Multiple Surface Functionalities through Step-by-Step Hydrolysis of Self-Assembled Monolayers

Self-assembled monolayers (SAMs) of N-(3-diethylphosphatoxy)propyl-11-mercaptoundecanamide (PPMA) were prepared on gold surfaces. The SAMs, consisting originally of a phosphonate surface functionality, were subjected to step-by-step acidic hydrolysis to reveal two different functional groups: (a) a hydroxyl and (b) a carboxylic group. At each stage these SAMs were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and water contact angle measurements. To our best knowledge, for the first time a methodical approach was used to obtain three different surface functionalities from one type of molecule on the surface of gold. These SAMs could provide a novel approach for conducting high-throughput investigations, for instance for cell adhesion. The present study contributes toward the understanding of reactions at interfaces as it demonstrates the influence of step-by-step hydrolysis on SAMs.