Faculty Profiles - SAITO, Nagahiro

Papers - SAITO, Nagahiro

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Quantitative spectrochemical analysis of solution plasma in aromatic molecules

Bratescu M.A., Kim K., Saito N.

Plasma Processes and Polymers Vol. 16 ( 7 ) 2019.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Plasma Processes and Polymers

A nonthermal plasma produced at atmospheric pressure in the gas resulted from the surrounding liquid is named solution plasma (SP). A quantitative and comparative spectrochemical analysis of the plasma gas and solution in benzene, pyridine, and aniline is performed. The number densities of dicarbon and cyano radicals and hydrogen molecule from the plasma gas are measured using a cheap, straightforward, and home-made optical set-up. By simply modifying the optical set-up, the molar concentration of newly formed chemical compounds is in situ obtained in the solution. The thermodynamic properties of aromatic molecules determine the electrical breakdown and the species number densities in the plasma gas. The production rate and atomic composition of carbon material are correlated with the radicals from plasma gas.

DOI： 10.1002/ppap.201900012

P-Type Doping of Graphene with Cationic Nitrogen

Chae S., Panomsuwan G., Bratescu M.A., Teshima K., Saito N.

ACS Applied Nano Materials Vol. 2 ( 3 ) page： 1350 - 1355 2019.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ACS Applied Nano Materials

Tailoring electrical properties of graphene by nitrogen doping is currently of great significance in a broad area of advanced applications. Bonding configuration of nitrogen atoms in graphene plays a vital role in controlling its electrical, chemical, and optical properties. Here, we report for the first time a simple bottom-up synthesis of a novel cationic nitrogen-doped graphene (CNG) by a solution plasma (SP). A mixture of ionic liquid and organic solvent was used as starting precursor. CNG exhibited an orthorhombic structure possibly due to the presence cationic nitrogen in hexagonal graphene lattice. Nitrogen doping content was found to be as high as 13.4 atom %. Electrical characterization demonstrated that the CNG exhibited a p-type semiconducting behavior with superior electrical conductivity and carrier concentration. Such unique electrical characteristics of CNG are mainly attributed to the presence of cationic nitrogen with preserved planar structure.

DOI： 10.1021/acsanm.8b02237

Production of reducing sugar from cassava starch waste (CSW) using solution plasma process (SPP)

Prasertsung I., Aroonraj K., Kamwilaisak K., Saito N., Damrongsakkul S.

Carbohydrate Polymers Vol. 205 page： 472 - 479 2019.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Carbohydrate Polymers

The cassava starch processing plays an important role in food industries. During starch processing stage, a large amount of cassava starch waste (CSW) which mainly contains lost starch product and solid residue such as cassava bagasse are produced. Starch and cassava bagasse can be hydrolyzed into fermentable sugar such as glucose. In the present study, the solution plasma process (SPP) is used to treat CSW to prepare reducing sugar. The investigated parameters are treatment time, solvent concentration, applied pulsed frequency, and CSW concentration. The %yield of total reducing sugar (TRS) and glucose were calculated by DNS method and glucose assay kit, respectively. The chemical structure, morphology, and crystal structure of plasma-treated CSW were investigated. The results showed that the %yield of TRS was greatly enhanced by SPP treatment compared to that of acid hydrolysis. The CSW powder completely broke down into pieces after SPP treatment was applied. The amorphous and crystalline regions of CSW were destroyed during SPP treatment. SPP treatment of CSW with light sulfuric acid concentration of 0.08 M, applied pulsed frequency of 30 kHz, and CSW concentration of 0.5%w/v provided 99.0% TRS and 47.9% glucose.

DOI： 10.1016/j.carbpol.2018.10.090

Enhanced degradation of methylene blue by a solution plasma process catalyzed by incidentally co-generated copper nanoparticles

Prasertsung I., Kaewcharoen S., Kunpinit K., Yaowarat W., Saito N., Phenrat T.

