Surface Structure, Adsorption, and Thermal Desorption Behaviors of Methaneselenolate Monolayers on Au(111) from Dimethyl Diselenides

Abstract

To understand the effect of headgroups (i.e., sulfur and selenium) on surface structure, adsorption states, and thermal desorption behaviors of self-assembled monolayers (SAMs) on Au(111), we examined methanethiolate (CH3–S, MS) and metheneselenolate (CH3–Se, MSe) monolayers formed from dimethyl disulfide (DMDS) and dimethyl diselenide (DMDSe) molecules by ambient vapor-phase deposition. Scanning tunneling microscopy imaging revealed that DMDS molecules on Au(111) after a 1 h deposition form MS monolayers containing a disordered phase and an ordered row phase with an inter-row spacing of 1.51 nm, whereas DMDSe molecules form long-range-ordered MSe monolayers with a (√3 × 3√3)R30° structure. X-ray photoelectron spectroscopy measurements showed that MS or MSe monolayers chemisorbed on Au(111) were formed via S–S bond cleavage of DMDS or Se–Se bond cleavage of DMDSe. On the other hand, we monitored three main desorption fragments for MS and MSe monolayers using TDS monomers (CH3S+, CH3Se+), parent mass species (CH3SH+, CH3SeH+), and dimers (CH3S–SCH3 +, CH3Se–SeCH3 +). Interestingly, we found that thermal desorption behaviors of MSe monolayers were markedly different from those of MS monolayers. All desorption peaks for MSe monolayers were observed at a higher temperature compared with MS monolayers, suggesting that the adsorption affinity of selenium atoms for the Au(111) surface is stronger than that of sulfur atoms. In addition, the desorption intensity of dimer fragments for MSe monolayers was much lower than for MS monolayers, indicating that selenolate SAMs on Au(111) did not undergo their dimerization efficiently during thermal heating compared with thiolate SAMs. Our results provide new insight into understanding the surface structure and thermal desorption behavior of MSe monolayers on Au(111) surface by comparing those of MS monolayers.

Sensitive SERS nanotags for use with 1550 nm (retina-safe) laser excitation

“…This suggests that the selenophene group adheres more effectively to the gold surface than thiophene and supports previous reports where selenolates have shown a greater affinity for gold surfaces than thiolates and phenyls. 11,26,27 Due to the exceptional SERS response obtained with these nanotags, particle dilution studies were conducted in order to calculate limits of detection (LOD) and further determine the level of sensitivity that can be achieved at this extremely red-shifted laser excitation. The LOD Commercial Nanotag study was conducted over the concentration range 1.7 nM to 80 pM.…”

Red to brown to green colorimetric detection of Ag+ based on the formation of Au-Ag core-shell NPs stabilized by a multi-sulfhydryl functionalized hyperbranched polymer

“…For instance, 11-mercaptoundecanoic acid, [14] 3-mercaptopropionic acid, [15] dithioerythritol [16] and alkanethiols with different chain lengths (2-mercaptoethanol, 4-mercraptobutanol, 6-mercaptohexanol, and 11-mercaptoundecanol) [17] have been applied to AuNP-based colorimetric systems. However, these monodentate ligands as capping agents can readily desorb or decompose upon heating, and be displaced from the AuNPs surface over time, [18][19][20][21] therefore hindering and limiting their application in sensing analyte.…”

Phase‐separated Nanodomains Formed by Coadsorption of Alicyclic and Aromatic Thiols on Au(111)

“…The adsorption of thiols onto metals creates self‐assembled monolayers (SAMs) that can provide a versatile route for fabrication of nanoscale structures and functionalized monomolecular thin films . Two‐component mixed SAMs are especially promising due to their strong potential to tune the physical and chemical properties of surfaces by changing the tail group, length, and chemical structure of the thiol molecular backbone.…”

“…CHT (C 6 H 11 ‐SH) and 4‐FBT (F‐C 6 H 4 ‐SH) were obtained from Sigma‐Aldrich (St. Louis, MO, USA). Au(111) substrates on mica were prepared by thermal evaporation, as described in a previous paper . Coadsorbed CHT and 4‐FBT SAMs were prepared by immersing the Au(111) substrates in an ethanol solution containing a total concentration of 1 mM of 9:1, 5:5, and 1:9 molar ratios of CHT and 4‐FBT at room temperature for 1 h. STM observations were performed under ambient conditions using a NanoScope E (Veeco Instruments, Santa Barbara, CA, USA).…”