Colloids and Interfaces

18 pages, 12270 KiB

Open AccessArticle

Sulfonate Thiacalixarene-Modified Polydiacetylene Vesicles as Colorimetric Sensors for Lead Ion Detection

by Angelina A. Fedoseeva, Indira Yespanova, Elza D. Sultanova, Bulat Kh. Gafiatullin, Regina R. Ibragimova, Klara Kh. Darmagambet, Marina A. Il’ina, Egor O. Chibirev, Vladimir G. Evtugyn, Nurbol O. Appazov, Vladimir A. Burilov, Svetlana E. Solovieva and Igor S. Antipin

Colloids Interfaces 2025, 9(2), 20; https://doi.org/10.3390/colloids9020020 - 28 Mar 2025

Abstract

We report the first synthesis of zwitterionic thiacalixarenes featuring imidazolium and sulfonate groups on the upper rim and alkyl (butyl or octyl) fragments on the lower rim of the platform. Despite their amphiphilic structure, these macrocycles exhibit limited water solubility. However, dynamic light [...] Read more.

We report the first synthesis of zwitterionic thiacalixarenes featuring imidazolium and sulfonate groups on the upper rim and alkyl (butyl or octyl) fragments on the lower rim of the platform. Despite their amphiphilic structure, these macrocycles exhibit limited water solubility. However, dynamic light scattering detected the formation of associates for derivatives with octyl moieties at a concentration of 0.1 mM. To develop stable materials for aqueous environments and to investigate the functionality of zwitterionic sulfonate-imidazolium groups along with the thiacalixarene platform, mixed organo-organic systems based on polydiacetylene polymer were created. Characterization of the modified polydiacetylene systems through various analytical methods revealed a significant colorimetric response to lead ions in aqueous media, surpassing that of the unmodified polydiacetylene polymer. Additionally, the modified polymers demonstrated efficacy in purifying aqueous media from lead ions, as evidenced by anodic stripping voltammetry (ASV) and microwave plasma atomic emission spectroscopy (MP AES). Full article

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24 pages, 3728 KiB

Open AccessFeature PaperArticle

Surfactants Adsorption onto Algerian Rock Reservoir for Enhanced Oil Recovery Applications: Prediction and Optimization Using Design of Experiments, Artificial Neural Networks, and Genetic Algorithm (GA)

by Kahina Imene Benramdane, Mohamed El Moundhir Hadji, Mohamed Khodja, Nadjib Drouiche, Bruno Grassl and Seif El Islam Lebouachera

Colloids Interfaces 2025, 9(2), 19; https://doi.org/10.3390/colloids9020019 - 25 Mar 2025

Abstract

This study investigates the adsorption of surfactants on Algerian reservoir rock from Hassi Messaoud. A new data generation method based on a design of experiments (DOE) approach has been developed to improve the accuracy of adsorption modeling using artificial neural networks (ANNs). Unlike [...] Read more.

This study investigates the adsorption of surfactants on Algerian reservoir rock from Hassi Messaoud. A new data generation method based on a design of experiments (DOE) approach has been developed to improve the accuracy of adsorption modeling using artificial neural networks (ANNs). Unlike traditional data acquisition methods, this approach enables a methodical and structured exploration of adsorption behavior while reducing the number of required experiments, leading to improved prediction accuracy, optimization, and cost-effectiveness. The modeling is based on three key parameters: surfactant type (SDS and EOR ASP 5100), concentration, and temperature. The dataset required for ANN training was generated from a polynomial model derived from a full factorial design (DOE) established in a previous study. Before training, 32 different ANN configurations were evaluated by varying learning algorithms, adaptation functions, and transfer functions. The best-performing model was a cascade-type network employing the Levenberg–Marquardt learning function, learngdm adaptation, tansig activation function for the hidden layer, and purelin for the output layer, achieving an R² of 0.99 and an MSE of 6.84028 × 10⁻⁹. Compared to DOE-based models, ANN exhibited superior predictive accuracy, with a performance factor (PF/3) of 0.00157 and the same MSE. While DOE showed a slight advantage in relative error (9.10 × 10⁻⁵% vs. 1.88 × 10⁻⁴% for ANN), ANN proved more effective overall. Three optimization approaches—ANN-GA, DOE-GA, and DOE-DF (desirability function)—were compared, all converging to the same optimal conditions (SDS at 200 ppm and 25 °C). This similarity between the various optimization techniques confirms the strength of genetic algorithms for optimization in the field of EOR and that they can be reliably applied in practical field operations. However, ANN-GA exhibited slightly better convergence, achieving a fitness value of 2.3247. Full article

