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.

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Understanding that life on this planet may have originated under extreme circumstances, such as high temperatures and acidic conditions, it would be extremely beneficial to study how simple biological molecules, like amino acids, behave under these scenarios. Importantly, this is possible through the use of electrochemical scanning tunneling microscopy, which can be used to both image and electrochemically manipulate the model systems under consideration. Earlier reports have examined the similarities between studies conducted at ultrahigh vacuum or low temperature and electrochemical conditions with both finding that amino acid molecules trap diffusing metal atoms on surfaces to form 2D ad-islands. Critically, all of the past work was conducted at room temperature. In this report, it has been found that as the temperature of the Au(111) surface was increased, the islands grew by 14% at 300 K and 40% at 305 K, relative to room temperature. Additionally, the increased surface temperature allowed for the formation of islands that were one atomic step higher than those observed at room temperature. Higher surface temperatures not only allowed for the observation of larger immobilized adatom islands, but they also demonstrated how temperature can be used as another method to control surface modification and molecular assembly. Not only is this work critical for a basic understanding of the role between temperature and surface diffusion, but it also begins to mimic how surfaces may have behaved during the emergence of life on Earth.

A clear description of how surface morphology is affected by the bonding of biomolecules with metal surfaces is critical to identify due to the potential applications in microelectronics, medical devices, and biosensors. Amino acids (AAs) on bare Au(111) were previously observed to trap Au adatoms, eventually leading to the formation of one atom high metal islands. To better understand the role of surface identity, L-isoleucine on Au(111) modified with a Ag thin film was investigated at ambient conditions with electrochemical scanning tunneling microscopy. The mere presence of an Ag monolayer drastically changed the amino acid/surface interactions despite the chemical similarity of Au and Ag. The adsorption of the AAs on the Ag monolayer drastically altered the surface and caused significant surface roughening distinct from 2D growth which had previously existed only on top of the surface. This roughening occurred layer-by-layer and was not restricted to the first layer of the surface as seen with sulfur containing molecules. Notably, this study demonstrates surface roughening that is occurring under extremely mild conditions highlighting the ability of Ag thin films to markedly alter surface chemistry in concert with biomolecules.