Role of surface properties for the kinetics of bubble Ostwald ripening in saponin-stabilized foams

Tcholakova, Slavka; Mustan, Fatmegul; Pagureva, Nevena; Golemanov, Konstantin; Denkov, Nikolai D.; Pelan, Eddie G.; Stoyanov, Simeon D.

doi:10.1016/j.colsurfa.2017.04.055

Cited by 52 publications

(36 citation statements)

References 40 publications

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“…This second peak is due to dissolution of the ESCA molecule in the water, followed by transfer to the second interface, as confirmed by visual inspection of the MD trajectory. This behavior outlines the anionic form of escin as being much more water-soluble, which is in agreement with the experimental results indicating that the anionic form of escin is more soluble than the neutral one [13].…”

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confidence: 91%

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Self-Assembly of Escin Molecules at the Air–Water Interface as Studied by Molecular Dynamics

2017

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Escin belongs to a large class of natural biosurfactants, called saponins, that are present in more than 500 plant species. Saponins are applied in the pharmaceutical, cosmetics, and food and beverage industries due to their variously expressed bioactivity and surface activity. In particular, escin adsorption layers at the air-water interface exhibit an unusually high surface elastic modulus (>1100 mN/m) and a high surface viscosity (ca. 130 N·s/m). The molecular origin of these unusual surface rheological properties is still unclear. We performed classical atomistic dynamics simulations of adsorbed neutral and ionized escin molecules to clarify their orientation and interactions on the water surface. The orientation and position of the escin molecules with respect to the interface, the intermolecular interactions, and the kinetics of molecular aggregation into surface clusters are characterized in detail. Significant differences in the behavior of the neutral and the charged escin molecules are observed. The neutral escin rapidly assembles in a compact and stable surface cluster. This process is explained by the action of long-range attraction between the hydrophobic aglycones, combined with intermediate dipole-dipole attraction and short-range hydrogen bonds between the sugar residues in escin molecules. The same interactions are expected to control the viscoelastic properties of escin adsorption layers.

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confidence: 91%

“…This compound is also a surfactant with some unusual adsorption characteristics. Escin adsorption layers feature extremely high surface elastic modulus and very low gas permittivity, which is important for the properties of foams and emulsions stabilized by this natural surfactant [12,13].…”

Section: Introductionmentioning

confidence: 99%

Self-Assembly of Escin Molecules at the Air–Water Interface as Studied by Molecular Dynamics

2017

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“…Despite this, surfactant foams tend to have a limited stability of only a few hours. Colloidal particles and certain proteins are extremely efficient in creating mechanically resistant surface layers to stop coalescence and coarsening all together (Gonzenbach et al, 2006;Salonen et al, 2016;Stocco et al, 2011;Tcholakova et al, 2008Tcholakova et al, , 2017. Particles can also gel or get stuck in the foam structure to block drainage (Bey et al, 2017;Guillermic et al, 2009;Haffner et al, 2014;Khidas et al, 2014;Louvet et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Surfactant Crystals as Stimulable Foam Stabilizers: Tuning Stability with Counterions

Zhang

Wang

Zheng

et al. 2019

J Surfact & Detergents

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The demands on foam stability are variable and changing, which is why design of foams that are both ultrastable and stimulable is important. We study foams stabilized using surfactant particles made through precipitation of sodium dodecyl sulfate with alkali chlorides. We have previously shown that depending on the concentrations of surfactant and salt, the foams can be ultrastable or age like common surfactant foams. We now show that the adsorption of surfactant crystals changes with the type of salt added and how the crystals are made, as well as the surfactant concentration. We see differences in foam stability if the crystals are made prior to foaming or if they are formed concomitantly with foaming. The adsorption of the crystals is improved if the crystals are made during generation, possibly because of their smaller size. The foams destabilize when heated above the Krafft boundary. We show that through tuning the surfactant concentration and salt type or concentration, we can modulate the melting temperature, and hence the destruction temperature of foam between 22 and 50 °C. Precipitated surfactant particles are versatile alternatives to stabilize ultrastable and stimulable foams.

