A Study on the Formation and Thermal Stability of 11-MUA SAMs on Au(111)/Mica and on Polycrystalline Gold Foils

Abstract

In this article we present a comprehensive study of 11-mercaptoundecanoic acid self-assembled monolayer (SAM) formation on gold surfaces. The SAMs were prepared in ethanolic solution, utilizing two different substrates: Au(111)/mica and polycrystalline gold foils. Several experimental methods (X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and atomic force microscopy) reveal a well-defined SAM. The main focus of this work, however, was to test the stability of these SAMs by thermal desorption spectroscopy. The spectra show different desorption peaks indicating different adsorption states and/or decomposition products on the surface. The assumed monolayer peak, which can be attributed to desorption of the intact molecule, is detected at 550 K. Further desorption peaks can be found, which result, e.g., from cracking of the S-C bond on the surface, depending on the substrate quality and on the residence time under ambient conditions.

Adsorption and thermal decomposition of 2-octylthieno[3,4-b]thiophene on Au(1 1 1)

“…Similar dehydrogenations of aliphatic carbon chains were reported for alkanethiols and mercaptanoundecanoic acids where, upon heating to $600 K, all chemisorbed alkanethiols began to produce hydrogen and yield carbon clusters on the surface [28,37,38]. The high temperature peak above 760 K being a result of sample holder degassing can be excluded since we did not observe this peak when performing experiments with a Au(1 1 1) surface that had not been exposed to OTTP.…”

“…The C1s binding energy has a maximum at 284.0 eV, and a considerable amount of carbons remain on the surface. It has been reported that a pure carbon film rich of sp linear chains could be formed by heating hydrocarbons in UHV and subsequently stabilized as all-carbon structures (polycumulenes or carbon clusters) [37,40]. Based on our XPS and TPD results, the existence of solid carbon after heating OTTP on Au(1 1 1) at 900 K implies that we can achieve a hydrogen-free carbon backbone using OTTP.…”

“…Two components are needed to deconvolute the experimental results. They occur at binding energies of 284.6 eV and 284.0 eV and are attributed to the aliphatic carbon chain and dehydrogenated carbon, respectively [37]. Note that the H 2 desorption in the high temperature region is due to dehydrogenation of aliphatic carbon chains (Fig.…”

“…The first peak was found at a binding energy of 284.6 eV, which is characteristic of an aliphatic carbon chain. The second peak at 287.1 eV can be attributed to emission from the C atoms next to the sulfur atoms in the thienothiophene rings [37]. When the S2p peak of the surface was collected, a small signal was observed around at 162.0 eV (Supplementary information), implying that OTTP molecules were chemisorbed on gold surface, similar to the unsubstituted thiophene SAMs [19,24,25].…”

Influence of Thiol Molecular Backbone Structure on the Formation and Reductive Desorption of Self-Assembled Aromatic and Alicyclic Thiol Monolayers on Au(111) Surface

“…To understand these fundamental issues, STM has been used as one of the very powerful tools for visualizing the atomic-and molecular-scale surface structures of SAMs on metal surfaces, as demonstrated in many previous reports. [1][2][3][4][6][7][8][9][10][11][12][13][14][15][16][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Additionally, thermal desorption spectroscopy (TDS) 10,11,32,[34][35][36][37] and electrochemical measurements [38][39][40][41][42][43] are very useful techniques to investigate the adsorption conditions, thermal stability, and the electrochemical behavior and stability of SAMs. TDS measurements revealed that alkanethiol SAMs exist as a form of monomer (alkanethiolate), not dimers (dialkyl disulfides) derived from associa-tive reactions of the sulfur headgroups, 10,11,34,…”