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Sample records for acid-based cationic surfactants

  1. Spectral and Acid-Base Properties of Hydroxyflavones in Micellar Solutions of Cationic Surfactants

    NASA Astrophysics Data System (ADS)

    Lipkovska, N. A.; Barvinchenko, V. N.; Fedyanina, T. V.; Rugal', A. A.

    2014-09-01

    It has been shown that the spectral characteristics (intensity, position of the absorption band) and the acid-base properties in a series of structurally similar hydroxyflavones depend on the concentration of the cationic surfactants miramistin and decamethoxin in aqueous solutions, and the extent of their changes is more pronounced for hydrophobic quercetin than for hydrophilic rutin. For the first time, we have determined the apparent dissociation constants of quercetin and rutin in solutions of these cationic surfactants (pKa1) over a broad concentration range and we have established that they decrease in the series water-decamethoxin-miramistin.

  2. Biological and surface-active properties of double-chain cationic amino acid-based surfactants.

    PubMed

    Greber, Katarzyna E; Dawgul, Małgorzata; Kamysz, Wojciech; Sawicki, Wiesław; Łukasiak, Jerzy

    2014-08-01

    Cationic amino acid-based surfactants were synthesized via solid phase peptide synthesis and terminal acylation of their α and ε positions with saturated fatty acids. Five new lipopeptides, N-α-acyl-N-ε-acyl lysine analogues, were obtained. Minimum inhibitory concentration and minimum bactericidal (fungicidal) concentration were determined on reference strains of bacteria and fungi to evaluate the antimicrobial activity of the lipopeptides. Toxicity to eukaryotic cells was examined via determination of the haemolytic activities. The surface-active properties of these compounds were evaluated by measuring the surface tension and formation of micelles as a function of concentration in aqueous solution. The cationic surfactants demonstrated diverse antibacterial activities dependent on the length of the fatty acid chain. Gram-negative bacteria and fungi showed a higher resistance than Gram-positive bacterial strains. It was found that the haemolytic activities were also chain length-dependent values. The surface-active properties showed a linear correlation between the alkyl chain length and the critical micelle concentration.

  3. Formation of wormlike micelle in a mixed amino-acid based anionic surfactant and cationic surfactant systems.

    PubMed

    Shrestha, Rekha Goswami; Shrestha, Lok Kumar; Aramaki, Kenji

    2007-07-01

    Formation of wormlike micelles in mixed anionic/cationic system without the addition of any salt has been studied. Amino-acid based anionic surfactant N-dodecylglutamic acid (LAD), which is practically immiscible with water at 25 degrees C upon neutralization by 2,2',2''-nitrilotriethanol (TEA) forms small micellar aggregates and the solution behaves like a Newtonian fluid. The rheological behavior of LAD/water/hexadecyltrimethylammonium bromide (CTAB) and LAD/water/dodecyltrimethylammonium bromide (DTAB) systems were investigated at different degrees of neutralization of the LAD depending on the concentration of the cationic surfactants and on temperature. Addition of CTAB to the dilute aqueous solution of the LAD-TEA-x (the neutralized product, where x represents the mole ratio of TEA) causes one dimensional micellar growth. After certain concentration the elongated micelles entangle forming a rigid network of viscoelastic wormlike micelles. Thus formed viscoelastic solutions follow Maxwellian behavior over a wide range of frequency and thus are considered to consist of transient network of wormlike micelles. By varying the degree of neutralization from 1:1 via 1:1.5 to 1:2 (molar ratio) phase and rheological behavior were modified in that the highly viscous region of viscoelastic wormlike micelles shifted to higher CTAB concentrations and no maxima in the zero-shear viscosity could be observed for the higher degree of neutralization of the LAD (1:1.5 and 1:2). However, the obtained rheological parameters showed scaling relationships that were consistent with the living polymer model. The zero-shear viscosity decays exponentially with temperature following Arrhenius behavior. The flow activation energy calculated from the Arrhenius plot is very close to the value reported for the typical wormlike micellar solution. In contrast to CTAB no formation of viscoelastic wormlike micelles could be observed with DTAB, although, the solution viscosity increases. The

  4. Cationic surfactants based on ferrocene

    SciTech Connect

    Pankratov, V.A.; Kucherova, N.L.; Abramzon, A.A.

    1988-07-20

    Quaternary ammonium salts based on ferrocene were synthesized and their surface active properties were studied as potential cationic surfactants and for uses including antiknock compounds. The salts were halide and nitrate derivatives of dimethylferrocenylmethylammonium and were prepared by aminomethylation of ferrocene. Chemical reaction yields, melting points, surface tension isotherms, and other characteristics were assessed.

  5. Amino acid-based surfactants – do they deserve more attention?

    PubMed

    Bordes, Romain; Holmberg, Krister

    2015-08-01

    The 20 standard amino acids (together with a few more that are not used in the biosynthesis of proteins) constitute a versatile tool box for synthesis of surfactants. Anionic, cationic and zwitterionic amphiphiles can be prepared and surfactants with several functional groups can be obtained by the proper choice of starting amino acid. This review gives examples of procedures used for preparation and discusses important physicochemical properties of the amphiphiles and how these can be taken advantage of for various applications. Micelles with a chiral surface can be obtained by self-assembly of enantiomerically pure surfactants and such supramolecular chirality can be utilized for asymmetric organic synthesis and for preparation of mesoporous materials with chiral pores. Surfactants based on amino acids with two carboxyl groups are effective chelating agents and can be used as collectors in mineral ore flotation. A surfactant based on cysteine readily oxidizes into the corresponding cystine compound, which can be regarded as a gemini surfactant. The facile and reversible cysteine-cystine transformation has been taken advantage of in the design of a switchable surfactant. A very attractive aspect of surfactants based on amino acids is that the polar head-group is entirely natural and that the linkage to the hydrophobic tail, which is often an ester or an amide bond, is easily cleaved. The rate of degradation can be tailored by the structure of the amphiphile. The ester linkage in betaine ester surfactants is particularly susceptible to alkaline hydrolysis and this surfactant type can be used as a biocide with short-lived action. This paper is not intended as a full review on the topic. Instead it highlights concepts that are unique to amino acid-based surfactants and that we believe can have practical implications.

  6. Effects of spacer chain length of amino acid-based gemini surfactants on wormlike micelle formation.

    PubMed

    Sakai, Kenichi; Nomura, Kazuyuki; Shrestha, Rekha Goswami; Endo, Takeshi; Sakamoto, Kazutami; Sakai, Hideki; Abe, Masahiko

    2014-01-01

    We studied the effects of the spacer chain length of amino acid-based gemini surfactants on the formation of wormlike micelles in aqueous solutions. The surfactants used were synthesized by reacting dodecanoylglutamic acid anhydride with diamine compounds (ethylenediamine, pentanediamine, and octanediamine), and were abbreviated as 12-GsG-12 (s: the spacer chain length of 2, 5, and 8 methylene units). These surfactants yielded viscoelastic wormlike micellar solutions at pH 9 upon mixing with a cationic monomeric surfactant, hexadecyltrimethylammonium bromide (HTAB). We found that the rheological behavior was strongly dependent on the spacer chain length and HTAB concentration. When the shortest spacer chain analogue (12-G2G-12) was used, an increased HTAB concentration resulted in the following structural transformations of the micelles: (i) spherical or rodlike micelles; (ii) anionic wormlike micelles exhibiting a transient network structure; (iii) anionic wormlike micelles with a micellar branching or interconnected structure; and (iv) cationic wormlike micelles. Similarly, when the middle spacer chain analogue (12-G5G-12) was used, a structural transformation from anionic to cationic wormlike micelles occurs; however, molecular aggregates with a lower positive curvature were also formed in this transition region. When the longest spacer analogue (12-G8G-12) was used, the formation of cation-rich molecular aggregates was not observed. These transition behaviors were attributed to the packing geometry of the gemini surfactants with HTAB. Additionally, as the spacer chain length increased, the zero-shear viscosity in the anionic wormlike micellar region decreased, suggesting limited one-dimensional micellar growth of spherical, rodlike, or anionic wormlike micelles.

  7. Hydrodynamic size of DNA/cationic gemini surfactant complex as a function of surfactant structure.

    PubMed

    Devínsky, Ferdinand; Pisárcik, Martin; Lacko, Ivan

    2009-06-01

    The present study deals with the determination of hydrodynamic size of DNA/cationic gemini surfactant complex in sodium bromide solution using the dynamic light scattering method. Cationic gemini surfactants with polymethylene spacer of variable length were used for the interaction with DNA. The scattering experiments were performed at constant DNA and sodium bromide concentrations and variable surfactant concentration in the premicellar and micellar regions as a function of surfactant spacer length. It was found that the DNA conformation strongly depends on the polymethylene spacer length as well as on the surfactant concentration relative to the surfactant critical micelle concentration. Gemini surfactant molecules with 4 methylene groups in the spacer were found to be the least efficient DNA compacting agent in the region above the surfactant cmc. Gemini molecules with the shortest spacer length (2 methylene groups) and the longest spacer length (8 methylene groups) investigated showed the most efficient DNA compaction ability. PMID:19592712

  8. Cationic versus anionic surfactant in tuning the structure and interaction of nanoparticle, protein, and surfactant complexes.