Water Science and Technology Vol. 79 ( 5 ) page： 967 - 974 2019

Language：English Publishing type：Research paper (scientific journal) Publisher：Water Science and Technology

This study presents a catalytic organic pollution treatment using the solution plasma process (SPP) with incidentally co-generated copper (Cu) nanoparticles via Cu electrode erosion. Methylene blue (MB) was used as a model organic contaminant. The treatment time was from 0 to 60 minutes at the plasma frequencies of 15 and 30 kHz. The treatment efficacy using the Cu electrode was compared with that of the tungsten (W) electrode. The high erosion-resistant W electrode provided no W nanoparticles, while the low erosion-resistant Cu electrode yielded incidental nanoparticles (10-20 nm), hypothesized to catalyze the MB degradation during the SPP. The percentage of MB degradation and the hydrogen peroxide (H2O2) generation were determined by an ultraviolet-visible spectrophotometer. The results showed that, after the SPP by the Cu electrode for 60 minutes, the MB was degraded up to 96%. Using the Cu electrode at a high plasma frequency strongly accelerated the Cu nanoparticle generation and MB treatment, although the amount of H2O2 generated during the SPP using the Cu electrode was less than that of the W electrode. The Cu nanoparticles were hypothesized to enhance MB degradation via both homogeneous (release of dissolved Cu ions) and heterogeneous (on the surface of the particles) catalytic processes.

DOI： 10.2166/wst.2019.035

Maximization of sodium storage capacity of pure carbon material used in sodium-ion batteries Reviewed International coauthorship

Kang J., Kim D.Y., Chae S.A., Saito N., Choi S.Y., Kim K.H.

Journal of Materials Chemistry A Vol. 7 ( 27 ) page： 16149 - 16160 2019

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Materials Chemistry A

Generally, carbon anode materials used in sodium-ion batteries do not exhibit good electrochemical performance because of low coulombic efficiency (CE). This paper presents a strategy to overcome this limitation by causing a co-intercalation reaction in a newly designed material. Here, Na was doped inside carbons and desodiation was caused by cleaning the doped Na. Consequently, the CE consistently exceeded 100%. Furthermore, new spaces were created when the doped Na was released continuously from the carbons, thereby allowing more Na to be stored in these spaces. This consistently increased the reversible capacity during cycling. Even though the designed material was a nanomaterial with a large specific surface area, the CE in the first cycle was 85%. Because of the co-intercalation reaction, a solid-electrolyte interphase (SEI) layer might not be formed depending on the anode surface structure and continuous long-term stable cycling was possible even without an SEI layer. Thus, a useful material for sodium-ion batteries can be designed using only carbons and without next-generation materials.

DOI： 10.1039/c9ta01751h

Solution plasma-assisted green synthesis of MnO <inf>2</inf> adsorbent and removal of cationic pollutant

Kim H., Saito N., Kim D.

Journal of Chemistry Vol. 2019 2019

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Chemistry

In this study, we proposed the solution plasma-(SP-) assisted green synthesis method using plants extracts, i.e., glucose, with the expectation of acting as a reducing agent and promotor for the formation of powder state of nanostructured MnO 2 . MnO 2 was simply and rapidly synthesized within 10 min by the SP-assisted method. The structural features and morphology of as-synthesized MnO 2 were characterized by XRD, Raman, FE-SEM, and TEM analyses. For potential application of as-synthesized MnO 2 , cationic dye, i.e., methylene blue (MB), removal performance was investigated by batch experiment at an initial concentration of C 0 = 100 mg L -1 . The obtained MnO 2 exhibited effective dye removal ability given high C 0 , and simultaneously applied plasma discharging further enhanced removal efficiency. These contributions therefore open a new window not only on a powerful and environmentally benign synthesis route for efficient adsorbents but also on supporting multiple removal mechanism.

DOI： 10.1155/2019/7494292

Cytotoxicity against cancer cells of chitosan oligosaccharides prepared from chitosan powder degraded by electrical discharge plasma

Chokradjaroen C., Theeramunkong S., Yui H., Saito N., Rujiravanit R.

