Supersaturated Aqueous Solutions Research Articles

Bubbles nucleating on superhydrophobic micropillar arrays under flow.

When a supersaturated aqueous solution flows over a microstructured, hydrophobic surface, bubbles tend to nucleate. Here, we control heterogeneous nucleation of gas bubbles from supersaturated CO2 solution. By designing the shape, size, and arrangement of hydrophobic micropillars and by adjusting the flow we obtain uniform nucleation patterns. It is possible to selectively turn nucleation on and off. We use laser scanning confocal microscopy to resolve nucleation in early stages at the micropillar-substrate intersection. Numerical simulations show a correlation between minute pressure drops behind micropillars and nucleation sites. Bubbles nucleate uniformly behind pillars of the same size. The flow profile further contributes to the uniform growth of the bubbles. We control heterogeneous nucleation by varying micropillar geometry or size, flow direction and rate. While nucleation behind square pillars is independent of the flow direction, nucleation behind round micropillars is coupled with the direction. Nucleation behind triangular micropillars is bifurcated. These observations pave the way for the replenishment of the gas layer entrapped in between hydrophobic surface features, needed for superhydrophobicity.

Molecular Drivers of Crystallization Kinetics for Drugs in Supersaturated Aqueous Solutions

In this study, we explore molecular properties of importance in solution-mediated crystallization occurring in supersaturated aqueous drug solutions. Furthermore, we contrast the identified molecular properties with those of importance for crystallization occurring in the solid state. A literature data set of 54 structurally diverse compounds, for which crystallization kinetics from supersaturated aqueous solutions and in melt-quenched solids were reported, was used to identify molecular drivers for crystallization kinetics observed in solution and contrast these to those observed for solids. The compounds were divided into fast, moderate, and slow crystallizers, and in silico classification was developed using a molecular K-nearest neighbor model. The topological equivalent of Grav3 (related to molecular size and shape) was identified as the most important molecular descriptor for solution crystallization kinetics; the larger this descriptor, the slower the crystallization. Two electrotopological descriptors (the atom-type E-state index for -Caa groups and the sum of absolute values of pi Fukui(+) indices on C) were found to separate the moderate and slow crystallizers in the solution. The larger these descriptors, the slower the crystallization. With these 3 descriptors, the computational model correctly sorted the crystallization tendencies from solutions with an overall classification accuracy of 77% (test set).

Influence of cobalt-doping on the optical properties of zinc tris–thiourea sulfate (ZTS) single crystal

Zinc tris-thiourea sulfate (ZTS) single crystals, pure and doped with different concentrations of cobalt, were synthesized and grown by the slow evaporation technique of supersaturated aqueous solutions at 315 K. Co2+ concentration in the solution was 2, 4 and 6 mol%. Optical transmittance was measured for the obtained crystals as a function of wavelength in the range of 190–900 nm. The present investigation shows that doping ZTS crystal with Co2+ modifies its optical properties. The absorption coefficient of ZTS crystal exhibits an exponential dependence on photon energy following Urbach relation. Doping ZTS crystal with Co2+ changes the values of optical transmittance, cut off wavelength, absorption coefficient, optical energy gap, Urbach tail energy and steepness parameter. The changes are systematic i.e. the mentioned optical parameters increase or decrease continuously with increasing Co2+ concentration in the growth solution. The electrical conduction of ZTS crystal is increased with cobalt doping. The Urbach tail energy changes reversely with the optical energy gap.

A new insight into the mechanism of the scale inhibition: DLS study of gypsum nucleation in presence of phosphonates using nanosilver dispersion as an internal light scattering intensity reference

Scaling in reverse osmosis facilities, boilers, heat exchangers, evaporation plants, and oilfield applications is a serious problem worldwide. A widely used solution for controlling scale deposition is an application of chemical inhibitors. However, irrespective of the broad and a long-term antiscalant application, the mechanisms of scale inhibition are still the matter of discussions.In order to provide a new insight into the mechanism of the scale inhibition, a novel dynamic light scattering (DLS) special technique is used to study the bulk supersaturated gypsum aqueous solutions during the induction period. It is based on the standard Ag nanoparticles (ARGOVIT) injection into the supersaturated gypsum solution. These nanoparticles act as an internal indifferent light scattering intensity reference, and provide a semiquantitative measurement of a relative gypsum particles content in a blank solution and in the system treated with phosphonates: amino-tris(methylenephosphonic acid), ATMP; 1-hydroxyethane-1,1-bis(phosphonic acid), HEDP; 2-phosphonobutane-1,2,4-tricarboxylic acid, PBTC. It is found that ATMP sufficiently reduces the number of gypsum nuclei, spontaneously formed in the supersaturated solutions. The less effective inhibitors of gypsum scaling HEDP and PBTC also reduce the gypsum nuclei number, but to a less extent. A tentative nonconventional mechanism of scale inhibition in the bulk supersaturated aqueous solutions of gypsum is proposed.

