N-Heterocyclic Carbene Based Nanolayer for Copper Film Oxidation Mitigation

The wide use of copper is limited by its rapid oxidation. Main oxidation mitigation approaches involve alloying or surface passivation technologies. However, surface alloying often modifies the physical properties of copper, while surface passivation is characterized by limited thermal and chemical stability. Herein, we demonstrate an electrochemical approach for surface-anchoring of an N-heterocyclic carbene (NHC) nanolayer on a copper electrode by electro-deposition of alkyne-functionalized imidazolium cations. Water reduction reaction generated a high concentration of hydroxide ions that induced deprotonation of imidazolium cations and self-assembly of NHCs on the copper electrode. In addition, alkyne group deprotonation enabled on-surface polymerization by coupling surface-anchored and solvated NHCs, which resulted in a 2 nm thick NHC-nanolayer. Copper film coated with a NHC-nanolayer demonstrated high oxidation resistance at elevated temperatures and under alkaline conditions.The ease of preparation and well-controlled growth process of electrochemically-induced NHC nanolayer make it an easily-applicable method for large-scale coating to provide thin and effective passivation layer for copper surfaces. Moreover, the electro-induced mechanism of NHC-nanolayer formation makes it possible to selectively deposit the protective layer on conducting copper wires without changing the optical properties of the entire device. These advantages make the presented technology highly suitable for applications that require high transparency, such as solar cells and electroluminescence devices.