Self-assembled Monolayers of Two Aromatic Disulfides and a Diselenide on Polycrystalline Silver Films: An Investigation by SERS and XPS

Abstract

Self-assembled monolayers of diphenyldisufide (DDS), naphthalenedisulfide (NDS), and diphenyldiselenide (DDSe) on polycrystalline silver films have been investigated by surface enhanced Raman spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS). DDS adsorbs on Ag through a homolytic cleavage of the S-S bond and resultant thiolate at the surface decomposes upon prolonged exposure to air. The geometry of the molecule is such that the benzene ring is almost horizontal to the surface. The Raman spectrum has been assigned in the light of ab-initio molecular orbital calculations. In DDSe, the Se-Se bond is retained upon adsorption and the molecule sticks up. In contrast, NDS is highly reactive on the microscopically rough surface so that a stable monolayer could not be prepared. A temperature dependent Raman study of the DDS monolayer shows the absence of any reorientation at the surface as one would expect from the adsorption geometry. XPS study complements the SERS data and shows the presence of Ag 2 S on an NDS exposed surface.

Comparative Study on the Corrosion Inhibitive Effect of 2-Mecraptobenzothiazole and Na2HPO4 on Industrial Conveying API 5L X42 Pipeline Steel

“…The next pair of Raman shifts near 1000 cm −1 (shoulder) and 1120 cm −1 comes to identify iron phosphate crystalline or amorphous phases [69] in conjunction with the combination of two other shifts near 1250 cm −1 and 1270 cm −1 and a smaller shift at 1310 cm −1 , the latter of which may have been gained from PO 2 asymmetric stretch. Moreover, the pair of 1430 cm −1 and 1480 cm −1 peaks in combination with those at 1580 cm −1 and 1590 cm −1 were noted to be in accordance with experimental Raman shift values for the adsorbed MBT molecule, especially when it is measured in its thione mode [65,72].…”

“…The next pair of Raman shifts near 1000 cm −1 (shoulder) and 1120 cm −1 comes to identify iron phosphate crystalline or amorphous phases [69] in conjunction with the combination of two other shifts near 1250 cm −1 and 1270 cm −1 and a smaller shift at 1310 cm −1 , the latter of which may have been gained from PO2 asymmetric stretch. Moreover, the pair of 1430 cm −1 and 1480 cm −1 peaks in combination with those at 1580 cm −1 and 1590 cm −1 were noted to be in accordance with experimental Raman shift values for the adsorbed MBT molecule, especially when it is measured in its thione mode [65,72]. Taking into account the Raman spectrum of Steel-NaCl-Na 2 HPO 4 (Figure 12b), it may be remarked that the absence of a peak near 218-221 cm −1 , which is attributed in the literature to the symmetric stretch of interlayer chloride ions in green rust [63,68] in combination with the detection of iron phosphate salts vibrations, at 430-450 cm −1 for Fe 4 (P 2 O 7 ) 3 and at 1011 cm −1 for a symmetric PO 3 2− symmetric stretch of Fe 3 (PO 4 ) 2 A (A for anion) [69], reassures mild steel surface phosphating and consequently the increase of crystallinity in corrosion products after exposure and drying processes.…”

Characterization of Tribofilm from Sulfurized Mohwa Oil

“…This contention has arisen because SMO gives the least amount of iron sulfide. On the other hand, the above results are consistent with the observation that the decomposition of SMO (35 wt%) at 150 • C for 8 hours in the presence of hydrocarbon solvent is about 10 wt% higher than that of dibenzyl disulfide (DBDS) at 1% equivalent sulfur concentration [20][21][22].…”

New metalorgano-chalcogenide compounds based on polymeric frameworks constructed by Se–Hg intermolecular interactions: Preparation, structural characterization, and Raman evaluation

“…Published studies on Raman spectroscopy have addressed metal chalcogenide compounds such as HgSe and CdSe nanoparticles, gold and silver nanoparticles functionalized with dichalcogenides, and polycrystalline films containing diselenide, among other materials [40][41][42][43][44], but published information on Raman spectroscopy for metal-organochalcogenide and polymeric compounds similar to those here described is scarce. To improve our knowledge of Raman assignments for the new molecules, we began by studying Raman spectra from simpler molecules (synthetic precursors), proceeding to more complex metal-chalcogenide compounds based on polymeric frameworks.…”