Microscopic and Spectroscopic Analyses of Pt-Decorated Carbon Nanowires Formed on Carbon Fiber Paper

Jeong, Namjo,Jang, Cheol-yong,Kim, Heeyeon,Jeong, Hakgeun,Yeo, Jeong-gu,Park, Yun Chang,Hwang, Kyo Sik Cambridge University Press 2013 Microscopy and microanalysis Vol.19 No.5

<B>Abstract</B><P>We report the synthesis of carbon nanowires (CNWs) via chemical vapor deposition using catalytic decomposition of ethanol on nanosized transition metals such as Co, Fe, and Ni. Dip-coating process was used for the formation of catalytic nanoparticles, inducing the growth of CNWs on the surface of the carbon fiber paper (CFP). The liquid ethanol used as carbon source was atomized by an ultrasonic atomizer and subsequently flowed into the reactor that was heated up to a synthesis temperature of 600-700°C. Microscopic images show that CNWs of <50 nm were densely synthesized on the surface of the CFP. Raman spectra reveal that a higher synthesis temperature leads to the growth of higher crystalline CNWs. In addition, we demonstrate the successful decoration of platinum nanoparticles on the surface of the prepared CNWs/CFP using the electrochemical deposition technique.</P>

Single-Crystal Apatite Nanowires Sheathed in Graphitic Shells: Synthesis, Characterization, and Application

Jeong, Namjo,Cha, Misun,Park, Yun Chang,Lee, Kyung Mee,Lee, Jae Hyup,Park, Byong Chon,Lee, Junghoon American Chemical Society 2013 ACS NANO Vol.7 No.7

<P>Vertically aligned one-dimensional hybrid structures, which are composed of apatite and graphitic structures, can be beneficial for orthopedic applications. However, they are difficult to generate using the current method. Here, we report the first synthesis of a single-crystal apatite nanowire encapsulated in graphitic shells by a one-step chemical vapor deposition. Incipient nucleation of apatite and its subsequent transformation to an oriented crystal are directed by derived gaseous phosphorine. Longitudinal growth of the oriented apatite crystal is achieved by a vapor–solid growth mechanism, whereas lateral growth is suppressed by the graphitic layers formed through arrangement of the derived aromatic hydrocarbon molecules. We show that this unusual combination of the apatite crystal and the graphitic shells can lead to an excellent osteogenic differentiation and bony fusion through a programmed smart behavior. For instance, the graphitic shells are degraded after the initial cell growth promoted by the graphitic nanostructures, and the cells continue proliferation on the bare apatite nanowires. Furthermore, a bending experiment indicates that such core–shell nanowires exhibited a superior bending stiffness compared to single-crystal apatite nanowires without graphitic shells. The results suggest a new strategy and direction for bone grafting materials with a highly controllable morphology and material conditions that can best stimulate bone cell differentiation and growth.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-7/nn305767t/production/images/medium/nn-2012-05767t_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn305767t'>ACS Electronic Supporting Info</A></P>

Selective synthesis and superconductivity of In–Sn intermetallic nanowires sheathed in carbon nanotubes

Jeong, Namjo,Yeo, Jeong-gu IOP Pub 2012 Nanotechnology Vol.23 No.28

<P>We demonstrate a simple and reproducible technique to synthesize crystalline and superconducting In–Sn intermetallic nanowires sheathed in carbon nanotubes (CNTs). The method is based on the catalytic reaction of C<SUB>2</SUB>H<SUB>2</SUB> over a mixture of both SnO<SUB>2</SUB> and In<SUB>2</SUB>O<SUB>3</SUB> particles. Importantly, tetragonal &bgr;-In<SUB>3</SUB>Sn and hexagonal &ggr;-InSn<SUB>4</SUB> nanowires with diameters of less than 100 nm are selectively synthesized at different SnO<SUB>2</SUB> to In<SUB>2</SUB>O<SUB>3</SUB> weight ratios. CNTs may serve as cylindrical nanocontainers for continuous growth of liquid-phased In<SUB>1−x</SUB>Sn<SUB>x</SUB> nanowires during growth process as well as for their solidification into In–Sn intermetallic nanowires during the cooling process. Microscopic and spectroscopic analyses clearly reveal evidence of a core–shell structure of the CNT-sheathed In–Sn intermetallic nanowires. Magnetization measurements show that the superconducting In–Sn nanowires have a critical magnetic field higher than the value of their bulk intermetallic compounds. Our method can be adopted to the nanofabrication of analogous binary and ternary alloys. </P>