Carbohydrate Polymers Vol. 201 page： 20 - 30 2018.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Carbohydrate Polymers

Chitosan oligosaccharides, which obtain from degradation of chitosan, possess some interesting molecular weight-dependent biological properties, especially anticancer activity. Therefore, the conversion of chitosan to chitosan oligosaccharides with specific molecular weight has been continuously investigated in order to find effective strategies that can achieve both economic feasibility and environmental concerns. In this study, a novel process was developed to heterogeneously degrade chitosan powder by highly active species generated by electrical discharge plasma in a dilute salt solution (0.02 M) without the addition of other chemicals. The degradation rate obtained from the proposed process was comparable to that obtained from some other methods with the addition of acids and oxidizing agents. Separation of the water-soluble degraded products containing chitosan oligosaccharides from the reaction solution was simply done by filtration. The obtained chitosan oligosaccharides were further evaluated for an influence of their molecular weights on cytotoxicity against cancer cells and the selectivity toward cancer and normal cells.

DOI： 10.1016/j.carbpol.2018.08.037

Mechanistic aspect based on the role of reactive oxidizing species (ROS) in macroscopic level on the glycerol photooxidation over defected and defected-free TiO<inf>2</inf>

Jedsukontorn T., Ueno T., Saito N., Hunsom M.

Journal of Photochemistry and Photobiology A: Chemistry Vol. 367 page： 270 - 281 2018.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Photochemistry and Photobiology A: Chemistry

The activity of commercial (defected-free) TiO2 and black (defected) TiO2 photocatalysts was comparatively tested in the glycerol photooxidation reaction. The preliminary results demonstrated that similar compounds, including glyceraldehyde (GCD), dihydroxyacetone (DHA), glycolic acid (GCOA), formaldehyde (FMD) and glycolaldehyde (GCAD), were generated from the photocatalytic oxidation of glycerol via both photocatalysts, but they differed in their yields. The black TiO2 exhibited a higher photocatalytic activity to convert glycerol than the commercial TiO2, due to the presence of some defective structure and its low band gap energy, and also promoted the generation of GCAD as the main product. In contrast, the commercial TiO2 promoted the formation of GCD as the major product. The principle reactive oxidizing species (ROS) contributing for glycerol conversion via black TiO2 can be ranked in the order of O2•->O12>OHb•>h+/OHs•>h+. The dominate ROS related to the conversion of glycerol to GCD and DHA were O2•- and OHb•, respectively. The main ROS to alter GCD and DHA to GCAD/FMD was O2•-, while the h+ was the principle ROS to convert GCD to GCOA. Finally, the pathway of glycerol conversion and product distribution over black TiO2 via various ROS in the presence of oxygen as electron acceptor is proposed.

DOI： 10.1016/j.jphotochem.2018.08.030

One-pot synthesis of purple benzene-derived MnO<inf>2</inf>-carbon hybrids and synergistic enhancement for the removal of cationic dyes Reviewed

Kim H., Saito N.

Scientific Reports Vol. 8 ( 1 ) 2018.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Scientific Reports

MnO2-carbon hybrid (MnO2-C-PBz) was simultaneously synthesized by a one-step solution plasma process (SPP) using a single precursor referred to as "purple benzene", which was derived from the K+(dicyclohexano-18-crown-6 ether) complex. To clarify the synergistic effects on the cationic dye removal, MnO2-free carbon and carbon-free MnO2 samples were concurrently investigated. The results of adsorption for cationic dyes (methylene blue (MB) and rhodamine B (Rh B)) and anionic dye (methyl orange (MO)) revealed remarkably high affinity for cationic dyes. In particular, MnO2-C-PBz exhibited the highest adsorption capacity for MB, i.e., ∼3 times greater than that of the others. In addition, MnO2-C-PBz exhibited a rapid, high decolorization ability at C0 = 10 mg L-1 (within a few seconds, ∼99%) and at C0 = 100 mg L-1 (within 30 min, ∼81%), and the theoretical maximum monolayer adsorption capacity was 357.14 mg g-1 as calculated from the Langmuir adsorption isotherm equation. Furthermore, compared with carbon-free MnO2, MnO2-C-PBz exhibited quite a good cyclic stability. We expect that our findings give rise to the understanding of the synergistic effects of MnO2-carbon hybrid, as well as role of each components for the cationic dye adsorption, and may open an innovative synthesis approach to inorganic-organic hybrid materials.

