An ultra sensitive DNA detection by using gold nanoparticle multilayer in nano-gap electrodes

This paper reports an electrical DNA detection method that detects target DNA at concentrations as low as 1 fM by using self-assembly multilayer gold nanoparticle structure between nano-gap electrodes. The distance of the gap between the electrodes is 300 nm and the height of the electrodes is 65 nm. A multilayer gold nanoparticle structure can be built on thin film of SiO ₂ silicon wafer. Bifunctional organic molecules are used to build up gold nanoparticle monolayer on the wafer substrate. After hybridization among target DNA, 5′-end thiol-modified probe DNA and 3′-end thiol-modified capture DNA; a second layer of gold nanoparticle is built up through a self-assembly process between gold nanoparticles and thiol-modified end of probe DNA. When the applied voltage is the same, electrical current through multilayer gold nanoparticle structure is much greater than that through monolayered gold nanoparticle structure. Therefore, target DNA in sample solution can be detected through a significant degradation in electrical resistance from monolayered gold nanoparticle to multilayer gold nanoparticle structures. The concentration of target DNA in tested sample solutions ranges from 1 fM to 100 pM. The linear I-V curves of multilayer gold nanoparticle structures indicate the device proposed in this study can detect target DNA concentrations as low as 1 fM. Additional approaches are also suggested in this study to improve the sensitivity in DNA detection by using I-V measurements through multilayer gold nanoparticle structures.