Luminomagnetic Silica-Coated Heterodimers of Core/Shell FePt/Fe₃O₄ and CdSe Quantum Dots as Potential Biomedical Sensor

Abstract

We report the synthesis of a new multifunctional nanomaterial based on silica-coated FePt/Fe 3 O 4 -CdSe heteronanostructures, combining luminescent and magnetic properties in a promising bifunctional sensor for biomedical applications. Spherical Fe 3 O 4 -coated FePt (FePt/Fe 3 O 4 ) superparamagnetic nanoparticles (10.8 ± 1.5 nm) with high saturation magnetization and controlled size and shape were obtained using thermal decomposition coupled with seed-mediated growth method. Luminescent property was added to the nanomaterial by using the FePt/Fe 3 O 4 magnetic core as seed and growing the CdSe quantum dots (2.7 ± 0.6 nm) onto its surface in a heterodimer-like structure using the hot-injection approach. The FePt/Fe 3 O 4 -CdSe luminomagnetic heteronanostructures were coated with silica shell using the reverse-micelle microemulsion route to avoid solvent-quenching effects. After silica coating, the water-dispersible heteronanostructures showed a diameter of 25.3 ± 2 nm, high colloidal stability, magnetic saturation of around 11 emu g −1 , and photoluminescence in the blue-green region, as expected for potential bifunctional platform in biomedical applications. The saturation magnetization of heteronanostructures can be increased to 28 emu g −1 by annealing at 550 ∘ C due to the presence of the FePt phase.

Synthetic Approaches to Colloidal Nanocrystal Heterostructures Based on Metal and Metal-Oxide Materials

“…To pursue enhanced functionality, there have been efforts toward SiO 2 -protected CNHS systems integrating magnetic and fluorescent materials. One example is represented by a complex FePt@Fe 3 O 4 -CdSe@SiO 2 system, which was constructed starting from spherical FePt@Fe 3 O 4 core@shell CNHSs [ 162 ]. The heterostructure seeds were first decorated with tiny CdSe nanocrystal satellites and then coated with SiO 2 shell in a reverse-micelle microemulsion to minimize solvent-induced quenching of the CdSe photoluminescence [ 162 ].…”