A low temperature synthesis of carbon nanofibers was demonstrated by a plasma-enhanced chemical vapor deposition (PECVD). A low temperature CO/Ar DC plasma was used in this study. Carbon films deposited on glass substrate during PECVD were characterized by scanning electron microscopy and Raman spectroscopy. The effect of discharge current and substrate location on the CNFs formation has been investigated. The results show that vertically aligned carbon nanofibers can be synthesized at even room temperature with optimum discharge conditions when the substrate is placed on the cathode.

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The present study demonstrates a novel preparation method for water-soluble carbon nanotubes (CNTs) using microplasma generated in water suspension of CNTs. The microplasma was achieved by generating pulsed streamer discharges, which were triggered by applying multiple square high voltage pulses to a wire-to-plane electrode system immersed in the CNT suspension. The CNTs treated by the microplasma were solubilized and homogeneously dispersed in water for a month or longer. The functional group of -OH seemed to be bound to the CNT surface and responsible for the solubilization effect. The -OH group might be formed by chemical reactions between O and H radicals, which were detected by optical emission spectroscopy of the microplasma. The proposed method does not need any particular chemical agents or additives for solubilization. Of particular importance is its simplicity and time-efficiency in contrast to the usual time-consuming chemical treatments developed thus far. It was demonstrated that bio-nano interfaces between the water-soluble CNTs and biological cells could be readily fabricated by simultaneous electrokinetic manipulation of them in water using dielectrophoresis (DEP). The DEP trapped CNTs could serve as a NO2 gas sensor, showing that the surface adsorption of gas molecules on the CNTs did not deteriorate by the microplasma treatment.

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Recently, to meet the demands of emerging industries, such as magnetic storage devices and micro electro mechanical systems (MEMS), diamond-like carbon (DLC) coatings have been required to be ultra-thin and sufficiently durable. The present study employed frictional force microscopy (FFM) to measure the coefficient of friction (COF) of ultra-thin DLC films, and thus, characterize their mechanical durability. FFM revealed that the COF of DLC films prepared by filtered cathodic vacuum arc (FCVA) increased with decreasing thickness. To explain the above tribological behavior, several mechanisms were discussed. The indications are that an increase in contact area plays an important role in the increase of COF of ultra-thin DLC films.

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In this study, we examined the partial reduction of anatase TiO2, both without form transformation from anatase to rutile and without transformation to Ti2O3, using hydrogen plasma. In this experiment, RF discharge plasma (13.56 MHz) was used, and the plasma was generated by a discharge between electrodes attached on the outer surface of a quartz tube. The reduced TiO2 was analyzed by XRD. Consequently, it was shown that, under the proper conditions, hydrogen plasma can partially reduce anatase TiO2 at temperatures lower than 800°C, both without form transformation from anatase to rutile and without transformation to Ti2O3.

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Microplasmas offer the advantage of small size, low power consumption as well as higher rate of materials processing and are therefore promising for new applications in materials processing. While many different types of microplasma devices have been presented in recent years, the effects of the smaller scale on the properties of the plasma (gas and electron temperatures), distribution of electrons, radicals and ions, and the implications of these characteristics for materials processing have not been studied in detail yet. Here we present the generation and characterization by optical emission spectroscopy (OES) as well as the numerical simulation of atmospheric pressure argon microplasmas inside capillaries with inner diameters between 50 micro m and 1 mm using two different types of thennoelectron enhanced microplasma (TEMP) devices. The first type has a freestanding geometry whereas the second type is planar, fabricated by a surface mount technique. The latter allows for future size reduction of the microplasma setup and for an easier integration with other apparatuses and devices.

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In order to understand the plasma cutting process for improving the reliability for stable cutting with a prolonged lifetime, the whole region of oxygen plasma jet, namely, a hafnium electrode as a cathode buried in the water-cooled copper sheath, an arc plasma and a copper nozzle as an anode is treated in a unified numerical model. Calculations are made for the two-dimensional distributions of temperature and fluid flow velocity in the whole region of the oxygen plasma jet for a 400 A in arc current. The current density distribution and also the whole energy balance at the tip of cathode and water-cooled copper sheath are predicted. It is shown that the nozzle diameter strongly affects the plasma jet properties and also the nozzle lifetime but weakly affects the hafnium cathode lifetime.

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A plasma torch can stabilize high temperature arc plasma by employing shielding gas and has high heating efficiency and highly controllable characteristics. Therefore, it is widely utilized as a heat source device, for example, for production of nano-particles, material processing, or treatment of toxic waste and so on. Tube Cathode Arc (TCA) is a kind of plasma torch which produces the arc plasma by introducing the shielding gas from the hole of the tube cathode. It has been studied as a heat source especially in lower pressure environment, for example, for space welding or plasma CVD. For an application in atmospheric pressure, it enables heating of materials uniformly and, therefore, to be suitable for processes such as thermal spraying, brazing or buildup. In this paper, as basic energy source properties of argon TCA, dependence of the arc plasma property on cathode shapes such as diameter and conical angle of the cathode are numerically analyzed.

