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Sungho Park

Publications and source records attributed to Sungho Park.

9 recordsLinked to original sources
PubMed2006

Separation of tricomponent protein mixtures with triblock nanorods.

Two-component triblock magnetic nanorods with gold end blocks and nickel interior blocks have been synthesized and used as affinity templates for the simultaneous and efficient separation of a three-component protein mixture. The gold blocks were selectively functionalized with 11-amino-1-undecanethiol, and then glutaraldehyde was used to covalently attach nitrostreptavidin to them. His-tagged proteins bind to the nickel block and biotin-tagged proteins bind to the functionalized gold ends, allowing one to separate a mixture of three proteins with a single material. Each surface-bound protein can be released selectively using imidazole for the His-tagged protein and biotin for the biotinylated protein.

Acetates↗
PubMed2006

Multipole plasmon resonances in gold nanorods.

The optical properties of gold rods electrochemically deposited in anodic aluminum oxide templates have been investigated. Homogeneous suspensions of rods with an average diameter of 85 nm and varying lengths of 96, 186, 321, 465, 495, 578, 641, 735, and 1175 nm were fabricated. The purity and dimensions of these rod nanostructures allowed us to observe higher-order multipole resonances for the first time in a colloidal suspension. The experimental optical spectra agree with discrete dipole approximation calculations that have been modeled from the dimensions of the gold nanorods.

Aluminum Oxide↗
PubMed2005

On-wire lithography.

We report a high-throughput procedure for lithographically processing one-dimensional nanowires. This procedure, termed on-wire lithography, combines advances in template-directed synthesis of nanowires with electrochemical deposition and wet-chemical etching and allows routine fabrication of face-to-face disk arrays and gap structures in the range of five to several hundred nanometers. We studied the transport properties of 13-nanometer gaps with and without nanoscopic amounts of conducting polymers deposited within by dip-pen nanolithography.

Journal Article↗
PubMed2005

Observation of a quadrupole plasmon mode for a colloidal solution of gold nanoprisms.

The synthesis and optical properties of single crystalline gold nanoprisms have been investigated. A three-step mediated seed growth process in an aqueous solution generated gold nanoprisms with a relatively homogeneous size distribution. The purity of these nanostructures has allowed us to observe a weak quadrupole resonance in addition to a strong dipole resonance associated with these novel structures. The experimental optical spectra agree with discrete dipole approximation calculations that have been modeled from the dimensions of gold nanoprisms produced in this synthesis.

Journal Article↗
PubMed2004

Hybrid organic-inorganic, rod-shaped nanoresistors and diodes.

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 the connection with microscopic circuits. In the three-component systems, the metal blocks provide an additional design flexibility, allowing one to prepare Schottky junctions.

Journal Article↗
PubMed2004

Self-assembly of mesoscopic metal-polymer amphiphiles.

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 facilitates their assembly by optimizing the correct collisional orientation upon dissolution of the template. Tubular structures with tailorable diameters can be assembled in a predictable manner on the basis of an estimate of the hybrid rod packing parameters.

Journal Article↗
PubMed2003

Electrochemical infrared characterization of CO comains on ruthenium-decorated platinum nanoparticles.

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 nanoparticles and the gold substrates. The observed promotion in CO electrooxidation by the existence of a Ru island on Pt nanoparticles, of interest to fuel-cell catalysis, showed a strong relationship with Ru surface concentrations, consistent with previous studies on single crystal or polycrystalline bimetallic surfaces. Two distinctive CO infrared bands, one for the Pt-CO and one for Ru-CO domain were found after the dipole coupling of CO within the two CO domains was minimized. Interestingly, those two CO bands showed independent electrooxidation behavior with electrode potential changes. Also, it is shown that the electrooxidation of CO on large Ru islands is less facile than on small Ru islands. In addition, the activity of commercial Pt/Ru alloy nanoparticles to CO stripping was tested and IRAS spectra were reported as a comparison to our Ru-decorated Pt nanoparticles.

Journal Article↗
PubMed2002

Transition metal-coated nanoparticle films: vibrational characterization with surface-enhanced Raman scattering.

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 the form of the SER spectra for chemisorbed carbon monoxide and ethylene. The potential of the present strategy for synthesizing relatively monodispersed "core-shell" nanoparticles using a myriad of coating materials, also displaying SERS activity, is pointed out.

Journal Article↗