Grant Johnson - In Situ Reactivity and TOF-SIMS Analysis of Surfaces Prepared by Soft and Reactive Landing of Mass-Selected Ions

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      Volume:   82

        Issue: 13

        Pages: 5718-5727


    Published: JUL 1 2010


        An instrument has been designed and constructed that enables in   situ reactivity and time-of-flight secondary ion mass   spectrometry (TOF-SIMS) analysis of surfaces prepared or modified   through soft and reactive landing of mass-selected polyatomic   cations and anions. The apparatus employs an electrospray ion   source coupled to a high transmission electrodynamic ion funnel,   two focusing collision quadrupoles, a large 19 mm diameter   quadrupole mass filter, and a quadrupole bender that deflects the   ion beam, thereby preventing neutral contaminants from impinging   on the deposition surface. The ion soft landing apparatus is   coupled to a commercial TOF-SIMS instrument permitting the   introduction of surfaces into vacuum and SIMS analysis before and   after ion deposition without breaking vacuum. To facilitate a   comparison of the current TOF-SIMS instrument with the in situ   Fourier transform ion cyclotron resonance (FTICR-SIMS) deposition   apparatus constructed previously, dications of the cyclic peptide   Gramicidin S (GS) and the photoactive organonometallic complex   ruthenium tris-bipyridine (Ru-(bpy)(3)) were soft-landed onto   fluorinated self-assembled monolayer (FSAM) on gold surfaces. In   both cases, similarities and differences were observed in the   secondary ion mass spectra, with the TOF-SIMS results, in   general, characterized by greater sensitivity, larger dynamic   range, less fragmentation, and fewer in-plume reactions than the   corresponding FTICR-SIMS spectra. The charge reduction kinetics   of both the doubly and singly protonated GS cations on the FSAM   surface were also examined as was the influence of the primary   gallium ion (Ga(+)) flux on the efficiency of these processes. In   addition, we demonstrate that the new instrument enables detailed   studies of the reactivity of catalytically active species   immobilized by soft and reactive landing toward gaseous   reagents.

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