Surfactants in novel technologies

In the late eighties, the new field of nano-technology, began to develop [284]. Considering the data presented in [284 - 287] and [41, pp. 227 - 265], the following main conclusions can be made. Nano-particles are small atomic clusters of 10 - 1000 atoms, which exhibit properties between the molecular and micro-heterogeneous size limits, and may contain crystalline, amorphous and quasi-crystalline phases. The microemulsion method is one of the novel techniques for the synthesis of nano-particles due to the ability of microemulsions to solubilise substances which are insoluble in both polar and apolar media [284]. 

Compared with coarse-grained materials, nano-particles can possess unique electronic, magnetic and optical properties. The main principle of producing nano-particles with microemulsions consists in mixing two types of microemulsions, i.e. o/w and w/o microemulsions. In this way, for example, ultra-fine particles are obtained, whose core and external shells consist of Fe salts, and in the intermediate layer copper is contained. To produce microemulsions, anionic surfactants such as Aerosol OT (AOT) are used, one mole of which can solubilise up to 8 moles of the aqueous phase. 

A method to obtain nano-particles at air/water interfaces has been described in [287]. Spreading of surfactant-coated metallic, semi-conducting, magnetic and ferroelectric nanoparticles on water surfaces results in the formation of monoparticulate thick films which then can be transferred, layer by layer, to solid substrates. These films can find potential applications in advanced electronic and electro-optical devices. Here and further, we give only typical examples of using surfactants in novel technologies. A more detailed description can be found in a new edition of Surfactants Science Series [288]. 

The recovery of metal ions from rinse solutions is important in electroplating. It has been shown in [291] that nickel ions can be recovered using a liquid surfactant membrane (LSM) obtained on the basis of di(2-ethylhexyl) phosphoric acid. The LMS permeation by nickel ions (external phase) is affected by the membrane viscosity which depends on the surfactant concentration. 

Surfactants improve the effectiveness of using conducting silver powders for screen printing [292]. Caprylic acid and triethanolamine were used as surfactants. The pastes obtained after the treatment with surfactants demonstrate a good effectiveness which increase with the surface 

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