Young Ki Hong

CHARACTERISTICS OF ELECTRICALLY CONDUCTING POLYMER-COATED TEXTILES

Intrinsically conducting polymer (ICP)/textile composites were prepared by coating polypyrrole (PPy) or poly (3,4-ethylenedioxythiopene) (PEDOT) on the fabrics through chemical and electrochemical oxidation of pyrrole or EDOT. We investigated the effects of the preparation conditions on the properties of the resulting composite such as ICP content, electrical conductivity, surface morphology, and electromagnetic interference shielding effectiveness (EMI SE). The specific volume resistivity of the composite was as low as 0.3 Ω-cm, giving rise to about 36 dB of EMI SE over the wide range of frequency up to 1.5 GHz. We also prepared the elastic textile composites, exhibiting a monotonic increase of the electrical resistance with the elongation up to 50%. We, therefore, propose the elastic textile composite can be used as a strain sensor for large deformation.

Light-emitting color barcode nanowires using polymers: nanoscale optical characteristics.

We report on the light-emitting color barcode nanowires (LECB-NWs), which were fabricated by alternating the electrochemical polymerization of light-emitting polymers with various luminescence colors and efficiencies. The nanoscale photoluminescence characteristics of LECB-NWs were investigated using a laser confocal microscope with a high spatial resolution. The alternating light emissions of the LECB-NWs showed orange-yellow, red, and green colors due to the serial combination of poly(3-butylthiophene), poly(3-methylthiophene), and poly(3,4-ethylenedioxythiophene), respectively, with distinct luminescence intensities. The optical detection sensitivity and stability of LECB-NWs have been enhanced through a nanoscale Cu metal coating onto the NWs, based on surface plasmon resonance coupling and protection against oxidation. The flexibility of the LECB-NWs has been investigated through the folding and unfolding of the NWs by an applied nanotip impetus. The flexible LECB-NWs can be used as highly sensitive optical identification nanosystems for nanoscale or microscale products with complex physical shapes.

Fabrication and magnetic characteristics of hybrid double walled nanotube of ferromagnetic nickel encapsulated conducting polypyrrole

This letter is a report on hybrid double walled nanotubes (HDWNTs) of crystalline ferromagnetic nickel (Ni) nanotubes encapsulated conducting polypyrrole (PPy) nanotubes through a sequentially electrochemical synthetic method. Ferromagnetic Ni nanotubes were fabricated by an electrochemical deposition method outside the wall of the conducting PPy nanotubes. The formation and structure of HDWNTs of conducting PPy nanotubes and ferromagnetic Ni nanotubes were confirmed by transmission electron microscopy, high-resolution transmission electron microscopy, and elementary analysis. From the angular dependences of the magnetic hysteresis curves of the HDWNTs, the authors observed that the Ni nanotubes of the HDWNT systems had an anisotropic ferromagnetic nature with the maximum of coercivity and remanent-saturation magnetization when applying a magnetic field along the parallel direction of the tubes.

Environmental Staility of EMI Shielding PET Fabric/Polypyrrole Composite

PET fabric/polypyrrole composites with high electrical conductivity were prepared by polymerization of polypyrrole on a PET fabric through both chemical and electrochemical oxidation of pyrrole monomer. We investigated environmental stability of the composite and measured activation energy using the Arrhenius Equation.

DNA detection using a light-emitting polymer single nanowire

Functionalization of light-emitting poly(3-methylthiophene) (P3MT) nanowires (NWs) with probe-DNA (p-DNA) and their label-free recognition of target-DNA (t-DNA) were correlated quantitatively with both the photoluminescence (PL) color and intensity of P3MT NWs.

Effects of electron-beam irradiation on conducting polypyrrole nanowires

Conducting polypyrrole (PPy) nanowires (NWs) were irradiated by a relatively high energy (300 keV–2 MeV) electron-beam (e-beam) generated from a linear electron accelerator in an atmospheric environment. From the current-voltage characteristics of pristine and 2 MeV e-beam irradiated PPy NWs, we observed a dramatic variation in resistance from 8.0×102 to 1.45×108 Ω, that is, we observed a transition from conducting states to nonconducting states through the e-beam irradiation. To discern conformational changes and the doping states of PPy NWs through the e-beam irradiation, we measured Raman and ultraviolet-visible absorption spectra for the PPy NWs. As the energy of the e-beam irradiation increased, we observed that the PPy NWs were changed from doping states to dedoping states with conformational modification including the variation in π-conjugation length.

