Faculty Profiles - SAITO, Nagahiro

Papers - SAITO, Nagahiro

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Study of protein adsorption onto a polymer film by in-situ UV attenuated total reflectance spectroscopy

Bratescu M., Fujita S., Saito N., Takai O.

Materials Research Society Symposium Proceedings Vol. 1138 page： 60 - 66 2009.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Research Society Symposium Proceedings

Our work presents results on human plasma protein adsorption onto a polyacrylic acid (PAA) film prepared via surface wave plasma (SWP) induced graft polymerization. The PAA film prepared in this manner is characterized by a carboxyl functional group and a constant contact angle in water of 35°. The adsorption kinetics of human plasma fibrinogen (HPF) and human serum albumin (HSA) proteins were measured by in-situ UV-ATR spectroscopy. The free energy of adsorption on PAA treated as well as untreated surfaces was -28 kJ M -1 and -22 kJ M-1 for HPF and HSA, respectively, regardless of surface chemistry. We determined that 14 μM and 6 μM HPF concentrations are enough to cover half of the maximum possible of surface coverage on silica and PAA film, respectively. HSA protein concentrations of 154 μM and 118 μM are enough to cover half of the maximum accessible surface of silica and PAA film, respectively. For surface treatment of implants with PAA polymer and protein, the necessary protein concentration for effective surface coverage should be known. © 2009 Materials Research Society.

Biomimetic materials processing

Ishizaki T., Hieda J., Bratescu M.A., Saito N., Takai O.

Proceedings of SPIE - The International Society for Optical Engineering Vol. 7404 2009.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of SPIE - The International Society for Optical Engineering

A biomimetic super-hydrophobic/super-hydrophilic micro-patterned surface was successfully fabricated by microwave plasma enhanced chemical vapor deposition (MPECVD) and vacuum ultraviolet (VUV) light lithography. On the micropatterned surface, various site-selective immobilizations were carried out. The fluorescent polystyrene spheres and copper were deposited site-selectively on super-hydrophobic regions using electrostatic interactions. The micropatterned surface brought the discrete adhesions of E. coli and B. subtilis specifically on super-hydrophobic regions. On the other hand, NIH 3T3 fibroblast cells attached to the super-hydrophilic regions in a highly selective manner. © 2009 SPIE.

DOI： 10.1117/12.829207

Fabrication of microtemplates for the control of bacterial immobilization

Miyahara Y., Mitamura K., Saito N., Takai O.

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films Vol. 27 ( 5 ) page： 1183 - 1187 2009.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

The authors described a region-selective immobilization methods of bacteria by using superhydrophobic/superhydrophilic and superhydrophobic/poly(ethylene glycol) (PEG) micropatterns for culture scaffold templates. In the case of superhydrophobic/superhydrophilic micropatterns, the superhydrophobic surface was prepared first by microwave-plasma enhanced chemical vapor deposition (MPECVD) from trimethylmethoxysilane. Then the superhydrophilic regions were fabricated by irradiating the superhydrophobic surface with vuv light through a stencil mask. In the case of the superhydrophobic/PEG micropatterned surfaces, PEG surfaces were fabricated first by chemical reaction of ester groups of p -nitrophenyl PEG with N H2 group of N H2 -terminated self assembled monolayer from n -6-hexyl-3-aminopropyltrimethoxysilane. The superhydrophobic regions were fabricated by MPECVD thorough a stencil mask. In this study four bacteria were selected from viewpoint of peptidoglycan cell wall (E. coli versus B. subtilis), extracellular polysaccharide (E.coli versus P. stutzeri, P. aeruginosa), and growth rate (P. stutzeri versus P. aeruginosa). The former micropattern brought discrete adhesions of E. coli and B. subtilis specifically on the hydrophobic regions, Furthermore, using the superhydrophobic/PEG micropattern, adhesion of bacteria expanded for E. coli, B. subtilis, P. stutzeri, and P. aeruginosa. They observed a high bacterial adhesion onto superhydrophobic surfaces and the inhibitive effect of bacterial adhesion on PEG surfaces. © 2009 American Vacuum Society.

DOI： 10.1116/1.3179158

Surfactant-assisted fabrication of tin oxide nanowires through one-step electrochemically induced chemical deposition

Ishizaki T., Saito N., Takai O.

