Electrochemical Applications at the Liquid | Liquid Interface: Electroanalysis and Electrodeposition

Abstract

This thesis demonstrates the application of the interface between two immiscible electrolyte solutions (ITIES) as an electroanalytical tool and as a route for one-pot single-step synthesis and fabrication of composite films. The complexation and binding of a tripodal thiourea (i.e. a synthetic anionic receptor) was studied at ITIES via an electrochemical approach. This assessment is an application of the facilitated ion transfer (FIT) reaction, which involves transfer by interfacial complexation at ITIES. The binding affinity and stoichiometry of the receptor with various anionic species were estimated from this approach, which were found to be consistent with literature values obtained from other methods. The electrochemical approach also provided insights on the binding of the receptor in solvents with low polarity. This study exhibited the advantages of the electrochemical approach for such assessments. The ITIES was modified with 2D molybdenum disulphide (MoS2) and the ion transfer across the modified interface was studied by cyclic voltammetry. The interfacial MoS2 layer was found to enhance the transfer of cationic species but restrict the transfer of anionic species. The enhancement was anticipated due to a localised increase of the cationic concentrations at the interface due to the negatively charged MoS2 nanosheets. The interfacial MoS2 layer was also found to influence the mechanism of transfer and the diffusion zones near the interface, leading to a behaviour observed in micro-ITIES supported on solid-state membranes. The MoS2-modified ITIES was also used to synthesise metal-MoS2 and polymer-MoS2 composite films. Pd and Cu particles were electrodeposited on the pre-adsorbed MoS2 layer. The reduction of the aqueous metal precursor was performed by a reducing agent dissolved in the organic phase. The MoS2 layer was found to promote the nucleation rate of the metal particles, by enhancing the oxidation of the reducing agent. Morphologies of the deposited composites were studied, and significant variations were observed in their structures. Polymer-MoS2 composite films were prepared from poly(pyrrole) (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT). The polymerisation reaction was performed with monomers (in organic phase) electrochemically oxidised at the interface by an oxidising agent in the aqueous phase. Raman analysis suggested that the polymers were electrodeposited in their oxidised state. However, compared with pristine polymers, MoS2 sheets were found to lower the degree of oxidation of the polymeric films. The polymeric films are thought to be doped with the anion of the organic electrolyte. The polymers exhibited different morphologies. PPy films were found to be very thin and highly porous, with MoS2 assumed to affect the porosity. On the other hand, PEDOT films were found to consist of fibre(rice)-like particles, these unusual PEDOT structures are suggested to have enhanced electrical properties.

Date of Award	31 Dec 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Robert Dryfe (Supervisor) & Mark Bissett (Supervisor)