Nanoscale probing of local dielectric changes at the interface between solids and aqueous saline solutions.
Nanoscale probing of local dielectric changes at the interface between solids and aqueous saline solutions.
复制标题
纳米级探测固体和盐水溶液之间界面处的局部介电变化。
DOI：
10.1039/d3fd00021d
复制
发表时间：
2023
影响因子：
3.4
通讯作者：
Trewby W
中科院分区：
文献类型：
--
作者：
Trewby W
溶解的离子和带电分子在界面上的流动性支撑着无数的科学和技术过程。实验上，这通常是根据电荷对电势的平均响应来测量的。高分辨率原子力显微镜（AFM）可以在固液界面上对单个吸附的离子和分子进行成像，但探测相关的动力学仍然具有高度挑战性。一种可能的策略是研究感兴趣的物种对高度局部化的AC电场的响应，其方法类似于介电谱。AFM针尖顶点所经历的介电力由所探测的样品的介电性质调制，其本身对溶剂化电荷和偶极子的迁移率敏感。以前的工作成功地使用这种方法来量化薄样品的介电常数，但空间分辨率有限。在这里，我们提出了一个策略，同时映射的纳米级的拓扑结构和局部介电变化的范围内的接口进行高分辨率AFM成像伴随着电交流测量在多频的方法。该策略在500 MHz带宽上在具有不同介电常数的纯液体和盐水溶液中进行了测试。在具有较高介电常数的液体中，系统表现为电感-电阻-电容，但离子的加入消除了电感谐振，并排除了在较高频率下的测量。高分辨率成像证明了在单一的氧化石墨烯（GrO）片与同时，但去耦介电测量。介电常数是一致的，可重复的液体，除了在较高的盐浓度，频率依赖性的影响发生。结果表明，该策略适用于固液界面介电特性的纳米级映射，但需要更多的工作来充分理解支撑测量的不同物理效应。
The mobility of dissolved ions and charged molecules at interfaces underpins countless processes in science and technology. Experimentally, this is typically measured from the averaged response of the charges to an electrical potential. High-resolution Atomic Force Microscopy (AFM) can image single adsorbed ions and molecules at solid–liquid interfaces, but probing the associated dynamics remains highly challenging. One possible strategy is to investigate the response of the species of interest to a highly localized AC electric field in an approach analogous to dielectric spectroscopy. The dielectric force experienced by the AFM tip apex is modulated by the dielectric properties of the sample probed, itself sensitive to the mobilities of solvated charges and dipoles. Previous work successfully used this approach to quantify the dielectric constant of thin samples, but with limited spatial resolution. Here we propose a strategy to simultaneously map the nanoscale topography and local dielectric variations across a range of interfaces by conducting high-resolution AFM imaging concomitantly with electrical AC measurements in a multifrequency approach. The strategy is tested over a 500 MHz bandwidth in pure liquids with different dielectric constants and in saline aqueous solutions. In liquids with higher dielectric constants, the system behaves as inductive–resistive–capacitive but the adjunction of ions removes the inductive resonances and precludes measurements at higher frequencies. High-resolution imaging is demonstrated over single graphene oxide (GrO) flakes with simultaneous but decoupled dielectric measurements. The dielectric constant is consistent and reproducible across liquids, except at higher salt concentrations where frequency-dependent effects occur. The results suggest the strategy is suitable for nanometre-level mapping of the dielectric properties of solid–liquid interfaces, but more work is needed to fully understand the different physical effects underpinning the measurements.