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Tomohiro Tojo,Cheon Soo Kang,Takuya Hayashi,Yoong Ahm Kim 한국탄소학회 2018 Carbon Letters Vol.28 No.-
Linear carbon chains (LCCs) encapsulated inside the hollow cores of carbon nanotubes (CNTs) have been experimentally synthesized and structurally characterized by Raman spectroscopy and transmission electron microscopy. However, in terms of electronic conductivity, their transportation mechanism has not been investigated theoretically or experimentally. In this study, the density of states and quantum conductance spectra were simulated through density functional theory combined with the non-equilibrium Green function method. The encapsulated LCCs inside (5,5), (6,4), and (9,0) single-walled carbon nanotubes (SWCNTs) exhibited a drastic change from metallic to semiconducting or from semiconducting to metallic due to the strong charge transfer between them. On the other hand, the electronic change in the conductance value of LCCs encapsulated inside the (7,4) SWCNT were in good agreement with the superposition of the individual SWCNTs and the isolated LCCs owing to the weak charge transfer.
Kang, Hungu,Ito, Eisuke,Hayashi, Tomohiro,Hara, Masahiko,Noh, Jaegeun American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.6
<P>The surface structures of self-assembled monolayers (SAMs) formed by the adsorption of pentachlorobenzenethiol (PCBT) molecules on Au(111) as a function of solution concentration were examined by means of scanning tunneling microscopy (STM) to understand the effect of concentration on the formation of ordered domains. STM imaging revealed that PCBT SAMs formed in a 0.01 or 1 mM ethanol solution at room temperature for 20 min contained small ordered domains in the range of several to 20 nm(2) and disordered phases, while PCBT SAMs formed in a 0.1 mM ethanol solution were composed of long-range ordered domains in the range of 20 to 50 nm(2), which can be assigned as a (4 x root 3) R45 degrees packing structure. Interestingly, the bright aggregated domains stacked by pi-pi interactions between PCBT rings were usually observed around boundary regions of ordered domains. In addition, X-ray photoelectron spectroscopy measurements revealed that ordered PCBT SAMs on Au(111) were formed via the chemical interactions between the sulfur atom of PCBT and gold surface. Our results obtained here will be very useful in understanding the formation and structure of PCBT SAMs on gold surfaces.</P>
Kim, Youngwoo,Kang, Hungu,Tsunoi, Azuho,Hayashi, Tomohiro,Hara, Masahiko,Noh, Jaegeun American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.3
<P>The formation and surface structure of 3-hexylthiophene (HTP) self-assembled monolayers (SAMs) on Au(111) prepared by solution and ambient-pressure vapor deposition at room temperature (RT) for 24 h were examined by means of scanning tunneling microscopy (STM) and cyclic voltammetry (CV). STM imaging revealed that HTP SAMs formed by solution deposition have a disordered phase, whereas those formed by vapor deposition exhibit a striped phase with a unidirectional orientation. The distance between the rows in the striped phase was measured to be 1.3 +/- 0.1 nm, and the hexyl molecular backbones of HTP in the SAMs on Au(111) are oriented parallel to the Au(111) surface with the head-to-head orientation. From this STM observation, we suggest that the formation of this striped phase in HTP SAMs prepared by vapor deposition were mainly driven by the optimization of van der Waals interactions between the hexyl chains on the surface. CV measurements also demonstrated that HTP SAMs show a high blocking efficiency for electron transfer reactions between electrolytes and the gold electrode, suggesting the formation of SAMs on Au(111) from the vapor phase. Our results obtained here will be very useful for understanding the formation and structure of HTP SAMs on Au(111) surfaces and how they are influenced by deposition method.</P>
Formation and Structure of Self-Assembled Monolayers by Adsorption of Octaneselenocyanate on Au(111)
Han, Seulki,Kang, Hungu,Park, Joon B.,Hayashi, Tomohiro,Hara, Masahiko,Noh, Jaegeun American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.8
<P>The formation and surface structure of self-assembledmonolayers (SAMs) on Au(111) by adsorption of octaneselenocyanate (C8Se-CN) in a 1 mM ethanol solution were examined by scanning tunneling microscopy (STM) and cyclic voltammetry (CV). STM imaging reveals that octaneselenolate (C8Se) SAMs formed at room temperature were mainly composed of disordered phase containing many vacancy islands, whereas well-ordered C8Se SAMs with a row structure were formed at high solution temperature of 50 or 75 degrees C. Spacing between the rows was measured to be 1.7 +/- 0.2 nm, and molecular spacing in the row was measured to be 0.5 +/- 0.1 nm. From this work, we clearly demonstrated that C8Se-CN molecules on Au(111) at high solution temperature led to the formation of ordered C8Se SAMs after bond cleavage of C8Se-CN. Our results will provide new insight into understanding the formation and structure of SAMs by the adsorption of C8Se-CN molecules on Au(111) surface.</P>
Unilateral rostral mandibulectomy for gingival vascular hamartoma in two calves
Takeshi Tsuka,Yoshiharu Okamoto,Naoki Yamamoto,Keiji Hayashi,Takehito Morita,Yuji Sunden,Yusuke Murahata,Kazuo Azuma,Tomohiro Osaki,Norihiko Ito,Tomohiro Imagawa 대한수의학회 2018 Journal of Veterinary Science Vol.19 No.4
A 2-month-old female Holstein calf and a 5-month-old female Japanese black calf presented with gingival vascular hamartoma located in the interdental space between the second and third mandibular incisors in the right and left mandibles, respectively. On radiographic or computed tomographic images, osteolytic changes appeared within the mandibular bones adjacent to the masses. The masses were removed along with affected mandibular bone by using unilateral rostral mandibulectomy. After surgery, both cases exhibited a normal appetite and grew normally, with no cosmetic changes or recurrences. Unilateral rostral mandibulectomy can be applied for invasive gingival vascular hamartomas associated with osteolytic changes.
