Enhanced fluorescence and near-field intensity for Ag nanowire/nanocolumn arrays: evidence for the role of surface plasmon standing waves

Abstract

We use scanning fluorescence microscopy and electron beam lithography to probe the mechanism of fluorescence enhancement by periodic arrays of silver nanostructures, determining the optimum size and spacing of both Ag nanowires and Ag nanocolumns for incident light of different wavelengths and polarizations. Finite difference time domain (FDTD) calculations show a systematic variation with spatial period and incident polarization of the local electric field above the surface of the arrays which correlate well with that of the measured fluorescence enhancement, but a lack of a simple proportionality indicates that the dependence of the radiative and nonradiative decay rates on array geometry must be included in models for this effect. The dependence of the enhancement on spatial period and polarization indicates the importance of surface plasmon standing waves in this effect.

Enhanced Fluorescence Microscopic Imaging by Plasmonic Nanostructures: From a 1D Grating to a 2D Nanohole Array

“…The fluorescence intensity of the 2D substrate was much higher than the fluorescence intensity of the other surfaces. Using a plain glass substrate as a reference, the enhancement factors (EFs) for the different substrates were calculated using Equation (1), and are shown in Figure 6c:21, 25 Here, I n and I nB are the fluorescence intensities of Cy5 measured on the grating/flat silver surfaces and the background intensity where Cy5 is absent, respectively. I f and I B are the fluorescence intensities of Cy5 and the ‘background’ intensity on the plain glass slide.…”

Tailored Plasmonic Gratings for Enhanced Fluorescence Detection and Microscopic Imaging

“…Surprisingly few studies have been published to date that exploit metallic grating coupled surface plasmon resonance for enhanced fluorescence microscopic observation 16, 17. Gratings consisting of Alq 3 and dielectric material have been developed for organic light‐emitting diodes (OLEDs) and biosensors18 and silver nanowires have been recently fabricated as periodical grating arrays on Si (001) substrate for fluorescence intensity enhancement 19. In the relevant study, the silver nanowires grating was fabricated on a flat Si (001) substrate surface using electron (e)‐beam lithography and a lift‐off procedure.…”

Effect of Extended Extinction from Gold Nanopillar Arrays on the Absorbance Spectrum of a Bulk Heterojunction Organic Solar Cell

“…This however is the opposite of what we have seen in the correspondence between our extinction measurements and the EQE measurement; it leads us to ask whether field enhancement within the organic layer does occur at wavelengths corresponding to particle plasmon excitation in our devices. Fluorescence maps of molecular films on metallic nanostructures have been demonstrated to reveal the excitation of particle plasmon and surface plasmon resonances in such structures [17][18][19][20][21]; locations in the map where enhancement in fluorescence occurs indicate regions of localized field enhancement. The insert in Figure 4 shows a fluorescence map across three different P3HT:PCBM film-covered NP arrays on an ITO coated glass substrate (for this measurement no Al/TiOx layers were deposited).…”