Remarkable Influence of Silver Islands on the Enhancement of Fluorescence from Eu3+ Ion-Doped Silica Gels

A simple methodology has been developed to enable a greater enhancement of fluorescence from europium (Eu3+)-doped silica gels containing adsorbed silver (Ag) islands. The procedure involves the preparation of Eu3+-doped silica gels by a sol−gel method and then immersion in a Ag sol for ca. 48 h to allow the adsorption of Ag islands on the pore surfaces of silica gels. UV−vis spectra show the characteristic surface plasmon resonance of the Ag at around 390 nm, and transmission electron microscopy (TEM) presents Ag islandlike particles on the surface of silica gels. The photoluminescence studies reveal the fact that the enhanced fluorescence originates from the local field enhancement around Eu3+ ions, caused by the electronic plasmon resonance of the Ag islands.