Structure and dynamics of monolayers on planar and cluster surfaces

Abstract

Organized molecular assemblies have been one of the intensely pursued areas of contemporary chemistry. Among the various methodologies used to make organized monolayer structures, self-assembled monolayers (SAMs) have been attractive to many materials chemists owing to the simplicity of the preparative method and high stability. Advances in various techniques and their application in the study of SAMs have significantly improved our understanding of these molecular systems. These studies have been further intensified since the successful preparation of stable metal clusters protected with monolayers. This article reviews the structure, temperature-induced phase transitions, and associated dynamics of monolayers, principally in the context of our own work in this area. Alkanethiols on Au (111) and Ag(111) are taken as archetypal systems to discuss the properties of 2D SAMs; studies from our laboratory have been on evaporated thin films. Alkanethiols on Au and Ag cluster surfaces are taken as examples of 3D SAMs. Although our principal focus will be on alkanethiols, we will touch upon a few other adsorbate systems as well.

Self-assembled monolayers of thiols and dithiols on gold: new challenges for a well-known system

“…[272][273][274][275] The greater concentration of atoms at surface defects and the high radius of curvature of the cluster allow a larger proportion of the Au atoms to be on the cluster surface, which in turn results in a greater coverage of the thiol monolayer on the surface. 214,276,277 EXAFS data suggest that NP smaller than 5 nm have almost twice S (y = 2/3) as found on planar surfaces (y = 1/3). 276,277 As already discussed, 2 this high coverage has been attributed to the occupancy of alternative binding sites (edges and corners) and can be modeled both by simple geometric 18,278-280 and computational models.…”

Functionalized gold nanoparticles: Synthesis, structure and colloid stability

“…The characterization of structure and dynamics of SAMs on planar gold films (2D SAMs) is often limited by the small number of molecules present on the surface. Nanoparticles, however, can scale-up greatly the planar surface area, thus techniques such as calorimetry, transmission IR spectroscopy, dynamic NMR spectroscopy can be used to characterize the chain mobility and ordering of SAMs on nanoparticle surfaces (3D SAMs) [25,[40][41][42][43][44][45].…”

Atomistic Simulations of Self-Assembled Monolayers on Octahedral and Cubic Gold Nanocrystals

“…Other studies 17,[26][27][28][29][30][31][32][33] indicate that surface reconstruction may play an important role during the SAM formation with the presence of vacancies or single adatoms sitting on the flat surface. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 Experiment [34][35][36][37][38][39][40] and simulations [41][42][43][44][45][46][47][48][49][50] show marked differences between the SAMs on flat surface and nanocrystals. Thus, the average surface per thiolate is about 10 to 20 % smaller for Au NCs 35,<...>…”