Fabrication of gold dots for DNA based nano-sensors

Here we report efforts towards fabrication of DNA based nanosensors, where DNA molecules were immobilized on gold-dot arrays. AFM was used as the main characterization tool. Two major challenges associated with characterizing these nanosensors are: 1) constructing small (<10 nm high) attachment sites on a flat surface to resolve the details of the hybridized DNA lattice and 2) fabricating attachment sites on a surface that allows the lattices to be well separated. We have chosen silicon as the substrate since atomically flat surfaces are readily available. For the formation of the gold-dot arrays, we combined e-beam lithography with metal deposition via an e-beam evaporation. The fabrication process was confirmed by AFM imaging. For DNA attachment we have used DNA functionalized on one end with multi-thiolated dendrimers, an attachment strategy developed in our lab. After exposing the surface to the DNA solution, the DNA was found to be attached to similar to 5% of the gold dots. To improve the attachment technique, oxygen plasma cleaning and ethanol treatment have been investigated. Finally, a higher yield (65% of total scanned areas) of DNA attachment to the gold dots was achieved.