Rapid reduction of self-assembled monolayers of a disulfide terminated para-nitrophenyl alkyl ester on roughened Au surfaces during XPS measurements

The application of multiple spectroscopic techniques to the characterisation of self-assembled monolayers (SAMs) is essential for determining whether the desired surface functionalization was achieved, the molecules are integer after self-assembly and well-packed on the substrate. We investigated the use of surface enhanced Raman spectroscopy and X-ray photoelectron spectroscopy to characterise SAMs of a disulfide-functionalised nitrobenzene (i.e. 4-nitrophenyl-5-(1,2-dithiolan-3-yl)pentanoate). We show that electron-induced damage during acquisition of photoemission spectra of the monolayer occurs through reduction of the nitro group. Use of roughened bulk gold substrates to enhance the SERS sensitivity results in an increase in the rate at which the reduction proceeds.