Adsorption and encapsulation of fluorescent probes in nanoparticles

Silica "nanobubbles" are hollow spheres of silica that can be used as nanom eter-sized containers for probe molecules. A method for the encapsulation o f a fluorescent molecule into silica "nanobubbles" is reported. Fluorescein isothiocyanate (FITC) dye molecules were coadsorbed onto the surface of go ld nanoparticles with 3-aminopropyltrimethoxysilane. Following silica conde nsation, and dissolution of the gold core, the fluorescent molecules remain inside the water-filled, but sealed, silica nanoparticle. The plasmon band of the gold particles and the absorption and fluorescence spectra of the d ye are affected by adsorption of the molecule on the gold particle. Encapsu lation in the silica nanobubble insulates the dye molecule from the externa l environment. Analogous methods can be applied to a wide range of probes.