Biofouling Properties of Nitroxide-Modified Amorphous Carbon Surfaces

Amorphous carbon films exhibit attractive optical and surface properties. In this work, modified amorphous carbon films incorporating nitroxide groups (α-CNO) have been obtained by searching for a condensed analogue to classical soft antifouling materials. Thin films deposited by reactive magnetron sputtering in air discharges at varying power conditions were characterized by ellipsometry, atomic force microscopy, and water contact angle. Plasma power was observed to activate the densification and roughness of nanograined films. Most hydrophilic films deposited at 30 W exhibited the lowest refractive index, negligible optical absorption in the vis-IR, and presented a close to stoichiometric C₂NO composition, as derived from X-ray photoelectron spectroscopy. Micropatterns prepared by photolithography validated the transparency-hydrophilicity of the α-CNO, as observed by water condensation contrast imaging. An albumin adsorption experiment evaluated through fluorescence revealed that α-CNO behaves as antifouling with respect to Si. Such thin antifouling films are of interest for the initiation of immobilization cascades in imaging surface plasmon resonance, where they have confirmed their antifouling contrast enhancement role. These results illustrate that the combination of a nanorough surface with nitroxide chemistry induces an antifouling behavior. In association with the optical transparency, the results invite the exploration of the bioengineering dimension of α-CNO films.