Methylthiolate on Au(111): adsorption and desorption kinetics

Abstract

Low energy electron diffraction, Auger electron spectroscopy, X-ray photoelectron spectroscopy and line of sight mass spectrometry have been used to study the adsorption and desorption of dimethyldisulfide (DMDS) on Au(111). At 300 K adsorption is dissociative, forming a chemisorbed adlayer of methylthiolate with a 1/3 ML, (sq rt 3 x sq rt 3)R30 degrees, structure. At 100 K adsorption is molecular, with dissociation to form the 1/3 ML (sq rt 3 x sq rt 3)R30 degrees methylthiolate structure occurring at 138-160 K. A physisorbed DMDS layer, with a coverage of 1/6 ML of DMDS, forms on top of the (sq rt 3 x sq rt 3)R30 degrees chemisorbed MT surface for T < or = 180 K, with multilayers forming for T < or = 150 K. In temperature programmed desorption, multilayers of DMDS desorbed with zero order kinetics and an activation energy of 41 kJ mol(-1); the physisorbed layer desorbed with first order kinetics, exhibiting repulsive lateral interactions with an activation energy which varied from 63 kJ mol(-1) (theta = 0) to 51 kJ mol(-1) (theta = 1); the chemisorbed methylthiolate layer desorbed associatively as DMDS via the physisorbed layer, the activation energy for the reaction, 2 methylthiolate --> physisorbed DMDS, exhibiting repulsive lateral interactions with an activation energy which varied from 65 kJ mol(-1) (theta = 0) to 61 kJ mol(-1) (theta = 1). The physisorbed disulfide layer explains the pre-cursor state adsorption kinetics observed in sticking probability measurement, while its relatively facile formation provides a mechanism by which thiolate self-assembled monolayers can become mobile at room temperature.

On the kinetics and thermodynamics of S–X (X = H, CH3, SCH3, COCH3, and CN) cleavage in the formation of self-assembled monolayers of alkylthiols on Au(111)

“…Combined low-energy electron diffraction, Auger electron spectroscopy, X-ray photoelectron spectroscopy, and line of sight mass spectrometry have been used to study the adsorption and desorption of DMDS on Au (111). According to these works, the S-S bond clearly cleaves on the surface and the estimated barrier height is to be in the range of 14.6-15.3 kcal/mol [105].…”

“…At the same time, both experimental and theoretical studies on other alkyl thiols, such as dimethyldisulphide (DMDS), reveal that the S-S bonds cleaves homolytically leaving a MeSÁ radical to be adsorbed firmly on the surface. The kinetics of such cleavage has been experimentally measured for DMDS indicating activation energy of 65 kJ/mol [105,106].…”

Thiolate adsorption on Au(${\bm {hkl}}$hkl) and equilibrium shape of large thiolate-covered gold nanoparticles

“…This cleavage is known to take place even at room temperature. 15 The adsorption of a CH 3 S-radical has also been studied on Au(100) and Au(110) surfaces by Masens et al 9 who found that the adsorption energy of CH 3 S-on Au(110) is lower by 0.13 eV than that on (100) and by about 0.43 eV than that of (111). Despite the large number of theoretical studies the nature of a binding site is an open issue.…”

“…[3][4][5][6][7][8][9][10][11][12] Various groups have studied the dissociative adsorption of dimethyl disulfide (DMDS) on Au(111), both theoretically 3,11 and experimentally. [13][14][15] In particular, Nuzzo et al 13 suggested, after employing a large variety of experimental methods including X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), high-resolution electron energy loss spectroscopy (HREELS), and thermal desorption spectroscopy (TDS), that the breaking of the (weak) S-S bond of DMDS leads to the formation of a) Electronic mail: barmparis@materials.uoc.gr. two methanethiolate-surface bonds on Au(111) at low coverage.…”

Electron Transport through Cyclic Disulfide Molecular Junctions with Two Different Adsorption States at the Contact: A Density Functional Theory Study

“…36 It was also reported that dissociation of dimethyl disulfide (CH 3 SSCH 3 ) adsorbed on the Au(111) surface can be accomplished by applying a voltage of ∼1.4 V. 37 Existence of disulfide bonds has long been a controversy for alkanethiols and dialkyl disulfides adsorbed on gold surfaces. [37][38][39][40][41][42][43][44][45] Thus, we posed the following questions: What if the application of the bias voltage induces the formation or breakage of the disulfide bonds of 1? Would this conversion between cyclic and acyclic 1,2-dithiolane anchor groups alter the electron transport through 1, serving as an additional switching mechanism for 1 and affecting the robustness of the junction?…”