An XPS Study of the Ag-S interface of L-Cysteine Films on Silver Surface

Authors

G. D. K. V. Maduwantha, Department of Engineering Technology, Faculty of Technology, Sabaragamuwa University of Sri Lanka, Belihuloya 70140, Sri Lanka\\ Center for Nanodevices Fabrication and Characterization, Faculty of Technology, Sabaragamuwa University of Sri Lanka, Belihuloya 70140, Sri LankaFollow
Chathudina Janitha Liyanage, Department of Food Science and Technology, Faculty of Applied Sciences, Sabaragamuwa University of Sri Lanka, Belihuloya 70140, Sri Lanka\\ Center for Nanodevices Fabrication and Characterization, Faculty of Technology, Sabaragamuwa University of Sri Lanka, Belihuloya 70140, Sri LankaFollow
Kaveenga Rasika Koswattage, Department of Engineering Technology, Faculty of Technology, Sabaragamuwa University of Sri Lanka, Belihuloya 70140, Sri Lanka\\ Center for Nanodevices Fabrication and Characterization, Faculty of Technology, Sabaragamuwa University of Sri Lanka, Belihuloya 70140, Sri LankaFollow

Abstract

L-cysteine has gained much attention as a versatile amino acid to create bioactive surfaces by assisting the bonding of proteins to metal surfaces. When L-cysteine interacts with metallic partners such as gold, silver and copper, the SH functional group is known to interact strongly with the metallic surface. The interaction of the L-cysteine with silver surfaces is particularly interesting because, L-cysteine adsorption on silver has been suggested to be stronger than on gold or copper surfaces and the interactions may strongly influence the formation of novel interface states of the L-cysteine-Ag interface. On the other hand, some studies report a weakening of silver-sulfur bond with increasing coverage. However, research has not been sufficiently addressed for experimental investigation to understand the interaction of L-cysteine with silver metallic surfaces. As the first step, we reported the results of experimental investigation of L-cysteine and silver interface electronic structure by thickness-dependent ultraviolet photoelectron spectroscopy (UPS) with a clear spectral feature in between Fermi edge and highest occupied molecular orbital (HOMO) of L-cysteine due to the formation of Ag-S bonding together with a weakening of the silver-sulfur bond with increasing of L-cysteine. In this study, the formation of Ag-S bond at the L-cysteine modified silver surface was systematically elucidated by X-ray photoelectron spectroscopy (XPS) for three different coverages, namely monolayer, two-layered and multi-layered. A prominent shoulder at 2475.2 eV of the main peak at 2473.2 eV was observed for the S 1s XPS spectrum for monolayer film, while only a single peak was observed in the case of two- layered and multi-layered. The spectral feature at 2475.2 eV can be attributed to the interaction of L-cysteine with silver. In addition, the disappearance of the spectral feature for the two-layered film can be attributed to the weakening of silver-sulfur bond by over layer of L-cysteine.

Recommended Citation

D. K. V. Maduwantha, G.; Janitha Liyanage, Chathudina; and Rasika Koswattage, Kaveenga (2023) "An XPS Study of the Ag-S interface of L-Cysteine Films on Silver Surface," International Journal of Thin Film Science and Technology: Vol. 12 : Iss. 1 , PP -.
Available at: https://digitalcommons.aaru.edu.jo/ijtfst/vol12/iss1/9