Nanoparticle–Fluid Interactions at Ultrahigh Acoustic Vibration Frequencies Studied by Femtosecond Time-Resolved Microscopy
Nanoparticle–Fluid Interactions at Ultrahigh Acoustic Vibration Frequencies Studied by Femtosecond Time-Resolved Microscopy
复制标题
通过飞秒时间分辨显微镜研究超高声振动频率下的纳米颗粒与流体相互作用
DOI：
10.1021/acsnano.0c09840
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发表时间：
2021
期刊：
影响因子：
17.1
通讯作者：
Wang, Guo Ping
中科院分区：
文献类型：
--
作者：
Yu, Kuai;Yang, Yang;Wang, Junzhong;Hartland, Gregory V.;Wang, Guo Ping
液体的粘性和粘弹性性质是决定流变现象的重要参数。机械谐振器具有极高的振动频率，与简单液体相互作用，具有从质量传感到生物力学的广泛应用。然而，由于缺乏对流体粘弹性的了解，极大地阻碍了机械谐振器的应用。本文利用具有大品质因子的Au纳米板的高频声振动，通过时间分辨的泵浦-探测显微镜实验来探测流体性质(水、甘油及其混合物)。对于水，可以清楚地观察到粘性减振，而无粘性效应是以前才检测到的。在水中加入甘油会增加流体的粘度，并导致体系中的粘弹性反应。实验结果与纳米板呼吸模式在液体中衰减的连续介质力学模型符合得很好，证实了实验观察到的粘弹性效应。除了纳米平板的呼吸模式外，在实验中还观察到了布里渊振荡。对布里渊振荡频率的分析还表明，在高粘度的溶剂中存在粘弹性效应。液体中粘性阻尼的检测和分析不仅对了解液体的能量耗散机理和提供液体的机械松弛时间具有重要意义，而且对于开发纳米机械谐振器在流体环境中的应用也具有重要意义。
Liquid viscous and viscoelastic properties are very important parameters in determining rheological phenomena. Mechanical resonators with extremely high vibrational frequencies interacting with simple liquids present a wide range of applications from mass sensing to biomechanics. However, a lack of understanding of fluid viscoelasticity greatly hinders the utilization of mechanical resonators. In this paper, the high frequency acoustic vibrations of Au nanoplates with large quality factors were used to probe fluid properties (water, glycerol, and their mixtures) through time-resolved pump–probe microscopy experiments. For water, viscous damping was clearly observed, where an inviscid effect was only detected previously. Adding glycerol to the water increases the fluid viscosity and leads to a bulk viscoelastic response in the system. The experimental results are in excellent agreement with a continuum mechanics model for the damping of nanoplate breathing modes in liquids, confirming the experimental observation of viscoelastic effects. In addition to the breathing modes of the nanoplates, Brillouin oscillations are observed in the experiments. Analysis of the frequency of the Brillouin oscillations also shows the presence of viscoelastic effects in the high-viscosity solvents. The detection and analysis of viscous damping in liquids is important not only for understanding the energy dissipation mechanisms and providing the mechanical relaxation times of the liquids but also for developing applications of nanomechanical resonators for fluid environments.