Size dependence of phase transitions in aerosol nanoparticles

Cheng, Yafang; Su, Hang; Koop, Thomas; Mikhailov, Eugene; Pöschl, Ulrich

doi:10.1038/ncomms6923

Cited by 160 publications

(216 citation statements)

References 47 publications

(72 reference statements)

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“…Using XPS and NEXAFS spectroscopies of the O 1s core level and O K-edge, respectively, we previously showed that these systems follow the phase rules at the airice interface [52]. This finding contrasts some earlier observations, where the presence of liquid-like Cl below the eutectic point of bulk solutions [53] was postulated (see Ref. [46] and references therein).…”

Section: Phase Changes Of Nacl-water Binary Systemsmentioning

confidence: 69%

The Environmental Photochemistry of Oxide Surfaces and the Nature of Frozen Salt Solutions: A New in Situ XPS Approach

et al. 2016

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Recent years have witnessed fast advancements in near ambient pressure X-ray photoelectron (NAPP) spectroscopy, which is emerging as a powerful tool for the investigation of surfaces in presence of vapors and liquids. In this paper we present a new chamber for the investigation of solid/vapor interfaces relevant to environmental and atmospheric chemistry that fits to the NAPP endstation at the Swiss Light Source. The new chamber allows for performing X-ray photoelectron spectroscopy (XPS) and electron yield near-edge X-ray absorption fine structure spectroscopy (NEXAFS) using soft, tender and hard X-ray in vacuum and in near-ambient pressures up to 20 mbar at environmentally relevant conditions of temperature and relative humidity. In addition, the flow tube design of the chamber enables the dosing of sticky reactive gases with short pressure equilibration time. The accessible photoelectron kinetic energy ranges from 2 to 7000 eV. This range allows the determination of surface and bulk electronic properties of ice and other environmental materials, such as metal oxides and frozen solutions, which are relevant to understanding atmospheric chemistry. The design of this instrument and first results on systems of great interest to the environmental and atmospheric chemistry community are presented. In particular, nearambient pressure XPS and NEXAFS, coupled to a UV-laser setup, were used to study the adsorption of water on a TiO 2 powder sample. The results are in line with previously proposed adsorption models of water on TiO 2 , and, furthermore, indicate that the concentration of water molecules tends to increase upon UV irradiation. In a second example we illustrate how NEXAFS spectroscopy measurements at the chlorine K-edge can provide new insight on the structures of eutectic and sub-eutectic frozen NaCl solutions at high and low relative humidity, respectively, indicating the formation of solution and solid NaCl phases, respectively. Finally, we demonstrate the assets of this new chamber for the dosing of sticky acidic gases and, in particular, for the investigation of formic acid uptake on ice surfaces.Keywords Metal oxides Á Ice Á Halogens Á X-ray photoelectron spectroscopy (XPS) Á Near-edge X-ray absorption fine structure (NEXAFS) Á Near ambient pressure photoemission (NAPP)

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Section: Phase Changes Of Nacl-water Binary Systemsmentioning

confidence: 69%

The Environmental Photochemistry of Oxide Surfaces and the Nature of Frozen Salt Solutions: A New in Situ XPS Approach

et al. 2016

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“…28, 49, and 50, see detailed discussion in Ickes et al 1 This relationship was originally derived for describing homogeneous nucleation of various metals from their melts, but it was shown to also work for alkali halides. 51 More recently, in a computational study of water and ice confined in nanopores, the Turnbull correlation was found to be consistent also in the supercooled range of water, revealing the same temperature dependence of σ i,l (T) and ∆H m (T), i.e., σ i,l (T)/∆H m (T) ≈ const. 52 The more alike the liquid and solid phases are, the smaller the enthalpy of the phase change and the smaller the interfacial energy.…”

Section: Interfacial Energymentioning

confidence: 83%

A physically constrained classical description of the homogeneous nucleation of ice in water

