Self-assembled Monolayers of Ferrocenvlthiols on Gold. An Electrochemical and Optical Charactensation

Short chain ferrocenyalkylthiols, (C5H 5 )Fe(C5H4)CO(CH2) n SH (n= 3, 5 and 7), were self-assembled on gold (111).The influence of the chain length and adsorption time on stability, surface coverage and order of the monolayers were assessed electrochemically and by the use of optical ellipsometry.The redox behaviour and structure of the SAMs were strongly dependent on the chain length.Long adsorption times were required to obtain ordered monolayers with high surface coverage.Ellipsometry indicated that the thicknesses of the layers were dependent on the surface concentration of the ferrocene derivatives.The thickness of the monolayer with the longer alkyl chain was estimated to be 2.9 nm with a complex refractive index h= 1.472-0.076Í.Imaging Ellipsometry allowed the visualisation of the lateral thickness distribution of a monolayer deposited on gold.