Study On Fast Synthesis And Influencing Factors Of Nano Silver By Microwave Heating

Nano silver materials are attracting more and more attention due to their excellent physical and chemical properties, such as small size effect, surface effect, macroscopic quantum tunneling effect, etc. And they have been widely used in the fields of catalysis, consumer electronics and biomedical.The size and morphology of nano silver have significant effect on their performance. So precisely control the particle size and morphology is the key to prepare high performance nano silver materials. Microwave-assisted method is a new technique for the synthesis of nanomaterials. Compared with traditional methods, it has unparalleled advantages, such as strong penetration ability, uniform heating, fast, simple, high efficient and clean.In this paper, we introduced a creative microwave-assisted method to synthesize nano silver materials with different morphology and size by using silver nitrate as silver precursor, PVP as capping agent, sodium sulfide or sodium chloride as control agent, ethylene glycol as reducing agent and solvent, and microwave as heating source. Then we uesd UV-Vis, XRD, SEM, TEM to characterize the synthesized nano silver. By changing reaction conditions and the ratio of reactants to find the factors that affect the morphology and particle size of nano silver. The main contents include the following aspects:(1) Preparation of silver nanowires: with sodium chloride as control agent and microwave as the heating source,we discussed different factors(microwave power, reacting time and temperature, concentration of NaCl, mass ratio of AgNO3 and PVP) on the formation of silver nanowires. Ultimately we achieved the optimal preparation process: microwave power=300 W; T=190 oC; t=4 min; mass ratio of AgNO3 and PVP=1:2.5; concentration of NaC l=2.5 mM. On this basis, we processed highly pure, well distributed silver nanowires with diameter about 40 nm and length about 15 μm and further explored the growth mechanism of silver nanowires.(2) Preparation of silver nanocubes: through microwave-assisted method, we use sodium sulfide as control agent. By changing concentration of Na2 S, mass ratio of AgNO3 and PVP, reacting time and temperature, we came up with the optimal preparation process: microwave power=300 W; T=180 oC; t=4 min; PVP=0.68 g; AgNO3=0.17 g; concentration of Na2S=375 μM. On this basis, we processed pure silver nanocubes and further explored the growth mechanism of silver nanocubes.(3) Preparation of silver nanoparticles with high concentration: for the weak reducibility of polyols and high reaction efficiency of microwave heating, we combine the two methods to synthesize silver nanoparticles. By discussing different factors(reacting time and temperature, concentration of Na2 S, mass ratio of AgNO3 and PVP) on the formation of silver nanoparticles, we could prepare high concentration of 0.5 M, small size(<10 nm), narrow size distribution(2-6 nm) silver nanoparticles in less than 10 minutes which is much quicker than other traditional methods.