DOI： 10.1038/s41598-018-22203-1

Narrowing band gap energy of defective black TiO<inf>2</inf> fabricated by solution plasma process and its photocatalytic activity on glycerol transformation

Jedsukontorn T., Ueno T., Saito N., Hunsom M.

Journal of Alloys and Compounds Vol. 757 page： 188 - 199 2018.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Alloys and Compounds

Defective black titania (TiO2) was synthesized by the solution plasma technique at ambient temperature and pressure. The effects of the electrolyte solution medium type (KCl and HNO3) and concentration (0.3 and 3.0 mM) as well as the plasma discharge time (1–4 h) with a Ti electrode were investigated. The 3.0 mM HNO3 solution provided the highest energy per second discharging into the plasma, resulting in both a high synthesis rate of black TiO2 and a high degree of defective structures, as monitored in terms of the Ti3+/Ti4+ ratio, which can shorten the band gap energy (Eg) of the obtained black TiO2. A long plasma discharge time (4 h) induced the formation of large particles of black TiO2, which appeared as a highly defective structure. Overall, the black TiO2 prepared by discharged plasma for 4 h in 3.0 mM HNO3 solution (BTN-304) provided the highest photocatalytic activity for glycerol conversion (58.49% at 24 h) and 4.85, 3.32, 2.11, 2.15, 39.15 and 26.61% yield of glyceraldehyde, dihydroxyacetone, hydroxypyruvic acid, glycolic acid, glycolaldehyde and formaldehyde, respectively. Pathway of glycerol conversion and product distribution over black TiO2 was attempted to propose. Finally, the reusability of the best black TiO2 was explored.

DOI： 10.1016/j.jallcom.2018.05.046

Thickness-Dependent Strain Evolution of Epitaxial SrTiO<inf>3</inf> Thin Films Grown by Ion Beam Sputter Deposition

Panomsuwan G., Saito N.

Crystal Research and Technology Vol. 53 ( 8 ) 2018.8

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

Epitaxial SrTiO3 (STO) thin films are grown on vicinal (001)-oriented LaAlO3 (LAO) substrates with various thicknesses (3–108 nm) by an ion beam sputter deposition (IBSD). Thickness-dependent strain in the STO films is investigated comprehensively through the X-ray analysis. The STO films grow on the LAO substrates under a compressive strain along in-plane direction (a- and b-axes) and a tensile strain along the growth direction (c-axis). With increasing film thickness, the STO unit cells evolve from more to less tetragonal structure, indicating the occurrence of strain relaxation. Quantitative strain analysis is also carried out for all STO films in terms of biaxial and hydrostatic components. It is found that the major cause of strain in STO films is caused by biaxial component over hydrostatic component. The surface morphology of STO films exhibit a step-and-terrace structure with roughness close to the LAO substrate (approx. 0.1 nm), indicating a 2D growth mode. However, as the film thickness increases, the surface terrace become rougher, which is caused by the effect of strain relaxation.

DOI： 10.1002/crat.201700211

Enhancing Bifunctional Catalytic Activity of Oxygen Reduction and Evolution Reaction via One-Pot Formation of MnO<inf>2</inf>-Carbon Hybrid Nanocomposite

Kim H., Saito N., Kim D.

