Effect of functional groups at hole edges on cisplatin release from inside single-wall carbon nanohorns

We incorporated cisplatin inside single-wall carbon nanohorns (NHs) and revealed that 70% of the cisplatin was released from NHs having holes with hydrogen-terminated edges when they were immersed in phosphate-buffered saline (PBS). However, only 15% was released from NHs having holes with oxygen-containing functional groups at the hole edges (NHox). Elemental analysis indicated that -COOH and -OH groups at the hole edges of NHox changed mainly to -COONa and -ONa groups by immersion in PBS. These groups decreased the practical hole diameters, which resulted in hindering the cisplatin release from NHox. This means that the release of the material from inside NHox would be controlled by chemically modifying the functional groups attached to the hole edges of NHox; thus the potential applicability of NHox to a material carrier would be enhanced.     

Control of hole opening in single-wall carbon nanotubes and single-wall carbon nanohorns using oxygen

Due to the simplicity of the process, holes in the graphene walls of single-wall carbon nanotubes (SWNTs) and single-wall carbon nanohorns (SWNHs) have often been opened using O2 gas at high temperatures, even though this contaminates the nanotubes with carbonaceous dust (C-dust). To open holes with less C-dust contamination, we found that a slow temperature increase of 1 degrees C/min or less, in air, was effective. We also found that SWNHs having little C-dust could store a large quantity of materials inside the tubes. We infer that the local temperature increase due to the exothermic reaction of combustion may have been suppressed in the slow combustion process, which was effective in reducing the C-dust.     

Controlling the incorporation and release of C60 in nanometer-scale hollow spaces inside single-wall carbon nanohorns

We succeeded in large-scale preparation of single-wall carbon nanohorns (SWNH) encapsulating C60 molecules in a liquid phase at room temperature using a "nano-precipitation" method, that is, complete evaporation of the toluene from a C60-SWNH-toluene mixture. The C60 molecules were found to occupy 6-36% of the hollow space inside the SWNH, depending on the initial quantity of C60. We showed that the C60 in C60@SWNHox was quickly released in toluene, and the release rate decreased by adding ethanol to toluene. Numerical analysis of the release profiles indicated that there were fast and slow release processes. We consider that the incorporation quantity and the release rate of C60 were controllable in/from SWNHs because SWNHs have large diameters, 2-5 nm.     

Micrometer-sized graphitic balls produced together with single-wall carbon nanohorns

We present in this report a new type of particles with micrometer-order sizes, which we called giant graphitic balls (GG balls). The GG balls are produced by CO2 laser ablation of graphite together with single-wall carbon nanohorns. They have graphitic structures whose layers tend to align parallel with the GG-ball surfaces, resulting in polygonal-like arrangements. Comparing the GG-ball structure with that of the previously reported polygonal graphite-particles, the growth mechanism of the GG ball is discussed briefly.     

Quantum effects on hydrogen isotope adsorption on single-wall carbon nanohorns

H(2) and D(2) adsorption on single-wall carbon nanohorns (SWNHs) have been measured at 77 K, and the experimental data were compared with grand canonical Monte Carlo simulations for adsorption of these hydrogen isotopes on a model SWNH. Quantum effects were included in the simulations through the Feynman-Hibbs effective potential. The simulation predictions show good agreement with the experimental results and suggest that the hydrogen isotope adsorption at 77 K can be successfully explained with the use of the effective potential. According to the simulations, the hydrogen isotopes are preferentially adsorbed in the cone part of the SWNH with a strong potential field, and quantum effects cause the density of adsorbed H(2) inside the SWNH to be 8-26% smaller than that of D(2). The difference between H(2) and D(2) adsorption increases as pressure decreases because the quantum spreading of H(2), which is wider than that of D(2), is fairly effective at the narrow conical part of the SWNH model. These facts indicate that quantum effects on hydrogen adsorption depend on pore structures and are very important even at 77 K.     

