Large Enhancement of Quantum Dot Fluorescence by Highly Scalable Nanoporous Gold

Abstract

Nanoengineered metallic materials have been shown to have a number of exclusive physicochemical properties not available at neither larger (micro- and macroscopic) nor smaller (molecular) scales. Recently, these materials in particular have drawn significant attention due to their capability to enhance fluorescent signals of nearby fluorescent species through a phenomenon known as metal enhanced fluorescence (MEF). MEF originates from the localized surface plasmon resonance (LSPR), a collective oscillation of conduction-band electrons that can modify both the extinction coefficient and quantum yield of adjacent fluorescent molecules/species. [1] The extinction coefficient is a function of the electromagnetic field intensity experienced by the fluorescent molecules, and under an enhanced electromagnetic field, fluorescent molecules absorb photons and promote electrons into excited states at accelerated rates. LSPR of metallic nanostructures can also modify the quantum yield of fluorescent species by increasing their radioactive decay rate. The combined enhancement of extinction coefficient and quantum yield can result in significantly strengthened fluorescence from fluorescent species.

Plasmonic nanosponges

“…This is relevant for the application of SERS in which the nonlinear optical processes are strongly amplified [13,14]. This is also relevant for the enhancement of fluorescence [15]. Furthermore, strongly enhanced nonlinear light scattering, such as second-harmonic generation (SHG) scattering, has also been experimentally observed [16].…”

Nanostructure Introduces Artifacts in Quantitative Immunofluorescence by Influencing Fluorophore Intensity

“…Enhancements in fluorescence intensity caused by the presence of strong LSPRs have been previously reported on np-Au films 30 . However, previous studies have primarily focused on surface functionalized nanometer sized fluorescent species such as quantum dots or unconjugated fluorescent dyes 30–33 .…”

Recent advances in plasmonic nanostructures for sensing: a review

“…The resulting intense electric field generated at the hot spot between the two nanospheres results in large MEF enhancement factors and the surrounding box provides an efficient reflector for backscatter collection of the signal. 160,156 By changing the nominal diameter of the nanosphere dimer particles, the optimal plasmon absorption wavelength can be easily changed to match a particular fluorophore. Arraying such a nanoantenna in boxes across a substrate can allow for rapid multiplexed analyses of many samples with single-molecule detection sensitivities.…”

“…Arraying such a nanoantenna in boxes across a substrate can allow for rapid multiplexed analyses of many samples with single-molecule detection sensitivities. 160,156 Another form of nanohole/nanopore array [see Fig. 11(d)] that has recently been employed for MEF sensing applications involves the use of AAO arrays, in which nanoholes bored in the AAO material provide the nanostructured surface for plasmon oscillation as well as pores for potential incorporation into microfluidic devices.…”