Page 18 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Chapter 1
small dimensions, the electric field distributions are changed. As a consequence, the plasma physical structures and the energy distribution of the species (e.g. electrons, ions, neutrals, and radicals) are also affected. In general, it employs beneficial properties of the atmospheric pressure gas discharge in microscale geometry for various plasma-enabled processes, resulting in a new and facile branch of applied plasma science.
Owing to its unique characteristics, a series of important, sometimes novel applications are being exploited with the development of the microplasma technology. Figure 1.1 illustrates several selected applications of microplasma that have been reported in recent years.68–72 Other applications like biomedical diagnostics,73 spectroscopic analysis 74 and dry-printing 75 were also reported and under development.
Figure 1.1 Important applications of microplasma. Reprinted with permission from [68] Copyright 2005 The Japan Society of Applied Physics. [69] Copyright 2012 The Japan Society of Applied Physics. [70] Copyright 2014 Elsevier. [71] Copyright 2009 American Chemical Society. [72] Copyright 2011 IOP Publishing
An emerging and promising application of microplasma is its use for nanomaterial synthesis. Several key advantages of microplasma-assited nanofabrication were summarized by Mariotti D and RM Sankaran: high pressure chemistry, continuous-flow, microreactor geometry and self-assembly/organization.76 From a cost efficiency standpoint, the atmospheric pressure operation of microplasmas allows saving of the significant costs associated with maintaining vacuum and using complex transfer chambers.77 From the process efficiency perspective, microplasmas are characterized by higher densities of radicals, resulting in higher rates of plasma-chemical reactions. Meanwhile, since the micro-scale geometry ensures a short residence time with a narrow residence time distribution (RTD) for precursors, the obtained nanoparticles are relatively smaller and have narrower size distributions compared with bulk plasma processes. In addition, the safety risks are cosiderably reduced when operating in micro-scale, especially when handling toxic materials. Based on these reasons, microplasma is becoming an emerging technique for nanofabrication, and a growing number of researches have been carried out in recent years focusing on its application in functional nanomaterial synthesis.
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