Isolating single-wall carbon nanohorns as small aggregates through a dispersion method

An approach to isolating small aggregates of single-wall carbon nanohorns (SWNHs) is presented. SWNHs are ultrasonically treated in an aqueous solution of surfactant, resulting in dispersion of SWNH aggregates. Subsequent centrifuging enables the separation of small aggregates from larger aggregates or agglomerations and removal of graphitic particles (GG balls), the main impurity. The SWNHs obtained in this way were purified and formed small aggregates, thus exhibiting characteristics superior to those of SWNHs before treatment. We believe that the ability to isolate small SWNH aggregates in an aqueous solution should contribute to their application in the fields of biological sensing and drug delivery systems.     

Optimum hole-opening condition for Cisplatin incorporation in single-wall carbon nanohorns and its release

We enclosed cisplatin (CDDP), an anticancer drug, inside single-wall carbon nanohorns (SWNH) with holes opened by being heated from room temperature to a target temperature (475-580 degrees C) in flowing dry air, with an increase rate of 1 degrees C/min. The optimum target temperature was found to be 500 degrees C, in terms of the least amount of CDDP deposited outside the SWNH, when the quantity of CDDP encapsulated inside the SWNH was 12 wt %. The incorporated CDDP was slowly released from the SWNH in phosphate buffer saline, and the released quantity was 80%, which was greatly improved from the previous value of 15%. This indicated that a CDDP-containing SWNH could become more potentially useful for biological applications.     

Synthesis of solid solutions of double-layered Ruddlesden-Popper phases in the Gd2O3-SrO-Fe2O3-Al2O3 system

The continuous Gd₂Sr(Al_{1 ? x} Fe _x )₂O₇ solid solution series was synthesized by a solid-state route over the entire concentration range (0 < x < 1). The processing stages of Gd₂Sr(Al_{1 ? x} Fe _x )₂O₇ series were investigated, and phase interaction schemes reflecting the multistaged formation of double-layered Ruddlesden-Popper solid solution are constructed. The closeness of the reactive mixture composition to the composition of individual compounds Gd₂SrAl₂O₇ or Gd₂SrFe₂O₇ is of importance for the realization of a particular way of Gd₂Sr(Al_{1 ? x} Fe _x )₂O₇ solid solutions formation.     

Preparation of Gd2O3:Yb,Er and Gd2O2S:Yb,Er infrared-to-visible conversion phosphor ultrafine particles using an emulsion liquid membrane system

Upconverting phosphor fine particles (Gd2O3:Yb,Er and Gd2O2S:Yb,Er) have been prepared, using an emulsion liquid membrane (ELM, water-in-oil-in-water (W/O/W) emulsion) system. The composite Gd-Yb-Er oxalate particles obtained in the ELM system were mainly 20-60 nm in size, together with a smaller amount of submicrometer-sized spherical particles. Nanometer-sized Gd2O3:Yb,Er and Gd2O2S:Yb,Er particles were obtained by calcination in air and in sulfur atmosphere, respectively, of the precursor oxalate particles prepared in the ELM system. Upconversion emissions (red and green) were obtained from the Gd2O3:Yb,Er and Gd2O2S:Yb,Er particles prepared in the ELM system under infrared excitation (lambdaex=980 nm) via a two-photon process. Upconversion phosphor fine particles, about 50 nm in diameter, may be applied to the luminescent reporter material for the detection of the targeted analyte in immunoassays or DNA assays.     

Synthesis and characterisation of Gd2O3 nanocrystals functionalised by organic acids

Nanocrystals of Gd2O3 have been prepared by various methods, using, e.g., trioctylphosphine oxide (TOPO), diethylene glycol (DEG) or glycine. The crystalline particles were of sizes 5 to 15 nm. Different carboxylic acids, e.g., oleic acid or citric acid, were adsorbed onto the surface of the particles made with DEG. IR measurements show that the molecules coordinate to the Gd2O3 surface via the carboxylate group in a bidentate or bridging manner. The organic-acid/particle complexes were characterised by XRPD, TEM, FTIR, Raman, and XPS.     

