XP motifs

In addition to using X-rays to irradiate a surface, ultraviolet light may be used as the source for photoelectron spectroscopy (PES). This technique, known as ultraviolet photoelectron spectroscopy (UPS, Figure 7.38), is usually carried out using two He lines (Hel at 21.2 eV and Hell at 40.8 eV), or a synchrotron source. This technique is often referred to as soft PES, since the low photon energy is not sufficient to excite the inner-shell electrons, but rather results in photoelectron emission from valence band electrons - useful to characterize surface species based on their bonding motifs. It should be noted that both UPS and XPS are often performed in tandem with an Ar" " source, allowing for chemical analysis of the sample at depths of < 1 J,m below the surface. 

In the study involving surface functionalization by photoenol chemistry, we introduced a novel 2-formyl-3-methylphenoxy (FMP) motif which we found more efficient than the 2-methylbenzophenone (at least in the conditions we used) [PAU 12b]. In particular, we demonstrated that complete cycloaddition could take place in minutes. Therefore, we aimed at bringing an FMP derivative onto surfaces in order to carry out patterning experiments. Again, we S5uithesized a silane derivative which we coated onto silicon wafers and assessed the success of the reaction by XPS and ToF-SIMS. The former confirmed the presence of the FMP moiety and the success of the photoinduced ftmctionalization of a bromine-containing maleimide which can act as a pol5mierization initiator as we will describe below. We also showed by ToF-SIMS that it is possible to use the photoenol method in the fiamework of peptide immobilization. 

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