Determination of functional head and tail groups of self-assembled monolayer (SAM) formed by 2-Mercaptoacetate on aluminium oxide substrate

In order to immobilize the biological receptor, aluminium oxide surface was functionalized by introducing a linker named 2-mercaptoacetate, which contains thiol and carboxylate functional groups. 2-mercaptoacetate will form orderly packed monolayer known as Self Assembled Monolayer (SAM) on the aluminium oxide surface. The aim of this work is to investigate and determine the head and tail of this SAM formed by the aforementioned linker on the aluminium oxide surface. The bare and the 2-mercaptoacetate modified aluminium oxide surface were compared and analyzed under X-ray photoelectron spectroscopy (XPS) to determine the head group. For further verification, 50 nm gold nanoparticle (GNP) was deposited on the 2-mercaptoacetate modified aluminium oxide to confirm thiol as a tail group of SAM layer. GNP deposition on 2-mercaptoacetate modified aluminium oxide surface was characterized by scanning electron microscope (SEM) and Atomic force microscope (AFM). XPS analysis indicates that native oxide has been grown on aluminium thin film. It also confirms the SAM structure; carboxylic and thiol as a head and tail group respectively.