    PubMed

    Mehan, Sumit; Aswal, Vinod K; Kohlbrecher, Joachim

    2014-08-26

    The structure and interaction in complexes of anionic Ludox HS40 silica nanoparticle, anionic bovine serum albumin (BSA) protein, and cationic dodecyl trimethylammonium bromide (DTAB) surfactant have been studied using small-angle neutron scattering (SANS). The results are compared with similar complexes having anionic sodium dodecyl sulfate (SDS) surfactant (Mehan, S; Chinchalikar, A. J.; Kumar, S.; Aswal, V. K.; Schweins, R. Langmuir 2013, 29, 11290). In both cases (DTAB and SDS), the structure in nanoparticle-protein-surfactant complexes is predominantly determined by the interactions of the individual two-component systems. The nanoparticle-surfactant (mediated through protein-surfactant complex) and protein-surfactant interactions for DTAB, but nanoparticle-protein (mediated through protein-surfactant complex) and protein-surfactant interactions for SDS, are found to be responsible for the resultant structure of nanoparticle-protein-surfactant complexes. Irrespective of the charge on the surfactant, the cooperative binding of surfactant with protein leads to micellelike clusters of surfactant formed along the unfolded protein chain. The adsorption of these protein-surfactant complexes for DTAB on oppositely charged nanoparticles gives rise to the protein-surfactant complex-mediated aggregation of nanoparticles (similar to that of DTAB surfactant). It is unlike that of depletion-induced aggregation of nanoparticles with nonadsorption of protein-surfactant complexes for SDS in similarly charged nanoparticle systems (similar to that of protein alone). The modifications in nanoparticle aggregation as well as unfolding of protein in these systems as compared to the corresponding two-component systems have also been examined by selectively contrast matching the constituents.

  9. Flexible polyelectrolyte conformation in the presence of cationic and anionic surfactants

    NASA Astrophysics Data System (ADS)

    Passos, C. B.; Kuhn, P. S.; Diehl, A.

    2015-11-01

    In this work we have studied the conformation of flexible polyelectrolyte chains in the presence of cationic and anionic surfactant molecules. We developed a simple theoretical model for the formation of the polyelectrolyte-cationic surfactant complexes and mixed micelles formed by cationic and anionic surfactant molecules, in the framework of the Debye-Hückel-Bjerrum-Manning and Flory theories, with the hydrophobic interaction included explicitly as an effective short-ranged attraction between the surfactant hydrocarbon tails. This simple model allows us to calculate the extension of the polyelectrolyte-cationic surfactant complexes as a function of the anionic surfactant concentration, for different types of cationic and anionic surfactant molecules. A discrete conformational transition from a collapsed state to an elongated coil was found, for all surfactant chain lengths we have considered, in agreement with the experimental observations for the unfolding of ​DNA-cationic surfactant complexes.

  10. Ordered DNA-Surfactant Hybrid Nanospheres Triggered by Magnetic Cationic Surfactants for Photon- and Magneto-Manipulated Drug Delivery and Release.

    PubMed

    Xu, Lu; Wang, Yitong; Wei, Guangcheng; Feng, Lei; Dong, Shuli; Hao, Jingcheng

    2015-12-14

    Here we construct for the first time ordered surfactant-DNA hybrid nanospheres of double-strand (ds) DNA and cationic surfactants with magnetic counterion, [FeCl3Br](-). The specificity of the magnetic cationic surfactants that can compact DNA at high concentrations makes it possible for building ordered nanospheres through aggregation, fusion, and coagulation. Cationic surfactants with conventional Br(-) cannot produce spheres under the same condition because they lose the DNA compaction ability. When a light-responsive magnetic cationic surfactant is used to produce nanospheres, a dual-controllable drug-delivery platform can be built simply by the applications of external magnetic force and alternative UV and visible light. These nanospheres obtain high drug absorption efficiency, slow release property, and good biocompatibility. There is potential for effective magnetic-field-based targeted drug delivery, followed by photocontrollable drug release. We deduce that our results might be of great interest for making new functional nucleic-acid-based nanomachines and be envisioned to find applications in nanotechnology and biochemistry.

  11. Ordered DNA-Surfactant Hybrid Nanospheres Triggered by Magnetic Cationic Surfactants for Photon- and Magneto-Manipulated Drug Delivery and Release.

    PubMed

    Xu, Lu; Wang, Yitong; Wei, Guangcheng; Feng, Lei; Dong, Shuli; Hao, Jingcheng

    2015-12-14

    Here we construct for the first time ordered surfactant-DNA hybrid nanospheres of double-strand (ds) DNA and cationic surfactants with magnetic counterion, [FeCl3Br](-). The specificity of the magnetic cationic surfactants that can compact DNA at high concentrations makes it possible for building ordered nanospheres through aggregation, fusion, and coagulation. Cationic surfactants with conventional Br(-) cannot produce spheres under the same condition because they lose the DNA compaction ability. When a light-responsive magnetic cationic surfactant is used to produce nanospheres, a dual-controllable drug-delivery platform can be built simply by the applications of external magnetic force and alternative UV and visible light. These nanospheres obtain high drug absorption efficiency, slow release property, and good biocompatibility. There is potential for effective magnetic-field-based targeted drug delivery, followed by photocontrollable drug release. We deduce that our results might be of great interest for making new functional nucleic-acid-based nanomachines and be envisioned to find applications in nanotechnology and biochemistry. PMID:26571346

  12. Solution properties and emulsification properties of amino acid-based gemini surfactants derived from cysteine.

    PubMed

    Yoshimura, Tomokazu; Sakato, Ayako; Esumi, Kunio

    2013-01-01

    Amino acid-based anionic gemini surfactants (2C(n)diCys, where n represents an alkyl chain with a length of 10, 12, or 14 carbons and "di" and "Cys" indicate adipoyl and cysteine, respectively) were synthesized using the amino acid cysteine. Biodegradability, equilibrium surface tension, and dynamic light scattering were used to characterize the properties of gemini surfactants. Additionally, the effects of alkyl chain length, number of chains, and structure on these properties were evaluated by comparing previously reported gemini surfactants derived from cystine (2C(n)Cys) and monomeric surfactants (C(n)Cys). 2C(n)diCys shows relatively higher biodegradability than does C(n)Cys and previously reported sugar-based gemini surfactants. Both critical micelle concentration (CMC) and surface tension decrease when alkyl chain length is increased from 10 to 12, while a further increase in chain length to 14 results in increased CMC and surface tension. This indicates that long-chain gemini surfactants have a decreased aggregation tendency due to the steric hindrance of the bulky spacer as well as premicelle formation at concentrations below the CMC and are poorly packed at the air/water interface. Formation of micelles (measuring 2 to 5 nm in solution) from 2C(n)diCys shows no dependence on alkyl chain length. Further, shaking the mixtures of aqueous 2C(n)diCys surfactant solutions and squalane results in the formation of oil-in-water type emulsions. The highly stable emulsions are formed using 2C₁₂diCys or 2C₁₄diCys solution and squalane in a 1:1 or 2:1 volume ratio.

  13. Switchable Pickering emulsions stabilized by silica nanoparticles hydrophobized in situ with a conventional cationic surfactant.

    PubMed

    Zhu, Yue; Jiang, Jianzhong; Liu, Kaihong; Cui, Zhenggang; Binks, Bernard P

    2015-03-24

    A stable oil-in-water Pickering emulsion stabilized by negatively charged silica nanoparticles hydrophobized in situ with a trace amount of a conventional cationic surfactant can be rendered unstable on addition of an equimolar amount of an anionic surfactant. The emulsion can be subsequently restabilized by adding a similar trace amount of cationic surfactant along with rehomogenization. This destabilization-stabilization behavior can be cycled many times, demonstrating that the Pickering emulsion is switchable. The trigger is the stronger electrostatic interaction between the oppositely charged ionic surfactants compared with that between the cationic surfactant and the (initially) negatively charged particle surfaces. The cationic surfactant prefers to form ion pairs with the added anionic surfactant and thus desorbs from particle surfaces rendering them surface-inactive. This access to switchable Pickering emulsions is easier than those employing switchable surfactants, polymers, or surface-active particles, avoiding both the complicated synthesis and the stringent switching conditions.

  14. Aqueous behaviour of cationic surfactants containing a cleavable group.

    PubMed

    Samakande, Austin; Chaghi, Radhouane; Derrien, Gaelle; Charnay, Clarence; Hartmann, Patrice C

    2008-04-01

    The aggregation behaviour of two novel cationic RAFT agents (transfer surfactants); N,N-dimethyl-N-(4-(((phenylcarbonothioyl)thio)methyl)benzyl)ethanammonium bromide (PCDBAB) and N-(4-((((dodecylthio)-carbonothioyl)thio)methyl)benzyl)-N,N-dimethylethanammonium bromide (DCTBAB) in diluted solutions have been investigated by surface tension, conductimetry and microcalorimetry measurements. The thermodynamic parameters i.e. the critical micelle concentration (cmc), the degree of micelle ionization (alpha), the head group surface area (a 0), Delta H mic, Delta G mic and T Delta S mic are reported at 303 K. The thermodynamic parameters have been compared to those of the conventional surfactant cetyltrimethylammonium bromide (CTAB) in order to specify structural relationships. The obtained results have been discussed considering the hydrophobic behaviour of the S-C=S- linkage and the specific interactions that arise from the introduction of the benzene ring into the hydrophobic part.