The Influence of Psychologic Factors on Diskography in Patients With Chronic Axial Low Back Pain

OBJECTIVE To determine whether a patients presenting psychometric scores affect the findings of a pressure and injection speed-controlled manometric lumbar diskography in patients with chronic low back pain (CLBP). DESIGN A prospective, correlation-based, investigative study. SETTING Free-standing ambulatory spine surgery center. PARTICIPANTS Two hundred sixty-three disks from 81 patients (54 men, 27 women). INTERVENTION Diskography was performed using pressure and injection speed-controlled techniques. The patients were divided into psychometric subgroups (normal, at risk, abnormal) according to the Distress and Risk Assessment Method (DRAM). MAIN OUTCOME MEASURES The diskography findings on each psychometric DRAM subgroup were evaluated. RESULTS Across the individual psychometric categories, the positive rates of diskography in the normal, at-risk, and abnormal subgroups were 75.0% (9/12), 59.5% (25/42), and 70.4% (19/27), respectively (P>.05). The mean numeric rating scores of pain at 15 and 50 psi above the opening pressure were similar in the 3 psychometric subgroups. There was no correlation between the diskography results and the psychometric subgroupings. CONCLUSIONS In patients with CLBP, there is no correlation between the presenting psychometric DRAM score and the findings from pressure and injection speed-controlled manometric lumbar diskography.

Characteristics of vapor coverage formation on an RF-driven metal electrode to discharge a plasma in saline solution

The generation condition of sub-mm sized non-thermal plasmas (named aqua-plasmas) inside electrically conductive liquids (saline) is investigated with various electrical conductivities of the electrolyte. The breakdown condition of an RF-driven (380 kHz and less than 50 W) aqua-plasma discharge on a metal electrode is investigated using both experimental and numerical simulation methods. Since breakdown occurs in the vapor covering the powered electrode surface, the boiling process and the influence of fluidic dynamics on the vapor coverage oscillation are considered in detail. The vapor coverage is formed on the metal electrode surface via three phases: individual bubble generation, merging of bubbles and maintaining the bubbles during the aqua-plasma discharge inside the full vapor coverage. The surface temperature is evaluated from a numerical simulation based on the proposed one-dimensional aqua-plasma equivalent circuit electro-fluid power balance, and the bubble coverage can be sustained due to boiling of the film on the heated electrode by a current flow of electrolyte ions, especially Na+ in this case. The periodic discharge of the aqua-plasma inside the shrunken vapor coverage is investigated by a model that considers the electrolyte viscosity and surface charge model. The vapor coverage periodically shrinks under the heat balance between the gain, mainly plasma heating and heat flux from the heated tip, and the loss to the saline, so it is a feature that the aqua-plasma is discharged during the period of shrinkage. Moreover, the tip, heated up to meet the temperature condition of film boiling ~300 °C, reduces the breakdown field due to the reduced work function of the electrode material.

High-yield and environment-minded fabrication of nanoporous anodic aluminum oxide templates

Nanoporous anodic aluminum oxide (AAO) templates, fabricated via anodization, have been widely studied in fundamental science and industry, for use as functional nanostructures in opto-electronics, membrane filters, energy storage devices, bio-applications, magnetic memory, etc. However, conventional AAO fabricating techniques have several disadvantages, such as the relatively long time required, inefficient usage of resources, and their toxicities, which restrict their practical application. This paper reports on a high-yield and environment-minded fabrication method for nanoporous AAO templates, accomplished through simultaneous multi-surface anodization and direct detaching of AAOs from an aluminum (Al) substrate by applying stair-like reverse biases in one electrolyte. These procedures can be repeated for mass production (i.e., high yield) using the same Al substrate. The nanoporous AAO templates fabricated here were used to synthesize gold (Au) nanowires (NW) with a diameter of ∼25 nm. This development, together with the modulation of physical properties of Au NWs, can enrich the potential of future nanotechnology based on nanoporous templates, and can also contribute to green technology owing to its minimized toxicity as well as its efficient use of resources.

Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting Polymer Nanostructures

Light-emitting π-conjugated polymers and their nanostructures have been intensively studied from the viewpoints of both fundamental research and optoelectronic applications. The characteristics of light-emitting polymer nanostructures, such as light absorption and emission efficiencies, can be tuned through chemical processing and by varying their physical dimensions. In this review article, recent progress in the synthesis, characterization, modification, and applications of light-emitting polymer-based nanostructures is presented. Various synthetic methods for light-emitting polymer nanostructures are introduced, and their intrinsic optical properties at a nanoscale level are summarized. Post-synthetic treatments for modification of the characteristics related to the morphologies and doping states are discussed. Finally, potential applications of these nanostructures to barcode/quasi-superlattice nanowires, biosensors, and nano-optoelectronics are presented.