Author: Hiroyuki Muramatsu

An anticorrosive magnesium/carbon nanotube composite

Hiroyuki Muramatsu MAURICIO TERRONES MALDONADO (2008)

"Here, we report a drastically improved anticorrosive characteristic of magnesium alloy composites with the introduction of multiwalled carbon nanotubes. Highly depressed corrosion of nanotube-filled magnesium composite in salt water is due to the formation of stable oxide films along the grain boundaries of magnesium. Our results indicate that carbon nanotube acted as effective multifunctional filler to improve both mechanical and anticorrosive performances of magnesium alloy."

Article

Carbon Fibers CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA

Strong and stable photoluminescence from the semiconducting inner tubes within double walled carbon nanotubes

Hiroyuki Muramatsu MAURICIO TERRONES MALDONADO Dresselhaus Mildred (2009)

"We examined the optical features of single wall carbon nanotubes (SWNTs) and the inner tubes within double walled carbon nanotubes (DWNTs) having the same (n,m) chirality. The brighter and more stable photoluminescence signals as well as the larger absorbance were observed for the semiconducting inner tubes within DWNTs and not for SWNTs. The outer layers of DWNTs maintain the high structural integrity of the inner tubes during both oxidative purification and strong sonication steps and are responsible in increasing the dielectric screening (due to weaker Coulomb interaction); thus leading to a redshift of the E(11)(S) and E(22)(S) excitonic transitions."

Article

Carbon nanotubes Chirality Elemental semiconductors Excitons Photoluminescence; Red shift Semiconductor nanotubes CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA

Diameter-selective separation of double-walled carbon nanotubes

Hiroyuki Muramatsu MAURICIO TERRONES MALDONADO Dresselhaus Mildred (2008)

"Here, we report a simple and effective way of separating double-walled carbon nanotubes as a function of their diameter using individually dispersed nanotube solutions with the aid of long and random single-stranded DNA. The subtle pHpH change in nanotube solutions gives rise to the preferential coagulation of large-diameter tubes and allows the easy preparation of small-diameter tubes. The stronger van der Waals forces between large-diameter tubes, combined with the decreased solubility of DNA in water at low pHpH, lead to the preferential agglomeration of large-diameter tubes."

Article

Carbon nanotubes Disperse systems DNA pH Phase separation Solubility Texture Van der Waals forces CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA

CdSe quantum dot-decorated double walled carbon nanotubes: the effect of chemical moieties

Hiroyuki Muramatsu MAURICIO TERRONES MALDONADO Dresselhaus Mildred (2008)

"We report that fluorine atoms on the outer tubes of double walled carbon nanotubes (DWNTs) are more effective for nucleating and growing CdSe nanoparticles than oxygen-containing functional groups. The CdSe particles with an average size of 5–7 nm grow through infiltration into an interstitial space created by four to five thin bundled DWNTs. We envisage that DWNTs will replace single and multiwalled carbon nanotubes in a wide range of applications because chemical moieties could be introduced selectively on the outer tubes while the optical and physical properties of the inner tubes remain almost unchanged"

Article

Fluorination CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA

Controlled growth of one-dimensional clusters of molybdenum atoms using double-walled carbon nanotube templating

Hiroyuki Muramatsu MAURICIO TERRONES MALDONADO Dresselhaus Mildred (2009)

"We report the controlled growth of one-dimensional clusters of molybdenum atoms inside the inner cores of double-walled carbon nanotubes. A combined characterization including high resolution transmission electron microscopy, nitrogen adsorption measurement at 77 K, x-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis reveals that the growth of one-dimensional Mo clusters can be controlled by varying the reaction conditions. The products have specific surface areas of 360–480 m2 g−1360–480 m2 g−1, and their characteristic properties are attributed to the presence of Mo cluster, which affect the electronic structure and can be exploited for the development of nanotube electronic devices."

