Plasmon-controlled fluorescence: a new paradigm in fluorescence spectroscopy

Abstract

Fluorescence spectroscopy is widely used in biological research. Until recently, essentially all fluorescence experiments were performed using optical energy which has radiated to the far-field. By far-field we mean at least several wavelengths from the fluorophore, but propagating far-field radiation is usually detected at larger macroscopic distances from the sample. In recent years there has been a growing interest in the interactions of fluorophores with metallic surfaces or particles. Near-field interactions are those occurring within a wavelength distance of an excited fluorophore. The spectral properties of fluorophores can be dramatically altered by near-field interactions with the electron clouds present in metals. These interactions modify the emission in ways not seen in classical fluorescence experiments. In this review we provide an intuitive description of the complex physics of plasmons and near-field interactions. Additionally, we summarize the recent work on metal-fluorophore interactions and suggest how these effects will result in new classes of experimental procedures, novel probes, bioassays and devices.

Tunable Nanowrinkles on Shape Memory Polymer Sheets

“…9-fold decrease in average lifetime suggests that enhancement results from strong interactions between the fluorophore and surface plasmons. [27] In addition, the shorter and longer lifetimes may be attributed respectively to the strongly (bright) and weakly (dim) enhanced regions (Fig. 3c, bottom).…”

“…This technique utilizes metallic nanostructures in which the plasmons resonate with the fluorophores to reduce their excited state lifetimes and simultaneously increase their fluorescence emission intensities. [27] Silver island films are often used to meet such a requirement, and the typically ca. 10-fold enhancement has been applied to improve detection of DNA hybridization [28] and immunoassay.…”

“…2-7. [27,30] Recently, utilization of ''continuous'' gold nanometer-scale features to improve the density of hotspots has been studied; typically, a ca. 0.5-to 5-fold increase of the fluorescence intensity can be achieved.…”

“…For instance, for further studies on multiple-probe MEF, these properties make it possible to adjust broad SPR bands to overlap well with various absorption bands of fluorophores. [27] In addition, our approach is considerably faster and significantly less expensive and more robust than other means of achieving such size-controllable nanometer-scale structures (including nanosphere lithography, focused ion beam lithography, and electron-beam lithography). [27] A significant enhancement of fluorescence intensity, together with the high throughput and fine microfluidic control over reagents with lab-on-chip techniques, makes the nanowrinkles promising low-cost substrates for ultrasensitive and ultrafast detection for biomedical applications.…”

Observation of Selective Plasmon-Exciton Coupling in Nonradiative Energy Transfer: Donor-Selective versus Acceptor-Selective Plexcitons

“…In the case of FRET in D−A QD pairs (as in Figure 2a), the emission enhancement factor for the donor and acceptor is given by (details are in Supporting Information: FRET in QDs pair) where γ D(A),exc is the exciton recombination rate of the donor (acceptor) and γ NRET = γ D,exc (R 0 /r) 6 is the Forster-type D−A transfer rate. Here, R 0 is the Forster radius, 27 and r is the separation distance between the D and the A. Parameters used in these calculations are provided in the Supporting Information: Numerical Results.…”