Metallic Deposition at a Liquid|Liquid Interface: A Study of Chemical Speciation and Nucleation

Abstract

Liquid/liquid interfaces provide a facile, stable interface which may be utilised in order to investigate a number of different reactions that are inaccessible in a single phase system. By sequestering the reactants in opposing phases, or exploiting the variations in reduction potentials in different solvents it is possible to examine numerous ion and electron transfer processes. Alongside spatial control over the reaction site, liquid/liquid interfaces are also able to stabilise and isolate the reaction product species. This opens up numerous possibilities to characterise the reactants, intermediates and products through in situ spectroscopy. The focus of the work presented in this thesis has been on the reactions of noble metal particles at “soft” polarisable interfaces. The work includes the use of chemical and electrochemical deposition procedures and the assembly of pre-formed metal nanoparticles. Nanoparticles are readily assembled at liquid/liquid interfaces and herein work is presented indicating that such assemblies can be utilised in order to enhance the spectroscopic response of species in solution. The in situ deposition of Au nanoparticles has been examined, confirming the presence of Au(I) as a stable reaction intermediate at the liquid/liquid interface. This has aided the investigation of the chemical synthesis of thiol protected Au nanoparticles using a 2-phase reaction. In this instance, the intermediate species have been characterised by electrochemical measurements and X-ray absorption spectroscopy in order to clarify the reaction mechanism. Through the use of in situ X-ray absorption spectroscopy, the progressive nucleation of Pd nanoparticles has been followed. The reaction was seen to proceed via a direct 2- electron reduction from Pd(II) to Pd(0) before growing through what is presumed to be an aggregative process. The reaction was strongly dependent on reactant concentration and the potential of the liquid/liquid interface enabling the observation of the growth and dissolution of meta-stable pre-nucleation clusters which could be entirely suppressed by the application of a fixed potential to the interface.

Date of Award	31 Dec 2017
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Robert Dryfe (Supervisor) & Sven Schroeder (Supervisor)