Department of Interfaces, Max-Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Golm/Potsdam, Germany.
Small. 2010 Feb 22;6(4):545-53. doi: 10.1002/smll.200901623.
Alloyed gold/silver nanoparticles with a core/shell structure are produced from preformed gold and silver nanoparticles during ultrasonic treatment at different intensities in water and in the presence of surface-active species. Preformed gold nanoparticles with an average diameter of 15 + or - 5 nm are prepared by the citrate reduction of chloroauric acid in water, and silver nanoparticles (38 + or - 7 nm) are formed after reduction of silver nitrate by sodium borohydride. Bare binary gold/silver nanoparticles with a core/shell structure are formed in aqueous solution after 1 h of sonication at high ultrasonic intensity. Cationic-surfactant-coated preformed gold and silver nanoparticles become gold/silver-alloy nanoparticles after 3 h of sonication in water at 55 W cm(-2), whereas only fusion of isolated gold and silver nanoparticles is observed after ultrasonic treatment in the presence of an anionic surfactant. As the X-ray diffraction profile of alloyed gold/silver nanoparticles reveals split, shifted, and disappeared peaks, the face-centered-cubic crystalline structure of the binary nanoparticles is defect-enriched by temperatures that can be as high as several thousand Kelvin inside the cavitation bubbles during ultrasonic treatment.
在水和表面活性剂存在的情况下，通过在不同强度的超声波处理预形成的金和银纳米粒子，制备出具有核/壳结构的合金金/银纳米粒子。通过在水中用柠檬酸钠还原氯金酸制备平均直径为 15 ± 5nm 的预形成金纳米粒子，然后通过硼氢化钠还原硝酸银形成 38 ± 7nm 的银纳米粒子。在高超声强度下超声 1 小时后，在水溶液中形成了具有核/壳结构的裸露二元金/银纳米粒子。在 55 W cm(-2)的水中超声 3 小时后，阳离子表面活性剂涂覆的预形成金和银纳米粒子变成了金/银合金纳米粒子，而在阴离子表面活性剂存在下进行超声处理后，仅观察到孤立的金和银纳米粒子的融合。由于合金金/银纳米粒子的 X 射线衍射谱显示出分裂、移位和消失的峰，因此二元纳米粒子的面心立方晶体结构被富含缺陷，在超声处理期间空化泡内的温度可高达几千开尔文。
