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We apply liquid nebulization (LN) in series with ion mobility spectrometry (IMS, using a differential mobility analyzer coupled to a condensation particle counter) to measure the size distribution functions (the number concentration per unit log diameter) of gold nanospheres in the 5-30 nm range, 70 nm × 11.7 nm gold nanorods, and albumin proteins originally in aqueous suspensions. In prior studies, IMS measurements have only been carried out for colloidal nanoparticles in this size range using electrosprays for aerosolization, as traditional nebulizers produce supermicrometer droplets which leave residue particles from non-volatile species. Residue particles mask the size distribution of the particles of interest. Uniquely, the LN employed in this study uses both online dilution (with dilution factors of up to 104) with ultra-high purity water and a ball-impactor to remove droplets larger than 500 nm in diameter. This combination enables hydrosol-to-aerosol conversion preserving the size and morphology of particles, and also enables higher non-volatile residue tolerance than electrospray based aerosolization. Through LN-IMS measurements we show that the size distribution functions of narrowly distributed but similarly sized particles can be distinguished from one another, which is not possible with Nanoparticle Tracking Analysis in the sub-30 nm size range. Through comparison to electron microscopy measurements, we find that the size distribution functions inferred via LN-IMS measurements correspond to the particle sizes coated by surfactants, i.e. as they persist in colloidal suspensions. Finally, we show that the gas phase particle concentrations inferred from IMS size distribution functions are functions of only of the liquid phase particle concentration, and are independent of particle size, shape, and chemical composition. Therefore LN-IMS enables characterization of the size, yield, and polydispersity of sub-30 nm particles.
Bibliographical noteFunding Information:
This work was supported by US National Science Foundation Award CBET-1133285 (for the purchase of samples, reagents, and operation of the LN-IMS system) as well as United States Army Research Office Award MURI W911NF-12-0407 (to support S. Jeon). Electron microscopy was performed at the College of Science and Engineering Characterization Facility, University of Minnesota (UMN), which receives funding from the National Science Foundation through the UMN MRSEC under Award DMR-1420013.
How much support was provided by MRSEC?
Reporting period for MRSEC
- Period 3
PubMed: MeSH publication types
- Journal Article
- Research Support, U.S. Gov't, Non-P.H.S.