Journal of the Electrochemical Society Vol. 156 ( 10 ) 2009.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of the Electrochemical Society

Tin oxide nanowires were successfully fabricated at the potentials of -0.6 to -0.8 V from nitric acid electrolytes containing 20 mM tin dichloride, 100 mM sodium nitrate, 75 mM nitric acid, and 5 mM sodium dodecyl sulfate (SDS) through a one-step electrochemically induced chemical deposition. The addition of SDS surfactant to the nitric acid electrolyte led to a dramatic change in the shapes of the deposits, resulting in the formation of the tin oxide nanowires. Field emission scanning electron microscope and tunneling electron microscope images of the deposits showed that the diameter and the length of the tin oxide nanowires were within the range of 30-400 nm and several tens to hundreds of micrometers, respectively. X-ray diffraction and the selected area electron diffraction patterns of the deposits revealed that the tin oxide nanowire had a polycrystalline tetragonal structure. The shapes of the obtained samples changed with the SDS surfactant concentrations. The formation mechanism of the tin oxide nanowires is also discussed. © 2009 The Electrochemical Society.

DOI： 10.1149/1.3190161

Characterization of platinum catalyst supported on carbon nanoballs prepared by solution plasma processing

Ichin Y., Mitamura K., Saito N., Takai O.

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films Vol. 27 ( 4 ) page： 826 - 830 2009.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

In order to improve the energy-conversion efficiency in fuel cells, the authors loaded Pt nanoparticles on carbon nanoballs (CNBs) by using solution plasma processing (SPP) involving CNB and Pt ion with a protection group. In this study, we employed poly(vinylpyrrolidone) (PVP) or sodium dodecyl sulfate (SDS) to prepare Pt nanoparticles supported on CNB (Pt/CNB) by the SPP, and the electrochemical properties as a catalyst was evaluated by cyclic voltammetry. The carbon nanoballs were prepared by thermal decomposition process of ethylene and hydrogen gases. Color of the solution changed from yellow to dark brown as synthesis time. This change indicates the improvement of dispersibility of CNB. Moreover, transmission electron microscopy images and elemental mapping images showed the Pt nanoparticles supported on CNB. A catalytic activity of the Pt/CNB in use of SDS was shown to be higher than the Pt/CNB prepared with PVP system. The SDS-containing Pt/CNB also showed the higher activity than that obtained by the conventional method. © 2009 American Vacuum Society.

DOI： 10.1116/1.3077285

Surface modification of gold nanorods by organosilanes

Mitamura K., Imae T., Saito N., Takai O.

Composite Interfaces Vol. 16 ( 4 ) page： 377 - 385 2009.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Composite Interfaces

Gold nanorods protected by hexadecyltrimethylammonium bromide were treated by an organosilane, aminopropyltriethoxysilane (APS) or vinyltrimethoxysilane (VS) in the presence of mercaptopropyltrimethoxysilane (MPS) serving as a binder. After the APS- or VS-treatment, a shell about 4 nm thick surrounding the nanorods was found by means of transmission electron microscopy. Its formation enabled the nanorods to be dispersed in polar media (ethanol, methanol, acetone and acetonitrile/water mixtures). © 2009 VSP.

DOI： 10.1163/156855409X447138

Self-assembly of human plasma fibrinogens on binary organosilane monolayers with micro domains

Lee S., Saito N., Takai O.

Applied Surface Science Vol. 255 ( 18 ) page： 7912 - 7917 2009.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Surface Science

The adsorption behavior and self-assembly of human plasma fibrinogen (HPF) on binary methyl- and amino-terminated self-assembled monolayers (SAMs) were investigated by atomic force microscopy (AFM). The binary SAMs were fabricated through self-assembly mechanism of organosilane molecules. The height of domains is the domain height is 0.8 ± 0.2 nm from the AFM topographic image. It corresponds to the domain height is 0.8 ± 0.2 nm from the AFM topographic image. It corresponds to the difference between the length of the alkyl chain of octadecyltrichlorosilane (OTS) and that of n-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS). The fibrinogen solution used ultrapure water as the solvent and its pH was adjusted at 3 and 10. From the AFM results at pH 3, HPF only formed network structures on the OTS domains of the binary SAM at early immersion times, and then the network structures expanded and connected between OTS domains through the AHAPS surface at long immersion times. In this case, a few HPFs are discretely adsorbed on the AHAPS surface. However, HPF is uniformly adsorbed on the binary SAM under the other conditions of pH. © 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2009.04.201

Highly reproducible technique for three-dimensional nanostructure fabrication via anodization scanning probe lithography

Lee S.H., Saito N., Takai O.

