Effect of Irradiation of Ultrasound on Formation of Metal Nanoparticles

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The preparation technique of ultrafine particles is one of the important and elemental technologies for the nanotechnology. New methods for preparing nanoparticles are seeking for the functional properties and mono size of particles and a preparative procedure using ultrasonic energy is one of new methods. In this study, the gold nanoparticles were mainly prepared in ultrasound field, and the effect of clay gel on the sonochemical reaction was also examined.At first, new methods for the particle size analysis were established, which were using a small angle X-ray scattering method and a light absorbance method combined with Mie theory.The gold nanoparticle was prepared from chloroauric acid aqueous solution using alcohol or surfactant as a radical source in the ultrasound field of 200 kHz. The good condition to prepare gold nanoparticles was in the neutral solution of pH. In general, the reaction rate increased with the carbon chain of the alcohol, but the rate was extremely slow at pH higher than 10 with the long carbon chain of the alcohol. When the ultrasonic wave was 600 kHz, the results were almost same as those at 200 kHz. On the other hand, the preparation rate of gold nanoparticles at 20 kHz ultrasound increased with pH values and the carbon chain of the alcohol.The reaction rate in the solution dispersed clay particles was slower than the case that clay gel was not contained, and the particle size distribution also extended. Although the particle size was not smaller than that expected, the nanoparticles dispersed well.