  15. Interactions of cationic trimeric, gemini and monomeric surfactants with trianionic curcumin in aqueous solution.

    PubMed

    Wang, Meina; Wu, Chunxian; Tang, Yongqiang; Fan, Yaxun; Han, Yuchun; Wang, Yilin

    2014-05-21

    Interactions of trianionic curcumin (Cur(3-)) with a series of cationic surfactants, monomeric surfactant dodecyl trimethylammonium bromide (DTAB), dimeric surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and trimeric surfactant tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD), have been investigated in aqueous solution of pH 13.0. Surface tension and spectral measurements indicate that the cationic surfactants display a similar surfactant concentration dependent interaction process with Cur(3-), involving three interaction stages. At first the three cationic surfactants electrostatically bind on Cur(3-) to form the surfactant-Cur(3-) complex. Then the bound and unbound cationic surfactants with Cur(3-) aggregate into surfactant-Cur(3-) mixed micelles through hydrophobic interactions above the critical micelle concentration of the surfactants (CMCC) in the presence of Cur(3-). Finally excess unbound surfactants self-assemble into micelles like those without Cur(3-). For all the three surfactants, the addition of Cur(3-) only decreases the critical micelle concentration of 12-6-12 but does not affect the critical micelle concentration of DTAB and DTAD. As the oligomeric degree of surfactants increases, the intermolecular interaction of the cationic surfactants with Cur(3-) increases and the surfactant amount needed for Cur(3-) encapsulation decreases. Compared with 12-6-12, either the weaker interaction of DTAB with Cur(3-) or stronger interaction of DTAD with Cur(3-) limits the stability or solubility of Cur(3-) in surfactant micelles. Therefore, gemini surfactant 12-6-12 is the best choice to effectively suppress Cur(3-) degradation at very low concentrations. Isothermal titration microcalorimetry, surface tension and (1)H NMR results reveal that 12-6-12 and Cur(3-) form a (12-6-12)2-Cur(3-) complex and start to form micelles at extremely decreased concentrations, where either 12-6-12 or Cur(3-) works as a bridge

  16. The preparation of calcium carbonate crystals regulated by mixed cationic/cationic surfactants

    NASA Astrophysics Data System (ADS)

    Zhao, Yingyuan; Li, Shuxia; Yu, Li; Liu, Yonghui; Wang, Xiaoqing; Jiao, Jingjing

    2011-06-01

    Cationic surfactants, didodecyldimethylammonium bromide (DDAB), 1-dodecyl-3-methylimidazolium bromide ([C 12mim]Br) and DDAB/[C 12mim]Br mixture were used to induce the formation of calcium carbonate (CaCO 3) crystals at ambient temperature. The obtained CaCO 3 particles were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The morphologies of CaCO 3 crystals changed from laminated cube to sphericity and string shape with the increase of DDAB and [C 12mim]Br concentration, respectively. Flower-shaped CaCO 3 crystals were synthesized in the mixed DDAB/[C 12mim]Br system. More importantly, it was found that the complete conversion from calcite to vaterite was achieved at room temperature only through changing DDAB concentration. The regulations of DDAB and [C 12mim]Br to CaCO 3 crystals have been compared with that of dodecyltrimethylammonium bromide (DTAB) in our previous work and possible mechanisms have been proposed. It is shown that the cationic surfactants can control the crystallization of CaCO 3 and the number of hydrophobic alkyl chains of cationic surfactants might be more effective in modulating the crystallization of vaterite than the head groups.

  17. Adsorption of mixed cationic-nonionic surfactant and its effect on bentonite structure.

    PubMed

    Zhang, Yaxin; Zhao, Yan; Zhu, Yong; Wu, Huayong; Wang, Hongtao; Lu, Wenjing

    2012-01-01

    The adsorption of cationic-nonionic mixed surfactant onto bentonite and its effect on bentonite structure were investigated. The objective was to improve the understanding of surfactant behavior on clay mineral for its possible use in remediation technologies of soil and groundwater contaminated by toxic organic compounds. The cationic surfactant used was hexadecylpyridinium bromide (HDPB), and the nonionic surfactant was Triton X-100 (TX100). Adsorption of TX100 was enhanced significantly by the addition of HDPB, but this enhancement decreased with an increase in the fraction of the cationic surfactant. Part of HDPB was replaced by TX100 which decreased the adsorption of HDPB. However, the total adsorbed amount of the mixed surfactant was still increased substantially, indicating the synergistic effect between the cationic and nonionic surfactants. The surfactant-modified bentonite was characterized by Brunauer-Emmett-Teller specific surface area measurement, Fourier transform infrared spectroscopy, and thermogravimetric-derivative thermogravimetric/differential thermal analyses. Surfactant intercalation was found to decrease the bentonite specific surface area, pore volume, and surface roughness and irregularities, as calculated by nitrogen adsorption-desorption isotherms. The co-adsorption of the cationic and nonionic surfactants increased the ordering conformation of the adsorbed surfactants on bentonite, but decreased the thermal stability of the organobentonite system.

  18. USE OF CATIONIC SURFACTANTS TO MODIFY SOIL SURFACES TO PROMOTE SORPTION AND RETARD MIGRATION OF HYDROPHOBIC ORGANIC COMPOUNDS

    EPA Science Inventory

    Cationic surfactants can be used to modify surfaces of soils and subsurface materials to promote adsorption of hydrophobic organic compounds (HOC). Batch and column experiments were performed to investigate this phenomenon with the cationic surfactant dodecylpyridinium (DP), a se...

  19. Interactions of bovine serum albumin with cationic imidazolium and quaternary ammonium gemini surfactants: effects of surfactant architecture.

    PubMed

    Zhou, Ting; Ao, Mingqi; Xu, Guiying; Liu, Teng; Zhang, Juan

    2013-01-01

    The interactions of BSA with a series of cationic imidazolium gemini surfactants ([C(n)-s-C(n)im]Br(2), n=10, 12, 14, s=2, 4, 6), quaternary ammonium surfactants (C(12)C(2)C(12)), and their corresponding monomers ([C(12)mim]Br and DTAB) are investigated by fluorescence using pyrene as a molecular probe, synchronous fluorescence, circular dichroism (CD), and UV-visible absorption spectra. These surfactants are used to elucidate the effects of surfactant hydrophilic head group, spacer length, and hydrophobic chain length on the conformation of BSA. The results of fluorescence spectra and CD show that the imidazolium gemini surfactants with shorter spacers or with longer hydrophobic chains have a larger effect on BSA unfolding, and the imidazolium gemini surfactant interacts with BSA more strongly than its corresponding monomer and the quaternary ammonium gemini surfactant. These conclusions have been confirmed by the binding constants (K(a)) and binding sites (n) for the BSA/surfactant system. Stern-Volmer quenching constants K(SV) of cationic surfactants binding to BSA are obtained, indicating that the probable quenching mechanism is initiated by ground-state complex formation rather than by dynamic collision. Moreover, the synchronous fluorescence spectra show that the surfactants mainly interact with tryptophan residues of BSA.

  20. Elucidating the Higher Stability of Vanadium (V) Cations in Mixed Acid Based Redox Flow Battery Electrolytes

    SciTech Connect

    Vijayakumar, M.; Wang, Wei; Nie, Zimin; Sprenkle, Vincent L.; Hu, Jian Z.

    2013-11-01

    The Vanadium (V) cation structures in mixed acid based electrolyte solution were analysed by density functional theory (DFT) based computational modelling and 51V and 35Cl Nuclear Magnetic Resonance (NMR) spectroscopy. The Vanadium (V) cation exists as di-nuclear [V2O3Cl2.6H2O]2+ compound at higher vanadium concentrations (≥1.75M). In particular, at high temperatures (>295K) this di-nuclear compound undergoes ligand exchange process with nearby solvent chlorine molecule and forms chlorine bonded [V2O3Cl2.6H2O]2+ compound. This chlorine bonded [V2O3Cl2.6H2O]2+ compound might be resistant to the de-protonation reaction which is the initial step in the precipitation reaction in Vanadium based electrolyte solutions. The combined theoretical and experimental approach reveals that formation of chlorine bonded [V2O3Cl2.6H2O]2+ compound might be central to the observed higher thermal stability of mixed acid based Vanadium (V) electrolyte solutions.

