Faculty Profiles - SAITO, Nagahiro

Papers - SAITO, Nagahiro

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Facile synthesis of ZnO nanobullets by solution plasma without chemical additives

Kim K., Chae S., Choi P.G., Itoh T., Saito N., Masuda Y.

RSC Advances Vol. 11 ( 43 ) page： 26785 - 26790 2021.7

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

ZnO nano-bullets were synthesized using solution plasma from only Zn electrode in water without any chemical agents. In this sustainable synthesis system, the rapid quenching reaction at the interface between the plasma/liquid phases facilitates the fast formation of nano-sized materials. The coil-to-pin type electrode geometry, which overcomes the discharge interruption owing to the electrode gap broadening of the typical pin-to-pin type enables the synthesis of numerous nanomaterials through a stable discharge for 1 h. The as-prepared samples exhibited a high crystalline ZnO structure without post calcination, and the length and width were 71.8 and 29.1 nm, respectively. The main exposed facet of ZnO nano-bullets was the (100) crystal facet, but interestingly, the (101) facet was confirmed at the inclined surfaces in the edges. The (101) crystal facet has an asymmetric Zn and O atom arrangement, and it could result in a focused electron density area with relatively high reactivity. Therefore, ZnO nano-bullets are promising materials for applications in advanced technologies.

DOI： 10.1039/d1ra05008g

Reduced Red Mud as the Solar Absorber for Solar-Driven Water Evaporation and Vapor-Electricity Generation

Wang P., Wang X., Chen S., Zhang J., Mu X., Chen Y., Sun Z., Wei A., Tian Y., Zhou J., Liang X., Miao L., Saito N.

ACS Applied Materials and Interfaces Vol. 13 ( 26 ) page： 30556 - 30564 2021.7

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

The emergent solar-driven water evaporation technology provides a reassuring scheme for red mud (RM) utilization in environment and materials science. With fewer restrictions on raw materials, wide availability of sheer quantity, and high complexity in chemical composition, the RM may be a promising candidate for solar absorbers. Here, we developed a novel solar absorber with reduced RM. It features favorable light absorption and photothermal conversion ability using biomass pyrolysis. When added to the polyvinyl alcohol and chitosan gel substrate, the light absorptance can reach 94.65%, while the corresponding evaporation rate is as high as 2.185 kg m-2 h-1 under an illumination density of 1 kW m-2. We further demonstrated its potential as an efficient solar absorber in the solar-driven water evaporation and the thermoelectric device to realize the stable and efficient coproduction of vapor and electricity.

DOI： 10.1021/acsami.1c05228

Cationic nitrogen-doped graphene as a p-type modifier for high-performance PEDOT:PSS hole transporters in organic solar cells

Lin H.S., Kaneko T., Ishikawa S., Jeon I., Chae S., Yana T., Saito N., Matsuo Y.

Japanese Journal of Applied Physics Vol. 60 ( 7 ) 2021.7

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

This research paper reports the enhanced hole-transporting ability of widely utilized poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) achieved by applying cationic nitrogen-doped graphene (CNG) as a p-type modifier for efficient organic solar cells (OSCs). The power conversion efficiency (PCE) of the CNG-coated PEDOT:PSS-applied OSC reaches 2.76%, which is an increase of 40% compared to that of the pristine PEDOT:PSS-applied OSC (1.96%). The significantly enhanced performance is contributed by the increased hole-transporting ability, and the improved interfacial morphology of PEDOT:PSS, which affords high-quality active layers.

DOI： 10.35848/1347-4065/ac00fc

Facile in Situ Synthesis of Amphiphilic Carbon-Supported Pt: Innovative Catalyst Preparation for Proton Exchange Membrane Fuel Cells

Tipplook M., Panomsuwan G., Muta Y., Saito N.

