Synthesis of superparamagnetic silica composites with europium doping For fluorescence

Superparamagnetic particles have attracted a lot of interest due to their relatively high saturation magnetization, zero remanence and zero coercivity. These properties render such particles suitable for a range of applications, such as cell sorting and targeted drug delivery. In this study, superparamagnetic silica composites embedded with europium (Eu) were successfully synthesised using a modified combination from published methods (Tan et al. 2004; He et al. 2007). The functionalisation of magnetic nanoparticles through the addition of a fluorescent element will help extend the particle uses in imaging applications (i.e. bio-markers). The superparamagnetic magnetite (Fe3O4 ) particles of 20nm size were prepared via co-precipitation of iron salts. The magnetite particles were then coated with silica by the sol-gel Stober method in a microemulsion. To produce fluorescent particles, a conjugate of europium (Eu) chelate was added to the microemulsion, thus covalently binding Eu onto the silica during the process. Eu can fluoresce at an excitation wavelength of 355nm and an emission wavelength of 610nm, while the covalent bonding should prevent problems associated with toxicity and leakage commonly encountered with encapsulation of fluorescent dyes. The particles were shown to demonstrate both superparamagnetic and fluorescent properties, making them potential candidates for biomedical applications such as imaging, cell sorting, or targeted drug delivery. Future works include optimising their functionality by adjusting the synthesis conditions.