ADVANCEMENTS IN PREPARATIVE MASS SPECTROMETRY TECHNIQUES USING HIGH THROUGHPUT MASS ANALYZERS

Ion soft landing is a preparative mass spectrometry technique that deposits mass- and charge-selected gas-phase ions onto surfaces at hyperthermal collision energies (<100 eV), preserving the molecular connectivity of polyatomic ions. This approach enables characterization of ions’ intrinsic properties at interfaces in the absence of contaminants, counterions, or solvent species. Most soft-landing applications involve the use of a quadrupole mass filter, which is compatible with hyperthermal energy ion beams. However, quadrupoles can only select single mass species from a multicomponent mixture, which limits throughput for rapid surface screening applications and functional design of substrates.

To address throughput limitations of preparative mass spectrometry, a compact mass dispersive analyzer has been developed that operates based on a rotating electric field. This device, termed a rotating wall mass analyzer (RWMA), is detailed in Chapter 2 with an emphasis on its enhanced mass-resolving capability from a high voltage phase-locked waveform generator. Furthermore, the RWMA is capable of high-mass analysis and can be utilized as an attractive candidate for mass analysis of charged nanodroplets produced from electrospray ionization, as described in Chapter 3. Due to the radial dispersive nature of the RWMA, ions are not deposited onto a concentrated surface location or spot, but rather in concentric ring patterns. To optimize ion coverage for soft landing applications, a designed open-faced Wien filter is described in Chapter 4 that enables parallel deposition from a multicomponent ion beam. Additionally, dynamic fields are applied to the Wien filter to enable one- and two-dimensional ion surface patterning. Collectively, the RWMA and dynamic field Wien filter enable simultaneous mass analysis from multicomponent ion beams to enhance throughput for rapid screening applications and design of well-defined surfaces in preparative mass spectrometry.

Finally, Chapter 5 explores a departure from ion soft landing, detailing the discovery of a metal-free, energy-efficient carbon-carbon synthesis of π-extended oligomers and their subsequent development into charge-transfer complexes. This work was conducted in collaboration with Dr. Jianguo Mei’s research team at Purdue University to characterize structures of novel organic conductive materials.