Preparation Of Cu-Ag Bimetallic Nanoparticles By Dopamine Oxide Polymerization And Metallization Chemical Reduction

The bimetallic core-shell structure nanoparticles endowed with its unique properties on account of their unique structure, showing the broad application prospect in many fields, including electricity, optical, biological medicine, biological sensors and other fields. As one of the nanometer materials, silver nanoparticles have excellent electrical conductivity, thermal conductivity, resistance to oxidation, catalytic properties and bactericidal properties, and their chemical performance is stable. Continuous and compact silver nanoparticles deposited on the surface of copper nanoparticles to form core-shell structure Cu/Ag bimetallic composite particles. They have a wide range of applications in conductive filler, catalysts, antibacterial medicine and other fields.Dopamine could occur oxidative polymerization generating poly (dopamine) to adhere on the surface of variety of substrate in the weak alkaline environment. The PDA layer structure contained catechol and nitrogen-containing groups, so it could be used as a good platform for secondary reactions. These groups had strong adsorption ability of many metal ions including silver ammonia ion. And utilizing poly (dopamine) itself weak reducibility to reduce metal ion to metal nanoparticles could form the catalytic activity sites. Under the effect of reducing agent, metal nanoparticles grew on the catalytic activity sites, forming continuous and compact metal shell. This study would first deposit poly (dopamine) on the surface of copper nanoparticles, and then electroless plating of silver performed on the as prepared Cu-PDA nanoparticles. The details of the work are as follows:This study first prepared Cu-PDA particles by poly (dopamine) layer deposition on the surface of the copper nanoparticles, the thickness of the poly (dopamine) layer was controlled. The catechol and nitrogen-containing groups present in the poly (dopamine) absorbed silver ammonia ions, and the weak reducibility of it reduced the silver ammonia ions into silver nanoparticles, forming catalytic activity sites. Adding glucose as the reducing agent, the silver ammonia ions existing in solution continue to reduce on silver nuclear growth into a dense silver layer, finishing the preparation of core-shell structure Cu-PDA/Ag bimetallic composite nanoparticles.We also studied the effect of dopamine deposition time, reaction temperature and the influence of heat treatment on dopamine layer, and the impact on the silver shell thickness of the concentration of AgNO3solution, pH of the solution, etc. The samples were characterized by XPS, TGA, SEM, XRD, and electrical conductivity. X-ray photoelectron spectroscopy (XPS) analysis the change of the elements on the surface before and after the modification of dopamine and silver plated copper nanoparticles, showed that poly (dopamine) and silver layer deposited on the surface of copper nanoparticles successfully. The morphology of the samples were investigated by scanning electron microscopy (SEM), showd that the silver particles coated on the surface of copper particles continuously and compactly. X-ray diffraction (XRD) analysis of the sample of crystal structure, proved that exists in the form of elemental silver. Thermogravimetric analyzer (TGA) characterized the thermal stability of the samples, and four point probe conductive proved the composite particles have very high electrical conductivity.By controlling the reaction conditions, such as reaction time, reaction temperature, concentration of AgNO3, heat treatment, etc, can control the thickness of poly (dopamine) layer and the silver shell of the composite nanoparticles. This method has mild reaction condition, simple process and the equipment requirements is not high, on the other hand, it is economic and pollution-free.