Kunihito Tanaka

The aqueous extract of the leaves of Odontonema strictum (OSM) is used in folk medicine for its antihypertensive properties, and it contains a wide range of secondary metabolites, mostly polyphenols such as verbascoside and isoverbascoside, which could play a major role in the preparation of silver nanoparticles. In this study, we aimed to prepare AgNPs for the first time using the OSM leaf extract (OSM-AgNPs) to investigate their free radical-scavenging potency against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2). Dynamic light scattering (DLS), UV/Vis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS) were used to characterize the OSM-AgNPs. With a size around 100 nm and a ζ-potential of −41.1 mV, OSM-AgNPs showed a good stability and a better colloidal property due to electrostatic repulsion and the dispersity. The strong absorption peak at 3 keV in the EDX spectra indicated that silver was the major constituent. Additionally, the existence of silver atoms was confirmed by the Ag 3d5/2 peak around 367 eV in the XPS spectra. IC50 values of 116 μg/mL and 4.4 μg/mL were obtained for the scavenging activities of DPPH and H2O2, respectively. The synthetic OSM-AgNPs can be further exploited as potential antioxidant agents.

<title>Abstract</title>The atmospheric pressure low-temperature homogeneous discharge using helium and nitrogen, both known for industrial applications, was reviewed. In case of helium, metastable atoms (2¹s and 2³s) produced in the glow discharge were able to dissociate mixed molecular gases to produce radicals or atoms. Radical species undergo chemical reactions, such as oxidation or nitration reaction and form products on the electrode surfaces. Applications of helium atmospheric pressure glow discharge including surface treatment of plastic films to enhance adhesibility with glue, weakening strength with pressure-sensitive glue, and deposition of solid material on a flat plate or powder surfaces, were described. Moreover, the microwave low-temperature discharge using nitrogen, as a cost-saving carrier gas, were introduced for the surface cleaning of silicon wafer.

During the past decade, we have examined the surface improvement of PVF, FEP, PFA, and PTFE films by APGD system. Their adhesive strength with an epoxy resin could be improved that attained by different kind gas introduction to the plasma system. Last year, new idea using NH4/H2O as the treating gas was proposed in the low pressure glow discharge (LPD) to treat PTFE by T. Yajima et al. So we examined the surface effects in both process, APGD and LPD, using NH4/H2O mixture. APGD treatment could not have any chemical effect on the PTFE surface. On the other hand, LPD, we got the proof of super hydrophilicity on the PTFE. It seemed that in the low pressure, a slow sputtering will be a preceding reaction on the PTFE even used the NH4/H2O. The difference of the kinetics was considered in the evaluation of both processes, APGD and LPD.

B2H6/He plasma and B2H6/H-2/He plasma treatments of PTFE were performed. Concentration of the B2H6 was varied through this experiment. Then defluorination degree and adhesive strength were measured. While B2H6 and hydrogen were effective for defluorination of PTFE surface, oxygen functional groups generated by post-oxidation improved adhesive strength. The atmospheric pressure glow plasma treatment with lower diborane concentration more modifies PTFE surface.

Polytetrafluoroethylene (PTFE) sheet surface was treated by the diborane/H-2/He plasma for the deflurination to improve the adhesive strength. Diborane was generated by the H-2/He plasma treatment of a boron plate and was transported to the plasma zone for PTFE sheet treatment. And then, the defluorination plasma treatment with this diborane/H-2/He mixture gas performed PTFE sheet. Fluorine atom content of treated PTFE surface was decreased to about twentieth of that of untreated PTFE. The adhesive strength between treated PTFE and epoxy glue became stronger enough for practical use.

The relationship between the plasma conditions and the atmospheric pressure glow plasma deposition characteristics of the polyhexafluoropropene film, such as the film configuration, the deposition rate and products in plasma, was investigated. The higher deposition rate and the higher monomer use efficiency were obtained at a lower hexafluoropropene (monomer) concentration and a lower total gas flow rate (longer residence time in the plasma region). However, an extreme long residence time generated some granular deposits. And five gas phase products were detected by gas phase analysis. We considered that C(2)F(4) and C(4)H(8), which have double bond, were related to the deposition deeply. (C) 2009 Elsevier B.V. All rights reserved.