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“…3 Procedure of single diamond eptaxial growth on Ir substrate [16,[60][61][62][63][64] 图 4 利用二次电子探测器观测到的 SEM 照片 [72] (a) BEN 过程后铱衬底表面形貌; (b) BEN 过程后铱衬底局部表面形貌; (c)生长过程后同一位置形貌 Fig. 4 SEM images [72] of the iridium surface after BEN treatment (a), local spots after BEN (b) and after a subsequent growth step (c) 程即新金刚石晶核与形核阶段金刚石晶核的连接与晶体尺寸增加过程。比较常见的晶体材料的生长机制有奥斯特瓦尔德熟化(Ostwald Ripening, OR) [73] 、定向附着生长 (Oriented Attachment, OA) [74] 和柯肯达尔效应 (Kirkendall Effect, KE) [75] 等。定向附着生长是团簇沿着特定的晶向聚集并最终形成单晶或孪晶的过程, 具有非随机性 [76] 。由于金刚石在 Ir 衬底上较高的形核密度, 金刚石生长的最初阶段更倾向于 OA 生长机制, 可以认为定向附着生长即为金刚石缓慢生长阶段的微观机理。 Li 等 [77] 首次利用透射电子显微镜观测到液体中晶粒的定向附着生长过程, 如图 5 所示。 Dong 等 [69] 在外延薄膜中观测到薄膜和过渡层晶粒的拓扑衍生定向附着生长现象, 如图 3(c1)所示。Dideikin 等 [78] 以爆轰法制备的纳米金刚石为原料, 在高温高压条件下, 纳米金刚石颗粒相接触并发生倾斜、旋转, 每两个颗粒的相同晶面通过悬挂键相连接, 最终形成 1.5 μm 的单晶金刚石颗粒, 从而验证了固体颗粒之间的定向附着生长机制。但是对于金刚石在形核生长过程中的原位过程还缺少相应的研究仪器和研究方法, 以至于金刚石的生长过程难以通过直观的方法进行观测。定向附着生长过程中, 晶界湮没形成金刚石单晶是小角度晶界形成的楔形向错所导致的。图 3(c2) 为立方晶中的小角晶界及部分形成楔形向错的结构示意图, 楔形向错对应于一个不完整的倾斜晶界 [70] 。可以推出晶粒尺寸 R 和晶界转变为楔形向错的临界角 ω crit 之间的关系为 [32] :…”

Section: 金刚石的生长过程unclassified

Heteroepitaxial Growth of Single Crystal Diamond Films on Iridium: Procedure and Mechanism

Zhu¹,

Zhong-Bo²,

Dai³

2019

Journal of Inorganic Materials

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Due to its unique physical and chemical property, diamond is widely used in many fields such as detectors and optoelectronic devices. Many scholars' attention is drew into single crystal diamond because of its potential to significantly increase the functionality of these devices. Presently, single crystal diamonds grown heteroepitaxially on iridium (Ir) substrates reach the largest size and an excellent growth quality. In this paper, substrates with different structures for nucleation and growth processes of epitaxial diamond are introduced. The mechanisms of diamond nucleation by Bias Enhanced Nucleation (BEN) method and growth undergoing an Epitaxial Lateral Overgrowth (ELO) process are described, including technique of Patterned Nucleation and Growth(PNG). Limitations of current study are pointed out, and the future development of heteroepitaxial theory and experiment are also forecasted in this paper.

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Role of surface properties for the kinetics of bubble Ostwald ripening in saponin-stabilized foams

Cited by 52 publications

References 40 publications

Self-Assembly of Escin Molecules at the Air–Water Interface as Studied by Molecular Dynamics

Self-Assembly of Escin Molecules at the Air–Water Interface as Studied by Molecular Dynamics

Surfactant Crystals as Stimulable Foam Stabilizers: Tuning Stability with Counterions

Heteroepitaxial Growth of Single Crystal Diamond Films on Iridium: Procedure and Mechanism

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