(741f) Optical Sensing with Surface Plasmon Enhanced Transmission through Surfaces with Nanostructured Topology

Sensors based on surface plasmon resonance (SPR) have become increasingly popular as a label-free method for measuring the binding of analytes to functionalized surfaces and in the detection of immobilized biomolecules. One of the key attributes of SPR sensing is that it eliminates the complex labeling/conjugation steps required of competing techniques that utilize fluorescently labeled molecules in detection assays. In addition, the large field-enhancement associated with SPR is the basis for many surface analytical techniques such as surface-enhanced Raman scattering and surface-enhanced fluorescence.

Although SPR is typically achieved with prism-coupled configurations, it has recently been discovered that plasmon-enhanced transmission of light can be achieved at nanostructured surfaces, such as nanometer-sized hole and slit arrays. In this work, we demonstrate the appearance of surface plasmon enhanced optical transmission through nanostructured grating surfaces. Enhanced light transmission is observed over a narrow wavelength range corresponding to conditions that excite surface plasmons at the gold-air interface. We explore the nature of these transmission peaks to identify the origins of the enhanced transmission as well as the impact of changing the surface profile, including the grating pitch and amplitude, in order to fine tune the optical response. A novel chirped grating based upon spontaneous buckling of an elastomeric film is used to modulate the grating structure and demonstrate the impact of surface topology. In addition, the utility of this device as an ex-situ sensor is demonstrated by measuring the thickness of various thin films.A model immunosensing application is also examined involving the formation of immunocomplexes between bovine serum albumin (BSA) and anti-BSA. This work demonstrates the utility and versatility of this grating-based SPR sensing technique.