Dual-function metallic nanohole arrays: Electrokinetic analyte concentration and plasmonic sensing

Metallic nanostructures facilitate analyte sensing through localization of surface plasmons. In this work, we demonstrate that the same metal nanostructures can also facilitate the concentration and localization of analyte at the active sensing surface. Specifically, the structure of flow-through plasmonic nanohole array sensors presents the opportunity of locally increasing analyte concentration using electrokinetic phenomena. The synergistic combination of analyte concentration and sensing promises increased effectiveness and reduced detection limits. An 80 fold increase in concentration is achieved in 100 s with a 100 V field applied. This is the first demonstration of an optofluidic system in which a nanostructure enables both analyte concentration and sensing.