Preparation Of Silver Nanorods With High Aspect Ratio And Study On Surface Plasmon Characteristics

Due to its unique optical properties and significant localized surface plasmon resonance effect,the silver nanorod has shown strong application potential in the on-chip nanophotonic integrated circuit.The local surface plasmon multi-order resonance peaks of silver nanorods with high aspect ratio include obvious narrow linewidth high-order resonance peaks,which means that the low-loss characteristics in practical applications and an indispensable position in applied research of nano-optics.The current methods for synthesizing silver nanorods still have some defects,such as poor size uniformity and uneven morphology.Therefore,how to prepare high aspect ratio silver nanorods stably and controllably becomes an urgent problem in the research and application of surface plasmon properties.Based on the present methods of preparing low-dimensional silver nanostructures,this paper proposes a method to prepare silver nanorods using silver seeds,and obtains silver nanorods with stable yield and high aspect ratio,and analyzes the basic properties of surface plasmons.The main research works are as follow:(1)Researching on the current synthesizing methods of silver nanorods with high aspect ratio,analyzing the factors that affect the differentiation of the long and short axes of silver nanorods,and making combination and improvement on the basis of multi-parameter comparison experiments of various methods.A method is pointed that can produce the target silver nanorods stably via the silver seeds that use the high-molecular polymer—sodium alginate as the carrier,which obtains the silver nanorods with the aspect ratio of 14～20,and the range difference of diameter distribution is 6 nm.The yield of silver nanorods is stable,and the size is uniform.(2)To study the influence of the amount of silver seed,reaction temperature and polymer chain on the synthesis of silver nanostructures when using sodium dodecyl sulfate(SDS)as a surfactant.In the reaction at room temperature,a new type of silver nanorod with hexagonal cross-section was prepared by using polymer chain seeds;adjusting the reaction temperature,a variety of silver nanostructures with different morphologies can be generated.In order to verify the effect of polymer chains on the growth of silver nanostructures,only polymer chains were introduced at 0℃(that means no silver seeds),and a hexagonal silver nanosheet structure with clear edges was formed by the reaction;changing the reaction temperature still produced various morphologies of silver nanostructures,which indicate that high molecular polymers are highly sensitive to temperature.The synthesized silver nanorods and nanosheets show that high molecular polymers can be used as a synthesis environment for metal nanostructures with various morphologies,and verify the possibility of preparing metal nanostructures at 0℃.(3)Performing basic analysis of surface plasmon characteristics of the prepared silver nanorods with high aspect ratio.Using numerical calculations and dark-field scattering methods,the scattering spectra in the visible-infrared band of silver nanorods that in the silicon-air system are obtained.The high aspect ratio silver nanorods synthesized in this research work showed the property that the localized surface plasmon resonance peaks gradually red-shifted with the increase in aspect ratio.At the same time,the high-order resonance peaks have obvious narrow line widths,which can be applied to the research on micro-nano devices;comparing the scattering spectra whenθ=0°and θ=15° that is the angle between incident electric field and long axis direction of the silver nanorods,it can be seen that the odd-order and even-order resonance modes of the silver nanorods with high aspect ratio can be excited at the same time when 0°<θ<90°.Furthermore,when the effective refractive index of the substrate material becomes smaller,the scattering resonance peaks of the silver nanorods will be blue-shifted.