Electron Irradiation Damage on thiol-protected gold nanoparticles during their charatecterization by TEM and XPS

AZCÁRATE, JULIO C.; E. ZELAYA; FONTICELLI, M. H.

San Carlos de Bariloche

Simposio; XXIII Latin American Symposium on Solid State Physics; 2018

CAB, Univ. Nac. de Río Negro

Thiol-capped gold nanoparticles (AuNP@SR) are widely studied and employed in dierent elds of basic and applied science. However, it is not always known in detail the structure and composition of those NPs. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are two advanced techniques used to characterize nanosystems. It is known that TEM can damage AuNP given coalescence of metallic neighbor cores.We determine that coalescence only occurs across 100 faces between AuNP@SR of 1-4 nm in size. At least the faces 100 should be free of thiolate moieties before cores coalescence. The main radiation damage mechanism is radiolysis rather than knock-on or temperature. The coalescence process implies the desorption of capping agent. To prove that thiol desorption, AuNP capped with dodecanethiol (DDT)and self-assembled monolayers of DDT on Au at surfaces were irradiated with electrons. The chemical changes induced by this irradiation were monitoredby XPS. The results revealed that thiolate moieties desorb as disulde species. The chemical kinetics of this process looks like a rst order reaction. Noticeably, the desorption is not complete, and a steady state is achievedwhere approximately the half of thiolate species still remain bonded to the surface. This result is consistent with the idea of preferential desorption of thiol from 100 faces rather than those bonded to the 111 faces.