Nanofabrication by thermal plasma jets: From nanoparticles to low-dimensional nanomaterials

Current fabrication of nanomaterials is facing the following two challenges: high selectivity toward specific chemical compositions or morphologies and their scalable production. This usually requires new extreme fabrication conditions beyond the conventional approaches. Thermal plasma jets are flows of partially ionized gases where gas and electron temperatures reach their equilibrium state around 10 000 K, and thus provide high fluxes of energy and chemically active species including electrons and ions with their strong spatial gradients. Such extreme environments can trigger reactions that are not thermodynamically favorable or require high activation barriers, leading to the production of materials with exotic chemical compositions or structures. Since their first operation in 1960, thermal plasma jets were soon recognized as a unique and effective medium for material transformation such as melting, vaporization, and pyrolysis and recently have also found their important applications in nanomaterial fabrication. In this Perspective, we briefly review the latest progress in the thermal plasma jet-assisted fabrication of nanomaterials from nanoparticles to low-dimensional nanostructures. A special focus is made on the advantages of the thermal plasma jet technology in nanostructure fabrication, discussing plasma properties responsible for the nanomaterial growth with high throughput, high purity, anisotropy, desired compositions, or narrow size distributions. This Perspective closes with an outlook of challenges and opportunities for further advancement in this emerging field.