Preparation And Characterization Of One-dimensional Nanomaterials In Carbon Group By Hydrothermal Method

Carbon group one-dimensional nanomaterials with quantum confinement effects and the small size effect have excellent optical, and magnetic properties, so have an important development prospects in the field of mesoscopic and nanodevices. Germanium / silicon oxide nano-cable, germanium oxide nanowires, nano-needles as well as Chrysotile nanotubes because of their unique structure and excellent performance, have attracted great interests. In this paper, a simple, environmentally friendly hydrothermal method was employed to prepare germanium / silicon oxide nano-cable, germanium oxide one-dimensional nanostructures and Chrysotile nanotubes. Furthermore their growth mechanism and photoluminescence properties have been studied.Ge/SiO_x nanocables were synthesized by hydrothermal method, using GeO₂ and Si powders as reactants. The product was characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) with energy dispersion spectroscopy(EDS). The Ge/SiO_x nanocables were obtained in large-scale, which had even diameters and the lengths of several hundred nanometers. It has been confirmed that the nanocables possessed the special structure of core-shell. Ge core was grown along a direction of [211].The growth of the Ge/SiO_x nanocables was considered to occur via the combination of oxide-assisted growth and vapor-liquid-solid processes, and the fabrication of nanocables was determined by the ratio of GeO₂ and Si powders. In addition, other products of special structures prepared by different experimental conditions have also been analysised.Bulk-quantity GeO₂ nanostructures have been synthesized by hydrothermal method, using germanium oxide powder as raw materials. Products were characterized by SEM, TEM, XRD, and so on. Most of GeO₂ nanostructures were smooth and straight in length. Apart from the conventional structure of nanowires, there were special structures of Nanoneedle and Nano-double needle. Results of X-ray diffraction and selected area electronic diffraction (SAED) showed that the nanostructures were hexagonal crystalline GeO₂. The nanostructures can emit stable and high brightness violet light at 368 nm, blue light at 472nm and green light at 545nm under excitation at 221 nm. The intensity of the emission is one order of magnitude higher than that of GeO₂ powder. The photoluminescence (PL) may is attributed to exciton recombination and some defects. The growth mechanism of GeO₂ nanostructures has also been discussed.In a neutral environment, Chrysotile nanotubes have been synthesized by hydrothermal method, with MgO and SiO₂ powder as the starting materials. X-Ray Diffraction(XRD), Scanning Electron Microscopy(SEM), Transmission Electron Microscopy(TEM) were used to characterize the crystal structure and morphology of the as-prepared samples. We found that the diameter of Chrysotile is uniform. Their outer diameter is about 30 50 nm and the inner diameter is about 6 ⁸ nm. The length of them is a few hundred nanometers. The XRD analysis indicated that the as-prepared Chrysotile is a Rhombohedral structures. The results of HRTEM and SAED showed that the {006} planes of serpentine roll up along the [006] direction to form the tubular structure. Furthermore, the curves of temperature and pressure with time showed that the water might participate in the reaction. Differential thermal analysis showed that chrysotile crystal is pure and uniform. The IR spectrum of Chrysotile nanotubes is similar to that of the natural Chrysotile. In addition, using magnesium carbonate as raw materials, magnesium oxide nano-plate was produced by hydrothermal method, with the thickness of 10 nm and six laterals of 1 to 2μm.