Direct synthesis of carbon nanofilaments on mcroscopic metal substrates and their anti-corrosion applications

Namjo Jeong(정남조),Eunjin Jwa(좌은진),Chansoo Kim(김찬수),Sooncheol Park(박순철),Moonseog Jang(장문석) 한국신재생에너지학회 2016 한국신재생에너지학회 학술대회논문집 Vol.2016 No.5

Effect of Graphitic Layers Encapsulating Single-Crystal Apatite Nanowire on the Osteogenesis of Human Mesenchymal Stem Cells

Jeong, Namjo,Park, Yun Chang,Lee, Kyung Mee,Lee, Jae Hyup,Cha, Misun American Chemical Society 2014 The Journal of physical chemistry B Vol.118 No.48

<P>An ideally designed scaffold for tissue engineering must be able to provide an environment that recapitulates the physiological conditions to control stem cell function. Here, we compared vertically aligned single-crystal apatite nanowires sheathed in graphitic layers (SANGs) with single-crystal apatite nanowires (SANs), which had the same geometric properties asbut differing nanotopographic surface chemistry thanSANGs, in order to evaluate the effect of the graphitic layer on the behavior of human mesenchymal stem cells (hMSCs). The difference in nanotopographic surface chemistry did not affect hMSC adhesion, growth, or morphology. However, hMSCs were more effectively differentiated into bone cells on SANGs through interaction with graphitic layers, which later degraded and thereby allowed the cells to continue differentiation on the bare apatite nanowires. Thus, SANGs provide an excellent microenvironment for the osteogenic differentiation of hMCS.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2014/jpcbfk.2014.118.issue-48/jp5075576/production/images/medium/jp-2014-075576_0012.gif'></P>

High-yield growth of carbon nanofilaments on nickel foam using nickel-tin intermetallic catalysts.

Jeong, Namjo,Hwang, Kyo Sik,Yang, Seung Cheol American Scientific Publishers 2014 Journal of nanoscience and nanotechnology Vol.14 No.10

<P>The integration of nanomaterials into macroscopic structures is of importance to their practical use. We report the direct synthesis of carbon nanofilaments on Ni foam using Ni-Sn intermetallic nanoparticles. The use of SnO2 nanoparticles was highly effective for the high-yield growth of carbon nanofilaments without the occurrence of surface breakup, resulting from excessive carbon accumulation in the Ni foam. Carbon nanofilaments with a diameter of 50 nm were synthesized and contained Ni3Sn nanoparticles at the tip, indicating a tip-growth mechanism. Higher vacuum conditions led to the growth of highly crystalline carbon nanofilaments. The results obtained using different sources of hydrocarbon revealed that in contrast to C2H2, CH4 or C3H8 did not induce carbon nanofilament formation on Ni foam.</P>

Direct Growth of Graphitic Carbon-Encapsulating Carbonate Apatite Nanowires from Calcium Carbonate

Jeong, Namjo,Park, Soon-Chul,Jang, Moon Seok,Kim, Sung-in The American Chemical Society 2018 CRYSTAL GROWTH AND DESIGN Vol.18 No.9

<P>We report the direct chemical vapor deposition of graphitic carbon-encapsulating carbonate apatite nanowires (GCECANs)/hexagonal portlandite-phased Ca(OH)<SUB>2</SUB> hybrid structures from CaCO<SUB>3</SUB> powder at 900 °C. The formation mechanism of the GCECANs is investigated in detail through a structural and morphological characterization of the final products. Spectroscopic analyses elucidate the effect of H<SUB>2</SUB> concentration in the reactor on the transformation of the calcite-phased CaCO<SUB>3</SUB> into vaterite-phased CaCO<SUB>3</SUB> and subsequently portlandite-phased Ca(OH)<SUB>2</SUB>. The results show that GCECANs are formed on the surface of the derived Ca(OH)<SUB>2</SUB>. It is especially remarkable that a higher H<SUB>2</SUB> concentration results in the precipitated growth of such hybrid structures. Microscopic images show that GCECANs 20 nm in diameter grew up to 3 μm in length along the direction corresponding to the [001] plane of the hexagonal apatite crystal. In addition, the electrical properties of the GCECANs are measured by using an electrode with 150 nm gap.</P><P>An approach is suggested to transform calcite-phased CaCO<SUB>3</SUB> into graphitic carbon-encapsulating carbonate apatite nanowires/hexagonal portlandite-phased Ca(OH)<SUB>2</SUB> hybrid structures using a chemical vapor deposition-based vapor−solid growth mechanism. An increase of H<SUB>2</SUB> concentration in the reactor accelerated the formation of such hybrid structures. Also, the vaterite phase was formed as an intermediate product during the transformation. The hexagonal apatite nanowires approximately 20 nm in diameter grew up to 3 μm in length along the [001] plane.</P> [FIG OMISSION]</BR>