Identification of molecular-interaction sites between lowly hydrolyzed polyvinyl alcohols and indomethacin by NMR spectroscopy

To evaluate the potency of hydrolyzed polyvinyl alcohols (PVAs) as matrices for solid dispersion (SD) formulations, we examined their inhibitory effects on precipitation of a poorly water-soluble drug, indomethacin (IND). Additionally, to clarify their mechanism, we investigated the intermolecular interaction of IND with PVAs in the supersaturated aqueous solution of IND. In the present study, we used five kinds of PVAs, i.e. JR-05 (70.0–74.0% hydrolyzed), JL-05E (80.0–84.0% hydrolyzed), JP-05 (87.0–89.0% hydrolyzed), JT-05 (93.5–94.5% hydrolyzed) and JF-05 (98.0–99.0% hydrolyzed). Of various PVAs, the lowly hydrolyzed PVAs such as JR-05 and JL-05E dramatically inhibited the precipitate formation of IND. Interestingly, the lowly hydrolyzed PVAs possessed micelle-forming ability, and inhibited the nucleation and crystal growth of IND. Moreover, strong hydrophobic interactions between vinyl acetate unit of lowly hydrolyzed PVA and hydrophobic moiety of IND were suggested based on the results of nuclear magnetic resonance (1H NMR) and nuclear overhauser effect spectroscopy (NOESY) in deuterium oxide. To the best of our knowledge, this is the first report describing the inhibitory effects of the hydrolyzed degree of PVAs on the precipitation of a drug, and demonstrating the intermolecular interaction between PVAs and a drug using NOESY in water.

Frustration vs Prenucleation: Understanding the Surprising Stability of Supersaturated Sodium Thiosulfate Solutions.

Gibbs classical nucleation theory predicts that a supersaturated solution will have transient nuclei that flitter in and out of existence. Only when one of these nuclei becomes larger than a critical size, will the solution crystalize. Recently, nonclassical nucleation theories have invoked the presence of prenuclei possibly associated with a liquid-liquid phase separation. However, there are few experimental observations of such prenuclei. Here, we use ultrafast optical Kerr-effect spectroscopy to measure the temperature-dependent low-frequency (sub-gigahertz to terahertz) anisotropic Raman spectra of supersaturated aqueous sodium thiosulfate solutions. Clear evidence of clusters is obtained in the spectra. However, on the basis of the inferred stability of these clusters, it appears that they frustrate rather than promote the formation of crystals. This would explain the surprising stability of supersaturated sodium thiosulfate and similar solutions.

NaCl nucleation from brine in seeded simulations: Sources of uncertainty in rate estimates.

This work reexamines seeded simulation results for NaCl nucleation from a supersaturated aqueous solution at 298.15 K and 1 bar pressure. We present a linear regression approach for analyzing seeded simulation data that provides both nucleation rates and uncertainty estimates. Our results show that rates obtained from seeded simulations rely critically on a precise driving force for the model system. The driving force vs. solute concentration curve need not exactly reproduce that of the real system, but it should accurately describe the thermodynamic properties of the model system. We also show that rate estimates depend strongly on the nucleus size metric. We show that the rate estimates systematically increase as more stringent local order parameters are used to count members of a cluster and provide tentative suggestions for appropriate clustering criteria.

Environmentally safe oil-field reagents for development and operation of oil-gas deposits

Sodium-carboxymethylcellulose and arabinogalactane inhibits the crystallization of calcium carbonate from a supersaturated aqueous solution at 80°C. The sizes of formed crystals CaCO3 in the presence of arabinogalactane, sodium-carboxymethylcellulose and neonol AF 9-10 decrease on an average 7-12 μm and a change of their structure. It is expected, that the mechanism of inhibitionis in specific adsorption polysaccharides and neonol on occurring crystalline surface of the calcium carbonate, both at the expense of electrostatic interaction of functional groups with Ca2+ ions, located on the surface of the crystal, and due to coordination and hydrogen bonds with oxygen atoms and HO-groups of additives. Oil-water emulsion rheology in the presence of neonol AF 9-10 has been studied. It is shown that neonol AF 9-10 decrease viscosity natural water-oil emulsion by 25 times. Addition of 5% neonol to water-oil emulsion leads to formation more than 20 stable emulsion forms of different density and composition. New highly effective “green” oilfield reagents have been developed on the basis of neonol and natural polysaccharides.

