Tseng Wenjea J, Chuang Yi-Chen
Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan.
J Nanosci Nanotechnol. 2018 Apr 1;18(4):2790-2796. doi: 10.1166/jnn.2018.14351.
Bimetallic iron/silver (Fe/Ag) core/shell nanoparticles were prepared by chemical reduction from ferrous sulfate in the presence of sodium borohydride as a reducing agent in water, followed then by redox transmetalation with addition of silver nitrate (AgNO3) solution. When the reduction temperature was increased from room temperature to 85 °C, Fe nanoparticles with a reduced crystallite size ranging from 5.5 to 2.0 nm resulted. The particles changed from spherical to plate-like morphology as the temperature reached 85 °C. Addition of trisodium citrate was able to protect the precipitated Fe nanoparticles from oxidation; nonetheless, the citrate would facilitate chelation of the Fe clusters so that dense Fe aggregates with a mean diameter greater than 100 nm were found as the concentration of trisodium citrate exceeded 3.33 mM. A continuous Ag film was formed on the Fe surface by the redox transmetalation. This Ag film became a raspberry structure involving preferential deposition of particulate Ag on the Fe particles when the AgNO3 concentration exceeded 76.9 mM. Magnetic saturation was found to reduce with the increasing Ag concentration in the bimetallic composite nanoparticles.
通过在水中以硼氢化钠作为还原剂，从硫酸亚铁进行化学还原制备双金属铁/银（Fe/Ag）核壳纳米颗粒，然后加入硝酸银（AgNO₃）溶液进行氧化还原金属转移。当还原温度从室温升高到85°C时，得到了微晶尺寸减小至5.5至2.0nm的铁纳米颗粒。随着温度达到85°C，颗粒形态从球形变为片状。添加柠檬酸钠能够保护沉淀的铁纳米颗粒不被氧化；然而，柠檬酸盐会促进铁簇的螯合，以至于当柠檬酸钠浓度超过3.33mM时，会发现平均直径大于100nm的致密铁聚集体。通过氧化还原金属转移在铁表面形成了连续的银膜。当AgNO₃浓度超过76.9mM时，该银膜变成了一种覆盆子结构，涉及颗粒状银在铁颗粒上的优先沉积。发现双金属复合纳米颗粒中的磁饱和度随着银浓度的增加而降低。