Koop

Murray

2016

The Journal of Chemical Physics

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101

152

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Liquid water can persist in a supercooled state to below 238 K in the Earth's atmosphere, a temperature range where homogeneous nucleation becomes increasingly probable. However, the rate of homogeneous ice nucleation in supercooled water is poorly constrained, in part, because supercooled water eludes experimental scrutiny in the region of the homogeneous nucleation regime where it can exist only fleetingly. Here we present a new parameterization of the rate of homogeneous ice nucleation based on classical nucleation theory. In our approach, we constrain the key terms in classical theory, i.e., the diffusion activation energy and the ice-liquid interfacial energy, with physically consistent parameterizations of the pertinent quantities. The diffusion activation energy is related to the translational self-diffusion coefficient of water for which we assess a range of descriptions and conclude that the most physically consistent fit is provided by a power law. The other key term is the interfacial energy between the ice embryo and supercooled water whose temperature dependence we constrain using the Turnbull correlation, which relates the interfacial energy to the difference in enthalpy between the solid and liquid phases. The only adjustable parameter in our model is the absolute value of the interfacial energy at one reference temperature. That value is determined by fitting this classical model to a selection of laboratory homogeneous ice nucleation data sets between 233.6 K and 238.5 K. On extrapolation to temperatures below 233 K, into a range not accessible to standard techniques, we predict that the homogeneous nucleation rate peaks between about 227 and 231 K at a maximum nucleation rate many orders of magnitude lower than previous parameterizations suggest. This extrapolation to temperatures below 233 K is consistent with the most recent measurement of the ice nucleation rate in micrometer-sized droplets at temperatures of 227-232 K on very short time scales using an X-ray laser technique. In summary, we present a new physically constrained parameterization for homogeneous ice nucleation which is consistent with the latest literature nucleation data and our physical understanding of the properties of supercooled water. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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“…However, recent work on nanoparticle phase suggests that these small particles should have a liquid phase (Cheng et al, 2015). Supersaturated AS nanoparticles, such as those likely to be produced in new particle formation, are expected to be liquid or mixed phase (depending on particle size) at the temperature and sizes considered in these experiments (see Sect.…”

Section: Particle-phase Dimethylaminium-ammonium Ratiosmentioning

confidence: 99%

“…Recent results have shown that the phase state of nanoparticles is size dependent, such that particles are expected to be completely liquid below some size threshold, even for supersaturated droplets (Cheng et al, 2015). The location of this transition depends on particle size, composition, water content, and temperature, and it was demonstrated to occur for AS nanoparticles at around 10 nm at 298 K for a particulate AS mass fraction of 0.63 (Cheng et al, 2015). At the slightly lower temperature in the present study (273 K), this transition occurs at a slightly smaller particle diameter, closer to 9 nm.…”

Section: Particle-phase Base : Acid Ratiosmentioning

confidence: 99%

Unexpectedly acidic nanoparticles formed in dimethylamine–ammonia–sulfuric-acid nucleation experiments at CLOUD

et al. 2016

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Abstract. New particle formation driven by acid-base chemistry was initiated in the CLOUD chamber at CERN by introducing atmospherically relevant levels of gas-phase sulfuric acid and dimethylamine (DMA). Ammonia was also present in the chamber as a gas-phase contaminant from earlier experiments. The composition of particles with volume median diameters (VMDs) as small as 10 nm was measured by the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Particulate ammonium-to-dimethylaminium ratios were higher than the gas-phase ammonia-to-DMA ratios, suggesting preferential uptake of ammonia over DMA for the collected 10-30 nm VMD particles. This behavior is not consistent with present nanoparticle physicochemical models, which predict a higher dimethylaminium fraction when NH 3 and DMA are present at similar gas-phase concentrations. Despite the presence in the gas phase of at least 100 times higher base concentrations than sulfuric acid, the recently formed particles always had measured base : acid ratios lower than 1 : 1. The lowest base fractions were found in particles below 15 nm VMD, with a strong size-dependent composition gradient. The reasons for the very acidic composition remain uncertain, but a plausible explanation is thatPublished by Copernicus Publications on behalf of the European Geosciences Union. 13602 M. J. Lawler et al.: Acidic nanoparticles at CLOUD the particles did not reach thermodynamic equilibrium with respect to the bases due to rapid heterogeneous conversion of SO 2 to sulfate. These results indicate that sulfuric acid does not require stabilization by ammonium or dimethylaminium as acid-base pairs in particles as small as 10 nm.

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Size dependence of phase transitions in aerosol nanoparticles

Cited by 160 publications

References 47 publications

The Environmental Photochemistry of Oxide Surfaces and the Nature of Frozen Salt Solutions: A New in Situ XPS Approach

The Environmental Photochemistry of Oxide Surfaces and the Nature of Frozen Salt Solutions: A New in Situ XPS Approach

A physically constrained classical description of the homogeneous nucleation of ice in water

Unexpectedly acidic nanoparticles formed in dimethylamine–ammonia–sulfuric-acid nucleation experiments at CLOUD

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