Kinetics of crystal growth of glycine manganese chloride in aqueous supersaturated solutions

In the present work, by using atomic force microscopy (AFM), the existence of periodic steps facilitates an aligned layer-over-layer (LOL) growth has been investigated for glycine manganese chloride (GMC) crystal. Nucleation and growth kinetics renders the information about the crystal growth process, which can be adopted to grow large size crystals. As for the crucial parameters in growing bulk crystal of GMC, the interfacial energy and growth activation energy have been calculated simultaneously from the induction time data without knowledge of the real growth rate of small nuclei. Additionally, various nucleation parameters involved in nucleation kinetics have been computed and described them as a function of temperature, degree of supersaturation. The results indicate that the growth activation energy for GMC is 13.34 kJ/mol, which suggests that the growth rate of small nuclei in the agitated induction time experiments is diffusion controlled.

Effects of Additives on the Morphology of Thiamine Nitrate: The Great Difference of Two Kinds of Similar Additives

The growth of thiamine nitrate, in supersaturated aqueous solutions in the absence and presence of sodium alkyl sulfates CH3(CH2)nSO4Na and sodium alkyl sulfonates CH3(CH2)nSO3Na was studied by a single seed crystal growth experiment. It was surprisingly found that the growth of the a-axis of thiamine nitrate is significantly inhibited by CH3(CH2)nSO4Na, thus reducing the aspect ratio of thiamine nitrate, while the aspect ratio of thiamine nitrate in the presence of CH3(CH2)nSO3Na remains almost constant. Furthermore, the mechanism of additives to modify the crystal morphology is proposed: both additives can inhibit the growth of thiamine nitrate by hindering the solute diffusion. However, their unusual behavior is due to the selective adsorption, which was caused by electrostatic and hydrogen bond interactions between solute and additive molecules. In particular, the anionic groups exposed at the end of the additives demonstrate an interesting case in which a small variation in the charge density and hyd...

STABILITY OF SUPERCOOLING SOLUTIONS OF CRYSTALLIZATION SYSTEMS IN CLASSICAL THEORY OF NEW PHASE FORMATION

Theoretical and experimental evaluations of crystallization systems solutions stability to overcooling were summarized. The general regulariries of the kinetics of the crystallization process are discussed from the standpoint of the classical theory of the formation and growth of new-phase particles. During the analysis of the process of periodic homogeneous crystallization kinetic diagram, three characteristic periods were revealed: the period of resistance to supercooling, the period of crystal growth, and the period of recrystallization. The nature of the processes determining the duration of the characteristic periods has been established. The applicability of the mathematical apparatus of the new phase formation classical theory for calculating the basic and particular functionals of the crystallization system is substantiated. Relations are given that make it possible to calculate the main and particular functionals of the crystallization system stability for supercooling. The analysis of crystallization system category influence on the magnitude of limit supercooling and periodic homogenous crystallization induction period extreme was made. Parameters of the resistance to supercooling of supersaturated aqueous solutions of inorganic and organic substances certain classes under periodic homogeneous crystallization are presented. Conclusions are drawn regarding the position of the main and particular functionals extrema of the crystallization system. The correctness of the conclusions is confirmed by an analysis of the experimental data on the crystallization kinetics of a number of inorganic and organic substances from aqueous and aqueous-organic solvents. On the example of periodic homogeneous crystallization process of the vitamin B1 thiamin bromide from the water-ethanol solution, a complete series of the crystallization system main and particular functionals extremum positions the are constructed. The regularities of the influence of the organic component concentration in a binary solvent on the stability functionals of the crystallization system are noted.Forcitation:Slivchenko E.S., Samarskiy A.P., Isaev V.N., Blinichev V.N. Stability of supercooling solutions of crystallization systems in classical theory of new phase formation. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 5. P. 88-93.

