Colloids and Interfaces

17 pages, 8176 KiB

Open AccessArticle

Effect of the Core/Shell Particle Synthesis Method on the Physico–Chemical Properties of Their Shell and Sensory Properties of 3D-Ordered Films

by Olga Iakobson, Elena Ivankova, Svetlana Laishevkina and Natalia Shevchenko

Colloids Interfaces 2024, 8(6), 67; https://doi.org/10.3390/colloids8060067 - 10 Dec 2024

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Abstract

In this work, we investigated the influence of the synthetic conditions of core/shell particles on physico–chemical properties of their shells, the process of self-assembly of particles into 3D-ordered structures, and the sensitivity of films based on these particles to the presence of ethanol [...] Read more.

In this work, we investigated the influence of the synthetic conditions of core/shell particles on physico–chemical properties of their shells, the process of self-assembly of particles into 3D-ordered structures, and the sensitivity of films based on these particles to the presence of ethanol and temperature changes. The core/shell particles were prepared by two methods: seed emulsion copolymerization and semi-batch emulsion copolymerization. The cores consisted of polystyrene or its copolymer with methyl methacrylate. Polymer shells of the particles were obtained by copolymerization of methyl methacrylate with several acrylate comonomers: butyl acrylate, butyl methacrylate, propyl acrylate, and ethyl acrylate. The photonic crystal films with the highest sensitivity to ethanol vapors were obtained on the basis of the core/shell particles synthesized by semi-batch emulsion polymerization. It was also established that introducing butyl acrylate or propyl acrylate units into shell copolymers led to an increase in the sensitivity of the resulting photonic crystal films. The films demonstrated a pronounced thermosensitivity only when the corresponding core/shell particles were synthesized as follows: the shell comonomers (methyl methacrylate and butyl acrylate) were introduced into the reaction system during the semi-batch emulsion process in a single step. The intensity of the photonic band gap (PBG) peak for these films decreased by 100% at around 42 °C. Full article

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17 pages, 2972 KiB

Open AccessFeature PaperArticle

Foaming Properties of Chlorella sorokiniana Microalgal Biomass

by Despoina Georgiou, Aggelos Charisis, Athina Theocharidou, Christos Ritzoulis, Georgia Papapanagiotou, Christina Samara, Christos Chatzidoukas and Eleni P. Kalogianni

Colloids Interfaces 2024, 8(6), 66; https://doi.org/10.3390/colloids8060066 - 29 Nov 2024

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Abstract

Chlorella sorokiniana is a well-studied microalga with significant nutritional potential due to its health-promoting nutrients. C. sorokiniana is rich in proteins (~50%), lipids (~14%), vitamins, and other bioactive compounds, making it an attractive ingredient for the food industry. Other properties of C. sorokiniana [...] Read more.

Chlorella sorokiniana is a well-studied microalga with significant nutritional potential due to its health-promoting nutrients. C. sorokiniana is rich in proteins (~50%), lipids (~14%), vitamins, and other bioactive compounds, making it an attractive ingredient for the food industry. Other properties of C. sorokiniana, such as its foaming properties, have not been extensively investigated. The present work examines the foaming properties of C. sorokiniana biomass and of its fractions, namely the foaming properties of the whole-cell biomass, the disrupted-cell biomass, the water-soluble protein-rich extract, and the disrupted-cell biomass residue after oil extraction. The water/air interfacial tension, zeta potential, foaming capacity, foam stability, and foam morphology of C. sorokiniana biomass and its fractions were determined. Furthermore, the effect of the pH on the foaming properties of the water-soluble protein-rich extract was also investigated. The results show that the examined fractions decrease the water-air interfacial tension and form foams. The type of biomass fraction affects strongly the foam characteristics and foam stability. Furthermore, the stability and characteristics of the foam are significantly affected by pH. Overall, the water-soluble protein-rich extract at pH 7 presented the best foam stability, as the foam remained stable for more than 24 h and had a narrow bubble size distribution. The obtained results suggest that fractionated microalgae biomass could be used as an effective foaming agent in different commercial applications. Full article

