Visualization of Freezing Process in situ upon Cooling and Warming of Aqueous Solutions

Bogdan, Anatoli; Molina, Mario J.; Tenhu, Heikki; Bertel, E.; Bogdan, Nataliia; Loerting, Thomas

doi:10.1038/srep07414

Cited by 38 publications

(82 citation statements)

References 47 publications

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“…The appearance of these two glass transitions is similar to the appearance of the two glass transitions that we observed in the cooling/warming thermograms of aqueous citric acid and sucrose. 13,14 We reported that these two glass transitions are produced by the two freeze-concentrated solutions, FCS 1 and FCS 2 , of different concentrations. 13,14 Most likely, in our case, the two transitions of ∼30 wt % (CA + protein) can also be produced by two FCS 1 and FCS 2 , of different concentrations.…”

Section: Methodsmentioning

confidence: 98%

Physical Chemistry of the Freezing Process of Atmospheric Aqueous Drops

Bogdan

Molina

2017

J. Phys. Chem. A

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In supercooled aqueous solutions, ice nucleation is the initial stage of the freezing process. In this paper, we present experimental results that indicate that during the freezing of aqueous solutions, freeze-induced phase separation (FIPS) into pure ice and a freeze-concentrated solution (FCS) takes place. Our observations involve the use of an optical cryo-microscope (OC-M) to record images and movies. The results visually indicate for the first time that there are two freezing processes for (NH)H(SO)/HO solutions: (i) contact freezing, as is the case for pure water drops, and (ii) the Wegener-Bergeron-Findeisen process, which is the growth of frozen drops (ice) at the expense of liquid ones. We also present OC-M images of frozen micrometer-scaled HSO/HO drops that support our previous finding that freezing of these solutions generates mixed-phase particles, namely an ice core coated with a FCS. These results are relevant for atmospheric as well as for pharmaceutical sciences.

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Section: Methodsmentioning

confidence: 98%

Physical Chemistry of the Freezing Process of Atmospheric Aqueous Drops

Bogdan

Molina

2017

J. Phys. Chem. A

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“…In contrast, the dynamics of freezing forces the solutes to segregate and form the veins of freeze-concentrated solutions engulfed by the ice (Blackford, 2007;Cheng et al, 2010;McCarthy et al, 2013;Bogdan et al, 2014;Krausko et al, 2014). The solutes in the freeze-concentrated solution, here probably in the surface layer only, experience not only an increased concentration (Heger et al, 2005;Kania et al, 2014;Krausko et al, 2015a) but also a changed pH (Heger et al, 2006;Krausková et al, 2016;Papadimitriou et al, 2016;Rérolle et al, 2016) and polarity (Heger and Klan, 2007).…”

Section: Ffs At a High Temperature: Brine Fingers Formationmentioning

confidence: 99%

Evaporating brine from frost flowers with electron microscopy and implications for atmospheric chemistry and sea-salt aerosol formation

Yang

Neděla²,

Runštuk³

et al. 2017

Atmos. Chem. Phys.

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Abstract. An environmental scanning electron microscope (ESEM) was used for the first time to obtain well-resolved images, in both temporal and spatial dimensions, of labprepared frost flowers (FFs) under evaporation within the chamber temperature range from −5 to −18 • C and pressures above 500 Pa. Our scanning shows temperature-dependent NaCl speciation: the brine covering the ice was observed at all conditions, whereas the NaCl crystals were formed at temperatures below −10 • C as the brine oversaturation was achieved. Finger-like ice structures covered by the brine, with a diameter of several micrometres and length of tens to 100 µm, are exposed to the ambient air. The brine-covered fingers are highly flexible and cohesive. The exposure of the liquid brine on the micrometric fingers indicates a significant increase in the brine surface area compared to that of the flat ice surface at high temperatures; the NaCl crystals formed can become sites of heterogeneous reactivity at lower temperatures. There is no evidence that, without external forces, salty FFs could automatically fall apart to create a number of sub-particles at the scale of micrometres as the exposed brine fingers seem cohesive and hard to break in the middle. The fingers tend to combine together to form large spheres and then join back to the mother body, eventually forming a large chunk of salt after complete dehydration. The present microscopic observation rationalizes several previously unexplained observations, namely, that FFs are not a direct source of sea-salt aerosols and that saline ice crystals under evaporation could accelerate the heterogeneous reactions of bromine liberation.

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“…CA/H 2 O/oil-surfactant-matrix of 1/10 by volume were subjected to magnetic stirring at different speeds in order to obtain CA/H 2 O drops of different size distributions [1]. In our measurements, we used methodology based on a ´2-dimensionál´ solution strategy designed for the in-situ observation of FIPS and ice/FCS morphology by applying OC-M [2], [3].…”

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

Visualization data on the freezing process of micrometer-scaled aqueous citric acid drops

2017

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The visualization data (8 movies) presented in this article are related to the research article entitled “Freezing and glass transitions upon cooling and warming and ice/freeze-concentration-solution morphology of emulsified aqueous citric acid” (A. Bogdan, M.J. Molina, H. Tenhu, 2016) [1]. The movies recorded in-situ with optical cryo-miscroscopy (OC-M) demonstrate for the first time freezing processes that occur during the cooling and subsequent warming of emulsified micrometer-scaled aqueous citric acid (CA) drops. The movies are made publicly available to enable critical or extended analyzes.

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Visualization of Freezing Process in situ upon Cooling and Warming of Aqueous Solutions

Cited by 38 publications

References 47 publications

Physical Chemistry of the Freezing Process of Atmospheric Aqueous Drops

Physical Chemistry of the Freezing Process of Atmospheric Aqueous Drops

Evaporating brine from frost flowers with electron microscopy and implications for atmospheric chemistry and sea-salt aerosol formation

Visualization data on the freezing process of micrometer-scaled aqueous citric acid drops

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