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15 pages, 7244 KiB

Open AccessArticle

Molecular Dynamics Study on the Lubrication Mechanism of the Phytic Acid/Copper Interface Under Loading Condition

by Min Guan, Dong Xie, Xiaoting Wang, Fengjuan Jing, Feng Wen and Yongxiang Leng

Colloids Interfaces 2025, 9(2), 18; https://doi.org/10.3390/colloids9020018 - 22 Mar 2025

Abstract

To investigate the lubrication mechanism of phytic acid (PA) solution, a “copper–PA solution–copper” confined model with varying concentrations was established. Molecular dynamics (MD) simulations were employed to model the behavior of compression and the confined shear process. By examining the variations in key [...] Read more.

To investigate the lubrication mechanism of phytic acid (PA) solution, a “copper–PA solution–copper” confined model with varying concentrations was established. Molecular dynamics (MD) simulations were employed to model the behavior of compression and the confined shear process. By examining the variations in key parameters such as dynamic viscosity, compressibility, radial distribution function, relative concentration distribution, and velocity distribution of PA solutions under different normal loads or shear rates, we elucidated the lubrication mechanism of PA solutions at the molecular level. The results demonstrate that under standard loading conditions, higher PA concentrations facilitate the formation of denser hydrated layers with decreased compressibility compared to free water, thereby significantly enhancing the load-bearing capacity. The shear stress at the solution–copper interface exhibits a substantial increase as the shear rate rises. This phenomenon originates from shear-driven migration of PA to the copper interface, disrupting the hydration layers and weakening hydrogen bonds. Consequently, this reduction in PA–water interactions amplifies slip velocity differences, ultimately elevating interfacial shear stress. The load-bearing capacity of the PA solution and the interfacial shear stress between the PA and copper are critical factors that influence the lubrication mechanism at the PA/Cu interface. This study establishes a theoretical foundation for the design and application of PA solution as a water-based lubricant, which holds significant importance for advancing the development of green lubrication technology. Full article

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26 pages, 1518 KiB

Open AccessReview

A Mini-Review on Enhancing Solubility in Topical Hydrogel Formulations Using Solid Dispersion Technology for Poorly Water-Soluble Drugs

by Zaid Dahma, Covadonga Álvarez-Álvarez and Paloma Marina de la Torre-Iglesias

Colloids Interfaces 2025, 9(2), 17; https://doi.org/10.3390/colloids9020017 - 21 Mar 2025

Abstract

The solubility behavior of drugs is a critical factor in formulation development. Approximately 40–45% of new drugs face market entry challenges due to low water solubility. Enhancing drug bioavailability is thus essential in developing pharmaceutical dosage forms. Many biopharmaceutical class II and IV [...] Read more.

The solubility behavior of drugs is a critical factor in formulation development. Approximately 40–45% of new drugs face market entry challenges due to low water solubility. Enhancing drug bioavailability is thus essential in developing pharmaceutical dosage forms. Many biopharmaceutical class II and IV drugs are commonly prescribed to treat inflammations, infections, and pain from various pathologies. Their oral administration has several drawbacks, including significant first-pass liver effects, low bioavailability, and adverse gastrointestinal effects. Topical application has gained relevance due to its advantages in delivering drugs directly to the target site, avoiding gastrointestinal irritation, and increasing their effectiveness. However, topical hydrogel formulations with poorly water-soluble drugs face challenges related to the skin’s permeability. Therefore, preparing topical hydrogels using solid dispersions (SDs) is an effective strategy to enhance the dissolution rate of poorly soluble drugs, thereby improving their topical bioavailability. In this review, the concepts of SDs, topical delivery systems, and topical hydrogel formulations incorporating SDs, as well as their preparation methods, characterization, and applications, will be discussed. Full article

(This article belongs to the Special Issue Biocolloids and Biointerfaces: 2nd Edition)

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14 pages, 1978 KiB

Open AccessArticle

Determination of Particle Mixture Composition by Visible Spectroscopy

by Mauricio Escudey, Lizethly Cáceres-Jensen and Manuel Gacitúa

Colloids Interfaces 2025, 9(2), 16; https://doi.org/10.3390/colloids9020016 - 12 Mar 2025

Abstract

Limited methods exist to determine the composition of particle mixtures. This research presents a simple UV-vis-spectroscopy-based method for the separate quantification of particles mixtures considering the following: synthesized ferrihydrite, commercial Fe₂O₃, and natural allophane. Calibration curves and adsorption/scattering coefficients [...] Read more.

