A new approach towards controlled synthesis of multifunctional core-shell nano-architectures: luminescent and superparamagnetic

We have developed a two-step method for synthesis of multifunctional core-shell nanoparticles with an improved structure as compared with those prepared by traditional methods used independently. The nanoparticles comprise a superparamagnetic core, an inner insulating dye-free silica shell, an outer luminescent silica shell encapsulating thousands of dye molecules and a functionalizeable surface. The innovative insertion of the isolating silica shell benefits the nanoparticles' architecture in two ways. Firstly, by keeping the dye molecules away from the magnetic core, the silica shell prevents dye luminescence quenching. Secondly, the non-magnetic shell decreases magnetic interparticle coupling, which, by reducing aggregation and preventing agglomeration, facilitates the formation of the high-quality luminescent shell in the second step of the process. The final nanoparticles being both superparamagnetic and luminescent have a great potential for theranostic applications such as ultra-sensitive detection, and in-vitro and in-vivo imaging.