Superparamagnetic particles have attracted a lot of interest since they could respond strongly to an external magnetic field, and returning to zero remanence and coercivity in the absence of the magnetic field. To produce such particles, a high control of particle size during synthesis is needed. Further functionalization of the particles by the addition of a fluorescent element will make them suitable for a range of biomedical applications such as imaging, cell sorting, or targeted drug delivery.

In this project, superparamagnetic magnetite nanoparticles were prepared via the co-precipitation method of iron salts, followed by silica coating by a sol-gel Stober method in a microemulsion. This method was chosen to allow for a greater control of particle size whilst ensuring that discrete particles are created, as opposed to a series of particles inter-connected by a silica matrix. Further silanisation of the particles by an amino silane bound to a conjugate of europium chelate was conducted to covalently attach the europium on the outer silica layer of the particle. With this approach, the problems of toxicity and leakage often encountered with the use of conventional fluorescent dyes can be minimised. The functionality can be optimized by characterizing the magnetic and fluorescent properties of particles synthesized at different precursor ratio.