Antibacterial, mechanical and surface properties of Ag-DLC films prepared by dual PLD for medical applications.

Silver doped diamond-like carbon layers were deposited by dual pulsed laser deposition using two KrF excimer lasers. The concentration of Ag, determined by XPS and WDS, moved from zero to ~10at%. We found that the sp2/sp3 ratio, film roughness and the number of droplets (SEM and AFM) increased with increasing silver concentration. The sp3 content measurement (XPS) was influenced by ion cluster surface sputtering and varied from 71.0% (undoped DLC) to 36.2% (for 9.3at% Ag). Transmission was measured on the scale from 200nm to 1100nm, and decreased with increasing silver content. An increase of Ag content has an effect on the decrease of the storage modulus (E') and the indentation hardness (HIT). The highest values HIT=51.9GPa and E'=270.6GPa were measured on a sample with 0at% Ag. The lowest values HIT=26.0GPa and E'=180.2GPa were measured on a sample of 9.3at% Ag. Film adhesion was studied using the scratch test and was up to 20.8N for the highest Ag concentration. The contact angle (CA) measurements for water showed that the CA of Ag-DLC films was higher (78°-98°) that of DLC film (77°). The surface free energy of DLC and of Ag-DLC was about 40mJ·m-2. Antibacterial properties were studied using gram positive and gram negative bacteria. The antibacterial effects increased with the Ag concentration and were ~99.9% after 24h for the layers with the highest silver content (9.3at%). Our results demonstrate that the Ag-doped DLC films are potentially useful biomaterials having both good mechanical properties and antimicrobial characteristics. PRIME NOVELTY STATEMENT: Unique manufacturing technique dual pulsed laser deposition was applied on hydrogen-free diamond-like carbon doped by Ag including topological, physical and antibacterial characterization.