arXiv 2007.098432020-07physics.app-phcond-mat.mtrl-sci

pH敏感的超薄氧化物-液态金属体系：理解其基本传感机制

pH-Sensitive Ultra-thin Oxide-Liquid Metal System: Understanding the Fundamental Sensing Mechanism

Atanu Das

AI总结：

本文研究液态金属GaInSn悬滴的超Nernstian pH响应，揭示超薄Ga2O3界面热力学驱动的离子交换机制，并通过引入离子交换因子推导统一Nernst方程，为二维氧化物电化学传感器提供新理论基础。

摘要：

本文研究了液态金属（共晶GaInSn）以悬滴形式呈现时的pH响应，并在pH 4至10范围内获得了92.96 mV的灵敏度。与电解质位点结合表面59.1 mV的pH灵敏度基本极限不同，这种超Nernstian pH灵敏度源于一种自发电化学反应，该反应与超薄（1-3 nm）Ga2O3-电解质界面处增强的离子交换有关，该过程纯粹由热力学驱动，使体系达到涉及镓酸根离子和双镓酸根离子的最低系统能量。通过引入离子交换因子x，推导出一个统一的Nernst方程来解释超Nernstian pH灵敏度，并发现pH灵敏度与Pourbaix pH-电位公式之间存在直接联系。研究发现，59.1 mV的Nernstian灵敏度仅在对称离子交换（x=1）反应中出现，而非对称离子交换可产生远超Nernst灵敏度的结果。我们的发现具有重要的科学意义，有望重新定义固态电化学传感器中离子传感机制的传统概念，并推动未来基于二维氧化物的电化学传感器的发展。

英文摘要：

The pH response of liquid metal (eutectic GaInSn) in the form of a pendant drop is investigated and the sensitivity of 92.96 mV in the pH range from 4 to 10 is obtained. Unlike the fundamental limit of pH sensitivity of 59.1 mV in an electrolyte-site binding surface, the super-Nernstian pH sensitivity originated from a spontaneous electrochemical reaction associated with an enhanced ionic exchange at the ultra-thin (1-3 nm) Ga2O3-electrolyte interface which is purely driven by thermodynamics, rendering to the lowest system energy possible involving gallate and bi-gallate ions. A unified Nernst equation is derived by introducing an ion-exchange factor x to explain superNernstian pH sensitivity and found a direct link between pH sensitivity and Pourbaix pH-Potential formulations. It is found that Nernstian sensitivity of 59.1 mV occurs only for symmetric ion exchange (x=1) reaction, whereas asymmetric ion exchanges could result in sensitivity far beyond the Nernst sensitivity. Our findings have great scientific significance, which could redefine the conventional concept of the ion sensing mechanism in a solid-state electrochemical sensor and push forward the future development of the 2D oxide-based electrochemical sensor.

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