A study was conducted to demonstrate a novel core/shell nanosphere with a poly(vinyl pyrrolidone (PVP)-modified silica core followed by a functional deposition of a single-crystal iron oxide shell. Such a core/shell nanosphere offers unique controlled release and nonrelease behavior for molecules encapsulated inside the silica core. The dense, single crystalline shell is efficiently preventing the fluorescence dye from undesired release, given that an undesirable leakage of the molecule during the course of delivery is completely inhibited. The molecules encapsulated in the core can be released in a highly controllable manner through the use of a magnetic stimulus. The study also suggests that these core/shell nanospheres are expected to play a significant role in the development of a new generation of site-specific controlled-release drug delivery nanodevices.