A top-down processing of diamond microcrystals, which are less prone to amorphization and vacancy loss, would provide a more industrially scalable route. However, in this case two barriers have to be surmounted the difficulties of irradiating large amounts of material and converting microdiamonds into nanocrystals while keeping both fluorescence properties and crystal structure intact.
In a recent study, which is published in Nanotechnology, researchers in France and Germany have explored with success this alternative route to producing homogeneous samples of pure and very small fluorescent diamond nanoparticles with high yield. The fabrication procedure starts with the irradiation of finely controlled micron-size diamonds and requires subsequent milling and purification steps. In this novel process, substitutional nitrogen-containing microdiamonds with defined atomic composition were irradiated using a high-energy electron beam and then annealed at high temperature (800 C) to create the desired photoluminescent centres in an intact diamond lattice. An original two-step milling protocol was designed to convert the fluorescent microdiamond into very small (down to 4 nm) round-shape nanoparticles of highly pure sp3 diamond with very bright and stable photoluminescent centres.
Such a fine fabrication process can now be used for the large-scale production of fluorescent diamond nanoparticles. One can vary and tailor their properties via the composition of the starting material to answer the needs of future applications. These fluorescent diamond nanoparticles open realistic perspectives to very long term labeling, to quantitative biology and innovative nanotechnology applications in composites, optoelectronics or analytical chemistry.
|Contact: Patrick Curmi|
INSERM (Institut national de la sant et de la recherche mdicale)