Ab Initio Studies of the Electronic Structure of L-Cysteine Adsorbed on Ag(111)

N.B. LUQUE; P. VÉLEZ; K. PÖTTING; E. SANTOS

LANGMUIR

AMER CHEMICAL SOC

Lugar: Washington; Año: 2012 vol. 28 p. 8084 - 8099

0743-7463

We have performed ab initio calculations for the adsorption of L-cysteine onAg(111) using density functional theory. We have focused on two possible adsorbed species:the L-cysteine radical (•S−CH2−CH−NH2−COOH) adsorbed almost flat at a bridge site,slightly displaced toward an fcc location, and the zwitterionic radical Z-cysteine (•S−CH2−CH−NH3+−COO−) adsorbed at a bridge site, shifted to a hcp site forming a (4 × 4) unit cell(θ = 0.06) and a (√3 × √3) R 30° unit cell (θ = 0.33), respectively. Special attention hasbeen paid to the electronic structure of the system. The adsorbate−silver bond formation hasbeen exhaustively investigated by analyzing the density of states projected onto the differentatoms of the molecule, and by charge density difference calculations. A complicated interplay between sp and d states of silver in the formation of bonds between the adsorbates and the surface has been found. The role of the carboxyl group in the interaction with the surface has been also analyzed.