Dispersion of hydroxyapatite nanocrystals stabilized by polymeric molecules bearing carboxy and sulfo groups

Calcium phosphate buildup is important for biological processes (e.g., bones and teeth growth) and negatively affects the efficiency and functioning of water systems (e.g., cooling water systems and boilers) as a result of scale buildup by salts precipitation. Thus, stable aqueous dispersions of calcium phosphate particles can effectively prevent the formation and buildup of scale in water systems. In this study, the stabilization of calcium phosphate nanocrystals (NCs) was studied by forming a supersaturated solution in the presence of poly acrylic acid/2-acrylamide-2-methylpropane sulfonic acid p(AA/AMPS) containing carboxy and sulfo group functionalities. Calcium phosphate NCs were formed and subsequently aggregated in a supersaturated aqueous solution containing 2-phosphonobutane-1,2,4-tricarboxylic acid without any copolymers. Aggregation of calcium phosphate NCs was suppressed in the presence of polymeric molecules containing carboxy groups, whereas molecules bearing sulfo groups were ineffective in dispersing calcium phosphate NCs. However, copolymers bearing both functional groups enhanced the dispersibility of calcium phosphate NCs. Using a combination of light scattering and surface charge measurements along with electron imaging, we found that the inhibition of calcium phosphate precipitation originates from hydroxyapatite nanocrystals (HANCs) with a size smaller than 100 nm in solution. While the carboxy groups in the copolymer adsorbed on the surface of the HANCs, the sulfo groups provided these species with an overall negative surface charge, thereby increasing their colloidal stability via electrostatic repulsion. These results indicated that the aggregation of the HANCs can be effectively hindered using sulfo/carboxy bifunctional copolymers.

Impact of Bile Salts on Solution Crystal Growth Rate and Residual Supersaturation of an Active Pharmaceutical Ingredient

Supersaturating formulations have become a popular approach to address the issue of inadequate aqueous solubility for small molecules. Given that prevention of nucleation may not be always possible, it is of particular interest to control crystal growth from supersaturated solutions in order to maximize the extent of oral absorption of therapeutic agents. Bile salts are endogenous surfactants that are present in biorelevant dissolution media and can have direct impact on the in vivo performance of therapeutic agents due to their presence in the gastrointestinal tract. In this study, an in situ common history seeding method was implemented to provide seeds that better mimic crystals formed from aqueous supersaturated solutions. By forming seeds in situ and then regenerating supersaturation, we were able to probe the influence of biorelevant bile salts on telaprevir crystal growth rates and secondary nucleation. The extent of growth inhibition was found to vary with bile salt chemistry and aggregation level...

A research on the chemical and microbiological qualities of honeys sold in Istanbul

Abstract Honey, produced by honeybees from nectar in flowers and plants, is an aqueous supersaturated sugar solution, mainly composed of fructose and glucose. The quality and biochemical properties of honey are related to honey maturity, production methods, processing and storage conditions, climatic conditions as well as the nectar source of the honey. In this study, 35 honey samples of different sizes and packaging all of which were sold in Istanbul were examined in terms of some physicochemical and microbiological properties. All samples were floral liquid honey. The physicochemical characterizations were as follows: average moisture (16.31±1.40%), ash (0.30±0.29%), hydroxymethylfurfural (HMF) (8.09±7.63 mg/kg), pH (4.32±0.34), acidity (30±9 meq/kg). In addition, total mesophilic aerobic bacteria, Enterobacteriaceae, yeast and mold analyses were performed in these samples. According to the microbiological analyses; the average total number of mesophilic aerobic bacteria was 2.68 log cfu/g. Enterobacteriaceae have not been observed in the samples. However, in three samples, mold-yeasts were detected at the levels between 1.30 and 1.60 log cfu/g.

Supersaturation dependence of glycine polymorphism using laser-induced nucleation, sonocrystallization and nucleation by mechanical shock.

The nucleation of glycine from aqueous supersaturated solution has been studied using non-photochemical laser-induced nucleation (NPLIN), ultrasound (sonocrystallization), and mechanical shock of sample vials. It was found that at higher supersaturation, samples were more susceptible to nucleation and produced more of the γ-glycine polymorph. The results are described in terms of a mechanism common to all three nucleation methods, involving the induction of cavitation events and pressure shockwaves. The switch in preference from α- to γ-glycine was observed to occur over a narrower range of supersaturation values for NPLIN. We attribute this to induction of cavitation events with higher energies, which result in higher localized pressures and supersaturations. Experiments on NPLIN using circularly versus linearly polarized light showed no evidence for binary polarization switching control of glycine polymorphism.