  1. Effect of electrolytes on wettability of glass surface using anionic and cationic surfactant solutions.

    PubMed

    Chaudhuri, Rajib Ghosh; Paria, Santanu

    2014-01-01

    Wetting behavior of a flat glass surface using pure nonionic, anionic, and cationic surfactants solutions has been studied by the dynamic contact angle (Wilhelmy plate) measurement technique. The advancing contact angle increases with the increasing concentration of surfactant and the value is maximum in the presence of cationic surfactant CTAB. The effect of different electrolytes in the presence of ionic surfactants was also studied to see the wetting behavior in the presence of electrolytes. The presence of electrolytes on ionic surfactant solutions significantly enhance the contact angle at very low concentration, which in turn lead to reduction in ionic surfactant requirement by more than 90% to achieve a particular contact angle. The effectiveness of electrolyte highly depends on the valance of counter ion. The reduction of ionic surfactant requirement is mostly useful for different applications such as flotation, and colloidal stability to reduce the production cost as well as environmental pollution.

  2. Improved methylene blue two-phase titration method for determining cationic surfactant concentration in high-salinity brine.

    PubMed

    Cui, Leyu; Puerto, Maura; López-Salinas, José L; Biswal, Sibani L; Hirasaki, George J

    2014-11-18

    The methylene blue (MB) two-phase titration method is a rapid and efficient method for determining the concentrations of anionic surfactants. The point at which the aqueous and chloroform phases appear equally blue is called Epton's end point. However, many inorganic anions, e.g., Cl(-), NO3(-), Br(-), and I(-), can form ion pairs with MB(+) and interfere with Epton's end point, resulting in the failure of the MB two-phase titration in high-salinity brine. Here we present a method to extend the MB two-phase titration method for determining the concentration of various cationic surfactants in both deionized water and high-salinity brine (22% total dissolved solid). A colorless end point, at which the blue color is completely transferred from the aqueous phase to the chloroform phase, is proposed as titration end point. Light absorbance at the characteristic wavelength of MB is measured using a spectrophotometer. When the absorbance falls below a threshold value of 0.04, the aqueous phase is considered colorless, indicating that the end point has been reached. By using this improved method, the overall error for the titration of a permanent cationic surfactant, e.g., dodecyltrimethylammonium bromide, in deionized (DI) water and high-salinity brine is 1.274% and 1.322% with limits of detection (LOD) of 0.149 and 0.215 mM, respectively. Compared to the traditional acid-base titration method, the error of this improved method for a switchable cationic surfactant, e.g., tertiary amine surfactant (Ethomeen C12), is 2.22% in DI water and 0.106% with LOD of 0.369 and 0.439 mM, respectively.

  3. Thermodynamics of cationic surfactant sorption onto natural clinoptilolite

    SciTech Connect

    Sullivan, E.J.; Bowman, R.S.; Carey, J.W.

    1998-10-15

    Sorption enthalpies of hexadecyltrimethylammonium bromide (HDTMA) as monomers and micelles and tetraethylammonium bromide (TEA) were used with surfactant, counterion, and co-ion sorption isotherms to infer the conformation, sorption mechanism, and relative stability of the sorbed surfactants on natural clinoptilolite. The average value of the sorption enthalpy was {minus}10.38 kJ/mol for monomers, {minus}11.98 kJ/mol for micelles, and +3.03 kJ/mol for TEA. Sorption of monomers produced a lower sorption plateau than equivalent micelle sorption (maxima 145 mmol/kg, 225 mmol/kg). Analysis of the sorption data demonstrated a change in the sorption mechanism at the external cation exchange capacity (ECEC) of clinoptilolite. Sorption data from below and above the ECEC were fit to a simple polynomial model and the Gibbs free energy of sorption ({Delta} G{sub m}{sup 0}) and sorption entropies were calculated. Resultant values of {Delta} G{sub m}{sup 0} were {minus}9.27 and {minus}14.38 kJ/mol for HDTMA monomers and micelles, respectively, for sorption below the ECEC, and {minus}16.11 and {minus}23.10 kJ/mol, respectively, for sorption above the ECEC. The value for TEA was {minus}1.04 kJ/mol, indicating weaker sorption than for HDTMA. Monomer sorption to clinoptilolite exceeded the ECEC, even when the solution concentration was below the critical micelle concentration. Hydrophobic (tail-tail) components of {Delta} G{sub m}{sup 0} were the driving force for sorption of HDTMA, both below and above the ECEC. A significant kinetic effect was observed in the sorption isotherms with a period of rapid sorption followed by slow equilibration requiring 7 days to achieve steady state for HDTMA; TEA equilibration occurred within 24 h.

  4. Enhanced spectrophotometric determination of Losartan potassium based on its physicochemical interaction with cationic surfactant

    NASA Astrophysics Data System (ADS)

    Abdel-Fattah, Laila; Abdel-Aziz, Lobna; Gaied, Mariam

    2015-02-01

    In this study, a simple and sensitive spectrophotometric method was developed for determination of Losartan potassium (LST K), an angiotensin-II receptor (type AT1) antagonist, in presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The physicochemical interaction of LST K with CTAB was investigated. The effect of cationic micelles on the spectroscopic and acid-base properties of LST K was studied at pH 7.4. The binding constant (Kb) and the partition coefficient (Kx) of LST K-CTAB were 1.62 × 105 M-1 and 1.38 × 105; respectively. The binding of LST K to CTAB micelles implied a shift in drug acidity constant (ΔpKa = 0.422). The developed method is linear over the range 0.5-28 μg mL-1. The accuracy was evaluated and was found to be 99.79 ± 0.509% and the relative standard deviation for intraday and interday precision was 0.821 and 0.963; respectively. The method was successfully applied to determine LST K in pharmaceutical formulations.

  5. Charge screening between anionic and cationic surfactants in ionic liquids.

    PubMed

    Chen, Lang G; Bermudez, Harry

    2013-03-01

    The aggregation and interfacial behavior of mixtures of anionic (sodium dodecylsulfate, SDS) and cationic (dodecylammonium bromide, DTAB) surfactants were investigated. A room-temperature ionic liquid (IL) was explored as a solvent for the SDS/DTAB system and compared to water. The critical micelle concentration (cmc) and composition in mixed micelles were determined for both solvents. Our experiments showed nearly ideal mixing of SDS/DTAB over the entire composition range and suggest that charge screening is prominent in ILs. This behavior is in sharp contrast to the strong electrostatic attraction and a multiphase composition gap in water. Two models by Clint and Rubingh, which describe ideal and nonideal micellar behavior, respectively, are discussed on the basis of our results. According to Rubingh's model, the composition of mixed micelles is gradually changing with the bulk composition in ILs but tends to be a 1:1 ratio in water. The results here are further support of the strong charge screening in ionic liquids.

  6. Functional role of cationic surfactant to control the nano size of silica powder

    NASA Astrophysics Data System (ADS)

    Singh, L. P.; Bhattacharyya, S. K.; Mishra, G.; Ahalawat, S.

    2011-09-01

    Preparation of dispersed, amorphous, spherical silica nanoparticles using cationic surfactant as organic template, tetraethoxysilane (TEOS) as silica precursor and ammonia as catalyst has been carried out using sol gel process. The aim of the present study was to evaluate the simultaneous effects of cationic surfactant on the textural and structural properties of silica nanoparticles. We used a series of the cationic surfactants, dodecytrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB) to evaluate the effects of the chain length of cationic surfactant on the grain size of silica nanoparticles. The size of silica nanoparticles can be finely tuned in the range ~50-100 nm by changing the chain length of cationic surfactant. Decreasing the particle size of silica nano particles resulted in increase in chain length of cationic surfactant. Further, these silica nanoparticles are incorporated with cement paste to evaluate the beneficial effect on mechanical properties of cement. Synthesized silica nanoparticles were analyzed using scanning electron microscopy (SEM), 29Si MAS NMR, powder X-ray diffraction techniques (XRD) and IR studies.

  7. Cationic surfactant adsorption states determined by the dependence of the electrophoretic mobility on dilution

    SciTech Connect

    Chang, C.H.

    1987-01-01

    A dilution method was devised in order to examine the dependence of the mobility of dilute aqueous coal dispersions on concentration. Mobility trends observed on dilution with water and the parent surfactant solution were interpreted in terms of desorption and adsorption of surfactant on coal. The dispersions were also studied by comparing the surface tension of surfactant solutions with the filtrates from a range of coal dispersions. The surfactants used were DTAB (Dodecyltrimethylammonium Bromide), CTAB (Cetyltrimethylammonium Bromide), ATLAS G-271 (N-Soya-N-ethyl morpholinium ethosulfate) and MERPOL-SE, (CH/sub 3/-(CH/sub 2/)/sub 24/-(OCH/sub 2/CH/sub 2/)/sub 8/-OH). The mobility of coal in the presence of cationic surfactant decreased as the dilution ratio increased and reach a constant value. It was also shown that the mobility remained near zero and constant if a non-ionic surfactant was used. On dilution with cationic surfactant solution, the mobility rose to a constant value at high dilution which was more than twice the aqueous asymptote suggesting the separate contribution of reversibility adsorbed surfactant. The structure of surfactant was another effect which controlled the adsorption mechanism. The two major properties of surfactant structure were the hydrophobicity and steric hindrance. The results also implied that hydrophobic tail-adsorbed was the dominant mechanism in contrast to the model which was proposed in earlier studies. Comparison of surface tension between pure surfactant solution and the filtrate from coal/surfactant solution indicated that the surfactants did not all act alike in some cases. Natural surfactant had been desorbed or eluted and in some cases surfactant had been adsorbed.

