Sonochemical Deposition of Nanoparticles on Spherical and Flat Surfaces

4 Sonochemical Deposition of Nanoparticles on Spherical and Flat Surfaces 

Metallic nanopartides were deposited on ceramic and polymeric partides using ultrasound radiation. A few papers report also on the deposition of nanomaterials produced sonochemically on flat surfaces. Our attention will be devoted to spheres. In a typical reaction, commerdally available spheres of ceramic materials or polymers were introduced into a sonication bath and sonicated with the precursor of the metallic nanopartides. In the first report Ramesh et al. [43] employed the Sto-ber method [44] for the preparation of 250 nm silica spheres. These spheres were introduced into a sonication bath containing a decalin solution of Ni(CO)4. The as-deposited amorphous clusters transform to polyciystalline, nanophasic, fee nickel on heating in an inert atmosphere of argon at a temperature of 400 °C. Nitrogen adsorption measurements showed that the amorphous nickel with a high surface area undergoes a loss in surface area on crystallization. 

In a few studies sonochemistry was used to coat polymers with nanosized par-tides [48-50]. Of these three reports one [50] dealt with metals, more specifically with noble metals (Pt, Pd, and Au). In this research, metal colloids are adsorbed to the surface of neutral functionalized polystyrene microspheres, PSMS. The authors report on the synthesis and characterization of catalytically important noble monometallic colloids using various chemical and sonochemical methods. These metal colloids are then adsorbed onto suitably functionalized PSMS. The metal-immobilized microspheres are reacted with a linker such as 4-mercaptobutyl phosphonic acid and subsequently used to grow multilayers. 

It can be seen that the level of deposition has been improved and we are currently able to create a very smooth coating of a monolayer of nanoparticles on the surface. This was achieved by a gradual reduction of the silver concentration, thus 

Papadimitrakopoulos and coworkers reported on transparent Si/ SiOx nanocomposite films, spontaneously adsorbed on glass or quartz substrates from their colloidal suspensions via a sonication-assisted oxidation process [56]. Individual nanosilicon partides (ca. 20 nm) appear to cover a significant part of the substrate along with agglomerates of the order of 50-80 nm in thickness. Kinetic studies indicate a rapid initial adsorption that slows down significantly after 3 h. 

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