Collisional activation and reactions of low-energy ions at fluorinated self-assembled monolayer surfaces

Bingbing Feng, Purdue University

Abstract

Several physical and chemical processes occur during inelastic low energy (less than 100 eV) ion/surface collisions at fluorinated self-assembled monolayer (F-SAM) surfaces. Among them, surface collisional activation and chemical reactions of a large variety of ions were investigated. Over a wide range of collision energies, differentiation of isomeric allene and propyne molecular ions are achieved and projectile translational to internal energy partitioning in surface-induced dissociation (SID) are carefully studied. Upon mild collisional activation of nickelocene molecular ion, nickeldihydride radical cation is formed. Experimental observations suggest that nickeldihydride ion formation involves vibrational excitation of the molecular ion and cyclopentadienyl ring fusion in concert with intramolecular hydrogen rearrangement. Abstraction of single or multiple fluorine atoms, and fluorocarbon groups from F-SAM surfaces were observed as a result of surface C-F and C-C bond activation by monatomic and polyatomic ions containing group IIIA to VIIIA elements. For polyatomic ions, SID usually occurs prior to ion/surface reactions and their fragments are often more reactive than the undissociated projectile ions. Ion/surface reaction mechanisms are proposed in light of projectile SID, chemical sputtering, product collisional energy dependence, ion/surface reaction enthalpies, and analogous gas phase experiments. It is found that in many cases fluoronium reaction intermediates are responsible for observed ion/surface reactions. Chemical modification of F-SAM surfaces, as examined by in situ chemical sputtering and independent TOF-SIMS studies, have been accomplished through ion/surface transhalogenation reactions and very low energy (less than 15 eV) soft-landing of polyatomic ions.

Degree

Ph.D.

Advisors

Cooks, Purdue University.

Subject Area

Analytical chemistry

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