Patterning Surfaces through Photografting of Iodonium Salts

Abstract

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 Φ L and lifetime τ L , quenching rate constant (k q), ΔG° and quantum yield (Φ R)]. 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 to obtain strongly bonded patterns with variable substituents on the aryl ring; it allows preparing various patterns of multifunctional surfaces that can be used for sensors and diagnostics, or to limit hydrophilic paths within hydrophobic films for surface tension confined microfluidic devices.

Can Plasmon Change Reaction Path? Decomposition of Unsymmetrical Iodonium Salts as an Organic Probe

“…However, the application of unsymmetrical ISs for the surface modification deserves more attention due to the lower price and versatile synthetic procedures. [40][41][42][43] In general, the selectivity of C-I bond cleavage, especially homolytic, can be considered as the highly challenging issue in the chemistry of ISs. 44,45 The homolytic decomposition of unsymmetrical ISs often leads to the formation of product mixtures with extremely low selectivity, [46][47][48][49] as seen in the application of unsymmetrical ISs for the modification of carbon surfaces.…”

“…44,45 The homolytic decomposition of unsymmetrical ISs often leads to the formation of product mixtures with extremely low selectivity, [46][47][48][49] as seen in the application of unsymmetrical ISs for the modification of carbon surfaces. 39,43,50,51 Nevertheless, improved selectivity towards the formation of radicals of the electron-rich aryl substituents has been observed in the SET-reactions, such as in the metal-free coupling of ISs. [52][53][54] Thus, the evaluation of regioselectivity issues has a great demand from the plasmon-assisted reactions mechanisms as well as from the common reactivity point of view.…”

Surface modification of materials: Electrografting of organic films

“…In spite of its wide use in the organic chemistry of diazonium salts, photochemistry has been seldom used for surface modification. Recent results include the photochemical cleavage of iodonium salts Ar-I + -Ar' [9] (under visible light in the presence of a sensitizer) and azosulfones Ar-N=N-SO 2 CH 3 [10] (under UV light). With the first reaction it is possible to pattern gold surfaces by using a mask, with the second one it is possible to attach both the aryl group and the sulfone to the surface.…”

Simultaneous Photografting of Two Organic Groups on a Gold Surface by using Arylazo Sulfones as Single Precursors

“…Among these species, diarylcarbenes, obtained by thermolysis or photolysis of the corresponding diazo compounds, have been investigated 20 for the preparation of highly colored polystyrene beads. 21 Diazonium salts (Ar-N 2 + ) or iodonium salts (Ar-I + -Ar') under UV 22 or visible light exposure (in the presence of a photoredox catalyst) 23,24,25,26 cleave to aryl radicals that react with metals or polymers. In this way it was possible to pattern gold surfaces, 24 polyethyleneterephthalate (PET) 25 or paper.…”

“…21 Diazonium salts (Ar-N 2 + ) or iodonium salts (Ar-I + -Ar') under UV 22 or visible light exposure (in the presence of a photoredox catalyst) 23,24,25,26 cleave to aryl radicals that react with metals or polymers. In this way it was possible to pattern gold surfaces, 24 polyethyleneterephthalate (PET) 25 or paper. 26 However, all the above reactions allow for the functionalization of the surface by a single chemical group obtained from the starting precursor.…”