Applied Surface Science Vol. 255 ( 16 ) page： 7302 - 7306 2009.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Surface Science

The effects of coated materials for Si probes on the sizes of line structure by using anodization scanning probe lithography (SPL) are investigated by using atomic force microscopy (AFM). Anodization SPL was carried out on the 1-decane monolayer directly attached to hydrogen-terminated silicon. Gold-coated, diamond-coated, and uncoated Si probes were used as the SPL probes in order to fabricate line structures of silicon oxide. In the cases of Au-coated and uncoated Si probes, the widths of line structures are widely influenced by the changes of scanning rate and applied bias voltage. However, the line width fabricated by use of the diamond-coated probe maintained 15 nm under any condition of scanning rate and applied bias voltage. One of the most narrow and three-dimensional nanostructures is found to be successfully fabricated on the hydrogen-terminated Si substrates when the diamond-coated probe was used as a probe of anodization SPL. In addition, this result indicated that high reproducibility of oxide nanostructures is attainable by anodization SPL used the diamond-coated probe. © 2009.

DOI： 10.1016/j.apsusc.2009.03.087

Adsorption of protein on polyelectrolyte brush surface

Higuchi, A; Tatematsu, H; Fujima, T; Saito, N; Takai, O

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 237 2009.3

Chemical dynamics of protein adsorption and desorption on regulated surfaces in aqueous solutions

Saito, N; Hieda, J; Takai, O

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 237 2009.3

Bioreorganization surface with hierarchical structure

Takai, O; Saito, N; Sato, H; Miura, Y; Kobayashi, K

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 237 2009.3

Effects of humidity on the friction coefficient of diamond-like carbon (DLC) coating

Kim S.G., Cho Y.K., Jang W.S., Kim S.W., Nagahiro S., Takai O.

Journal of the Korean Physical Society Vol. 54 ( 3 ) page： 1228 - 1236 2009.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of the Korean Physical Society

A diamond-like Carbon (DLC) coating has been known to be a good tribological problem solver due to its low friction characteristics and high hardness. The friction coefficient values shown in the literature surveyed differ from the authors' due to different test conditions. When we plot these results and our own with the variable of humidity, the friction coefficient decreases with increasing environmental humidity. By using contact angle measurements to study the interface properties of these coatings, we conclude that this change comes from the hydrophilic and the hydrophobic properties of the surface and the eventual change of the wear mode. DLC films were deposited on SKD11 steel by using pulsed (DC PECVD) (a-CH, hydrogenated DLC, Si-containing DLC) and amorphous carbon filtered arc DLC (a-C, non-hydrogenated DLC). Deposited DLCs were tested according to humidity by using a tribometer. We used a SUJ2 (JIS standard) steel ball bearing for the counterpart of wear test. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and surface roughness testers were used for surface analysis of the DLC and the wear trace. The Raman spectra of the films showed that the carbon bonding structures changed according to the I(D)/I(G) intensity ratio for the wear trace at severe wear conditions. In normal humidity, 30-85 % RH, the DLC had a friction coefficient lower than it did in 5 % RH. In this case, the Si-containing hydrogenated DLC definitely had the lowest friction coefficient. Eventually, it also had the lowest contact angle, as expected. When we investigated two different kinds of DLCs in terms of hydrogen content, we observed the same effect of relative humidity on friction behavior.

DOI： 10.3938/jkps.54.1228

Friction behavior of diamond-like carbon coating with relative humidity

Kim S., Saito N., Otake N., Kim S., Takai O.

