Multilayer formation of copper ions (Cu2+) deposited onto self-assembled monolayers of alkanedithiols on Au (111) surfaces

Self-assembled monolayers (SAMs) of 1,5-pentanedithiol and 1,9-nonanedithio l on Au (111) surfaces were used to adsorb copper ions (Cu2+) from an ethan olic solution of cupric chloride (CuCl2) by chemical interaction of thiol g roups and copper ions assembling multilayer structures. Ellipsometry, conta ct angle measurement and X-ray photoelectron spectroscopy (XPS) confirmed t hat the alkanedithiol molecules formed SAMs with only one-ended thiol group s attached to the gold surface, leaving the other-ended thiol groups free, which is supported by the molecular mechanics calculation. XPS and X-ray Au ger electron spectroscopy (XAES) not only indicate that copper ions deposit ed onto SAMs from the solution by the chemical reaction of copper ions with ended free thiol groups of SAMs, but more importantly demonstrate that cop per is present in the +1 oxidation state in the multilayer system. Atomic F orce microscopy (AFM) was used to observe SAMs and multilayer structures.