The term sonication refers to applying sound energy to a solution to agitate insolubilised or suspended particles. When the frequency of sonication is above 20 kHz it is often referred to as ultrasonication. There are ultrasonic baths and ultrasonic processors, which as you say are used both to de-aggregate nanoparticles and to produce them by top-down processes. Here are several articles where you can see protocols for nanoparticle synthesis with an ultrasonic processor:
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