Kook Hyun Yu

Highly Flexible and Planar Supercapacitors Using Graphite Flakes/Polypyrrole in Polymer Lapping Film.

Flexible supercapacitor electrodes have been fabricated by simple fabrication technique using graphite nanoflakes on polymer lapping films as flexible substrate. An additional thin layer of conducting polymer polypyrrole over the electrode improved the surface conductivity and exhibited excellent electrochemical performances. Such capacitor films showed better energy density and power density with a maximum capacitance value of 37 mF cm(-2) in a half cell configuration using 1 M H2SO4 electrolyte, 23 mF cm(-2) in full cell, and 6 mF cm(-2) as planar cell configuration using poly(vinyl alcohol) (PVA)/phosphoric acid (H3PO4) solid state electrolyte. Moreover, the graphite nanoflakes/polypyrrole over polymer lapping film demonstrated good flexibility and cyclic stability.

Enhanced supercapacitive performances of functionalized activated carbon in novel gel polymer electrolytes with ionic liquid redox-mediated poly(vinyl alcohol)/phosphoric acid

Supercapacitors with solid/gel polymer electrolytes have attracted much attention due to their high reliability, flexibility, facile designing, being separator-free and free from electrolyte leakage and volatilization such that they can meet the increasing demands of practical applications. The present work reports on a functionalized activated carbon (AC) supercapacitor based on novel redox-mediated gel polymer electrolyte, PVA/H3PO4/ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, [EMIM]BF4). The electrochemical properties of this supercapacitor were studied using cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy techniques with various concentrations of [EMIM]BF4 in PVA/H3PO4 gel polymer electrolyte. The incorporation of [EMIM]BF4 in PVA/H3PO4 electrolyte effectively increased the specific capacitance value due to the improved ionic conductivity and additional pseudo-reaction occurring in the electrode/electrolyte interfaces. The specific capacitance of the supercapacitor using PVA/H3PO4/[EMIM]BF4 (50%) electrolyte showed a maximum value of 271 F g−1 at 0.5 A g−1 discharge current, which is much higher than the bare PVA/H3PO4 (103 F g−1) based supercapacitor. The supercapacitor with PVA/H3PO4/[EMIM]BF4 (50%) electrolyte showed enhanced energy and power density of 54.3 W h kg−1 and 23.88 kW kg−1 respectively. Moreover the device showed comparable specific capacitance retention after 3000 cycles of charge/discharge.

Effective immobilization of glucose oxidase on chitosan submicron particles from gladius of Todarodes pacificus for glucose sensing

An effective enzymatic glucose biosensor was developed by immobilizing glucose oxidase on chitosan submicron particles synthesized from the gladius of Todarodes pacificus (GCSP). The chemically synthesized chitosan from gladius was pulverized to submicron particles by ball milling technique, which was further characterized and compared with the standard chitosan (SCS). The degree of deacetylation of GCSP was determined using FTIR spectroscopy which was comparable to the value of standard chitosan. The glucose oxidase (GOx) was immobilized over GCSP on porous zinc oxide/platinum nanoparticle (ZnO/Pt) based electrode. The morphological and structural properties of the electrodes were analyzed using scanning electron microscopy and X-ray diffraction analysis. The glucose sensing behavior of electrode was estimated using electrochemical analysis and showed an excellent analytical performance. The electrode ZnO/Pt/GCSP conjugated with GOx displayed high sensitivity (88.76 μA mM(-1) cm(-2)) with low detection limit in short response time. In addition, the very low value of Michaelis-Menten constant for GCSP based electrode contributes a better affinity of the electrode surface towards glucose oxidase.

Electrochemical supercapacitor behaviour of functionalized candle flame carbon soot

The electrochemical supercapacitor behaviour of bare, washed and nitric acid functionalized candle flame carbon soots were reported. Crystallinity and the morphology of the candle soots were recorded using X-ray diffraction analysis, scanning and transmission electron microscopy, respectively. The nitric acid functionalized candle soot showed an improved Brunauer–Emmett–Teller surface area of 137.93 from 87.495 m2 g−1 of washed candle soot. The presence of various functional groups in candle soots and the development of oxygen functionalities in the functionalized candle soot were examined through Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis. Raman spectra showed the characteristic peaks corresponding to the D (diamond) and G (graphite) phase of carbon present in the candle soots. The electrochemical characterization was performed by cyclic voltammetry, galvanostatic charge/discharge test and impedance spectroscopy in 1 M H2SO4 electrolyte. The functionalized candle soot electrode showed an enhanced specific capacitance value of 187 F g−1 at 0.15 A g−1 discharge current density, which is much higher than that of bare and washed candle soot electrodes.

In vivo targeting of ERG potassium channels in mice and dogs by a positron-emitting analogue of fluoroclofilium

The antiarrhythmic clofilium is an efficient blocker of hERG1 potassium channels that are strongly expressed in the heart. Therefore, derivatives of clofilium that emit positrons might be useful tools for monitoring hERG1 channels in vivo. Fluoroclofilium (F-clofilium) was synthesized and its channel-blocking properties were determined for hERG1 and hEAG1 channels expressed in HEK 293 cells and in Xenopus oocytes. When applied extracellularly in the whole-cell patch-clamp configuration, F-cloflium exhibited a slower onset of block when compared with clofilium, presumably owing to its lower membrane permeability. When applied in the inside-out configuration at the intracellular membrane side, it blocked hEAG1 channels almost as efficiently as clofilium (IC50 1.37 nM and 0.83 nM, respectively). Similar results were obtained for hERG1, showing Fclofilium is a potent hERG1 and hEAG1 channel blocker once it has reached the intracellularly accessible target site at the channel. Using the 18F-labeled analog we studied the in vivo binding and distribution of F-clofilium in mice and a dog. Greatest activity was found in kidneys and bones. A small but significant enrichment of activity in the dog myocardium known for its expression of cERG1 channels allowed to depict the myocardium of a living dog by PET. Thus, F-clofilium is a useful tool for imaging hERG channels in living organisms.

