X-Ray photoelectron spectroscopy as a tool in the study of nanostructured titanium and commercial pet surfaces in biotechnological applications

In this Chapter, two case studies are presented. In the first study, XPS was used to identify the oxidation states of titanium in nanostructured titanium films on titanium surfaces fabricated by different polishing (mechanical and chemical) and sputtering techniques. A layer of titanium dioxide was detected on both substrates, forming a protective passive film. The physiochemical and dielectric properties of this film determine the biocompatibility of titanium when used in the manufacture of medical implants. When formed in aqueous solution, air, or other oxygen-containing environments, the oxide layer is normally only a few nanometres thick and consists essentially of titanium dioxide. However, by varying the sputtering conditions, other chemical states of titanium oxide can be formed, such as Ti₂O₃ and TiO. Carbon was detected on all surfaces, at various levels ranging from 11% to 30%. Carbon has been shown to be a commonly encountered contaminant in similar studies. In the second study, XPS was used to investigate the bacterial modification of the surfaces of poly(ethylene terephthalate) (PET) bottles exposed to bacterial enrichment culture over a nine month period. Four elements, two carbon species, two oxygen species, and one nitrogen species were detected on the modified surface that were not detected on the reference surface, and two elements present on the reference surface were not detected on the modified surface. As was found in the analysis of the titanium surfaces, some carbon contamination was detected, however as carbon is the primary element in the polymer chains, it is difficult to evaluate the exact nature and extent of contamination.