Proceedings of the 17th IFHTSE Congress Vol. 1 page： 373 - 376 2009

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of the 17th IFHTSE Congress

Owing to the intrinsic beneficial tribological properties of DLC coating, it has attracted many researcher's interest in better understanding of wear phenomena. In this study, DLC films show a tendency to decrease the friction coefficient value as the humidity increases. These results come from a change in the hydrophilic and hydrophobic properties of DLC films through the evolution of the contact angle of interface with humidity. DLC films were deposited on SKD11 steel by filtered arc DLC (a-C, non-hydrogenated DLC) and pulsed DC PECVD (a-C:H, hydrogenated DLC and Si-containing hydrogenated DLC). Wear tests of the DLC films were carried out with a ball-on- disk tribometer machine in different level of humidity. In contrast to what had been expected, the wear volume of a-C:H DLC, which has the lower friction coefficient than a-C DLC, seems important the wear were occurred through first adhesive wear type and followed by producing small-sized DLC debris between the tribology system and finally the abrasive mode. In the case of the non-hydrogenated DLC wear test at the same condition, microscopic observation showed that the final abrasive wear occurred through the sliding small-size hydrophobic debris formed between the steel counter partner and the DLC coating layer. At the same humidity condition, the Si-containing hydrogenated a-C:H DLC showed different wear behavior that was caused by hydrophilic agglomerated debris. A large area seemed to be worn away for the DLC films and eventually Fe<inf>3</inf>O<inf>4</inf> comes out with Fe<inf>3</inf>O<inf>4</inf>from the substrate. Even though, the friction coefficient of hydrogenated DLC was lower, the wear loss seemed to be more severe due to the agglomeration of debris and the wear mode shift in the dry condition evaluation of tribological characteristic of DLC cannot be done by a simple index. The other side, at the normal humidity (30-85% RH) condition, the Si-containing hydrogenated DLC showed a very low friction coefficient with small wear volume compared to the dry condition. In a similar manner the non-hydrogenated DLC showed a gradual lower friction coefficient as the humidity increased.

Morphological control of vertically self-aligned nanosheets formed on magnesium alloy by surfactant-free hydrothermal synthesis

Ishizaki, T; Cho, SP; Saito, N

CRYSTENGCOMM Vol. 11 ( 11 ) page： 2338 - 2343 2009

High frequency bipolar pulsed spark electrohydraulic discharge characteristics and plasma parameters of liquid solution plasmas

Miron C., Chang J.S., Takeda T., Saito N., Takai O.

GD 2008 - 17th International Conference on Gas Discharges and Their Applications page： 489 - 492 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：GD 2008 - 17th International Conference on Gas Discharges and Their Applications

An experimental investigation has been conducted to study fundamental electrohydraulic discharge characteristics and plasma parameters of liquid solution plasmas. HF-bipolar high voltage was supplied to the rod-to-rod type plate electrodes with a few mm gap distance inside water with conductive KCl or Na2SO4 solutions. Experiments are conducted for applied maximum voltage from 1 to 6 kV, the electrode gap distances from 0.3 to 5 mm and for the operating frequency from10 to 15 kHz. Plasma parameters was determined by the optical emission spectroscopy with LTE model and compared with the discharge channel averaged plasma parameter from discharge characteristics. The results show that a stable, liquid solution plasma can be generated by HF PSED. Based on optical emission spectra, a significant hydrogen gas was generated in a spark discharge channel. Morphology of liquid solution plasma and transient plasma density behavior will be discussed in detail.

Reaction Dynamics for Gold Nanoparticles Synthesis in Solution Plasma

Hieda J., Saito N., Takai O.

Materials Research Society Symposium Proceedings Vol. 1056 page： 221 - 226 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Research Society Symposium Proceedings

We describe the dynamics of the synthesis of gold nanoparticles by glow discharge in aqueous solutions. Initial [AuCl4]- concentration and the voltage applied between the electrodes were varied. Reduction rates were calculated from changes in concentration of [AuCl 4]- vs. discharge time. A pulsed power supply was used to generate discharges in the aqueous solutions. The morphology of the nanoparticles obtained was observed by transmission electron microscopy (TEM). [AuCl4]- was reduced by H radicals or electrons generated by the discharge. Dendrite-shaped nanoparticles -150 nm in size were formed after discharge for 1 mm. The pH of the solution decreased gradually with increasing discharge time. The decrease in pH led to dissolution of gold nanoparticles. The reduction and dissolution rates increased proportionately with the applied voltage. The size of gold nanoparticles decreased during discharge and was 20 nm after discharge for 45 mm. When the reduction rate lowered as a result of dissolution, anisotropic nanoparticles were formed and continued to grow in the solution. © 2008 Materials Research Society.

