Charge-based forces at the Nafion-water interface.
Charge-based forces at the Nafion-water interface.
复制标题
Nafion-水界面处基于电荷的力。
DOI：
10.1021/la304418p
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Pollack,GeraldH
中科院分区：
文献类型：
--
作者：
Das,Ronnie;Pollack,GeraldH
位于亲水表面旁边的界面水已被证明在光谱、机械和电学上与本体水不同。界面水也被证明排除带负电荷和正电荷的微球，因此被称为“排除区”。测量表明，禁区相对于本体水呈现出-100 mV量级的负电势，在禁区之外的本体水区域中具有正质子的相应分布。这种电荷的分离被假设为在排除区和质子富集区之间产生静电力。为了检验这一假设，亲水性Nafion环连接到可偏转带状力传感器的尖端。传感器的设计目的是阻止质子从杠杆的一侧流向另一侧，这样任何基于质子的力都将保持单向。pH敏感的染料测量证实，质子主要局限于一侧。当杠杆组件暴露在水中时，传感器朝向质子偏转。在20 min的时间内，偏转量约为20 μm，相当于约22 μN的力。因此，静电力得到证实。如果排斥区普遍存在于亲水性表面，包括生物表面，那么所产生的静电力可能在许多生物现象中发挥重要作用，包括粘附和蛋白质折叠。
Interfacial water lying next to hydrophilic surfaces has been shown to be spectroscopically, mechanically, and electrically distinct from bulk water. Interfacial water has also been shown to exclude negatively and positively charged microspheres and has thus become known as the “exclusion zone”. Measurements have demonstrated that exclusion zones exhibit a negative electrical potential on the order of −100 mV relative to bulk water, with a corresponding distribution of positive protons in the bulk water region beyond the exclusion zone. This separation of charge is hypothesized to create an electrostatic force between the exclusion zone and the proton-enriched zone beyond. To test this hypothesis, a hydrophilic Nafion ring was attached to the tip of a deflectable ribbonlike force sensor. The sensor was designed to obstruct the flow of protons from one side of the lever to the other, so that any proton-based force would remain unilateral. pH-sensitive dye measurements confirmed that the protons were largely confined to one side. When the lever assembly was exposed to water, the sensor deflected toward the protons. Over a period of 20 min, deflection amounted to approximately 20 μm, corresponding to a force of approximately 22 μN. Hence, electrostatic forces are confirmed. If exclusion zones exist ubiquitously at hydrophilic surfaces, including biological surfaces, then the resulting electrostatic forces may play significant roles in many biological phenomena including adhesion and protein folding.