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In order to make clear the physical grounds for anode fall in atmospheric free-burning argon arc, the results of the experimental measurements of anode fall with Langmuir-probe method for various arc currents and gas flow rates are presented. In the case of low arc current, the anode fall is positive. The electron temperature and space potential rise on approaching the anode surface within 0.1 mm from the anode for low gas flow rate. In the case of high arc current, the anode fall is negative. Furthermore, the electron temperature and the space potential hardly depend on the distance from the anode and are not influenced by gas flow rate.

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In this paper, we review our recent works on the preparations of some Au electrodes modified with self-assembled monolayers of functional metal complexes. such as molecular recognition, electron transfer, bacteria immobilization, and dioxygen activation, from the viewpoint of the construction of chemical/energetic conversion devices. (i) A new-classed promoter electrode bearing optically-active CoIII complexes containing (S)-/(R)-phenylalaninc derivative ligands as the molecular recognition site has been constructed: the chirality and/or orientation of promoter on Au electrode surface have affected the electron transfer rate of cytochrome c. (ii) The FelII-artificial siderophore-modified Au electrode surface has been prepared as an immobilizing tool of microorganisms toward the bacteria sensor and bio-reactor, whose adsorption ability for microorganisms has been studied. (iii) For a purpose of fixation and activation of dioxygen at room temperature, the self-assembled monolayer of dinuclear iron complex has been modified on Au electrode, and its reaction with dioxygen has been studied.

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Biointerface composed of bimolecules with pH response, bioaffinity and protein immobilization functionalities using synthesized surface initiator coated on magnetic nanoparticles surface was successfully prepared by atom transfer radical polymerization (ATRP) in methanol at ambient temperature. The pH response polymer brush with 2-(diethylamino)ethyl methacrylate (DEA)-grafted magnetic nanoparticles can be dispersed in below pKa 7.3 aqueous solution due to protonation overcome magnetic interaction. On the other hand, polymer and block copolymer with bioaffinity and proteine immobilization functionalities based on 2-methacryloyloxyethyl phosphorylcholine (MPC)-grafted nanoparticles can be dispersed in neutral aqueous solution in spite of having a neutral charge. It is considered that steric repulsion of surface polymer brush has influenced the dispersibility. In the case of block copolymer composed of bioaffinity and protein immobilization functionalities, when the rate of immobilization of bovine serum albumin (BSA) was estimated, it turned out that the original protein immobilization part of surface polymer was exchanged for BSA. It is concluded that biointerface with various functionalities can be prepared by ATRP method to be useful for such as bioaffinity beads construction.

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We propose the non-label and invasive analysis method for drug transport using an oocyte-based field effect device, which is based on potentiometric detection of extracellular potential change derived from exchange of molecular charges at cell membrane/gate insulator. The extracellular potential change at cell membrane/gate insulator can be directly transduced into electrical signal such as threshold voltage changes using the oocyte-based FET. The time course of threshold voltage change can be monitored during the uptake of common substrate through the transporter at the cell membrane without any labeling materials. The platform based on the oocyte-based FET is suitable for a simple and convenient system for drug screening in pharmaceutical lead discovery.

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The hydroxamate-typed artificial siderophore, tris[2-{3-(N-acetyl-N-hydroxamino)propylamido}propyl]aminomethane (TAPPA) was prepared and its FeIII complex, FeIII-TAPPA was modified on Au electrode surface. FeIII-TAPPA indicated biological activity for Microbacterium flavescens, which is hydroxamate-typed siderophore auxotrophic gram-positive microorganism, suggesting that FeIII-TAPPA was able to permeate the cell membrane of microorganism. The modification of Fem-siderophore complex was carried out by stepwise self-assembling method. The cyclic voltammetry of the resultant Au electrode, FeIII-TAPPA/Au confirmed the surface modification of Fem-TAPPA. The adsorption experiments of M. flavescens with FeIII-TAPPA/Au were clearly showed that FIII-TAPPA/Au could immobilize microorganisms. The images of the adsorption of M flavescens were obtained by various microscopic methods. Quart crystal microbalance (QCM) measurements also suggested that FeIII-TAPPA/Au was able to adsorb M. flavescens. The adsorption ability is due to the interaction between FeIII-TAPPA on a Au electrode and receptor/binding protein in the cell membrane.

