Optical Sensitivities of Three Flow-through Porous Plasmonic Sensors

Abstract

The research studies presented in this thesis include analysing the sensitivity of three different plasmonic substrates with arrays of open-ended nanometric holes. The first plasmonic nanohole array based sensor consisted of commercially available transmission electron microscopy grids with well-defined, periodic arrays of nanoholes etched through a thin silicon nitride membrane. These grids were coated with silver and used to detect changes to the surrounding bulk fluid via optical transmission spectroscopy. The second plasmonic nanohole array based sensor was similar in structure to the first sensor, but consisted of a silicon chip with multiple well-defined, periodic nanohole arrays suspended on a thin, silicon nitride membrane coated with silver. The surface sensitivities of these chips were measured using optical transmission spectroscopy by stacking adlayers of films to the surface of the sensor. Through these experiments with periodic nanohole arrays, the surface sensitivity was shown to be highly variable and dependent upon the geometry of the nanohole array. Finally, a third plasmonic sensor was fabricated and tested which was based on commercially available porous anodic alumina filters. The pores of this filter were longer, less ordered and non-periodic, yet the filters were shown to be suitable for detecting an analyte at parts per trillion levels after evaporatively coating the filters with silver. Both simulations and experiments using optical transmission spectroscopy were used to understand and identify the variables that affect the sensitivity of these three platforms.