Self-Assembling of Thiol Monolayers on Copper, Copper-Nickel Alloy and Nickel Using Ionic Liquid as Reducing Medium

Self-assembling of molecules on metal surfaces is one way to chemically modify surfaces for various applications. Thiol self-assemblies on metal surfaces like gold, silver and copper are formed easily while thiol monolayers on economically important metal surfaces like copper, copper-nickel and nickel surfaces are yet to be explored due to the less affinity for sulphur and rapid oxidation of metal under ambient atmosphere. Seminal works from our laboratory have shown the use of electrochemical reduction using acids as a feasible way to remove metal oxides layers and form SAMs on metal.

Ionic liquids are promising as efficient solvents for surface modifications. They have several advantages such as non volatile, recyclable and in particular large electrochemical window.

 In the present study, we are exploring the use of 2- hydroxyethanolamine formate (HEAF) ionic liquid ionic as a solvent to electrochemically reduce the oxide layers and and the impact on the self-assembly process of thiol monolayers on copper, copper-nickel alloy and nickel substrates.  It is shown that HEAF is suitable medium to reduce the metal passive oxide layers and good quality thiol monolayers can be formed on copper, copper-nickel alloy and nickel substrates by immersion in 0.05 M ethanolic solution for 18 h. The monolayers formed were characterized using different electrochemical (CV, LSV) and spectroscopic techniques (XPS, PM-IRRAS).