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Journal Articles

Carbonated nanohydroxyapatite from bone waste and its potential as a super adsorbent for removal of toxic ions

Sekine, Yurina; Nankawa, Takuya; Yamada, Teppei*; Matsumura, Daiju; Nemoto, Yoshihiro*; Takeguchi, Masaki*; Sugita, Tsuyoshi; Shimoyama, Iwao; Kozai, Naofumi; Morooka, Satoshi

Journal of Environmental Chemical Engineering, 9(2), p.105114_1 - 105114_12, 2021/04

 Times Cited Count:0 Percentile:0(Engineering, Environmental)

Remediating toxic ion contamination is crucial for protecting human health and the environment. This study aimed to provide a powerful strategy for effectively utilizing bone waste from the food production and preparation industries for removal of toxic ions. Here, we show that immersing pig bone in NaHCO$$_{3}$$ solution produced a carbonated nanohydroxyapatites (C-NHAP). The C-NHAP exhibited high adsorptivity for Sr$$^{2+}$$, Cd$$^{2+}$$, Pb$$^{2+}$$, and Cu$$^{2+}$$. The strontium adsorptivity was about 250 and 4,500 times higher than that of normal bone and synthetic HAP, respectively. The C-NHAP is an eco-friendly, high-performance material that is simple to prepare and should be useful for tackling problems of food waste disposal and environmental pollution.

Journal Articles

Eco-friendly carboxymethyl cellulose nanofiber hydrogels prepared via freeze cross-linking and their applications

Sekine, Yurina; Nankawa, Takuya; Yunoki, Shunji*; Sugita, Tsuyoshi; Nakagawa, Hiroshi; Yamada, Teppei*

ACS Applied Polymer Materials (Internet), 2(12), p.5482 - 5491, 2020/12

We developed a cross-linking method using freeze concentration and used it to synthesize a new type of carboxymethyl cellulose nanofiber (CMCF) hydrogel with high compressive strength ($$>$$ 80 MPa) and high compressive recoverability. The hydrogels were prepared by adding an aqueous solution of citric acid (CA) to a frozen CMCF sol and then thawing the sol. The reaction between the freeze-concentrated CMCF and CA created a rigid porous structure that reflected the ice crystal structure. Their cross-linked structure has a high stability to compressive stress. Bentonite was immobilized on a CMCF hydrogel by adding bentonite to the CMCF sol before freeze cross-linking. The CMCF-bentonite hydrogel showed high adsorptivity for chemical dyes. The physically cross-linked CMCF hydrogels are non-toxic, metal-free, and simple to prepare, and thus they may be useful as sustainable materials in various fields.

Journal Articles

Crossover from coherent quasiparticles to incoherent hole carriers in underdoped cuprates

Hashimoto, Makoto*; Yoshida, Teppei*; Tanaka, Kiyohisa*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*

Physical Review B, 79(14), p.140502_1 - 140502_4, 2009/04

 Times Cited Count:13 Percentile:52.72(Materials Science, Multidisciplinary)

Journal Articles

Relationship between the superconducting gap and the pseudogap; Temperature-dependent photoemission study of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ and La$$_{2}$$CuO$$_{4.10}$$

Hashimoto, Makoto*; Tanaka, Kiyohisa*; Yoshida, Teppei*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*

Physica C, 460-462(2), p.884 - 885, 2007/09

 Times Cited Count:3 Percentile:18.97(Physics, Applied)

In the high-${it T$_{rm c}$}$ research, relationship between the pseudogap and the superconducting gap has been an important issue. We have performed a detailed temperature-dependent angle-integrated photoemission study of lightly-doped to heavily-overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ and oxygen-doped La$$_{2}$$CuO$$_{4.10}$$. We found that, while the magnitude of the pseudogap increased with decreasing doping, that of the superconducting gap did not increase. This behavior can be explained if the superconducting gap opens only on the Fermi arc around the node (0,0)-($$pi$$,$$pi$$) whereas the pseudogap opens primarily around ($$pi$$,0).

Journal Articles

Distinct doping dependences of the pseudogap and superconducting gap of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ cuprate superconductors

Hashimoto, Makoto*; Yoshida, Teppei*; Tanaka, Kiyohisa*; Fujimori, Atsushi*; Okusawa, Makoto*; Wakimoto, Shuichi; Yamada, Kazuyoshi*; Kakeshita, Teruhisa*; Eisaki, Hiroshi*; Uchida, Shinichi*

Physical Review B, 75(14), p.140503_1 - 140503_4, 2007/04

 Times Cited Count:64 Percentile:89.48(Materials Science, Multidisciplinary)

We have performed a temperature-dependent angle-integrated photoemission study of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ covering from lightly doped to heavily overdoped regions and oxygen -doped La$$_{2}$$CuO$$_{4.10}$$. The superconducting gap energy $$Delta_{sc}$$ was found to remain small for decreasing hole concentration while the pseudogap energy $$Delta^{*}$$ and temperature $$T^{*}$$ increase. The different behaviors of the superconducting gap and the pseudogap can be explained if the superconducting gap opens only on the Fermi arc around the nodal (0,0)-$$(pi,pi)$$ direction while the pseudogap opens around $$sim (pi,0)$$. The results suggest that the pseudogap and the superconducting gap have different microscopic origins.

