• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1197-1202
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• 2003

Patterning of biological molecules was attempted on both gold and glass using fourth generation (G4) poly(amidoamine) (PAMAM) dendrimer as an interfacing layer between solid surfaces and biomolecules. As for the patterning of avidin and anti-biotin antibody on gold, PAMAM dendrimers representing amine functionalities were firstly printed onto the 11-mercaptoundecanoic acid SAM by microcontact printing, followed by biotinylation, and reacted with fluorescence-labeled avidin or anti-biotin antibody. Fluorescence microscopic analysis revealed that the patterns of avidin and anti-biotin antibody were well constructed with the resolution of < 2 ㎛. The PAMAM dendrimers were also printed onto aldehyde-activated slide glass and reacted directly with anti-BSA antibodies, which had been oxidized with sodium periodate. As a result, distinct patterns of the anti-BSA antibodies were also obtained with a comparable edge resolution to that of avidin patterns on gold. These results clearly show that PAMAM dendrimers can be adopted as an interfacing layer for the patterning of biological molecules on solid surfaces with micrometer resolution.

• Medical Lasers
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• v.8 no.2
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• pp.97-100
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• 2019

Facial pores are a visible topographic feature of skin surfaces and are generally the enlarged openings of pilosebaceous follicles. Enlarged facial pores can be a significant cosmetic problem, particularly for women. Recently, gold nanoshell-mediated photothermal therapy (PTT) has been reported to be effective in treating recurrent acne. The treatment of enlarged facial pores with gold nanoshell-mediated PTT produced excellent results with no side effects. The two cases reported here demonstrate the possibility of gold nanoshell-mediated PTT as a safe and effective treatment for enlarged facial pores.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.3-8
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• 2000

Chemical nature of nascent metal surfaces which is one of the important active sources for tribochemical reactions was investigated using a newly developed method. Some enhanced activities were observed. For example, organic compounds chemisorbed on nascent gold surfaces and aromatic compounds decomposed on nascent nickel surfaces resulting in hydrogen evolution. Non-polar compounds such as organic sulfides had a higher chemisorption activity on nascent steel surfaces than polar compounds such as fatty acids and phosphates. Organic sulfides reacted directly with nascent steel surfaces and the surface was covered with metal sulfides. The activity for the chemisorption of organic compounds was closely dependent on the electronic structure of metals. Although benzene chemisorbed very easily on nascent surfaces of transition metals, it did not chemisorb ell nascent surfaces of simple metals. Boundary lubricating behaviors of extreme pressure additives were explained on the bases of the chemical activities of nascent surfaces obtained in this investigation. Under mild conditions, polar compounds such as fatty acids and phosphates were effective for boundary lubrication, because surfaces are covered with oxide layers. On the other hand, sulfides were more effective under severe conditions where the oxide layers were removed and the nascent surfaces were formed.

• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.83-89
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• 2012

We investigate the electrocatalytic activities for oxygen reduction at nanoporous gold (NPG) surfaces fabricated by selective dissolution of Ag from electrodeposited Ag-Au layers on electrode surfaces. The structure of NPG was controlled by changing the concentration ratios of precursor metal complexes during the electrodeposition of Ag-Au layers and the corresponding surface morphology and surface area was examined. NPG structures with Ag/Au ratio of 2.0 exhibited the highest electrocatalytic activity for oxygen reduction, where the nanoporous structure plays a key role, but the surface area does not affect on the electrocatalytic activity. The mechanism of electroreduction of oxygen was investigated by rotating disk electrode techniques. In acidic media, oxygen was first reduced to hydrogen peroxide followed by further reduction to water through 2-step 4-electron mechanism, whereas the oxygen was reduced directly to water by 4-electron mechanism in basic media.

• Polymer Science and Technology
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• v.23 no.1
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• pp.21-28
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• 2012

• Bulletin of the Korean Chemical Society
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• v.15 no.5
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• pp.339-340
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• 1994

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.213-223
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• 2007

The success of a porcelain fused to metal (PFM) restoration depends upon the quality of the porcelain-metal bond. The adhesion between metal substructure and dental porcelain is related to the diffusion of oxygen to the reaction layer formed on cast-metal surface during firing. The purposed of this investigation was to study the effects of gold based bonding agent on Ni-Cr alloy-ceramic adhesion between porcelain matrix, gold based bonding agent and metal substructure interface. gold based bonding agent have been applied as an intermediate layer between a metal substructure and a ceramic coating. gold based bonding agent(Aurofilm NP, Metalor, Swiss) was applied on Ni-Cr alloy surface by four method. Surfaces only air abraded with 110${\beta}\neq$ Al2O3 particles were used as control. metal ceramic adhesion was evaluated by a biaxial flexure test(N=5) and volume fraction of adherent porcelain was determined by SEM/EDS analysis. Result of this study suggest that the layering sequence of gold based bonding agent is very important and can improve porcelain adherence to PFM.