  8. [Nutrition, acid-base metabolism, cation-anion difference and total base balance in humans].

    PubMed

    Mioni, R; Sala, P; Mioni, G

    2008-01-01

    The relationship between dietary intake and acid-base metabolism has been investigated in the past by means of the inorganic cation-anion difference (C(+)(nm)-A(-)(nm)) method based on dietary ash-acidity titration after the oxidative combustion of food samples. Besides the inorganic components of TA (A(-)(nm)-C(+)(nm)), which are under renal control, there are also metabolizable components (A(-)(nm)-C(+)(nm)) of TA, which are under the control of the intermediate metabolism. The whole body base balance, NBb(W), is obtained only by the application of C(+)(nm)-A(-)(nm) to food, feces and urine, while the metabolizable component (A(-)(nm)-C(+)(nm)) is disregarded. A novel method has been subsequently suggested to calculate the net balance of fixed acid, made up by the difference between the input of net endogenous acid production: NEAP = SO(4)(2-)+A(-)(m)-(C(+)(nm)-A(-)(nm)), and the output of net acid excretion: NAE = TA + NH(4)(+) - HCO(3)(-). This approach has been criticized because 1) it includes metabolizable acids, whose production cannot be measured independently; 2) the specific control of metabolizable acid and base has been incorrectly attributed to the kidney; 3) the inclusion of A-m in the balance input generates an acid overload; 4) the object of measurement in making up a balance has to be the same, a condition not fulfilled as NEAP is different from NAE. Lastly, by rearranging the net balance of the acid equation, the balance of nonmetabolizable acid equation is obtained. Therefore, any discrepancy between these two equations is due to the inaccuracy in the urine measurement of metabolizable cations and/or anions.

  9. Spectroscopic study on interaction between three cationic surfactants with different alkyl chain lengths and DNA.

    PubMed

    Guo, Lili; Zhang, Zhaohong; Qiao, Heng; Liu, Miao; Shen, Manli; Yuan, Tianxin; Chen, Jing; Dionysiou, Dionysios D

    2015-01-01

    In this study, the interaction between cationic surfactants with different alkyl chain lengths, such as hexyltrimethyl ammonium bromide (HTAB), dodecyltrimethyl ammonium bromide (DTAB) and cetyltrimethyl ammonium bromide (CTAB), and DNA was investigated by UV-vis spectroscopy, fluorescence spectroscopy and viscosity techniques. The results showed that these three cationic surfactants with different hydrocarbon chain lengths could all interact with DNA. Their binding modes were estimated and their interaction strength was compared. In addition, the effects of the surfactant, NaCl and phosphate ion concentrations on the interaction were reviewed. It is wished that this work would provide some valuable references to investigate the influence of cationic surfactants with different alkyl chain lengths on DNA.

  10. Self-aggregation of cationic dimeric surfactants in water-ionic liquid binary mixtures.

    PubMed

    Martín, Victoria Isabel; Rodríguez, Amalia; Laschewsky, André; Moyá, María Luisa

    2014-09-15

    The micellization of four dimeric cationic surfactants ("gemini surfactants") derived from N-dodecyl-N,N,N-trimethylammonium chloride was studied in pure water and in water-ionic liquid (IL) solutions by a wide range of techniques. The dimeric surfactants are distinguished by their rigid spacer groups separating the two surfactant motifs, which range from C3 to C5 in length. In order to minimize organic ion pairing effects as well as the role of the ionic liquids as potential co-surfactants, ILs with inorganic hydrophilic anions and organic cations of limited hydrophobicity were chosen, namely ethyl, butyl, and hexyl-3-imidazolium chlorides. (1)H NMR two-dimensional, 2D, rotating frame nuclear Overhauser effect spectroscopy measurements, ROESY, supported this premise. The spacer nature hardly affects the micellization process, neither in water nor in water-IL solutions. However, it does influence the tendency of the dimeric surfactants to form elongated micelles when surfactant concentration increases. In order to have a better understanding of the ternary water-IL surfactant systems, the micellization of the surfactants was also studied in aqueous NaCl solutions, in water-ethylene glycol and in water-formamide binary mixtures. The combined results show that the ionic liquids play a double role in the mixed systems, operating simultaneously as background electrolytes and as polar organic solvents. The IL role as organic co-solvent becomes more dominant when its concentration increases, and when the IL alkyl chain length augments.

  11. Rheological characterizations and molecular dynamics simulations of self-assembly in an anionic/cationic surfactant mixture.

    PubMed

    Yan, Zhihu; Dai, Caili; Zhao, Mingwei; Sun, Yongpeng

    2016-07-13

    The formation of self-assemblies in mixed amino acid-based anionic N-hexadecanoylglutamic acid (HGA) and cationic benzyldimethyl hexadecylammonium chloride (HDBAC) surfactants in aqueous solutions has been characterized. With rheological analysis, the viscoelastic properties of the mixed system are found to be completely dependent on the concentration of HDBAC. Molecular dynamics simulation results suggest that the morphology of self-assembly can be regulated from spherical micelles to wormlike micelles by the addition of HDBAC. The aromatic group of HDBAC adsorption provides a "charge-neutral" function to the micelle corona; the repulsive interactions within the head group of HGA are progressively screened and closely packed. In addition, the dynamic processes and formation mechanisms of self-assembly were analyzed in detail with molecular simulation techniques. PMID:27373717

  12. Extended delivery of an anionic drug by contact lens loaded with a cationic surfactant.

    PubMed

    Bengani, Lokendrakumar C; Chauhan, Anuj

    2013-04-01

    Drug eluding contact lenses can be very effective vehicles for ophthalmic drug delivery, but are incapable of releasing drug for more than a few hours. We propose to optimize the interactions of the polymer matrix of the contact lens with the hydrophobic tails of ionic surfactants to adsorb the surfactant molecules on the polymer with high packing and thus create a high surface charge. Ionic drugs can then adsorb on the charged surfactant coated surfaces with high affinity to reduce the transport rates, leading to extended release. Specifically, we show control release of an anionic drug dexamethasone 21-disodium phosphate from poly-hydroxyethyl methacrylate (p-HEMA) contact lenses by utilizing cationic surfactant (cetalkonium chloride). The partition coefficient of the drug increase exponentially with surfactant loading in the gel in at least qualitative agreement with the Debye-Hückel theory. The drug adsorbs on the surfactant covered polymer, and can also diffuse along the surface with diffusivity lower than that for the free drug, leading to a reduction in the effective diffusivity, which is the weighted combination of the free and surface diffusivities. The addition of surfactant did not impact transparency of lenses, and had additional benefits of increase in wettability and significant reduction in protein absorption. With a surfactant loading of about 10%, the drug release duration was increased from about 2 h to 50 h in 1-day ACUVUE(®) contact lenses, proving the viability of using surfactant for increasing drug release durations.

  13. Loading capacity and interaction of DNA binding on catanionic vesicles with different cationic surfactants.

    PubMed

    Xu, Lu; Chen, Jingfei; Feng, Lei; Dong, Shuli; Hao, Jingcheng

    2014-12-01

    Cationic and anionic (catanionic) vesicles were constructed from the mixtures of sodium laurate (SL) and alkyltrimethylammonium bromide (CnTAB, n = 12, 14, and 16) and were used to control the loading capacity of DNA. The binding saturation point (BSP) of DNA to catanionic vesicles increases with the chain length of cationic surfactants, which is at 1.0, 1.3 and 1.5 for CnTAB with n = 12, 14, and 16, respectively. Our measurements showed that the loading capacity and affinity of DNA can be controlled by catanionic vesicles. It increases with the chain length of cationic surfactants. Because of a large reduction in surface charge density, catanionic vesicles are prone to undergo re-aggregation or fusion with the addition of DNA. DNA molecules can still maintain original coil state during the interaction with catanionic CnTAL vesicles. (1)H NMR data reveals that the obvious dissociation of anionic ions, L(-), from catanionic C14TAL vesicles is due to the interaction with DNA; however, this phenomenon cannot be observed in C12TAB-SL vesicles. Agarose gel electrophoresis (AGE) results demonstrate that the electrostatic interaction between the two oppositely charged cationic and anionic surfactants is stronger than that between DNA and cationic surfactant, CnTAB (n = 12, 14, and 16). Not only is the dissociation of L(-) simply determined by the charge competition, but it also depends largely on the variations in the surface charge density as well as the cationic and anionic surfactant competing ability in geometry configuration of catanionic vesicles. The complicated interaction between DNA and catanionic vesicles induces the deformation of cationic vesicles. Our results should provide clear guidance for choosing more proper vectors for DNA delivery and gene therapy in cell experiments.

