Noradrenaline and a Thiol Analogue on Gold Surfaces: An Infrared Reflection−Absorption Spectroscopy, X-ray Photoelectron Spectroscopy, and Near-Edge X-ray Absorption Fine Structure Spectroscopy Study

Abstract

Self-assembled monolayers and multilayers of a noradrenaline analogue (Nor-Pt) on gold substrates as well as multilayers of noradrenaline have been investigated by means of the molecular orientation, the molecule−surface interaction, the molecular composition and the functional group availability for further biointeraction processes, using X-ray photoelectron spectroscopy (XPS), infrared reflection−absorption spectroscopy (IRAS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. A chemical shift (1.7 eV) of the S 2p peak to lower binding energies is observed, in the XPS spectrum, indicating that the Nor-Pt molecules are chemisorbed onto the gold substrate. The IR results show that Nor-Pt adsorbate has the CO stretching vibration modes parallel oriented relative to the gold substrate. The average tilt angle of the aromatic ring relative to the gold surface normal is determined to be approximately 51°, based on the NEXAFS measurements on Nor-Pt monolayers. The experimental results and assignments are supported with theoretical studies where we use the building block principle in the spectral analysis and compare with the measurements of noradrenaline and Nor-Pt. The theoretical calculations are shown to be useful; for angle dependence NEXAFS studies as resonances with fully π* or σ* character are preferred for correct analysis.

Bioinspired Catechol‐Terminated Self‐Assembled Monolayers with Enhanced Adhesion Properties

“…XPS results are also in agreement with those found for similar catechol‐terminated monolayers [16d], (See Supporting Information, Figure S2). The S 2p core level clearly presents two peaks with a 2:1 ratio, located at 161.9 and 163.0 eV, assigned to sulphur atoms chemically bound to gold surfaces.…”

Calculating core‐level excitations and x‐ray absorption spectra of medium‐sized closed‐shell molecules with the algebraic‐diagrammatic construction scheme for the polarization propagator

“…In this section, the previously discussed results of the CVS‐ADC(2)‐x calculations are compared to CVS‐ADC(2)‐s, as well as to TD‐DFT/B3LYP results, as TD‐DFT has proven now several times to yield quite accurate results for core excitation spectra, in particular in combination with the B3LYP functional. Figure summarizes the arithmetic mean errors of the computed excitation energies with respect to experimental values for all three methods, which have been evaluated for each molecule and every core excitation separately. As example, the results for the ANQ molecule are analyzed here (Tables and ).…”

Requirements of first-principles calculations of X-ray absorption spectra of liquid water

“…Alternatively, the different tensor components can be used to treat polarization dependences of the sample, relevant for, e.g., the treatment of self-assembled monolayers on metal surfaces. 85 For the calculation of the polarizability, standard linear response theory suffers from divergences at resonance energies, related to the lack of decay from the excited states. By introducing a damping term γ n for each excited state |n , spontaneous and collision-induced relaxation/de-excitation effects can be included in a phenomenological manner.…”