Bronsted acidic surfactants: efficient organocatalysts for diverse organic transformations

Organic transformations using efficient, atom-economical, cost-effective and environmentally benign strategies for the construction of diversified molecules have attracted synthetic chemists worldwide in recent years. These processes often minimize the waste production and avoid the use of hazardous flammable organic solvents. Among various green protocols, the procedures using surfactant-based catalytic systems have received a considerable attention in organic synthesis. In this context, Bronsted acidic surfactants have emerged as efficient catalysts for various C–C, C–O, C–N and C–S bond forming reactions. Many of these reactions occur in water, as Bronsted acidic surfactants have a unique ability of creating hydrophobic pocket through micelle formation in aqueous medium and the substrate molecules react efficiently to afford the targeted products in good yields. In the past, Bronsted acidic surfactant combined catalysts successfully displayed their potential to accelerate the reaction rates of diverse organic transformations. This chapter presents a complete overview on Bronsted acidic surfactants catalyzed organic reactions to construct a variety of aromatic and heteroaromatic molecular frameworks.

Oil Red O based method for Exosome Labelling and Detection

With the realization of the role of exosomes in diseases especially cancer, exosome research is gaining popularity in biomedical sciences. To understand exosome biology, their labelling and tracking studies are important. New and improved methods of exosome labelling for detection and tracking of exosomes need to be developed to harness their therapeutic and diagnostic potential. In this paper, we report a novel, simple and effective method of labelling and detecting exosomes using Oil red O (ORO) which is a dye commonly used for lipid staining. Using ORO is a cost effective and easy approach with intense red colouration of stained exosomes. Further, the issues faced with commonly used lipophilic dyes for exosomes labelling such as long term persistence of dyes, aggregation and micelle formation of dyes, difficulty to distinguish dye particles from labelled exosomes and detection of large aggregates of dye or dye-exosome are not seen with ORO dye. This method shows good labelling efficiency of exosomes with very sensitive detection and real-time tracking of the cellular uptake of exosomes.

REVIEW: AN EFFORTS TO INCREASE THE SOLUBILITY AND DISSOLUTION OF ACTIVE PHARMACEUTICAL INGREDIENTS

The most significant aspect of a drug's physicochemical nature is its solubility. If the medicine is in a dissolved form, it can dissolve and enter the membrane, resulting in a therapeutic effect. The pharmacokinetic phase of the drug in the body, which includes absorption, distribution, metabolism, and excretion, will be correlated with solubility. Some medications, however, have a low solubility. To obtain a therapeutic impact, an effort must be made to increase the drug's solubility. Based on the literature research, the goal of this paper is to explain approaches that can be utilized to improve solubility. In general, physical, chemical, and micelle formation efforts can all be used it to enhance solubility. Particle size reduction, crystal shape modification, and the utilization of matrices in the disperse phase are examples of physical alterations. pH adjustment, buffering, salt formation, complexation, and derivatization all are examples of chemical alterations. The employment of supercritical processes in solutions and also excipients such as surfactants, cosolvents, stabilizing solutions, and others are examples of how micelle formation can be modified.

Surface Activity and Efficiency of Cat-Anionic Surfactant Mixtures

The surface activity of surfactant mixtures is critically analyzed. Cat-anionic systems, in which two ionic species are mixed in non-stoichiometric ratios, are considered. With respect to the solution behavior, where a substantial decrease of cmc is met compared to the pure components, a moderate effect on surface tension, γ, occurs. Compared to the pure species, the decrease of surface tension for such mixtures is not significant, and no clear dependence on the mole fraction anionic/cationic is met. The surface tension is grossly constant in the whole concentration range. Conversely, the interaction parameter for surfaces, βsurf (calculated by the regular solution theory), is more negative than that for micelle formation, βmic. This fact suggests that the desolvation of polar heads of the two species at interfaces is largely different. Very presumably, the underlying rationale finds origin in the sizes and solvation of both polar head groups.

