Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.
Nat Commun. 2017 May 24;8:15548. doi: 10.1038/ncomms15548.
Nanoscopic and microscopic water droplets and ice crystals embedded in liquid hydrophobic surroundings are key components of aerosols, rocks, oil fields and the human body. The chemical properties of such droplets critically depend on the interfacial structure of the water droplet. Here we report the surface structure of 200 nm-sized water droplets in mixtures of hydrophobic oils and surfactants as obtained from vibrational sum frequency scattering measurements. The interface of a water droplet shows significantly stronger hydrogen bonds than the air/water or hexane/water interface and previously reported planar liquid hydrophobic/water interfaces at room temperature. The observed spectral difference is similar to that of a planar air/water surface at a temperature that is ∼50 K lower. Supercooling the droplets to 263 K does not change the surface structure. Below the homogeneous ice nucleation temperature, a single vibrational mode is present with a similar mean hydrogen-bond strength as for a planar ice/air interface.
纳米级和微观级的水滴和冰晶嵌入在液体疏水环境中，是气溶胶、岩石、油田和人体的关键组成部分。这种液滴的化学性质关键取决于液滴的界面结构。在这里，我们报告了从振动和频散射测量中获得的疏水油和表面活性剂混合物中 200nm 大小的水滴的表面结构。与空气/水或正己烷/水界面以及以前报道的室温下的平面液态疏水/水界面相比，水滴的界面具有明显更强的氢键。观察到的光谱差异与温度约低 50K 的平面空气/水表面相似。将液滴冷却至 263K 并不会改变表面结构。在均相冰成核温度以下，存在一个单一的振动模式，其平均氢键强度与平面冰/空气界面相似。