(This article belongs to the Special Issue Food Colloids: 3rd Edition)

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16 pages, 2729 KiB

Open AccessArticle

Polyelectrolyte-Surfactant Mixture Effects on Bulk Properties and Antibacterial, Cytotoxic Activity of Fine Sulfur Particles

by Seitzhan Turganbay, Saule Aidarova, Assem Issayeva, Zhanar Iskakbayeva, Aitugan Sabitov, Gulsinay Turganbay and Alpamys A. Babayev

Colloids Interfaces 2024, 8(6), 65; https://doi.org/10.3390/colloids8060065 - 28 Nov 2024

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Abstract

Elemental sulfur, commonly known for its wide range of biological activities, has a long history of use in protecting all garden and vegetable crops from a range of pests and diseases, including powdery mildew, ascochyta blight, clubroot, plant mites, oidium, anthracnose, and scab. [...] Read more.

Elemental sulfur, commonly known for its wide range of biological activities, has a long history of use in protecting all garden and vegetable crops from a range of pests and diseases, including powdery mildew, ascochyta blight, clubroot, plant mites, oidium, anthracnose, and scab. In the present study, a quick and environmentally friendly approach has been developed for the synthesis of sulfur nanoparticles with antibacterial activity. Fine sulfur particles (FSPs) were prepared by modifying the surface of elemental sulfur using various polyelectrolyte–surfactant mixtures (PSMs) including sodium carboxymethyl cellulose–sodium dodecylbenzene sulfonate (NaCMC-SDBS) and polyhexamethylene guanidine hydrochloride–cetyltrimethylammonium bromide (PHMG-CTAB). The FSPs were characterized by UV–visible spectrophotometry, X-ray diffraction (XRD), thermogravimetric/differential scanning calorimetry analysis (TG/DSC), and scanning electron microscopy (SEM), with the FSPs showing an almost spherical shape with an average size in the range of 150–200 nm. The antibacterial activity of the FSPs was tested against Gram-positive Staphylococcus aureus and Enterococcus faecium and Gram-negative Escherichia coli and Pseudomonas aeruginosa bacteria and one fungus (Aspergillus brasiliensis ATCC 95 16404). Based on this, it could be seen that FSPs exhibited significant antimicrobial activity against Gram-positive bacteria, i.e., S. aureus and E. faecium. The in vitro cytotoxicity of the FSPs-1 and FSPs-2 studied in normal (MeT-5A) and tumorous (MCF-7) human cell lines was assessed in the concentration range from 500 μg/mL to 0.12 mg/mL, from which it was determined as being non-cytotoxic. The received products can be considered for potential application in agriculture and medicine. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of Colloids and Interfaces 2024)

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13 pages, 2053 KiB

Open AccessFeature PaperArticle

Adsorption Behavior of Fluorocarbon Surfactants on Polytetrafluoroethylene Surface

by Fei Yan, Cheng Ma, Qingtao Gong, Wangjing Ma, Zhiqiang Jin, Zhicheng Xu, Lei Zhang and Lu Zhang

Colloids Interfaces 2024, 8(6), 64; https://doi.org/10.3390/colloids8060064 - 20 Nov 2024

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Abstract

By using the sessile drop method, the wetting properties of nonionic fluorocarbon surfactants (FNS-1 and FNS-2) and anionic fluorocarbon surfactant (FAS) solutions on the surface of polytetrafluoroethylene (PTFE) were investigated. Meanwhile, the effects of surfactant concentration on the contact angle, adhesion tension, PTFE–liquid [...] Read more.

