Intermicellar interaction in surfactant solutions; a review study

Linear-Organic-Ions In Situ-Intercalated MoS2 for Unveiling Capacitive Energy Storage Relies on the Chain Length

Intercalating linear-organic-ions into the MoS2 interlayer is beneficial for optimizing electrons/ions' capacitive storage behavior. The chain length, as an important parameter of linear organic ions, can lead to differences in the dispersion, polarity, critical micelle concentration of organic ions, and steric hindrance to the growth of MoS2 nanosheets. Up until now, the relationship between chain length, synthesis of intercalated-MoS2, and capacitive energy storage has not been unveiled. Herein, we have designed an in situ-intercalation route that is simple, efficient, and high yield for inserting four types of linear organic ions into the interlayer of MoS2 to synthesize four types of in situ-intercalated MoS2 samples. After organic-ion intercalation, the expanded interlayer spacing achieved the introduction of intercalation-type pseudocapacitors, as confirmed by ex situ XRD. Improved extra capacitance is verified due to the enlarged ion storage space from a synergistic spatial effect in the broken-shell-hollow ball. Additionally, the generation of high-valent Mo (+5 and +6) and S-vacancies is beneficial for energy storage. More importantly, according to density functional theory (DFT) calculations, as the chain length increases, the number of negative adsorption sites and the total adsorption ability also increase, leading to significantly improved specific capacitance. This work will provide an archetype for the preparation of in situ-intercalated layered materials and unveil capacitive energy storage that relies on the organic-ion chain length.

High-Performance Aluminum Fuels Induced by Monolayer Self-Assembly of Nano-Sized Energetic Fluoride Vesicles on the Surface

Surface modification is frequently used to solve the problems of low combustion properties and agglomeration for aluminum-based fuels. However, due to the intrinsic incompatibility between the aluminum powder and the organic modifiers, the surface coating is usually uneven and disordered, which significantly deteriorates the uniformity and performances of the Al-based fuels. Herein, a new approach of monolayer nano-vesicular self-assembly is proposed to prepare high-performance Al fuels. Triblock copolymer G-F-G is produced by glycidyl azide polymer (GAP) and 2,2'-(2,2,3,3,4,5,5-Octafluorohexane-1,6-diyl) bis (oxirane) (fluoride) ring-open addition reaction. By utilizing G-F-G vesicular self-assembly in a special solvent, the nano-sized vesicles are firmly adhered to the surface of Al powder through the long-range attraction between the fluorine segments and Al. Meanwhile, the electrostatic repulsion between vesicles ensures an extremely thin coating thickness (≈15 nm), maintaining the monolayer coating structure. Nice ignition, combustion, anti-agglomeration, and water-proof properties of Al@G-F-G(DMF) are achieved, which are superior among the existing Al-based fuels. The derived Al-based fuel has excellent comprehensive properties, which can not only inspire the development of new-generation energetic materials but also provide facile but exquisite strategies for exquisite surface nanostructure construction via ordered self-assembly for many other applications.

Surfactant-mediated bio-manufacture: A unique strategy for promoting microbial biochemicals production

Biochemicals are widely used in the medicine and food industries and are more efficient and safer than synthetic chemicals. The amphipathic surfactants can interact with the microorganisms and embed the extracellular metabolites, which induce microbial metabolites secretion and biosynthesis, performing an attractive prospect of promoting the biochemical production. However, the commonness and differences of surfactant-mediated bio-manufacture in various fields are largely unexplored. Accordingly, this review comprehensively summarized the properties of surfactants, different application scenarios of surfactant-meditated bio-manufacture, and the mechanism of surfactants increasing metabolites production. Various biochemical productions such as pigments, amino acids, and alcohols could be enhanced using the cloud point and the micelles of surfactants. Besides, the amphiphilicity of surfactants also promoted the utilization of fermentation substrates, especially lignocellulose and waste sludge, by microorganisms, indirectly increasing the metabolites production. The increase in target metabolites production was attributed to the surfactants changing the permeability and composition of the cell membrane, hence improving the secretion ability of microorganisms. Moreover, surfactants could regulate the energy metabolism, the redox state and metabolic flow in microorganisms, which induced target metabolites synthesis. This review aimed to broaden the application fields of surfactants and provide novel insights into the production of microbial biochemicals.

Recent advances in understanding the interfacial activity of antioxidants in association colloids in bulk oil

The chemical stability of edible oils rich in polyunsaturated fatty acids (PUFAs) is a major challenge within the food and supplement industries, as lipid oxidation reduces oil quality and safety. Despite appearing homogeneous to the human eye, bulk oils are actually multiphase heterogeneous systems at the nanoscale level. Association colloids, such as reverse micelles, are spontaneously formed within bulk oils due to the self-assembly of amphiphilic molecules that are present, like phospholipids, free fatty acids, and/or surfactants. In bulk oil, lipid oxidation often occurs at the oil-water interface of these association colloids because this is where different reactants accumulate, such as PUFAs, hydroperoxides, transition metals, and antioxidants. Consequently, the efficiency of antioxidants in bulk oils is governed by their chemical reactivity, but also by their ability to be located close to the site of oxidation. This review describes the impact of minor constituents in bulk oils on the nature of the association colloids formed. And then the formation of mixed reverse micelles (LOOH, (co)surfactants, or antioxidations) during the peroxidation of bulk oils, as well as changes in their composition and structure over time are also discussed. The critical importance of selecting appropriate antioxidants and surfactants for the changes of interface and colloid, as well as the inhibition of lipid oxidation is emphasized. The knowledge presented in this review article may facilitate the design of bulk oil products with improved resistance to oxidation, thereby reducing food waste and improving food quality and safety.

