With this award from the Major Research Instrumentation (MRI) Program that is co-funded by the Chemistry Research Instrumentation and Facilities (CRIF) and the Chemical Measurements and Imaging (CMI) Programs, Professor Robert Continetti from the University of California San Diego will build a novel aerosol impact spectrometer (AIS). The AIS will provide a new experimental approach for the study of the chemistry of charged aerosol particles in the 50 nm to 1 micron size range, providing analysis of the chemical composition and morphology using both laser desorption ionization (LDI) and hypervelocity impact on an inert surface. The analytical process involves a series of carefully choreographed steps. The instrument will first trap particles/aerosols in a quadrupole ion trap, where they can be chemically modified if desired, and sequentially eject them into an image-charge mass spectrometer to determine the mass and charge state. The particles will then be accelerated to a high velocity prior to impact on a single-crystal diamond surface. Chemical analysis of charged products will be performed by time-of-flight mass spectrometry (TOF-MS) and neutral species desorbed on impact will be analyzed by vacuum ultraviolet laser photoionization TOF-MS. Variation of the velocity of impact will provide a new variable for studying the chemical properties of mass-resolved single particles as a function of depth, yielding a technique for aerosol studies analogous to the widely used secondary ion mass spectrometry (SIMS) technique that uses the impact of known ionic particles to characterize surfaces.
The chemistry of aerosols and nanoparticles has broad importance to understanding environmental and biological systems, and further development of techniques to understand the chemistry of particles as a function of size, such as mass spectrometry, is essential. Mass spectrometry vaporizes and ionizes a sample by a variety of methods. The particles (parent and fragment ions) flow into a mass spectrometer where their mass/charge ratios are measured. This highly sensitive technique allows determination of the masses of the particles, their chemical composition and enables one to deduce the structure of the substances in a complex mixture. The instrument that will be developed will apply a new analytical tool in mass spectrometry (hypervelocity impact) that will have broad application for the characterization of complex nanoparticles and aerosols at a single-particle mass-resolved level of detail. This will yield unique information on the chemistry of aerosols and particles and will be useful in fields as diverse as Chemistry, Biology and Environmental studies. The initial focus of the studies will be on atmospheric aerosols and biologically modified synthetic nanoparticles. This research project will also help train a new generation of instrumentalists in state-of-the-art techniques.
