Utilising Nanoparticle-Mediated Electrochemical Gating to Prepare a Novel Sensing Platform

One of the biggest challenges faced in modern biosensor design is achieving lower detection limits while maintaining a decent response time and low surface capacitance. The reliance of electrochemical sensors on diffusion as a mechanism for mass transport to the sensing surface means that when the distance between the analyte and the surface increases the response time varies dramatically in accordance with Ficks law. Therefore despite the development of sensors able to detect single analytes in solution if the sample size is sufficiently large the response time becomes prohibitively long.This project overcomes the problem with diffusion by utilising modified gold-coated magnetic nanoparticles (Au@MNP) that bind to the analyte and are directed to the surface of the electrode. This significantly decreases the detection limit and response time of the sensor by minimizing the reliance on diffusion as a means of mass transport of the analyte to the sensing surface.To lower the capacitance of the underlying electrode and to improve the signal to noise ratio at low detection limits the electrode was modified with different alkanethiol monolayers. Due to the passivating nature of the organic layer, electrochemistry between the underlying electrode and the redox species in solution is prevented. By situating Au@MNP's on the distal end of the organic layer a return of the electrochemical signal was observed without the non-Faradaic charging of the underlying surface.By constructing these magnetic nanoparticle-organic layer-electrode constructs it was possible to obtain electrodes that have low capacitance, are easily modified and can be "switched on"