Seed-mediated synthesis, properties and application of γ-Fe2O3–CdSe magnetic quantum dots

Seed-mediated growth of fluorescent CdSe quantum dots (QDs) around γ-Fe2O3 magnetic cores was performed at high temperature (300 °C) in the presence of organic surfactants. Bi-functional magnetic quantum dots (MQDs) with tunable emission properties were successfully prepared. The as-synthesized MQDs were characterized by high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS), which confirmed the assembly of heterodimers. When a longer growth period was employed, a homogeneous dispersion of QDs around a magnetic nanoparticle was obtained. The magnetic properties of these nanocomposites were examined. The MQDs were superparamagnetic with a saturation magnetization of 0.40 emu/g and a coercivity of 138 Oe at 5 K. To demonstrate their potential application in bio-labeling, these MQDs were coated with a thin silica shell, and functionalized with a polyethylene glycol (PEG) derivative. The functionalized MQDs were effectively used for the labeling of live cell membranes of 4T1 mouse breast cancer cells and HepG2 human liver cancer cells.

(a) HRTEM image of oleic acid capped MPs. The size of MPs ranges from 8 to 10 nm. (b) XRD pattern of γ-Fe2O3 MPs.Figure optionsDownload as PowerPoint slideHighlights
► The fabrication of MQDs through a seed-mediated approach has been demonstrated.
► The formation and assembly of these bi-functional nanocomposites have been elucidated.
► The MQDs exhibit superparamagnetism and tunable emissions characteristic of the components.
► MQDs with thin silica coating were successfully employed in the labeling of cancer cell membranes.