Solvent and cosolute dependence of Mg surface enrichment in submicron aerosol particles

Abstract

The formation of multicomponent aerosol particles from precursor solution droplets often involves segregation and surface enrichment of the different solutes, resulting in non-homogeneous particle structures and diverse morphologies. In particular,...

Surface composition of size-selected sea salt particles under the influence of organic acids studied in situ using synchrotron radiation X-ray photoelectron spectroscopy

“…This is interpreted as a 10-20-fold surface enrichment of Mg, since at these photoelectron kinetic energies XPS gives information only from the depth of first 1-2 nm from the particle surface. In a similar experiment by Pelimanni et al on particles produced via atomisation of aqueous binary salt mixtures of MgBr 2 and NaBr, Mg was observed to be highly enriched over Na 25 . When they atomised an aqueous solution of MgCl 2 and CaCl 2 , the particles produced did not show any surface enrichment, but the Mg-to-Ca corresponded well to the bulk ratio at all relative concentrations of MgCl 2 and CaCl 2 salts studied.…”

“…In a similar experiment by Pelimanni et al on particles produced via atomisation of aqueous binary salt mixtures of MgBr 2 and NaBr, Mg was observed to be highly enriched over Na. 25 When they atomised an aqueous solution of MgCl 2 and CaCl 2 , the particles produced did not show any surface enrichment, but the Mg-to-Ca corresponded well to the bulk ratio at all relative concentrations of MgCl 2 and CaCl 2 salts studied. This behaviour showed a better correlation with differences in efflorescence dynamics than solubilities of these salts, which has also been discussed to be one factor driving the surface segregation.…”

“…For example, today it is possible to carry out high resolution experiments in the gas phase on atmospheric precursor molecules and clusters 15,16 and size-selected cluster ions 17 , follow reactant formation isomer-selectively 18 , and image single aerosol particles 19 . Synchrotron radiation XPS studies of atmospheric aerosols span the range from organic droplets 20 to soot particles 21 and inorganic salt systems [22][23][24][25] . Recently, we reported a XPS study on free-flying nanoparticles generated with an atomiser from a model sea salt aqueous solution 26 .…”

“…19 Synchrotron radiation XPS studies of atmospheric aerosols span the range from organic droplets 20 to soot particles 21 and inorganic salt systems. [22][23][24][25] Recently, we reported an XPS study on free-ying nanoparticles generated with an atomiser from a model sea salt aqueous solution. 26 The results indicated that dried particles had a core-shell structure, which can be modied through the addition of an organic acid.…”

Bridging Gaps between Clusters in Molecular-Beam Experiments and Aerosol Nanoclusters

“…Co-expansion and pickup MB methods discussed above can already produce multicomponent clusters mimicking complex aerosols. However, species which are not easy to evaporate are difficult to incorporate into clusters in MB, yet they are indispensable components of many aerosol particles, e.g., salts in sea-spray aerosols. ,,,, Aerosol particles can be generated directly from liquid salt solutions using an atomizer and transferred into a MB with an aerodynamics lens; however, the sizes of such particles are typically in the 10 2 nm range. Electrospray ionization (ESI) is ideally suited for the generation of salt–solution clusters, yet it produces charged clusters while the majority of atmospheric aerosol particles are neutral.…”