Preparative Mass Spectrometry: Instrumentation and Applications
Ion soft landing is a preparative mass spectrometry technique that enables intact deposition of polyatomic ions onto surfaces. The ability to select ions with well-defined mass, charge, and kinetic energy, along with precise control over size, shape, and position of the ion beam in the deposition process distinguishes ion soft landing from traditional synthetic and surface preparation approaches. A wide range of projectile ions including molecular ions, non-covalent complexes, clusters, and ionic fragments generated in the gas phase have been used in soft-landing studies to address both the fundamental questions related to ion-surface interactions and enable applications of hyperthermal beams.
Since the first soft landing instrument was implemented by Cooks and co-workers in 1977, significant advances have been achieved in preparative mass spectrometry instrumentation. Current instrument development efforts are focused on obtaining high ion currents, increasing the experimental throughput, and developing capabilities for layer-by-layer deposition. In chapter 2 and 3, two novel instrumentation approaches are introduced, which improve the ion flux and experimental throughput of ion soft landing research. In particular, soft landing of ions of both polarities enables the bottom-up construction of ionic materials. Meanwhile, a rotating wall mass analyzer substantially increases the mass range of mass-selective deposition and disperses multiple species on the same surface thereby increasing the experimental throughput. These instrumentation developments open up the opportunities to explore research topics in the field of catalysis, energy storage and production, biology, and quantum sciences.
In chapter 4, I describe a novel in situ spectroelectrochemistry approach for studying structural changes of electroactive species during electrochemical processes. In these experiments, ion soft landing is used to prepare well-defined ions at electrochemical interfaces. In addition, understanding of the gas-phase properties of cluster ions is important for their application in ion soft landing research. Ions can be prepared in the proper physical and chemical state via gas-phase chemistry approaches, and the favorable properties and reactivities of ions can thereby be harnessed using ion soft landing. In chapter 5 and 6, gas phase properties of host-guest complexes of cyclodextrins and polyoxometalates and molybdenum halide clusters are discussed.