• Korean Journal of Materials Research
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• v.34 no.4
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• pp.194-201
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• 2024

In this study, the surfaces of two gold nanoparticles of different shapes were modified with hexadecyltrimethylammonium bromide (CTAB) and used for contact lenses. The polymer was based on 2-hydroxyethyl methacrylate (HEMA), and spherical and sea urchin-shaped gold nanoparticles were used as additives. CTAB was used to modify the surface of the sea urchin-shaped gold nanoparticles. To analyze the physical properties of the prepared contact lens, optical transmittance, refractive index, water content, contact angle, and atomic force microscope (AFM) were measured and evaluated. The results showed the nanoparticles did not significantly affect optical transmittance, refractive index, or water content of the lens, and tensile strength increased according to the ratio of the additive. The addition of the sea urchin-shaped nanoparticles resulted in lower wettability compared with the spherical nanoparticles, but somewhat superior tensile strength. In addition, it was found that the wettability of the lens was improved when the surface-modified sea urchin-shaped gold nanoparticles were added. The types of gold nanoparticles and surface modification methods used in this study are considered to have great potential for use in ophthalmic materials.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.4
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• pp.645-661
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• 1995

As the mechanical property of composite resin improved, composite resin has been widely used esthetic dentistry. In the field of esthetic dentistry, the color of prosthetic material is very important. The purpose of this study was to evaluate the color difference of specimens, by the types of alloys and gold electrodeposit. Experimental groups were as follows : Group Prec : Au-Pt alloy with no gold coating and no resin veneer. Group Semi : Pd-Ag alloy with no gold coating and no resin veneer. Group BAse : Ni-Cr alloy with no gold coating and no resin veneer. Group Gsem : Pd-Ag alloy with no gold coating and no resin veneer. Group Gbas : Ni-Cr alloy with no gold coating and no resin veneer. Group PreR : Resin veneer on the Pd-Ag alloy without gold coating. Group SemR : Resin veneer on the Pd-Ag alloy without gold coating. Group GbsR : Resin veneer on the Ni-Cr alloy with gold coating Group BasR : Resin veneer on the Ni-Cr alloy without gold coating. In this study, colors of metal surfaces and veneered resins were evaluated by the CIE $L^{*}a^{*}b$ system. The results obtained were as follows : 1. different alloy types and gold coating make the $L^{*}a^{*}b$ system. 2. The ${\Delta}E^*$ab value between groups semi and Base was less than 1.5 and there was no $a^*$ and $b^*$ value difference between groups Gsem and Gbas 3. The values of $L^*$ and $a^*$ ain groups GsemR and GbasR were so similar that the ${\Delta}E^*$ab value was as small as 0.58. 4. In resin specimens with gold coated semiprecious or base alloys showed yellower and redder deviation than the resin specimens with precious alloy. 5. The ${\Delta}E^*$ab values between goups PreR-GsemR and groups PreR-GbasR were as small as 2.68 and 2.22 respectively.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.69-75
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• 2008

Tautomerism of pyrimidine base cytosine has been comparatively examined on nanoparticle and roughened plate surfaces of silver, gold, and copper by surface-enhanced Raman scattering (SERS). The SERS spectrum was found to be different depending on the metals and their substrate conditions suggesting the dissimilar population of various tautomers of cytosine on the surfaces. The ab initio calculations were performed at the levels of B3LYP, HF, and MP2 levels of theory with the LanL2DZ basis set to estimate the energetic stability of the tautomers with the metal complexes as well as the gas phase state. The amino group and N3-coordinated tautomer was predicted to be more favorable for bonding to Au, whereas the hydroxyl and N1-coordinated zwitter ionic form is most stable with Ag and Cu as a bidentate form from the DFT calculation. The binding energy with the Ag atom is calculated to be smaller than those with the Au and Cu atoms in line with the temperature-dependent SERS spectra of cytosine.