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Hyoung Kun Park

Publications and source records attributed to Hyoung Kun Park.

6 recordsLinked to original sources
PubMed2006

Facile method to prepare surface-enhanced-Raman-scattering-active Ag nanostructures on silica spheres.

In this paper we describe a very simple electroless plating method used to prepare Ag-coated silica beads. Robust Ag nanostructures can be reproducibly fabricated by soaking silica beads in ethanolic solutions of AgNO(3) and butylamine. When the molar ratio of butylamine to AgNO(3) is far below 1.0, distinct nanosized Ag particles are formed on the silica beads, but by increasing the amount of butylamine, network-like Ag nanostructures are formed that possess very broad UV/vis absorption characteristics extending from near-UV to near-infrared regions. In conformity with the UV/vis absorption characteristics, the Ag-deposited silica beads were highly efficient surface-enhanced Raman scattering (SERS) substrates, with the enhancement factor estimated using benzenethiol as a model adsorbate to be larger than 10(6). Since another silica layer can be readily deposited onto the Ag surface, the Ag-coated silica beads should be invaluable in the development of SERS-based biosensors.

Journal Article↗
PubMed2006

microAg particle-based molecular sensing/recognition via surface-enhanced Raman spectroscopy.

In this study, we demonstrate that powders of commercially available 2-microm-sized Ag (microAg) can be used as a core material for constructing molecular sensing/recognition units operating via surface-enhanced Raman scattering (SERS). This is possible because microAg powders are very efficient substrates for both the infrared and Raman-spectroscopic characterization of molecular adsorbates prepared in a similar manner on silver surfaces. The Raman spectrum of organic monolayers on powdered silver is a SERS spectrum. The agglomeration of microAg particles in a highly concentrated buffer solution could be prevented by the deposition of polar molecules like 1,4-phenylenediisocyanide (1,4-PDI), and mixed self-assembled monolayers of 1,4-PDI and N-(+)-biotinyl-6-aminocaproic acid on microAg particles were then confirmed via the SERS of 1,4-PDI to selectively recognize the avidin arrays formed on a separate biotinylated substrate. According to a dose response curve, avidin at >10(-6)g/mL could be easily identified by the present method. In addition, the non-specific adsorption of microAg particles was found to be negligibly small, probably because the Ag particles were too heavy to be retained on organic substrates solely by non-specific interaction.

Avidin↗
PubMed2006

Silver-particle-based surface-enhanced Raman scattering spectroscopy for biomolecular sensing and recognition.

In this study, we demonstrate that 2-microm-sized Ag (microAg) powders can be used as a core material for constructing molecular sensing/recognition units operating via surface-enhanced Raman scattering (SERS). This is possible because microAg powders are very efficient substrates for both the infrared and Raman-spectroscopic characterization of molecular adsorbates prepared in a similar manner on silver surfaces; we can obtain an infrared spectrum of organic molecules adsorbed on microAg particles with a very high signal-to-noise ratio by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and the Raman spectrum of organic monolayers on powdered silver is an SERS spectrum. The agglomeration of microAg particles in a highly concentrated buffer solution could be prevented by the layer-by-layer deposition of cationic and anionic polyelectrolytes such as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). In fact, prior to depositing PAA and PAH, 4-aminobenzenethiol (4-ABT) was assembled on the surfaces of the microAg particles as SERS markers. Because of the presence of amine groups of 4-ABT, PAA could be readily deposited on the microAg particles. On the other hand, the outermost PAA layer could also be derivatized with biotin-derivatized poly(L-lysine). The nonspecific interaction of poly(L-lysine) with proteins could be suppressed by grafting poly(ethylene glycol) into the biotin-derivatized poly(L-lysine) molecules. On the basis of the nature of the SERS peaks of 4-ABT, it was confirmed that these biotinylated microAg powders were effective in selectively recognizing the streptavidin arrays. Because a number of different molecules can be used as SERS-marker molecules, such as probable 4-ABT, commercially available microAg powders must be a prospective material in molecular sensing/recognition, particularly via SERS.

Acrylic Resins↗
PubMed2006

Novel fabrication of Ag thin film on glass for efficient surface-enhanced Raman scattering.

This paper describes a very simple electroless-plating method used to prepare optically tunable nanostructured Ag films. Very stable Ag films can be reproducibly fabricated simply by soaking glass substrates in ethanolic solutions of AgNO3 and butylamine. The grain size of silver can be readily controlled to range from 20 to 150 nm, and these nanostructural features correlated well with their UV/vis absorption characteristics, as well as with their surface-enhanced Raman scattering (SERS) activities. It is also very advantageous that the Ag films prepared exhibit very even SERS activity over an area up to hundreds thousand square-micrometers, and the enhancement factor estimated using benzenethiol as a prototype adsorbate reaches approximately 2 x 10(5). Since the proposed method is cost-effective and is suitable for the mass production of diverse Ag films irrespective of the shapes of the underlying substrates, it is expected to play a significant role in the development of surface plasmon-based analytical devices.

Journal Article↗
PubMed2004

Gelation of octadecyltrimethoxysilane at the air/water interface: effect of perfluorotetradecanoic acid and divalent cadmium ions.

The effect of an acidic surfactant, perfluorotetradecanoic acid (PFTDA), on the gelation of octadecyltrimethoxysilane (ODTMS) monolayers at the air/water interface was investigated using a Langmuir film balance, attenuated total reflection (ATR) infrared spectroscopy, and atomic force microscopy (AFM). The gelation of ODTMS was greatly accelerated by adding only 2 mol % PFTDA into the monolayer; in this case, the hydrolysis of ODTMS was completed within a few minutes, whereas otherwise it took 18 h. ATR-IR spectroscopy clearly demonstrated that the gelation of a 49:1 ODTMS/PFTDA monolayer proceeded on a pure water subphase mainly via hydrolysis followed by condensation. In the presence of PFTDA, the local acidity at specific sites is presumed to be very high, catalyzing the hydrolysis of ODTMS. The extremely fast rate is attributed not only to the lateral diffusion of PFTDA in the mixed monolayer but also to proton propagation where the proton(s) involved in the initial hydrolysis are transposed rapidly to the nearby methoxy groups for subsequent hydrolysis. The catalytic activity of PFTDA can be neutralized, however, simply by the addition of multivalent metallic ions such as Cd2+ to form saltlike complexes with PFTDA; the rate of 2-D sol-gel processes can thus be easily regulated by a minute amount of PFTDA and/or Cd2+ added into the reaction system.

Journal Article↗