By using the sessile drop method, the wetting properties of nonionic fluorocarbon surfactants (FNS-1 and FNS-2) and anionic fluorocarbon surfactant (FAS) solutions on the surface of polytetrafluoroethylene (PTFE) were investigated. Meanwhile, the effects of surfactant concentration on the contact angle, adhesion tension, PTFE–liquid interfacial tension, and work of adhesion of the fluorocarbon surfactant with different structures were detected. The results demonstrate that the adsorption amount of the three fluorocarbon surfactants at the air–liquid interface is 1.5~2 times higher than their adsorption amount at the PTFE–solution interface. Before critical micelle concentration (CMC), the fluorocarbon surfactant molecules rely on their hydrophobic groups to adsorb on the PTFE surface. The smallest molecular size of FNS-2 results in the largest adsorption amount, while electrostatic repulsion and large steric hindrance result in the smallest adsorption amount for FAS. Above CMC, the fluorocarbon surfactants form semi-micelles to adsorb on the PTFE surface. The hydrophilic modification ability of the three fluorocarbon surfactants for the PTFE surface is stronger than that of reported surfactants, and the contact angle can be reduced to about 20° at high concentrations. The order of the hydrophilic modification ability is FNS-2 > FNS-1 > FAS. Hydrophilic EO groups can effectively enhance the hydrophilicity of FNS-1 and FNS-2. Due to the hydrophobic -CH₃ group and the smaller adsorption amount, FNS-1 possesses a weaker hydrophilic modification ability than FNS-2. Investigating the adsorption behavior of fluorocarbon surfactants on the PTFE surface can help us to better utilize fluorocarbon surfactants. This could have broad implications for colloid and interface science. Full article

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18 pages, 8994 KiB

Open AccessArticle

A GNN-Based QSPR Model for Surfactant Properties

by Seokgyun Ham, Xin Wang, Hongwei Zhang, Brian Lattimer and Rui Qiao

Colloids Interfaces 2024, 8(6), 63; https://doi.org/10.3390/colloids8060063 - 19 Nov 2024

Viewed by 503

Abstract

Surfactants are among the most versatile molecules in the chemical industry because they can self-assemble in bulk solutions and at interfaces. Predicting the properties of surfactant solutions, such as their critical micelle concentration (CMC), limiting surface tension (

γ_{c m c}

), [...] Read more.

Surfactants are among the most versatile molecules in the chemical industry because they can self-assemble in bulk solutions and at interfaces. Predicting the properties of surfactant solutions, such as their critical micelle concentration (CMC), limiting surface tension (

γ_{c m c}

), and maximal packing density (

Γ_{m a x}

) at water–air interfaces, is essential to their rational design. However, the relationship between surfactant structure and these properties is complex and difficult to predict theoretically. Here, we develop a graph neural network (GNN)-based quantitative structure–property relationship (QSPR) model to predict the CMC,

γ_{c m c}

, and

Γ_{m a x}

. Ninety-two surfactant data points, encompassing all types of surfactants—anionic, cationic, zwitterionic, and nonionic—are fed into the model, covering a temperature range of [20–30 °C], which contributes to its generalization across all surfactant types. We show that our models have high accuracy (R² = 0.87 on average in tests) in predicting the three parameters across all types of surfactants. The effectiveness of the QSPR model in capturing the variation of CMC,

γ_{c m c}

, and

Γ_{m a x}

with molecular design parameters are carefully assessed. The curated dataset, developed model, and critical assessment of the developed model will contribute to the development of improved surfactants QSPR models and facilitate their rational design for diverse applications. Full article

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36 pages, 4529 KiB

Open AccessFeature PaperReview

Addressing the Apparent Controversies Between the Contact Angle-Based Models for Estimation of Surface Free Energy: A Critical Review

by Georgi As. Georgiev, Stanislav Baluschev, Petar Eftimov, Mihaela Bacheva and Katharina Landfester

Colloids Interfaces 2024, 8(6), 62; https://doi.org/10.3390/colloids8060062 - 18 Nov 2024

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Abstract

The most popular contact angle (CA)-based approaches for determination of solid surface free energy (SFE) are considered: (i) single liquid methods, mainly of Neumann and Chibowski, (ii) the multiple liquids approach of Owens–Wendt–Rabel–Kaelble (OWRK), and (iii) van Oss-Chaudhury–Good (vOCG) acid–base model. Evaluations based [...] Read more.

