Enhanced fluorescence through the incorporation of nanocones/gaps into a plasmonic gratings sensor platform

In this article, a novel plasmonic grating sensor platform was developed and tested for feasibility in sensor applications using a "lights-on" fluorescence based DNA sensor. The sensor platform combined the fluorescence enhancement of a grating-based plasmonic platform with the electric field intensifying effects of nano-scale cones and cavities. The gratings were made through a microcontact printing process that replicated HD-DVD discs in polymethylsilsesquioxane (PMSSQ) and coated in a thin gold film. Nanocavities were incorporated into the sensor platform during the printing process and nanocones were incorporated during the 100 nm gold deposition process. Fluorescently-tagged single-strand (SS) DNA molecules were immobilized onto the surface and were designed such that the molecules would fluoresce when bound to a complementary sequence. Sensor substrates were imaged after exposure to a mismatched and matched oligomer to quantify the fluorescence enhancement of the sensor. Much higher fluorescence intensity was observed on all of the plasmonic structures as compared to flat gold.