(474e) Monolayer Assembly of Monodisperse Nanoparticles for Magnetic and Catalytic Applications

With unique properties different from their bulk materials, nanoparticles (NPs) with controlled size, shape and composition have been extensively studied not only for scientific interests but also for technological developments. Organic solution-phase synthesis has been demonstrated to be a versatile and robust method for synthesizing these NPs. Over the years, assembling these well-defined NPs into functional devices through "bottom-up" approach has being actively pursued. In this talk, I will give two examples of synthesis and assembly of monodisperse NPs for magnetic and catalytic studies.

Specifically, I will discuss the controlled synthesis of monodisperse cobalt ferrite NPs with tunable magnetic properties and the large-area monolayer assembly of these magnetic NPs through the water-air interfacial self-assembly approach.¹ The monolayer arrays can be used as magnetic recording media, demonstrating great potentials in magnetic data storage application. This self-assembly approach can be extended to uniform cobalt NPs, which are of great interests for catalyzing OER in water splitting.²In this case, highly stable cobalt NPs are demonstrated to be more active and stable than the state-of-the-art iridium catalyst. More importantly, the well-defined monolayer catalyst of the cobalt NPs enables more detailed study of the intrinsic OER activity of cobalt NPs, showing 15 times higher turnover frequency and mass activity than the NPs deposited on conventional carbon black. These two examples demonstrate the importance of assembling well-defined NPs into ordered monolayer arrays for important technological applications and fundamental studies.

References

1. Wu, L.; Jubert, P. O.; Berman, D.; Imaino, W.; Nelson, A.; Zhu, H.; Zhang, S.; Sun, S., Monolayer Assembly of Ferrimagnetic Co_xFe_3-xO₄ Nanocubes for Magnetic Recording. Nano Lett. 2014, 14, 3395-3399.

2. Wu, L.; Li, Q.; Wu, C. H.; Zhu, H.; Mendoza-Garcia, A.; Shen, B.; Guo, J.; Sun, S., Stable Cobalt Nanoparticles and Their Monolayer Array as an Efficient Electrocatalyst for Oxygen Evolution Reaction. J. Am. Chem. Soc. 2015, 137, 7071-7074.