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Journal Articles

In situ transmission electron microscopy observation of melted germanium encapsulated in multilayer graphene

Suzuki, Seiya; Nemoto, Yoshihiro*; Shiiki, Natsumi*; Nakayama, Yoshiko*; Takeguchi, Masaki*

Annalen der Physik, 535(9), p.2300122_1 - 2300122_12, 2023/09

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

New material exploration to enhance neutron intensity below cold neutrons; Nanosized graphene flower aggregation

Teshigawara, Makoto; Ikeda, Yujiro*; Yan, M.*; Muramatsu, Kazuo*; Sutani, Koichi*; Fukuzumi, Masafumi*; Noda, Yohei*; Koizumi, Satoshi*; Saruta, Koichi; Otake, Yoshie*

Nanomaterials (Internet), 13(1), p.76_1 - 76_9, 2023/01

 Times Cited Count:0 Percentile:64.13(Chemistry, Multidisciplinary)

To enhance neutron intensity below cold neutrons, it is proposed that nanosized graphene aggregation could facilitate neutron coherent scattering under particle size conditions similar to nanodiamond. It might also be possible to use it in high neutron radiation conditions due to graphene's strong sp2 bonds. Using the RIKEN accelerator-driven compact neutron source and iMATERIA at J-PARC, we performed neutron measurement experiments, total neutron cross-section, and small-angle neutron scattering on nanosized graphene aggregation. The measured data revealed, for the first time, that nanosized graphene aggregation increased the total cross-sections and small-angle scattering in the cold neutron energy region, most likely due to coherent scattering, resulting in higher neutron intensities, similar to nanodiamond.

Journal Articles

Chloramphenicol removal from water by various precursors to enhance graphene oxide-iron nanocomposites

Idham, M. F.*; Falyouna, O.*; Eljamal, R.*; Maamoun, I.; Eljamal, O.*

Journal of Water Process Engineering (Internet), 50, p.103289_1 - 103289_16, 2022/12

 Times Cited Count:7 Percentile:90.93(Engineering, Environmental)

Journal Articles

Possible oxygen reduction reactions for graphene edges from first principles

Ikeda, Takashi; Hou, Z.*; Chai, G.-L.*; Terakura, Kiyoyuki*

Journal of Physical Chemistry C, 118(31), p.17616 - 17625, 2014/08

 Times Cited Count:48 Percentile:80.64(Chemistry, Physical)

N-doped carbon-based nanomaterials are attracting a great interest as promising Pt-free electrode catalysts for polymer electrolyte fuel cells (PEFCs). In this computational study, we demonstrate that N-doped graphene edges can exhibit enhanced catalytic activity toward oxygen reduction reactions by controlling their electron-donating and -withdrawing abilities, and basicity, resulting in higher selectivity of 4e$$^{-}$$ reduction via inner and outer sphere electron transfer at edges in acidic conditions, respectively. Our simulations also show that 2e$$^{-}$$ reduction occurs selectively in the presence of pyridinic N next to carbonyl O at zigzag edges. This study thus rationalizes the roles of doped N in graphenelike materials for oxygen reduction reactions.

Journal Articles

Interplay between oxidized monovacancy and nitrogen doping in graphene

Hou, Z.*; Shu, D.-J.*; Chai, G.-L.*; Ikeda, Takashi; Terakura, Kiyoyuki*

Journal of Physical Chemistry C, 118(34), p.19795 - 19805, 2014/08

 Times Cited Count:11 Percentile:36.14(Chemistry, Physical)

In most of the N-doped graphene which attracts strong attention in the context of precious-metal free catalysts and nanoelectronics, the oxygen content is generally higher than or at least comparable to the nitrogen content. We perform density functional theory calculations to study the interplay of oxidized monovacancies and the nitrogen doping, motivated by the fact that MV is more frequently observed and more chemically active than divacancy and Stone-Wales defect. We determine the phase diagrams of un-doped and nitrogen-doped oxidized MVs as a function of temperature and partial pressure of O$$_{2}$$ and H$$_{2}$$ gases. The modification of the electronic structure of MV by oxidation and N doping is studied. Our results show that the ether group is a common component in stable configurations of oxidized MVs. Most of the stable configurations of oxidized MVs do not induce any carriers.

Journal Articles

NMR chemical shifts of $$^{15}$$N-bearing graphene

Wang, X.*; Hou, Z.*; Ikeda, Takashi; Terakura, Kiyoyuki*

Journal of Physical Chemistry C, 118(25), p.13929 - 13935, 2014/06

 Times Cited Count:10 Percentile:33.54(Chemistry, Physical)

The NMR chemical shifts of possible N-containing moieties at edges and defects of graphene are investigated by using the first-principles method. Our computations show that pyridine-like and graphite-like N are rather easily identifiable using $$^{15}$$N NMR technique, in agreement with experiment. On the other hand, pyridinium-like N is hardly distinguished from pyrrole-like one because these $$^{15}$$N nuclei give nearly overlapping signals. However, our simulations suggest that $$^{1}$$H NMR is useful to discriminate between them; The NMR chemical shift of $$^{1}$$H directly bonded with pyridinium-like and pyrrole-like N is estimated as 0.8 and 10.8 ppm, respectively. The $$^{15}$$N NMR signals for various moieties at edges we considered are found to be similar to the corresponding ones at defects except for pyridine-like nitrogens. Conversely, the $$^{15}$$N NMR chemical shifts are altered sensitively by the degree of aggregation of pyridine-like $$^{15}$$N atoms both along armchair edges and at defect sites.

Oral presentation

Growth mechanism of graphene on Cu(111) substrates studied by in-situ photoelectron spectroscopy

Ogawa, Shuichi*; Yamada, Takatoshi*; Ishizuka, Shinji*; Yoshigoe, Akitaka; Hasegawa, Masataka*; Teraoka, Yuden; Takakuwa, Yuji*

no journal, , 

Oral presentation

Graphene nanoribbon growth on Au(100)

Yano, Masahiro; Asaoka, Hidehito

no journal, , 

Graphene nanoribbons that were bottom-up synthesized from self-assembled precursor monolayers on Au(100) and Au(111) were observed by using a scanning tunneling microscope (STM). It was revealed that the molecular orientation of the self-assembled monolayers decides the orientation direction of the graphene nanoribbons. In particular, the orientation direction of the graphene nanoribbons coincides with the one-dimensional uneven of the surface reconstruction structure on Au(100). It means that the controllability of graphene nanoribbon orientation on Au(100) is higher than that of Au(111). This is an important finding for the device application of graphene nanoribbons.

Oral presentation

Graphene nanoribbon synthesis from well-ordered DBBA monolayer

Yano, Masahiro; Yasuda, Satoshi; Asaoka, Hidehito

no journal, , 

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