Shi Meng, Qiu Jinbin, Feng Shangsheng, Zhang Lei, Zhao Yimin, Lu Tian Jian, Xu Feng
Bioinspired Engineering and Biomechanics Center (BEBC), MOE Key Laboratory of Biomedical Information Engineering, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, P. R. China.
Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA, 94720-1740, USA.
Small. 2021 Apr;17(17):e2007325. doi: 10.1002/smll.202007325. Epub 2021 Mar 11.
Janus particles with asymmetric crystals show great importance in optoelectronics and photocatalysis, but their synthesis usually requires complicated procedures. Here, an unexpected Janus vitrification phenomenon is observed in a droplet caused by the Leidenfrost effect at a cryogenic temperature, which is commonly regarded as symmetric. The Leidenfrost phenomenon levitates the droplet when it comes in contact with liquid nitrogen causing different cooling conditions on the droplet's top and bottom surfaces. It induces asymmetric crystallization in the droplet, forming a Janus vitrified particle with an asymmetric crystallization borderline after cooling, as further evidenced by cryotransmission electron microscopy (cryo-TEM) experiments. Theoretical analysis and experimental study indicate that the position of the asymmetric crystallization borderline is determined by the droplet radius and density, and the observation window of asymmetric crystallization borderline is determined by the chemical concentration. The finding reveals the asymmetric crystallization phenomenon in droplet vitrification for the first time, and provides a new insight for creating Janus particles through the Leidenfrost phenomenon.
具有不对称晶体的Janus颗粒在光电子学和光催化中具有重要意义，但其合成通常需要复杂的程序。在此，在低温下由莱顿弗罗斯特效应引起的液滴中观察到一种意外的Janus玻璃化现象，这种现象通常被认为是对称的。当液滴与液氮接触时，莱顿弗罗斯特现象会使液滴悬浮，导致液滴上下表面的冷却条件不同。它在液滴中诱导不对称结晶，冷却后形成具有不对称结晶边界的Janus玻璃化颗粒，低温透射电子显微镜（cryo-TEM）实验进一步证明了这一点。理论分析和实验研究表明，不对称结晶边界的位置由液滴半径和密度决定，不对称结晶边界的观察窗口由化学浓度决定。这一发现首次揭示了液滴玻璃化中的不对称结晶现象，并为通过莱顿弗罗斯特现象制备Janus颗粒提供了新的见解。
