The effect of the surface coverage of the phosphonic acid terminated self-assembled monolayers on the electrochemical behavior of dopamine

The surface coverage of 3-mercaptopropylphosphonic acid (HS-CH₂CH₂CH₂-PO₃H₂, MPPA) self-assembled monolayers (SAMs) on gold surface can be controlled by the dissociation degree of phosphonic acid groups (-PO₃H₂) in the bulk solution and adsorption time of MPPA molecules under the basic condition. Electrochemical measurements show that the low-density MPPA-SAMs modified gold electrode enhances significantly the kinetics of electron transfer of dopamine (DA), and improves the antifouling capability of modified electrode towards DA oxidation. The present results offer crucial information for design and optimization of the electrochemical sensors for DA determination.