Photochemical grafting reactions of a benzophenone-containing alkanethiol monolayer on au with deuterated polystyrene

Photochemical reactions of 4-[(10-sulfanyldecyl)oxy]benzophenone with deuterated polystyrene (PS-d8) were studied using Fourier-transform infrared (FT-IR) spectroscopy and vibrational sum frequency generation (VSFG) spectroscopy. The FT-IR spectral changes of PS thin films indicated that exposure to ultraviolet (UV) light caused photochemical consumption of the benzophenone moiety by a hydrogen abstraction reaction of the carbonyl group; the reaction was almost complete at an exposure energy of 2.0 J cm-2 at 254 nm. The VSFG spectral changes of the adsorbed monolayer on Au on UV exposure revealed that the carbonyl groups oriented parallel to the Au substrate surface were consumed at more exposure energies. The exposure-energy-dependent formation of PS-grafted layers was confirmed by atomic force microscopy observations of Au surfaces modified with a photoreactive monolayer.