ACS Applied Energy Materials Vol. 4 ( 6 ) page： 5606 - 5614 2021.6

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

Carbon materials are widely utilized to support platinum (Pt) catalysts for proton exchange membrane fuel cells (PEMFCs). However, carbon surfaces generally promote hydrophobicity, which limits the transport of active species and lowers the efficiency of PEMFCs. Consequently, functional groups should be introduced on the carbon surface to create transport channels. One promising strategy is to modify the amphiphilic functional group on a carbon surface. In this study, the liquid-phase plasma process was applied to realizing a facile one-step synthesis of amphiphilic functional group-modified carbon-supported platinum (Am@C/Pt) to serve as a catalyst. This novel synthesis strategy provides several advantages over conventional processes, such as reducing the number of steps and minimizing the chemical and energy consumptions. Experimental results revealed that the PEMFCs' efficiency with Am@C/Pt is mainly controlled by the number of hydrophilic and hydrophobic characters on the carbon surface. A single PEMFC demonstrated a maximum current and power density of 2.41 A cm-2 and 1.68 W cm-2, respectively, at 0.7 V, which was significantly higher than those of commercially available carbon-supported Pt catalysts. Furthermore, Am@C/Pt demonstrated superior durability after 5000 test cycles.

DOI： 10.1021/acsaem.1c00406

Insight on solution plasma in aqueous solution and their application in modification of chitin and chitosan

Chokradjaroen C., Niu J., Panomsuwan G., Saito N.

International Journal of Molecular Sciences Vol. 22 ( 9 ) 2021.5

Language：English Publishing type：Research paper (scientific journal) Publisher：International Journal of Molecular Sciences

Sustainability and environmental concerns have persuaded researchers to explore renewable materials, such as nature-derived polysaccharides, and add value by changing chemical structures with the aim to possess specific properties, like biological properties. Meanwhile, finding methods and strategies that can lower hazardous chemicals, simplify production steps, reduce time consumption, and acquire high-purified products is an important task that requires attention. To break through these issues, electrical discharging in aqueous solutions at atmospheric pressure and room temperature, referred to as the “solution plasma process”, has been introduced as a novel process for modification of nature-derived polysaccharides like chitin and chitosan. This review reveals insight into the electrical discharge in aqueous solutions and scientific progress on their application in a modification of chitin and chitosan, including degradation and deacetylation. The influencing parameters in the plasma process are intensively explained in order to provide a guideline for the modification of not only chitin and chitosan but also other nature-derived polysaccharides, aiming to address economic aspects and environmental concerns.

DOI： 10.3390/ijms22094308

Deposition of carbon–tungsten carbide on coir pulp to improve its compatibility with polylactic acid

Boonyeun N., Rujiravanit R., Saito N.

Cellulose Vol. 28 ( 7 ) page： 4119 - 4136 2021.5

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

To increase hydrophobicity of surfaces of coir pulp, carbon–tungsten carbide (WC) was synthesized and simultaneously deposited on coir pulp by applying in-liquid electrical discharge plasma, so-called solution plasma process (SPP). As a result, water contact angle of carbon-WC deposited coir pulp was 123.4°, whereas that of coir pulp was 82.8°. The carbon-WC deposited coir pulp was then used as a filler in polylactic acid (PLA) to attain composite films of PLA/carbon-WC deposited coir pulp. The deposition of carbon-WC on coir pulp not only increased hydrophobicity of coir pulp but also improved compatibility between the filler and PLA. Even at the low filler content of 0.75 wt%, tensile strength and Young’s modulus of composite films of PLA/carbon-WC deposited coir pulp increased up to 45.73% and 22.79%, respectively compared with those of neat PLA film. Furthermore, the presence of carbon-WC deposited coir pulp in the PLA composite films could enhance the formation of crystalline structure of PLA. Accordingly, SPP is an interesting tool for surface modification of coir pulp in order to achieve surface-functionalized coir pulp for using as a filler in green composites. Graphic abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s10570-021-03799-6

Li-air battery and ORR activity of nanocarbons produced with good synthesis rate by solution plasma process Reviewed

Islam M.Z., Watthanaphanit A., Chae S., Saito N.

