Preparation And Application Of Macro-Centimeter Level Silver Nanostructures

Silver nanostructures have attracted wide attention because of their excellent optical,electrical,thermal,magnetic and catalytic properties.However,due to the limitation of synthesis method,it is difficult for silver nanostructures to reach the macro-centimeter level,which makes it impossible for many studies on silver nanomaterials to be conducted by conventional means.Many their unique properties and wide applications have not yet been discovered and utilized.In this paper,macro-centimeter level silver nanostructures were prepared by vacuum thermal evaporation method and solid-state ionics method under the different current electric field using the suitable silver ions conductor films.The surface morphology and chemical composite of the prepared silver nanostructures were characterized by field emission scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS)attached to the SEM.The applications of the obtained nanostructures in surface-enhanced Raman scattering(SERS)and transparent conductive films were also studied.The main contents are as follows:High quality silver films and silver ions RbAg4I5 conductor films on the quartz glass substrates were prepared by vacuum thermal evaporation with the optimum parameters.Silver nanostructures with different morphologies,such as nanowire clusters,nanowire bundles,nanowire sheets and nanowire arrays were prepared on the cathode when the impressed current intensity were 1?A,4?A,7?A and 10?A,respectively.The growth mechanism of macro-centimeter level silver nanostructures was further explored by the fractal dimension of their nanostructures.The resulted showed that the silver nanostructures with abnormity shape were related to the irregular electrode interface and the apical growth advantage.When the current intensity was 7?A,the obtained silver nanostructures with the lengths of 3cm were branched-shaped and the fractal dimension of silver nanostructures was 1.70,and the diameter of nanowires ranged from 80?180nm,which indicates the silver nanostructures grow most at the edge of the cathode,and the nanostructures are arranged most closely.The Raman enhancement scattering properties of the silver nanostructures SERS substrates with different morphologies were observed by Rhodamine 6G(R6G)solutions as probe molecules by confocal micro-Raman spectrometer,and melamine in aqueous solutions and milk solutions were detected by surface-enhanced Raman spectroscopy.When the impressed current intensity was 4?A,the limiting concentrations of R6G solutions for the prepared macro-centimeter level silver nanostructures substrates is 10-16mol/L and 10-15 mol/L under the current intensity was 10?A,respectively.The resulted that the SERS activity of silver nanostructures with different morphologies varied greatly,which mainly depended on the arrangement order and surface roughness of the nanostructures.The detection effects of melamine in aqueous solutions and milk solutions were the best when ordered arrangement silver nanowire arrays as SERS substrates,and the limit concentrations were 10-16 mol/L and 10-10 mol/L,respectively.The transparent conductive films were prepared by drop coating method using macro-centimeter level silver nanowires.The optical and electrical properties of the prepared conductive films were characterized by using an ultraviolet-visible spectrophotometer and four point probe and the effects of dispersant content and drop coating times on the photoelectric properties of the conductive films were studied.In order to meet the requirements of transmittance and sheet resistance of silver nanowires transparent conductive films in optoelectronic devices,the dispersant content of 15%and the 2 times dropping were choosed to obtain the excellent optical and electrical properties.On the basis of this study,the influence of the morphology of silver nanowires on the photoelectric properties of the films was also studied The results showed that the transparent conductive films made of silver nanowires under 7?A current intensity have the best optoelectronic properties,and its transmittance and sheet resistance were 87.3%and 15.80?/sq,respectively.