Sung Ho Park

The assembly properties of two- and three-component rod-like building blocks consisting of gold and polymer block domains have been investigated. These structures behave like mesoscopic amphiphiles and form a series of single-layer superstructures consisting of bundles, tubes, and sheets depending upon the compositional periodicity. Unlike molecular systems, the template used to initially synthesize them plays a critical role in the assembly process by prealigning them in a manner that facilitat

The voltammetric electrooxidation rates of formic acid, formaldehyde, and methanol in acidic electrolyte on carbon-supported platinum nanoparticle films with varying particle diameters ( d ) in the range of ca. 2−9 nm are examined with the objective of comparing the nanoparticle size sensitivity for these related yet distinct electrocatalytic processes. The reaction rates on the larger nanoparticles ( d > 4 nm) are similar to those observed on polycrystalline Pt when normalized to the same micro

High-performance, flexible all graphene-based thin film transistor (TFT) was fabricated on plastic substrates using a graphene active layer, graphene oxide (GO) dielectrics, and graphene electrodes. The GO dielectrics exhibit a dielectric constant (3.1 at 77 K), low leakage current (17 mA/cm(2)), breakdown bias (1.5 × 10(6) V/cm), and good mechanical flexibility. Graphene-based TFTs showed a hole and electron mobility of 300 and 250 cm(2)/(V·s), respectively, at a drain bias of -0.1 V. Moreover,

The utilization of surface-attached gold nanoparticles as templates for generating Pt-group particles displaying near-optimal surface-enhanced Raman scattering (SERS) characteristics is described. Essentially epitaxial transition metal coatings down to the monolayer level can be prepared, most readily by the spontaneous replacement of an electrochemically deposited copper layer by the desired Pt-group metal. The and essentially pinhole-free nature of the coated nanoparticles is demonstrated from

Monte Carlo simulations of hydration water on the mica (001) surface under ambient conditions revealed water molecules bound closely to the ditrigonal cavities in the surface, with a lateral distribution of approximately one per cavity, and water molecules (interposed between K+ counter ions) in a layer situated about 2.5 A from a surface O along a direction normal to the (001) plane. The calculated water O density profile was in quantitative agreement with recent x-ray reflectivity measurements

This paper reports a methodology for preparing ordering hydrophilic metal nanoparticles into close-packed 2-dimensional arrays at a hexane-water interface with alkanethiol in the hexane layer. The destabilization of metal nanoparticles by the addition of alcohol caused the nanoparticles to adsorb to an interface where the surface of entrapped Au nanoparticle was in situ coated with the long-chain alkanethiols present in a hexane layer. The adsorption of alkanethiol to the nanoparticle surface ca

We present a simple synthetic method for hexagonal Au nanoplates. Selective etching of specific facets of triangular nanoplates has led to the shape transformation. Also, the high quality of hexagonal Au nanoplates allows one to identify the higher-order plasmon resonance bands in addition to the dipole mode.

The electrical properties of template-synthesized three- and four-component rodlike nanostructures consisting of metal and conducting polymer domains have been studied. These structures behave like nanometer-scale resistors and diodes, depending upon their compositions and spatial distribution of the different compositional blocks. In the two-component systems, the conducting polymer block dictates the electrical properties of the nanostructure, and the metal blocks act as leads to facilitate th

Electrode potential-dependent infrared spectra for carbon monoxide dosed onto carbon-supported platinum nanoparticle films, significant as commercial fuel-cell catalysts as well as of fundamental importance, are reported with the aim of elucidating their structure as a function of particle size. The need to acquire absolute unipolar, rather than bipolar, spectra by means of potential-difference infrared tactics for such nanoparticle films is demonstrated, given the broad asymmetric C−O stretchin

This paper reports a method for assembling midnanosized Au nanoparticles (25 < d < 100 nm) into close-packed 2D arrays with a high degree of local order. An in situ coating of Au nanoparticles with an alkanethiol surfactant can induce close-packed particle arrays when the nanoparticles are trapped at the interface. The film morphology was determined to be either monoparticulate or multiparticulate depending on the 1-dodecanethiol concentration. This paper reports on the optimum conditions for th

Surface plasmonics of nanomaterials has been one of the main research themes in nanoscience. Spherical and elongated nanoparticles show their corresponding unique optical features mainly depending on the physical dimensions. Here we successfully synthesized Au nanorings having Pt framework (Pt@Au nanorings) with high uniformity through wet-chemistry. The synthetic strategy consisted of serial reactions involving site-selective growth of Pt on the rim of Au nanoplates, subsequent etching of Au na

We report a methodology for synthesis of palladium (Pd) nanospring structures using an anodic aluminum oxide (AAO) membrane template and facile electrochemical deposition. The hydroxyl-terminated surfaces of alumina nanochannels and localized hydrogen evolution contribute to the growth of Pd atoms at peripheral positions of the alumina nanochannels in the presence of an effectual electric potential and a plating solution consisting of PdCl(2), CuCl(2), and HCl. Structural characterization includ

This paper describes a new strategy for synthesizing hollow nanotubes (pore d > 100 nm) with nanoporous walls (pore d < 10 nm) as well as how the nanoporous hollow nanotubes exhibit better intrinsic electrocatalytic activity toward methanol oxidation compared with an analogous nanotube system with smooth walls. Compared with vertical arrays of a nanorod system, the nanotube system is better in terms of increasing the effective surface area because the inner and outer surfaces are both in contact

Two-dimensional ordered arrays of honeycomb morphology of platinum are fabricated by using anodized aluminum oxide template and metal sputtering methods. The resulting metal films are highly conductible (71 Ω/sq), stretchable (16.8%), and transparent (75.2% at 550 nm). The presented synthetic strategy is scalable to large area without noticeable defects by incorporating the deposition of a thin layer of silver. In addition, both the pore size and wall thickness of platinum nanomesh films are str

Spectra obtained by electrochemical infrared reflection absorption spectroscopy (EC-IRAS) for carbon monoxide (CO) adlayers formed by partial CO dosing on various ruthenium-decorated platinum nanoparticle films are reported. The need to achieve a well distributed rather than aggregated metal nanoparticle array is demonstrated, given that such nanoparticle aggregates induce complex dielectric behavior. The strategy here is to use an "organic glue matrix" (short chain SAMs) between the nanoparticl