In Situ Aggregation of ZnSe Nanoparticles into Supraparticles: Shape Control and Doping Effects

The ability to tune the size, shape, and properties of supraparticles is of great importance for fundamental study as well as their promising applications. We previously developed a method to synthesize monodisperse ZnSe supraparticles via “in situ aggregation” of ZnSe nanoparticles through a simple hot-injection method. In the present work, we show that the “in situ aggregation” strategy can be extended to tune the shapes of ZnSe supraparticles, and introduce novel functional magnetic and luminescence properties. Shape control is manipulated with oleic acid as ligands, which balances the attractive interparticles van der Waals forces and steric repulsive forces from the ligands. With the increase of oleic acid concentration, a morphology change from microspheres to asymmetrical multimer and three-dimensional nanoflowers was observed. “Doping” preformed Fe<sub>3</sub>O<sub>4</sub> nanoparticles into ZnSe supraparticles endow them with magnetic properties. The magnetism of these Fe<sub>3</sub>O<sub>4</sub>@ZnSe supraparticles depends on the dosage of dopant. Doping of preformed CdS nanocrystals was also studied, resulting in emissive hybrid CdS@ZnSe supraparticles with diameters of 50–100 nm. It is noted that the doping of Fe<sub>3</sub>O<sub>4</sub> and CdS nanoparticles show differing morphologies. The differences can be explained by variance in the lattice mismatches which leads to differing potentials for crystal growth.