## 2 Preparation of Magnetic-Fluorescent Nanocomposites
### Fluorescent Polymer Coated Magnetic Nanoparticles
#### 2.2.3 Polymer and QDs-Magnetic-Fluorescent Nanocomposites  
A range of fluorescent-magnetic nanocomposites have also been prepared by using different sized quantum dots and varying amounts of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) magnetic nanoparticles into poly(styrene/acrylamide) copolymer nanospheres. The fabrication of the multifunctional nanospheres involved the incorporation of the quantum dots and \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) nanoparticles into the copolymer [55]. The encapsulation of both magnetic and infrared emitting nanoparticles into a polymeric matrix leads to a magnetic-fluorescent hybrid nanostructure with multimodal magnetic-fluorescent imaging abilities (Figure 6). The nanostructures were prepared by combining nontoxic iron superparamagnetic nanoparticles with PbS quantum dots through encapsulation with the biocompatible polymer poly(lactic-_co_-glycolic-acid) [56]. Hydrophobic trioctylphosphine oxide (TOPO)-capped CdSe@ZnS quantum dots (QDs) were assembled on polyethyleneimine (PEI)-coated Fe\({}_{3}\)O\({}_{4}\) nanoparticles [57]. Figure 5: Surface Modification Process of Superparamagnetic Fe\({}_{3}\)O\({}_{4}\) Nanoparticles. Adapted from ref. [46]. In another study, superparamagnetic Fe\({}_{3}\)O\({}_{4}\) NPs and visible light emitting fluorescent CdTe/CdS quantum dots were conjugated using the covalent linking of the oxidized dextran shell of magnetic particles to the glutathione ligands of QDs [58]. Hydrophobic trioctylphosphine oxide-capped CdSe/ZnS quantum dots (QDs) and oleic acid-capped nano-\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) magnetic particles are directly, selectively and controllably assembled on branched poly(ethylene imine)-coated nanospheres without  
Figure 6: Top: Characterization of luminescent-magnetic HNS. (**a**) Compositional analysis (EDX) of a PLGA nanostructure denoting the presence of elements of both magnetic NPs and QDs. (inset) Schematic diagram of the magnetic NPs and QDs in the PLGA nanostructure; (**b**) TEM image of a typical PLGA nanostructure synthesized in this work; (**c**) A detailed TEM image of a PLGA nanostructure revealing the presence of two types of NPs inside the structure; (**d**) Size distribution of both types of particles obtained from TEM images. The size distribution corresponds to the sizes of the magnetic NPs and QDs (right). Fluorescence analysis; (**e**) Infrared fluorescence images of a PBS solution containing the HNS, as obtained under 808 nm laser excitation and by employing different long pass filters; (**f**) Emission spectrum of HNS; (**g**) IR fluorescence images of the same dispersion in the presence of a magnet, demonstrating the potential for the magnetic control of the nanostructures while enabling visual tracking through the IR luminescence. Adapted from [56]. any pre-treatment. This is crucial in keeping the high quantum yield of QDs and the good dispersibility of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)[59]. Magnetic core/shell Fe\({}_{3}\)O\({}_{4}\)/ZnSe NPs with a spherical shape were prepared by an organometallic synthesis. The 7 nm core/3 nm shell NPs show good magnetic and photoluminescence (PL) responses [60]. [PERSON] et al. prepared nanocontainers composed by polymeric micelles with hydrophobic core into which quantum dots or rods and superparamagnetic iron oxide nanoparticles were encapsulated [61]. QDs with emissions in the near-infrared range (\(\sim\)800 nm) are conjugated onto the surface of a nanocomposite consisting of a spherical polystyrene matrix (\(\sim\)150 nm) and the internally embedded, high fraction of superparamagnetic Fe\({}_{3}\)O\({}_{4}\) nanoparticles (\(\sim\)10 nm). For drug storage, the chemotherapeutic agent paclitaxel (PTX) is loaded onto the surfaces of these composite multifunctional nanocarriers by using a layer of biodegradable poly(lactic-\(\infty\)-glycolic acid) (PLGA), see Figure 7[62]. Superparamagnetic iron oxide nanoparticles (SPIO) and near-infrared fluorescent CdTe quantum dots (QDs) were covalently coupled onto the surface of CNTs in sequence via LBL assembly (Figure 8) [63].