Limited methods exist to determine the composition of particle mixtures. This research presents a simple UV-vis-spectroscopy-based method for the separate quantification of particles mixtures considering the following: synthesized ferrihydrite, commercial Fe₂O₃, and natural allophane. Calibration curves and adsorption/scattering coefficients are determined for each particle at different wavelengths. This is the main input to solve equation systems and, ultimately, quantify particle concentration in binary mixtures. The limit of detection varies with wavelength and particle type, yielding values as low as 1.5, 0.2, and 1.6 mg L⁻¹ for ferrihydrite (500 nm), Fe₂O₃ (450 nm), and natural allophane (450 nm), respectively. This study provides a simple, low-cost and straightforward method, compared to atomic-spectroscopy- or chromatography-based techniques, for resolving the composition of binary particle mixtures in suspension. Full article

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23 pages, 2278 KiB

Open AccessFeature PaperReview

Nanosized Being of Ionic Surfactant Micelles: An Advanced View on Micellization Process

by Olga S. Zueva, Mariia A. Kazantseva and Yuriy F. Zuev

Colloids Interfaces 2025, 9(2), 15; https://doi.org/10.3390/colloids9020015 - 28 Feb 2025

Abstract

An advanced model of ionic surfactant micellization has been developed. The structural and kinetic properties of micelles were analyzed in parallel from a universally accepted point of view and taking into account the principles of quantum mechanics, the phenomenon of ion pairing in [...] Read more.

An advanced model of ionic surfactant micellization has been developed. The structural and kinetic properties of micelles were analyzed in parallel from a universally accepted point of view and taking into account the principles of quantum mechanics, the phenomenon of ion pairing in the Stern layer, the symmetry considerations, and the chaos theory. It was shown that a micelle can be considered as a layered fullerene-like structure with a cavity in its center, possessing the solid-like properties of micelles in radial directions and the liquid-like properties in the perpendicular ones, allowing for water penetration between the surfactant head group and nearby methylene groups. The dimensions of the minimal fullerene-like structure formed by the terminal hydrogen atoms of surfactant methyl groups around the central cavity, unable to be occupied by surfactant tail fragments, were estimated. It was indicated that permanently occurring surfactant self-organization/disintegration needs a probabilistic description and revision of processes occurring in micellar systems built by ionic surfactants. It was noted that the probabilistic approach alters the mechanism of colloidal dissolution of hydrocarbon compounds and their solubilization by micelles. The advanced model proposes the same macroscopic properties of micelles as the classical one but modifies the structural characteristics of micelles on the nanoscale. Full article

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46 pages, 13796 KiB

Open AccessFeature PaperReview

Measurement Techniques for Interfacial Rheology of Surfactant, Asphaltene, and Protein-Stabilized Interfaces in Emulsions and Foams

by Ronald Marquez and Jean-Louis Salager

Colloids Interfaces 2025, 9(1), 14; https://doi.org/10.3390/colloids9010014 - 14 Feb 2025

Abstract

This work provides a comprehensive review of experimental methods used to measure rheological properties of interfacial layers stabilized by surfactants, asphaltenes, and proteins that are relevant to systems with large interfacial areas, such as emulsions and foams. Among the shear methods presented, the [...] Read more.

This work provides a comprehensive review of experimental methods used to measure rheological properties of interfacial layers stabilized by surfactants, asphaltenes, and proteins that are relevant to systems with large interfacial areas, such as emulsions and foams. Among the shear methods presented, the deep channel viscometer, bicone rheometer, and double-wall ring rheometers are the most utilized. On the other hand, the main dilational rheology techniques discussed are surface waves, capillary pressure, oscillating Langmuir trough, oscillating pendant drop, and oscillating spinning drop. Recent developments—including machine learning and artificial intelligence (AI) models, such as artificial neural networks (ANN) and convolutional neural networks (CNN)—to calculate interfacial tension from drop shape analysis in shorter times and with higher precision are critically analyzed. Additionally, configurations involving an Atomic Force Microscopy (AFM) cantilever contacting bubble, a microtensiometer platform, rectangular and radial Langmuir troughs, and high-frequency oscillation drop setups are presented. The significance of Gibbs–Marangoni effects and interfacial rheological parameters on the (de)stabilization of emulsions is also discussed. Finally, a critical review of the recent literature on the measurement of interfacial rheology is presented. Full article

