• Macromolecular Research
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• v.14 no.1
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• pp.73-80
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• 2006

Sulfonated poly(ethylene glycol) (PEG-$SO_{3}$) grafted polyrotaxanes (PRx-PEG-$SO_{3}$) were prepared in order to utilize the unique properties of PEG-$SO_{3}$ and the supramolecular structure of PRx, in which PEG-$SO_{3}$ grafted $\alpha$-cyclodextrins ($\alpha$-CDs) were threaded onto PEG segments in a PEG-b-poly(propylene glycol) (PPG)-b-PEG triblock copolymer (Pluronic) chain capped with bulky end groups. Some of the PRx-PEG-$SO_{3}$ demonstrated a higher anticoagulant activity in case of PRx-PEG-$SO_{3}$ (P 105), and compared with the control they showed a lower fibrinogen adsorption in PRx-PEG-$SO_{3}$ (F68) and a higher binding affinity with fibroblast growth factor. The obtained results suggested that polyrotaxane incorporated with PEG-$SO_{3}$ may be applicable to the surface modification of clinically used polymers, especially for blood/cell compatible medical devices.

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.412-417
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• 2023

There is increasing interest in the rapid and highly sensitive monitoring of cell viability in biological and toxicological research. Conventional methods depend on optical assays using Water Soluble Tetrazolium-8 (WST-8) or 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay, which requires a large volume of samples and special instruments, necessitating shipment of clinical samples to laboratories. This paper reports on the development of a rapid and sensitive electrochemical (EC) sensor using screen printed electrode (SPE) and surface modification using 4'-mercapto-N-phenylquinone diamine (4'-NPQD), as double electron mediators, for monitoring cell viability via the measurement of nicotinamide adenine dinucleotide (NADH). We used the sensor to observe the viability of MCF-7 and doxorubicin (Dox)-treated cells. The oxidation current of NADH was measured via chronoamperometry (CA), and the EC results showed a good linear relationship when compared with NADH quantification using WST-8 assay. The analysis time was only 10 s and limit of detection (LOD) of NADH was 1.78 µM. Our EC method has the potential to replace conventional WST assays for cell viability and cytotoxicity experiments.

• Tribology and Lubricants
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• v.37 no.3
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• pp.83-90
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• 2021

In this study, an ultrasonic nanocrystal surface modification (UNSM) was used to improve the mechanical properties, scratch resistance and tribological performance of Cu-based bimetals, which are usually used to manufacture sliding bearings and bushings for internal combustion engines (ICEs). Two different Cu-based bimetals, namely CuPb10Sn10 and CuSn10Bi7, were sintered onto a low carbon steel substrate. The mechanical properties and dry tribological performance using a tensile tester and micro-tribo tester were evaluated, respectively. The scratch resistance was assessed using a micro-scratch tester at an incremental load. The tensile test results showed that the yield strength (YS) and ultimate tensile strength (UTS) of both Cu-based bimetals increased after UNSM. Furthermore, the scratch and tribological tests results revealed that the scratch resistance and tribological performance of both Cu-based bimetals were improved by the application of UNSM. These improvements were mainly attributed to the eliminated pores, increased hardness and reduced roughness after UNSM. CuSn10Bi7 demonstrated better mechanical properties, scratch resistance and tribological performance than CuPb10Sn10. It was found that the presence of Bi in CuSn10Bi7 formed a Cu₁₁Bi₇ intermetallic phase, which is harder than Cu₃Sn. Hence, CuSn10Bi7 demonstrated higher strength and wear resistance than CuPb10Sn10. In addition, a CuSn10Bi7 formed both SnO₂ and Bi₂O₃ that prevented adhesion and improved the tribological performance. It can be expected that under dry tribological conditions, ICEs can utilize UNSM bearings and bushings made of CuSn10Bi7 instead of CuPb10Sn10 under oil-lubricated conditions.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.239-244
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• 2019

Two hydrogenation surface modifications, namely hydrogen atmosphere heat treatment and hydrogen plasma treatment, were found to lead to improved dispersion of nanodiamond (ND) seed particles and enhanced nucleation density for deposition of smooth ultrananocrystalline diamond (UNCD) film. After hydrogenation, the C-O and O-H surface functionalities on the surface of nanodiamond particles were converted to the C-H surface functionalities, and the Zeta potential was increased. As the degree of dispersion was improved, the size of nanodiamond aggregates decreased significantly and nucleation density increased dramatically. After hydrogen heat treatment at 600℃, average size of ND particles was greatly reduced from 3.5 ㎛ to 34.5 nm and a very high nucleation of ~3.9 × 10¹¹ nuclei/㎠ was obtained for the seeded Si surface.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.382-387
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• 2005

