School of Chemistry, WestCHEM, University of Glasgow, Glasgow, UK.
Nat Chem. 2018 May;10(5):506-510. doi: 10.1038/s41557-018-0009-8. Epub 2018 Mar 5.
Control over the nucleation of new phases is highly desirable but elusive. Even though there is a long history of crystallization engineering by varying physicochemical parameters, controlling which polymorph crystallizes or whether a molecule crystallizes or forms an amorphous precipitate is still a poorly understood practice. Although there are now numerous examples of control using laser-induced nucleation, the absence of physical understanding is preventing progress. Here we show that the proximity of a liquid-liquid critical point or the corresponding binodal line can be used by a laser-tweezing potential to induce concentration gradients. A simple theoretical model shows that the stored electromagnetic energy of the laser beam produces a free-energy potential that forces phase separation or triggers the nucleation of a new phase. Experiments in a liquid mixture using a low-power laser diode confirm the effect. Phase separation and nucleation using a laser-tweezing potential explains the physics behind non-photochemical laser-induced nucleation and suggests new ways of manipulating matter.
控制新相的成核是非常理想的，但也是难以实现的。尽管通过改变物理化学参数来进行结晶工程已有很长的历史，但控制哪种多晶型结晶、分子结晶还是形成无定形沉淀仍然是一个理解不深的实践。尽管现在有许多使用激光诱导成核来控制的例子，但由于缺乏物理理解，进展受到了阻碍。在这里，我们表明，激光夹持势可以利用液-液相变临界点或相应的双节线来诱导浓度梯度。一个简单的理论模型表明，激光束存储的电磁能产生自由能势，迫使相分离或引发新相的成核。在使用低功率激光二极管的液体混合物中的实验证实了这一效果。使用激光夹持势的相分离和成核解释了非光化学激光诱导成核背后的物理原理，并为操控物质提供了新的方法。