  14. Novel cationic dye and crosslinkable surfactant for DNA biophotonics

    NASA Astrophysics Data System (ADS)

    Johnson, Lewis E.; Latimer, Luke N.; Benight, Stephanie J.; Watanabe, Zachary H.; Elder, Delwin L.; Robinson, Bruce H.; Bartsch, Carrie M.; Heckman, Emily M.; Depotter, Griet; Clays, Koen

    2012-10-01

    Biopolymers such as DNA can be used as a host material for nonlinear optical dyes for photonic applications. In previous work by Heckman et al. (Proc. SPIE 6401, 640108-2), the chromophore Disperse Red 1 (DR1) was combined with CTMA-DNA (a water-insoluble DNA/surfactant complex) to produce an electro-optic waveguide modulator. However, DR1 does not bind strongly to DNA and has a low first hyperpolarizability (β). We have used theory-aided design to develop and synthesize a novel chromophore with strong affinity for DNA and higher β than DR1. We have also developed a surfactant containing a photocrosslinkable moiety that can be used to harden thin films of the DNA/surfactant/dye composite under ultraviolet light. The optical and thermal properties of these materials and outlook for device applications will be discussed.

  15. Impact of cationic surfactant on the self-assembly of sodium caseinate.

    PubMed

    Vinceković, Marko; Curlin, Marija; Jurašin, Darija

    2014-08-27

    The impact of a cationic surfactant, dodecylammonium chloride (DDACl), on the self-assembly of sodium caseinate (SC) has been investigated by light scattering, zeta potential, and rheological measurements as well as by microscopy (transmission electron and confocal laser scanning microscopy). In SC dilute solutions concentration-dependent self-assembly proceeds through the formation of spherical associates and their aggregation into elongated structures composed of connected spheres. DDACl interacts with SC via its hydrophilic and hydrophobic groups, inducing changes in SC self-assembled structures. These changes strongly depend on the surfactant aggregation states (monomeric or micellar) as well as concentration ratio of both components, leading to the formation of soluble and insoluble complexes of nano- to microdimensions. DDACl monomers interact with SC self-assembled entities in a different way compared to their micelles. Surfactant monomers form soluble complexes (similar to surfactant mixed micelles) at lower SC concentration but insoluble gelatinous complexes at higher SC concentration. At surfactant micellar concentration soluble complexes with casein chains wrapped around surfactant micelles are formed. This study suggests that the use of proper cationic surfactant concentration will allow modification and control of structural changes of SC self-assembled entities.

  16. ENVIRONMENTAL RESEARCH BRIEF: USE OF CATIONIC SURFACTANTS TO MODIFY AQUIFER MATERIALS TO REDUCE THE MOBILITY OF HYDROPHOBIC ORGANIC COMPOUNDS

    EPA Science Inventory

    Cationic surfactants can be used to modify surfaces of soils and subsurface materials to promote sorption of hydrophobic organic compounds (HOC) and retard their migration. For example, cationic surfactants could be injected into an aquifer downgradient from a source of HOC conta...

  17. The interaction of a model active pharmaceutical with cationic surfactant and the subsequent design of drug based ionic liquid surfactants.

    PubMed

    Qamar, Sara; Brown, Paul; Ferguson, Steven; Khan, Rafaqat Ali; Ismail, Bushra; Khan, Abdur Rahman; Sayed, Murtaza; Khan, Asad Muhammad

    2016-11-01

    Interactions of active pharmaceutical ingredients (API) with surfactants remain an important research area due to the need to improve drug delivery systems. In this study, UV-Visible spectrophotometry was used to investigate the interactions between a model low molecular weight hydrophilic drug sodium valproate (SV) and cationic surfactant cetyltrimethylammonium bromide (CTAB). Changes in the spectra of SV were observed in pre- and post-micellar concentrations of CTAB. The binding constant (Kb) values and the number of drug molecules encapsulated per micelle were calculated, which posed the possibility of mixed micelle formation and strong complexation between SV and CTAB. These results were compared to those of a novel room temperature surface active ionic liquid, which was synthesized by the removal of inorganic counterions from a 1:1 mixture of CTAB and SV. In this new compound the drug now constitutes a building block of the carrier and, as such, has considerably different surfactant properties to its building blocks. In addition, enhanced solubility in a range of solvents, including simulated gastric fluid, was observed. The study provides valuable experimental evidence concerning the performance of drug based surfactant ionic liquids and how their chemical manipulation, without altering the architecture of the API, leads to control of surfactant behavior and physicochemical properties. In turn, this should feed through to improved and controlled drug release rates and delivery mechanisms, and the prevention of precipitation or formation of polymorphs typical of crystalline form APIs.

  18. The interaction of a model active pharmaceutical with cationic surfactant and the subsequent design of drug based ionic liquid surfactants.

    PubMed

    Qamar, Sara; Brown, Paul; Ferguson, Steven; Khan, Rafaqat Ali; Ismail, Bushra; Khan, Abdur Rahman; Sayed, Murtaza; Khan, Asad Muhammad

    2016-11-01

    Interactions of active pharmaceutical ingredients (API) with surfactants remain an important research area due to the need to improve drug delivery systems. In this study, UV-Visible spectrophotometry was used to investigate the interactions between a model low molecular weight hydrophilic drug sodium valproate (SV) and cationic surfactant cetyltrimethylammonium bromide (CTAB). Changes in the spectra of SV were observed in pre- and post-micellar concentrations of CTAB. The binding constant (Kb) values and the number of drug molecules encapsulated per micelle were calculated, which posed the possibility of mixed micelle formation and strong complexation between SV and CTAB. These results were compared to those of a novel room temperature surface active ionic liquid, which was synthesized by the removal of inorganic counterions from a 1:1 mixture of CTAB and SV. In this new compound the drug now constitutes a building block of the carrier and, as such, has considerably different surfactant properties to its building blocks. In addition, enhanced solubility in a range of solvents, including simulated gastric fluid, was observed. The study provides valuable experimental evidence concerning the performance of drug based surfactant ionic liquids and how their chemical manipulation, without altering the architecture of the API, leads to control of surfactant behavior and physicochemical properties. In turn, this should feed through to improved and controlled drug release rates and delivery mechanisms, and the prevention of precipitation or formation of polymorphs typical of crystalline form APIs. PMID:27472069

  19. New ester based gemini surfactants: the effect of different cationic headgroups on micellization properties and viscosity of aqueous micellar solution.

    PubMed

    Bhadani, Avinash; Tani, Misako; Endo, Takeshi; Sakai, Kenichi; Abe, Masahiko; Sakai, Hideki

    2015-07-15

    A new series of ester functionalized cationic gemini surfactants having different cationic headgroups (i.e. piperidinium, pyrrolidinium, morpholinium and quaternary ammonium) have been synthesized and characterized using NMR and Mass spectroscopy. These new gemini surfactants were investigated for their micellization and viscosity properties using surface tension, conductivity, fluorescence and rheology thechniques. The physicochemical properties of the aqueous surfactant system were influenced by polarity, size and the nature of cationic headgroups as the surface, thermodynamic and viscosity properties of these gemini surfactants were found to be dependent on the type of cationic headgroup. The current research finding establishes the structure-property relationship of the surfactant molecule specifically taking into account the dominant role displayed by the nature of the cationic headgroup. PMID:26145125

  20. Shape control of mesoporous silica nanomaterials templated with dual cationic surfactants and their antibacterial activities.

    PubMed

    Hao, Nanjing; Chen, Xuan; Jayawardana, Kalana W; Wu, Bin; Sundhoro, Madanodaya; Yan, Mingdi

    2016-01-01

    Mesoporous silica nanomaterials of different shapes (film, platelet, sphere, rod) were synthesized simply by tuning the mole ratio of dual cationic surfactant templates, cetyltrimethylammonium bromide (CTAB) and tetrabutylammonium iodine (TBAI). The film showed the most potent antibacterial activity against mycobacteria. PMID:26364920

  1. Shape Control of Mesoporous Silica Nanomaterials Templated with Dual Cationic Surfactants and Their Antibacterial Activities

    PubMed Central

    Hao, Nanjing; Chen, Xuan; Jayawardana, Kalana W.; Wu, Bin; Sundhoro, Madanodaya; Yan, Mingdi

    2015-01-01

    Mesoporous silica nanomaterials of different shapes (film, platelet, sphere, rod) were synthesized simply by tuning the mole ratio of dual cationic surfactant templates, cetyltrimethylammonium bromide (CTAB) and tetrabutylammonium iodine (TBAI). The film showed the most potent antibacterial activities against mycobacteria. PMID:26364920

  2. A cationic surfactant assisted selective etching strategy to hollow mesoporous silica spheres.

    PubMed

    Fang, Xiaoliang; Chen, Cheng; Liu, Zhaohui; Liu, Pengxin; Zheng, Nanfeng

    2011-04-01

    Hollow mesoporous silica spheres have recently attracted increasing attention. However, effective synthesis of uniform hollow mesoporous spheres with controllable well-defined pore structures for fundamental research and practical applications has remained a significant challenge. In this work, a straightforward and effective "cationic surfactant assisted selective etching" synthetic strategy was developed for the preparation of high-quality hollow mesoporous silica spheres with either wormhole-like or oriented mesoporous shell. The as-prepared hollow mesoporous silica spheres have large surface area, high pore volume, and controllable structure parameters. Our experiments demonstrated that cationic surfactant plays critical roles in forming the hollow mesoporous structure. A formation mechanism involving the etching of solid SiO(2) accelerated by cationic surfactant followed by the redeposition of dissolved silica species directed by cationic surfactant is proposed. Furthermore, the strategy can be extended as a general strategy to transform silica-coated composite materials into yolk-shell structures with either wormhole-like or oriented mesoporous shell.

