Ion soft-landing is a mass spectrometry-based deposition method that delivers intact and pure molecular ions onto a surface with kinetic energy in the hyperthermal range (1–100 eV). This gentle deposition process is analogous to molecular beam epitaxy but uses charged species instead of neutral molecules. Ion soft-landing provides access for deposition of a wide range of both stable and chemically labile charged species, from small atomic ions to large protein complexes in the megadalton mass range. However, its ion currents are substantially lower than typical fluxes of neutral molecules used in molecular beam epitaxy, therefore, ion soft-landing has been mainly used for preparing monolayers on small conductive or semiconductive substrates. To address this challenge, we developed a multiplexed electrospray ionization interface with improved ion transmission and achieved high-flux ion soft-landing that decreases the deposition time substantially.
Multiplexing of Electrospray Ionization Sources Using Orthogonal Injection into an Electrodynamic Ion Funnel, Analytical Chemistry, 2021, 93, 33, 11576-11584, https://doi.org/10.1021/acs.analchem.1c02092.
Pei Su, Xi Chen, Andrew J. Smith, Michael F. Espenship,Hugo Y. Samayoa-Oviedo, Solita M. Wilson, Habib Gholipour-Ranjbar, Carlos Larriba-Andaluz and Julia Laskin
Below is a brief description of ongoing projects with ion soft-landing instruments developed in Prof. Julia Laskin Lab:
Deposition of ultrathin films of nanoclusters through ion soft-landing
For superatomic clusters to be effectively utilized in most of the applications, its necessary to prepare them on an appropriate substrate. The present approach for preparing cluster assembled materials (CAMs) is the self-assembly method which requires highly pure clusters with a similar size and symmetry as well as interaction to produce the target structure. Since providing all the required conditions for spontaneous self-assembly of clusters is challenging, only a few CAMs have been prepared so far. To address this challenge and introduce a well-defined deposition method to a broad range of nanoclusters for both fundamental and applied research, I am using a dual-polarity ion soft-landing instrument which is ideally suited for preparing uniformly distributed nanoclusters with specific composition, charge state, kinetic energy, and purity.
Nanocluster activation through ion soft-landing
Activation of ligated nanoclusters (NCs) through the controlled surface ligand removal is one of the challenges in materials science. This is commonly achieved using aggressive physical treatments such as thermal pyrolysis or chemical etching. However, ligand removal using these approaches is difficult to control, which limits their utility. To address this challenge, we use an ion soft-landing instrument equipped with a collision cell, which enables the controlled removal of surface ligands from ligated NCs for understanding their reactivity on surfaces. I have been able to generate reactive fragments of metal chalcogenide clusters ligated with triethylphosphine (PEt3) and demonstrate that their gas-phase stability towards ligand loss is an excellent indicator of their reactivity on surfaces.
