Application of Visible-Light Photosensitization to Form Alkyl-Radical-Derived Thin Films on Gold

Visible-light irradiation of phthalimide esters in the presence of the photosensitizer [Ru(bpy)₃]²⁺ and the stoichiometric reducing agent benzyl nicotinamide results in the formation of alkyl radicals under mild conditions. This approach to radical generation has proven useful for the synthesis of small organic molecules. Herein, we demonstrate for the first time the visible-light photosensitized deposition of robust alkyl thin films on Au surfaces using phthalimide esters as the alkyl radical precursors. In particular, we combine visible-light photosensitization with particle lithography to produce nanostructured thin films, the thickness of which can be measured easily using AFM cursor profiles. Analysis with AFM demonstrated that the films are robust and resistant to mechanical force while contact angle goniometry suggests a multilayered and disordered film structure. Analysis with IRRAS, XPS, and TOF SIMS provides further insights.