Materials Advances Vol. 2 ( 8 ) page： 2636 - 2641 2021.4

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Advances

Nanocarbons were successfully synthesized from benzene (BZ), nitro-benzene (BZ-NO2) and aniline (BZ-NH2) by solution plasma process (SPP). The SPP was generated by a bipolar pulsed power supply between two tungsten electrodes at room temperature. The synthesized nanocarbons were investigated. The highest synthesis rate, 40 mg min-1, was for the BZ nanocarbon. The transmission electron microscopy (TEM) morphology showed that the nanocarbon sizes were 15-25 nm. The Brunauer-Emmett-Teller (BET) analysis shows a highest surface area of 220 m2 g-1, pore size of 0.45 cm3 g-1, and average pore diameter of 20.0 nm for the BZ nanocarbon. Cyclic voltammetry (CV) in an acidic medium exhibited the oxygen reduction reaction (ORR) of the nanocarbons. The nanocarbon from BZ-NH2 obtained a high special capacity of 15 500 mA h per g of carbon at the discharge rate of 0.1 mA cm-2 with 1.0 mg carbon loading for the lithium (Li)-air battery. The ORR is an important reaction in Li-air batteries and fuel cells for the application of next-generation batteries and energy conversion devices.

DOI： 10.1039/d0ma00926a

Plasma-assisted synthesis of multicomponent nanoparticles containing carbon, tungsten carbide and silver as multifunctional filler for polylactic acid composite films

Boonyeun N., Rujiravanit R., Saito N.

Polymers Vol. 13 ( 7 ) 2021.4

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

Multicomponent nanoparticles containing carbon, tungsten carbide and silver (carbon-WC-Ag nanoparticles) were simply synthesized via in-liquid electrical discharge plasma, the so-called solution plasma process, by using tungsten electrodes immersed in palm oil containing droplets of AgNO3 solution as carbon and silver precursors, respectively. The atomic ratio of carbon:W:Ag in carbon-WC-Ag nanoparticles was 20:1:3. FE-SEM images revealed that the synthesized carbon-WC-Ag nanoparticles with particle sizes in the range of 20–400 nm had a spherical shape with a bumpy surface. TEM images of carbon-WC-Ag nanoparticles showed that tungsten carbide nanoparticles (WCNPs) and silver nanoparticles (AgNPs) with average particle sizes of 3.46 nm and 72.74 nm, respectively, were dispersed in amorphous carbon. The carbon-WC-Ag nanoparticles were used as multifunctional fillers for the preparation of polylactic acid (PLA) composite films, i.e., PLA/carbon-WC-Ag, by solution casting. Interestingly, the coexistence of WCNPs and AgNPs in carbon-WC-Ag nanoparticles provided a benefit for the co-nucleation ability of WCNPs and AgNPs, resulting in enhanced crystallization of PLA, as evidenced by the reduction in the cold crystallization temperature of PLA. At the low content of 1.23 wt% carbon-WC-Ag nanoparticles, the Young’s modulus and tensile strength of PLA/carbon-WC-Ag composite films were increased to 25.12% and 46.08%, respectively. Moreover, the PLA/carbon-WC-Ag composite films possessed antibacterial activities.

DOI： 10.3390/polym13070991

N-Doped few-layer graphene encapsulated Pt-based bimetallic nanoparticles: Via solution plasma as an efficient oxygen catalyst for the oxygen reduction reaction

Phan P.Q., Naraprawatphong R., Pornaroontham P., Park J., Chokradjaroen C., Saito N.

Materials Advances Vol. 2 ( 1 ) page： 322 - 335 2021

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

N-Doped few-layer graphene encapsulated Pt-based bimetallic nanoparticles were successfully synthesized via the solution plasma (SP) method. This synthesis strategy can be achieved in one pot by using only pure dimethylformamide (DMF) as the reaction solution at room temperature and atmospheric pressure. The structural analyses exhibited a fine core-shell structured nanoparticle (2-4 nm), which had Pt and Pt-based bimetallic nanoparticles as a core and N-doped few-layer graphene (NFG), having 2-4 layers, as a shell. Pt-based bimetallic cores (i.e., PtAu, PtAg, and PtPd) were varied depending on the metal electrodes used in the SP process. The electrocatalytic activity toward the oxygen reduction reaction (ORR) of the obtained samples in an acidic solution was found to be acceptable, while possessing excellent durability, compared to those of the commercial carbon-supported Pt catalyst. The effective ORR activity was possibly attributed to the synergistic effect of the Pt-based bimetallic core and N-doped graphene shell which contained high amounts of pyridinic-N and quaternary-N. The results in a single fuel cell test expressed the superiority of our SP-derived sample in the fuel cell performances to commercial Pt/C. This study not only proposed potential alternative ORR catalysts with acceptable electrocatalytic activity and high durability but also provided guidelines for the facile synthesis of carbon-based core-shell nanostructured materials with low chemical use via the SP process. This journal is

DOI： 10.1039/d0ma00718h

Natural Self-Confined Structure Effectively Suppressing Volume Expansion toward Advanced Lithium Storage Reviewed International coauthorship

Zhang Y., Huang J., Liao Z., Hu A., Li X., Saito N., Zhang Z., Yang L., Hirano S.I.

