Soft Deposition of Organic Molecules Based on Cluster-Induced Desorption for the Investigation of On-Surface and Surface-Mediated Reactions.

Abstract

Desorption/ionization induced by neutral clusters (DINeC) was employed for the soft transfer of organic and biomolecules, such as porphyrins and peptides, from a bulk sample onto any substrate of choice. Qualitative analysis of the deposition technique was performed by means of mass spectrometry, demonstrating that the deposited molecules remained intact due to the soft nature of the transfer process. Deposition rates were studied quantitatively using a quartz crystal microbalance; layers of intact biomolecules ranging from the submonolayer regime up to a few monolayers in thickness were realized. Mixed layers of molecules were deposited when two different sources of molecules were employed. The samples which were prepared based on this soft deposition method were used for the investigation of reactions of the deposited molecules with either coadsorbates on the surface or the surface itself. Examples include adduct formation of peptides with alkali metals on SiO2, the oxidation of peptides exposed to oxygen, as well as the metallization of porphyrins in interaction with the substrate.