TOPICAL REVIEW: Microplasmas for nanomaterials synthesis

Microplasmas have attracted a tremendous amount of interest from the plasma community because of their small physical size, stable operation at atmospheric pressure, non-thermal characteristics, high electron densities and non-Maxwellian electron energy distributions. These properties make microplasmas suitable for a wide range of materials applications, including the synthesis of nanomaterials. Research has shown that vapour-phase precursors can be injected into a microplasma to homogeneously nucleate nanoparticles in the gas phase. Alternatively, microplasmas have been used to evaporate solid electrodes and form metal or metal-oxide nanostructures of various composition and morphology. Microplasmas have also been coupled with liquids to directly reduce aqueous metal salts and produce colloidal dispersions of nanoparticles. This topical review discusses the unique features of microplasmas that make them advantageous for nanomaterials synthesis, gives an overview of the diverse approaches previously reported in the literature and looks ahead to the potential for scale-up of current microplasma-based processes.