A surface enhanced Raman spectroscopy study of aminothiophenol and aminothiophenol-C60 self-assembled monolayers: Evolution of Raman modes with experimental parameters

Abstract

P-aminothiophenol (PATP) is a well-known molecule for the preparation of self-assembled monolayers on gold via its thiol functional group. After adsorption, it has been demonstrated that this molecule is anchored to gold through its thiol group, and standing nearly upright at the surface with the amino functional group on top. This molecule has been extensively studied by surface enhanced Raman spectroscopy but its exact SERS spectrum remains unclear. Here, we demonstrate that it can be strongly affected by at least two experimental parameters: laser power and layer density. Those features are discussed in terms of a dimerization of the PATP molecules. The free amino group affords the adsorption of other molecules such as C(60). In this case, a complex multilayer system is formed and the question of its precise characterisation remains a key point. In this article, we demonstrate that surface enhanced Raman spectroscopy combined with x ray photoelectron spectroscopy can bring very important information about the organization of such a self-assembled multilayer on gold. In our study, the strong evolution of Raman modes after C(60) adsorption suggests a change in the organization of aminothiophenol molecules during C(60) adsorption. These changes, also observed when the aminothiophenol layer is annealed in toluene, do not prevent the adsorption of C(60) molecules.

Underpotential deposition of selenium and antimony on gold

“…As the substrate is made of gold, we cannot totally exclude that an optical near-field enhancement occurs and that we perform surface-enhanced Raman spectroscopy (SERS). This feature is usually observed with well-nanostructured samples [45], which is not the case here. Nevertheless, it could explain the difference in intensity observed between the two laser excitations.…”

Vibrational modes of aminothiophenol: a TERS and DFT study

“…These two modes are associated to ATP molecules, this is clearly confirmed by DFT simulations of the ATP Raman modes (Fig. 15 These features are hardly compatible with a charge transfer mechanism and based on DFT calculations several authors have proposed to attribute them to a new molecule: DMAB. In some particular places of the sample, other modes are observed: 1140, 1390 and 1440 cm À1 (see Fig.…”

“…15 The atomically flat Au(111) substrates were purchased from Arrandee. 15 The atomically flat Au(111) substrates were purchased from Arrandee.…”

Spectral fluctuation in SERS spectra of benzodiazepin molecules: The case of oxazepam

“…As mentioned in the Introduction, the role of chemical interaction between the molecule and the metallic surface in essential in SERS. [ 22 ] For molecules with a strong affinity for gold, such as thiol molecules, [ 23 ] this question can be easily addressed. This is not the case here: oxazepam has no specific chemical function with a very high affinity for gold.…”