Direct growth, characterization, and optical properties of silica nanowires on cordierite monolith

Jeong, Namjo,Kim, Chan-soo,Hong, Sung-kook,Park, Soon-chul,Jang, Moon-seok Elsevier Science B.V., Amsterdam. 2016 Ceramics international Vol.42 No.-

Uniform coating of molybdenum disulfide over porous carbon substrates and its electrochemical application

Jeong, Namjo,Kim, Han-ki,Kim, Won-sik,Choi, Ji Yeon,Han, Ji-hyung,Nam, Joo-youn,Hwang, Kyo Sik,Yang, SeungCheol,Jwa, Eun-Jin,Kim, Tae-Young,Park, Soon-Chul,Seo, Yong-Seog,Kim, Sung-in Elsevier 2019 Chemical engineering journal Vol.356 No.-

<P><B>Abstract</B></P> <P>The direct integration of two-dimensional nanostructures into macroscopic porous carbon substrates is essential for their practical use in potential applications, which is a big challenge due to the difficulty of securing uniform coating layers. In this work, we demonstrate a very simple and effective method for the direct coating of MoS<SUB>2</SUB> onto the surface of porous carbon structures having nano-sized pores, such as vertically aligned carbon nanotube arrays. A uniform coverage of MoS<SUB>2</SUB> over carbon substrates was achieved by chemical vapor deposition of gaseous species derived from starting precursors in a closed reactor. Transmission electron microscopy images, X-ray diffraction data, and Raman spectra confirmed the formation of highly crystalline MoS<SUB>2</SUB> layers. X-ray photoelectron and energy dispersive X-ray spectroscopies revealed highly uniform MoS<SUB>2</SUB> layers over the whole surface of the carbon substrates. Our approach is also applicable for the synthesis of MoS<SUB>2</SUB>/carbon fiber paper (CFP) hybrid structures. The electrochemical tests showed that the as-synthesized MoS<SUB>2</SUB>/CFP structures can serve as highly active cathodes for reverse electrodialysis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoS<SUB>2</SUB>@VCNT and MoS<SUB>2</SUB>@CFP were prepared in this work. </LI> <LI> Uniform MoS<SUB>2</SUB> coating was achieved by CVD of gaseous species in the closed reactor. </LI> <LI> This approach is very powerful for MoS<SUB>2</SUB> coating over macroscopic porous substrates. </LI> <LI> MoS<SUB>2</SUB>/CFP can be a highly active cathode for reverse electrodialysis. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Direct synthesis of carbon nanotubes using Cu-Sn catalyst on Cu substrates and their corrosion behavior in 0.6M NaCl solution

Jeong, Namjo,Jwa, Eunjin,Kim, Chansoo,Choi, Ji Yeon,Nam, Joo-youn,Park, Soon-chul,Jang, Moon-seok Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.423 No.-

<P><B>Abstract</B></P> <P>We report the high-yield and large-area synthesis of a spaghetti-like carbon nanotubes (CNTs) on macroscopic Cu substrates (foil and foam) using a Cu-Sn alloy catalyst. In addition, we investigate the corrosion properties of the as-synthesized CNT/Cu foil system in 0.6M NaCl solution. Electrochemical analysis showed that the corrosion resistance of the CNT/Cu foil system improved by a factor of ∼100 compared to the as-received Cu foil. Thus, it is concluded that a dense network of CNT was uniformly coated on the Cu foil and this coating functioned as an efficient barrier to corrosion under simulated seawater conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High-yield and large-area synthesis of CNTs on Cu substrates such as foil and foam. </LI> <LI> The tip growth mechanism by CCVD governed the overall growth using Cu-Sn catalysts. </LI> <LI> Our approach can be extended to high-yield growth of CNTs over various substrates. </LI> <LI> Corrosion resistance of CNT/Cu was improved a hundred times than as-received Cu. </LI> <LI> Change in surface morphology after corrosion test induced reduced hydrophobicity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>