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Ordered surface patterning of biocompatible microdomain is potentially needed in many applications such as high sensitive biochips, biosensors, and nanobio devices for cell culturing. One of the efficient ways in the fabrication of patterned surface is using the microphase separation of well-defined block copolymers by controlling molecular weight and film formation process. Thus we synthesize several compositions of block copolymers containing 2-methacryloyloxyethyl phosphorylcholine (MPC) which is hydrophilic and shows excellent biocompatibility, and polydimethylsiloxane (PDMS) which has hydrophobic nature and usually used as soft lithography materials. All of the copolymers were synthesized by the atom transfer radical polymerization (ATRP) method at room temperature. The kinetics plot and molecular weight plot shows that the polymerizations of block copolymers were well controlled, thus the compositions of block copolymers were controllable. Two kinds of synthesized copolymers: the longest MPC segment and the shortest one, were cast on Si(100) substrate by spin casting or solvent casting. By using the IR-multichannel viewer and atom force microscope, we could conclude that the film formed by the longest MPC segment could not generate the well defined surface structure due to its long chain aggregation. By using the copolymer containing the shortest MPC segment, we could generate a nanoscale ordered surface patterning of phorsphorylcholine unit.

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Development of the biointerface for high performance immuno-sensing methods is one of the current research topics in analytical chemistry and biochemistry. We developed histidine-tagged protein A (His6-protein A)/poly(ethylene glycol) (PEG) co-immobilized gold surface as a new class of immuno-sensor chip, where both protein A and PEG are directly immobilized on the surface by the histidine-tag and the thiol group, respectively. In this study, the resulting surface was applied to sandwich assay for specific protein detection based on surface plasmon resonance measurements. Despite the similar content of immobilized antibodies, the amount of secondary antibody on His6-protein A/PEG surface was about eight times higher than that of physically adsorbed antibody/PEG surface. In addition, nonspecific protein absorption was extremely suppressed on His6-protein A/PEG surface, compared with Ni2+ -nitrilotriacetic acid (NTA) surface, which was generally used for the immobilization of histidine-tagged proteins. These results clearly indicate that effective orientation of the immobilized antibody with the prevention of non-specific adsorption was achieved on the His6-protein A/PEG surface.

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Diiron(II) complex with a new dinucleating ligand containing terminal amino group, 2,6-bis[bis(6-pivalamido-2-pyridylmethyl)aminomethyl]-4-aminophenol (tppap) (1), [Fe2(tppap)(C6H5COO)2]+ (2), was synthesized. The self-assembled monolayer (SAM) of 2, 2/Au, was prepared by the coupling reaction between 2 and activated ester-modified Au electrode. The redox behavior of 2/Au was observed in aqueous solution at room temperature, which suggests that 2 on Au surface has been stabilized as compared with 2 in homogeneous solution. In addition, the redox potentials of 2/Au assignable to Fe2(II,II)/(III,III) and Fe2(II,III/III,III) shifted to negative direction by bubbling of molecular dioxygen, which returned to the original potential by Ar bubbling. These behaviors were reversible, suggesting that 2/Au can reversibly bind/release molecular dioxygen in aqueous solution at room temperature.

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The purpose of this study is obtaining both biocompatibility and lubricity to biomaterial surfaces. For this purpose, we investigated the effects of a graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) onto polypropylene (PP) surface. The MPC graft nanolayer was prepared using a photo-induced graft polymerization. The poly(MPC)-grafted (PMPC-g-PP) surface was characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and static and dynamic water contact angle measurements. As a result, the PMPC grafting clearly increased hydrophilicity and surface mobility. Friction coefficient was measured in air and in water. The friction coefficient of the PMPC surface was 0.019 in water, which was 1/10 compared with air condition. This value is similar to that of the human joints. After the friction test in water, the surface was observed with scanning electron spectroscopy. No flaw was observed on the PMPC surface. It was considered that the PMPC surface showed the behavior of hydrodynamic lubrication in water. Friction test was also performed under biological conditions; in phosphate buffered saline (PBS), PBS containing a bovine serum albumin, and cell culture medium containing fetal bovine serum. The results indicated that the PMPC surface kept highly lubricity under biological conditions.

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We prepared the mixed monolayer-modified Au electrode composed of negatively charged CoIII complex (1) and hydroxyl-terminated alkanethiols (Cn; n = 2, 6), 1/Cn-Au, using the ‘step-by-step’ immobilization method; the low-density monolayer of 1 (1-Au) was firstly constructed with a spacing and then Cn molecules were filled in the gap of 1. In the cyclic voltammetric measurement of horse heart cytochrome c (cyt c) using 1/C2-Au, only a pair of oxidation-reduction wave was observed with almost the same peak separation as the case of 1-Au. Since the electron transfer rate by using the single monolayer of C2 was much faster than that of 1-Au, it clearly indicates that the modification of C2 does not cause the phase-separation and C2 molecules on Au do not influence to the electron transfer reaction with cyt c. In contrast, 1/C6-Au showed faster electron transfer rate than the cases of 1-Au and 1/C2-Au, but exhibited slower rate than that of single monolayer of C6. These findings indicate that cyt c firstly interacts with negatively charged 1, and then electron transfer reaction proceeds via C6 molecules on Au electrode.

