A facile method for the preparation of bifunctional Mn:ZnS/ZnS/Fe(3)O(4) magnetic and fluorescent nanocrystals

Bifunctional magnetic and fluorescent core/shell/shell Mn:ZnS/ZnS/Fe(3)O(4) nanocrystals were synthesized in a basic aqueous solution using 3-mercaptopropionic acid (MPA) as a capping ligand. The structural and optical properties of the heterostructures were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), UV–vis spectroscopy and photoluminescence (PL) spectroscopy. The PL spectra of Mn:ZnS/ZnS/Fe(3)O(4) quantum dots (QDs) showed marked visible emission around 584 nm related to the (4)T(1) → (6)A(1) Mn(2+) transition. The PL quantum yield (QY) and the remnant magnetization can be regulated by varying the thickness of the magnetic shell. The results showed that an increase in the thickness of the Fe(3)O(4) magnetite layer around the Mn:ZnS/ZnS core reduced the PL QY but improved the magnetic properties of the composites. Nevertheless, a good compromise was achieved in order to maintain the dual modality of the nanocrystals, which may be promising candidates for various biological applications.