Thermal Stability of Alkanethiolate and Aromatic Thiolate Self-Assembled Monolayers on Au(111): An X-ray Photoelectron Spectroscopy Study

Abstract

Applications of functional self-assembled monolayers (SAMs) rely to a large extent on their stability, with the thermal stability being of particular importance. In this context, thermal stability of archetypical, non-substituted alkanethiolate (AT) and aromatic thiolate (ArT) SAMs on gold was studied by synchrotron-based high-resolution X-ray photoelectron spectroscopy, taking several monolayers with different lengths of the molecular backbones as representative examples and heating them in UHV. Evaporated, grain-structured Au(111) was used as the support, in view of broad practical relevance of this substrate type. AT and ArT SAMs were found to be stable up to temperatures of ∼373 and ∼383−393 K, respectively, followed by extensive molecular desorption and decomposition upon further heating. The decomposition was mediated by the cleavage of C−S bonds, which represented the so-called "weak or weakest link" in the systems. This process contributed minorly to the temperature-induced degradation of AT SAMs but was the dominant degradation channel for the ArT case. The residual films exhibited ∼10% (AT) or ∼ 35% (ArT) of the initial packing density and represented a superposition of the laying-down phase and atomically adsorbed sulfur, with a possible coexistence of a restructured, standing-up phase in the ArT case.

Probing Matrix Effects in the Course of Electron Transfer across a Self-Assembled Monolayer

“…49 This doublet is accompanied by a weak shoulder at a low BE, corresponding to an additional, weak doublet at ∼161.0 eV (S 2p 3/2 ), which can be assigned to atomically adsorbed sulfur, based on the results of thermal stability experiments. 50,51 The spectral weight of this latter doublet is, however, comparably small, so that the respective species can be considered as minor contamination only and it can be concluded that all molecules in the films are bound to the substrate via the thiolate anchor.…”

Donor–Acceptor Stenhouse Adducts for Stimuli-Responsive Self-Assembly of Gold Nanoparticles into Semiconducting Thin Films

“…The retention in the hydrophobic state permanently is extraordinary, though, taking into account previous reports. , Importantly, the collected water phase after the experiment was shaken with 2 mL of chloroform, and no coloration of the organic phase was observed. This indicates that the loss of the nanomaterial abilities was not caused by the detachment of DASA ligands from NPs but rather ligand degradation during the procedure. , …”

“…This indicates that the loss of the nanomaterial abilities was not caused by the detachment of DASA ligands from NPs 44 but rather ligand degradation during the procedure. 43,44 First, we investigated the photostability of compounds 5 and 4 (i.e., DASA-SAc and its immediate DASA-moiety-bearing substrate, respectively). We took about 2 mg of each compound and dissolved it in CHCl 3 (10 mL).…”

Unraveling the Radiation Damage of n-Dodecanethiol Self-Assembled Monolayers on Au(100) and Au(111): A Prerequisite to Understand the Oriented Attachment of Au Nanoparticles

“…Thus where I S2 0 is the signal that would be expected in the absence of attenuation effects and λ org,S is the EAL of the organic matrix for the S 2p electrons. Following a recent publication by Asyuda et al, the thickness of the complete SAM can be related to that of the hydrocarbon layer by just adding to the latter the contribution from the S–Au interface ( t S ), as t SAM = t C + t S , taking t S = 0.24 nm (Scheme ). The quantity I S2 0 is expected to be proportional to the thiolate surface density: I S2 0 = K σ S N S2 / A , where N S2 is the number of thiolates in the excited area A , K is a constant, which involves several experimental parameters, and σ S is the photoemission cross section of sulfur.…”