ACS Applied Materials and Interfaces 2021

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

Volume expansion hinders conversion-type transition-metal oxides (TMOs) as potential anode candidates for high-capacity lithium-ion batteries. While nanostructuring and nanosizing have been employed to improve the cycling stability of TMOs, we show here that both high initial Coulombic efficiency (ICE) and stable cycling reversibility are achieved in the layered compound Li0.9Nb0.9Mo1.1O6 (L0.9NMO) by inherent properties of the bulk crystal structure. In this model, MoO6 octahedra as active centers react with lithium ions and endow capacity, while a grid composed of NbO6 octahedra effectively suppresses the volume expansion, enhances the conductivity, and supports the structural skeleton from collapse. As a result, bulk L0.9NMO not only delivers a high discharge capacity of 1128 mA h g-1 at 100 mA g-1 with a considerable ICE of 87% but also exhibits long cycling stability and good rate performance (339 mA h g-1 after 500 cycles at 1 A g-1 with an average Coulombic efficiency approaching 100%). The self-confined structure provides a competitive strategy for stable conversion-type lithium storage.

DOI： 10.1021/acsami.1c02269

Safe, superionic conductive and flexible “polymer-in-plastic salts” electrolytes for dendrite-free lithium metal batteries

Liao Z., Huang J., Chen W., Saito N., Zhang Z., Yang L., Hirano S.i.

Energy Storage Materials Vol. 33 page： 442 - 451 2020.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Energy Storage Materials

Solid polymer electrolytes (SPEs) garner tremendous attention for both enabling higher energy density battery chemistry and alleviating the safety concerns of liquid electrolytes, but the practical utilizations of SPEs are severely hindered by the limited room temperature ionic conductivity, low transference number and huge interface impedance. Unlike the polymer chain movement in traditional SPEs, in the present work, we develop novel “polymer-in-plastic salts” electrolytes (PIPSEs) via a high weight ratio of plastic salts to polymer in which polymer just function as framework so that non-flammable, superionic conductive and flexible SPEs can be obtained. Also, the high content of plastic salts in PIPSEs can wet electrodes and form compatible solid electrolyte interface (SEI) with lithium metal. As a consequence, solid-state dendrite-free symmetric Li cells with PIPSEs show ultralong cycle life over 1000 h under up to 2.0 mA cm−2 and Li/LiFePO4 and high-voltage Li/LiNi0.6Co0.2Mn0.2O2 cells utilizing above PIPSEs exhibit excellent cycle performance and appealing rate performance. It is anticipated that our work provides a new strategy for the next-generation solid-state batteries.

DOI： 10.1016/j.ensm.2020.09.003

Single-walled carbon nanotubes wrapped by cationic nitrogen-doped carbon for electrocatalytic applications Reviewed International coauthorship

Chae S., Phan P.Q., Panomsuwan G., Bratescu M.A., Hashimoto T., Teshima K., Saito N.

ACS Applied Nano Materials Vol. 3 ( 10 ) page： 10183 - 10189 2020.10

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ACS Applied Nano Materials

The exploration of novel carbon material systems has emerged as a promising strategy for yielding unique and unconventional functional properties. In this study, a cationic nitrogen-doped carbonwrapped single-walled carbon nanotube (CN-C@SWCNT) was synthesized for the first time via solution plasma (SP) by using an aniline aqueous solution with the SWCNT dispersion under ambient conditions. The reactive species produced from SP led to the formation of cationic nitrogendoped carbon (CN-C) completely wrapped around SWCNT. Raman spectroscopy, electron diffraction, and X-ray photoelectron spectroscopy confirmed the presence of cationic nitrogen. CN-C@SWCNT exhibited an excellent electrical conductivity of 120.30 S cm-1. Room-temperature halleffect measurements revealed p-type semiconducting behavior for CN-C@ SWCNT, with a carrier concentration of 4.6 × 1020 cm-3. The electrical conductivity and carrier concentration of p-type CN-C@SWCNT were greater than those reported previously for carbon-based materials. The high electrical properties of CN-C@SWCNT were synergistically related to a conducting bridge between CN-C and SWCNT conducting domains and the presence of doped cationic nitrogen. The SP-synthesized CN-C@SWCNT demonstrates immense potential as an emerging class of p-type carbon materials in advanced electrocatalytic applications.

