Design of Inverted Nano-Cone Arrayed SERS Substrate for Rapid Detection of Pathogens

Rapid detection of bacteria is a very critical and important part of infectious disease treatment. Sepsis kills more than 25 percent of its victims, resulting in as many as half of all deaths in hospitals before identifying the pathogen for patients to get the right treatment. Raman spectroscopy is a promising candidate in pathogen diagnosis given its fast and label-free nature, only if the concentration of the pathogen is high enough to provide reasonable sensitivity. This work reports a new design of surface-enhanced Raman spectroscopy (SERS) substrate which will provide high enough sensitivity and fast and close contact of the target structure to the optical hot spots for immunomagnetic capturing-based bacteria-concentrating technique. The substrate uses inverted nanocone structure arrays made of transparent PDMS (Polydimethylsiloxane) to funnel the light from the bottom to the top of the cones where plasmonic gold nanorods are located. A high reflective and low loss layer is deposited on the outer surface of the cone. Given the geometry of cones, photons are multi-reflected by the outer layer and thus the number density of photons at hotspots increases by an order of magnitude, which could be high enough to detect immunomagnetically densified bacteria.