Assistant Professor Rachael Farber named November 2024 Sutton Family Research Impact Award recipient
The Department of Chemistry congratulates Assistant Professor Rachael Farber on receiving the November 2024 Sutton Family Research Impact Award!
The Sutton Award is a monthly competition among chemistry faculty. Every month, the Chemistry Department Chair and Associate Chairs review the peer-reviewed papers published by chemistry faculty from the three previous months to select a winner. The recipient receives a $500 cash prize and is featured on the departmental website.
For a full list of winners, visit our Sutton Family Research Impact Award webpage.
Influence of hydrogen-bonded 3-mercaptopropionic acid bilayers on binary self-assembled monolayer formation
By Lindsey N. Penland, H. H. Hirushan, N. Dissanayake, and Rachael G. Farber
J. Vac. Sci. Technol. A 42, 63205 (2024). DOI: 10.11166.0003926
Self-assembled monolayers (SAMs) are widely used for their ability to tune the interfacial properties of metal surfaces. Molecular control over interfacial properties can be further enhanced by introducing a second molecular species, resulting in a binary SAM. Binary SAMs can be prepared using a mixed solution to co-adsorb the two species on the surface or through the displacement of one molecule by another. Displacement leverages the fact that long chain alkyls can displace shorter chain alkyls due to increased Van der Waals forces between alkyl tail groups. While there are studies that show long chain alkanethiols can displace SAMs that are stabilized through hydrogen bonding, there is little research on how the presence of a hydrogen bonded bilayer influences displacement rates.
In this work, we investigated how monolayer order, defect density, and bilayer formation impact displacement behavior of 3-mercaptopropionic acid (MPA) by 1-decanethiol (DT). Ultra-high vacuum scanning tunneling microscopy analysis of pristine, moderately defected, and bilayer MPA SAMs confirm that well-ordered, pristine MPA SAMs are displaced at slower rates than MPA SAMs with less long-range order and greater defect density. Interestingly, MPA samples containing regions of an MPA bilayer displayed the slowest rates of displacement with DT. For pristine MPA samples and MPA samples with regions of an MPA bilayer, displacement with DT resulted in the formation of the low density, lying down phase of DT. These results suggest that the presence of an MPA bilayer, which forms due to hydrogen bonding between carboxylic acid groups in MPA, significantly lowers the rate of total displacement of MPA by DT compared to moderately defected MPA SAMs. These results highlight the importance of structure, composition, and intermolecular forces, such as hydrogen bonding, when considering binary SAM formation via solution-phase displacement methods.