DOI： 10.1021/acsanm.0c02164

In situ synthesis of copper nanoparticles encapsulated by nitrogen-doped graphene at room temperature via solution plasma

Phan P.Q., Chae S., Pornaroontham P., Muta Y., Kim K., Wang X., Saito N.

RSC Advances Vol. 10 ( 60 ) page： 36627 - 36635 2020.10

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

Metal-carbon core-shell nanostructures have gained research interest due to their better performances in not only stability but also other properties, such as catalytic, optical, and electrical properties. However, they are limited by complicated synthesis approaches. Therefore, the development of a simple method for the synthesis of metal-carbon core-shell nanostructures is of great significance. In this work, a novel Cu-core encapsulated by a N-doped few-layer graphene shell was successfully synthesized in a one-pot in-liquid plasma discharge, so-called solution plasma (SP), to our knowledge for the first time. The synthesis was conducted at room temperature and atmospheric pressure by using a pair of copper electrodes submerged in a DMF solution as the precursor. The core-shell structure of the obtained products was confirmed by HR-TEM, while further insight information was explained from the results of XRD, Raman, and XPS measurements. The obtained Cu-core encapsulated by the N-doped few-layer graphene shell demonstrated relatively high stability in acid media, compared to the commercial bare Cu particles. Moreover, the stability was found to depend on the thickness of the N-doped few-layer graphene shell which can be tuned by adjusting the SP operating conditions. This journal is

DOI： 10.1039/d0ra07162e

Solution plasma: new synthesis method of N-doped carbon dots as ultra-sensitive fluorescence detector for 2,4,6-trinitrophenol Reviewed International coauthorship

Kim K., Chokradjaroen C., Saito N.

Nano Express Vol. 1 ( 2 ) 2020.9

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

Herein, we report the synthesis of nitrogen-doped carbon dots (NCDs) through solution plasma (SP) for the first time. The SP method occurs a rapid dissociation of molecules, such as organic compounds, caused by an electrical discharge between electrodes immersed in a solution. The dissociation can result in the creation of various radicals such as ·C2, ·CN, and ·H which enable the rapid synthesis of carbon dots (CDs). The unique reaction of radicals allowed the formation of CDs with high N concentration and functionalization of the surface in a short time. In this study, by using the SP method, a very fine NCDs with size of 6 nm were synthesized from a pyridine/water mixture in just 10 min. Bright blue fluorescence (410 nm) with a high quantum yield (61%) was observed due to the high N concentration and the surface passivation. From the potential application point of view, the synthesized NCDs showed an excellent detection property for 2,4,6-trinitrophenol (TNP) by fluorescence quenching effect. It was due to rich amino-functional groups which act as a reaction pathway to TNP. This phenomenon was caused by the synergetic effect of a photo-induced electron transfer with the assistance of proton transfer-assisted electron transfer.

DOI： 10.1088/2632-959X/abb9fa

Effect of electrical discharge plasma on cytotoxicity against cancer cells of N,O-carboxymethyl chitosan-stabilized gold nanoparticles

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

Carbohydrate Polymers Vol. 237 2020.6

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

Electrical discharge plasma in a liquid phase can generate reactive species, e.g. hydroxyl radical, leading to rapid reactions including degradation of biopolymers. In this study, the effect of plasma treatment time on physical properties and cytotoxicity against cancer cells of N,O-carboxymethyl chitosan-stabilized gold nanoparticles (CMC-AuNPs) was investigated. AuNPs were synthesized by chemical reduction of HAuCl4 in 2 % CMC solution to obtain CMC-AuNPs, before being subjected to the plasma treatment. Results showed that the plasma treatment not only led to the reduction of hydrodynamic diameters of CMC-AuNPs from 400 nm to less than 100 nm by the plasma-induced degradation of CMC but also provided the narrow size distribution of AuNPs having diameters in the range of 2–50 nm, that were existing in CMC-AuNPs. In addition, the plasma-treated CMC-AuNPs could significantly reduce the percentage of cell viability of breast cancer cells by approximately 80 % compared to the original CMC and CMC-AuNPs.

