Luminescent Silica Core/Silver Shell Encapsulated with Eu(III) Complex

Abstract

In this paper we studied the metal-enhanced emission from long-lifetime lanthanide dyes that were encapsulated in the silver nanoshells. The metal nanoshells were synthesized with the silica spherical cores of 50 nm diameters and the silver shells of 5 -60 nm. The optical properties of luminescent metal shells were performed on the either ensemble fluorescence spectroscopy or single particle imaging. The emission intensity from the encapsulated lanthanides was observed to enhance significantly by the metal nanoshell. The enhancement efficiency initially increased with the metal shell thickness and then decreased. The maximal enhancement occurred at the 20 -30 nm thickness. The lifetime of encapsulated Eu(III) complexes was shorten dramatically indicating that they were coupled efficiently with the metal shells. The increased brightness and reduced lifetime of this coreshell structure demonstrate that the lanthanides are favorable for the single target molecule detections after encapsulating into the metal nanoshells.

Detection of CXCR4 receptors on cell surface using a fluorescent metal nanoshell

“…These results were in accordance to the observations in our previous report. [26][27][28] The organic monolayers on the metal nanoshells were partially substituted by the terminal-carboxylate ligands via ligand exchange. 30 Then, anti-CXCR4 mAb molecules were covalently bound on the metal nanoshell surfaces via condensation.…”

“…As a result, the fluorophores throughout the core can be coupled equally and efficiently with the interior uniform field, leading to greatly enhanced fluorescence. [26][27][28] Importantly, the near-field interaction of the fluorophore with the metal nanostructure can increase the radiative rate of a fluorophore, which may increase the intrinsic decay rate of fluorophores, leading to a dramatic reduction in lifetime. 18 Therefore, these metal nanoshells can be developed as the time-resolved fluorescent probes in the lifetime cell imaging.…”

Target molecule imaging on tissue specimens by fluorescent metal nanoprobes

“…13,14 There were approximate 100 Ru(bpy) 3 2 + complexes incorporated into a single silica core. To improve the chemical stability of FMNs in buffer solution and reduce their nonspecial conjugations with the tissue specimens, we coated FMNs with monolayers of polyethylene glycol (PEG)-like ligands.…”

“…Typically, these metal nanoprobes are designed in two configurations: metal nanospheres with fluorophores immobilized on external layers 12 and metal nanoshells with fluorophores within cores. 13,14 Both configurations were found to display improved optical properties, and their emission signals were observed to be distinctly distinguishable in the cell images. 15,16 We are particularly interested in the metal nanoshells because there are uniform and intensive electric fields throughout core areas, [17][18][19] and thus the dyes in the cores can be interacted efficiently with metal plasmon resonances, leading to great improvements on their optical properties.…”

Enhancement of the decay rate by plasmon coupling for Eu 3+ in an Au nanoparticle model system

“…Control over the coupling between the emitter and the metal structure is provided by tuning the overlap between the plasmon resonance and the emission wavelength. More recently, studies have appeared where the distance dependence of plasmon resonance enhancement was studied for lanthanide complexes and silver nanoparticles of silver island films [29,30]. In this paper we will present a model system to investigate the plasmon coupling for Ln 3+ emission, in which the distance between the Ln 3+ ion and the metal particle can be tuned.…”