Self-Assembly of (S)-Glutamic Acid on Ag(100): A Combined LT-STM and Ab Initio Investigation

Self-assembly of organic molecules at metal surfaces is of greatest importance in nanoscience; in fact, it opens new perspectives in the field of molecular electronics and in the study of biocompatible materials. Combining an experimental low-temperature scanning tunneling microscopy investigation with ab initio calculations, we succeeded to describe in detail (S)-glutamic acid adsorption on Ag(100) at T=350 K. We find that (S)-glutamic acid organizes in a squared structure and, at variance with the majority of cases reported in literature, it adsorbs in the neutral form, 4.6A ° above the surface plane. The interaction with the poorly reactive Ag substrate is only due to weak van der Waals forces, while H-bonds between carboxyl groups and the formation of aOCOH-OCOH-OCOH-OCOH cycle at the vertex of the squares are the main responsible for the self-assembly.