DOI： 10.1016/j.carbpol.2020.116162

Fabrication of biocomposite membrane with microcrystalline cellulose (MCC) extracted from sugarcane bagasse by phase inversion method

Thiangtham S., Runt J., Saito N., Manuspiya H.

Cellulose Vol. 27 ( 3 ) page： 1367 - 1384 2020.2

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

Abstract: The design of biocomposite membranes based on microcrystalline cellulose (MCC) extracted from sugarcane bagasse added into matrices of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) was fabricated by the phase inversion method. The pore formation of biocomposite membranes was prepared by the phase inversion method, and the obtained biocomposite membranes showed a tunable microstructure formed in the membranes that was investigated by field-emission scanning electron microscope. Due to the high porosity and hydrophilic properties of MCC, the biocomposite membranes demonstrated excellent electrolyte wettability, large electrolyte uptake (up to 138%), and smaller interfacial resistance leading to enhancement of the ionic conductivity. Furthermore, the effects of MCC on the thermal properties of biocomposite membranes were evaluated by differential scanning calorimetry and the thermal shrinkage test. The addition of 5 wt% MCC showed the outstanding thermal stability of the biocomposite membranes. After thermal treatment at 135 °C for 1 h, this biocomposite membrane exhibited shrinkage of only 32% from the original shape while the PLA/PBS membrane showed shrinkage of 81%, which verifies that the introduction of MCC improves the thermal stabilities of biocomposite membranes. Promisingly, the biocomposite membranes represent candidate alternatives for future battery applications. Graphic abstract: [Figure not available: see fulltext.].

DOI： 10.1007/s10570-019-02866-3

Liquid-Phase Plasma-Assisted in Situ Synthesis of Amino-Rich Nanocarbon for Transition Metal Ion Adsorption

Tipplook M., Pornaroontham P., Watthanaphanit A., Saito N.

ACS Applied Nano Materials Vol. 3 ( 1 ) page： 218 - 228 2020.1

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

Amino-modified nanocarbon (NH2-C) has been widely used as an adsorbent for transition metal ion adsorption due to its high specific surface area, high electrical charge, and the ability to form a coordinate linkage to a transition metal ion. In this work, NH2-C was successfully synthesized from a mixture of phenol and (3-aminopropyl)triethoxysilane (APTES) through solution plasma processing, which performs both carbonization and amination simultaneously. This synthesis method eliminates the need to functionalize carbon with amino groups, as is required in the conventional process. Our NH2-C shows a better dispersion and a higher number of amino groups on both the external surface and inner pores, which enhances the adsorption capacity. The maximum capacities for Cu2+, Zn2+, and Cd2+ adsorption were 144.9, 115.4, and 102.0 mg g-1, respectively. These values were higher than those of five typical NH2-Cs synthesized by a conventional process. Based on the adsorption mechanism derived from adsorption kinetic, isotherm, and thermodynamic studies, the transition metal ions were chemisorbed to the surface in a monolayer endothermically and spontaneously. Moreover, it was found that NH2-C was suitable for use in ten consecutive adsorption-desorption cycles without significant loss of adsorption capacity.

DOI： 10.1021/acsanm.9b01915

Simultaneous deacetylation and degradation of chitin hydrogel by electrical discharge plasma using low sodium hydroxide concentrations

Rujiravanit R., Kantakanun M., Chokradjaroen C., Vanichvattanadecha C., Saito N.

