Directed Self-Assembly to Create Molecular Terraces with Molecularly Sharp Boundaries in Organic Monolayers

Abstract

We demonstrate the ability to control the placement of molecules within self-assembled films. We show quasi-two-dimensional mosaic structures within two-component self-assembled monolayers. These demonstrate new types of monolayer features: the domains of each component form molecular terraces, and the boundaries between these domains form molecular step edges. We find the molecular step edges are molecularly sharp and laterally epitaxial. The molecular step edges have the unique ability to expose a typically buried part of the larger molecule at the boundary. For the identical components in the crystalline monolayer, we can also distribute the molecules randomly. These structures were selected and created using simple controlled sequences of self-assembly and processing with different length alkanethiols on Au{111}. We have imaged these films using molecular resolution scanning tunneling microscopy.

Nitrosoarene Dimerization on Two- and Three-dimensional Gold Surfaces

“…40 Following the usual room temperature assembly process, the molecular film was annealed in an ethanolic solution of compound 1 for 1 h at 78 °C. 41 By comparing morphology characteristics before ( Figure 1b) and after an annealing step (Figure 1c), a decrease in a number of vacancy islands and an increase in domain size were observed which is consistent with the Ostwald ripening process. 42 However, although domain size was increased we could not observe any long range molecular order within the adlayer of compound 1.…”

Molecular, Supramolecular, and Macromolecular Motors and Artificial Muscles

“…3 These defects and their densities can be controlled by processing the matrix. 37,38 After exposing the alkanethiolate SAMs to guest molecules either in solution, vapor, or by contact (e.g., with a patterned polymer stamp), single molecules can be selectively inserted at the defect sites. 3,23,26,27,30,31,[39][40][41][42][43][44][45] Due to physical constraints from the surrounding matrix and (optional) designed intermolecular interactions, the inserted molecules are limited in their motion and stabilized in specific conformations.…”

Communication: Site-dependent reactivity between chlorine atoms and mixed-chain-length alkanethiolate monolayers

“…The experiments described in this Communication follow the methods pioneered by Weiss and co-workers for creating and characterizing various well-ordered and phase-separated coadsorbed thiolate monolayers using STM. [18][19][20] This involves initial formation of a monolayer, followed by partial desorption and "filling in" of the vacancies created with a different thiolate species.…”

“…In particular, a three-methylene difference in the alkane chains gives an observed height difference larger than that of a gold substrate step to help simplify STM image interpretation. Two CH 2 groups create some ambiguity, as the tilt angle of ∼30 • and the relatively insulating nature of the alkane chain gives an apparent topographic height of 2.2 Å, 18 very close to the Au substrate step height of 2.35 Å. On the other hand, a four-or-more CH 2 difference in chain length made STM scanning prone to instabilities.…”

“…As observed by Weiss and co-workers, these islands can either have sharp borders with the close-packed 8-thiolate areas or be adjacent to the domain boundaries of the 8-thiolate SAM. 18 The experimental apparatus and procedure have been previously described in detail. 15 Essentially, before the start of Cl-atom exposure, a monitoring area on the sample is chosen and scanned multiple times to ensure that both the area and the STM tip are stable.…”