Showing papers by "Ryo Kitaura published in 2007"

Raman Spectroscopy of Size-Selected Linear Polyyne Molecules C2nH2 (n = 4−6) Encapsulated in Single-Wall Carbon Nanotubes

Abstract: Polyyne molecules (C2nH2, n = 4−6) encaged inside single-wall carbon nanotubes (SWNTs) are investigated by Raman spectroscopy. The Raman bands observed in the region of 2000−2200 cm-1 are identifie...

Enhanced 1520 nm photoluminescence from Er3+ ions in di-erbium-carbide metallofullerenes (Er2C2)@C82 (isomers I, II, and III).

Abstract: Di-erbium and di-erbium-carbide endohedral metallofullerenes with a C82 cage such as Er2@C82 (isomers I, II, and III) and (Er2C2)@C82 (isomers I, II, and III) have been synthesized and chromatographically isolated (99%). The structures of Er2@C82 (I, II, III) and (Er2C2)@C82 (I, II, III) metallofullerenes are characterized by comparison with the UV–vis−NIR absorption spectra of (Y2C2)@C82 (I, II, III), where molecular symmetries of the structures are determined to be Cs, C2v and C3v, respectively. Furthermore, enhanced near-infrared photoluminescence (PL) at 1520 nm from Er3+ ions in Er2@C82 (I, III) and (Er2C2)@C82 (I, III) have been observed at room temperature. The PL intensities have been shown to depend on the symmetry of the C82 cage. In particular, the PL intensity of (Er2C2)@C82 (III) has been the strongest among the isomers of Er2@C82 and (Er2C2)@C82. Optical measurements indicate that the PL properties of Er2@C82 (I, II, III) and (Er2C2)@C82 (I, II, III) correlate strongly with the absorbance at...

Endohedral Metallofullerenes and Nano-Peapods

Abstract: In this review article, we deal with the structures and properties of novel hybrid nanocarbon materials, which are created by the incorporation of atoms and molecules in hollow spaces of fullerenes and carbon nanotubes (CNTs); these hybrid materials are called endohedral metallofullerenes (in the case of metal atom incorporated fullerenes) and nano-peapods, respectively. Synthesis procedures, structural characterizations by synchrotron powder x-ray diffraction, electronic structures, and magnetic properties of endohedral metallofullerenes are discussed. The structure and properties of nano-peapods by high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), scanning tunneling microscopy (STM) and field effect transistor (FET) transport measurements together with their synthesis procedures are described. The utilization of the low-dimensional nanosized spaces of CNTs to produce novel low-dimensional nanocluster, nanowire and nano-tube materials is also discussed.

Magnetism of the endohedral metallofullerenes M @ C 82 ( M = Gd , Dy ) and the corresponding nanoscale peapods: Synchrotron soft x-ray magnetic circular dichroism and density-functional theory calculations

Abstract: Synchrotron soft x-ray magnetic circular dichroism (SXMCD) spectroscopy at the Gd and Dy ${M}_{5}$ edges is reported on endohedral metallofullerenes ($M@{\mathrm{C}}_{82}$, $M=\mathrm{Gd}$ and Dy) and the corresponding nanopeapods [$(M@{\mathrm{C}}_{82})@\mathrm{SWNT}$, SWNT represents single wall carbon nanotube] in a temperature range between 10 and $40\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The magnetic moment has also been determined by theoretical calculations, which are based on the Hartree-Fock approximation with relativistic corrections. Because of the element-specific measurement of SXMCD, magnetization processes of Gd and Dy ions of nanopeapods have been selectively observed. The temperature dependence of magnetic moments of the metallofullerenes and nanopeapods follows the Curie-Weiss law with a small Weiss temperature, indicating that the magnetic interaction between encapsulated rare-earth metal atoms is relatively weak. Although the observed differences in Curie constants and Weiss temperatures between $\mathrm{Gd}@{\mathrm{C}}_{82}$ and $(\mathrm{Gd}@{\mathrm{C}}_{82})@\mathrm{SWNT}$ are small, those of $\mathrm{Dy}@{\mathrm{C}}_{82}$ and $(\mathrm{Dy}@{\mathrm{C}}_{82})@\mathrm{SWNT}$ are significant. This observation is consistently explained by charge transfer-induced crystal-field effects.

Synthesis and spectroscopic characterization of salmon dna-wrapped single-wall carbon nanotubes

Abstract: Single-wall carbon nanotubes (SWNTs) can be well-dispersed in water by wrapping with short segments of natural DNA from salmon sperm. We report here the isolated DNA-wrapped SWNT hybrids. Measurements were carried out using UV-vis-NIR, near-infrared photoluminescence (PL) spectrum and atomic force microscopy (AFM). A possible charge transport between SWNTs and salmon-DNA is discussed in terms of observed spectral shifts in the photoluminescence spectra.

Carbon‐Nanotube‐Based Hybrid Materials: Nanopeapods

Abstract: This review article focuses on the structures and properties of novel hybrid nanocarbon materials, which are created by incorporating atoms and molecules into the hollow spaces of carbon nanotubes (CNTs); thus they are called nanopeapods. After dealing with synthesis procedures, we discuss the structures and electronic properties of the hybrid materials based on high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS), X-ray and electron diffraction, scanning tunneling microscopy (STM), and field-effect transistor transport measurements. Utilization of the low-dimensional nanosized spaces of CNTs to produce novel low-dimensional nanocluster, nanowire, and nanotube materials is also discussed.