Figure 7.

Representative optical reflectance spectra of (a) undecanoic acid-modified porous Si and (b) ozone-oxidized porous Si before and after 8 days in cell culture. Electrochemical anodization of the Si wafer produces a film uniform and thin enough to display Fabry-Perot interference fringes. After 8 days in cell culture, the optical spectrum of the undecanoic acid-modified sample indicates a moderate degree of oxidation and/or dissolution, while the ozone-oxidized sample has degraded to the point that thin film interference can no longer be observed