Expeditious and eco-friendly hydrothermal polymerization of PEDOT nanoparticles for binder-free high performance supercapacitor electrodes

Poly(3,4-ethylenedioxythiophene) (PEDOT) is a promising conjugated polymer that has attracted attention because of its outstanding electronic properties, useful for a wide range of applications in energy storage devices. However, synthesis of high-quality PEDOT occurs via vapour phase polymerization and chemical vapour deposition techniques using extrinsic hard templates or complicated experimental setups. This study introduces a simple hydrothermal polymerization technique using ferric chloride (FeCl3) as an oxidizing agent to overcome the above drawback, which results in good conductive, crystalline PEDOT nanodendrites and nanospheres. The effects of varying the molar ratio of FeCl3 oxidant were investigated in terms of the structural, morphological and electrochemical properties of PEDOT. The supercapacitive performance of the as-polymerized PEDOT nanostructures was determined by fabricating an electrode without the aid of organic binders or conductive additives. PEDOT nanodendrites polymerized using 2.5 molar ratio of FeCl3 demonstrated enhanced electrochemical performance with a maximum specific capacitance of 284 F g−1 with high energy density of 39.44 W h kg−1 at 1 A g−1 current density in 1 M H2SO4 electrolyte. Moreover, the sample possessed higher conductivity, better specific surface area, improved electrochemical properties, comparable crystallinity, and excellent cycling stability after 5000 charge/discharge cycles than the other PEDOT nanostructures. Importantly, the results establish that these materials afford good redox behaviors with better conductivity suitable for the development of an organic electrode-based supercapacitor with high specific charge capacity and stability.

Surface treatments of silver rods with enhanced iodide adsorption for I-125 brachytherapy seeds

This study described an effective method to load (125)I on silver rods for the preparation of a brachytherapy source. We tested various ligands on the silver rod surface to screen the one with the highest adsorption and specific radioactivity. In addition, we investigated the effect of surface etching to increase the adsorption capability followed by the extended surface area. We also found that the use of an oxidant during iodide adsorption can increase the loading significantly. The maximum activity of 137.90MBq/rod (3.7269mCi/rod) was achieved on the etched silver rods with phosphate ligand and hydrogen peroxide as an oxidant. In addition, this is 4.5-fold higher than that of the conventional chloride treatment method.

Lu-177 preparation for radiotherapy application

A separation study using a (176)Yb target for the preparation of nca (177)Lu, which is a beta-emitting nuclide used not only in radioimmunotherapy applications but also in the treatment of various lesions, has been performed. A material having a better selectivity and separation efficiency for Lu than Yb was developed, and the separation conditions of (177)Lu were derived using this from a neutron irradiated (176)Yb target. The separation material was an organo-ceramic hybrid material containing a phosphate group. Adsorption behavior was determined through batch experiments, and (177)Lu separation from the Yb target was evaluated through column experiments. The Yb target, with a 99.72% in (176)Yb, was irradiated in the irradiation hole of HANARO, which has a thermal neutron flux of 1.6E+14ncm(-2)s(-1). The batch experiments revealed that the organo-ceramic hybrid material (Sol-POS) had a separation factor of 1.6 at 0.5M HCl. Separation was performed through extraction chromatography using a 5mg enriched Yb target, and the separation yield of the NCA (177)Lu was about 78%. If the amount of Yb target is increased to produce curies level (177)Lu, additional purification will be needed.

Rationally designed spider web-like trivanadium heptaoxide nanowires on carbon cloth as a new class of pseudocapacitive electrode for symmetric supercapacitors with high energy density and ultra-long cyclic stability

The design and construction of one-dimensional (1D) nanostructures on flexible electrodes without the use of polymer binders/conductive additives has shown great potential for engineering improved electrochemical properties in supercapacitors. Herein, a facile in situ hydrothermal technique was adopted for the growth of trivanadium heptaoxide nanowires on carbon fiber cloth (V3O7/CFC). The resultant V3O7 sample displayed the self-accumulated growth of nanowires on CFC after 48 h with a spider web-like morphology. The specially designed binder-free V3O7/CFC was used to fabricate a symmetric supercapacitor in aqueous 1 M Na2SO4 electrolyte, which showed excellent electrochemical performance. Specifically, in the half-cell configuration, the device exhibited a maximum specific capacitance (Csp) of 198 F g−1 at 1 A g−1 and in full-cell configuration, it showed a Csp of 151 F g−1 at the same current density with ultra-high cycling stability of ∼97% (after 100 000 cycles). In addition, the performance of the symmetric device in 1 M 1-ethyl-3-methylimidazolium trifluoromethanesulfonate electrolyte was studied and it showed a wide potential window of 2 V with a maximum Csp of 178 F g−1. Furthermore, the device exhibited high energy and power densities of 24.7 W h kg−1 (48.5 mW h cm−2) and 5.13 kW kg−1 (10.05 W cm−2), representing as a viable electrode in ionic liquid electrolyte.