  3. Non-extraction flow injection determination of cationic surfactants using eriochrome black-T

    NASA Astrophysics Data System (ADS)

    Ensafi, Ali A.; Hemmateenejad, B.; Barzegar, S.

    2009-09-01

    A new, rapid, sensitive, non-extraction batch, and flow injection spectrophotometric method for the determination of cationic surfactants (CSs) such as cetyltrimethyl ammonium bromide (CTAB), tetra-n-butyl ammonium chloride (TBAC) and cetylpyridinium chloride (CPC) is proposed. The method is based on the interaction of cationic surfactants with eriochrome black-T to form an ion-association complex. This complex has strong absorbance at 708 nm. The effects of chemical parameters and FIA variables on the determination of cationic surfactants were studied in detail, especially for CTAB. Under optimum conditions, the two linear calibration ranges of the method are 3.0 × 10 -6 to 5.0 × 10 -3 mol L -1 CTAB, CPB and DTAB for the batch spectrophotometric method and 2.0 × 10 -6 to 2.0 × 10 -4 mol L -1 CTAB, CPB and TBC for the flow injection spectrophotometric method. The sample throughput was 35 ± 5 samples h -1 at room temperature. The relative standard deviations for 10 replicates of analysis of (2.0, 0.6 and 0.2) × 10 -4 mol L -1 CTAB were 1.2, 1.3, and 0.8%, respectively. In addition, the influence of potential interfering substances on the determination of cationic surfactants was studied. The proposed method is simple and rapid, using no toxic organic solvents. It was applied to the determination of trace CS in industrial wastewater with satisfactory results.

  4. Accurate assessment of the biodegradation of cationic surfactants in activated sludge reactors (OECD TG 303A).

    PubMed

    Geerts, Roy; van Ginkel, Cornelis G; Plugge, Caroline M

    2015-08-01

    The continuous-fed activated sludge test (OECD TG 303A) was used to predict the removal of cationic surfactants from wastewater in activated sludge plants. However, a method to differentiate between adsorption and biodegradation is not provided in these guidelines. Assessment of removal by biodegradation was possible with analysis of the surfactant present in mixed liquid suspended solids in combination with a simple equation. This equation was derived from the mass balance of the activated sludge unit in steady state. The removal by biodegradation of decylamine, tetradecylamine, octadecylamine, dioctadecylmethylamine and dioctadecyldimethylammonium chloride that have different capacities to adsorb was >99.9%, >99.9%, 98.2%, 94.2%, and 69.0%, respectively. The total removal of all five cationic surfactants from the influent was ≥98.8%. The removal of octadecylamine spiked at different influent concentrations indicated first order kinetics. PMID:25913361

  5. The interactions between cationic cellulose and Gemini surfactant in aqueous solution.

    PubMed

    Zhao, Shaojing; Cheng, Fa; Chen, Yu; Wei, Yuping

    2016-05-01

    Due to the extensive application of cationic cellulose in cosmetic, drug delivery and gene therapy, combining the improvement effect of surfactant-cellulose complexes, to investigate the properties of cellulose in aqueous solution is an important topic from both scientific and technical views. In this study, the phase behavior, solution properties and microstructure of Gemini surfactant sodium 5-nonyl-2-(4-(4-nonyl-2-sulfonatophenoxy)butoxy)phenyl sulfite (9-4-9)/cationic cellulose (JR400, the ammonium groups are directly bonded to the hydroxyethyl substituent with a degree substitution of 0.37) mixture was investigated using turbidity, fluorescence spectrophotometer and shear rheology techniques. As a control, the interaction of corresponding monovalent surfactant, sodium 2-ethoxy-5-nonylbenzenesulfonate (9-2) with JR400 in aqueous solution was also studied. Experimental results showed that 9-4-9/JR400 mixture has lower critical aggregation concentration (CAC) and critical micelle concentration (CMC) (about one order of magnitude) than 9-2/JR400 mixture. A low concentration of Gemini surfactant 9-4-9 appeared to induce an obvious micropolarity and viscosity value variation of the mixture, while these effects required a high concentration of corresponding monovalent one. Furthermore, dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements illuminated the formation and collapse procedure of network structure of the 9-4-9/JR400 mixture, which resulted in the increase and decrease of viscosity. These results suggest that the molecular structure of the surfactant has a great effect on its interaction with cationic cellulose. Moreover, the Gemini surfactant/cationic cellulose mixture may be used as a potencial stimuli-responsive drug delivery vector which not only load hydrophilic drugs, but also deliver hydrophobic substances. PMID:26876997

  6. Effect of cationic/anionic organic surfactants on evaporation induced self assembled tin oxide nanostructured films

    NASA Astrophysics Data System (ADS)

    Khun Khun, Kamalpreet; Mahajan, Aman; Bedi, R. K.

    2011-01-01

    Tin oxide nanostructures with well defined morphologies have been obtained through an evaporation induced self assembly process. The technique has been employed using an ultrasonic nebulizer for production of aersol and its subsequent deposition onto a heated glass substrate. The precursor used for aersol production was modified by introducing cationic and anionic surfactants namely cetyl trimethyl ammonium bromide and sodium dodecyl sulphate respectively. The effect of surfactants on the structural, electrical and optical properties of self assembled tin oxide nanostructures were investigated by using X-ray diffraction, field emission scanning electroscope microscopy, two probe technique and photoluminiscence studies. The results reveal that high concentration of surfactants in the precursor solution leads to reduction in crystallite size with significant changes in the morphology of tin oxide nanostructures. Photoluminiscence studies of the nanostructures show emissions in the visible region which exhibit marked changes in the intensities upon variation of surfactants in the precursor solutions.

  7. Preparation, Physicochemical Properties, and Transfection Activities of Tartaric Acid-Based Cationic Lipids as Effective Nonviral Gene Delivery Vectors.

    PubMed

    Wan, Ning; Jia, Yi-Yang; Hou, Yi-Lin; Ma, Xi-Xi; He, Yong-Sheng; Li, Chen; Zhou, Si-Yuan; Zhang, Bang-Le

    2016-07-01

    In this work two novel cationic lipids using natural tartaric acid as linking backbone were synthesized. These cationic lipids were simply constructed by tartaric acid backbone using head group 6-aminocaproic acid and saturated hydrocarbon chains dodecanol (T-C12-AH) or hexadecanol (T-C16-AH). The physicochemical properties, gel electrophoresis, transfection activities, and cytotoxicity of cationic liposomes were tested. The optimum formulation for T-C12-AH and T-C16-AH was at cationic lipid/dioleoylphosphatidylethanolamine (DOPE) molar ratio of 1 : 0.5 and 1 : 2, respectively, and N/P charge molar ratio of 1 : 1 and 1 : 1, respectively. Under optimized conditions, T-C12-AH and T-C16-AH showed effective gene transfection capabilities, superior or comparable to that of commercially available transfecting reagent 3β-[N-(N',N'-dimethylaminoethyl)carbamoyl]cholesterol (DC-Chol) and N-[2,3-dioleoyloxypropyl]-N,N,N-trimethylammonium chloride (DOTAP). The results demonstrated that the two novel tartaric acid-based cationic lipids exhibited low toxicity and efficient transfection performance, offering an excellent prospect as nonviral vectors for gene delivery. PMID:27118165

  8. Investigation of the electrokinetic properties of paraffin suspension. 2. In cationic and anionic surfactant solutions.

    PubMed

    Chibowski, Emil; Wiacek, Agnieszka; Holysz, Lucyna; Terpilowski, Konrad

    2005-08-16

    Electrical phenomena at nonionogenic hydrophobic surfaces (solid or liquid) in water, electrolyte, and/or surfactant solutions still attract research. In part 1 of this paper we described the electrokinetic behavior of paraffin wax suspension in water and electrolyte solutions (NaCl or LaCl3). On the basis of the latest data of water structure near hydrophobic surfaces it was concluded that immobilized water dipoles at the interface can play an essential role in the zeta potential formation. In this paper were investigated the zeta potentials of paraffin wax in cationic surfactants cetyltrimethylammonium bromide, C16H33(CH3)3NBr, and octadecyltrimethylammonium chloride, C18H37(CH3)3NCl, and anionic surfactant sodium dodecyl sulfate, C12H25SO4Na. Also changes in wettability of the paraffin surface due to the surfactant's adsorption were studied via wetting contact angle measurements and calculation of the surface free energy. It was concluded that at a low surfactant concentration (10(-6) M) the water dipole structure still contributes to the zeta potential, but at a higher one the zeta potential is determined by the surfactant molecules' adsorption. A special role of OH- ions is also clearly seen. Moreover, a functional relationship was found between the surface free energy of the surfactant-covered paraffin surface and the zeta potential.

