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In this paper, a facile synthesis process is proposed to prepare multiwalled carbon nanotubes/magnetite (MWCNTs/Fe3O4) hybrids. The process involves two steps: (1) water-soluble CNTs are synthesized by one-pot modi. cation using potassium persulfate (KPS) as oxidant. (2) Fe3O4 is assembled along the treated CNTs by employing a facile hydrothermal process with the presence of hydrazine hydrate as the mineralizer. The treated CNTs can be easily dispersed in aqueous solvent. Moreover, X-ray photoelectron spectroscopy (XPS) analysis reveals that several functional groups such as potassium carboxylate (-COOK), carbonyl (-C=O) and hydroxyl (-C-OH) groups are formed on the nanotube surfaces. The MWCNTs/Fe3O4 hybrids are characterized with respect to crystal structure, morphology, element composition and magnetic property by X-ray diffraction (XRD), transmission electron microscopy (TEM), XPS and superconducting quantum interference device (SQUID) magnetometer. XRD and TEM results show that the Fe3O4 nanoparticles with diameter in the range of 20-60 nm were firmly assembled on the nanotube surface. The magnetic property investigation indicated that the CNTs/Fe3O4 hybrids exhibit a ferromagnetic behavior and possess a saturation magnetization of 32.2 emu/g. Further investigation indicates that the size of assembled Fe3O4 nanoparticles can be turned by varying experiment factors. Moreover, a probable growth mechanism for the preparation of CNTs/Fe3O4 hybrids was discussed., Article, APPLIED SURFACE SCIENCE. 255(20):8676-8681 (2009)

A novel one-step process using potassium persulfate (KPS) as oxidant is proposed in this paper to prepare water-soluble single-walled carbon nanotubes (SWNTs). The process without the need for organic solvents and acids is a low-cost, eco-friendly, facile method. Morphology observation by atomic force microscopy (AFM) indicates that the KPS-treated SWNTs were effectively debundled without obvious shortening in their length. The functional groups and thermal stability of the treated SWNTs were analyzed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). XPS results show that several functional groups such as potassium carboxylate (-COOK), carbonyl (-C=O) and hydroxyl (-C-OH) groups were formed on the surfaces of the SWNTs, while the TGA results reveal that the quantity of the functional groups can reach to approximately 20%., Article, APPLIED SURFACE SCIENCE. 255(15):7095-7099 (2009)

This paper reports the luminescence properties of spark-processed Si (sp-Si) prepared with different atmospheres such as air, O2, and N2 in low vacuum range (50–760 Torr). Three main luminescence bands are observed from spark-processed Si (sp-Si). In addition to the well-known two luminescence bands in the blue/violet peaking at 410 nm and green peaking at 500 nm, a novel UV luminescence band is detected for the sp-Si prepared in N2. The temperature dependence of photoluminescence (PL) characteristics of the newly detected UV luminescence band is examined. Further studies of photoluminescence excitation (PLE) have been performed and origins of luminescence are discussed based on the experimental results.

We adopt first-principle approach to calculate potential energy surfaces for α-quartz and -cristobalite silicon dioxide (SiO2) with hydrogenated impurities in the neutral, positive, and negative charged states. It is expected that H atoms in SiO2 have an important role to generate leakage current paths. In this paper, we calculate stable and unstable positions of a migrating H atom and discuss electrons or holes trapping mechanism. These results clarify that the dynamics of the H atom in the neutral, negative, and positive charged states should be different from one another, and therefore, the mechanism of the dielectric break down of SiO2 also depends on the charged environment. Based on the regional density functional theory, we have calculated the effective charge tensor density of the migrating H atom in the neutral state.