ChemistrySelect Vol. 3 ( 23 ) page： 6302 - 6308 2018.6

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

While manganese dioxide (MnO2) is a promising bifunctional electrocatalyst for oxygen reduction and evolution reaction (ORR/OER) in alkaline media, electrochemical performance of bulk MnO2 limited by their poor electrical conductivity. Herein, we fabricate a MnO2-carbon nanoparticle hybrid composite (MO-CNP) by applying the plasma discharge in the single precursor of purple benzene. This synthesis route facilitates a simultaneous formation of MnO2 and carbon, which induced a homogeneously mixed and firmly anchored hybrid composite. As a result, as-obtained MO-CNP-1 shows more than 12 times higher electrical conductivity than that of prepared conventionally. Thus, formation of MO-CNP could be accompanied by a synergy between MnO2 and CNP as electrocatalyst, and consequently, electrochemical properties were significantly improved. In comparison with CNP, the ORR potential of MO-CNP-1 was positively shifted from –0.28 to –0.23 V (vs. Ag/AgCl), and current density has increased more than 2 times. Although the ORR activity of MO-CNP-1 was still far a little short of the commercial Pt/C, the MO-CNP-1 indicated significant higher OER activity, which demonstrated excellent overall catalytic capability of MO-CNP-1 as bifunctional catalyst.

DOI： 10.1002/slct.201800851

Nano-Assembled Thin Films of Tetraphenylporphyrin on Amine Silane-Modified Substrate for the Optical Gas Sensor

Tipplook, M; Hashimi, K; Bratescu, MA; Saito, N

NANOSCIENCE AND NANOTECHNOLOGY LETTERS Vol. 10 ( 5-6 ) page： 667 - 674 2018.5

The Nano-Structure and Their Properties of Exfoliation Several Layers-Stacked Graphene Prepared from Graphite Dispersed in Aqueous Solutions by Solution Plasma

Chae, S; Hashimi, K; Bratescu, MA; Saito, N

NANOSCIENCE AND NANOTECHNOLOGY LETTERS Vol. 10 ( 5-6 ) page： 784 - 789 2018.5

The Initial Reactions from Pyridine to Hetero-Carbon Nanomaterials Through Solution Plasma

Kim, K; Hashimi, K; Bratescu, MA; Saito, N

NANOSCIENCE AND NANOTECHNOLOGY LETTERS Vol. 10 ( 5-6 ) page： 814 - 819 2018.5

Photoinduced glycerol oxidation over plasmonic au and aum (M = Pt, Pd and Bi) nanoparticle-decorated TiO<inf>2</inf> photocatalysts

Jedsukontorn T., Saito N., Hunsom M.

Nanomaterials Vol. 8 ( 4 ) 2018.4

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

In this study, sol-immobilization was used to prepare gold nanoparticle (Au NP)-decorated titanium dioxide (TiO2) photocatalysts at different Au weight % (wt. %) loading (Aux/TiO2, where x is the Au wt. %) and Au–M NP-decorated TiO2 photocatalysts (Au3M3/TiO2), where M is bismuth (Bi), platinum (Pt) or palladium (Pd) at 3 wt. %. The Aux/TiO2 photocatalysts exhibited a stronger visible light absorption than the parent TiO2 due to the localized surface plasmon resonance effect. Increasing the Au content from 1 wt. % to 7 wt. % led to increased visible light absorption due to the increasing presence of defective structures that were capable of enhancing the photocatalytic activity of the as-prepared catalyst. The addition of Pt and Pd coupled with the Au3/TiO2 to form Au3M3/TiO2 improved the photocatalytic activity of the Au3/TiO2 photocatalyst by maximizing their light-absorption property. The Au3/TiO2, Au3Pt3/TiO2 and Au3Pd3/TiO2 photocatalysts promoted the formation of glyceraldehyde from glycerol as the principle product, while Au3Bi3/TiO2 facilitated glycolaldehyde formation as the major product. Among all the prepared photocatalysts, Au3Pd3/TiO2 exhibited the highest photocatalytic activity with a 98.75% glycerol conversion at 24 h of reaction time.

