Nanoplasmonic enhancement of single-molecule fluorescence

Abstract

We demonstrate that the fluorescence rate from a single molecule with near-unity quantum yield can be enhanced by a factor of ≈10 by use of a single laser-irradiated noble metal nanoparticle. The increased fluorescence rate is primarily the result of the local field enhancement. However, at particle-molecule distances shorter than 2 nm, nonradiative decay of the excited molecule due to energy transfer to the metal dominates over the local field enhancement giving rise to fluorescence quenching. These counteracting processes depend on the wavelength-dependent dielectric function of the particle antenna. In this study, we quantitatively compare single-molecule fluorescence enhancement near 80 nm gold and silver nanoparticles excited at a fixed wavelength of λ = 637 nm. In accordance with theory we find similar enhancements for both gold and silver nanoparticles.

Directional emission from a single plasmonic scatterer

“…Nanoantennas composed of metallic nanoparticles that support localized surface plasmon resonances (LSPRs) in the ultraviolet-visible-infrared part of the electromagnetic spectrum have been used to control spontaneous emission [2][3][4][5][6] and surface enhanced Raman scattering 7,8 , and find applications in targeted medicine 9,10 , solar steam generation 11,12 or photovoltaics 13 . In many of these applications the directionality of the plasmon scattering plays a pivotal role.…”

Dependence of the energy transfer to graphene on the excitation energy

“…In such cases the interaction between an emitter and a metallic nanostructure can be probed by monitoring decrease of donor emission intensity and shortening of its fluorescence decay. The resonant character of plasmon excitations in metallic nanostructures implies strong wavelength dependence of both metal-enhanced fluorescence and fluorescence quenching [9,11,12].…”

Fluorescence quenching/enhancement surface assays: Signal manipulation using silver-coated gold nanoparticles

“…Many immunoassays using gold nanoparticles are based on strong fluorescence quenching near the particle surface [5,22]. Larger gold nanoparticles and clusters may enhance the surface fluorescence [11,16]. Second, as a result of illumination of metallic nanoparticles by the excitation light, there is an enhanced local field.…”

“…In many cases, strong quenching of a fluorophore is observed near gold nanoparticles of 1-100 nm size [4][5][6][7]. However, in some cases no quenching [8] (at specific fluorophore orientation on the gold nanoparticle surface), or fluorescence enhancement [9][10][11] is observed. Fluorophore emission near gold particles depends on the location of the dye near the particle, the fluorophore-particle surface distance, and molecular dipole orientation versus particle surface [12][13][14].There are various effects observed on gold particles attached to a glass substrate: for example, less quenching [15] or enhancement [16].…”