Self-Assembled Monolayers Composed of Aromatic Thiols on Gold:  Structural Characterization and Thermal Stability in Solution

Abstract

Self-assembled monolayers (SAMs) derived from 1,2-bis(mercaptomethyl)-4,5-dialkylbenzene (1), 1-mercaptomethyl-3,4-dialkylbenzene (2), 1-mercaptomethyl-4-alkylbenzene (3), 1-mercapto-4-alkylbenzene (4), and 4-mercaptomethyl-4‘-alkoxybiphenyl (5) were prepared by adsorption from solution onto evaporated gold. The SAMs were characterized by contact angle goniometry, optical ellipsometry, and polarization modulation infrared reflection absorption spectroscopy. Comparison of SAMs generated from 1 and 2 to well-known SAMs generated from normal alkanethiols (6) revealed that the former SAMs are densely packed and highly oriented. The alkyl chains of the SAMs derived from 1 and 2 are, however, less crystalline (i.e., less conformationally ordered) than those derived from 6. The adsorption of compounds 3, 4, and 5 onto gold yielded highly crystalline SAMs. Solution-phase thermal desorption of SAMs 1 − 6 at temperatures ranging from 60 to 110 °C was monitored using ex situ ellipsometry. The desorption profiles of SAMs derived from 1 − 6 revealed two distinct kinetic regimes: a fast initial desorption followed by a substantially slower desorption. The rates of film desorption in both regimes were observed to increase with increasing temperature. Comparison of the desorption profiles of SAMs 1 − 6 showed that the structure of the adsorbate strongly influenced the rate of desorption; the differences were more apparent during the advanced stages of desorption. These studies provided a framework for evaluating the structural features and the mechanistic pathways that dictate the thermal stability of SAMs on gold.

Forming Microstructured Alkanethiol Self-Assembled Monolayers on Gold by Laser Ablation

“…4(a)]. This indicates that the ablation process is purely thermally and not chemically based, what is in agreement with literature data [9]- [12]. By means of the laser scanner, also more complex structures can be prepared easily in the 100-m range like the microarrays shown in Fig.…”

Nanoparticle‐Driven Orientation Transition and Soft‐Shear Alignment in Diblock Copolymer Films via Dynamic Thermal Gradient Field

“…The out‐of‐plane thermal expansion behavior of AuNP filled PS‐PMMA films was investigated by ellipsometry via continuous heating from 30 to 210 °C in 40 min. As shown in Figure D, there is a bump in the first heating curve for PS‐PMMA/10%AuNP film corresponding to desorption of PS ligands due to thermal instability of Au–thiol bonds based on prior studies of AuNP in solution . This thermally unstable interaction of PS ligands reduced the T g of the nanocomposite film, but only transiently.…”

Poly(l-lysine) Interfaces via Dual Click Reactions on Surface-Bound Custom-Designed Dithiol Adsorbates

“…The second step involved a thiol-Michael addition of the cysteine-terminated poly-L-lysine to the maleimide and was conducted under ambient conditions; 19 this latter reaction has been used in a wide variety of materials/biomaterials applications. 2,15,20 The use of a short-chained dithiol platform for producing a polypeptide interface offers at least three advantages when compared to related approaches involving the physisorption of peptides: 5,21 (1) a reliable site for covalent attachment of peptide molecules, (2) a highly stable monolayer on the surface, 22,23 and (3) circumvention of problems that are encountered when using adsorbates having long alkyl chains (e.g., disarray in the resulting peptide films). Further, the minor differences in structure between the two dithiol adsorbates provide an opportunity to assess the value of the added conformational mobility afforded by a limited increase in the length of the alkyl spacer extending from the rigid aromatic ring.…”