Optofluidically Tuned Fluorescence Enhancement by Plasmonic Nanocup Arrays
- PDF / 4,544,534 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 24 Downloads / 201 Views
Optofluidically Tuned Fluorescence Enhancement by Plasmonic Nanocup Arrays Sujin Seo1, Abid Ameen1 and Gang Logan Liu2 1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green Street, Urbana, IL 61801, U.S.A. 2 Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 306 N. Wright Street, Urbana, IL 61801, U.S.A. ABSTRACT We demonstrate fluidically tuned fluorescence enhancement on the colorimetric substrate with the plasmonic effects induced by the periodic gold nanocup arrays. The fluorescence enhancement by the plasmonic effect has been studied extensively by varying the geometries of nanostructures or the morphology of nanoparticles. In this study, however, the fluorescence enhancement without changing these parameters but simply by varying surrounding media on the colorimetric plasmonic surface is accomplished. The dynamic responses of fluorescence from self-assembled monolayer of dyes on the surface were monitored by flowing various fluids with different refractive indices. The dependence of the radiative decay rate as well as the scattering cross-section on the surrounding dielectric properties results into the selective enhancement of the fluorescence intensity, having a maximum at different surrounding refractive index for different fluorophores with different emission band centers. INTRODUCTION The metal enhanced fluorescence (MEF) has been studied extensively along with the studies on the plasmonic effects by metals in nano-scale.[1–3] Fluorescence intensity from an organic dye is influenced by the local electromagnetic field and photonic mode density change,[4] the distance between the fluorophore and the metallic surface,[5,6] and the fluorophore’s absorption or emission spectral overlap with the plasmonic scattering or extinction spectra.[1,7] Since the plasmonic properties depend on numerous geometrical factors of the nanoparticles or nanostructures, the enhancement of the fluorescence intensity as well as the spectral shape alteration was achieved by tuning the size and shape of the nanoparticles and changing the geometries of the nanostructures.[8,9] Many MEF studies, however, were focused on the scientific phenomena of fluorescence enhancement by applying the fluorophores on different arrangements of plasmons for different plasmonic properties but not much on the applications to sensing the external changes on the plasmons once a plasmonic system was provided. Here, we use organic fluorophores as the commonly used tags bound onto the target molecules or proteins and aim for detecting the refractive index change around the metallic nanoparticles with these fluorophores by using the conventional microscope. The fluorescence serves as adding the specificity, of which the simple plasmon based sensing platform lacks, and the refractive index change is to alter the plasmonic resonance which affects to the fluorescence excitation and emission processes. It has been reported that the radiative decay rate of a fluorophore is proportional to the r
Data Loading...
