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 with diameters of 50 nm and the silver shells of 5−60 nm. The optical properties of the luminescent metal shells were determined by either the ensemble fluorescence spectroscopy or the single-particle imaging. The emission intensity from the encapsulated lanthanides was observed to be enhanced 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 shortened 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 encapsu...