(This article belongs to the Special Issue Rheology of Complex Fluids and Interfaces)

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17 pages, 2350 KiB

Open AccessFeature PaperArticle

Viral Clearance of Cupric-Modified Phyllosilicate Minerals Against Enveloped and Non-Enveloped Viruses

by Vaishali Sharma, Sneha Singh, Natalie M. Nold, Supreet Kaur, Bowen Li and Caryn L. Heldt

Colloids Interfaces 2025, 9(1), 13; https://doi.org/10.3390/colloids9010013 - 14 Feb 2025

Abstract

The effectiveness of copper-based composites, specifically cupric ion (Cu²⁺)-modified phyllosilicate minerals, was evaluated in reducing the concentration of infectious agents in the environment while minimizing metal ion release. The phyllosilicate minerals, vermiculite, exfoliated and unexfoliated, and sepiolite, all modified with Cu [...] Read more.

The effectiveness of copper-based composites, specifically cupric ion (Cu²⁺)-modified phyllosilicate minerals, was evaluated in reducing the concentration of infectious agents in the environment while minimizing metal ion release. The phyllosilicate minerals, vermiculite, exfoliated and unexfoliated, and sepiolite, all modified with Cu²⁺, were compared with copper oxide for their antiviral activity against non-enveloped porcine parvovirus (PPV) and enveloped human coronavirus 229E (HCoV). Sepiolite effectively removed PPV and HCoV from the solution, regardless of Cu²⁺ presence, while vermiculite showed substantial viral clearance only when Cu²⁺ was present. The kinetics of viral clearance was fast, with complete clearance within one hour in many cases. To better understand the mechanism of virus clearance, EDTA was added at different times during the clearance study for PPV. EDTA prevented virus clearance in all vermiculite samples, whereas sepiolite containing copper still demonstrated substantial virus clearance. The addition of BSA before the virus binding was able to block binding in all cases. It was determined that binding is the key mechanism, and PPV can be eluted from the minerals with EDTA and still be infectious. This study provides the potent antiviral mechanisms of Cu²⁺-modified phyllosilicate minerals, offering insights for designing paints and plastics for high-touch surfaces to reduce viral transmission and enhance public health significantly. Full article

(This article belongs to the Special Issue Biocolloids and Biointerfaces: 2nd Edition)

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11 pages, 2190 KiB

Open AccessFeature PaperArticle

Transient Electroosmosis on a Soft Surface

by Hiroyuki Ohshima

Colloids Interfaces 2025, 9(1), 12; https://doi.org/10.3390/colloids9010012 - 4 Feb 2025

Cited by 1

Abstract

A general theory was developed for the time-dependent transient electroosmosis on a planar soft surface, i.e., a polyelectrolyte-coated solid surface in an electrolyte solution, when an electric field is suddenly applied. This serves as a simple model for the time-dependent electrokinetic phenomena occurring [...] Read more.

A general theory was developed for the time-dependent transient electroosmosis on a planar soft surface, i.e., a polyelectrolyte-coated solid surface in an electrolyte solution, when an electric field is suddenly applied. This serves as a simple model for the time-dependent electrokinetic phenomena occurring at biointerfaces. A closed-form approximate expression is derived for the electroosmotic velocity distribution within the polyelectrolyte layer as a function of both position and time. This analysis reveals that the temporal and spatial variations in the electroosmotic flow caused by the surface charges of the solid surface is confined to the region near the solid surface. In contrast, the variations due to the fixed charges within the polyelectrolyte layer extend over a wider region inside the polyelectrolyte layer. Full article

(This article belongs to the Special Issue Biocolloids and Biointerfaces: 2nd Edition)

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11 pages, 3405 KiB

Open AccessArticle

Effect of Size Asymmetry of Latex Nanoparticles on Formation and Properties of Nanocolloidal Gels

by Sofia M. Morozova and Tatiana G. Statsenko

Colloids Interfaces 2025, 9(1), 11; https://doi.org/10.3390/colloids9010011 - 28 Jan 2025

Abstract

The study of the fundamental principles of gelation of colloidal nanoparticles (NPs) advances the understanding of the formation of colloidal systems of living organisms. In this paper, the effect of particle size for a binary system of oppositely charged latexes on the experimental [...] Read more.

