Photoreactivity of Alkylsiloxane Self-Assembled Monolayers on Silicon Oxide Surfaces

Abstract

We have combined contact angle measurements, Fourier transform infrared spectroscopy (FT-IR), and atomic force microscopy (AFM) to investigate the UV photoreactivity of octadecylsiloxane (ODS) SAMs (self-assembled monolayers) in air. Contact angle measurements present evidence that ozone is not the active agent in alkylsiloxane SAM degradation under UV illumination in air. A combination of UV and oxygen is necessary for monolayer degradation to proceed. AFM measurements on submonolayer coverage SAMs provide direct evidence of the photodegradation of ODS SAMs and reveal the role of defects in the degradation process. FT-IR and AFM results suggest that the hydrocarbon chain is the reactive site of the monolayers. A microscopic mechanism of the photoreactivity involving hydrogen abstraction is suggested based on the mechanism of gas-phase oxidation of alkanes. Our results have implications in clarifying the contribution from the reactivity of alkyl chains during the photomodification of SAMs. This clarification may provide insight into optimization of the SAM photopatterning processes.

Unusual aggregates from the oxidation of alkene self-assembled monolayers: a previously unrecognized mechanism for SAM ozonolysis?

“…[8][9][10][11][12] Oxidation of alkane SAMs, often in the presence of UV radiation, has been the subject of many studies (e.g., see ref. [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. While the vast majority of the work to date has focused on alkanethiol SAMs on gold, several studies of the ozone oxidation of C8 and C3 terminal-alkene SAMs on silica surfaces have been reported.…”

Impact dynamics of water droplets on chemically modified WOx nanowire arrays

“…Previous studies have demonstrated that UV radiation and oxygen in air play significant roles in the UV-enhanced decomposition of alkyl chains of OTS. 18,19 The alkyl chains of OTS are decomposed by OH radicals and/or atomic oxygen produced by the UV-catalyzed dissociation of ozone, which is photogenerated from air.…”

Fundamentals of Surface Modification

“…Therefore, this type of modification will be helpful in fictionalization of biomaterials to enhance their cell adhesion property, so better stability and long time use can be achieved. Ficai A. et al used hydroxyapatite for layer-by-layer deposition onto the collagen matrix for orthopaedic implant applications [41].…”