Gemini and Bicephalous Surfactants: A Review on Their Synthesis, Micelle Formation, and Uses

The use of surfactants in polymerization reactions is particularly important, mainly in emulsion polymerizations. Further, micelles from biocompatible surfactants find use in pharmaceutical dosage forms. This paper reviews recent developments in the synthesis of novel gemini and bicephalous surfactants, micelle formation, and their applications in polymer and nanoparticle synthesis, oil recovery, catalysis, corrosion, protein binding, and biomedical area, particularly in drug delivery.

Enhanced water-resistant performance of Cu-BTC through polyvinylpyrrolidone protection and its capture ability evaluation of methylene blue

Water instability issues greatly restrict the application of Cu-BTC for cationic dye (e.g. methylene blue (MB)) capture from wastewater.

Prediction of Aqueous Solution Surface Tension of Some Surfactant Mixtures and Composition of Their Monolayers at the Solution—Air Interface

Measurements of the surface tension of the aqueous solution of SDDS mixture with fluorocarbon surfactants (FC) were carried out and considered in light of the surface tension of aqueous solutions of individual surfactants. Similar analyses were made for many other aqueous solutions of binary and ternary mixtures, taking into account the literature data of the surface tension of aqueous solutions of TX100, TX114, TX165, SDDS, SDS, CTAB, CPyB and FC. The possibility of predicting the surface tension of the aqueous solution of many surfactant mixtures from that of the mixture components using both the Szyszkowski, Fainerman and Miller and Joos concepts was analyzed. The surface tension of the aqueous solutions of surfactant mixtures was also considered based on the particular mixture component contribution to the water surface tension reduction. As a result, the composition of the mixed surface layer at the solution–air interface was discussed and compared to that which was determined using the Hua and Rosen concept. As follows from considerations, the surface tension of the aqueous solution of binary and ternary surfactant mixtures can be described and/or predicted.

Self-Assembling Drug Formulations with Tunable Permeability and Biodegradability

This review focuses on key topics in the field of drug delivery related to the design of nanocarriers answering the biomedicine criteria, including biocompatibility, biodegradability, low toxicity, and the ability to overcome biological barriers. For these reasons, much attention is paid to the amphiphile-based carriers composed of natural building blocks, lipids, and their structural analogues and synthetic surfactants that are capable of self-assembly with the formation of a variety of supramolecular aggregates. The latter are dynamic structures that can be used as nanocontainers for hydrophobic drugs to increase their solubility and bioavailability. In this section, biodegradable cationic surfactants bearing cleavable fragments are discussed, with ester- and carbamate-containing analogs, as well as amino acid derivatives received special attention. Drug delivery through the biological barriers is a challenging task, which is highlighted by the example of transdermal method of drug administration. In this paper, nonionic surfactants are primarily discussed, including their application for the fabrication of nanocarriers, their surfactant-skin interactions, the mechanisms of modulating their permeability, and the factors controlling drug encapsulation, release, and targeted delivery. Different types of nanocarriers are covered, including niosomes, transfersomes, invasomes and chitosomes, with their morphological specificity, beneficial characteristics and limitations discussed.

A review of the role and mechanism of surfactants in the morphology control of metal nanoparticles

Although great progress has been made in the synthesis of metal nanoparticles, good repeatability and accurate predictability are still difficult to achieve. This difficulty can be attributed to the synthetic method based primarily on observation and subjective experience, and the role of many surfactants remains unclear. It should be noted that surfactants play an important role in the synthetic process. Understanding their function and mechanism in the synthetic process is a prerequisite for the rational design of nanocatalysts with ideal morphology and performance. In this review article, the function of surfactants is introduced first, and then the mechanism of action of surfactants in controlling the morphology of nanoparticles is discussed according to the types of surfactants, and the promoting and sealing effects of surfactants on the crystal surface is revealed. The relationship between surfactants and the morphology structure of nanoparticles is studied. The removal methods of surfactants are discussed, and the existing problems in the current development strategy are summarized. Finally, the application of surfactants in controlling the morphology of metal nanocrystals is prospected. It is hoped that the review can open up new avenues for the synthesis of nanocrystals.

