When the surface of water is curved at nanoscale as a bubble, droplet and meniscus, its surface tension is expected to be smaller than that of planar interface, which still awaits experimental studies. Here, we report static and dynamic force spectroscopy that measures the capillary force of a single nanoscale water meniscus at constant curvature condition. Based on the Young-Laplace equation, the results are used to obtain the effective surface tension (ST) of the meniscus, which decreases to less than 20% of the bulk value at the radius-of-curvature (ROC) below 25 nm, while indicating the bulk behaviour above ~130 nm ROC. Interestingly, such a possibility provides a qualitative resolution of the unsettled discrepancies between experiments and theories in the thermodynamic activation processes for the mentioned three types of nano-curvatured water. Our results may not only lead to development of microscopic theories of ST as well as further experimental investigations, but also help better understanding of the ST-induced nanoscale dynamics such as cluster growth or protein folding, and the ST-controlled design of nano-biomaterials using the nano-meniscus.

中文翻译：

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稳态水纳米弯月面的粘附力测量：纳米级的有效表面张力。


当水表面以气泡、水滴和弯月面的形式进行纳米级弯曲时，其表面张力预计将小于平面界面的表面张力，这仍有待实验研究。在这里，我们报告了静态和动态力光谱，可测量恒定曲率条件下单个纳米级水弯月面的毛细管力。基于Young-Laplace方程，该结果用于获得弯液面的有效表面张力（ST），在曲率半径（ROC）低于25 nm时，该表面张力降低至体积值的20％以下，同时指示高于 ~130 nm ROC 的体行为。有趣的是，这种可能性为上​​述三种纳米曲率水的热力学活化过程中实验和理论之间尚未解决的差异提供了定性的解决方案。我们的结果不仅可能促进 ST 微观理论的发展以及进一步的实验研究，而且有助于更好地理解 ST 诱导的纳米级动力学，例如簇生长或蛋白质折叠，以及 ST 控制的纳米生物材料设计使用纳米弯液面。