Polytetrafluoroethylene (PTFE) sheets were treated by the diborane/H2/He plasma for the deflurination to improve the painting performance and the adhesive strength with an epoxy glue. Diborane was generated by the H2/He plasma treatment of a boron plate. And then, the defluorination plasma treatment with this diborane/H2/He mixture gas performed to PTFE sheet. Fluorine atom content of treated PTFE surface was decreased to about one hundredth of that of untreated PTFE. The water contact angle of treated PTFE was also decreased from 120° to 50°. A paint coated on treated PTFE adhered to its surface strongly.

Polytetrafluoroethylene (PTFE) sheet surface was treated by the diborane/H-2/He plasma for the deflurination to improve the painting performance. Diborane was generated by the H-2/He plasma treatment of a boron plate. And then, the defluorination plasma treatment with this diborane/H2/He mixture gas performed to PTFE sheet. Fluorine atom content of treated PTFE surface was decreased to about one hundredth of that of untreated PTFE. The water contact angle of treated PTFE was also decreased from 120 degrees to 50 degrees. A paint coated on treated PTFE adhered to its surface strongly.

Water insoluble polyethylene glycol (PEG) films as a core-shell of polymer powder were fabricated by the combination techniques of adsorption of PEG on the powder surfaces and atmospheric glow discharge(APGD) irradiation to the surface to take cross linking reaction of the adsorbed PEG. PEG 2000 was used as the precursor of the core-shell films. The obtained films on the powder surfaces were investigated by XPS,ATR-FTIR and wettability measurement using the capillary raise method.

SiO2 films were deposited using both atmospheric glow plasma chemical deposition (APG-CVD) and spin coating as hard coating agents for their abrasion resistance. Tetracthoxysilane (TEOS) was used as the precursor. We formed films by spin coating on surfaces over APG-CVD as adhesive interlayer, and were able to achieve a hard deposited film without any cracks.

We synthesized silica nano powder using ICP plasma and evaluated its adsorption ability for biotic substances such as proteins and molecular histamine. The silica particles with negative electric charge adsorbed cytochrome C and histamine which have a positive electric charge. On the other hand, OVA which has a negative electric charge was not adsorbed. We considered that electrostatic interactions dominate the adsorption process between silica particles and biotic substances.

Plasma-polymerized hexafluoropropene (PPHFP) film had adhesive strength that was low enough for use as a release coating, but a small amount of PPHFP peeled off from a poly(ethylene terephthalate) (PET) film substrate. The insertion of a soft and elastic polymer, polyethylene glycol, between the two layers prevented the PPHFP peeling off from PET. The results also showed that the polymerization degree of PPHFP was low. (c) 2006 Elsevier B.V All rights reserved.

Combined surface treatments using plasma fluorination and surface roughening were applied to investigate whether they could increase the peel property of PET beyond the value needed for use as a release coating of pressure-sensitive adhesive tapes. The peel strength of PET treated with CF4/He APG plasmas decreased to approximately 100 N . m(-1), but not quite to the ideal value of PTFE, 20 N . m(-1). We also prepared PET with a rough surface (matte PET) to examine the effect of surface roughening. The matte PET peel strengths were decreased by plasma fluorination; the roughest matte PET showed even lower peel strength than PTFE. We conclude that the combined treatments could be effective in the formation of a surface with high peel property on PET.

Fe oxide-coated TiO2 particles for UV protection cosmetics were produced by means of atmospheric pressure glow discharge using IAA(Iron acethyl acetonato). The particles were also coated by a silica protection layer. To examine the UV catalytic ability of Fe oxide-coated TiO2, we measured a squalene that contained the powders by GCMS for the gas products after the squalene had been irradiated by a Xe lamp for one hour. Using silica-coated TiO2 that was coated by Fe oxide, we find almost no signals from any harmful organic oxides in the GC-MS spectra of the UV irradiated squalene.The multi- coated powder shows very fine and flesh like-color with pearl-like glowing. © 2007, The Institute of Electrical Engineers of Japan. All rights reserved.