Carbohydrate Polymers Vol. 228 2020.1

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

Electrical discharge plasma occurring in a liquid phase, so called solution plasma, can generate highly active species, e.g. free radicals, which can involve in various chemical reactions, leading to less chemical uses. In this study, solution plasma was applied to deacetylation of chitin aiming to reduce the use of alkali. It was found that solution plasma could induce deacetylation of chitin hydrogels that were dispersed in MeOH/water solutions containing low NaOH concentrations (1–12%). Due to the action of free radicals, some extent of chain session of the polymer occurred during the plasma treatment. The degree of deacetylation and molecular weight of the obtained chitosan were 78% and 220 kDa, respectively, after the plasma treatment for five cycles (1 h/cycle) by using 90% MeOH/water solution containing 12% NaOH. The obtained chitosan could completely dissolve in 2% acetic acid solution and had antibacterial activities against S. aureus and E. coli.

DOI： 10.1016/j.carbpol.2019.115377

Synthesis of Au Nanoparticles in Natural Matrices by Liquid-Phase Plasma: Effects on Cytotoxic Activity against Normal and Cancer Cell Lines Reviewed International coauthorship

Treesukkasem N., Chokradjaroen C., Theeramunkong S., Saito N., Watthanaphanit A.

ACS Applied Nano Materials Vol. 2 ( 12 ) page： 8051 - 8062 2019.12

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

Wrapping of gold nanoparticles (AuNPs) with a biocompatible matrix, to gain AuNP colloids, is a general strategy to synthesize the AuNPs for biomedical purposes. This work reports the synthesis of AuNP colloids in the aqueous solution of several natural matrices using a liquid-phase plasma process. Two classes of natural substances used are sugars (including: glucose, fructose, and sucrose) and biopolymers (including: carboxymethyl cellulose, sodium alginate, and gelatin). All are negatively charged water-soluble substances that are claimed to be sources of energy for cells to grow and have a high potential to be compatible with them. The study has emerged since one question arises: "Do these matrices also promote the growth of cancer cells?" The synthesis is performed by generating plasma across a pair of electrodes immersed in an aqueous solution of a natural matrix containing a gold precursor (HAuCl4·3H2O). Two concentrations of the matrices (0.5 and 1.0% w/v) are used, and the plasma treatment times are varied (0, 10, and 30 min). The effect of the type and concentration of natural matrices as well as the plasma treatment time on the formation of AuNPs, along with their physical and chemical properties, including morphology, size, hydrodynamic diameter (dh), colloidal stability, and charge on the AuNP surface, is evaluated. We find that the charge of the AuNP surfaces could be altered by the plasma treatment. Eventually, cytotoxicity test results against normal (MRC-5) and cancer (H460 and HeLa) cell lines could not only answer our opening question but also suggest a rather complex response. Our findings indicate the great potential of the obtained AuNP colloids as a part of cancer therapy.

DOI： 10.1021/acsanm.9b02106

Nitriding an oxygen-doped nanocarbonaceous sorbent synthesized via solution plasma process for improving CO<inf>2</inf> adsorption capacity

Pornaroontham P., Panomsuwan G., Chae S., Saito N., Thouchprasitchai N., Phongboonchoo Y., Pongstabodee S.

Nanomaterials Vol. 9 ( 12 ) 2019.12

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

The synthesis of carbon nanoparticles (Cn) and oxygen-doped nanocarbon (OCn) was successfully done through a one-step synthesis by the solution plasma process (SPP). The Cn and OCn were nitrogen-doped by nitridation under an ammonia atmosphere at 800◦C for 2 h to yield NCn and NOCn, respectively, for carbon dioxide (CO2) adsorption. The NOCn exhibited the highest specific surface area (~570 m2 g−1) and highest CO2 adsorption capacity (1.63 mmol g−1 at 25◦C) among the synthesized samples. The primary nitrogen species on the surface of NOCn were pyridinic-N and pyrrolic-N. The synergistic effect of microporosity and nitrogen functionality on the NOCn surface played an essential role in CO2 adsorption enhancement. From the thermodynamic viewpoint, the CO2 adsorption on NOCn was physisorption, exothermic, and spontaneous. The NOCn showed a more negative enthalpy of adsorption, indicating its stronger interaction for CO2 on the surface, and hence, the higher adsorption capacity. The CO2 adsorption on NOCn over the whole pressure range at 25–55◦C best fitted the Toth model, suggesting monolayer adsorption on the heterogeneous surface. In addition, NOCn expressed a higher selective CO2 adsorption than Cn and so was a good candidate for multicycle adsorption.

DOI： 10.3390/nano9121776

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