Preparation And Properties Of Silver Nanoparticles Colloids

In this paper, a green method has been developed to synthesize silver nanoparticles and the corresponding colloids. The influences of reaction parameters on its morphology, size and antibacterial property, stable property and cytotoxicity have been investigated systematically. The main contents and results of this research were as follows:(1) Without any stabilizing agents, a facile synthesis of silver nanoparticles colloid has been conducted in aqueous solution using the reduction of silver nitrate by maltose. The synthetic parameters, such as temperature and amount of ammonia in the reaction system, have important influenced on the size of the silver nanoparticles. The results showed that silver nanoparticles were dispersed well in aqueous solution between 20℃and 40℃, and agglomerated at 60℃and 80℃. When the adding amount of ammonia was 0.1ml, silver nanoparticles with an average diameter of 20nm and narrow size distribution were prepared. When the amounts of ammonia were 0.7ml and 0.4ml, the diameters of silver nanoparticles increased to 30nm and 40nm, respectively. The adding sequences of the reaction reagents have impacted the significant influence on the size of the silver nanoparticles, ex., the diameter of Ag nanoparticles within 30-50nm can be obtained by changing the adding sequence of the reactants. Under the same experimental condition, the diameter of Ag nanpopartilces maintained the same when enlarging the reaction volume from 200ml to 5000ml. All the results showed that our experimental procedures had an excellent repeatability.(2) The prepared Ag colloid was stable for several months without any stabilizing agents. The high-temperature (60℃) test showed that the color of solution changed form yellow-brownish to gray after five days. During the illumination experiment, the color of solution correspondingly changed with time. The colloid was stable for ten days at 40℃. After stored at room temperature for 18 months, the silver nanoparticles in the colloids have not any changes in comparison with the as-prepared sample. The colloids can be stored in transparent bottle at room temperature, which isn't stored in refrigeration or in dark.(3) Using E.Coli as a probe to compare the antibacterial property of the prepared silver nanoparticles and the clinic sulfadiazine silver powders, the results show that silver nanoparticles have a better antibacterial effect than that of sulfadiazine silver. MIC of silver nanoparticles is 1.25μg·ml-1. After high- temperature (60℃) and illumination experiment, the antibacterial effect of solution decreased. The antibacterial effect of Ag colloids stored at room temperature are the same as that of the colloids stored at 4℃.(4) The cytotoxicity of Ag colloids to HeLa cells was investigated by MTT assay. The results show that all the tested samples gave rise to one-grade cytotoxicity, which was mild cytoxicy. The higher the concentration of the Ag colloid is, the lower rate of cell proliferation is and then the higher cytotoxicity of silver nanopartciles is. The cytotoxicity of the silver colloids depends on the dose of Ag nanoparticles.