Postdoc – Designed Polymers for Water Purification and Clean Energy Generation

Reversible Capture and Release of Hg(II) from Water Using Conducting Polymers

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Heavy metal ions, especially mercury (Hg) in water, are highly toxic, so become a threat to public health and environment.  In this work, I demonstrated how the redox active polyaniline reversibly captured and released Hg(II) in water. Polyaniline naturally adsorbs Hg(II), and subsequent dose of oxidation potential induces the release.  Nanofiber geometry of polyaniline offered faster adsorption kinetics, and additional sulfur chelating groups enhanced uptake capacity. 

Kim, Y. et al. J. Am. Chem. Soc. 2018, ASAP (doi)

Current work targets different toxic ions with higher capacity and faster response.

Kim, Y. et al.  (In preparation)

Extremely Stable and Highly Conducting Anion Exchange Membranes for Fuel Cells

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Anion exchange membrane fuel cells are a clean and efficient promising future energy source. However, the development of stable high-performance membranes remains a major challenge. Herein I demonstrated how the effective phase separation improved both chemical and mechanical properties of the membranes.

Kim, Y. et al.  ACS Appl. Mater. Interfaces 2017, 9, 42409.  (doi)

Current work focuses on design and synthesis of new cations and new polymers to overcome the above mentioned challenges.

Kim, Y. et al.  (In preparation)


Ph.D. – Science and Engineering on Nanocomposites

Stretchable Nanoparticle Conductors

 (from left to right) Photograph of a free-standing Au NP composite. Calculated conductivity dependence on strain for composites described by percolation theory. TEM images of NP layers under strain of 0%, 30%, and 50%.

(from left to right) Photograph of a free-standing Au NP composite. Calculated conductivity dependence on strain for composites described by percolation theory. TEM images of NP layers under strain of 0%, 30%, and 50%.

I demonstrated an example of excellent stretchable conductors from self-organization of nanoparticles (NPs).   Free-standing stretchable conductors were prepared by layer-by-layer (LBL) assembly.   High conductivity and stretchability originated from dynamic self-organization of NPs.   Modified percolation theory to incorporate the self-organization supports the experimental observation.

Kim, Y. et al. Nature 2013, 500, 59.  (doi)

Reconfigurable Chiroptical Nanocomposites

 (from left to right) Chiroptical nanocomposites from gold NPs. Circular dichroism (CD) spectra of the composites under strains of 0, 10, 25 and 50%. Stimulated emission depletion microscopy images of chiroptically assembled NPs in mirror symmetry.

(from left to right) Chiroptical nanocomposites from gold NPs. Circular dichroism (CD) spectra of the composites under strains of 0, 10, 25 and 50%. Stimulated emission depletion microscopy images of chiroptically assembled NPs in mirror symmetry.

Here, I demonstrated the chiroptical nanocomposites for the applications of metamaterials devices and optoelectronics.  Nanocomposites were LBL assembled from NPs and single-walled carbon nanotubes.   Chiroptical activities were reversibly tunable by macroscale stresses.  S-like non-planar nano-assemblies are responsible for the optical activities and this was confirmed by computational simulations.

Kim, Y. et al. Nature Materials 2016, 15, 461.  (doi)


B.S. – Cross-linked Porous Networks

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Porous materials are widely used for chemical separations, sensing, and storage. I synthesized highly porous (surface areas up to 1,200 m g-1) and robust materials using octaphenylsilsesquioxanes. Copper-mediated in-situ homocoupling effectively constructed the networks.

Kim, Y. et al. Macromolecules 2010, 43, 6995.  (doi)