Influence of polymerisation on the reversibility of low-energy proton exchange reactions by Para-Aminothiolphenol

Abstract

The reversibility of redox processes is an important function for sensing and molecular electronic devices such as pH reporters or molecular switches. Here we report the electrochemical behaviour and redox reversibility of para-aminothiolphenol (PATP) after different polymerisation methods. We used electrochemical and photo-polymerisation in neutral buffers and plasma polymerisation in air to induce reversible redox states. The chemical stoichiometry and surface coverage of PATP in the polymerized layers were characterized by X-ray photoelectron spectroscopy (XPS), while cyclic voltammetry (CV) was used to measure the charge transfer, double layer capacitance and electrochemical rate of the layers during successive potential cycles. Our results show that the surface coverage of the redox active species is higher on electro-polymerised samples, however, after consecutive cycles all the methods converge to the same charge transfer, while the plasma polymerised samples achieve higher efficiency per molecule and UV polymerised samples have a higher electron transfer rate.

Redox Active Self-Assembled Monolayer Functioning as a pH Actuator

“…Figure 1a(i) shows the structural representation of the self-assembled 4ATP adsorbed on Au, which can dimerize in different ways depending on the polymerisation method (Figure 1a(ii-iv)). We discussed the different possibilities of polymerisation in our previous article [2]. All the three methods provided reversible proton exchange reactions where two protons and two electrons are exchanged from the molecule to the electrolyte.…”

“…The advantage of electropolymerisation is a higher charge transfer at the beginning, however, UV or plasma polymerisations can be more suitable for delivering large batches of samples, and if the application requires many cycles, they do not have much difference of charge transfer after 50 cycles. More details of the characterization and performance of the polymerized layers can be found in our previous work [2]. Figure 1d shows the schematic representation of the microfluidic platform with image of the electrochemical chip in Figure 1e and the platform in Figure 1f.…”

“…Three different methods of polymerisation of ATP were performed, Electropolymerisation, Photopolymerisation and Plasmapolymerisation. More details on the setup of the experiments are described in our previous work [2]. The charge transfer for each polymerisation method was measured and compared using CV measurements.…”

“…To this goal we studied Aminothiolphenol SAMs modified by electrochemical, optical and plasma dimerization methods that provided electrode coatings with quasi-reversible redox states able to exchange protons with the electrolyte at low voltages [2]. We correlated their chemical characterization with their electrochemical performance.…”

Electrochemical Control of pH in Nanoliter Volumes

“…Here we present and demonstrate a design that takes advantage of the large surface area that can be achieved by microfabrication. For the control of the pH we use nano-structured electrodes functionalised with redox active self-assembled monolayers (SAM's) , which we recently demonstrated to be capable of exchanging protons with small voltage biases in a reversible way for more than hundred cycles [21] . The reactor design is integrated in a microfluidic platform that allows addressing the electrodes from an external control.…”