Bifunctional nanostructures composed of fluorescent core and metal shell subdomains with controllable geometry

Here, we describe novel composite nanoparticles composed of highly emissive fluorophore-doped silica cores and hemispherical gold-coatings, separated by spectroscopically inert silica spacer layers. Photoluminescence (PL) measurements at the single particle level demonstrated that the addition of the spacer layer effectively reduces the core PL quenching by the gold layer, rendering both constituents of the multicomponent nanostructure optically active. The versatility of this approach is further demonstrated by synthesizing analogous gold-coated nanoparticles based upon commercial fluorescent polymer nanoparticles. These multilayered nanoparticles were designed to combine the properties of fluorescent nanoparticles with the useful surface properties of gold, and such species could find utility in a wide range of biosensing applications. We have demonstrated that the hemispherical gold surfaces of these multilayered particles can be readily functionalized with DNA and the DNA-modified hybrids recognize cDNA strands without the problem of nonspecific bindings, showing promise for their use in DNA detection applications.