Effect of Irradiation of Ultrasound on Formation of Metal Nanoparticles

超细颗粒的制备技术是纳米技术的重要基础技术之一。制备纳米粒子的新方法是追求纳米粒子的功能特性和单一尺寸，利用超声能量制备纳米粒子是其中一种新方法。本研究主要在超声场下制备金纳米粒子，并考察了粘土凝胶对声化学反应的影响。首先，建立了小角x射线散射法和结合Mie理论的光吸收法两种粒径分析方法。以氯金酸水溶液为原料，以乙醇或表面活性剂为自由基源，在200 kHz超声场下制备金纳米颗粒。制备金纳米粒子的最佳条件是在pH为中性的溶液中。总的来说，随着醇碳链的增加，反应速度加快，但当pH大于10时，醇碳链较长，反应速度极慢。当超声波为600 kHz时，结果与200 kHz时基本相同。另一方面，在20 kHz超声下，金纳米颗粒的制备速率随着pH值和醇碳链的增加而增加。分散粘土颗粒的溶液中反应速度比不含粘土凝胶的情况慢，粒径分布也扩大。虽然颗粒尺寸并不比预期的小，但纳米颗粒分散良好。

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.