Experimental evidence for internal structure in aqueous–organic nanodroplets

Wyslouzil, Barbara E.; Wilemski, Gerald; Strey, R.; Heath, Christopher H.; Dieregsweiler, Uta

doi:10.1039/b514824c

Cited by 48 publications

(51 citation statements)

References 18 publications

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“…Many organic compounds have very low solubilities in water, and, as a result, these mixtures display miscibility gaps separating water-rich and organic-rich phases within the droplet. [6][7][8] In particular, surface active components are likely to form films covering the droplets, [8][9][10] and indeed Tervahattu et al found evidence that fatty acids form a surface coating on marine aerosol particles. 11,12 Aqueousorganic aerosol droplets may also adopt radically different structures depending on their overall composition, on the solubility of organic compounds in the aqueous phase, and on the relative humidity.…”

Section: Introductionmentioning

confidence: 99%

The structure of D2O-nonane nanodroplets

Pathak

Obeidat

Wilemski

et al. 2014

The Journal of Chemical Physics

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We study the internal structure of nanometer-sized D2O-nonane aerosol droplets formed in supersonic nozzle expansions using a variety of experimental techniques including small angle X-ray scattering (SAXS). By fitting the SAXS spectra to a wide range of droplet structure models, we find that the experimental results are inconsistent with mixed droplets that form aqueous core-organic shell structures, but are quite consistent with spherically asymmetric lens-on-sphere structures. The structure that agrees best with the SAXS data and Fourier transform infra-red spectroscopy measurements is that of a nonane lens on a sphere of D2O with a contact angle in the range of 40°-120°.

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Section: Introductionmentioning

confidence: 99%

The structure of D2O-nonane nanodroplets

Pathak

Obeidat

Wilemski

et al. 2014

The Journal of Chemical Physics

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“…One significant consequence of this difference is that rather than developing the core-shell structures favored by the amphiphilic compounds, 36 D 2 O-water nanodroplets favor a lens-on-sphere structure. 12,13 Thus, the higher condensation coefficients estimated here are consistent with a droplet structure that exposes at least some regions that favor water condensation.…”

Section: B Binary Nucleation and Condensationmentioning

confidence: 99%

Co-condensation of nonane and D2O in a supersonic nozzle

Pathak

Wölk

Strey

et al. 2014

The Journal of Chemical Physics

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We study the unary and binary nucleation and growth of nonane-D2O nanodroplets in a supersonic nozzle. Fourier Transform Infrared spectroscopy measurements provide the overall composition of the droplets and Small Angle X-ray Scattering experiments measure the size and number density of the droplets. The unary nucleation rates Jmax of nonane, 9.4 × 10(15) < Jmax /cm(-3) s(-1) < 2.0 × 10(16), and those of D2O, 2.4 × 10(17) < Jmax /cm(-3) s(-1) < 4.1 × 10(17), measured here agree well with previous results. In most of the binary condensation experiments new particle formation is dominated by D2O, but the observed nucleation rates are decreased by up to a factor of 6 relative to the rates measured for pure D2O, an effect that can be partly explained by non-isothermal nucleation theory. The subsequent condensation of D2O is inhibited both by the increased temperature of the binary droplets relative to the pure D2O droplets, and because the binary droplet surface is expected to be comprised largely of nonane. For the one case where nonane appears to initiate condensation, we find that the nucleation rate is about 50% higher than that observed for pure nonane at comparable pv0, consistent with significant particle formation driven by D2O.

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“…The determination of the physical and optical properties of aerosols is necessary to further understand aerosol contribution to these effects. There is evidence to suggest that aerosols coated with a thin film of organic material are prevalent in the troposphere [2][3][4][5][6][7] . Mineral dust is a common source of solid aerosol 8,9 that is produced by wind action and can become coated with organic material such as lipids 9 arising from plant matter.…”

Section: Introductionmentioning

confidence: 99%

The study of thin films on solid aerosol particles using optical trapping and Mie scattering from a broadband white LED

2014

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A counter-propagating optical trap has been used to study thin organic films on the surface of solid particles levitated in air. Micron sized silica spheres have been trapped in air between opposed 1064 nm laser beams, and illuminated with a broadband white LED. Backscattered light from the trapped particle was collected to obtain a Mie spectrum over the 495-670 nm wavelength range and this was used to determine particle radius and wavelength dependent refractive index (Jones et al., 2013). The trapped particle was coated using a flow of organic vapour and the resultant thin film analysed using a coated sphere model. Resonance positions in the Mie spectrum were monitored with time in order to determine film formation, thickness and refractive index. Whilst thin films are believed to form naturally on atmospheric aerosols (Tervahattu et al., 2002), a debate remains as to whether the organic component completely coats the aerosol surface or partially engulfs it. Such films are readily oxidised in the atmosphere causing a change in aerosol properties and knowledge of aerosol properties is required to understand their effect on the climate. The use of optical trapping combined with Mie spectra acquisition to study and characterise coated solid particles is therefore an important step in atmospheric science.

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Experimental evidence for internal structure in aqueous–organic nanodroplets

Cited by 48 publications

References 18 publications

The structure of D2O-nonane nanodroplets

The structure of D2O-nonane nanodroplets

Co-condensation of nonane and D2O in a supersonic nozzle

The study of thin films on solid aerosol particles using optical trapping and Mie scattering from a broadband white LED

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