A general method for the controlled embedding of nanoparticles in silica colloids.

A novel method for the controlled embedding of multiple nanoparticles of various materials, such as gold nanoparticles, quantum dots, and magnetic nanoparticles, in silica colloids is presented. After adsorption of the amphiphilic polymer poly(vinylpyrrolidone) on hydrophobic or hydrophilic stabilized nanoparticles, these are adsorbed on silica spheres and covered by variable-thickness silica shells. This silica coating protects the embedded nanoparticles against chemical transformations, which is of crucial importance for the biocompatibility of particles containing toxic elements. Moreover, it is found that the optical properties of the nanoparticles are retained. Possible applications of multicore particles are briefly discussed.