title: Optimization of plasmonic enhancement of fluorescence on plastic substrates.
abstract: In this work, we report on the uniform deposition of tailored plasmonic coatings on polymer substrates and on the distance dependence of the plasmonic enhancement of a fluorescent dye. Silver, gold, and silver/gold alloy nanoparticles (NPs) with a range of diameters were synthesized using chemical techniques and characterized using UV-vis absorption spectroscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM). Reproducible polyelectrolyte (PEL) layers, which were deposited on plastic microwell plates using a layer-by-layer technique, served as both a stable and uniform substrate for deposition of the NPs as well as providing spacer layers of known thickness between the NPs and the fluorescent dye. A maximum enhancement factor of approximately 11 was measured for 60 nm diameter pure silver NPs, for a dye-NP separation of approximately 3 nm. A shift in the localized surface plasmon resonance (LSPR) wavelength as a function of the effective refractive index of the PEL layers was also observed, and the measured shifts show a similar trend with theoretical predictions. This work will contribute toward the rational design of optical biochip platforms based on plasmon-enhanced fluorescence.
authors.affiliation: Biomedical Diagnostics Institute, National Centre for Sensor Research, School of Physical Sciences, Dublin University, Dublin, Ireland.
authors.forename: Robert I
authors.initials: RI
authors.lastname: Nooney
authors.forename: Ondrej
authors.initials: O
authors.lastname: Stranik
authors.forename: Colette
authors.initials: C
authors.lastname: McDonagh
authors.forename: Brian D
authors.initials: BD
authors.lastname: MacCraith
mesh_terms: D004573:Electrolytes; D005453:Fluorescence; D053768:Metal Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D010969:Plastics / Q000737:chemistry*; D013053:Spectrophotometry
chemical_list: D004573:Electrolytes; D010969:Plastics