were measured by nanoindentation for these films. Importantly, even at nanodiamonds concentrations upto 20 wt.% the films remain optically transparent while strongly absorb the UV radiation. This study has signify that nanodiamonds –polymer, nanofibers with very high ND content (up to 80 wt.%) can be formed by electrospinning. At high concentration of nanodiamonds the composite fibers act as ceramic fibers, in particular, indicating the brittle failure typical for ceramic materials, with no necking or crazing, that are typical for pure PAN or CNT-containing PAN nanofibers176. A pronounced agglomeration of nanodiamonds observed at higher concentrations shows that characteristics of these composites can be even higher when dispersion of nanodiamonds is enhance. These nanodiamonds –polymer films are favourable candidates for optically transparent UV absorbing scratch- and wear resistant coatings and paints, and indicate that nanodiamonds could be used to squash the photoaging of polymers177. For coatings specifically, a strong adhesion between the substrate and the coating composite film is needed. Nanodiamonds can improve the adhesion through creating nano-roughness at the coating-substrate interface, as well as through other mechanisms. A remarkable upgrade adhesion of the Nylon-11 coating to steel due to the addition of 7 wt.% purified nanodiamonds has been reported, further underlined the potential of nanodiamonds in polymer-based coatings and paints178. In various studies nanodiamonds have shown to be non-toxic and biocompatible, which give it an excellent material for biomedical applications. Most polymer synthesized for such applications, in particular biodegradable polymers, suffer from poor mechanical properties, sharply limiting their potential for the replacement of metals in applications such as bone fracture fixation179.
Various studies have explore the use of nanodiamonds to reinforce polyvinyl alcohol (PVA), which is used in soft tissue replacing, artificial cartilage, skin, pancreas, as well as catheters and hemodialysis membranes, and a number of other biomedical applications. A 40% enhanced tensile modulus and a 70% larger fracture energy were measured due to the addition of 1 vol.% of nanodiamonds -carrying detonation soot purified by treatment with o-xylene to remove adsorbed organics180. The noticed enhancement were described by favorable interactions between oxygen-containing groups (including COOH, C-O and alike), reveal on the surface of nanodiamonds-containing soot and OH groups of PVA. It is likely that removal of adsorbed hydrocarbons and other weakly bonded species from the surface of nanodiamonds containing soot by boiling it in o-xylene accelerate weak interactions (mainly hydrogen bonding) between these groups and the functional