SYNTHESIS AND PROPERTIES OF MODIFIED XANTHAN GUM

Xanthan gum is widely used as a stabilizing, emulsifying, thickening agent in pharmacology, medicine, food, oil, paint, textile, perfume, mining and agriculture. For food purposes, potassium, sodium or calcium salts of xanthan formed by carboxyl groups of glucuronic acid and pyruvate group are used. Currently, xanthan gum is not produced on an industrial scale in Russia. There are repeated attempts to create industries in various regions of the country. The paper synthesizes hydrophobized acetylated xanthan gum derivatives with different degrees of substitution. Physical-chemical and colloidal-chemical properties of initial and modified gum are compared by methods of viscosimetry, tensiometry, IR spectroscopy. The point of zero charge of xanthan gum is determined.. Change of macromolecule conformation depending on pH of aqueous solution and preliminary dewatering is shown. Delamination temperatures of initial and modified forms of xanthan gum were determined. The critical micelle formation concentration of the modified gum is 0.2%. At this concentration, the surface activity of the gum is 6.1 and 7.9 mJ m/kg when replacing two and five hydroxo groups, respectively. The possibility of using modified xanthan gum as a binder for obtaining fuel pellets with improved operational properties and calorific value is shown.

Detailed Calorimetric Analysis of Mixed Micelle Formation from Aqueous Binary Surfactants for Design of Nanoscale Drug Carriers

While numerous papers have been published according to the binary surfactant mixtures, only a few articles provide deeper information on the composition dependence of the micellization, and even less work attempts to apply the enhanced feature of the mixed micelles. The most important parameter of the self-assembled surfactants is the critical micelle concentration (cmc), which quantifies the tendency to associate, and provides the Gibbs energy of micellization. Several techniques are known for determining the cmc, but the isothermal titration calorimetry (ITC) can be used to measure both cmc and enthalpy change (ΔmicH) accompanying micelle formation. Outcomes of our calorimetric investigations were evaluated using a self-developed routine for handling ITC data and the thermodynamic parameters of mixed micelle formation were obtained from the nonlinear modelling of temperature- and composition- dependent enthalpograms. In the investigated temperature and micelle mole fractions interval, we observed some intervals where the cmc is lower than the ideal mixing model predicted value. These equimolar binary surfactant mixtures showed higher solubilization ability for poorly water-soluble model drugs than their individual compounds. Thus, the rapid and fairly accurate calorimetric analysis of mixed micelles can lead to the successful design of a nanoscale drug carrier.

Aiming to the superior of phosphor pattern: Influence of SiO2 nanoparticles on photoluminescence intensification of YAG:Ce

<span lang="EN-US">Yttrium aluminum garnet (YAG: RE) rare-earth-doped phosphors have great photoluminescence (PL) characteristics and are commonly used in light-emitting rectifying tubes. The RE elements used in these phosphors, however, are precious and in shortage. The production of phosphorus containing a limited amount of RE content is therefore essential. One solution is to manufacture Nano composite phosphors that use an inexpensive and more easily available content as a matrix for RE oxide. In this research, we developed a YAG: Ce/SiO2 Nano composite using a sol-gel procedure; in order to impulse micelle formation and agglomeration, poly (ethylene glycol) and urea have been added, respectively. X-ray diffraction, scanning and transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy were used to characterize the Nano composites. In proposing an explanation for this enhancement, we defined the concentration of SiO2 that produced optimum PL enhancement and used geometric models as well as the characterization consequences. Our results demonstrated that a 10% SiO2 concentration produced a 120% PL intensity of pure YAG:Ce. TEM analysis revealed that SiO2 nanoparticles filled the voids between the YAG:Ce crystals' single grain borders, hence inhibiting light scattering, resulting in increased PL. This procedure would be beneficial for the synthesis of low-RE and high-PL phosphors on a wide scale.</span>

Analysis of Micelle Formation and Adsorption Layers of Binary Mixtures of Sulphate Soap Components