Fundamental electrohydraulic discharge characteristics and plasma parameters of dielectric liquid dodecane with Ar gas injections for gold nano-particle fabrications

Hieda J., Chang J.S., Saito N., Takai O.

2008 IEEE International Conference on Dielectric Liquids, ICDL 2008 2008.11

Language：English Publishing type：Research paper (scientific journal) Publisher：2008 IEEE International Conference on Dielectric Liquids, ICDL 2008

An experimental investigation has been conducted to study a fundamental electrohydraulic discharge characteristics and plasma parameters in a dielectric liquid solution with Ar gas injections. HF-bipolar high voltage was supplied to the converging angle type plate electrodes with 1mm gap distance inside dodecane with conductive salt solutions. Experiments are conducted for Ar gas flow rate from 0.1 to 1 L/min., applied maximum voltage from 10 to 60 kV for the operating frequency fromlO to 15 kHz. The results show that HF PSED can be generated relatively stable discharge even in the dielectric fluid and gold nano-particles were fabricated. Morphology of liquid solution plasma and transient plasma density behavior will be discussed in detail.

DOI： 10.1109/ICDL.2008.4622477

Nano/Micro Patterning of Inorganic Thin Films

Koumoto, K; Saito, N; Gao, YF; Masuda, Y; Zhu, PX

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN Vol. 81 ( 11 ) page： 1337 - 1376 2008.11

Surface characterization on binary nano/micro-domain composed of alkyl- and amino-terminated self-assembled monolayer

Lee S.H., Ishizaki T., Saito N., Takai O.

Applied Surface Science Vol. 254 ( 22 ) page： 7453 - 7458 2008.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Surface Science

The binary alkyl- and amino-terminated self-assembled monolayers (SAMs) composed of nano/micro-sized domains was prepared though a self-assembly technique. In addition, the wetting and electrostatic property of the binary SAMs was investigated by the analysis of the static and dynamic water contact angle and zeta-potentials measurement. The binary SAMs were also characterized by atomic force microscope (AFM), Kelvin probe force microscope (KPFM) and X-ray photoelectron spectroscopy (XPS). The domains on the binary SAMs were observed in topographic and surface potential images. The height of domain and the surface potential between octadecyltrichlorosilanes (OTS)-domain and n-(6-aminohexl)aminopropyl-trimethoxysilane (AHAPS)-SAM were about 1.1 nm and -30 mV. These differences of height and surface potential correspond to the ones between OTS and AHAPS. In XPS N 1s spectra, we confirmed the formation of binary SAMs by an amino peak observed at 399.15 eV. The dynamic and the static water contact angles indicated that the wetting property of the binary SAMs was depended on the OTS domain size. In addition, static water contact angles were measured under the conditions of different pH water and zeta-potential also indicated that the electrostatic property of the binary SAMs depended on OTS domain size. Thus, these results showed that the wetting and electrostatic property on the binary SAMs could be regulated by controlling the domain size. © 2008.

DOI： 10.1016/j.apsusc.2008.06.001

Control of site-selective adsorption reaction on a biomimetic super-hydrophilic/super-hydrophobic micropatterned template

Ishizaki T., Sakurai H., Saito N., Takai O.

Surface and Coatings Technology Vol. 202 ( 22-23 ) page： 5535 - 5538 2008.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Surface and Coatings Technology

A biomimetic super-hydrophobic/super-hydrophilic micropatterned template was successfully fabricated by microwave plasma-enhanced chemical vapor deposition (MPECVD) and vacuum ultraviolet (VUV) lithography. Water drops were selectively condensed on super-hydrophilic regions of the template. In the solution of pH 2.6, carboxyl-terminated fluorescent polystyrene spheres were sedimented on super-hydrophobic regions due to electrostatic attractive forces between negative -COO- and positive -CH3 groups. Cu was also deposited densely on only super-hydrophobic regions through electroless plating. From these results, we revealed that the biomimetic super-hydrophobic/super-hydrophilic micropatterned template was used as site-selective chemical reaction field. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2008.06.124

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