Interaction of L-cysteine on Pd surface

L-cysteine, as an amino acid on the outer fringes of large proteins, can provide a link between those proteins and inorganic metal substrates. For the application of biomolecules (e.g., proteins) in electronic devices, it is essential to bond and organize the biomolecules on metals. L-cysteine presumably employs multiple functional groups (i.e., SH, NH2, and COOH) in its bonding to metal surfaces and anchors to the metal surface using either chemisorption (similar to thiolate-metal bonding) or physisorption (similar to the bonding to metal surfaces by the amino and carboxyl functional groups). These bonding strengths of L-cysteine, in particular the involvement of SH with the other functional groups, depend on the metallic partner properties. Therefore, an understanding of the interaction of L-cysteine with metal surfaces is necessary. Thus, in our previous studies, we have demonstrated different interaction strength and configurations of L-cysteine on the metallic surfaces of Au(111), Ag(111), and Cu(111) using ultraviolet photoemission spectroscopy (UPS) and in this study, the interface electronic structure of L-cysteine and Pd is systematically elucidated by UPS.