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Yanggu, South Korea

Noh J.,Seoul National University | Park S.,Nomadien Corporation | Kim H.C.,Seoul National University | Chung T.D.,Seoul National University
Bulletin of the Korean Chemical Society

A disposable solid-state pH sensor was realized by utilizing two nanoporous Pt (npPt) electrodes and a copolyelectrolytic junction. One nanoporous Pt electrode was to measure the pH as an indicating electrode (pH-IE) and the other assembled with copolyelectrolytic junction was to maintain constant open circuit potential (Eoc) as a solid-state reference electrode (SSRE). The copolyelectrolytic junction was composed of cationic and anionic polymers immobilized by photo-polymerization of N,N'-methylenebisacrylamide, making buffered electrolytic environment on the SSRE. It was expected to make. The nanoporous Pt surrounded by a constant pH excellently worked as a solid state reference electrode so as to stabilize the system within 30 s and retain the electrochemical environment regardless of unknown sample solutions. Combination between the SSRE and the pH-IE commonly based on nanoporous Pt yielded a complete solid-state pH sensor that requires no internal filling solution. The solid state pH sensing chip is simple and easy to fabricate so that it could be practically used for disposable purposes. Moreover, the solid-state pH sensor successfully functions in calibration-free mode in a variety of buffers and surfactant samples. Source

Han J.-H.,Seoul National University | Lee E.,Kwangwoon University | Park S.,Nomadien Corporation | Chang R.,Kwangwoon University | Chung T.D.,Seoul National University
Journal of Physical Chemistry C

Geometric factors affecting the enhanced electrocatalysis on nanoporous Pt (L2-ePt) were examined by electrochemical methods and computer simulations. The experimental results revealed that the electrochemical enhancement of O2 and H2O2 does not come only from expansion of the active surface area (so-called roughness factor, f R) of L2-ePt. The presence of extra contribution was verified by the fact that significant enhancement in electrocatalytic reactions remained even after the effect of the fR was eliminated from the electrochemical redox behavior of O2 and H2O2 on L2-ePt electrodes. Not only the voltammetric observation but also potentiometric pH responses of L2-ePt suggested the presence of unique nanoporous effects other than the surface enlargement in regard to heterogeneous electrochemical reactions. L2-ePt showed near Nernstian behavior, faster response time, and less hysteresis even if the real surface area was smaller than that of flat Pt. Increased residence time near the electrode surface due to extremely confined space of nanoporous structure was proposed as possible origins and examined by the Monte Carlo simulations of simple model electrodes. The theoretical approaches indicated that long residence time of reactant at electrode surface by confinement effect of the nanoporous environment well accounted for the experimental results. © 2010 American Chemical Society. Source

Lee S.,Seoul National University | Joo S.,University of Ulsan | Park S.,Nomadien Corporation | Kim S.,Seoul National University | And 2 more authors.

In this study, in situ surface-enhanced Raman scattering (SERS) decoding was demonstrated in microfluidic chips using novel thin micro gold shells modified with Raman tags. The micro gold shells were fabricated using electroless gold plating on PMMA beads with diameter of 15 μm. These shells were sophisticatedly optimized to produce the maximum SERS intensity, which minimized the exposure time for quick and safe decoding. The shell surfaces produced well-defined SERS spectra even at an extremely short exposure time, 1 ms, for a single micro gold shell combined with Raman tags such as 2-naphthalenethiol and benzenethiol. The consecutive SERS spectra from a variety of combinations of Raman tags were successfully acquired from the micro gold shells moving in 25 μm deep and 75 μm wide channels on a glass microfluidic chip. The proposed functionalized micro gold shells exhibited the potential of an on-chip microfluidic SERS decoding strategy for micro suspension array. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA. Source

Park S.,Nomadien Corporation | Song Y.J.,Seoul National University | Han J.-H.,Seoul National University | Boo H.,Seoul National University | Chung T.D.,Seoul National University
Electrochimica Acta

The morphologies, roughness factors, and thicknesses of 3D nanoporous Pt (3D-npPt) films were investigated in terms of electroplating conditions. The electrochemical behaviors of 3D-npPt films with regard to electrochemical glucose oxidation, O2 reduction, and H2O2 reduction were investigated as a function of roughness factors (Rf). Close comparison of glucose oxidation on 3D-npPt and 1D nanoporous Pt (1D-npPt) showed that the overall electrode activity of 3D-npPt is significantly higher than that of 1D-npPt. Electrochemical impedance analysis based on transmission line theory confirmed a substantially low pore resistance of 3D-npPt, which may account for the superior electrode response of this material. © 2009 Elsevier Ltd. All rights reserved. Source

Piao L.,Seoul National University | Park S.,Nomadien Corporation | Lee H.B.,Seoul National University | Kim K.,Seoul National University | And 2 more authors.
Analytical Chemistry

We finely tuned the Au shell on a polystyrene microsphere of 2 μm in diameter to achieve a strong surface enhanced raman scattering (SERS)-active platform so that the molecules on a single microspherical shell surface produce their own fingerprint SERS spectra. The proposed microshells can be easily and individually manipulated under a conventional optical microscope using a micropipet and act as a sensitive probe to obtain the SERS spectra of the monolayer of molecules on Pt as well as Au surfaces without any requirement of special surface morphology or modification for inducing SERS activity. Well-defined SERS spectra can be obtained at a very short acquisition time of milliseconds, suggesting useful applications of the present system based on the decoding of the SERS-active barcodes on individually functionalized microshells. © 2010 American Chemical Society. Source

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