The study of the fundamental principles of gelation of colloidal nanoparticles (NPs) advances the understanding of the formation of colloidal systems of living organisms. In this paper, the effect of particle size for a binary system of oppositely charged latexes on the experimental parameters of the system, including the gelation region, rheological parameters and cluster size, is considered for the first time. It is shown that the gelation regions in the phase diagrams for asymmetric particles are symmetric with respect to the ratio of charge and surface area of the particles. It was found that asymmetric particles form denser gels compared with the same concentration of symmetrical particles. This work provides insight into the gelation of asymmetric NPs, which is important for numerous applications, including their utilization in colloidal gels as ink for additive manufacturing and as scaffolds for cell growth, as well as understanding the fundamental aspects of the formation of bio-colloids. Full article

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17 pages, 3356 KiB

Open AccessArticle

Encapsulation of Canola Oil by Sonication for the Development of Protein and Starch Systems: Physical Characteristics and Rheological Properties

by Reynaldo J. Silva-Paz, Celenia E. Ñope-Quito, Thalia A. Rivera-Ashqui, Nicodemo C. Jamanca-Gonzales, Amparo Eccoña-Sota, Natalia Riquelme and Carla Arancibia

Colloids Interfaces 2025, 9(1), 10; https://doi.org/10.3390/colloids9010010 - 22 Jan 2025

Abstract

Canola oil, extracted from Brassica napus, is appreciated for its nutritional profile, but its use in the food industry is limited by its susceptibility to oxidation. This study aimed to evaluate the nanoemulsion of canola oil by sonication to develop stable nanoemulsified [...] Read more.

Canola oil, extracted from Brassica napus, is appreciated for its nutritional profile, but its use in the food industry is limited by its susceptibility to oxidation. This study aimed to evaluate the nanoemulsion of canola oil by sonication to develop stable nanoemulsified gels from protein and starch systems. Two stages were performed. In the first stage, oil-in-water (O/W) nanoemulsions were prepared using soy lecithin and Tween 80 as emulsifiers, analyzing their physical stability by particle size and polydispersity index. The results show that the sonication conditions and emulsifier concentration significantly affected the creaming index and particle size. In the second stage, gels were developed from these nanoemulsions, evaluating their colorimetric and rheological properties. It was observed that the gels presented a viscoelastic behavior suitable for food applications, with a higher luminosity in protein systems. In conclusion, nanoemulsion by sonication improves the stability of canola oil, suggesting its potential use in various food applications. Additional emulsifier combinations and optimization of processing conditions are recommended to further improve the stability and functionality of the encapsulated oil. Full article

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

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19 pages, 4221 KiB

Open AccessFeature PaperArticle

Bio-Based Interpolyelectrolyte Complexes for the Stabilization of Pickering-like Emulsions

by Francisco Joel Guerrero-Vasquez, Francisco Ortega, Ramón G. Rubio and Eduardo Guzmán

Colloids Interfaces 2025, 9(1), 9; https://doi.org/10.3390/colloids9010009 - 22 Jan 2025

Abstract

This work studies the stabilization of Pickering-like emulsions using dispersions of interpolyelectrolyte complexes (IPECs) formed by chitosan (CS) and sodium alginate (ALG), two polymers from natural resources, as the aqueous phase and soybean oil as the oil phase. The ability of these bio-based [...] Read more.

This work studies the stabilization of Pickering-like emulsions using dispersions of interpolyelectrolyte complexes (IPECs) formed by chitosan (CS) and sodium alginate (ALG), two polymers from natural resources, as the aqueous phase and soybean oil as the oil phase. The ability of these bio-based IPECs to form stable emulsions was evaluated by varying the compositional ratio of CS to ALG (Z-ratio) and the oil volume fraction (ϕ_o). Turbidity, zeta potential, and dynamic light scattering measurements revealed the dependence of IPEC properties on the Z-ratio, with phase separation observed near stoichiometric ratios. Phase diagram analysis showed that stable oil-in-water (O/W) and water-in-oil (W/O) emulsions could be obtained under certain combinations of the Z-ratio and ϕ_o. Emulsion stability increased with higher Z-ratios due to increased interfacial activity of the complexes and reduced coalescence. Emulsions with high ϕ_o exhibited transitions from discrete droplets to bicontinuous interfacially jammed emulsion gels (bijels), suggesting tunable morphologies. These results highlight the potential of CHI-ALG IPECs as eco-friendly and efficient stabilizers of Pickering-like emulsions for applications in food, cosmetics and pharmaceuticals. Full article

