Date of Graduation

12-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Chemical Engineering

Advisor/Mentor

Roper, D. Keith

Committee Member

Spicer, Tom O. III

Second Committee Member

Thoma, Gregory J.

Third Committee Member

Ulrich, Richard K.

Fourth Committee Member

Ware, Morgan E.

Keywords

Pure sciences; Applied sciences; Chemical sensing; Nanoparticles; Nanorings; Nanotechnology; Noble metals; Optical sensing; Plasmonics

Abstract

Chemical sensing is a key component in modern society, especially in engineering applications. Because of their widespread impact, improvements to chemical sensors are a significant area of research. One class of sensors, plasmonic sensors, is being heavily researched because of their ability to detect low levels of analyte in near real time without destroying the analyte. This work studies a new class of plasmonic sensor that utilizes diffractive coupling to improve sensor performance. Specifically, this work outlines the first study of diffractive coupling sensors with typical nanoparticle shapes. Sensitivity of this new class of sensor is directly compared to typical localized surface plasmon resonance sensors. Spectral peak location sensitivity was found to be equal to or greater than typical plasmonic sensors. These results were corroborated with numerical simulation with and without nanoparticle interaction to demonstrate the power of harnessing diffractive coupling in nanoparticle sensors.

The sensing results were then extended to analyze ordered arrays of nanorings. Nanorings were chosen because they have the highest reported sensitivity of any plasmonic shape (880 nm/RIU) in the literature and have a high surface area to volume ratio, which is a key parameter for plasmonic sensors. Theoretical simulations of diffractive coupling nanorings indicate that sensitivity is comparable to non-coupling nanorings in the literature (890 nm/RIU vs. 880 nm/RIU, respectively). Another metric of sensor performance, the figure of merit, was much higher (34) than the non-coupling ring (2). Ordered nanoring arrays which exhibit diffractive coupling improve upon current refractive index based plasmonic sensors. Further improvements to nanoring sensors' figure of merit are possible based on simulation results for nanosphere arrays.

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