Liu Shasha, Li Haoran, Fang Susu, Xu Weigao, Hu Wenbing, Wang Wei
State Key Laboratory of Analytical Chemistry for Life Science, Chemistry and Biomedicine Innovation Center (ChemBIC), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
J Am Chem Soc. 2023 Feb 10. doi: 10.1021/jacs.2c10763.
The Leidenfrost effect describes a fascinating phenomenon in which a liquid droplet, when deposited onto a very hot substrate, will levitate on its own vapor layer and undergo frictionless movements. Driven by the significant implications for heat transfer engineering and drag reduction, intensive efforts have been made to understand, manipulate, and utilize the Leidenfrost effect on macrosized objects with a typical size of millimeters. The Leidenfrost effect of nanosized objects, however, remains unexplored. Herein, we report on an unprecedented Leidenfrost effect of single nanosized sulfur particles at room temperature. It was discovered when advanced dark-field optical microscopy was employed to monitor the dynamic sublimation process of single sulfur nanoparticles sitting on a flat substrate. Despite the phenomenological similarity, including the vapor-cushion-induced levitation and the extended lifetime, the Leidenfrost effect at the nanoscale exhibited two extraordinary features that were obviously distinct from its macroscopic counterpart. First, there was a critical size below which single sulfur nanoparticles began to levitate. Second, levitation occurred in the absence of the temperature difference between the nanoparticle and the substrate, which was barely possible for macroscopic objects and underscored the value of bridging the gap connecting the Leidenfrost effect and nanoscience. The sublimation-triggered spontaneous takeoff of single sulfur nanoparticles shed new light on its further applications, such as nanoflight.
当液滴沉积在非常热的基底上时，它会在自身的蒸汽层上悬浮并进行无摩擦运动。受传热工程和减阻方面重大意义的驱动，人们已经做出了大量努力来理解、操控和利用毫米级典型尺寸的宏观物体上的莱顿弗罗斯特效应。然而，纳米级物体的莱顿弗罗斯特效应仍未被探索。在此，我们报道了室温下单纳米级硫颗粒前所未有的莱顿弗罗斯特效应。这是在采用先进的暗场光学显微镜监测位于平坦基底上的单个硫纳米颗粒的动态升华过程时发现的。尽管在现象学上存在相似性，包括蒸汽垫引起的悬浮和延长的寿命，但纳米尺度的莱顿弗罗斯特效应表现出两个与宏观对应物明显不同的非凡特征。首先，存在一个临界尺寸，低于该尺寸单个硫纳米颗粒开始悬浮。其次，悬浮发生在纳米颗粒与基底之间不存在温差的情况下，这对于宏观物体来说几乎是不可能的，突出了弥合莱顿弗罗斯特效应与纳米科学之间差距的价值。单个硫纳米颗粒由升华引发的自发起飞为其进一步应用，如纳米飞行，提供了新的思路。
