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Abstract

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 ± 5 nm are prepared by the citrate reduction of chloroauric acid in water, and silver nanoparticles (38 ± 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 water solution after one hour of sonication at high ultrasonic intensity. Cationic surfactant-coated preformed gold and silver nanoparticles become gold-silver alloy nanoparticles after three hours of sonication in water at 55 W cm-2, while 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 splitted, shifted and disappeared peaks, the face centered cubic crystalline structure of binary nanoparticles is defect enriched by the temperatures which can be as high as several thousand K inside the cavitation bubbles during ultrasonic treatment.