Rapid assembly of ssDNA on gold electrode surfaces at low pH and high salt concentration conditions

This paper reports a simple method to immediately functionalize ssDNA onto gold electrodes using a low pH-induced and high salt concentration solution route. Electrochemical impedance spectroscopy, cyclic voltammetry, and chronocoulometry were used to characterize the ssDNA self-assembled monolayer (SAM). The effects of pH, ionic strength, and ssDNA sequences for DNA adsorption were investigated. It was found that thiolated ssDNA can be attached to gold electrodes using a low pH-induced route in a high salt concentration solution. A synergistic effect between pH and the salt has been suggested by studying the fundamental kinetics. The surface coverage of 3.054 × 1013 molecules/cm2 in pH 3.4 buffer was higher than that of 4.574 × 1012 molecules/cm2 in pH 7.4 buffer. The ssDNA on the gold surface was functional and was able to recognize complementary DNA strands.