TY - JOUR A1 - Song, X. A1 - Ma, Y. A1 - Wang, C. A1 - Dietrich, Paul A1 - Unger, Wolfgang A1 - Luo, Y. T1 - Effects of protonation, hydrogen bonding, and photodamaging on X-ray spectroscopy of the amine terminal group in aminothiolate monolayers JF - The journal of physical chemistry / C N2 - The amine headgroup, NH2, in aminothiolate monolayers can often generate unexpectedly rich structures in its N K-edge X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra that are difficult to assign. We have carried out density functional theory (DFT) calculations to study the XPS and NEXAFS of amine headgroup in four different aminothiolate monolayers, namely, aliphatic 11-aminoundecane-1-thiol (AUDT), aromatic 4-aminobenzenethiol (ABT), araliphatic 4-aminophenylbutane-1-thiol (APBT), and 3-(4''-amino-1,1':4',1''-terphenyl-4-yl)propane-1-thiol (ATPT), with the focus on structure changes caused by protonation, hydrogen bonding, and X-ray damaging. Spectra of all possible saturated and unsaturated species, as well as X-ray damage products, such as imine, nitrile, azo species, and cumulative double bonds, have been thoroughly examined. It is found that extra spectral structures observed in the experimental XPS spectra do not result from protonation but from the formation of a primary ammonium. The X-ray excitation can induce cross-linking between two neighboring molecules to form different complexes that contribute to the π* features in NEXAFS spectra. KW - Surface analysis KW - Spectrum simulation KW - X-ray absorption spectroscopy KW - Self assembling monolayer PY - 2012 DO - https://doi.org/10.1021/jp302716w SN - 1932-7447 SN - 1089-5639 VL - 116 IS - 23 SP - 12649 EP - 12654 PB - Soc. CY - Washington, DC AN - OPUS4-26255 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -