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Colloids Interfaces, Volume 8, Issue 3 (June 2024) – 12 articles

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19 pages, 1315 KiB  
Article
An Investigation of the Effect of pH on Micelle Formation by a Glutamic Acid-Based Biosurfactant
by Jacob D. Mayer, Robert M. Rauscher, Shayden R. Fritz, Yayin Fang, Eugene J. Billiot, Fereshteh H. Billiot and Kevin F. Morris
Colloids Interfaces 2024, 8(3), 38; https://doi.org/10.3390/colloids8030038 - 11 Jun 2024
Viewed by 237
Abstract
NMR spectroscopy, molecular modeling, and conductivity experiments were used to investigate micelle formation by the amino acid-based surfactant tridecanoic L-glutamic acid. Amino acid-based biosurfactants are green alternatives to surfactants derived from petroleum. NMR titrations were used to measure the monomeric surfactant’s primary and [...] Read more.
NMR spectroscopy, molecular modeling, and conductivity experiments were used to investigate micelle formation by the amino acid-based surfactant tridecanoic L-glutamic acid. Amino acid-based biosurfactants are green alternatives to surfactants derived from petroleum. NMR titrations were used to measure the monomeric surfactant’s primary and gamma (γ) carboxylic acid pKa values. Intramolecular hydrogen bonding within the surfactant’s headgroup caused the primary carboxylic acid to be less acidic than the corresponding functional group in free L-glutamic acid. Likewise, intermolecular hydrogen bonding caused the micellar surfactant’s γ carboxylic functional group to be less acidic than the corresponding monomer value. The binding of four positive counterions to the anionic micelles was also investigated. At pH levels below 7.0 when the surfactant headgroup charge was −1, the micelle hydrodynamic radii were larger (~30 Å) and the mole fraction of micelle-bound counterions was in the 0.4–0.7 range. In the pH range of 7.0–10.5, the micelle radii decreased with increasing pH and the mole fraction of micelle bound counterions increased. These observations were attributed to changes in the surfactant headgroup charge with pH. Above pH 10.5, the counterions deprotonated and the mole fraction of micelle-bound counterions decreased further. Finally, critical micelle concentration measurements showed that the micelles formed at lower concentrations at pH 6 when the headgroup charge was predominately −1 and at higher concentrations at pH 7 where headgroups had a mixture of −1 and −2 charges in solution. Full article
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16 pages, 1728 KiB  
Article
Biocomposite Films of Amylose Reinforced with Polylactic Acid by Solvent Casting Method Using a Pickering Emulsion Approach
by Marwa Faisal, Jacob Judas Kain Kirkensgaard, Bodil Jørgensen, Peter Ulvskov, Max Rée, Sue Kang, Nikolai Andersson, Mikkel Jørgensen, Jonas Simonsen, Kim H. Hebelstrup and Andreas Blennow
Colloids Interfaces 2024, 8(3), 37; https://doi.org/10.3390/colloids8030037 - 9 Jun 2024
Viewed by 359
Abstract
Binary and ternary blends of amylose (AM), polylactic acid (PLA), and glycerol were prepared using a Pickering emulsion approach. Various formulations of AM/PLA with low PLA contents ranging from 3% to 12% were mixed with AM matrix and reinforced with 25% cellulose nanofibers [...] Read more.
Binary and ternary blends of amylose (AM), polylactic acid (PLA), and glycerol were prepared using a Pickering emulsion approach. Various formulations of AM/PLA with low PLA contents ranging from 3% to 12% were mixed with AM matrix and reinforced with 25% cellulose nanofibers (CNF), and PLA-grafted cellulose nanofibers (g-CNF), the latter to enhance miscibility. Polymeric films were fabricated through solvent casting and characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Wide-Angle X-ray Scattering (WAXS), and the evaluations of physical, mechanical properties, and wettability were performed using contact angle measurements. The binary blends of AM and PLA produced films suitable for packaging, pharmaceutical, or biomedical applications with excellent water barrier properties. The ternary blends of AM/CNF/PLA and AM/g-CNF/PLA nanocomposite films demonstrated enhanced tensile strength and reduced water permeability compared to AM/PLA films. Adding g-CNF resulted in better homogeneity and increased relative crystallinity from 33% to 35% compared to unmodified CNF. The application of Pickering emulsion in creating AM-based CNF/ PLA composites resulted in a notable enhancement in tensile strength by 47%. This study presents an effective approach for producing biodegradable and reinforced PLA-based nanocomposite films, which show promise as bio-nanocomposite materials for food packaging applications. Full article
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19 pages, 9237 KiB  
Article
Diffusiophoresis of a Charged Soft Sphere in a Charged Spherical Cavity
by Wei-Zhi Chen and Huan-Jang Keh
Colloids Interfaces 2024, 8(3), 36; https://doi.org/10.3390/colloids8030036 - 2 Jun 2024
Viewed by 342
Abstract
The quasi-steady diffusiophoresis of a soft particle composed of an uncharged hard sphere core and a uniformly charged porous surface layer in a concentric charged spherical cavity full of a symmetric electrolyte solution with a concentration gradient is analyzed. By using a regular [...] Read more.
The quasi-steady diffusiophoresis of a soft particle composed of an uncharged hard sphere core and a uniformly charged porous surface layer in a concentric charged spherical cavity full of a symmetric electrolyte solution with a concentration gradient is analyzed. By using a regular perturbation method with small fixed charge densities of the soft particle and cavity wall, the linearized electrokinetic equations relevant to the fluid velocity field, electric potential profile, and ionic concentration distributions are solved. A closed-form formula for the diffusiophoretic (electrophoretic and chemiphoretic) velocity of the soft particle is obtained as a function of the ratios of the core-to-particle radii, particle-to-cavity radii, particle radius to the Debye screening length, and particle radius to the permeation length in the porous layer. In typical cases, the confining charged cavity wall significantly influences the diffusiophoresis of the soft particle. The fluid flow caused by the diffusioosmosis (electroosmosis and chemiosmosis) along the cavity wall can considerably change the diffusiophoretic velocity of the particle and even reverse its direction. In general, the diffusiophoretic velocity decreases with increasing core-to-particle radius ratios, particle-to-cavity radius ratios, and the ratio of the particle radius to the permeation length in the porous layer, but increases with increasing ratios of the particle radius to the Debye length. Full article
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14 pages, 1346 KiB  
Article
Silk Fibroin Self-Assembly at the Air–Water Interface
by Olga Yu. Milyaeva, Alexander V. Akentiev, Alexey G. Bykov, Reinhard Miller, Anastasiya R. Rafikova, Kseniya Yu. Rotanova and Boris A. Noskov
Colloids Interfaces 2024, 8(3), 35; https://doi.org/10.3390/colloids8030035 - 2 Jun 2024
Viewed by 266
Abstract
Amphiphilic silk fibroin (SF) forms stable adsorption layers at the air–water interface. The range of the investigated protein concentrations can be divided into two parts according to the peculiarities of the surface layer properties. At protein concentrations from 0.0005 to 0.01 mg/mL, the [...] Read more.
Amphiphilic silk fibroin (SF) forms stable adsorption layers at the air–water interface. The range of the investigated protein concentrations can be divided into two parts according to the peculiarities of the surface layer properties. At protein concentrations from 0.0005 to 0.01 mg/mL, the dynamic surface elasticity monotonically increases with the concentration and surface age and reaches values of up to 220 mN/m. In this range, the adsorption layer compression leads to a fast increase of the surface pressure. In the second part (>0.01 mg/mL), the surface elasticity decreases again and the kinetic dependences of the film thickness and adsorbed amount change only a little. In this case, the layer compression leads only to a slight increase of the surface pressure. These two types of behavior can be attributed to the distinctions in the protein aggregation in the surface layer. Atomic force microscopy (AFM) investigations of the layers transferred from the liquid surface onto a mica surface by the Langmuir–Schaefer method show some peculiarities of the layer morphology in the intermediate concentration range (~0.02 mg/mL). Full article
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14 pages, 1816 KiB  
Article
The Role of Adsorption Phenomena in ac Conductivity Measurements of Dielectric Nanoparticle Suspensions
by Ioulia Chikina and Andrey Varlamov
Colloids Interfaces 2024, 8(3), 34; https://doi.org/10.3390/colloids8030034 - 28 May 2024
Viewed by 432
Abstract
The authors of numerous measurements of conductivity for suspensions of nanoparticles of various types carried out in the last decade came to the general conclusion that the well-known Maxwell’s theory is not applicable to quantitative explanation of the properties of such systems. In [...] Read more.
The authors of numerous measurements of conductivity for suspensions of nanoparticles of various types carried out in the last decade came to the general conclusion that the well-known Maxwell’s theory is not applicable to quantitative explanation of the properties of such systems. In the present work, we demonstrate that the Maxwell’s theory can be still applicable even for such systems, but the specifics of the standard ac measurements have to be correctly taken into account. Namely, the dependence of the capacitance of “metal–electrolyte” cuvette boundaries on nanoparticle adsorption, which in its turn dramatically depends on nanoparticle concentration, has to be taken into account. The latter circumstance strongly (via the RC characteristic of the circuit) affects the results of conductivity measurements. We propose the new algorithm of the impedance measurement data analysis for the particles’ concentration dependence of conductivity σ(ϕ) (where ϕ is the volume fraction of nanoparticles in suspension) for the suspensions of the diamante nanoparticles in alcohol which demonstrates the adequate correspondence of the Maxwell’s theory to the available experimental findings. Full article
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14 pages, 3059 KiB  
Article
Discontinuous Shear Thickening of Suspensions of Magnetic Particles in Relation to the Polymer Coating on Their Surfaces
by Georges Bossis, Olga Volkova and Yan Grasselli
Colloids Interfaces 2024, 8(3), 33; https://doi.org/10.3390/colloids8030033 - 17 May 2024
Viewed by 474
Abstract
The phenomenon of discontinuous shear thickening (DST) is observed in suspensions of solid particles with a very high-volume fraction. It is characterized by an abrupt decrease in the shear rate for critical stress during a ramp of stress. This behavior can be reproduced [...] Read more.
The phenomenon of discontinuous shear thickening (DST) is observed in suspensions of solid particles with a very high-volume fraction. It is characterized by an abrupt decrease in the shear rate for critical stress during a ramp of stress. This behavior can be reproduced in numerical simulations by introducing a local friction between two particles above a given local force. We present experimental results showing this DST behavior obtained with suspensions of magnetic (iron) and nonmagnetic (calcium carbonate) particles and different amounts of a superplasticizer molecule used in the cement industry. For both types of particles, the same behavior was observed with first an increase in critical stress with the amount of plasticizer followed by a decrease at higher concentrations but with a larger viscosity before critical stress was reached. At a low concentration of plasticizer, the low critical stress is interpreted by the local sliding of plasticizer molecules on the surface of particles. At higher concentrations, when total coverage is achieved, the critical stress is higher since it has to remove the molecules out of the surface. At still higher concentrations, the increase in viscosity is explained by the formation of multilayers of molecules on the surface of the particles. This interpretation is supported by the measurement of the adsorption isotherm of the plasticizer on the surface of the particles. Full article
(This article belongs to the Special Issue Rheology of Complex Fluids and Interfaces)
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10 pages, 3474 KiB  
Article
Flowable Electrodes from Colloidal Suspensions of Thin Multiwall Carbon Nanotubes
by Massinissa Hamouma, Wilfrid Neri, Xavier Bril, Jinkai Yuan, Annie Colin, Nicolas Brémond and Philippe Poulin
Colloids Interfaces 2024, 8(3), 32; https://doi.org/10.3390/colloids8030032 - 17 May 2024
Viewed by 473
Abstract
Flowable electrodes, a versatile alternative to traditional solid electrodes for electrochemical applications, exhibit challenges of high viscosity and carbon content, limiting flow and device performances. This study introduces colloidal suspensions of thin multiwall carbon nanotubes (MWCNTs) with diameters of 10–15 nm as electrode [...] Read more.
Flowable electrodes, a versatile alternative to traditional solid electrodes for electrochemical applications, exhibit challenges of high viscosity and carbon content, limiting flow and device performances. This study introduces colloidal suspensions of thin multiwall carbon nanotubes (MWCNTs) with diameters of 10–15 nm as electrode materials. These thin nanotubes, stabilized in water with a surfactant, form percolated networks, exhibiting high conductivity (50 ms/cm) and stability at a low carbon content (below 2 wt%). Colloidal clustering is enhanced by weak depletion attractive interactions. The resulting suspensions display yield stress and a shear thinning behavior with a low consistency index. They can easily flow at a nearly constant shear over a broad range of shear rates. They remain electrically conductive under shear, making them a promising option for flow electrochemical applications. This work suggests that the use of depletion-induced MWVNT aggregates addresses crucial issues in flow electrochemical applications, such as membrane fragility, operating energy, and pressure. These conductive colloidal suspensions thereby offer potential advancements in device performance and lifespan. Full article
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16 pages, 3691 KiB  
Review
A Review of Investigations and Applications of Biocides in Nanomaterials and Nanotechnologies
by Assem Issayeva, Altynay Sharipova, Saule Aidarova, Galiya Madybekova, Jaroslav Katona, Seitzhan Turganbay and Reinhard Miller
Colloids Interfaces 2024, 8(3), 31; https://doi.org/10.3390/colloids8030031 - 16 May 2024
Viewed by 498
Abstract
In recent years, the development of nanomaterials with biocidal properties has received considerable attention due to their potential applications in various industries, including food, medicine, and cultural heritage preservation. The growing demand for coatings with antibacterial properties has sparked interest from industrial sectors [...] Read more.
In recent years, the development of nanomaterials with biocidal properties has received considerable attention due to their potential applications in various industries, including food, medicine, and cultural heritage preservation. The growing demand for coatings with antibacterial properties has sparked interest from industrial sectors in exploring the incorporation of biocides into these materials. Coatings are prone to microbial growth, which can cause damage such as cracking, discoloration, and staining. To combat these problems, the integration of biocides into coatings is a crucial strategy. Biocide-embedded nanomaterials offer numerous advantages, including high efficiency in small quantities, ease of application, good chemical stability, low toxicity, and non-bioaccumulation. Encapsulated nanobiocides are particularly attractive to the agro-industry, because they can be less toxic than traditional biocides while still effectively controlling microbial contamination. To fully exploit the benefits of nanobiocides, future research should focus on optimizing their synthesis, formulation, and delivery methods. The purpose of this review is to summarize the current status of biocide nanomaterials, discuss potential future research directions, and highlight research methods, the development of new forms of nanomaterials, and studies of their physico-chemical properties. Biocide nanocapsules of DCOIT (4,5-Dichloro-2-octyl-2H-isothiazol-3-one) are chosen as an example to illustrate the research pathways. Full article
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19 pages, 7477 KiB  
Article
Effect of Asphaltenes and Asphaltene Dispersants on Wax Precipitation and Treatment
by Oualid M’barki, John Clements and Quoc P. Nguyen
Colloids Interfaces 2024, 8(3), 30; https://doi.org/10.3390/colloids8030030 - 14 May 2024
Viewed by 589
Abstract
A detailed understanding of the interactions between wax and asphaltenes with other components of crude oils and the effect of treatments with paraffin inhibitors (PIs) and asphaltene dispersants (ADs), with a focus on identifying specific structure-activity relationships, is necessary to develop effective flow [...] Read more.
A detailed understanding of the interactions between wax and asphaltenes with other components of crude oils and the effect of treatments with paraffin inhibitors (PIs) and asphaltene dispersants (ADs), with a focus on identifying specific structure-activity relationships, is necessary to develop effective flow assurance strategies. The morphological and rheological consequences of treating wax and asphaltenes in oils of differing composition with a series of ADs having structural features in common with an alpha olefin-maleic anhydride (AO-MA) comb-like copolymer PI were assessed alone and in combination with said PI. Of the four ADs studied, two were identified as being effective dispersants of asphaltenes in heptane-induced instability tests and in a West Texas (WT) crude. The degree to which a low concentration of asphaltenes stabilizes wax in the absence of treatment additives is lessened in oils having greater aromatic fractions. This is because these stabilizing interactions are replaced by more energetically favorable aromatic–asphaltene interactions, increasing oil viscosity. Treatment with AD alone also reduces the extent of wax–asphaltene interactions, increasing oil viscosity. In concert with the PI, treatment with the AD having greater structural similarity with the PI appears to improve wax solubility in both the presence and absence of asphaltenes. However, the viscosity of the treated oils is greater than that of the oil treated with PI alone, while treatment with AD having lesser structural similarity with the PI does not adversely affect oil viscosity. These data suggest that rather than treating both wax and asphaltenes, AD may poison the function of the PI. These data illuminate the pitfalls of designing flow assurance additives to interact with both wax and asphaltenes and developing treatment plans. Full article
(This article belongs to the Special Issue Crude Oil Recovery)
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15 pages, 3471 KiB  
Article
Vesicle Morphogenesis in Amphiphilic Triblock Copolymer Solutions
by Senyuan Liu, Mohammad Sadegh Samie and Radhakrishna Sureshkumar
Colloids Interfaces 2024, 8(3), 29; https://doi.org/10.3390/colloids8030029 - 6 May 2024
Viewed by 683
Abstract
Coarse-grained molecular dynamics simulations are employed to investigate the spatiotemporal evolution of vesicles (polymersomes) through the self-assembly of randomly distributed amphiphilic BAB triblock copolymers with hydrophilic A and hydrophobic B blocks in an aqueous solution. The vesiculation pathway consists of several intermediate structures, [...] Read more.
Coarse-grained molecular dynamics simulations are employed to investigate the spatiotemporal evolution of vesicles (polymersomes) through the self-assembly of randomly distributed amphiphilic BAB triblock copolymers with hydrophilic A and hydrophobic B blocks in an aqueous solution. The vesiculation pathway consists of several intermediate structures, such as an interconnected network of copolymer aggregates, a cage of cylindrical micelles, and a lamellar cage. The cage-to-vesicle transition occurs at a constant aggregation number and practically eliminates the hydrophobic interfacial area between the B block and solvent. Molecular reorganization underlying the sequence of morphology transitions from a cage-like aggregate to a vesicle is nearly isentropic. The end-to-end distances of isolated copolymer chains in solution and those within a vesicular assembly follow lognormal probability distributions. This can be attributed to the preponderance of folded chain configurations in which the two hydrophobic end groups of a given chain stay close to each other. However, the probability distribution of end-to-end distances is broader for chains within the vesicle as compared with that of a single chain. This is due to the swelling of the folded configurations within the hydrophobic bilayer. Increasing the hydrophobicity of the B block reduces the vesiculation time without qualitatively altering the self-assembly pathway. Full article
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13 pages, 3615 KiB  
Article
Water-Based Bi2S3 Nano-Inks Obtained with Surfactant-Assisted Liquid Phase Exfoliation and Their Direct Processing into Thin Films
by Micaela Pozzati, Felix Boll, Matteo Crisci, Sara Domenici, Francesco Scotognella, Bernd Smarsly, Teresa Gatti and Mengjiao Wang
Colloids Interfaces 2024, 8(3), 28; https://doi.org/10.3390/colloids8030028 - 30 Apr 2024
Viewed by 704
Abstract
Bi2S3 has gained considerable attention as a semiconductor for its versatile functional properties, finding application across various fields, and liquid phase exfoliation (LPE) serves as a straightforward method to produce it in nano-form. Till now, the commonly used solvent for [...] Read more.
Bi2S3 has gained considerable attention as a semiconductor for its versatile functional properties, finding application across various fields, and liquid phase exfoliation (LPE) serves as a straightforward method to produce it in nano-form. Till now, the commonly used solvent for LPE has been N-Methyl-2-pyrrolidone, which is expensive, toxic and has a high boiling point. These limitations drive the search for more sustainable alternatives, with water being a promising option. Nonetheless, surfactants are necessary for LPE in water due to the hydrophobic nature of Bi2S3, and organic molecules with amphoteric characteristics are identified as suitable surfactants. However, systematic studies on the use of ionic surfactants in the LPE of Bi2S3 have remained scarce until now. In this work, we used sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS) and sodium hexadecyl sulfonate (SHS) as representative species and we present a comprehensive investigation into their effects on the LPE of Bi2S3. Through characterizations of the resulting products, we find that all surfactants effectively exfoliate Bi2S3 into few-layer species. Notably, SDBS demonstrates superior stabilization of the 2D layers compared to the other surfactants, while SHS becomes the most promising surfactant for obtaining products with high yield. Moreover, the resulting nano-inks are used for fabricating films using spray-coating, reaching a fine tuning of band gap by controlling the number of cycles, and paving the way for the utilization of 2D Bi2S3 in optoelectronic devices. Full article
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14 pages, 3182 KiB  
Article
Rheological Behaviors and Fractional Viscoelastic Modeling of Glucopone (APG)/Water/Hydrocarbons Solutions
by Mohamed A. Siddig
Colloids Interfaces 2024, 8(3), 27; https://doi.org/10.3390/colloids8030027 - 24 Apr 2024
Viewed by 718
Abstract
The aims of this work are to study the rheological behaviors of a microemulsion of Glucopone–water–hydrocarbon systems and to use a fractional model to describe several experimental results of these systems. Four different types of hydrocarbons were considered. The frequency dependent storage, G [...] Read more.
The aims of this work are to study the rheological behaviors of a microemulsion of Glucopone–water–hydrocarbon systems and to use a fractional model to describe several experimental results of these systems. Four different types of hydrocarbons were considered. The frequency dependent storage, G′, and loss modulus, G″, were investigated below the critical strain. The critical strain was found to decrease as the alkane chain lengths increased, while the opposite behavior was observed for zero shear viscosity, η0. Most of the microemulsions exhibited stable elastic fluid behavior (G′ > G″) below 10 rad s−1 angular frequency. For all systems, elastic modulus values were found to be greater than loss modulus in the frequency range studied, indicating more elastic behaviors. Shear-thinning behaviors were observed, and the complex viscosity decreased with an increase in hydrocarbon chain lengths. The effects of hydrocarbon types on the rheological behaviors were more profound in the dodecane systems which showed maximum values of G′ and η0. The Friedrich–Braun model was introduced and was used to describe several experimental results on Alkyl polyglocoside solutions. Fractional rheology successfully described the viscoelastic phenomena in Glucopone surfactant solutions and the comparisons between the experimental results and the theoretical predictions were found to be satisfactory. Full article
(This article belongs to the Special Issue Rheology of Complex Fluids and Interfaces)
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