Publications by authors named "Baeck Choi"

Here we report a simple and scalable soft-lithography-based templating technology for fabricating Au-covered oxide (titania and zirconia) gratings by using DVDs as a structural template. The resulting plasmonic gratings simultaneously exhibit very high surface plasmon resonance (SPR) sensitivity (up to ∼940 nm per refractive index unit, nm per RIU) and figure of merit (FOM, up to 62.5).

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Here we report a simple and scalable colloidal lithography technology for fabricating periodic arrays of gold nanodonuts for sensitive surface plasmon resonance (SPR) analysis. This new bottom-up approach leverages a unique polymer wetting layer between a self-assembled, non-close-packed monolayer silica colloidal crystal and a silicon substrate to template ordered gold nanodonuts with tunable geometries over wafer-sized areas. The processes involved in this templating nanofabrication approach, including spin coating, oxygen plasma etching, and metal sputtering, are all compatible with standard microfabrication technologies.

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Article Synopsis
  • A new shape-memory polymer (SMP) has been created by combining techniques from photonic crystals and SMP technologies.
  • This innovative SMP allows for shape recovery at room temperature, which is a significant improvement over traditional methods.
  • It can instantly revert to its original shape when exposed to different organic vapors, making it versatile for various applications.
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Here we report a scalable colloidal templating approach for fabricating periodic arrays of metallic and silicon nanorings with complex nanostructures. Non-close-packed monolayer silica colloidal crystal prepared by a simple spin-coating technology is first used as template for making periodic arrays of mushroom-like composite nanostructures consisting of silica spherical caps and polymer stems. Subsequent metal sputtering and reactive ion etching lead to the formation of ordered asymmetric nickel nanorings which can be further utilized as etching masks for patterning periodic arrays of symmetric silicon nanorings.

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Here, we report a scalable bottom-up approach for fabricating periodic arrays of metal nanorings and nanocrescents. Wafer-scale monolayer silica colloidal crystals with an unusual non-close-packed structure prepared by a simple and rapid spin-coating technology are used as both etching and shadowing masks to create nanoring-shaped trenches in between templated polymer posts and sacrificial nanoholes. Directional deposition of metals in the trenches followed by liftoff of the polymer posts and the sacrificial nanoholes results in forming ordered metal nanorings.

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Electrocatalysts for hydrogen oxidation reactions (HORs) are the key to renewable-energy technologies including fuel cells, hydrogen pumps, and water splitting. Despite the significant technological interest and tremendous efforts that have been made, development of hydrogen electrode catalysts with high activity at low cost remains a great challenge. Here, we report the preparation, characterization, and electrochemical properties of a hybrid material composed of Pd nanocrystals grown on spontaneously oxidized WC as a high-performance catalyst for the HOR.

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