Delayed Photoluminescence in Metal-Conjugated Fluorophores

Abstract

Assemblies of metal nanostructures and fluorescent molecules represent a promising platform for the development of biosensing and near-field imaging applications. Typically, the interaction of molecular fluorophores with surface plasmons in metals results in either quenching or enhancement of the dye excitation energy. Here, we demonstrate that fluorescent molecules can also engage in a reversible energy transfer (ET) with proximal metal surfaces, during which quenching of the dye emission via the energy transfer to localized surface plasmons can trigger delayed ET from metal back to the fluorescent molecule. The resulting two-step process leads to the sustained delayed photoluminescence (PL) in metal-conjugated fluorophores, as was demonstrated here through the observation of increased PL lifetime in assemblies of Au nanoparticles and organic dyes (Alexa 488, Cy3.5, and Cy5). The observed enhancement of the PL lifetime in metal-conjugated fluorophores was corroborated by theoretical calculations based on the reverse ET model, suggesting that these processes could be ubiquitous in many other dye− metal assemblies.

Ambient Tip-Enhanced Photoluminescence with 5 nm Spatial Resolution

“…Another possibility is the nonradiative energy transfer from a QD to the Au probe. This process is known to cause a red-shift in the PL of organic dyes anchored to Au NPs but only when dye excitons were lower in energy than the surface plasmon resonance of a metal nanoparticle. Unlike the charge transfer process, the rate of QD-to-Au energy transfer is not directly proportional to the QD-Au tip distance.…”

Energy Transport in CsPbBr3 Perovskite Nanocrystal Solids

“…STEP spectroscopy − was recently developed for measurements of the donor → acceptor energy transfer efficiency, E D → A . It is based on the assumption that the number of photons emitted by an acceptor fluorophore, N A PL , depends linearly on the number of excited acceptor (A) and donor (D) molecules, N A and N D , respectively: where QY A is the emission quantum yield of the fluorophore A in the presence of the donor D (as measured in the donor–acceptor assembly).…”

Silver Nanoparticles Functionalized by Fluorescein Isothiocyanate or Rhodamine B Isothiocyanate: Fluorescent and Plasmonic Materials

“…The interaction of fluorophores with Au and Ag NPs is slightly more complicated, and both enhancement and quenching of fluorophores have been reported [29][30][31][32][33]. Part of the reason for this apparent contradiction is that the interaction between fluorophores and the NP depends on the size and shape of the NPs, the distance of the fluorophore from the surface of the NPs, the orientation of the fluorophore dipole moment, and the overlap between the emission spectrum of the fluorophore and the plasmon resonance spectral feature of the NP [34][35][36].…”