Ultra-small photoluminescent silicon-carbide nanocrystals by atmospheric-pressure plasmas

This work was supported by the Royal Society International Exchange Scheme (IE120884), the Leverhulme International Network (IN-2012-136), EPSRC (EP/K022237/1 and EP/ M024938/1) and EU-FP7 (award n.606889). S. A. and A. U. H. thank the financial support of the University of Ulster Vice- Chancellor Studentship and EU-funded ITN, respectively (award n.606889). IL and KO acknowledge financial support from CSIRO and Australian Research Council. I. L. acknowledges support from the School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology.Highly size-controllable synthesis of free-standing perfectly crys- talline silicon carbide nanocrystals has been achieved for the first time through a plasma-based bottom-up process. This low-cost, scalable, ligand-free atmospheric pressure technique allows fabri- cation of ultra-small (down to 1.5 nm) nanocrystals with very low level of surface contamination, leading to fundamental insights into optical properties of the nanocrystals. This is also confirmed by their exceptional photoluminescence emission yield enhanced by more than 5 times by reducing the nanocrystals sizes in the range of 1–5 nm, which is attributed to quantum confinement in ultra-small nanocrystals. This method is potentially scalable and readily extendable to a wide range of other classes of materials. Moreover, this ligand-free process can produce colloidal nano- crystals by direct deposition into liquid, onto biological materials or onto the substrate of choice to form nanocrystal films. Our simple but efficient approach based on non-equilibrium plasma environment is a response to the need of most efficient bottom-up processes in nanosynthesis and nanotechnology.PostprintPeer reviewe