DOI： 10.3390/nano8040269

Accelerated formation of nanocarbons in solution plasma using benzene substituted with CF<inf>3</inf> group

Panomsuwan G., Li O.L., Saito N., Ishizaki T.

Japanese Journal of Applied Physics Vol. 57 ( 1 ) 2018.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

Nanocarbons were synthesized by a solution plasma method using benzene (C6H6) and benzotrifluoride (C5H5CF3) as precursors. The effects of the substituted CF3 group on the overall properties of synthesized nanocarbons were investigated and discussed. As determined from the characterization results, the nanocarbons obtained from both benzene and benzotrifluoride mainly exhibited an amorphous structure and their diameter was about 20-40 nm. There were no notable differences in morphology, surface area, and crystalline structure observed between them. Interestingly, the synthesis rate of nanocarbons from benzotrifluoride (20.3 mg/min) was almost three fold higher than that from benzene (7.6 mg/min). Moreover, a lower H/C ratio was observed in the case of nanocarbons from benzotrifluoride, indicating its more efficient H abstraction. The higher synthesis rate and lower H/C ratio of nanocarbons from benzotrifluoride were possibly attributed to the CF3 radicals generated in the reaction fields of solution plasma during synthesis.

DOI： 10.7567/JJAP.57.0102B6

Degradation of chitosan hydrogel dispersed in dilute carboxylic acids by solution plasma and evaluation of anticancer activity of degraded products

Chokradjaroen C., Rujiravanit R., Theeramunkong S., Saito N.

Japanese Journal of Applied Physics Vol. 57 ( 1 ) 2018.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

Chitosan is a polysaccharide that has been extensively studied in the field of biomedicine, especially its water-soluble degraded products called chitooligosaccharides (COS). In this study, COS were produced by the degradation of chitosan hydrogel dispersed in a dilute solution (i.e., 1.55 mM) of various kinds of carboxylic acids using a non-thermal plasma technology called solution plasma (SP). The degradation rates of chitosan were influenced by the type of carboxylic acids, depending on the interaction between chitosan and each carboxylic acid. After SP treatment, the water-soluble degraded products containing COS could be easily separated from the water-insoluble residue of chitosan hydrogel by centrifugation. The production yields of the COS were mostly higher than 55%. Furthermore, the obtained COS products were evaluated for their inhibitory effect as well as their selectivity against human lung cancer cells (H460) and human lung normal cells (MRC-5).

DOI： 10.7567/JJAP.57.0102B5

In vitro cytotoxicity of carbon black nanoparticles synthesized from solution plasma on human lung fibroblast cells

Panomsuwan G., Chokradjaroen C., Rujiravanit R., Ueno T., Saito N.

Japanese Journal of Applied Physics Vol. 57 ( 1 ) 2018.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

Carbon black nanoparticles (CB-NPs) have been synthesized from liquid benzene by a solution plasma method at room temperature and atmospheric pressure. The morphological observation by scanning electron microscopy revealed the agglomeration of aggregated fine particles. The synthesized CB-NPs were predominantly amorphous as confirmed by X-ray diffraction. The in vitro cytotoxicity of CB-NPs on the human lung fibroblast (MRC-5) cell line was assessed by the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and systematically compared with those of two types of commercial carbon blacks (i.e., Vulcan XC-72 and Ketjenblack EC-600JD). Cell viabilities were studied at different concentrations of 32.5, 65, 125, and 250 μg/mL. It was found that the CB-NPs derived from solution plasma exhibited a lower cytotoxicity on the MRC-5 cells than the other two comparative carbon blacks. The viability of MRC-5 cells exposed to CB-NPs remained higher than 90% even at a high concentration of 250 μg/mL. This result preliminarily confirmed the biosafety and potential use of CB-NPs in the field of biological applications.

DOI： 10.7567/JJAP.57.0102BG

Plasma in Solution and Its Applications

Saito N., Nakamura J., Shirafuji T., Ishizaki T.

Japanese Journal of Applied Physics Vol. 57 ( 1 ) 2018.1

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