Fluorescent Magnetic Nanocrystals by Sequential Addition of Reagents in a One-Pot Reaction:  A Simple Preparation for Multifunctional Nanostructures

Core−shell nanostructures consisting of FePt magnetic nanoparticles as the core and semiconducting chalcogenides as the shell were synthesized by a series of reactions in a one-pot procedure. Adding Cd(acac)₂ as the cadmium precursor to a reaction mixture containing FePt nanoparticles afforded FePt@CdO core−shell intermediates. The subsequent addition of chalcogens yielded FePt@CdX core−shell nanocrystals (where X was S or Se). The reverse sequence of addition, i.e., adding X before Cd, resulted in spongelike nanostructures because the chalcogens readily formed nanowires in the solution. Transmission electron microscopy, energy-dispersive X-ray spectrometry, selected area electron diffraction, fluorescence spectroscopy, and SQUID were used to characterize the nanostructures. These core−shell nanostructures displayed superparamagnetism at room temperature and exhibited fluorescence with quantum yields of 2.3−9.7%. The flexibility in the sequence of addition of reagents, combined with the compatibility of the lattices of the different materials, provides a powerful yet convenient strategy for generating sophisticated, multifunctional nanostructures.