Nanostructured DLC-Ag composites for biomedical applications

We have synthesized novel diamondlike carbon coatings with silver nanoparticles embedded into the DLC film. The size of silver nanoparticles that are confined into layered structures has been varied from 5 nm to 50 nm using an ingenious pulsed laser deposition technique. The size of nanoparticles was found to be remarkably uniform within 15%. We have characterized these samples using high-resolution cross-section TEM and STEM-Z contrast techniques, electron energy loss spectroscopy (EELS), Raman, nanohardness, adhesion, and biocompatibility measurements. In the STEM-Z, where the contrast is proportional to atomic number, we have obtained the details of the atomic structure of silver particles. We have correlated the microstructure with hardness and adhesion properties. The EELS was used in conjunction with STEM-Z to obtain sp /sp bonding ratio. This ratio was compared with Raman result to provide an average bulk value. The role of silver nanoparticles is surmised to provide a reservoir of electrons for antimicrobial activity on the surface, as revealed by our biocompatibility tests.