Polarization independence of laser-induced nucleation in supersaturated aqueous urea solutions.

In a seminal report on laser-induced nucleation in aqueous supersaturated solutions (Phys. Rev. Lett., 1996, 77, 3475) it was noted that needle-shaped crystals of urea were aligned with the direction of the electric field of the linearly polarized laser pulse. The results gave rise to a new mechanism for control of crystal nucleation involving alignment of solute molecules (optical Kerr effect) now commonly known as non-photochemical laser-induced nucleation (NPLIN). Recent theoretical and experimental work has cast doubts on the optical Kerr effect mechanism. In the present letter we present results from digital imaging of urea-crystal growth immediately following laser-induced nucleation. Analysis of the data shows no statistically significant correlation between crystal angle and direction of linear polarization. The results overturn a long-held result that has shaped theoretical and experimental studies of NPLIN.

On the light intensity transmitted through water and aqueous supersaturated ammonium dihydrogen phosphate solutions containing different antisolvents

Experimental data of the dependence of transmitted laser light intensity I of aqueous ADP solutions saturated at 303.15K on feeding time t of three antisolvents (i.e. acetone, methanol and ethanol) are analyzed using mathematical equations based on two approaches. The first approach is based on exponential decrease in I with increasing t whereas the second one is based on the concept of adsorption of antisolvent molecules onto solvent and solute molecules. It was found that: (1) the latter approach is superior to the former one for explaining the observed dependence of transmitted laser-beam intensities of pure solvent and aqueous saturated ADP solutions, (2) the parameter A of the second approach provides better insight into the processes of adsorption of antisolvents in terms of the differential heat Qdiff of adsorption, and (3) the trends of changes in the values Qdiff for different antisolvents in water and aqueous solutions are associated with the dielectric constants of different antisolvents and are directly connected with the chemical constitution of the methanol, ethanol and acetone molecules.

Effects of pulsed electric energy on sucrose nucleation in supersaturated solutions

The effects of pulsed electric energy (PEE) on sucrose nucleation in supersaturated aqueous solutions are studied. The supersaturation degree (S = 1.32) and temperature (T = 25 °C) were fixed. Pulsed electric field (PEF) treatment without discharge was performed in the chamber with plane-to-plane electrodes geometry using exponential pulses and electric field strength of E = 20–80 kV/cm. High voltage electrical discharge (HVED) treatment was applied in the chamber with rod-to-plane electrodes geometry at E = 20–80 kV/cm. Different number of PEE pulses was applied, n = 1–20. An insignificant reduction of the induction period of nucleation was observed for the PEF treated sample (n = 10), tind ≈ 100 min. However, after the HVED treatment (n = 10) the induction period was only tind ≈ 55 min. For the HVED assisted nucleation, the time of effective crystallization decreased and a maximum rate of crystallization increased with increasing of E and n. The obtained data evidence promising perspectives for enhancing sucrose crystallization by the HVED treatment.

Effect of sodium-carboxymethylcellulose on inhibition of scaling by calcium carbonate and sulfate

Sodium-carboxymethylcellulose inhibits the crystallization of calcium carbonate and sulfate on the surface of stainless steel in a supersaturated aqueous solution at 80°C. An increase in the size of calcium carbonate crystals and a change of their structure is observed in the presence of sodium-carboxymethylcellulose. The data obtained indicate that development of new “green” reagents for oil and gas extraction, scale inhibitors, on the basis of sodium-carboxymethylcellulose is promising.

A Comparison of the Crystallization Inhibition Properties of Bile Salts

Bile salts are natural surfactants present in the human gastrointestinal tract. Therefore, it is essential to consider their effect on the dissolution and crystallization tendency of oral drug formulations. Although a recent study showed that sodium taurocholate delayed nucleation for 11 structurally diverse compounds, there is limited information about the crystallization inhibition properties of other bile salts and whether they are interchangeable in this context. In this study, we evaluated the ability of 13 bile salts to maintain supersaturated aqueous solutions of three compounds: celecoxib, nevirapine, and fibanserin. Most bile salts extended nucleation induction times. However, their inhibitory effects varied depending on the structure and concentration of the bile salt and the drug. The R5 group and hydrophobicity of the bile salt appeared to be essential. Molecular dynamics simulations indicated that van der Waals and hydrogen bonding interactions occurred between nevirapine and bile salts, with...