Ito, Eisuke,Ito, Hiromi,Kang, Hungu,Hayashi, Tomohiro,Hara, Masahiko,Noh, Jaegeun American Chemical Society 2012 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.116 No.33
<P>The formation and thermal desorption behaviors of octanethiol (OT) SAMs on single crystalline Au(111) and polycrystalline Au, Ag, and Cu substrates were examined by X-ray photoelectron microscopy (XPS), thermal desorption spectroscopy (TDS), and contact angle (CA) measurements. XPS and CA measurements revealed that the adsorption of OT molecules on these metals led to the formation of chemisorbed self-assembled monolayers (SAMs). Three main desorption fragments for dioctyl disulfide (C8SSC8<SUP>+</SUP>, dimer), octanethiolate (C8S<SUP>+</SUP>), and octanethiol (C8SH<SUP>+</SUP>) were monitored using TDS to understand the effects of surface morphology and the nature of metal substrates on the thermal desorption behavior of alkanethiols. TDS measurements showed that a sharp dimer peak with a very strong intensity on single crystalline Au(111) surface was dominantly observed at 370 K, whereas a broad peak on the polycrystalline Au surface was observed at 405 K. On the other hand, desorption behaviors of octanethiolates and octanethiols were quite similar. We concluded that substrate morphology strongly affects the dimerization process of alkanethiolates on Au surfaces. We also found that desorption intensity of the dimer is in the order of Au ≫ Ag > Cu, suggesting that the dimerization process occurs efficiently when the sulfur–metal bond has a more covalent character (Au) rather than an ionic character (Ag and Cu). The relative desorption intensity of the octanethiolates to the octanethiols follows the order of bond strength, Cu > Au > Ag. Alkanethiolates may be a dominant desorption product as metal–sulfur bonds become stronger. In this study, we clearly demonstrate that the thermal stability and desorption behaviors of alkanethiol SAMs are strongly influenced by the surface morphologies of metal substrates, bonding character of the sulfurs, the bond strength of metal–sulfur, and van der Waals interactions. Our results provide new insights into understanding the thermal stability and desorption behaviors of alkanethiols on Au, Ag, and Cu surfaces.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-33/jp3041204/production/images/medium/jp-2012-041204_0008.gif'></P>
Jeong, Hyerim,Kang, Hungu,Han, Seulki,Park, Heegun,Han, Jinwook,Hayashi, Tomohiro,Hara, Masahiko,Noh, Jaegeun American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.8
<P>To compare the adsorption affinity of S-Au and Se-Au in self-assembled monolayers (SAMs), we examined displacement behaviors of pre-covered cyclohexanethiolate (CHS) and cyclohexaneselenolate (CHSe) SAMs on Au(111) by octanethiol (OT) for 20 min using scanning tunneling microscopy (STM) and cyclic voltammetry (CV) measurements. Molecular-scale STM observation revealed that the surface structure of CHS SAMs with a (5x2 root 3)R35 degrees packing structure on Au(111) was totally changed to a linear molecular row structure after displacement for 20 min, whereas the surface structure of CHSe SAMs with a (2x2 root 10)R27 degrees structure was almost not changed. This STM result are also good consistent with CV result showing reductive desorption behaviors. From STM and CV results, we consider that the strength of Se-Au bond in the SAMs is much stronger than that of S-Au bond.</P>