Preparing a magnetically responsive single-wall carbon nanohorn colloid by anchoring magnetite nanoparticles

A single-wall carbon nanohorn (SWNH) colloid was made to be magnetically responsive by anchoring magnetite nanoparticles prepared by the homogeneous mixing of FeCl(2)-FeCl(3) and NaOH solutions. Transmission electron microscopy observation showed the high dispersion of magnetite particles of 2-9 nm on the surface of the SWNH colloid, coinciding with the broad X-ray diffraction peaks of the magnetites. The magnetization measurements showed that the magnetite nanoparticles-anchored SWNH (mag-SWNH) colloid has the hybrid property of ferrimagnetism and superparamagnetism. It was demonstrated that mag-SWNH colloid dispersed in water by sonication responded to an external magnetic field, gathering toward a magnet. N(2) adsorption experiments showed the high nanoporosity of mag-SWNHs and that magnetite nanoparticles were preferably anchored at "nanowindow" sites and the entrance sites of interstitial pores. This magnetically responsive SWNH colloid should contribute to the field of drug delivery.     

Supramolecular catalysts for the gas-phase synthesis of single-walled carbon nanotubes

Reversed micelles containing metallic ions have been used as precursors of novel catalysts for the gas-phase synthesis of single-walled carbon nanotubes (SWNTs). This technique possesses the following advantages: (i) excellent solubility in organic solvents, which are used as reactants and (ii) facile preparation of multicomponent catalysts enabling systematic screening of catalyst compositions for the synthesis of SWNTs. In this study, we report the results of the screening study on the catalytic behavior of Fe-Mo binary catalysts during the synthesis of SWNTs. The results suggested that the catalytic ability was closely related to the strain of the crystal structure of Fe-Mo catalysts formed in the reaction and/or the phase transition caused by dissolution of the Mo atoms. The addition of lithium to the Fe-Mo binary catalysts has revealed an increase in the yield of SWNTs.     

Appropriate PEG compounds for dispersion of single wall carbon nanohorns in salted aqueous solution

Aiming at improving the dispersion state of single wall carbon nanohorns (SWNHs) in highly salted aqueous environment for potential biological applications, we compared the dispersion ability of different PEG-based dispersants in this work. We have found that ceramide-conjugated poly(ethylene glycol) (CPEG) dispersed SWNHs better than phospholipid-conjugated PEG (DPEG) in both water and phosphate buffer saline (PBS), which was evidenced by the measurements of particle sizes and dispersion stability. The large zeta potentials, according to the high surface charges, did not fully explain the high dispersion ability of CPEG for SWNHs. We propose that the more neutral linker group between alkyl and PEG chains in CPEG, in contrast to the charged phosphoethanolamino group in DPEG, resulted in the larger number of CPEG molecules attaching on SWNHs, and those PEG molecules enhanced the dispersion of SWNHs in water and PBS. In addition, for the first time we reported the adverse effect of the amino terminal group of PEG chain on the dispersion ability, compared with the methyl terminal group.     

Some electronic properties and morphological features of hybrid material DNA–SWCNT thin films

Thin films of hybrid material (ssDNA–SWCNT) prepared by ultrasonic mixing of both materials in water have been examined from the viewpoint of electrical, magnetic and optical properties, and morphological features to probe the possibly induced novel functions due to mutual interactions. Enclosing of DNA molecules inside a SWCNT is confirmed by the image and its motion. The temperature dependence of electrical resistivities is best-fitted to the two-dimensional variable-range-hopping regime. The radial breathing mode of the Raman spectra of the SWCNT exhibits significant modification due to interaction with DNA. The expected change in magnetic susceptibilities is not found in this case.     

The parameterized Steiner problem and the singular Plateau problem via energy

The Steiner problem is the problem of finding the shortest network connecting a given set of points. By the singular Plateau Problem, we will mean the problem of finding an area-minimizing surface (or a set of surfaces adjoined so that it is homeomorphic to a 2-complex) spanning a graph. In this paper, we study the parametric versions of the Steiner problem and the singular Plateau problem by a variational method using a modified energy functional for maps. The main results are that the solutions of our one- and two-dimensional variational problems yield length and area minimizing maps respectively, i.e. we provide new methods to solve the Steiner and singular Plateau problems by the use of energy functionals. Furthermore, we show that these solutions satisfy a natural balancing condition along its singular sets. The key issue involved in the two-dimensional problem is the understanding of the moduli space of conformal structures on a 2-complex.

     

Synthesis of 2′,3′-Dideoxy-2′-Fluorokanamycin A

2′,3′-Dideoxy-2′-fluorokanamycin A (23) was prepared by condensation of 6-azido-4-0-benzoyl-2,3,6-trideoxy-2-fluoro-α-D-ribo-hexopyranosyl bromide (13) and a protected disaccharide (19). Methyl 4,6-0-benzylidene-3-deoxy-β-D-arabino-hexopyranoside (5) prepared from methyl 4,6-0-benzylidene-3-chloro-3-deoxy-β-D-allo-hexopyranoside (1) by oxidation with pyridinium chlorochromate followed by reduction with Na₂ S₂O₄ was fluorinated with the DAST reagent to give methyl 4,6-O-benzylidene-2,3-dideoxy-2-fluoro-β-D-ribo-hexopyranoside (7). Successive treatment of 7 with NBS, NaN₃ and SOBr₂ gave 13. The structure of the final product (23) was determined by the ¹H and ¹⁹F and shift-correlated 2D NMR spectra.     

Nano-optical image and probe in a scanning near-field optical microscope

We study a nanometer-sized optical probe and image in a scanning near-field optical microscope (SNOM). We demonstrated the potential to observe 5-nm wide optical patterns using the SNOM. The probe profile was measured by using a knife-edge method and a modulated transfer function evaluation method. An aluminum covered and pipet-pulled fiber probe used here has two optical probes, one which has a large diameter of 350 nm and one which has a small diameter of around 10 nm.     

Structural evolutions of carbon nano-peapods under electron microscopic observation

Supramolecular assemblages made of single wall carbon nanotubes (SWNT) filled with fullerenes or metal doped fullerenes exhibit promising electronic structure variations at a nanometer scale. Nevertheless, the knowledge about the structural defects of these systems is still very limited. Here, we report structural evolutions under high-resolution electron microscopic observation at the sensitivity of a single atom detection for Ca@C₈₂ molecules encapsulated within SWNT.     

Underwater Acoustic Sensor with Fiber Bragg Grating

A new type of underwater acoustic sensor is proposed with an optical fiber Bragg grating (FBG). Because of the photoelasticity with respect to the refractive index and the elasticity of the fiber, the sound pressure in water modulates the Bragg reflection wavelength and, in turn, the intensity of the laser light transmitted through the FBG fiber. Good linearity between the detected signal and the sound pressure is obtained in the range from 81 dB to 140 dB re 1 μPa. Since the upper and lower limits of the acoustic signal level for operation of the sensor are limited by the driving circuit and the transduction of the sound in water, the sensor is expected to operate with much larger dynamic range both at higher and lower pressure levels. Operation of the sensor is very stable with the insertion of optical isolators into the system, although without the isolators the output signal fluctuates at low frequency due to the Fabry-Perot interference effect between the FBG and the various facets.     

Editorial

Journal of Sol-Gel Science and Technology -