术研究了氯化钾晶体的动态形貌演化过程。在空气/溶液界面处的光学陷阱触发了结晶，然后实时观察到了晶体形态的动态变化。在晶化初期，我们观察到了针状、长方形和立方状三种不同的晶体形态。随着激光功率的增加，立方晶体的产生几率增加，特别是在线偏振的照射下。我们还发现，通过对所产生的晶体的连续照射，激光偏振相关的形貌演化。线偏振激光辐照后，KCl晶体的阶梯状形态由针状演变为长方形，最终演变为立方状，为平衡形状。同时，由于矩形晶体在旋转过程中溶解，圆偏振激光辐照只诱导其形貌由针状向矩形演化，而不是由立方体转变为立方体。由于我们的结晶方法具有时空可控性，所以有可能观察到这种独特的形态演变。从成核前光学俘获形成的致密团簇区的角度，讨论了这些有趣现象的动力学和机制。
Dynamic morphology evolution of potassium chloride (KCl) crystals was demonstrated by surface optical trapping with a focused continuous-wave near-infrared laser. Optical trapping at an air/solution interface triggered the crystallization, and then, the dynamic change in crystal morphology was observed in real time. We observed three different crystal morphologies of needle, rectangle, and cubic at the early stage of crystallization. As the laser power increases, the probability of generation of a cubic crystal increases, especially upon the irradiation with linear polarization. We also found laser polarization-dependent morphology evolution by the continuous irradiation to the generated crystals. Upon linearly polarized laser irradiation, the stepwise morphology evolves from needle to rectangle, and eventually to cubic, which is an equilibrium shape of KCl crystals. Meanwhile, circularly polarized laser irradiation only induced morphology evolution from needle to rectangle, without morphology change into cubic, because the rectangle crystal was dissolved while the crystal was rotating. It was made possible to observe such a unique morphological evolution due to the spatiotemporal controllability of our crystallization method. The dynamics and mechanism of these intriguing phenomena are discussed from the perspective of a dense cluster domain formed by optical trapping before nucleation.