Electrochemical, High-Resolution Photoemission Spectroscopy and vdW-DFT Study of the Thermal Stability of Benzenethiol and Benzeneselenol Monolayers on Au(111)

Abstract

The preparation and thermal stability of benzenethiol and benzeneselenol self-assembled monolayers (SAMs) grown on Au(111) have been investigated by electrochemical experiments and high-resolution photoemission spectroscopy. Both techniques confirm the formation of monolayers with high packing densities (θ = 0.27-0.29 ML) and good degrees of order in both cases. Despite many similarities between the two SAMs, the thermal desorption is distinctly different: whereas the benzenethiol SAM desorbs in a single steplike process, the desorption of the benzeneselenol SAM occurs with a much lower activation energy and involves the cleavage of some Se-C bonds and a change in molecular configuration from standing up to lying down. This behavior is explained by considering the different nature of the bonding of the headgroup with the metal surface and with the phenyl ring. Density functional theory calculations show that the breakage of the Se-C bond has a lower activation energy barrier than the breakage of the S-C bond.

Seleno groups control the energy-level alignment between conjugated organic molecules and metals

“…This final annealing step also induces a φ decrease of 0.05 eV. The origin of these observations is likely desorption of intact molecules, probably accompanied by (substrate-mediated) chemical reactions and desorption of reaction products, similar to what was reported for benzeneselenolate/Au(111) 39,85 and TTT/Au(111). 45 …”

“…14 Notably, the BE values of the interface species for Se3d and C1s are very similar to those found for selenolate SAMs on Au(111) and Ag(111), where the selenium atoms are covalently bound to the metal. [39][40][41] This strongly hints towards a similar interaction in terms of strength and bond mediation (i.e., via the selenium atoms) also between TSeT and Au and Ag.…”

“…In particular, a systematic variation with the number of methylene groups was found for oligophenyl-substituted alkanethiolate SAMs (so-called odd-even effects) 42,43 and explained with differently strained sulfur-metal bonds. 44 On the other hand, for benzeneselenol/Au(111) 39 and biphenyl methylenethiol/Ag(111), 43 two core level peaks have been attributed to two chemically different chalcogen species on the surface: chalcogen atoms in chalcogenolate molecules [at higher BE, which would correspond to IF 1 in Fig. 1(b)] and chalcogen atoms abstracted from the molecules [at lower BE, which would correspond to IF 2 in Fig.…”

The Role of a Double Molecular Anchor on the Mobility and Self‐Assembly of Thiols on Au(111): The Case of Mercaptobenzoic Acid

“…[3] On the other hand, strong molecular reorganizations take place during alkanethiol adsorption, leadingtoaphase transition from diluted lying-down phases to denser standing-up phases, usually the well-known c(4 2) and/or ( p 3 p 3)R308 lattices, with surface coverage q = 0.33 and at ilt angle (a)o fa bout 308 with respect to the substrate normal. [7] As expected, by increasing adsorption time and/or concentration/pressure, molecules adopt as tanding-upc onfigurationw ith am uch smaller a value ranging from 198 to 308, [8][9][10] which allows more molecules to be accommodated to form denser stable structures (q = 0.2-0.3)t hrough molecule-molecule interactions. As imilar situation has been reported for small aromatic thiols and amino acids.…”

Thiol Molecules as Temperature Sensors for Surface-enhanced Raman Scattering Measurements of Heat-sensitive Materials

“…This finding is in good agreement with other reports, in which the coverage of the TP decreased with heating in vacuum, air, water, and ethanol by X-ray photoelectron spectroscopy 24 and cyclic voltammetry. 25 The decrease in the SERS signal of TP in water was observed at laser power densities higher than 11 mW¯m…”