Magnetic nanoparticle engineering, characterization and their use as an emulsion stabilizer is the focal point of this research and dissertation. Their magnetic properties enable remote manipulation of particle’s motion. In this research pH-responsive Fe3O4 nanoparticles were synthesized using a chemical co-precipitation method and consequently used to stabilize Pickering emulsions. Oleic acid was used to modify the nanoparticle surface to tailor their wettability as well as pH responsiveness as a consequence of deprotonation/protonation of carboxylic group. It was found that the oleic acid arranges in bilayer structure at pH higher than 8 but remains as a monolayer at pH lower than 7. This change in structure alters the wettability of particle with a change in pH. The nanoparticles were characterized in terms of particle morphology, size distribution by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometer, thermo-gravimetric analysis (TGA) and zeta potential. Bilayer stabilized magnetic nanoparticles were suitable for preparing Pickering emulsions. The stability of emulsion was dependent on pH with stable emulsions forming at pH higher than 10. The rheological studies were done to understand the flow behavior of emulsions. Emulsions with higher weight percentage of nanoparticles were found to be the least stable due to decrease in pH of aqueous phase. The decrease in pH and consequent lower stability of emulsions was due to oxidation of bare Fe3O4 nanoparticle in alkaline medium. These findings are applicable in applications such as enhanced oil recovery, liquid phase heterogeneous catalysis, emulsion polymerization, and biomedicine where control destabilization of Pickering emulsion is required. Emulsion droplets can be directed using an external magnetic field and emulsions can also be destabilize by changing the pH of the aqueous phase. Since the particle are magnetic, they can be recovered in presence of external magnetic field after the separation of phases of emulsion.