SciCombinator

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Concept: Surfactant

160

Dimeric quaternary alkylammonium salts possess a favourable surface and antimicrobial activity. In this paper we describe synthesis, spectroscopic analysis, surface and antimicrobial activity as well as biodegradability of polymethylene-α,ω-bis(N,N-dialkyl-N-deoxy-D-glucitolammonium iodides), a new group of dimeric quaternary ammonium salts. This new group of gemini surfactants can be produced from chemicals which come from renewable sources. The structure of products has been determined by the FTIR and (1)H and (13)C NMR spectroscopy. The biodegradability, surface activity and antimicrobial efficacy against Escherichia coli, Staphylococcus aureus, Candida albicans, Aspergillus niger and Penicillium chrysogenum were determined. The influence of the number of alkyl chains and their lengths on surface and antimicrobial properties has been shown. In general, dimeric quaternary alkyldeoxy-D-glucitolammonium salts with long alkyl substituents show favourable surface properties and an excellent antimicrobial activity.

Concepts: Spectroscopy, Surfactant, Quaternary ammonium cation, Ammonium, Ascomycota, Salt, Cocamidopropyl betaine, Fabric softener

146

In this paper, the extracts of three-part beggarticks (Bidens tripartita) were prepared using ultrasonic assisted micelle-mediated extraction method (UAMME). Different kind of surfactants and WPC (whey protein concentrate) were applied. In the B. tripartita extracts twenty polyphenols were identified by UPLC-DAD-MS. Both aqueous and UAMME extracts mainly contained chlorogenic acid, caftaric acid and its derivatives as well as luteolin 7-O-glucoside. The luteolin was extracted with Rokanol B2 and Triton X-100. Furthermore, antioxidative properties of the extracts were analyzed with two methods: reactions with di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) reagent and Follin’s method. The DPPH radical scavenging by micellar extracts was in general comparable with the antioxidant activity of conventional extracts. The most active was sample with Tego Care CG90, reducing about 73% of the radical. Obtained results confirmed that the UAMME might be an alternative method, to the liquid-liquid or solid-liquid extraction, of obtaining specified extracts rich in active compounds. Selecting a suitable surfactant may thus provide the expected composition of the extract.

Concepts: Antioxidant, Whey protein, Coffee, Surfactant, Micelle, Extraction, Bidens, Bidens tripartita

142

A new desorption method was investigated, which does not require toxic organic solvents. Efficient desorption of organic solvents from activated carbon was achieved with an ananionic surfactant solution, focusing on its washing and emulsion action.

Concepts: Oxygen, Solubility, Carbon, Solvent, Surfactant, Solutions, Solution, Activated carbon

75

Here, we present a comprehensive approach for creating robust, elastic, designer Lunar and Martian regolith simulant (LRS and MRS, respectively) architectures using ambient condition, extrusion-based 3D-printing of regolith simulant inks. The LRS and MRS powders are characterized by distinct, highly inhomogeneous morphologies and sizes, where LRS powder particles are highly irregular and jagged and MRS powder particles are rough, but primarily rounded. The inks are synthesized via simple mixing of evaporant, surfactant, and plasticizer solvents, polylactic-co-glycolic acid (30% by solids volume), and regolith simulant powders (70% by solids volume). Both LRS and MRS inks exhibit similar rheological and 3D-printing characteristics, and can be 3D-printed at linear deposition rates of 1-150 mm/s using 300 μm to 1.4 cm-diameter nozzles. The resulting LRS and MRS 3D-printed materials exhibit similar, but distinct internal and external microstructures and material porosity (~20-40%). These microstructures contribute to the rubber-like quasi-static and cyclic mechanical properties of both materials, with young’s moduli ranging from 1.8 to 13.2 MPa and extension to failure exceeding 250% over a range of strain rates (10(-1)-10(2) min(-1)). Finally, we discuss the potential for LRS and MRS ink components to be reclaimed and recycled, as well as be synthesized in resource-limited, extraterrestrial environments.

Concepts: Mars, Materials science, Surfactant, Pascal, Ink, Young's modulus, Powder, Life on Mars

40

Nanoscale emulsions are essential components in numerous products, ranging from processed foods to novel drug delivery systems. Existing emulsification methods rely either on the breakup of larger droplets or solvent exchange/inversion. Here we report a simple, scalable method of creating nanoscale water-in-oil emulsions by condensing water vapor onto a subcooled oil-surfactant solution. Our technique enables a bottom-up approach to forming small-scale emulsions. Nanoscale water droplets nucleate at the oil/air interface and spontaneously disperse within the oil, due to the spreading dynamics of oil on water. Oil-soluble surfactants stabilize the resulting emulsions. We find that the oil-surfactant concentration controls the spreading behavior of oil on water, as well as the peak size, polydispersity, and stability of the resulting emulsions. Using condensation, we form emulsions with peak radii around 100 nm and polydispersities around 10%. This emulsion formation technique may open different routes to creating emulsions, colloidal systems, and emulsion-based materials.

Concepts: Water, Colloid, Liquid, Surface tension, Emulsion, Surfactant, Solution, Vapor

31

Janus emulsion assays that rely on carbohydrate-lectin binding for the detection of Escherichia coli bacteria are described. Surfactants containing mannose are self-assembled at the surface of Janus droplets to produce particles with lectin binding sites. Janus droplets orient in a vertical direction as a result of the difference in densities between the hydrocarbon and fluorocarbon solvents. Binding of lectin to mannose(s) causes agglutination and a tilted geometry. The distinct optical difference between naturally aligned and agglutinated Janus droplets produces signals that can be detected quantitatively. The Janus emulsion assay sensitively and selectively binds to E. coli at 10(4) cfu/mL and can be easily prepared with long-time stability. It provides the basis for the development of inexpensive portable devices for fast, on-site pathogen detection.

