Antimicrobial Studies of Black Silicon and Black Diamond Using Gram‐Positive Bacteria

Herein, it is investigated if black diamond is useful in a bactericidal surface. Black diamond is derived from black silicon, a silicon surface structured into nanosized needles. Black diamond is obtained by coating black silicon with a thin diamond film, rendering the nanostructures more robust. The bactericidal and antibacterial properties of fluorine‐terminated and hydrogen‐terminated black diamonds with those of black silicon and for flat surfaces of diamond (on silicon) with the same terminations are studied. The ability to repel and kill Gram‐positive Staphylococcus aureus and Staphylococcus epidermidis is evaluated, which have a thicker cell wall and are more mechanically robust than the bacteria that are studied before. The initial adhesion as well as long‐term 24 h biofilm formation is studied. The number of bacteria that initially adhere to the fluorine‐terminated black diamond surface is reduced and has the highest dead bacterial ratio. Biofilm formation after 24 h shows that while all surfaces outperform glass over the long term, diamond‐coated surfaces with both fluorine and hydrogen termination have a significant inhibiting biofilm formation effect. In conclusion, fluorinated and hydrogenated diamond‐coated surfaces with and without nanoneedles have repelling, bactericidal, and biofilm‐inhibiting effects on Gram‐positive bacterial strains and are promising antimicrobial surfaces.