Fluorescent core-shell Ag@SiO2 nanocomposites for metal-enhanced fluorescence and single nanoparticle sensing platforms

We report the development of highly versatile highly fluorescent and photostable core-shell Ag@SiO2 nanocomposites, which allows researchers the flexibility to incorporate just about any fluorophores to the outer silica shell by two simple methods. To show the generality of the preparation technique, we have developed three different fluorescent probes: an organic fluorophore (Rh800) and a lanthanide probe doped (noncovalently linked) and an organic fluorophore (Alexa 647) covalently linked to the silica shell. When compared to the control fluorescent nanoparticles (nanobubbles), fluorescent nanoparticles with silver core-silica shell architecture yielded up to 20-fold (with Rh800) enhancement of the fluorescence signal. In terms of nanoparticle detectability for sensing and cellular imaging applications, a 20-fold increase in fluorescence intensity coupled with a 10-fold drop in lifetime affords a total increased detectability of similar to 200-fold as compared to the control sample nanobubbles containing the same number of fluorophores. The size, shell thickness, and color of the new MEF-nanoparticles can be easily controlled and optimized for a variety of biological applications, such as cellular entry, imaging, and localization.