Journal Articles

Photoluminescent dinuclear lanthanide complexes with Tris(2-pyridyl)carbinol acting as a new tetradentate bridging ligand

Watanabe, Masayuki; Nankawa, Takuya*; Yamada, Teppei*; Kimura, Takaumi; Namiki, Kosuke*; Murata, Masaki*; Nishihara, Hiroshi*; Tachimori, Shoichi

Inorganic Chemistry, 42(22), p.6977 - 6979, 2003/11

 Times Cited Count:33 Percentile:75.93(Chemistry, Inorganic & Nuclear)

A tripodal ligand, tris(2-pyridyl)carbinol affords a novel tetradentate coordination mode in homodinuclear lanthanide complexes, which exhibit remarkably short distance between the metal ions. Strong fluorescence of Eu(III) and Tb(III) complexes with the ligand demonstrate that the ligand has a suitable excited state for energy transfer from the ligand to Eu(III) and Tb(III) center.

Oral presentation

Separation and recovery of radioactive cesium and strontium by metal-organic-frameworks

Nankawa, Takuya; Ogoshi, Yurie; Kuwahara, Akira; Yamada, Teppei*; Zanella, M.*; Jansat, S.*; Manning, T.*; Rosseinsky, M.*

no journal, , 

Radioactive Cesium(Cs) and Strontium(Sr) in liquid waste can be separated by porous materials such as zeolite. The pore sizes of these materials seems to identify metal ion radius or hydrated ion radius of Cs or Sr. But since it is very difficult to change the pore sizes of these materials, we cannot investigate the relationship between the pore sizes and Cs or Sr uptake behavior of these materials. And since the frameworks of these materials are rigid, it is very hard to recover Cs or Sr absorbed in the materials and we have to dispose Cs or Sr containing material as nuclear waste. But if Cs and Sr can be recovered from the materials, we can make use of these radioactive nuclides as radiation or heat source. On the other hand, metal-organic-frameworks (MOF) have attracted much interest in this two decades because of its fascinating characters such as gas absorption, catalytic or optical properties. The advantages of MOF over zeolites or other porous materials are a highly-ordered structure composed of metal ions and organic ligands, and highly controllable pore sizes that can be controlled by the length of ligand and ionic radii of metal ions. Moreover, structures of MOF can easily be influenced by solution phase. So, it becomes easy to recover guest ions from MOF. In this study, we synthesized a novel series of MOF, (NH$$_{4}$$)[Ln(C$$_{2}$$O$$_{4}$$)$$_{2}$$(H$$_{2}$$O)]. The structure is shown in Fig.1. All the structures the MOF are isostructural. The cell lengths and pore sizes tend to be decreased with the increase of atomic number in response to the decrease of ionic radius known as lanthanide contraction. And we investigated the behavior of Cs or Sr uptake by changing lanthanide ions in the MOF. Moreover, we found that Cs can be recovered from the MOF and we can reuse the MOF again. According to these results, we found a new material to recover Cs from radioactive liquid waste to decrease the amount of waste and make use of Cs as radiation source.

Oral presentation

Separation and recovery of radioactive ions by metal-organic-frameworks

Nankawa, Takuya; Yamada, Teppei*; Ogoshi, Yurie; Kuwahara, Akira; Alexandros, K.*; David, S.*; Marco, Z.*; Jansat, S.*; Troy, D. M.*; Matthew, J. R.*

no journal, , 

Oral presentation

Development of high-strength cellulose nanofiber hydrogels by freeze-crosslinking

Sekine, Yurina; Nankawa, Takuya; Miura, Daisuke*; Yunoki, Shunji*; Sugita, Tsuyoshi; Nakagawa, Hiroshi; Yamada, Teppei*

no journal, , 

We developed a crosslinking method using freeze concentration and used it to synthesize a cellulose nanofiber hydrogel with high compressive strength. The reaction between the freeze-concentrated cellulose nanofiber and citric acid created a rigid porous structure. Without the freeze crosslinking method, the complex of the cellulose nanofiber sol and citric acid produced hydrogels, which easily collapsed under compressive stress. We will give a presentation on the crosslinking method and the chemical and physical properties of the hydrogel.

Oral presentation

Gelation mechanism of freeze-crosslinked cellulose nanofiber gels with high compressive strength

Miura, Daisuke; Nankawa, Takuya; Yamada, Teppei*; Sekine, Yurina

no journal, , 

We developed a crosslinking method using freeze concentration and used it to synthesize a carboxymethyl cellulose nanofiber (CMCF) hydrogel with high compressive strength and high formability. The reaction between freeze-concentrated CMCF and organic acids created a rigid porous structure. In this study, we found that the structure of the freeze-concentrated CMCF could be fixed by organic acids in presence of ice, and the fixed structure contributed the mechanical properties of the hydrogel. We will give a presentation on the gelation mechanism of the CMCF hydrogel.

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