Patterning Surfaces through Photografting of Iodonium Salts

A gold surface immersed in an aprotic iodonium salt solution containing a photosensitizer is patterned by irradiation with a blue light through a mask. The photochemical behavior of three photosensitizers in the presence of (4-nitrophenyl)(2,4,6-trimethylphenyl)iodonium triflate I is fully characterized [luminescence quantum yield ΦL and lifetime τL, quenching rate constant (kq), ΔG°, and quantum yield (ΦR)]. The key species for the surface modification are aryl radicals formed under irradiation through reduction of the iodonium salt by the excited state of the photosensitizer. The pattern consists of a polyaryl film obtained from aryl radicals that react with the surface and also with the first grafted aryl groups. The modified surface is characterized by IR, XPS, AFM, and electrochemistry. The submillimetric pattern is observed by condensation and scanning electrochemical microscopy. This method permits strongly bonded patterns with variable substituents on the aryl ring to be obtained; it allows prepar...