Mechanism for the plasma oxidation of wool fiber surfaces from XPS studiesof self-assembled monolayers

The O-2 plasma treatment of self-assembled monolayers (SAMs) of octadecyl m ercaptan on gold substrates was investigated as a model for the oxidation o f wool fiber surfaces. Three controlled low-pressure gas-plasma treatments were employed in which the active species were (i) atomic oxygen, (ii) atom ic oxygen plus vacuum UV radiation, and (iii) full plasma treatment (charge d particles in addition to the above). X-ray photoelectron spectroscopy rev ealed that the plasma treatments differ from each other in the extent of ox idation and etch rate with the full plasma treatment being the most aggress ive plasma. The results have confirmed that the charged particles present i n a full O-2 plasma treatment are responsible for rapid etching of the orga nic surface and thus play a significant role in the oxidation mechanism due to radical formation during this process. Vacuum UV radiation also contrib utes to the oxidation process. Only short plasma treatment is necessary for the oxidation of the lipid layer and the SAM is a suitable model for this process. (C) 2001 John Wiley & Sons, Inc.