琥珀酸二异辛酯磺酸钠微乳体系中纳米银的制备及其连续相的影响

在琥珀酸二异辛酯磺酸钠(AOT)为表面活性剂、环己烷为连续相形成的微乳体系中, 利用水合肼还原AgNO₃制备了分散性良好的纳米银. 利用紫外-可见(UV-Vis)光谱和透射电镜(TEM)对所得产物进行了表征, TEM显微图像表明形成粒子为球形结构, 平均粒径为5.10 nm, 标准偏差为2.84 nm. 分别利用正己烷、正庚烷、正辛烷、环己烷和十二烷等作连续介质, 研究了微乳液中连续相对纳米银形成的影响. 随着正烷烃碳链长度的增加, 微乳液中胶束之间的交换速率增大, 形成粒子的平均粒径逐渐减小. 十二烷形成的微乳体系制备的纳米银溶胶具有最宽的共振吸收峰, 所得的纳米银粒子平均粒径最小. 环己烷形成的微乳液中反胶束具有特殊的界面强度, 导致纳米银晶核的形成速率过低, 纳米银晶粒的生长不完全.

Preparation of Silver Nanoparticles and Effect of Continuous Phases in Sodium Bis(2-ethylhexyl)sulfosuccinate Microemulsion

Silver nanoparticles were synthesized in water-in-oil microemulsion using sodium bis(2-ethyl- hexyl)sulfosuccinate (AOT) as a surfactant, silver nitrate solubilized in the water core of one microemulsion as a source of silver ions, hydrazine hydrate solubilized in the water core of the other microemulsion as a reducing agent. Ultraviolet-visible spectrum was used for confirming the formation of silver nanoparticles and evaluating the effect of continuous phases. Transmission electron microscopy (TEM) was also used for elucidating the structure of the resultant particles. TEM micrographs confirm that the nanoparticles prepared in AOT-cyclohexane microemulsion are all spherical with mean diameters of 5.10 nm and standard deviation of 2.84 nm. The effect of various continuous phases in the microemullsion, such as hexane, heptane, octane, cyclohexane and dodecane, on the formation of silver nanoparticles was investigated. On increasing the chain length of alkanes, the exchange rate coefficient increases, that is to say, the exchange rate between reverse micelles increases. As a result, the average diameter of the silver nanoparticles decreases correspondingly. Comparing to the microemulsion formed in alkanes with short chain lengths and cyclohexane, the plasma resonance of silver sol prepared in AOT-dodecane microemulsion has the broadest absorption peak, indicating that the average size of the particles formed in this microemulsion is smaller than that of the particles formed in other microemulsions. The micelles formed in AOT-cyclohexane microemulsion have a special interfacial rigidity, and thus the formation rate of silver nucleation decreases remarkably. As a result, the growth of the silver nanocrystals may be incomplete and the plasma resonance of the silver nanoparticles displays an absorption peak with a lower absorption intensity and broader absorption band.