SPION@SiO 2 NPs were synthesised via a reverse microemulsion method, as seen in Fig. and discussed in section 2.2.2. Through understanding the reaction mechanism, it is clear why the regression analysis determined that the experimental factors were highly dependent on each other. TEOS is clearly needed for the growth of silica shell, hence the strong linear effect for shell thickness, and monodispersity of particles formed. The NH 4 OH number of moles is responsible for both the hydrolysis of TEOS and the quantity and size of aqueous domains (hence micelles present), therefore also exhibiting a linear effect in controlling shell thickness and monodispersity. With these interactions in mind, it is clear why the population of SPION@SiO 2 NPs is dependent on both the number of moles of TEOS and NH 4 OH.