(89f) Flame Aerosol Synthesis of Functional Composite Nanoparticles

Magnetic and fluorescent composite nanoparticles are useful for biomedical imaging applications. Flame aerosol synthesis may be used for the manufacturing of such nanoparticles, with advantages such as simplicity and high energy efficiency. However, producing the desired particle properties in flame aerosol synthesis may prove challenging. In flame aerosol synthesis, both thermodynamics and kinetics play an important role. Better understanding of these factors would greatly improve our ability to design efficient routes for the synthesis of smart nanoparticles.

In this study, flame aerosol processes were used to synthesize M-SiO₂ composite nanoparticles (M=Fe, Eu, Tb, Dy, Tm). These particles are characterized by TEM, XRD, and fluorescence spectroscopy. The Fe/SiO₂ nanoparticles contain separate phases of amorphous SiO₂ and crystalline gamma-Fe₂O₃. The lanthanides exist in the silica matrix as a separate amorphous phase. All lanthanide/silica particles are fluorescent, with photoluminescence peak wavelength at 544, 574, 616, and 657 nm (Tb, Dy, Eu and Tm respectively). The particles generally do not have a core-shell structure. The iron- or lanthanide-rich phases randomly distribute in the silica matrix. When on the edge of the nanoparticles, these phases may be dissolved in 4% sulfuric acid at room temperature.

In conclusion, flame aerosol synthesis can be used to generate silica-based composite nanoparticles for magnetic or fluorescent properties. These particles can be potentially used in biomedical imaging. However, with this method making core-shell structures with full encapsulation by silica remains a challenge. The toxicity of these particles needs to be examined before they can be used in biomedical applications.