Study On Preparation And Stability Of Nano-silver

Nano-silver had important applied value in some fields such as new catalyst,sterilizing material,electronic paste and so on,and it was of great value to study the preparation of nano-silver with mild conditions and simple process.Nano-silver was prepared by reduction method of polyvinylpyrrolidone and extraction of Ixeris denticulata,and the effect of preparation conditions on the particle size and stability of nano-silver was investigated.Nano-silver was prepared with glycerol as solvent,PVP as reducing agent and AgNO3 as precursor,and formation and growth process of nano-silver was traced by UV-visible spectrum.The effect of adding water,alkali and glucose on the particle size and stability of nano-silver in the reaction mixture was investigated.The results showed that adding a small amount of water could accelerate the formation rate of nano-silver,and the stability of nano-silver water dispersions would be better.With the increase of water content,the particle size of nano-silver becomes larger and the concentration became lower.The addition of alkali can accelerate the formation rate of nano-silver,at the same time the particle size and concentration of nano-silver became larger slightly.The nano-silver was stable in the mixed solution,but it sank after separating and dispersing in the water.The particle size of nano-silver remained unchanged after adding glucose,while the stability and concentration increased.The nano-silver prepared with polyvinylpyrrolidone reduction method at 100? for 1h,was obtained with average particle size 20nm.The morphology of nano-silver was approximately spherical,and the dispersity was better.Nano-silver was prepared with extraction of Ixeris denticulata as reducing and coating agent,AgNO3 as precursor,and the formation and growth process of nano-silver was traced by UV-visible spectrum.The study of the particle size and stability of nano-silver was affected by the concentration of AgNO3,reaction time,temperature,pH,extract of Ixeris denticulata content,concentration of chloride ion,surface active agent.The nano-silver was characterized by transmission electron microscopy,X-ray diffraction and infrared spectroscopy.The results showed that the characteristic absorption peaks of nano-silver were red shifted and the absorbance increases with the increase of AgNO3 concentration.With the extension of reaction time,the characteristic absorption peak of nano-silver shifted red shifted slightly and the absorbance increased gradually.The higher the temperature was,the bigger the concentration and the reaction rate of nano-silver.However,the turbidity of the reaction mixture increased because of the secondary macromolecule substance reacting each other in the extraction of Ixeris denticulata.The size distribution of nano-silver was the most homogeneous in pH=6.8.With the increase of the content of Ixeris denticulata extract,the concentration and the stability of nano-silver increased,but the effect was also enhancing on nano-silver with the chloride ion originate from Ixeris denticulatain extract.In the case of constant extraction,it was found that the trace of Cl-(40ug)had little effect on the preparation of nano-silver.The size of the nano-silver was larger with the increase of Cl-content,while the concentration of nano-silver was reduced and the stability of nano-silver was weakened,at the same time the aggregation phenomenon appeared and the turbidity of the solution increased.The formation rate of nano-silver was accelerated by adding sodium sixteen alkyl benzene sulfonate,but the particle size of the nano-silver became larger and the stability weakened.The turbidity of the system increased with the adding of sixteen alkylbenzene sulfonate,so it had negative effects on the preparation and stability of nano-silver.The addition of twelve sodium alkyl sulfate made the particle size of nano-silver smaller,and made the concentration reduced.Triton X-100 in different contents had almost no effect on the preparation of nano-silver,while Triton X-100 had synergistic effect on the stability of nano-silver.The analysis of transmission electron microscope of nano-silver showed that most of the morphology of nano-silver was spherical and only a few was clavate structures.The particle size of nano-silver was 20nm and the nano-silver was in good dispersibility.The X-ray diffraction analysis showed that the crystal type of nano-silver prepared with the extract of Ixeris denticulata was a face centered cubic structure.The infrared spectraanalysis showed that the phenols,amino acids,fats and aromatic groups in the extract played a reductive and protective role in the preparation of nano-silver.