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

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 core-shell structure demonstrate that the lanthanides are favorable for the single target molecule detections after encapsulating into the metal nanoshells.