Synthesis and optical properties of Gd2O3:Pr3+ phosphor particles

Spherical-shaped Gd₂O₃:Pr³⁺ phosphor particles were prepared with different concentrations of Pr³⁺ using the urea homogeneous precipitation method. The resulting Gd₂O₃:Pr³⁺ phosphor particles were characterized by X-ray diffraction, field emission scanning electron microscope, and photoluminescence spectroscopy. The effects of the Pr³⁺ doping concentration on the luminescent properties of Gd₂O₃:Pr³⁺ phosphors were investigated. Photoluminescence measurements revealed the Gd₂O₃:1?% Pr³⁺ phosphor particles to have the strongest emission. The luminescence properties of Gd₂O₃:Pr³⁺ particles are strongly affected by the phosphor crystallinity and X-ray diffraction measurements confirmed that the crystallinity of Gd₂O₃ cubic structure could be enhanced by increasing the firing temperature. The luminescent Gd₂O₃:Pr³⁺ phosphor particles have potential applications in areas, such as optical display systems, lamps and etc.     

Bulk synthesis of linear carbon chains confined inside single-wall carbon nanotubes by vacuum discharge

Carbyne, an infinite carbon chain, has attracted much interest and induced significant controversy for many decades. Recently, the presence of linear carbon chains (LCCs), which were confined stably inside double-wall carbon nanotubes (DWCNTs) and multiwall carbon nanotubes (MWCNTs), has been reported. In this study, we present a novel method to produce LCCs in a film of carbon nanotubes (CNTs). Our transmission electron microscopy and Raman spectroscopy revealed the formation of a bulk amount of LCCs after electric discharge of CNT films, which were used as field emission cathodes. The LCCs were confined inside single-wall CNTs as well as DWCNTs. Furthermore, two or three LCCs in parallel with each other are encapsulated when the inner diameter of CNT is larger than approximately 1.1 nm.     

Single-walled carbon nanohorns coated with Fe2O3 as a superior anode material for lithium ion batteries

A novel composite of Fe(2)O(3) and single-walled carbon nanohorns (SWCNHs) was firstly developed via a simple hydrothermal method. As an anode material for lithium ion batteries, a Fe(2)O(3)/SWCNHs composite shows excellent rate performance and cycle stability, even at a high current density of 1000 mA g(-1).     

Synthesis and modification of carbon nanohorns structure for hyperthermic application

Single-wall carbon carcass nanoparticles (nanohorns) (CNHs) are synthesized by two methods: electric arc and electron evaporation of graphite in the inert atmosphere. Distinctions in the structures of obtained materials are revealed using electron microscopy and Raman spectroscopy. The chemical structure of the CNH surface is investigated by X-ray photoelectron and NEXAFS spectroscopy during oxidation. It is found that oxidation causes the destruction of CNH agglomerates and weakly affects the structure of graphene nets. However, these changes are sufficient for an increase in the infrared radiation absorption by the dispersion of nanohorns in water. It is shown that the efficiency of 808 nm laser heating of a CNH dispersion depends on the synthesis method and chemical modification of nanoparticles, which enables their potential use for local hyperthermia of cells of living organisms in cancer therapy.     

Functionalisation of carbon nanohorns

The functionalisation of single wall carbon nanohorns via 1,3-dipolar cycloaddition has been achieved, and the products have been characterised by spectroscopy, microscopy and thermogravimetry.     

Subsolidus phase relations in the Gd2O3-Rh2O3 system

The Gd₂O₃-Rh₂O₃ system is studied using the anneal-and-quench technique, X-ray powder diffraction, thermal analysis, and chemical analysis. A schematic subsolidus phase diagram is designed. One double oxide of composition GdRhO₃ is found to exist. It was characterized using some physicochemical methods.     

Synthesis and characterization of SiO2/Gd2O3:Eu core-shell luminescent materials

Europium-doped Gd2O3 with an average size of approximately 15 nm was coated on the surface of preformed silica nanospheres by the wet chemical method. SEM and TEM photographs showed that SiO2/Gd2O3:Eu core-shell submicrospheres are obtained. XRD patterns indicated that the Gd2O3:Eu shell is crystalline after heat treatment. FTIR and XPS spectra showed that the Gd2O3:Eu shell is linked to the silica surface by forming a Si-O-Gd bond. Photoluminescence studies showed that the luminescent properties are still retained after coating on an inert silica core; additionally, we noted that the emitting peaks are broadened, which results from size effects and interface effects of nanocrystal.