Modification of the Stober Process by a Polyazamacrocycle Leading to Unusual Core−Shell Silica Nanoparticles

In the view of designing functional nanoparticles, the encapsulation of 1,4,7,10-tetraazacyclododecane (cyclen) within silica nanoparticles using the Stöber process was studied. In the presence of cyclen and tetraethoxysilane (TEOS), silica particles exhibiting an unusual core?shell structure were obtained. On then basis of TEM, DLS, and NMR data, we suggest that the particle core is constituted of hybrid primary nanoparticles resulting from cyclen?silica interactions, whereas the shell formation results from further condensation of unreacted silica precursors. Control experiments performed with the zinc?cyclen complex and ammonia addition suggest that cyclen?TEOS interactions arise from the activation of the silicon alkoxide hydrolysis with the polyazamacrocycle amine groups. These data are discussed in the context of silica biomineralization mechanisms, where polyamine/silica interactions have been shown to play a major role. Moreover, the possibility to control the size and the structure of these nanoparticles makes them promising materials for pharmaceutical applications.