一种电化学原位生成和检测单个离子水簇及其在纳米科学应用的新方法

Traditionally, in single particle collision electroanalytical chemistry, analytes such as nanoparticles (including emulsion droplets, etc.) are prepared in advance and added to the electrolyte solution in contact with the ultramicroelectrode (UME) during testing. This often leads to agglomeration of the nanoparticles, making it difficult to detect "only one particle collision at a time." In response to this common problem, the project intends to establish a novel method for electrochemical in-situ generation and detection of single ionic water clusters and its application in nanoscience. This in-situ detection can effectively solve this “agglomeration” problem due to the short time interval between the preparation and detection of ionic water clusters. This method is based on the application of electrochemical means to transfer small hydrated ions from a micro/nano glass pipet into an immiscible organic electrolyte solutions, the mechanism by which a single ionic water cluster is formed between the small hydrated ions and larger/lipophilic counter-ions via electrostatic interactions in the organic phase. Reversing the polarization potential applied at the micro/nano liquid/liquid interface, the ionic water clusters by diffusion or electromigration are encountered and then fused to the interface, and one ion-current "instantaneous event" can be detected. This method provides a new mechanism for preparing nanoparticles based on the principle of microfluidic fluid mechanics. It can be widely used in the nanoscience, such as preparation of monodispersed droplets, precious metals and quantum dot nanoparticles and drug delivery, to name a few.

传统单颗粒碰撞电分析化学的被分析物如纳米粒子(包括乳滴等)都是事先制备好，测试时再加入到与超微电极(UME)接触的电解质溶液中。这样往往会导致纳米粒子的团聚，使“每次只有一个粒子碰撞”的检测变得困难。针对该共性问题本项目拟建立一种电化学原位生成和检测单个离子水簇及其在纳米科学应用的新方法。该原位检测由于离子水簇的制备与检测的时间间隔短，可以有效解决这个问题。该方法基于使用电化学手段使微纳玻璃管里的小的水合离子转移入互不相溶的有机电解质溶液里，该水合离子与有机相大的/亲油性的对离子之间由于静电相互作用形成单个离子水簇的机理。逆转施加在微纳液/液界面的极化电位，离子水簇通过扩散或电迁移碰到并融合于界面，可检测到一个个的离子电流"瞬时事件"。该方法提供了一种不同于以往基于微流控流体力学原理制备纳米粒子的新机理，可被广泛应用于制备单分散液滴、贵金属和量子点纳米粒子和药物输送等纳米科学领域。

背景：单颗粒电化学可以在溶液中研究单个微纳硬粒子（如金属或介电粒子）、软粒子（如乳液、细胞、囊泡、病毒、生物大分子）甚至原子团簇等的电化学行为。在单颗粒电化学的传统实践中，往往直接将待测粒子加入到与微纳电极接触的电解质溶液中，让粒子在溶液中自由扩散/电迁移碰撞电极。这种模式下，粒子在较高离子强度下往往会发生团聚，因而对其电化学信号的解析显得困难和复杂。.主要研究内容、重要结果和关键数据：为了解开粒子团聚的难题，我们首次使用微型液/液界面结合双恒电位计时电流法，实现了一种新型乳液的原位生成和其单颗粒电化学测量。简而言之，在界面施加电场驱使水合无机离子进入油相，并在油相与大体积的有机抗衡离子生成拮抗盐。拮抗盐的无机离子被水溶剂化，有机抗衡离子被油相溶剂化，由于静电引力形成跨过水/油界面的离子双电层。随后，施加相反方向的电场能够观察到与生成电场方向相反的离散离子电流尖峰。尖峰下降支遵循整体电解模型。我们猜想这些尖峰是由离子双电层包裹的纳米水团簇与极化微界面的碰撞、融合并释放水合离子到水相一侧造成的。这些水团簇是一类新型油包水纳米乳液，被命名为离子体。采用单颗粒电化学研究了水相离子电荷密度、有机溶剂、有机相电解质、可极化电势窗内转移离子等对离子体的形成影响。我们还使用化学极化法结合动态光散射、核磁共振、悬滴法来辅助揭示离子体的形成机理。离子体融合了乳液和脂质体的特征：受离子双层自发组装驱动的两相混合系统。最后，我们还提出了通过球形离子电容器来定量描述其物化行为。.科学意义：由于电化学原位生成和测量离子体之间的时间间隔非常短，“团聚”问题被我们开发的“生成-测量”单颗粒电化学彻底解决。此外，离子体作为一大类新的微/纳乳液，竟然是通过单颗粒电化学发现的，这在单颗粒电化学发展史上还是第一次，即单颗粒电化学对胶体与表面化学的直接贡献。通过该项目的实施，离子体的理论框架被初步建立起来。