With unique properties different from their bulk materials, magnetic nanoparticles (NPs) have been extensively studied not only for scientific interests but also for technological developments. Organic solution-phase synthesis provides a versatile and robust method for synthesizing monodisperse NPs with controlled size, shape and composition. Those monodisperse NPs can be self-assembled into functional devices through the “bottom-up” approach. This thesis focuses on the synthesis and self-assembly of several magnetic NPs, as well as their applications in magnetic recording and catalysis. Synthesis and self-assembly of monodisperse magnetic NPs are very important for magnetic recording. In this thesis, I will discuss the controlled synthesis of cobalt ferrite NPs with tunable size and magnetic properties. Large-area monolayer arrays of those ferrimagnetic NPs were fabricated through the water-air interfacial self-assembly. The monolayer arrays were studied as the magnetic recording media, demonstrating their great potentials in data storage application. This solution-phase synthesis and self-assembly approach were extended to ferromagnetic barium ferrite NPs, which can be potentially used for magnetic recording and permanent magnets. The investigations of magnetic NPs for catalytic applications will also be discussed. Specifically, I will discuss the efficient catalytic activity of cobalt (Co) NPs for oxygen evolution reaction (OER) in water splitting. Highly stable Co NPs were synthesized through thermal decomposition of Co2(CO)8 followed by a post reductive annealing treatment. The developed NPs are more active and stable than state-of-the-art iridium catalyst. Moreover, well-defined monolayer catalyst of the Co NPs was developed to evaluate their intrinsic OER activity, showing 15 times higher turnover frequency and mass activity than the NPs deposited on conventional carbon support. Strong ferromagnetic face-centered tetragonal (fct) FePt NPs are a superior catalyst towards oxygen reduction reaction (ORR). However, it is very challenging to make fully order intermetallic fct-FePt NPs. In the thesis, I will discuss a new approach to fully ordered fct-FePt NPs through dumbbell-like FePt-Fe3O4 NPs. The fct-FePt NPs exhibit the highest catalytic activity and durability for ORR among all intermetallic Pt-based catalysts.
Wu, Liheng,
"Synthesis and Self-assembly of Monodisperse Nanoparticles for Magnetic and Catalytic Applications"
(2016).
Chemistry Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0S75DRB