Concepts: Bacteria, Gut flora, Escherichia coli, Liquid, Surface tension, Emulsion, Proteobacteria, Surfactant

30

The nature of interfacial water is critical in several natural processes, including the aggregation of lipids into the bilayer, protein folding, lubrication of synovial joints, and underwater gecko adhesion. The nanometer-thin water layer trapped between two surfaces has been identified to have properties that are very different from those of bulk water, but the molecular cause of such discrepancy is often undetermined. Using surface-sensitive sum frequency generation (SFG) spectroscopy, we discover a strongly coordinated water layer confined between two charged surfaces, formed by the adsorption of a cationic surfactant on the hydrophobic surfaces. By varying the adsorbed surfactant coverage and hence the surface charge density, we observe a progressively evolving water structure that minimizes the sliding friction only beyond the surfactant concentration needed for monolayer formation. At complete surfactant coverage, the strongly coordinated confined water results in hydration forces, sustains confinement and sliding pressures, and reduces dynamic friction. Observing SFG signals requires breakdown in centrosymmetry, and the SFG signal from two oppositely oriented surfactant monolayers cancels out due to symmetry. Surprisingly, we observe the SFG signal for the water confined between the two charged surfactant monolayers, suggesting that this interfacial water layer is noncentrosymmetric. The structure of molecules under confinement and its macroscopic manifestation on adhesion and friction have significance in many complicated interfacial processes prevalent in biology, chemistry, and engineering.

Concepts: Electric charge, Fundamental physics concepts, Density, Water, Surfactant, Nature, Friction, Tribology

28

In this study, the degradation of tetradecyltrimethylammonium bromide (TTAB) by freely suspended and alginate-entrapped cells from the bacteria Pseudomonas putida (P. putida) A ATCC 12633 was investigated in batch cultures. The optimal conditions to prepare beads for achieving a higher TTAB degradation rate were investigated by changing the concentration of sodium alginate, pH, temperature, agitation rate and initial concentration of TTAB. The results show that the optimal embedding conditions of calcium alginate beads are 4 % w/v of sodium alginate content and 2 × 10(8) cfu ml(-1) of P. putida A ATCC 12633 cells that had been previously grown in rich medium. The optimal degradation process was carried out in pH 7.4 buffered medium at 30 °C on a rotary shaker at 100 rpm. After 48 h of incubation, the free cells degraded 26 mg l(-1) of TTAB from an initial concentration of 50 mg l(-1) TTAB. When the initial TTAB concentration was increased to 100 mg l(-1), the free cells lost their degrading activity and were no longer viable. In contrast, when the cells were immobilized on alginate, they degraded 75 % of the TTAB after 24 h of incubation from an initial concentration of 330 mg l(-1) of TTAB. The immobilized cells can be stored at 4 °C for 25 days without loss of viability and can be reused without losing degrading capacity for three cycles.

Concepts: Cell wall, Pseudomonas, Surfactant, Seawater, Solution, Pseudomonadales, Pseudomonadaceae, Pseudomonas putida

28

A model for the limiting surface tension of surfactant solutions (surface tension at and above the critical micelle concentration, cmc) was developed. This model takes advantage of the equilibrium between the surfactant molecules on the liquid/vacuum surface and in micelles in the bulk at the cmc. An approximate analytical equation for the surface tension at the cmc was obtained. The derived equation contains two parameters, which characterize the intermolecular interactions in the micelles, and the third parameter, which is the surface area per surfactant molecule at the interface. These parameters were calculated using a new atomistic modeling approach. The performed calculations of the limiting surface tension for four simple surfactants show good agreement with experimental data (∼30% accuracy). The developed model provides the guidance for design of surfactants with low surface tension values.

Concepts: Chemistry, Surface tension, Surfactant, Micelle, Quaternary ammonium cation, Solution, Macromolecule, Colloidal chemistry

28

The structure of solubilized water in water-in-n-heptane aggregates stabilized by mixtures of single- and double-tail quaternary ammonium surfactants, namely didodecyldimethylammonium chloride/dodecyltrimethylammonium chloride (DDAC/DTAC) or didodecyldimethylammonium bromide/dodecyltrimethylammonium bromide (DDAB/DTAB) was studied by two noninvasive techniques, (1)H NMR and FT-IR. In the former, the chemical shift data, δ(obs), were used to calculate the so-called deuterium/protium fractionation factor, φ(M), of the aggregate-solubilized water and were found to be unity. In the FT-IR study, upon increasing water/surfactant molar ratio, W, the frequency, ν(OD), of the HOD species decreases, while its full width at half height and its area increase. The results obtained from both techniques indicate that the water appears to be present as a single nano-phase and the structure varies continuously as a result of increasing W. In addition, the effect of changing the counter-ion (Br(-) or Cl(-)) on (1)H NMR and FT-IR results was investigated. In spite of the known difference in the dissociation of these counter-ions from micellar aggregates, this was found not to affect the state of solubilized water. This report gives further insight into the contradictory scientific debates on the structure of water in the polar nano-cores of microemulsions.

Concepts: Nuclear magnetic resonance, Addition, Emulsion, Surfactant, Micelle, Quaternary ammonium cation, Cocamidopropyl betaine, Fabric softener