Currently, the main trend of the pulp and paper industry development is bio-refining. It is based on integrated and deep processing of wood raw materials to obtain products with higher value added and reduced amount of waste. One of the high priority tasks of bio-refining is improvement of technology of by-product (sulphate soap) extraction from spent liquor with an increase in the yield and quality of the resulting product and a decrease in the level of environmental pollution. The complexity and energy intensity of sulphate soap extraction from spent liquor depends on many factors, including the species used for wood cooking, composition of extractives, the method of wood preparation for delignification, etc. Sulphate soap is a multicomponent emulsion with a predominant content of resin and fatty acids, small amount of unsaponifiable substances and an admixture of lignin, which is mainly extracted from waste liquior by settling. The low degree of its extraction is associated with the absence of systematical data on the mutual influence of the sulphate soap components. In this work, the patterns of intermolecular interaction of the individual components of the by-product (sulphate soap) are found. For this purposes the critical concentration of micelle formation (CCM) and surface tension depression of surface-active sodium oleate and sodium abietate and their mixtures of varying compositions were determined by the methods of tensiometry and conductometry. A detailed analysis of its mixed micelles and adsorption layers was carried out using the Rubin–Rosen pseudophase model. The interaction mechanisms of components in mixtures are explained. The impact on the composition of micelles and adsorption layers of the more surface-active sodium oleate was detected in mixed solutions. A maximum synergistic effect of micelle formation was observed in mixtures with a predominant content of sodium abietate. Analysis of experimental data and the result of sulphate soap modeling allow substantiating the complexity of its extraction from waste liquor after wood cooking with the presence of hardwood over 30 %, which is explained by the reduced content of resin acids in black liquor. For citation: Yakubova O.S., Demiantseva E.Yu., Smit R.A., Dubovy V.K. Analysis of Micelle Formation and Adsorption Layers of Binary Mixtures of Sulphate Soap Components. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 6, pp. 196–205. DOI: 10.37482/0536-1036-2021-6-196-205

Impacts of polyols and temperature on the micellization, interaction and thermodynamics behavior of the mixture of tetradecyltrimethylammonium bromide and polyvinyl alcohol

Herein, the aggregation manner of the mixture of polyvinyl alcohol (PVA) and tetradecyltrimethylammonium bromide (TTAB) was performed in polyols (glucose, maltose and galactose) media over 300.55–320.55 K temperatures range with 5 K interval through conductivity measurement method. The micelle formation of TTAB + PVA mixture was identified by the assessment of critical micelle concentration (CMC) from the plots of specific conductivity (κ) versus TTAB concentration. The degree of micelle ionization (α), the extent of bound counter ions (β) as well as thermodynamic properties ( Δ G m 0 ${\Delta}{G}_{m}^{0}$ , Δ H m 0 ${\Delta}{H}_{m}^{0}$ and Δ S m 0 ${\Delta}{S}_{m}^{0}$ ) of TTAB + PVA systems have been estimated. The CMC values reveal that the micelle formation of TTAB + PVA mixture experience an enhancement in the manifestation of polyols. The values of free energy of micellization ( Δ G m 0 ${\Delta}{G}_{m}^{0}$ ) are negative for the TTAB + PVA system in aqueous polyols media, suggesting a spontaneous aggregation phenomenon. The Δ H m 0 ${\Delta}{H}_{m}^{0}$ and Δ S m 0 ${\Delta}{S}_{m}^{0}$ values of TTAB + PVA systems direct that the PVA molecule interacts with TTAB through the exothermic, ion-dipole, and hydrophobic interactions. The thermodynamic properties of transfer were also determined for the move of TTAB + PVA mixture from H2O to water + polyols mixed solvents. The values of compensation temperature (T c) and intrinsic enthalpy gain ( Δ H m 0 , ∗ ${\Delta}{H}_{m}^{0,\ast }$ ) were evaluated and discussed for the studied system.