The most popular contact angle (CA)-based approaches for determination of solid surface free energy (SFE) are considered: (i) single liquid methods, mainly of Neumann and Chibowski, (ii) the multiple liquids approach of Owens–Wendt–Rabel–Kaelble (OWRK), and (iii) van Oss-Chaudhury–Good (vOCG) acid–base model. Evaluations based on Neumann and Chibowski models agree between each other. Under the assumption of equilibrium “wet wetting” (i.e., presence of saturated precursor film ahead of the drop), the model of Chibowski transforms in Lipatov’s interfacial equilibrium rule, i.e., the Antonow rule derived for the ternary point solid–liquid–gas. Very good agreement is observed between single and multiple liquids models where OWRK/vOCG values can be viewed as a mean of the individual SFE adopted by the solid with each of the wetting probes. Both approaches (single and multiple liquids) can be used in conjunction to evaluate SFE dispersion and polar components and to elucidate hydrophobicity and hydrophilicity. The implementation of apparently fully non-polar liquids (diiodomethane, bromonaphthalene) in OWRK and vOCG is practically and theoretically suspect. CA-based estimates represent apparent SFE determined by the interactions of both the solid surface and the probing liquid, which are very useful to elucidate the energy, chemistry and dynamics of the solid surface. Full article

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13 pages, 3087 KiB

Open AccessArticle

Mixed Adsorption Mono- and Multilayers of ß-Lactoglobulin Fibrils and Sodium Polystyrene Sulfonate

by A. G. Bykov, G. Loglio, R. Miller, E. A. Tsyganov, Z. Wan and B. A. Noskov

Colloids Interfaces 2024, 8(6), 61; https://doi.org/10.3390/colloids8060061 - 11 Nov 2024

Viewed by 711

Abstract

The formation of beta-lactoglobulin (BLG)/sodium polystyrene sulfonate (PSS) complexes decelerates the change in the surface properties of the mixed solutions with the surface age and increases the steady-state dilational surface elasticity in a narrow PSS concentration range. At the same time, the changes [...] Read more.

The formation of beta-lactoglobulin (BLG)/sodium polystyrene sulfonate (PSS) complexes decelerates the change in the surface properties of the mixed solutions with the surface age and increases the steady-state dilational surface elasticity in a narrow PSS concentration range. At the same time, the changes in the surface properties are accelerated in the dispersions of BLG fibrils with and without PSS due to the influence of small peptides coexisting with fibrils. A decrease in the peptide concentration as a result of the dispersion purification leads to slower changes in the surface properties at low PSS concentrations. The increase in the polyelectrolyte concentration results in an increase in the steady-state surface elasticity due to the fibril/PSS complex formation and in very slow changes in the surface properties if the polyelectrolyte exceeds a certain critical value. The latter effect is a consequence of the formation of large aggregates and of an increase in the electrostatic adsorption barrier. The consecutive adsorption of BLG fibrils and PSS leads to the formation of regular multilayers at the liquid–gas interface. The multilayer properties change noticeably with an increase in the number of layers from four to six in agreement with previous results on the multilayers of PSS with an oppositely charged synthetic polyelectrolyte, presumably due to the heterogeneity of the first PSS layer. The dynamic elasticity of the multilayers approaches 250 mN/m, indicating that they can effectively stabilize foams and emulsions. Full article

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37 pages, 3487 KiB

Open AccessFeature PaperArticle

The Entropy of Mixing in Self-Assembly and the Role of Surface Tension in Modeling the Critical Micelle Concentration

by Frank Müh

Colloids Interfaces 2024, 8(6), 60; https://doi.org/10.3390/colloids8060060 - 31 Oct 2024

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Abstract

A theory for the micelle formation of nonionic head-tail amphiphiles (detergents) in aqueous solutions is derived based on the traditional molecular thermodynamic modeling approach and a variant of the Flory–Huggins theory that goes beyond lattice models. The theory is used to analyze experimental [...] Read more.