(This article belongs to the Special Issue State of the Art of Colloid and Interface Science in the Iberian Peninsula)

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10 pages, 1873 KiB

Open AccessFeature PaperArticle

An Imine-Based Two-Dimensional Covalent Organic Framework for Gemcitabine Delivery

by Kajal Kaliya, Neha Bhardwaj, Ruchika and Ankit Saneja

Colloids Interfaces 2025, 9(1), 8; https://doi.org/10.3390/colloids9010008 - 21 Jan 2025

Abstract

A 2D imine-linked covalent organic framework (COF) with good biocompatibility was synthesized using o-Dianisidine and 1,3,5-Triformylbenzene. The synthesized COF was characterized by using the Fourier transform infrared (FTIR), thermogravimetry analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized COF [...] Read more.

A 2D imine-linked covalent organic framework (COF) with good biocompatibility was synthesized using o-Dianisidine and 1,3,5-Triformylbenzene. The synthesized COF was characterized by using the Fourier transform infrared (FTIR), thermogravimetry analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized COF was subsequently utilized for the delivery of gemcitabine (Gem), an FDA-approved drug for the treatment of pancreatic cancer. The COF demonstrated a remarkable drug loading of 30 µg/mg and better drug release at pH 5.0. The biocompatibility of the COF was evaluated in the L929 (mouse fibroblast) cell line, while the cytotoxicity of the Gem-loaded COF (COF-Gem) was evaluated against the MIA-PaCa-2 and PANC-1 (pancreatic cancer) cell lines using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The results indicated that the COF was safe at concentrations up to 200 µg/mL, while the COF-Gem led to superior cytotoxicity as compared to native Gem, with IC₅₀ values of 8.1 ± 1.2 µM in MIA-PaCa-2 cells and 6.0 ± 1.3 µM in PANC-1 cells after 48 h. This study offers a new perspective of utilizing COF as a promising delivery system for Gem delivery. Full article

(This article belongs to the Special Issue Biocolloids and Biointerfaces: 2nd Edition)

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13 pages, 1177 KiB

Open AccessArticle

Transient Diffusiophoresis of a Spherical Colloidal Particle

by Hiroyuki Ohshima

Colloids Interfaces 2025, 9(1), 7; https://doi.org/10.3390/colloids9010007 - 19 Jan 2025

Cited by 1

Abstract

A general theoretical approach is introduced to analyze the time-dependent, transient diffusiophoresis of a charged spherical colloidal particle in a symmetrical electrolyte solution when an electrolyte concentration gradient is suddenly applied. We derive a closed-form approximate expression for the relaxation function R( [...] Read more.

A general theoretical approach is introduced to analyze the time-dependent, transient diffusiophoresis of a charged spherical colloidal particle in a symmetrical electrolyte solution when an electrolyte concentration gradient is suddenly applied. We derive a closed-form approximate expression for the relaxation function R(t), which describes the time course of the diffusiophoretic mobility of a weakly charged spherical colloidal particle possessing a thin electrical double layer. The relaxation function depends on the mass density ratio of the particle to the electrolyte solution and the kinematic viscosity. However, it does not depend on the type of electrolyte (e.g., KCl or NaCl). It is also found that the expression for the relaxation function in transient diffusiophoresis of a weakly charged spherical colloidal particle with a thin electrical double layer takes the same form as that for its transient electrophoresis. Full article

(This article belongs to the Special Issue Biocolloids and Biointerfaces: 2nd Edition)

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15 pages, 7577 KiB

Open AccessFeature PaperArticle

Experimental Investigation of Stability of Emulsions Produced by Catastrophic Phase Inversion Using Non-Ionic Surfactants

by Maria Doutsi, Maria C. Vlachou, Christos Koukiotis, Margaritis Kostoglou and Thodoris D. Karapantsios

Colloids Interfaces 2025, 9(1), 6; https://doi.org/10.3390/colloids9010006 - 16 Jan 2025

Abstract

Emulsions stabilized by environmentally friendly surfactants have been at the center of research attention over recent decades. Non-ionic surfactants with good biodegradability, while being non-toxic and non-irritating, have dominated in this area. For a chosen system, the main goal is to engineer its [...] Read more.

