Magnetic Janus Particle: Synthesis, Applications and Flow Behaviour in Suspensions and Pickering Emulsions
Creators: name: Habibi, Samin
Publisher: name: Schulich School of Engineering
Year: 2024
Subjects: subject: Magnetic Janus Particle
subject: Dual Surface Functionality
subject: Pickering Emulsion
subject: Electroless Deposition
subject: Chromium (VI) Adsorption
subject: Phenol Degradation
subject: Nucleic Acids Separation
subject: Magnetic Particles
subject: Magnetite
subject: Core/shell
subject: Magnetorheology
subject: Janus Magnetic Particle
subject: Stimuli-responsive Emulsion
subject: Stabilization
subject: Destabilization
subject: Bulk Rheology
subject: Interfacial Rheology
subject: Engineering--Chemical

description: Particles’ unique properties and versatility make them a valuable tool in the development of new materials, technologies, and applications, contributing to advancements in science, industry, medicine, etc. Engineering nanoparticles provide opportunities for innovation, addressing challenges, and creating more efficient and sustainable solutions. The possibility of multiple properties encapsulated within a single colloidal particle is of greatest importance in enabling diverse and multifunctional applications across various industries. Magnetic Janus particles can effectively integrate four properties including amphiphilicity, surface multi-functionality, anisotropy, and magnetic-responsive characteristics in a single particle. Magnetic Janus particles, with their unique combination of properties, hold great promise for a wide range of technological applications, including microprobes, micromotors, delivery carriers, etc. In this thesis, we identified the major issues of the common methodologies currently used for fabricating magnetic Janus particles. Focusing on the magnetic Janus particle synthesis challenges, we implemented a new facile, scalable, and simple approach for magnetic Janus particle fabrication. The Electroless deposition technique was employed to create an iron oxide shell on the surface of silica particles. This technique was then further manipulated and combined with the Pickering emulsion method to selectively shield a portion of the silica particles and create magnetic Janus particles by decorating just the exposed area with the iron oxide shell. As a result, we successfully synthesized two distinct varieties of particles featuring iron oxide core/shell (SiO2@Fe3O4) and iron oxide Janus particles (SiO2@NH2&amp;Fe3O4). The dual surface functionality of the SiO2@NH2&amp;Fe3O4 Janus particle was tested in multi-compound removal from aqueous solution and compared to corresponding SiO2@Fe3O4 and SiO2@NH2 homogeneous particles. Significant performance of Janus in simultaneous phenol and chromium (VI) removal was assigned to phenol degradation via the Advanced Oxidation Process (AOP) on the magnetite face and chromium adsorption on the amine face. This particle was also identified as an alternative for magnetic beads which are used for DNA separation from water and virus and nucleic acid such as Deoxyribonucleic Acid/Ribonucleic Acid (DNA/RNA) isolation and purification from wastewater model. Magnetorheological fluids of magnetic homogeneous and Janus particles were also tested and compared through rheological measurements. An off-state and on-state external magnetic fields were used to study the contribution of anisotropic magnetization to the rheological properties of the magnetic suspension. The synergistic effect of friction force and dipole force in magnetic Janus particles was found more significant in comparison with homogenous particles. We also showed magnetization contribution achieved from magnetic material as a shell or cap does not follow the models presented for conventional types of magnetorheological fluids. We also used amphiphilic and magnetic responsive characteristics of the synthesized Janus particle to generate stimuli-responsive Pickering emulsion. The contribution of the particles’ amphiphilic properties at stabilizing the interface was first tested through an interfacial rheological test. Then, the field-driven response of the Pickering emulsion was tested in bulk magneto-rheological measurements. We showed that Pickering emulsion made of magnetic Janus particles demonstrated gel-like behavior due to a stable magnetic droplet network at the interface. We also found the critical magnetic field density at which droplets coalesce and break down. In summary, a new, simple, and scalable process was used to synthesize magnetic-capped Janus particles. The dual surface functionality of this Janus particle can be used for multi-compounds removal from water. A combination of amphiphilicity, anisotropic characteristics, and field-responsive properties enables the fabricated magnetic Janus particle to a great potential for MR fluid and smart Pickering emulsion.