Preparation Of Copper Nanoparticles, Copper Film And Pattern By Photoreduction Method

We developed a facile method for preparing copper nanoparticles, filmedand patterned surface by ultraviolet (UV) irradiation of a mixture solutioncontaining a photoinitiator and a copper-amine coordination compound. Themechanism of the photoreduction is as follows: the photoinitiator wasphotolyzed and the radical was produced under UV irradiation. The copper ionabstracted the electron from the radical and was reduced to copper. The mainresults were emphasized as follows.1. The formula of photoreduction of copper ion was designed. Toimprove the reaction efficiency and expand the photoreduction system fromone that features the use of an expensive copper salt to one that employscommon copper salt, we choose the copper chloride as copper salt. But thecuprous chloride is insoluble in the ethanol. It inhibits the furtherphotoreduction. By adding diethanol amine into the ethanol solution of copperchloride, the copper-amine coordination was formed and the coppernanoparticles were prepared for the avoiding the formation of cuprouschloride. It was confirmed that the particles were copper nanoparticles byUV-vis spectra and the result of XRD. 2. The effects of concentration of copper salt, reaction temperature,irradiation intensity, stirring and the different solvents on the photoreductionwere investigated. The results are as follows:(1) The concentration of copper salt influenced on the size and sizedistribution of copper nanoparticles significantly. The lower concentration, thesmaller the copper nanopartiles. With increase of the concentration of coppersalt to0.1M, the copper film was formed on the surface of the side with UVirradiation.(2) The temperature was the another main effect on the size andsize distribution of copper nanoparticles. The size of copper particlesincreased and the size distribution turned broad with the increase of thetemperature.(3) With the stirring, the size and the size distribution of coppernanoparticles turned small and evenly respectively.(4) The irradiationintensity had slight effect on the size and size distribution but had great effecton the reaction velocity.(5) The alcohol with different number of carboninfluenced the reaction velocity. When the number of carbon was more than2,the velocity was influenced by viscosity. But, the radical could abstract themethoxyl group from the methyl alcohol, and the hydrogen radical wasproduced, which could reduce the copper ion and the photoreduction velocityincreased.3. The polymer capping agent could control the size and size distributionof copper nanoparticles. The frequently used capping agent, PVP which ispolyvinyl pyrrolidone, was used in our system and the result showed that thesize of copper nanoparticles turned small and the evenly. But it could also findon the UV-vis spectra that the absorbance peak of copper had serious red shift.The another polymer, polyethylenimine (PEI) which has the function group ofamine in the main chain and side chain of the polymer, controlled the size andsize distribution of copper nanoparticles well for PEI has the functions ofcoordinating. With the PEI, the absorbance peak of copper had no obvious red shift and the copper concentration had little effect on the copper size.4. The mechanism of photoreduction was studied by GC-MS and UV-visspectra. The copper ion was reduced by the radical which produced from thephotoinitiator and the photoreduction of the copper ion has two steps. TheGC-MS confirmed that methyl alcohol had participated in the photoreactionbut not ethanol.5. The copper film and copper pattern on the transparent substrate wereprepared by photoreduction of0.1M copper-diethanol amine coordination.The XRD result confirmed that the particles on the substrate were copper andthe UV-vis result showed the copper nanoparticle grew on the substrate stepby step.