Emulsions stabilized by environmentally friendly surfactants have been at the center of research attention over recent decades. Non-ionic surfactants with good biodegradability, while being non-toxic and non-irritating, have dominated in this area. For a chosen system, the main goal is to engineer its properties for smaller droplet sizes and better stability, a process which is mainly derived from the emulsification method. In the present study, Ethylan 1005 and Ethylan 1008 were used as stabilizers, both alone and combined at different ratios, in eco-friendly emulsions produced by paraffin oil and Millipore water, via direct emulsification, catastrophic phase inversion and catastrophic phase inversion in droplets. During the experiments, the emulsions’ rheological behavior, phase separation, and droplet size distribution profiles were measured. Catastrophic phase inversion in droplets resulted in the finest droplet size distributions for both emulsifiers when used alone. As the concentration of Ethylan 1008 increased from 0% to 100% in the surfactant mixtures, the droplets’ mean diameter and range also increased, indicting degradation of emulsion stability. However, phase separation tests revealed the opposite. Explanation was found in the chemical structure of the two emulsions and the steric phenomena caused by this, while a semi-quantitative analysis of these trends was also developed. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of Colloids and Interfaces 2024–2025)

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26 pages, 44536 KiB

Open AccessArticle

Polydispersity and Composition Stability in a Long-Term Follow-Up of Palmarosa (Cymbopogon Martini) and Tea Tree (Melaleuca Alternifolia) O/W Nanoemulsions for Antibacterial Use

by Erick Sánchez-Gaitán, Vianney González-López and Francisco Delgado

Colloids Interfaces 2025, 9(1), 5; https://doi.org/10.3390/colloids9010005 - 14 Jan 2025

Abstract

There is a growing focus on the design of nanoemulsions because of their valuable properties as an enhanced vehicle for interaction with cells and resistant bacteria. Their potential applications in the health and food industry are numerous. Although they are considered unstable because [...] Read more.

There is a growing focus on the design of nanoemulsions because of their valuable properties as an enhanced vehicle for interaction with cells and resistant bacteria. Their potential applications in the health and food industry are numerous. Although they are considered unstable because of flocculation and coalescence, they are still efficient resources for antibacterial inhibition due to their droplet size. Studies on the interactions between essential oils and an aqueous medium are increasing, in order to efficiently formulate them at the nanometric scale using surfactants, thereby providing them with long-lived droplet size stability. This study used the ultrasonication method for fabrication and Eumulgin as a surfactant to achieve nanometric droplet sizes using two noble essential oils, palmarosa and tea tree. A follow-up for one year tracked a stable droplet size and sustained polydispersity in those emulsions as the most valuable outcome. Moreover, the insights of a thermoresponsive study have been included, also showing a strong stability. The antibacterial properties of the essential oils considered became enhanced, at a comparable scale of an antibiotic, on Salmonella spp. and Bacillus subtilis depending on the nanoscale droplet size. The outcomes suggest the importance of deepening parametric studies of these nanoformulations in terms of concentrations and temperature changes, characterizing their remarkable properties and durability. Full article

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19 pages, 2309 KiB

Open AccessFeature PaperArticle

Micellization and Physicochemical Properties of CTAB in Aqueous Solution: Interfacial Properties, Energetics, and Aggregation Number at 290 to 323 K

by Bappaditya Naskar

Colloids Interfaces 2025, 9(1), 4; https://doi.org/10.3390/colloids9010004 - 9 Jan 2025

Abstract

This work reports a detailed investigation of the micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) over the temperature range of 290–313 K. Conductometry, tensiometry, fluorimetry, and isothermal titration calorimetry (ITC) were used to study the overall solution behavior of amphiphilic self-aggregation. The [...] Read more.

