Controlled deposition of single DNA molecules on bare gold electrodes

We report a new approach to a directly controlled deposition of long deoxyribonucleic acid (DNA) molecules on a bare gold electrode array predefined on a positively charged substrate surface by electrostatic interaction without modification of gold electrodes and DNA molecules. The method involves depositing amino-terminated self-assembled monolayer on a specific region on a SiO2/Si substrate, and subsequently defining gold electrode array on the modified region by mask pattern transfer technique, as well as transferring a droplet of DNA solution onto the patterned substrate. Atomic force microscopy observations demonstrate that DNA molecules are significantly less stable on the bare gold surface than that on the aminothiolated gold surface. However, DNA can stably immobilize on the bare gold electrode array predefined on the positively charged substrate surface. The noncovalent binding of DNA onto the bare gold electrodes was shown to be robust enough to withstand ultrasonically washing. The approach represents a simple route to positioning of single DNA molecules on predefined structures, and can be potentially applied to other charged one-dimensional nanostructures.