Advances in laser-assisted conversion of polymeric and graphitic carbon into nanodiamond films

Nanodiamond (ND) synthesis by nanosecond laser irradiation has sparked tremendous scientific and technological interest. This review describes efforts to obtain cost-effective ND synthesis from polymers and carbon nanotubes (CNT) by the melting route. For polymers, ultraviolet (UV) irradiation triggers intricate photothermal and photochemical processes that result in photochemical degradation, subsequently generating an amorphous carbon film; this process is followed by melting and undercooling of the carbon film at rates exceeding 10⁹K s^-1. Multiple laser shots increase the absorption coefficient of PTFE, resulting in the growth of 〈110〉 oriented ND film. Multiple laser shots on CNTs result in pseudo topotactic diamond growth to form a diamond fiber. This technique is useful for fabricating 4-50 nm sized NDs. These NDs can further be employed as seed materials that are used in bulk epitaxial growth of microdiamonds using chemical vapor deposition, particularly for use with non-lattice matched substrates that formerly did not form continuous and adherent films. We also provide insights into biocompatible precursors for ND synthesis such as polybenzimidazole fiber. ND fabrication by UV irradiation of graphitic and polymeric carbon opens up a pathway for preparing selective coatings of polymer-diamond composites, doped nanodiamonds, and graphene composites for quantum computing and biomedical applications.