Controlled Synthesis And Properties Study Of Copper And Cuprous Oxide Nanostructured Materials

Copper-based nanomaterials have great application value in the field of catalysis, adsorption, antibacterial materials, wear resistance and electrochemistry due to its rich sources and unique physical and chemical properties. This thesis focused on controlled synthesis of cubic cuprous oxide nanocages and monodisperse copper nanoparticles in organic solvents through liquid-phase chemical routes. The obtained products were characterized in detail by XRD, SEM, TEM, HRTEM and IR. The formation mechanism of the products was analyzed through tracking reaction process and the influences of different experimental conditions on the size and morphology of the product were studied. What is more, the sensor properties of different morphologies of cuprous oxide nanoparticles were tested to investigate the relationship between the structure and properties. This work studies the intrinsic controlling mechanism of nanoparticles and provides effective means to preparation of hollow cuprous oxide nanocages and copper nanoparticles in solution.1. Synthesis of cubic Cu2O nanocages through acid etching methodCu2O nanocages with the diameter of80-90nm were synthesized at35℃using Copper chloride as a salt precursor, ascorbic acid and hydrazine hydrate as reducing agents, and sodium hydroxide as the pH regulator. The average thickness of the walls is ca.5nm. Studies show that the formation processes of Cu2O nanocages were as follows. When the ascorbic acid was added to the mixed solution of cupric chloride and sodium hydroxide,Cu2O nanoparticles were prepared in a few seconds. To reduce its surface energy, nanoparticles appeared to be aggregated, and then formed cubic Cu2O aggregates with rough surface and solid structure. With the extension of reaction time and nanoparticles aggregation, outside surface of the aggregates became smoother and had better crystalline. Finally, the crystalline of the external and internal of the aggregates was not consistent with each other. Because the pH of the solution was about5.0at this time, cuprous oxide particles were easily etched by acid. Once a small area of the surface of solid Cu2O is etched under the suitable acidity, its interior nanoparticles will be completely etched with the outer shells being preserved, owing to the different crystalline states between the inside and outside of Cu2O. Thus, the selectivity of acidic etching led to the formation of hollow Cu2O nanocubes with thick and broken walls. When the reaction time reached to5min, N2H4·H2O was added to the mixture. Because the above hollow structure was not closed completely,N2H4·H2O could reduced a part of Cu2O on the inside and outside surface of hollow structure to Cu nanoparticles in a certain period of time. The formed Cu nanoparticles with high surface energy were small and less, so a small amount of Cu nanoparticles could aggregate and grow on the broken places of the walls of hollow Cu2O. Then, these hollow Cu2O were separated by centrifugation and Cu nanoparticles on their walls would be oxidized to Cu2O nanoparticles by oxygen in the subsequent process of centrifugation and washing. Ultimately, Cu2O nanocages with thin walls and complete structure were prepared.We also discussed effects of different experimental conditions including the addition way and the amount of AA, reaction time, and reaction temperature on the results. In addition, we have discovered that Cu2O nanocages have more excellent performance as gas sensor than solid Cu2O nanocubes.2. Controlled synthesis of copper nanoparticles in organic phaseIn this experiment, copper nanoparticles which had excellent dispersion and uniform size in organic solvent were prepared by only using acetylacetonate copper and oleylamine as reactions. The diameter of Cu nanoparticles was about12nm. The Cu nanoparticles were capped with oleylamine through the analysis of the infrared spectrum of the product, so nanoparticles could be uniformly dispersed in hexane. The reaction was carried out at200℃with nitrogen atmosphere. The reaction temperature was relatively high, so the formation mechanism of Cu nanoparticles may be the thermal decomposition of acetylacetonate copper. In addition, oleylamine could be used as mild reducing agent in the synthesis of metal and metal oxide nanomaterials, so the formation of Cu nanoparticles was caused by the oxidation-reduction reaction of acetylacetonate copper and oleylamine. Finally, we also discussed effects of different experimental conditions including the reaction temperature, the solvent, the ratio of cupric acetylacetonate and oleyamine and the amount of oleic acid on the morphology and the size of the product. The experiment which had simple reactants and facile operation process provided an effective method for controlled synthesis of Cu nanoparticles.