Young Rae Hong

Photochemical deposition of Co and Ni based oxygen evolution catalysts on hematite nanorods cathodically shifted the onset potential of photocurrent near to the flat band potential of hematite. A 9.5 fold enhancement in the photocurrent density at 0.86 V vs. RHE compared to the parent hematite photoanode was observed with the Ni–Bi/Fe2O3 photoanode.

Novel low band gap copolymers based on dithienosilole and thienopyrroledione units were synthesized. Copolymer P1 with branched side chains on the TPD units demonstrated a PCE of 4.4% with a high Voc of 0.89 V for OPV applications while OTFT devices fabricated from a copolymer containing linear side chains (P2) performed better in OTFT device configurations.

Applying sufficiently strong shear to thin films of a sphere-forming polystyrene–polyisoprene diblock copolymer is shown to induce an order-order transition to cylinders. The transformation is not continuous or epitaxial, as the intercylinder spacing is ca. 10% greater than the spacing between close-packed lines of spheres. The transition is facilitated when the block copolymer has a composition which places it close to the “zero-field” (no shear) sphere/cylinder phase boundary; the… Show more

Applying sufficiently strong shear to thin films of a sphere-forming polystyrene–polyisoprene diblock copolymer is shown to induce an order-order transition to cylinders. The transformation is not continuous or epitaxial, as the intercylinder spacing is ca. 10% greater than the spacing between close-packed lines of spheres. The transition is facilitated when the block copolymer has a composition which places it close to the “zero-field” (no shear) sphere/cylinder phase boundary; the shear-induced transformation is more difficult and less effective for a polymer further from this boundary. Applying a modest shear stress to a polymer close to the boundary distorts the hexagonal lattice formed by the spheres without forming cylinders; the mechanical anisotropy produced by this distortion is sufficient to permit a film containing only a single layer of spherical domains to align in shear. Show less

A silicon (Si) nanowire grid ultraviolet (UV) transmission polarizer has been fabricated, and its performance was measured over the visible to deep UV range. A cylinder-forming polystyrene-b-poly(hexylmethacrylate) diblock copolymer was coated onto an amorphous Si layer supported on a fused silica substrate, then shear aligned and employed as a mask for reactive-ion etching, resulting in a Si grid of 33 nm period and multi-centimeter-squared area. Due to the high plasma frequency and UV… Show more

A silicon (Si) nanowire grid ultraviolet (UV) transmission polarizer has been fabricated, and its performance was measured over the visible to deep UV range. A cylinder-forming polystyrene-b-poly(hexylmethacrylate) diblock copolymer was coated onto an amorphous Si layer supported on a fused silica substrate, then shear aligned and employed as a mask for reactive-ion etching, resulting in a Si grid of 33 nm period and multi-centimeter-squared area. Due to the high plasma frequency and UV reflectance of the deposited Si, this nanowire grid was able to polarize light down into the deep UV, including 193 nm.

Show less

Hexagonal arrays of nanoscale holes or metal dots (25 nm in diameter and 39 nm in period), with orientational order extending over the entire square-centimeter array area, were fabricated on unpatterned silicon wafer substrates using a shear-aligned sphere-forming diblock copolymer template. Since two or more layers of spherical nanodomains are required to achieve alignment in the block copolymer film, but pattern transfer requires a single layer, a multistep etching process was developed… Show more

Hexagonal arrays of nanoscale holes or metal dots (25 nm in diameter and 39 nm in period), with orientational order extending over the entire square-centimeter array area, were fabricated on unpatterned silicon wafer substrates using a shear-aligned sphere-forming diblock copolymer template. Since two or more layers of spherical nanodomains are required to achieve alignment in the block copolymer film, but pattern transfer requires a single layer, a multistep etching process was developed, whereby the top layer of a shear-aligned bilayer was evenly removed, leaving the ordered bottom layer as the fabrication template for hole and dot arrays free from grain boundaries.
Show less

Here we report the first measurement of homogeneous electron transfer between oxidized and reduced metal tris(bipyridine) core dendrimers by NMR line-broadening; the results indicated that, as the generation of the dendrimer increased, the rate of self-exchange decreased.

Heterogeneous electron-transfer rates in metal tris(bipyridine) core dendrimers were measured using Osteryoung square-wave voltammetry. Rates decreased with generation, and this decrease could be correlated with the molecular weight increase. These results indicate that the coordination number around the redox center did not play any special role in sterically encapsulating the redox center.