Using EC-STM to obtain an understanding of amino acid adsorption on Au(111)

Abstract

With increasing interest into the origin of life as well as the advancement of medical research using nanostructured architectures, investigations into amino acid assemblies have increased heavily in the field of surface science. Amino acid self/assisted-assembly on metallic surfaces is typically investigated with Scanning Tunneling Microscopy at low temperatures and under ultra-high vacuum in order to maintain a pristine surface and to provide researchers the tools to atomically interrogate the surface. However, in doing so, results often tend to be uncertain when moving to more realistic conditions. The investigation presented focuses on the electrochemical STM study of five simple amino acids as well as two modifications of a single amino acid and the means by which they interact with Au(111). Using EC-STM under in situ conditions, the amino acids were shown to have a considerable interaction with the underlying surface. In all cases, the amino acids trapped diffusing adatoms to form islands. These findings have also been observed under UHV conditions, but this is the first demonstration of the correlation in situ. Results indicate that an increase in the molecular footprint of the amino acid had a subsequent increase in the area of the islands formed. Furthermore, by shifting from a nonpolar to polar side chain, island area also increased. By analyzing the results gathered via EC-STM, fundamental insight can be gained into not only the behavior of amino acids with the underlying surface, but also into the direct comparison of LT-UHV-STM data with imaging performed under ambient conditions.

Observing Electrocatalytic Processes via In Situ Electrochemical Scanning Tunneling Microscopy: Latest Advances

“…It should be noted that many EC‐STM analyses of small molecule adsorption/desorption, such as glycerol adsorption on Cu(111), [32] amino acid on Au(111), [33] and CO 2 on metal porphyrin, [34] do not involve electrocatalysis. Therefore, they may not be as informative as in situ EC‐STM studies.…”