Transport of Nanoparticles in Gases: Overview and Recent Advances

Nanoparticles play a major role in industrial processes and natural phenomena in a variety of fields including chemical engineering, chemistry, physics, public health and biology. Nanoparticles are suspended in fluids during production, handling, processing, and by unintentional and/or undesirable release to the environment. In many cases the suspending fluid is a gas, as for example in large scale production, air pollution, clean room applications and many more. The small size of nanoparticles makes it possible to compare their transport properties to the fluid itself. Brownian particle diffusion is one of the most important mechanisms leading to significant transport rates. Diffusion is well known in mass transfer, however, differences arise because of the wide spectrum of nanoparticle sizes and their morphology (aggregate structure) − a concept understood in particle science and technology but needed in many diverse fields of nanoparticle applications. Nanoparticle transport can be controlled by external force fields because these forces may act exclusively on the nanoparticles and have negligible effects on fluid molecules. These include thermophoresis and forces in electrical fields.