Self-assembly of reactive difunctional molecules on nickel electrode

Abstract

Self-assembly of some reactive difunctional molecules such as mercaptopyridine, pyrazine, phenylene diisocyanide, amino ethanethiol and simple hexadecane thiol molecule have been formed on nickel surface. The adsorption behaviour has been monitored by Quartz crystal microbalance with energy dissipation (QCM-D) and the results show that these molecules form thin rigid films on the surface. QCM-D results also reveal that nickel atoms on the surface are highly stable and do not undergo any corrosion or removal of nickel atoms from the surface during the adsorption process as observed with gold surface for these molecules. Reflection-absorption infrared spectral (RAIR) measurements were performed to study the mode of binding, order and packing of these molecules on nickel surface. Ellipsometric thickness results are comparable to theoretical values and water contact angle measurements were carried out to study the change in the wettability and the observed values are slightly lesser than the data reported in literature for these molecules on gold surface. The charge transfer kinetics of these modified nickel surface have been studied by cyclic voltametry using a ferrocene redox probe in solution. An increase in the peak potential separation of the redox species was observed with the modified surfaces compared to bare nickel which may be due to the insulating nature of these monolayers.