Novel redox molecules for surface electrochemistry

The research presented herein reports the development of two novel redox molecules for biosensing applications. Frequently electrochemical biosensors necessitate the use of strictly controlled conditions including the pH of the surrounding solution. Electrochemical biosensors that only operate under such conditions are not viable as portable sensors for in-field analysis. Consequently, a method for measuring the pH in conjunction with electrochemical biosensors would provide an opening for such sensors in in-field analysis. A novel redox molecule, JUGSH, has been prepared for this purpose. In a separate investigation, a ruthenium complex has been prepared which allows tuning of its formal potential by altering the structure of one ligand. This novel redox molecule is destined for use in multi-analyte arrays. By altering the formal potential of the redox molecule, a series of redox reporters can be prepared to allow differentiation between analytes. The novel redox molecule JUGSH consists of a hydroxy-naphthoquinone with an alkanethiol chain that allows formation of a self-assembled monolayer (SAM) of JUGSH on gold electrodes. X-ray spectroscopy analysis was employed for characterisation. The electrochemical properties of a JUGSH SAM were investigated along with the pH dependence of the formal potential. After further research into the pH dependence of the electron transfer rate coefficient, JUGSH was applied to the analysis of pH together with an electrochemical biosensor. Two peptide sensors for metal detection developed previously were employed to test the concept of measuring pH with JUGSH. The peptides employed were angiotensin I and Gly-Gly-His immobilised on a thioctic acid SAM and 3-mercaptopropionic acid SAM for lead and copper detection respectively. JUGSH was demonstrated to have the ability to measure the pH of the analyte solution allowing compensation of the sensor’s electrochemical response. The angiotensin I sensor was shown to have a viable working range from pH 3 to pH 7. A ruthenium complex ...