Toluene decomposition is examined using a corona discharge, a UV lamp, and a TiO2 catalyst complex system. The toluene decomposition reaction occurs only with OH and O (D-1) radical. High decomposition rations are obtained: 98% for the toluene/H2O/O-2-corona/UV system and 70% for the toluene/H2O/air-corona/UV systems. Moreover, if the TiO2 catalyst is combined with the corona-UV system for 1 000 ppm of toluene, this value increases to 78% (0.31 Wh.m(-3).ppm(-1)), which is higher than that obtained in a normal corona discharge system.

PLGA microcapsule developed as a drug delivery system (slow release speed of medicines) material has, however, a problem, that is the initial burst release of medicine because of water penetrating into the PLGA capsules. To prevent water penetration, the fluorinated layer fort-nation on the PLGA surface by atmospheric pressure glow plasma was examined. We tried to use CF4/He plasma and C3F6/He plasma treatments for the formation. The C3F6/He plasma 7 times treated ones showed the worse initial burst release because this treatment destroyed the PLGA capsules by its excessive treatment time. On the contrary, since the C3F6/He plasma 5 times treatment could make the PLGA capsule surface enough hydrophobic, they had no initial burst release and the slow release speed. (c) 2005 Elsevier B.V. All rights reserved.

Dispersed PE powder was carried into an RF-APG-plasma zone by gas flow. and was treated; treatment time was about 30 ms. Plasma-treated PE powder was gathered by a filter. then measured by chemical derivatization techniques using XPS. Oxidized PE powder showed enough hydrophilicity to disperse in water completely even though the treatment time was quite short. The degree of oxidization could be controlled by changing discharge power and oxygen gas content. Though PE powder was not nitrided enough by NNH3/He plasma under any plasma conditions. it was found that nitriding was promoted by increasing, the number of treatments.

Plasma-polymerized hexafluoropropene (PPHFP) film deposited using a dielectric barrier discharge reactor at atmospheric pressure had low enough adhesive strength, 22.2 Nm(-1), for use as a release coating of pressure-sensitive adhesive tapes, but the bond strength between PPHFP film and a poly (ethylene terephthalate) (PET) substrate film was slightly weak: some part of the PPHFP deposits could be peeled from the PET substrate. Since the XPS results indicated that the bond strength between plasmapolymerized ethylene (PPE) film and PET substrate was strong enough, we tried to deposit PPE and plasma-polymerized ethylene - hexafluoropropene gradient plasmacopolymer between the PET substrate and the PPHFP film. This multi-layer film (MLF) had low enough adhesive strength, 36.6 Nm(-1), for use as the release coating; this value was near that of a control sample, Teflon sheet, 21.6 Nm(-1). Moreover, the bond strength between MLF and PET substrate became stronger than that between PPHFP and PET films.

Poly(tetrafluoroethylene-co-perfluoro [alkyl vinyl ether]) (PFA) and polytetrafluoroethylene (PTFE) films were treated by three kinds of atmospheric pressure glow plasmas: an untreated sample was treated by He plasma or trimethoxyborane (TMB)/H2/He plasma, and a TMB-absorbed sample was treated by H2/He plasma. TMB was a new reactant for the treatment, to increase the films' adhesive strength with an epoxy glue. These films were also treated by a wet method using a sodium solution (Tetra-Etch compound) and such films were used as the control samples. The peel strength values of the controls of PFA and PTFE were 3.5 and 9.5Ncm-1, respectively. The adhesive strengths of all plasma-treated PFAs were stronger than those of untreated one. Especially, the peel strength of the TMB/H2/He plasma-treated PFA showed the maximum value of 4.5Ncm-1, which was bigger than that of the control one. The adhesive strength of the TMB/H 2/He plasma-treated PTFE films also showed the maximum peel strength, 7.9Ncm-1, but this value did not exceed that of the control PTFE. Such results suggested that the TMB/H2/He plasma had the advantage of providing better adhesive improvement of those polymers, especially PFA than the wet method could provide. The results of XPS and SEM indicated that TMB actively removed fluorine atoms from the polymer surface. Therefore, boron compounds are effective for the improvement of the adhesive strength between the fluorinated polymer and the epoxy glue. © 2003 Elsevier Ltd. All rights reserved.