Liquid Crystalline Phases for Enhancement of Oral Bioavailability

Liquid crystalline phases (LCPs) are generated upon lipolysis of ingested lipids in the gastrointestinal tract. The breaking off and subsequent evolution of LCPs produce more advanced vesicular and micellar structures which facilitate oral absorption of lipids, as well as co-loaded drug entities. Owing to sustained or controlled drug release, bioadhesiveness, and capability of loading drugs of different properties, LCPs are promising vehicles to implement for enhancement of oral bioavailability. This review aims to provide an overview on the classification, preparation and characterization, in vivo generation and transformation, absorption mechanisms, and encouraging applications of LCPs in enhancement of oral bioavailability. In addition, we comment on the merits of LCPs as oral drug delivery carriers, as well as solutions to industrialization utilizing liquid crystalline precursor and preconcentrate formulations.

Controllable enzymatic superactivity of α-chymotrypsin activated by the electrostatic interaction with cationic gemini surfactants

Surfactant plays a critical role in enzymatic multi-functionalization processes. However, a deep understanding of surfactant-enzyme interactions has been lacking up until now due to the extreme complexity of the mixed system. This work reported the effect of cationic gemini surfactants, alkanediyl-α,ω-bis(dimethyldodecylammonium bromide) (C12C S C12Br2, S = 2, 6, and 10) on the enzymatic activity and conformation of α-chymotrypsin (α-CT) in phosphate buffer solution (PBS, pH 7.3). The enzymatic activity was assessed by the rate of 2-naphthyl acetate (2-NA) hydrolysis measured by UV-vis absorption. The superactivity of α-CT in the presence of C12C S C12Br2 appears in the concentration region below the critical micelle concentration (cmc) of the surfactant, and its maximum superactivity is correlated to the spacer length of C12C S C12Br2. Subtle regulation of the charge density of headgroups of the cationic surfactant can be achieved through partial charge neutralization of cationic headgroups by introducing inorganic counterions or oppositely charged surfactant, demonstrating that the electrostatic interaction plays the crucial role for emergence of the superactivity. The interaction between C12C S C12Br2 (S = 2,6, and 10) and α-CT was characterized by isothermal titration calorimetry (ITC), and the obtained endothermic enthalpy change indicates that the interaction induces the change in conformation and enzymatic superactivity. The methodologies of fluorescence spectroscopy, circular dichroism (CD), and differential scanning calorimetry (DSC) show that the gemini surfactants with different spacer lengths induct and regulate the secondary, tertiary and even fourth structures of the protein. The present work is significant to get deeper insight into the mechanism of the activation and denaturation of enzymes.

Co-solvent Effect on Spontaneous Formation of Large Nanoscale Structures in Catanionic Mixtures in the Anionic-Rich Region

The aggregation behavior was investigated in mixtures of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) (anionic-rich catanionic) solutions. The study was conducted in solutions of water–ethylene glycol (EG) by means of surface tension, conductometry, cyclic voltammetry, zeta potential measurements, transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. The degree of counterion dissociation (α), critical micelle concentration, aggregation numbers, interfacial properties, interparticle interaction parameters, and morphology of aggregates were determined. Based on regular solution theory, the cosolvent effects between SDS and CTAB as surfactants were also analyzed for both mixed monolayers at mixed micelles (βM) and the air/liquid interface (βσ). It was shown that the formation of large aggregates occurred in the presence of an excess of anionic surfactant. A phase transition from cylindrical micelles to spherical micelles in the anionic-rich regime was observed with an increase in the EG volume fraction. The inter particle interactions were assessed in terms of cosolvent effects on the micellar surface charge density and the cylindrical-to-spherical morphology change. Zeta potential and size of the aggregates were determined using dynamic light scattering and confirmed the models suggested for the processes taking place in each system.

Clear distinction between CAC and CMC revealed by high-resolution NMR diffusometry for a series of bis-imidazolium gemini surfactants in aqueous solutions

The aggregation behavior in the transition region was studied for a series of dicationic surfactants 3,3′-[α,ω-(dioxaalkane)]bis(1-dodecylimidazolium)dichlorides with varied spacer length from two to twelve carbon atoms. We employed Nuclear Magnetic Resonance diffusometry and Bayesian DOSY analysis to obtain the aggregate size distribution in the transition region. The critical concentrations CC were independently obtained from surface tension, electric conductivity, UV-Vis and NMR methods. The micelle aggregation numbers were estimated from the self-diffusion coefficients and were independently confirmed using steady-state fluorescence quenching. The morphology of the aggregates was characterized by small-angle scattering of synchrotron radiation and molecular dynamics simulations. The obtained CC values are identified as critical aggregation concentrations CAC. A broad transition region was observed, and stable micelles were obtained at much higher concentrations than CAC. The accurate CMC values could not be identified for the systems in the study. We indicated that the distribution of aggregate size becomes small and the system becomes homogeneous at much larger concentrations than CAC (typically 15–20 mM). The existence of a slow exchange between two environments, an aggregate and aqueous environment, was confirmed by ¹H NMR and 2D HSQC NMR spectroscopy.

The aggregation behavior in the transition region was studied for a series of dicationic surfactants 3,3′-[α,ω-(dioxaalkane)]bis(1-dodecylimidazolium)dichlorides with varied spacer length from two to twelve carbon atoms.