Distance-Dependent Plasmon-Enhanced Fluorescence of Submonolayer Rhodamine 6G by Gold Nanoparticles

Abstract

We investigate the fluorescence from submonolayer rhodamine 6G molecules near gold nanoparticles (NPs) at a well-controlled poly (methyl methacrylate) (PMMA) interval thickness from 1.5 to 21 nm. The plasmonic resonance peaks of gold NPs are tuned from 530 to 580 nm by the PMMA spacer of different thicknesses. Then, due to the plasmonic resonant excitation enhancement, the emission intensity of rhodamine 6G molecules at 562 nm is found to be enhanced and shows a decline as the PMMA spacer thickness increases. The variation of spectral intensity simulated by finite-difference time-domain method is consistent with the experimental results. Moreover, the lifetime results show the combined effects to rhodamine 6G fluorescence, which include the quenching effect, the barrier effect of PMMA as spacer layer and the attenuation effect of PMMA films.

One-Pot Synthesis of Silica-Coated Gold Nanostructures Loaded with Cyanine 5.5 for Cell Imaging by SERS Spectroscopy

“…The dependence of fluorescence quenching on the distance between the fluorophore molecule and plasmon core was studied earlier. In particular, it was shown for nanorods that fluorescence quenching is limited by a distance of approximately 2 nm from the core [ 4 , 28 ]. Performing three purifications at nanotag preparation (replacement of isopropanol with water, purification from excess APTES, and removing the excess unbound folic acid) guarantees that the observed fluorescence signal comes precisely from cyanine 5.5 amine incorporated into the silica shell but not from the fluorophore remaining in the solution.…”

“…Despite plasmonic nanoparticles are more sophisticated and multipurpose agents, their use in fluorescence spectroscopy remains questionable due to the quenching effect competing with the electromagnetic enhancement. The relationship between these effects strongly depends on the distance between the fluorophore and the plasmonic core [ 4 , 5 , 6 ]. Usually, fluorescence is quenched when the distance between the fluorophore and metal core is less than 2–5 nm and complete disappearance of the emission can be observed directly on the surface.…”

Highly Stable Polymer Coating on Silver Nanoparticles for Efficient Plasmonic Enhancement of Fluorescence

“…Alkanethiol and DNA , molecules are other candidates for the spacer material. Furthermore, polymer shells − possess practical advantages in terms of chemical stability, excellent compatibility in a polymer matrix, and versatility of surface modification for the conjugation of a variety of molecules including biomolecules and dyes. The polymer shells are usually formed with coupling agents and multiple steps, which requires one to properly select the coupling agents and optimize parameters.…”

Combined effects of emitter–emitter and emitter–plasmonic surface separations dictate photoluminescence enhancement in a plasmonic field

“…43 Similarly, PL enhancement in the presence of a plasmonic field has been explored recently by various groups. 29,31,42,[44][45][46][47][48][49][50][51][52][53][54] Some of these reports include: (i) theoretical demonstration indicating that the enhancement is higher when one emitter is placed on a metal surface compared to three emitters which drops with t; 44 (ii) experimental studies using IRDye800 bound on silica coated Au nanorods which exhibit a PL enhancement of 10-fold at t = 17 nm and when the dye-plasmon spectral overlap is maximum; 31 (iii) observations that the field enhancement is predominant over other nonradiative processes when CdSe quantum dots (QDs) are densely packed on silica coated Au nanoparticles at large t; 45 (iv) investigation on the role of the local orientation of the dye molecule and local electric field intensity contour around Au nanorods in MEF using single-molecule fluorescence measurements 42 and (v) the role of excitation wavelength in MEF using CdSe QDs bound on Ag nanoparticles. 46 The density of emitters on the nanoparticles' surfaces which controls their nearestneighbour separations (represented as 's') is yet another crucial factor affecting the PL characteristics.…”