This work reports a detailed investigation of the micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) over the temperature range of 290–313 K. Conductometry, tensiometry, fluorimetry, and isothermal titration calorimetry (ITC) were used to study the overall solution behavior of amphiphilic self-aggregation. The CMC values showed a trend of first declining and then rising with a minimum temperature of 298 K. The adsorption at the air–water interface and micellization processes of CTAB are both spontaneous. The enthalpy of CTAB micellization is negative at 290 K and increases negatively as the temperature rises. The interfacial parameters—maximum surface excess concentration (Γ_max), minimum area per molecule (A_min), standard free energy of adsorption (A_min), and surface pressure at CMC (Π_CMC)—were calculated using surface tension data. The aggregation numbers (N) of CTAB micelles and others (SDS and CHAPS) determined at different [surfactant]>CMC by the static fluorescence quenching method were used to find out the N values at CMC (or N^CMC). The results revealed that the N^CMC values were 48, 54, and 4 for CTAB, SDS, and CHAPS micelles, respectively. Temperature-dependent N^CMC by the ITC method was also examined for the studied surfactants. Additionally, the ITC-determined specific heat of micellization was used to find out the extent of water penetration into the micelle interior of up to 8, 7, and 3 hydrocarbons for CTAB, SDS, and CHAPS, respectively. Full article

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18 pages, 6011 KiB

Open AccessReview

Application of Porous Materials in Photocatalytic Treatment of Wastewater

by Jian Nan, Xinyu Liu, Di Zhang, Rui Xu and Yong Zhang

Colloids Interfaces 2025, 9(1), 3; https://doi.org/10.3390/colloids9010003 - 3 Jan 2025

Abstract

With the increasing environmental water pollution, there is an increasing demand for efficient and sustainable wastewater treatment technologies. Photocatalysis, as an environmentally friendly oxidation technology, shows significant promise for the degradation and mineralization of organic pollutants in wastewater. Porous structured materials have received [...] Read more.

With the increasing environmental water pollution, there is an increasing demand for efficient and sustainable wastewater treatment technologies. Photocatalysis, as an environmentally friendly oxidation technology, shows significant promise for the degradation and mineralization of organic pollutants in wastewater. Porous structured materials have received much attention from scientists for the photocatalytic treatment of wastewater due to their good dispersibility and high specific surface area. Based on the exploration of the recent research papers about various porous materials in photocatalytic degradation of wastewater, we summarize the synthesis of porous materials and methods of loading catalysts, explore the applications for treating different types of pollutants, and finally present the challenges and prospects of porous materials in photocatalytic wastewater treatment. We hope that this review will inspire more researchers to focus on this important field. Full article

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12 pages, 2616 KiB

Open AccessArticle

Microencapsulation Efficiency of DCOIT Biocide in the TPM/SiO₂ System and a Study of Their Acute Toxicity

by Assem Issayeva, Saule Aidarova, Galiya Madybekova, Seitzhan Turganbay, Alpamys Babayev, Miras Issakhov, Altynay Sharipova, Reinhard Miller and Botagoz Mutaliyeva

Colloids Interfaces 2025, 9(1), 2; https://doi.org/10.3390/colloids9010002 - 31 Dec 2024

Abstract

Biocides are often used in various industries and applications to control microbial growth and prevent the deterioration of materials, and they often have the ability to target a wide range of microorganisms rather than being specific to one type. They are designed to [...] Read more.

Biocides are often used in various industries and applications to control microbial growth and prevent the deterioration of materials, and they often have the ability to target a wide range of microorganisms rather than being specific to one type. They are designed to be highly effective at killing or inhibiting the growth of microorganisms and some biocides have residual activity, meaning they remain active for a period of time after application, providing longer-term protection. Biocides need to be compatible with the materials and surfaces they are applied to without causing damage or adverse effects, and they should remain stable under various environmental conditions, such as temperature and pH, to maintain their efficacy over time. In this study, microcapsules incorporating the biocide 4,5-dichloro-2-n-octyl-4-isotriazolin-3-one (DCOIT) were synthesized, and their effectiveness was evaluated. The investigation focused on several aspects, including colloidal chemical properties such as interfacial tension at pH values of 3, 7, and 9, as well as the size, ζ-potential, and morphology of the microcapsules. To validate the microcapsule production, elemental analysis was performed, and the effects on wettability and toxicological properties were assessed within the DCOIT + trimethoxysilyl propylmethacrylate/silicon dioxide nanoparticle system. Interfacial tension kinetics were measured using the PAT-1 tensiometer. The microcapsules exhibited an average diameter of 146 ± 1 nm following emulsification, with a ζ-potential of −50.2 ± 1 mV, as determined by the Malvern Zetasizer Nano Z. The morphology of the microcapsules was characterized using the SEM Controller 1550. Elemental composition was analyzed via energy-dispersive X-ray microanalysis (EDAX). The study concluded that the DCOIT biocide, when incorporated in the TPM/SiO₂ system, demonstrated non-toxic properties. Full article

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Colloids and Interfaces

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