We examined a method for coating zirconia on flat amorphous Co70.3Fe4.7Si10B15 powder (fa-Co) by atmospheric pressure glow plasma with Zr(OC4H9)(4). XPS analysis was performed to determine the existence of ZrO2 on the surface of the treated powder. The fa-Co obtained strong resistance to oxidization by this zirconia coating method. Resistivity measurements revealed that fa-Co coated with ZrO2 was insulating. We also improved the permeability as a function of frequency of composite cores made from fa-Co by this zirconia-coating method. (C) 2001 Elsevier Science B.V. All rights reserved.

Atmospheric pressure glow (APG) plasma treatment does not require a vacuum pump that is equipped with a low pressure plasma device. With treatment for organic powder, APG plasma can modify the surface roughness and wettability. In this study, we treated polystyrene films and powder by APG plasma, surveyed the changes of surface morphology, and examined the antifoaming effects of powders. A high exposure time (for this study, 20 min) in He + CF4 plasma, polystyrene powders were introduced onto approximately 55% of fluorine atoms. This powder gave a better result for antifoaming properties. (C) 2001 Elsevier Science B.V. All rights reserved.

We tried to treat poly (vinyl fluoride) (PVF), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) and poly(tetrafluoroethylenei-o-perfluoro [alkyl vinyl ether]) (PFA) films by atmospheric pressure glow plasma to increase their adhesive strength with an epoxy resin. Their adhesive strength could be improved; the maximum peel force values obtained from a 180 degrees peel test were over 2.00, 0.90 and 0.62kgf 20 mm(-1), respectively. These values were near or higher than those of the control sample films treated by a surfactant: 1.06, 0.47 and 0.70kgf 20 mm(-1), respectively. In this study, we found that the O-2/He plasma-treated films had the highest peel forces although their contact angles were highest and their amounts of incorporated oxygen or nitrogen atoms were least; He plasma treatment also showed better effects on the overall results. (C) 2001 Elsevier Science B.V. All rights reserved.

The NH3, O-3 and NOx reduction from NH3/air and NOx/air systems were studied in a corona discharge tube. In the negative corona discharge, the NH3 was decomposed and NOx, NO, O-3 production was suppressed even in air. The NOx reduction reaction in corona discharge was explained by an enhancing of electron impact dissociation in a low field strength discharge. (C) 2001 Elsevier Science B.V. All rights reserved.

We examined the ashing treatment at atmospheric pressure by means of three spray-type reactors fed with O2/He or O2/Ar mixture gases. These differed in the size or the shape of their nozzles. Such reactors were able to ash an organic compound (OFPR-800 a photoresist) even at atmospheric pressure. The results showed that the following procedures are important for increasing the ashing rate: to make the gas speed after blowing out fast to decrease the O2 content while increasing the gas speed and to use a gas mixture which has a slow decay rate of the active species, such as the oxygen radicals. Especially, when we used O2/Ar mixture gas for the ashing treatment, the ashing rate became quite fast and was as fast as that of a general low pressure glow plasma.

We examined silica coating methods on Fe3O4 (black), FeOOH (yellow) and Lithol Rubine BCA (RED) powders by means of atmospheric pressure glow plasma CVD with tetraethoxysilane. These pigments were deteriorated easily by heating or oxidation. However, cooling the discharge tube and depositing protective films on the pigments before plasma oxidation could prevent the deterioration. We developed three ways to make protective films, which suited each pigment's characteristics. (C) 1998 Elsevier Science S.A.

We investigated the mechanism and application of photoresist ashing by means of atmospheric pressure glow (APG) plasma. APG plasma using a mixture gas of He and O2 could ash the photoresist with a rate of about 1 μm·min-1, which was roughly the same value as that of O2 plasma ashing at a low pressure. The dependences of etch-rate on O2 gas flow rate, discharge power and substrate temperature suggested that the APG plasma ashing process was mainly the oxidation of the photoresist by oxygen radicals. The XPS and optical emission spectroscopy suggested that excited helium promoted the desorption of oxides on the surface of the photoresist. To reduce cost, we tried to use Ar, acetone (Ac) and O2 mixture gas instead of He and O2 mixture gas. Ar/Ac/O2 plasma could etch the photoresist as fast as He / O2 plasma, although the O2 content was one sixth of that of He/O2 plasma. Minute area ashing using a spray type discharge tube was also investigated. Its ashing rate was the fastest, about 4.0 μm·min-1, when Ar/O2 mixture gas was used. ©1997TAPJ.