Polyvinylidene fluoride (PVDF) surface was irradiated and became superhydrophilic by low energy (180 eV) and high flux $(\~10^{15}/cm{\cdot}s)$ ion beam. As an ion source, a closed electron Hall drift thruster of $\phi=70mm$ outer channel size without grid was adopted. Ar, $O_2$ and $N_2O$ were used for source gases. When $N_2O^+$ and $O_2^+$ reactive gas ion beam were irradiated with the ion fluence of $5\times10^{15}/cm^2$, the wetting angle for deionized water was drastically dropped from $61^{\circ}\;to\;4^{\circ}\;and\;2^{\circ}$, respectively. Surface energy was also increased up to from 44 mN/m to 81 mN/m. Change of chemical component in PVDF surface was analyzed by x-ray photoelectron spectroscopy. Such a great increase of the surface energy was intimately related with the increase of hydrophilic group component in reactive ion irradiated PVDF surfaces. By using an atomic force microscopy, the root-mean-square of surface roughness of ion irradiated PVDF was not much altered compared to that of pristine PVDF.

• Journal of Adhesion and Interface
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• v.9 no.1
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• pp.9-15
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• 2008

EVA foam was treated by oxygen plasma under a various treatment time for surface modification. The effect of plasma treatment on surface properties of EVA foam was investigated in terms of FT-IR ATR, XPS, contact angle, and SEM analysis and the adhesion characteristic of the EVA foam was studied in peel strength. As a results, EVA foam treated by plasma led to an elimination of organic compound, an increase of oxygen content, and an increase of surface roughness, resulting in improving the adhesion properties of the EVA foam. As the plasma treatment time increased, the hydrophilicity and physical change of surface of the EVA foam were increased and showed maximum value at 180 s and 420 s, respectively. The maximum adhesion strength appeared at plasma treatment time of 420 s and therefore, in this study the physical change was thought to be a major factor for improving the adhesion of the EVA foam.

• Journal of Surface Science and Engineering
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• v.45 no.4
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• pp.151-154
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• 2012

A hydrophobic surface has been fabricated on aluminum by two-step surface treatment processes consisting of structure modification and surface coating. Nature inspired micro nano scale structures were artificially created on the aluminum surface by a blasting and Ar ion beam etching. And a hydrophobic thin film was coated by a trimethylsilane ($(CH_3)_3SiH$) plasma deposition to minimize the surface energy of the micro nano structure surface. The contact angle of micro nano structured aluminum surface with the trimethylsilane coating was $123^{\circ}$ (surface energy: 9.05 $mJ/m^2$), but the contact angle of only trimethylsilane coated sample without the micro nano surface structure was $92^{\circ}$ (surface energy: 99.15 $mJ/m^2$). In the hydrophobic treatment of aluminum surface, a trimethylsilane coated sample having the micro nano structure was more effective than only trimethylsilane coated sample without the micro nano structure.

• Journal of Surface Science and Engineering
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• v.38 no.3
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• pp.118-125
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• 2005

Low temperature plasma treatment with different gases and rf powers were performed to improve the adhesion strength between polytetrafluoroethylene(PTFE) and electroless deposited copper. According to the research, $H_2$ plasma having hydrogen radical was more effective in surface polarity modification than $O_2$ plasma due to the defluorination reaction. However, surface roughness of PTFE was more increased with $O_2$ than $H_2$ plasma. PTFE treated with $120W-O_2$ plasma and $250w-H_2$ plasma, consecutively showed rougher surface than single step $250w-H_2$ plasma treated one and more hydrophilic than single step $120W-O_2$ plasma treated one. And it showed 5B tape test grade, which is better adhesion property than 1B or 3B obtained by single step plasma treatment. In addition, adhesion strength between PTFE and Cu deposit is also deeply affected by residual water on its interface.

• Corrosion Science and Technology
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• v.13 no.5
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• pp.170-177
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• 2014

Polyurethane coating was designed to give a hydrophobic property on its surface by modifying it with hydroxyl terminated polydimethylsiloxane and then effects of surface hydrophobic tendency, water transport behavior and hence corrosion protectiveness of the modified polyurethane coating were examined using FT-IR/ATR spectroscopy, contact angle measurement and electrochemical impedance test. As results, the surface of polyurethane coating was changed from hydrophilic to hydrophobic property due primarily to a phase separation tendency between polyurethane and modifier by the modification. The phase separation tendency is more appreciable when modified by polydimethylsiloxane with higher content. Water transport behavior of the modified polyurethane coating decreased more in that with higher hydrophobic surface property. The decrease in the impedance modulus ${\mid}Z{\mid}$ at low frequency region in immersion test for polyurethane coatings was associated with the water transport behavior and surface hydrophobic properties of modified polyurethane coatings. The corrosion protectiveness of the modified polyurethane coated carbon steel generally increased with an increase in the modifier content, confirming that corrosion protectiveness of the modified polyurethane coating is well agreed with its water transport behavior.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2567-2569
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• 2014