Preparation Of Metal Oxides/multi-walled Carbon Nanotubes Composites And Studies Of Their Properties

Carbon nanotubes (CNTs) with unique structure and excellent chem-physical properties have attracted increasing interest because novel applications have been found for these materials in catalysis, electrode fabrication and gas storage/separation. Recently, as a new hybrid material, metal or metal oxides/CNT composites have received much attention for their promising applications in gas sensors, supercapacitors and so on. In our work, a series of metal or metal oxides/multi-walled carbon nanotube (MWNT) composites with controlled morphology have been obtained via the interaction of M(NH3)x2+ ions and acid-treated MWNTs. The photoelectric and magnetic properties of the obtained products have been studied.A simple method has been employed to modify MWNTs with ZnO nanostructures by zinc-ammonitum complex ion covalently attached to the MWNTs through the C?N bonds. When acid-treated MWNTs are soaked in the Zn(NH3)42+ solution at room temperature for a short time, the concentration of the Zn(NH3)42+ on the tips of the MWNTs is rather high due to the presence of a large number of carboxyl groups. As a result, the concentration of CONH2?Zn(NH3)32+ groups formed by the reaction of the amide and carboxyl in the intermediate products is high and favors the formation of flower-like structures on the tips of MWNTs after calcination. When prolonging the soaking time, the Zn(NH3)42+ are dispersed homogeneously around the MWNTs, and the concentration of CONH2?Zn(NH3)32+ groups in the intermediate products is low and prefers the formation of nanoparticles around the MWNTs after calnination. Photoluminescence measurements of the obtained products, strongly influenced by the ZnO nanostructures, have been performed. PL peak of ZnO nanoparticles directly attached to MWNTs is quenched to a considerable extent compared with that of flower-like ZnO in the flower-like ZnO/MWNT heterojunctions. It is due to the interaction of ZnO nanoparticles in excited state and MWNTs in electron transfer process. The photovoltage transient results of both of the hybrid materials display a positive response, which attributed to the photovoltage from ZnO attached to MWNTs, and a negative response which due to the transfer of photoinduced electrons of ZnO to MWNTs.CuO/MWNT composites have been prepared by the interaction of Cu(NH3)42+ ions and carboxyl groups on the surface of MWNTs. Cu/MWNT composites have also been prepared by adjusting the calcination temperature. In addition, Cu2O/MWNT composites have been obtained by increasing the amount of NH3?H2O. The morphology of Cu2O/MWNT composites could be controlled by adjusting the soaking time. UV?visible absorption spectra of the obtained Cu2O/MWNT composites present a blue-shift with the decrease of particle size, which could be attributed to the quantum confinement effect.Decoration of the MWNTs with CoO and NiO nanoparticles has been achieved via the interaction of M(NH3)x2+ (M = Co, Ni) ions and carboxyl groups on the surface of MWNTs. Both CoO/MWNT and NiO/MWNT composites present superparamagnetic behavior at 300 K, which can be attributed to the small particle size of CoO and NiO nanoparticles.