Article

Adsorption Carbon nanotubes Chemical reactions Electronic structure Metal clusters Molybdenum Nanotechnology Raman spectra Thermal analysis Transmission electron microscopy X-ray photoelectron spectra CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA

Raman spectroscopy study of heat-treated and boron-doped double wall carbon nanotubes

Georgy Samsonidze Hiroyuki Muramatsu MAURICIO TERRONES MALDONADO Dresselhaus Mildred (2009)

"We performed Raman spectroscopy experiments on undoped and boron-doped double walled carbon nanotubes (DWNTs) that exhibit the "coalescence inducing mode" as these DWNTs are heat treated to temperatures between 1200 C and 2000 C. The fact that boron doping promotes DWNT coalescence at lower temperatures allowed us to study in greater detail the behavior of first- and second-order Raman modes as a function of temperature with regard to the coalescence process. Furthermore, by using various excitation laser energies we probed DWNTs with different metallic (M) and semiconducting (S) inner and outer tubes. We find that regardless of their M and S configurations, the smaller diameter nanotubes disappear at a faster rate than their larger diameter counterparts as the heat treatment temperature is increased. We also observe that the frequency of the G band is mostly determined by the diameter of the semiconducting layer of those DWNTs that are in resonance with the laser excitation energy. Finally, we explain the contributions to the G' band from the inner and outer layers of a DWNT."

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA

Loop formation in graphitic nanoribbon edges using furnace heating or Joule heating

Xiaoting Jia JESSICA ROSAURA CAMPOS DELGADO EDGAR EDUARDO GRACIA ESPINO Mario Hofmann Hiroyuki Muramatsu MAURICIO TERRONES MALDONADO Dresselhaus Mildred (2009)

"Here the authors report the use of either furnace heating or Joule heating to pacify the exposed graphene edges by loop formation in a novel graphitic nanoribbon material, grown by chemical vapor deposition. The edge energy minimization process involves the formation of loops between adjacent graphene layers within the nanoribbons. A comparison is made of the similarities and differences between the loop structures formed using these two methods. An estimation of the temperature of these graphitic nanoribbons during Joule heating is also reported based on the melting and evaporation of Pt nanoparticles."

Article

Chemical vapour deposition Evaporation Graphite Heat treatment Melting Nanoparticles Nanotechnology Platinum INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS

Observation of magnetic edge state in graphene nanoribbons

Hiroyuki Muramatsu JESSICA ROSAURA CAMPOS DELGADO FLORENTINO LOPEZ URIAS ANDRES RAFAEL BOTELLO MENDEZ HUMBERTO TERRONES MALDONADO MAURICIO TERRONES MALDONADO Dresselhaus Mildred (2010)

"The electronic structure and spin magnetism for few-layer-graphene nanoribbons synthesized by chemical vapor deposition have been investigated using near-edge x-ray absorption fine structure (NEXAFS) and electron-spin resonance (ESR). For the pristine sample, a prepeak was observed below the pi* peak close to the Fermi level in NEXAFS, indicating the presence of additional electronic states close to the Fermi level. The intensity of this prepeak decreased with increasing annealing temperature and disappeared after annealing above 1500 degrees C. The ESR spectra, which proved the presence of localized spins, tracked the annealing-temperature-dependent behavior of the prepeak with fidelity. The NEXAFS and ESR results jointly confirm the existence of a magnetic edge state that originates from open nanographene edges. The disappearance of the edge state after annealing at higher temperatures is explained by the decrease in the population of open edges owing to loop formation of adjacent graphene edges."

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA

Transitional behaviour in the transformation from active end planes to stable loops caused by annealing

Morinobu Endo Byoung-Ju Lee Yoong Ahm Kim Yong-jung Kim Hiroyuki Muramatsu Takahashi Yanagisawa Takuya Hayashi MAURICIO TERRONES MALDONADO Dresselhaus Mildred (2003)

"Here we investigate the stabilization process on the active outer/inner surfaces (or the end plane of a graphene sheet) for shortened cup-stacked-type carbon nanotubes caused by annealing, utilizing both analytic and electrochemical techniques. The suggested schematic procedure for loop formation is as follows: (a) formation of single-type loops between neighbouring truncated conical graphene layers at 900–1200?°C through a zipping mechanism after the evolution of hydrogen gas; (b) the transition from single- to multi-type loops above 1500?°C accompanying a decrease in specific surface area."

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA FÍSICA