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To develop a highly sensitive immunoassay, both enhancement of specific signals and reduction of nonspecific signals should be achieved. In this study, we investigated a novel biointerface for highly sensitive immunoassays by integrating a phospholipid polymer with a nanoscale surface modification process known as the electrospray deposition (ESD) method. The surface prepared by ESD has a nanosphere-shaped polymer structure and therefore the specific signals from analytes in the enzyme immunoassay were significantly enhanced due to an increase in the surface area. The sprayed phospholipid polymer prevented nonspecific protein adsorption effectively lowering the nonspecific signals which cause the high background or noise level. Furthermore, the phospholipid polymer has active ester groups for conjugation of antibodies, and the stability of the antibodies conjugated to the polymer surface was improved drastically. The nanosphere-shaped phospholipid polymer surface can be used to yield a highly sensitive, stable, and reliable assay.

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In order to obtain the structural information around the active site of three c-type cytochromes (cyt c from horse heart, cyt c2 from Rhodospirillum rubrum, and cyt c553 from Alcaligenes xylosoxidans GIFU 1051) in aqueous solution, we studied their redox behaviors by use of the densely packed monolayer of the (S)-phenylalanine-containing CorIII complex. In the case of cyt c, no redox wave was observed, which agrees with the previous report· that the heme is buried inside of the protein. In contrast, the redox wave of cyt c2 was clearly observed, which coincides with the fact that the heme positions at the protein surface. Interestingly, in the cyclic voltammogram of cyt c2, a splitting of the wave was detected, which was elucidated to be attributable to the protonation/deprotonation of His42 imidazole of the protein. Cyt c553, of which the structural information has still not been revealed, gave the redox wave without splitting. In the light of the results of cyt c and cyt c2, this redox behavior indicates the existence of two structural characteristics for cyt c553: (i) the heme is probably located near the protein surface, and (ii) there is no conformational change caused by the protonation.

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To investigate the tissue adhesive function of a hydrogel composed of biocompatible amphiphilic polymers, random and graft polymers were prepared from 2-methacryloyloxyethyl phosphorylcholine (MPC), electrolyte monomers and hydrophobic n-butyl methacrylate (BMA). The results of the fluorescence study suggested enhanced electrostatic interaction in the graft polymers compared to the random polymers. This is due to the strategically designed architectures and the hydrophobic BMA units. The results of the cytotoxicity test showed that the cytotoxicity of the MPC polymers was lower than that of glutaraldehyde, which is a crosslinking agent in the aldehyde-type tissue adhesives and is known to cause serious side effects. The cationic MPC polymers demonstrated higher cytotoxicity compared to the anionic ones, which demonstrated no significant cytotoxicity. The tissue adhesion of the PlC hydrogels was lower than that of a commercially available fibrin glue. However, the tissue adhesive strength increased with an increase in the polymer concentration and could be controlled by the water content of the hydrogel. In addition, balance of the electrolyte units for the PIC formation and the tissue adhesion is crucial for expression of adhesion. Although further investigation of the biocompatibility is required, it can be concluded that the PlC hydrogels formed by the amphiphilic MPC polymers can be a promising tissue adhesive which demonstrate tissue adhesion and biocompatibility according to the architectures and chemical structures.

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To construct polymer hydrogel microstructure containing biomolecules as a biosensor in microfluidic devices by a conventional photoirradiation, new photocrosslinkable polymers composed of 4-(4methoxycinnamoyl)phenyl methacrylate and 2-methacryloyloxyethyl phosphorylcholine (PMMC) was synthesized. The polymers were used as prepolymers to make hydrogels by photoirradiation. Moreover, PMMC gel exhibited excellent performance of protein adsorption resistance compared with Poly(vinyl alcohol)-N-methyl-4(4'-formylstyryl) pyridinium methosulfate acetal (PVA-SbQ), and succeeded in the immobilizing of enzyme. In the future, the immobilized enzyme will be checked in detail for application of PMMC to a biosensor. PMMC is thought to be increasing the permeability of the biomolecules to the inside of the gel compared with PVA-SbQ which is the material commonly used in the current researches. From the results so far, it is expected that PMMC can be used for simple fabrication of enzyme immobilizing membranes for highly sensitive biosensors.

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