A theory for the micelle formation of nonionic head-tail amphiphiles (detergents) in aqueous solutions is derived based on the traditional molecular thermodynamic modeling approach and a variant of the Flory–Huggins theory that goes beyond lattice models. The theory is used to analyze experimental values for the critical micelle concentration of n-alkyl-ß-D-maltosides within a mass action model. To correlate those parts of the micellization free energy, which depend on the transfer of hydrophobic molecule parts into the aqueous phase, with molecular surfaces, known data for the solubility of alkanes in water are reanalyzed. The correct surface tension to be used in connection with the solvent-excluded surface of the alky tail is ~30 mN/m. This value is smaller than the measured surface tension of a macroscopic alkane–water interface, because the transfer free energy contains a contribution from the incorporation of the alkane or alkyl chain into water, representing the change in free volume in the aqueous phase. The Flory–Huggins theory works well, if one takes into account the difference in liberation free energy between micelles and monomers, which can be described in terms of the aggregation number as well as the thermal de Broglie wavelength and the free volume of the detergent monomer. Full article

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15 pages, 4012 KiB

Open AccessArticle

Exploring the Safety of the Sustainable Toxicity Testing in Zebrafish and Brine Shrimp Using Nanoemulsions Formulated from Fish Byproducts and Lemon Oil

by Amira Ayman Hendawy, Amal A. M. Elgharbawy, Najihah Mohd Noor, Nurhidayu Al-Saari, Nor Azrini Nadiha Azmi and Hamzah Mohd Salleh

Colloids Interfaces 2024, 8(6), 59; https://doi.org/10.3390/colloids8060059 - 29 Oct 2024

Viewed by 876

Abstract

Nanoemulsions, characterized by their nanosized particles ranging from 20 to 200 nm, are effective carriers for drug molecules. Our novel oil-in-water nanoemulsion, NE-FLO™, formulated from lemon and fish byproduct oils, demonstrates promising antioxidant and anti-inflammatory activities, with initial studies indicating nontoxicity to normal [...] Read more.

Nanoemulsions, characterized by their nanosized particles ranging from 20 to 200 nm, are effective carriers for drug molecules. Our novel oil-in-water nanoemulsion, NE-FLO™, formulated from lemon and fish byproduct oils, demonstrates promising antioxidant and anti-inflammatory activities, with initial studies indicating nontoxicity to normal skin cells. This study investigated the safety of NE-FLO™ using brine shrimp (Artemia salina) and zebrafish (Danio rerio) models, focusing on concentration-dependent effects and LC₅₀ values. At lower concentrations (0.1 mg·L⁻¹, 0.01 mg·L⁻¹, and 0.001 mg·L⁻¹), NE-FLO™ showed minimal toxicity without adverse effects. However, at 1 mg·L⁻¹, reduced survival rates indicate potential toxicity. Specifically, this concentration also induces altered swimming behaviors in zebrafish. LC₅₀ values are 8.7474 mg·L⁻¹ for brine shrimp and 0.316 mg·L⁻¹ for adult zebrafish. These results underscore the necessity for further detailed investigations into NE-FLO™, balancing its therapeutic benefits with potential toxicity risks. This study emphasizes the importance of optimizing nanoemulsion formulations from fish oil and conducting comprehensive safety assessments to meet regulatory standards. Full article

(This article belongs to the Special Issue Food Colloids: 3rd Edition)

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9 pages, 256 KiB

Open AccessArticle

Surfactant Distribution on the Liquid Surface Above an Approaching Particle

by Alexander A. Nepomnyashchy

Colloids Interfaces 2024, 8(6), 58; https://doi.org/10.3390/colloids8060058 - 24 Oct 2024

Viewed by 628

Abstract

The axisymmetric distribution of an insoluble surfactant on the liquid surface above a particle rising towards the surface has been considered. Under the assumption that the surface is fully covered by the surfactant, an analytical expression for the quasistationary surfactant distribution is found. [...] Read more.

The axisymmetric distribution of an insoluble surfactant on the liquid surface above a particle rising towards the surface has been considered. Under the assumption that the surface is fully covered by the surfactant, an analytical expression for the quasistationary surfactant distribution is found. The limits of the assumption validity are discussed. The conditions for the appearance of a region free of the surfactant is found. Full article

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Colloids Interfaces, Volume 8, Issue 6 (December 2024) – 10 articles

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