Introduction to Plasma Nanosynthesis
Nanomaterials have the potential to revolutionize many fields of science and technology, including electronics, chemical synthesis, energy storage, and environmental and pharmaceutical applications. However, commercial applications of nanomaterials require reliable, predictable, large-scale and low-cost synthesis. Synthesis by plasma and in plasma has the potential to satisfy these requirements, as well as to form improved nanomaterials [1-6]. Plasma synthesis offers the possibility of high throughput, short nanostructure growth time, low cost, and optimized material properties. These remarkable features of plasma synthesis are in great part due to the ability of plasma synthesis methods to sustain a higher yield production of nanomaterials both in volume and on surfaces, and often at lower process temperature and higher chemical purity, than conventional chemical synthesis . In this regard, synthesis by so-called non-equilibrium plasmas where plasma species, including, ions, electrons as well as atoms, are at different temperatures, is particularly attractive because it promises to sustain a non-thermal synthesis for a wide range of nanomaterials with high and low melting temperatures [3-8]. Control of production and transport of the plasma species during nucleation and growth of nanoparticles and nanostructures can potentially lead to a controllable synthesis of nanomaterials with desired structures and properties.
A critical obstacle toward these goals is the lack of understanding of plasma synthesis processes. This critical issue is also relevant to synthesis of nanomaterials by equilibrium thermal plasma techniques, which usually operate at atmospheric pressure and higher. Because such plasmas can produce larger plasma fluxes, they can provide larger synthesis yields than non-equilibrium low-pressure plasmas [7,9,10]. However, the limited control of much denser thermal plasmas results in a poorer selectivity of these synthesis methods as compared to synthesis techniques that utilize low-pressure plasmas [7,10].
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