Self-Assembly of Alkanedithiols on Au(111) from Solution: Effect of Chain Length and Self-Assembly Conditions

Abstract

A comparative study on the adsorption of buthanedithiol (BDT), hexanedithiol (HDT), and nonanedithiol (NDT) on Au(111) from ethanolic and n-hexane solutions and two different preparation procedures is presented. SAM characterization is based on reflection-absorption infrared spectroscopy, electrochemistry, X-ray photoelectron spectroscopy, and time of flight direct recoil spectroscopy. Results indicate that one can obtain a standing-up phase of dithiols and that the amount of the precursor lying-down phase decreases from BDT to NDT, irrespective of the solvent and self-assembly conditions. A good ordering of the hydrocarbon chains in the standing-up configuration is observed for HDT and NDT when the system is prepared in degassed n-hexane with all operations carried out in the dark. Disulfide bridges at the free SH terminal groups are formed for HDT and to a lesser extent for NDT prepared in ethanol in the presence of oxygen, but we found no evidence of ordered multilayer formation in our experiments. No disulfides were observed for BDT that only forms the lying-down phase. Our results demonstrate the key role of the chain length and the procedure (solvent nature and oxygen presence) in controlling the surface structure and chemistry of SAMs dithiols on Au(111).

Alkylthiol self-assembled monolayers on Au(111) with tailored tail groups for attaching gold nanoparticles

“…[9] They reach this conclusion by measuring the ratio of the S2p core level shift at 163.5 eV related to free S-H bonds or disulfides and 162 eV related to thiolates. Interestingly, by monitoring the 163.5 eV peak, they conclude that the signal comes from terminal sulfur atoms that have formed disulfide bridges.…”

“…In a previous study, it has been shown that BDT SAM formation leads to a mix of standing-up and flat-lying phases, contrary to NDT which leads to disulfides formation. [9] And thus, the disulfides formation is lower for BDT compare to NDT. This weaker tendency of BDT for forming rows can be explained by the shorter chain length and by the weaker van der Waals interactions between the alkyl chains in neighbouring molecules [33].…”

Surface plasmon resonance for detecting clenbuterol: Influence of monolayer structure

“…Thiol terminal of the DSP binds to the Au surface and a biochemical recognition element with an NH 2 -terminal can be instantly immobilized, since succinimide group of DSP is replaced by amines in a neutral buffer in a single step. However, since alkanethiols with short alkyl chains are often shown to adopt a lying-down phase [25,26], the orientation of biochemical recognition element can significantly affect the sensitivity of the biosensor. We will, therefore, discuss the relationship between the sensitivity of the sensor and the lying-down configuration of the molecules in domain structure.…”

Electrochemical study of adlayers of α,ω-alkanedithiols on Au(111): Influence of the forming solution, chain length and treatment with mild reducing agents

“…The chain length and the preparation procedure in the surface structure and chemistry of SAMs of DTs on Au(1 1 1) have been regarded as important features recently [16,17]. In these studies, it is inferred that the best way to prepare DT SAMs is by using n-hexane N 2 saturated solutions in absence of light.…”