Stable perfluorosilane self-assembled monolayers on copper oxide surfaces: Evidence of siloxy-copper bond formation

Formation of stable and hydrophobic self-assembled monolayers (SAMs) on an oxidized copper (Cu) surface has been accomplished via reaction with 1H,1H,2H,2H-perfluorodecyldimethylchlorosilane (PFMS). The perfluoroalkyl SAMs showed sessile drop static contact angles of more than 125 degrees for pure water and stability against exposure to boiling water, boiling nitric acid solution, and warm sodium hydroxide solution for up to 30 min. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared reflection/absorption spectroscopy (FT-IRRAS) data reveal a coordination of the PFMS silicon (Si) atom with a cuprate (CuO) molecule present on the oxidized copper substrate. The data give good evidence that the stability of the SAM film on the PFMS-modified oxidized Cu surface is largely due to the formation of a siloxy-copper (-Si-O-Cu-) bond via a condensation reaction between silanol (-Si-OH) and copper hydroxide (-CuOH). The extremely hydrophobic and stable SAMs on oxidized Cu could have useful applications in corrosion inhibition for micro/nanoelectronics and/or heat exchange surfaces exploiting dropwise condensation.