Papaderakis Athanasios A, Roh Ji Soo, Polus Kacper, Yang Jing, Bissett Mark A, Walton Alex, Juel Anne, Dryfe Robert A W
Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Henry Royce Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Faraday Discuss. 2023 Oct 12;246(0):307-321. doi: 10.1039/d3fd00037k.
Electrowetting is a simple way to induce the spreading and retraction of electrolyte droplets. This method is widely used in "device" applications, where a dielectric layer is applied between the electrolyte and the conducting substrate. Recent work, including contributions from our own laboratory, have shown that reversible electrowetting can be achieved directly on conductors. We have shown that graphite surfaces, in particular when combined with highly concentrated electrolyte solutions, show a strong wetting effect. The process is driven by the interactions between the electrolyte ions and the surface, hence models of double-layer capacitance are able to explain changes in the equilibrium contact angles. Herein, we extend the approach to the investigation of electrowetting on graphene samples of varying thickness, prepared by chemical vapor deposition. We show that the use of highly concentrated aqueous electrolytes induces a clear yet subtle electrowetting response due to the adsorption of ions and the suppression of the negative effect introduced by the surface impurities accumulating during the transfer process. The latter have been previously reported to fully hinder electrowetting at lower electrolyte concentrations. An amplified wetting response is recorded in the presence of strongly adsorbed/intercalated anions in both aqueous and non-aqueous electrolytes. The phenomenon is interpreted based on the anion-graphene interactions and their influence on the energetics of the interface. By monitoring the dynamics of wetting, an irreversible behaviour is identified in all cases as a consequence of the irreversibility of anion adsorption and/or intercalation. Finally, the effect of the underlying reactions on the timescales of wetting is also examined.
电润湿是一种诱导电解质液滴铺展和回缩的简单方法。这种方法广泛应用于 “器件” 应用中，即在电解质和导电基底之间施加一层介电层。包括我们自己实验室的研究在内的近期工作表明，在导体上可以直接实现可逆电润湿。我们已经表明，石墨表面，特别是当与高浓度电解质溶液结合时，表现出很强的润湿效应。该过程由电解质离子与表面之间的相互作用驱动，因此双层电容模型能够解释平衡接触角的变化。在此，我们将该方法扩展到对通过化学气相沉积制备的不同厚度的石墨烯样品上的电润湿进行研究。我们表明，由于离子的吸附以及对转移过程中积累的表面杂质所引入的负面影响的抑制，使用高浓度水性电解质会引发明显但细微的电润湿响应。此前有报道称，在较低电解质浓度下，后者会完全阻碍电润湿。在水性和非水性电解质中，当存在强烈吸附 / 嵌入的阴离子时，会记录到放大的润湿响应。基于阴离子 - 石墨烯相互作用及其对界面能量学的影响对该现象进行了解释。通过监测润湿动力学，在所有情况下都识别出一种不可逆行为，这是阴离子吸附和 / 或嵌入不可逆性的结果。最后，还研究了潜在反应对润湿时间尺度的影响。
