The aerosol impact spectrometer: a versatile platform for studying the velocity dependence of nanoparticle-surface impact phenomena

Abstract

A new apparatus designed to accelerate/decelerate and study the surface impact phenomena of charged aerosols and nanoparticles over a wide range of mass-tocharge (m/z) ratios and final velocities is described. A nanoparticle ion source coupled with a linear electrostatic trap configured as an image charge detection (ICD) mass spectrometer allows determination of the mass-to-charge ratio and the absolute charge and mass of single nanoparticles. A nine-stage linear accelerator/ decelerator is used to fix the final velocity of the nanoparticles, and in the results reported here the coefficient of restitution for polystyrene latex spheres (PSLs) impacting on silicon is measured using ICD techniques. To enable this apparatus to study a wide range of m/z, the data acquisition system uses a transient digitizer interfaced to a field-programmable gate array module that allows real time calculation of m/z and determination of the pulse sequence for the linear accelerator/decelerator. Electrospray ionization of a colloidal suspension of PSL spheres of 510 and 990 nm has been used to demonstrate acceleration and deceleration of charged nanoparticles and the resolution of the apparatus. Measurements of the coefficient of restitution for PSLs on silicon over the range 10-400 m/s are consistent with previous studies.

Experimental and theoretical investigation of overall energy deposition in surface-induced unfolding of protein ions

“…After this re-calibration, it is clear that energy deposition at higher laboratory frame collision energies is typically more efficient for SIU than for CIU, and SIU is more efficient for high-mass protein ions than for those with lower masses, reaching a maximum of ∼68% conversion to internal energy for the highest–energy transitions (using the CIU calibration with no cooling mechanism yields a value of ∼85%, which we interpret as an extreme upper bound for energy deposition in SIU). Computational results for collisions of dialanine with an FSAM surface suggest that a maximum of 16% of initial KE lab remains in translational modes after surface collision,35 leaving 84% or more of the energy to be partitioned between ion internal modes and the surface; an even lower fraction of the energy remains in translational modes for nanoscale polystyrene latex spheres after surface collision 54. Our maximum value falls within this upper bound, and suggests that energy transfer to internal modes dominates over energy transfer to the surface under these conditions.…”

Direct observation of ion emission from charged aqueous nanodrops: effects on gaseous macromolecular charging

“…Charge detection mass spectrometry (CDMS) can weigh individual ions well into the 100's of megadaltons (MDa) corresponding to molecules or molecular assemblies with diameters over 100 nm. [34][35][36][37][38][39][40] Sample heterogeneity and salt adduction can lead to overlapping ion signals that can prevent conventional mass spectrometry measurements of ion ensembles. 41,42 This problem with high sample heterogeneity is overcome with CDMS measurements of individual ions, making it an ideal technique for probing charged nanodrops.…”

Understanding Hypervelocity Sampling of Biosignatures in Space Missions

“…Although fragmentation upon impact with a hard surface can be mitigated by reducing the flyby speed of the spacecraft relative to the atmosphere, this compromises sampling signal intensities, collisional ionization strategies for analyzing dust, and may not be practical for certain planetary missions. Previous approaches to study these phenomena include efforts to relate organic fragmentation processes in analytical pyrolysis and ionizing fragmentation from laser or electron impacts (Wörgötter et al, 1997), dust accelerator experiments for organic particles (Goldsworthy et al, 2003;Srama et al, 2009), and more recently, by accelerating/decelerating charged aerosols and nanoparticles (Adamson et al, 2017).…”