Solution-synthesis And Theoretical Study Of Copper And Cupreous Composites Nanomaterials With Special Structure

In the work of this paper, we synthesized a series of copper and cuprous composites nanomaterials by using a simple solution chemical method. The reaction systems we studied include Ni stabilized Cu micro-nanoparticles, cubic Cu nanocages, Cu₂O/SiO₂ and Cu/SiO₂ octahedral core-shell nanocomposites, Cu₂O/TiO₂ and Cu/TiO₂ core-shell materials and Cu-Ag bimetallic nanocomposites. And on the basis of experiment and characterization, we also did an in-depth study on the mechanism of each reaction system.First, High purity Cu micro-nano powders have been synthesized by addition of trace Ni in aqueous-phase at room temperature. On the basis of electrode reactions, this trace Ni used as seeds to accelerate the reduction of Cu and as anodic protection agent to keep Cu products pure and stable. The obtained Ni stabilized Cu particles were about 300 nm in size with a high purity and stability. Moreover, Cu-Ni alloy nanoparticles with a size of about 50 nm have been synthesized under the similar reaction system and it was found that the formation of alloy nanoparticles was affected much by the adding order of agents.Second, we show a fast approach to the synthesis of cubic Cu nanocages in higher yield through a wet chemical reductive procedure. The performing reductive reactions from Cu (II) to Cu (0) in the aqueous phase can be finished in few minutes at the low temperature of 80°C. The resultant cubic Cu cages are aggregates of Cu nanoparticles with 200 nm in edge lengths and the inclusive nanoparticles are about 20 nm in size. According to the inspection of the Cu nanostructure-forming mechanism, we suggest that the reduction intermediate of roughly solid Cu₂O cubes formed in this strategy served as a spontaneous shape-controlled template and the cubic structure of the Cu nanostructures was evolved by morphology heredity from them. And this process is kinetically controlled growth, as the collaborated performance of Kirkendall effect and Ostwald ripening. In our work, we suggest that cubic Cu nanocages transform to hollow spheres if the reaction time is long enough, and the result of long time experiment has also support our viewpoint. Though, the cubic Cu cage is a structure metastable toward hollow spherical materials, the rapidly formed Cu products are stable in morphology both in solution and as powders in restrained reaction time.Third, Cu₂O/SiO₂ core–shell nanocomposites have been synthesized in water solution. During an in situ deposition process, a compact SiO₂ shell 9 nm in thickness is located at the surfaces of Cu₂O octahedral. On the basis of zeta potential study and IR character we presumed, dynamic absorbing and disengaging of Na+ at the interface of Cu₂O octahedra and the solution made it possible for the deposition of SiO₂ and dehydration of molecules made the formation of Cu–O–Si bonds between core and shell in the composites. This is the reason why the SiO₂ shell is so compact and uniform. As a result of reaction time-dependent and concentration-dependent experiments, it can be said that the thickness of the SiO₂ shell in our strategy is controllable in a determined range by adjusting the reaction time or the concentration of Na2SiO3. Moreover, these Cu₂O/SiO₂ core–shell octahedra were further used as precursors, depending on a simple disproportionation reaction of Cu₂O in acid, to easily achieve Cu/SiO₂ movable multicore–shell octahedral nanocomposites. The reaction was also controlled Kirkendall effect, and the thin SiO₂ octahedral shell was held in the final Cu/SiO₂ core–shell composite, inside of which formed several free Cu nanoparticles 50–80 nm in size.As an extension of Cu₂O/SiO₂ core-shell composites system, we also synthesized Cu₂O/TiO₂ octahedral core-shell composites in ethanol phase. In this system, fresh synthesized Cu₂O octahedra were used as precursors and the deposited process composed two hydrolyzing step: the primary hydrolyzing by surface absorbed water on the surface of Cu₂O octahedra and the follow main hydrolyzing by adding water/ethanol solution. This method is favor for formation of uniform integrated TiO₂ shells and their thickness can be controlled by adjusting the ratio of water/ethanol (W/E). According to the surface photovoltage spectroscopy of the Cu₂O/TiO₂ composites, we think the material would have a potential application in photocatalysis and photoelectric transition. Furthermore, Cu/TiO₂ composites have also been obtained by us.Last, we studied the system of Cu-Ag metallic nanocomposites. Cubic Cu nanocages were used here as precursor, and we synthesized Cu-Ag nanocomposites with uniform unit structure by simple replacement reaction between metals. We also studied the effect of method used on morphology of products. Inside, we showed a new method of using spontaneous separation process, instead of centrifuge or leaching, which can avoid the congregate of particles and make the resultants more uniform during the further displacement reaction.It can be said the 5 systems contracted with each other, which consummated the study of copper and cuprous composites nanomaterials. Beside the products were obtained, our work also showed a theoretical significance on the solution synthesis of nanomaterials. The synthesized methods used here were simple and the obtained copper and cuprous composites nanomaterials can be potential applied in areas as electronic devices, molecular catalysis and energy conversion.