Preparation Of Low Dimensional Silver Nanostructures With Controllable Size And Morphology

The synthesis of silver nanostructures was very active at present,but the size of one dimensional silver naostructure was mostly single and narrow,the diameter is about 100 nm or 60 nm.The crystal structure is mainly polycrystalline and twin structure,while the cross-section is irregular or pentagon.The as-synthesized silver nanoplates'size(horizontal size,length edge) was mostly around 100 nm with a width-thickness ratio(edge length and thickness ratio)≤6.This uniformity of size and morphology was not conducive to the performance of silver nanostructures and large-scale applications,and finding a new synthesis method for the preparation of adjustable size and morphology of the silver nanostructures has very important academic significance and broad application prospects.In this paper,we sucsessfuly synthesized silver nanowires with rectangular cross-section,single crystal nano-coaxial cables,silver nanowires with lengths of several millimeters and silver nanoplates with edge lengths of several micrometers by solvothermal or hydrothermal route.The as-obtained silver products were characterized and tested and the growth mechanism of former silver naostructures was dicussed.Firstly,we have prepared large scale silver nanowires with different cross-section by using ethylene glycol as reducing agent,PVP as crystal growth control agent,and Fe³⁺ as etching agents under solvothermal condition.The diameter of as-synthesized silver nanowires changed from 50 nm to 300 nm,and the structural of cross-section changed from pentagon to rectangular with the increase of [Fe³⁺].It showed that the twin crystal seed could be gotten into a single crystal effectively by controlling the[Fe³⁺],which realized kinetically controllable size and morphology for silver nanowiresSecondly,we have prepared high-purity cylindrical coaxial silver/polymer nano-cables by using PVP as reduction agents and silver chloride as precursors.And these nano-cables can assemble into perfect order linear array.The influential factors such as reaction temperature,reaction time,and concentration of the reagents were studied.The results showed that the reducing ability and solvents could control the type of silver seed,cross-section structure and size,and controllable preparation of asingle crystal silver nanowires.The adsorption of PVP on surface of silver nanowires is the key role for the formation of silver metal/polymer nano-coaxial cable and order array.Thirdly,we have successfully synthesized single-crystal silver nanoplates with edge lengths and aspect ratio≥10 in a large-scale and high-purity through a low temperature solvothermal approach,where N-dimethyllformamide(DMF) was used as a main reducing agent and a solvent,polyvinylpyrrolidone(PVP) was used as capping agents,and silver nitrates were used as precursors.We investigated the impact of different solvents on the morphologies of silver nanostructures,and proposed a possible growth mechanism of the as-synthesized silver nanoplates with large edge lengths and high aspect ratios.The current work provides a new reliable kinetic approach to tune the edge length and aspect ratios of silver nanoplates and the as-obtained silver nanoplates with large edge lengths and aspect ratios show potentially important applications in polymer-based conductive composites and electromagnetic shielding materials.