Electrochemical anion sensing at self-assembled monolayers and polymeric interfaces

阴离子是生物、医学和环境应用领域众多的相关靶点。因此，迫切需要发展选择性、敏感和实际适用的阴离子感应方法，特别是在竞争性介质中（这是大多数实际应用所需要的）。电化学方法（伏安法、阻抗法或电位法）提供了一种功能强大但实验相对简单的方法来探测溶液或界面上的合成受体，这将是其他常规技术（如核磁共振或紫外可见光谱）探测的挑战。将传感器固定在表面（通常是自组装单层，SAMs）具有许多优点，包括绕过受体溶解度限制，显着减少所需受体的数量，并且由于界面上的预组织和介电效应，还可以提供传感放大。迄今为止，许多阴离子受体的阴离子感应能力已经被研究过（通常含有氢键（HB）结合位点），但一个很大程度上不发达的领域是基于卤素键（XB）受体基元的阴离子的界面电化学感应。卤素键已被证明是一种强的、定向的非共价相互作用，通常优于HB类似物，因此提供了改进阴离子传感器设计的机会。此外，对具有XB基序的可接受的聚合物界面的探索提供了可能的多价效应、介电效应和电场效应的研究，这些效应可能会极大地影响界面上阴离子结合/传感的效率。本项目旨在通过各种电化学技术（特别是伏安和阻抗传感）研究HB/ xb基结合基序（如原或碘三唑）自组装单层的阴离子结合能力，然后进一步研究流动下的界面电化学阴离子传感，这对于sigma键界面来说是前所未有的。将在竞争性溶剂介质（ACN/H2O体系）中对一系列阴离子进行系统研究，并对HB和XB类似物进行比较。此外，还将比较具有类似氧化还原活性的基于xb设计的sam和聚合物薄膜中的离散受体。将开发一种方法，用于使用受控的自由基聚合程序，如原子转移自由基聚合（ATRP）或可逆加成-碎片链转移聚合（RAFT），对这种接受性单体基序（包括氧化还原标记和非氧化还原标记）进行表面引发聚合。接下来将对所得到的薄膜进行广泛的表征（例如，多分散性、薄膜厚度、伏安行为），并对一系列阴离子物种进行全面的电化学传感研究。该项目属于EPSRC物理科学研究领域：分析科学、电化学科学、高分子材料。

Anionic species are relevant targets in a multitude of fields for biological, medicinal and environmental applications. Thus, there is significant demand for the development of approaches for selective, sensitive and practically applicable anion sensing, particularly in competitive media (which is required for most real-world applications). Electrochemical methods (voltammetric, impedimetric or potentiometric) provide a powerful yet relatively experimentally simple approach to probe synthetic receptors in solution or at interfaces, which would be otherwise challenging to probe with other routinely used techniques like NMR or UV-Vis spectroscopy. Immobilisation of a sensor onto a surface (often in self-assembled monolayers, SAMs) offers a number of advantages, including bypassing receptor solubility limits, significantly reducing the quantity of receptor required and can also provide a sensing amplification due to preorganisation and dielectric effects at an interface. The anion sensing capabilities of a number of anion receptive, redox-active receptors have been investigated thus far (often containing hydrogen bonding (HB) binding sites) but an area which is largely underdeveloped is interfacial, electrochemical sensing of anions with halogen bonding (XB) based receptive motifs. Halogen bonding has been shown to be a strong, directional non-covalent interaction that often outperforms HB analogues and therefore presents an opportunity to improve anion sensor designs. Further to this, an exploration of receptive, polymeric interfaces with XB motifs offers an investigation into possible multivalent, dielectric and electric field effects that could greatly influence the efficacy of anion binding/sensing at an interface. This project aims to investigate the anion binding capabilities of self-assembled monolayers with HB/XB-based binding motifs (e.g. proto- or iodotriazoles) via various electrochemical techniques (particularly voltammetric and impedimetric sensing), and then progress to studying interfacial electrochemical anion sensing under flow, which is unprecedented for a sigma bonding interface. A systematic study with a range of anions will be conducted in competitive solvent media (ACN/H2O systems) and comparisons will be drawn between HB and XB analogues. Furthermore, a comparison between discrete receptors in SAMs and polymeric films with a similar redox-active, XB-based design will be investigated. A methodology will be developed for surface-initiated polymerisation of this receptive monomer motifs (both redox-tagged and not) using a controlled radical polymerisation procedure such as atom transfer radical polymerisation (ATRP) or reversible addition-fragmentation chain-transfer polymerisation (RAFT). This will be followed by extensive characterisation of the resulting films (e.g. polydispersity, film thickness, voltammetric behaviour) and comprehensive electrochemical sensing studies for a range of anionic species.This project falls within the EPSRC Physical Sciences research area: analytical science, electrochemical sciences, polymer materials.