  9. Liquid-Liquid Interface Study of Hydrocarbons, Alcohols, and Cationic Surfactants with Water

    NASA Astrophysics Data System (ADS)

    Singh, Man; Matsuoka, Hideki

    Molecular interaction dynamics at liquid-liquid interface (LLI), involved nondispersive solution as compared with the interaction in bulk phase. Thereby, interfacial tension (IFT, mN/m) of LLI for four saturated hydrocarbons, six alcohols, and three cationic surfactants are reported at 298.15 K. The pentane, hexane, heptane, octane hydrocarbons and pentanol, hexanol, heptanol, 1-octanol, 2-octanol, and 1-decanol alcohols were used and IFT data were compared with 4 mm kg-1 dodecyltrimethylammoniumbromide (DTAB), trimethylsulfoxoniumiodide (TMSOI), methyltrioctylammoniumchloride (MTOAC) surfactants studied in benzene-water LLI. The IFT data are noted as hydrocarbons > DTAB > TMSOI > alcohols > MTOAC. The hydrocarbons and alcohols decreased IFT within 16 to 49% and 87 to 92%, respectively, whereas the surfactants within 78.3 to 95.9%. The alcohols developed interaction similar to surfactants and are denoted as nonionic surfactants for making mixtures of low IFT with hydrophilic and hydrophobic interactions to the level of the surfactants. The pentanol and MTOAC caused similar decrease in IFT so the pentanol developed the hydrophilic and hydrophobic interactions of the strength of MTOAC. Comparatively, the hydrocarbons showed lower decrease but the octane showed 49% decrease in IFT. Thus, the hydrocarbon with longer alkyl chain and the alcohol with shorter behave as good surfactants. The hydrocarbons with inductive effect on sigma bond between carbon atoms in alkyl chain also weakened the IFT and influenced the hydrophobic interactions. The MTOAC with four octyl units reduced 96% IFT so inductive effects monitor LLI dynamics.

  10. Hydrogels of sodium alginate in cationic surfactants: Surfactant dependent modulation of encapsulation/release toward Ibuprofen.

    PubMed

    Jabeen, Suraya; Chat, Oyais Ahmad; Maswal, Masrat; Ashraf, Uzma; Rather, Ghulam Mohammad; Dar, Aijaz Ahmad

    2015-11-20

    The interaction of cetyltrimethylammoium bromide (CTAB) and its gemini homologue (butanediyl-1,4-bis (dimethylcetylammonium bromide), 16-4-16 with biocompatible polymer sodium alginate (SA) has been investigated in aqueous medium. Addition of K2CO3 influences viscoelastic properties of surfactant impregnated SA via competition between electrostatic and hydrophobic interactions. Viscosity of these polymer-surfactant systems increases with increase in concentration of K2CO3, and a cryogel is formed at about 0.5M K2CO3 concentration. The thermal stability of gel (5% SA+0.5M K2CO3) decreases with increase in surfactant concentration, a minimum is observed with increase in 16-4-16 concentration. The impact of surfactant addition on the alginate structure vis-à-vis its drug loading capability and release thereof was studied using Ibuprofen (IBU) as the model drug. The hydrogel with 16-4-16 exhibits higher IBU encapsulation and faster release in comparison to the one containing CTAB. This higher encapsulation-cum-faster release capability has been related to micelle mediated solubilization and greater porosity of the hydrogel with gemini surfactant.

  11. Solubilization of two organic dyes by cationic ester-containing gemini surfactants.

    PubMed

    Tehrani-Bagha, A R; Singh, R G; Holmberg, K

    2012-06-15

    Solubilization of two different types of organic dyes, Quinizarin with an anthraquinone structure and Sudan I with an azo structure, has been studied in aqueous solutions of a series of cationic gemini surfactants and of a conventional monomeric cationic surfactant, dodecyltrimethylammonium bromide (DTAB). Surfactant concentrations both above and below the critical micelle concentration were used. The concentration of solubilized dye at equilibrium was determined from the absorbance of the solution at λ(max) with the aid of a calibration curve. The solubilization power of the gemini surfactants was higher than that of DTAB and increased with increasing alkyl chain length. An increase in length of the spacer unit resulted in increased solubilization power while a hydroxyl group in the spacer did not have much effect. Ester bonds in the alkyl chains reduced the solubilization power with respect to both dyes. A comparison between the absorbance spectra of the dyes in micellar solution with spectra in a range of solvents of different polarity indicated that the dye is situated in a relatively polar environment. One may therefore assume that the dye is located just below the head group region of the micelle. Attractive π-cation interactions may play a role for orienting the dye to the outer region of the micelle.

  12. Interaction of cationic surfactants with iron and sodium montmorillonite suspensions

    SciTech Connect

    Chen, G.; Han, B.; Yan, H.

    1998-05-15

    Calorimetry, static technique, and X-ray diffraction (XRD) analysis were employed to study the adsorption of cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) on Fe-montmorillonite and Na-montmorillonite suspensions. The results show that the process of adsorption is exothermic and that the type of clay and the alkyl chain length of surfactant affect the amount of adsorption and the enthalpy of adsorption significantly but that the effect of temperature is very limited in the temperature range studied. The magnitudes of adsorption amount and adsorption enthalpy follow the order Na-montmorillonite > Fe-montmorillonite, CTAB > DTAB. The basal spacings determined by X-ray powder diffraction indicate that the CTAB adsorbed between the clay interlayers in a bilayer arrangement, while the DTAB formed bilayers or monolayers at saturation adsorption between the Na-montmorillonite and Fe-montmorillonite interlayers, respectively. The adsorption mechanism is also discussed on the basis of the experimental data.

  13. Effects of Surfactants on the Improvement of Sludge Dewaterability Using Cationic Flocculants

    PubMed Central

    Zhai, Jun; Teng, Houkai; Zhao, Chun; Zhao, Chuanliang; Liao, Yong

    2014-01-01

    The effects of the cationic surfactant (cationic cetyl trimethyl ammonium bromide, CTAB) on the improvement of the sludge dewaterability using the cationic flocculant (cationic polyacrylamide, CPAM) were analyzed. Residual turbidity of supernatant, dry solid (DS) content, extracellular polymeric substances (EPS), specific resistance to filtration (SRF), zeta potential, floc size, and settling rate were investigated, respectively. The result showed that the CTAB positively affected the sludge conditioning and dewatering. Compared to not using surfactant, the DS and the settling rate increased by 8%–21.2% and 9.2%–15.1%, respectively, at 40 mg·L−1 CPAM, 10×10−3 mg·L−1 CTAB, and pH 3. The residual turbidities of the supernatant and SRF were reduced by 14.6%–31.1% and 6.9%–7.8% compared with turbidities and SRF without surfactant. Furthermore, the release of sludge EPS, the increases in size of the sludge flocs, and the sludge settling rate were found to be the main reasons for the CTAB improvement of sludge dewatering performance. PMID:25347394

  14. Synthesis of high quality MCM-48 with binary cationic-nonionic surfactants.

    PubMed

    Zhao, Wei; Li, Quanzhi; Wang, Lina; Chu, Jinglong; Qu, Jinkui; Li, Shaohua; Qi, Tao

    2010-05-18

    Highly ordered MCM-48 was synthesized in the hydrothermal system of a mixture of cationic cetyltrimethylammonium bromide (CTAB) and nonionic poly(ethylene glycol) monooctylphenyl ether (Tx-100) using water glass as the silicon source. The effect of various factors, such as the amount of surfactant, CTAB/Tx-100, Si source, crystallization temperature, and crystallization time, on the synthesis were discussed in detail. The local effective surfactant packing parameter theory and the charge balance theory were used to explain the reason that various factors can affect the product structure reasonably. Especially, the role of Tx-100 was expounded. The optimum synthesis conditions for MCM-48 were obtained.

  15. Interaction of Sodium Hyaluronate with a Biocompatible Cationic Surfactant from Lysine: A Binding Study.

    PubMed

    Bračič, Matej; Hansson, Per; Pérez, Lourdes; Zemljič, Lidija F; Kogej, Ksenija

    2015-11-10

    Mixtures of natural and biodegradable surfactants and ionic polysaccharides have attracted considerable research interest in recent years because they prosper as antimicrobial materials for medical applications. In the present work, interactions between the lysine-derived biocompatible cationic surfactant N(ε)-myristoyl-lysine methyl ester, abbreviated as MKM, and the sodium salt of hyaluronic acid (NaHA) are investigated in aqueous media by potentiometric titrations using the surfactant-sensitive electrode and pyrene-based fluorescence spectroscopy. The critical micelle concentration in pure surfactant solutions and the critical association concentration in the presence of NaHA are determined based on their dependence on the added electrolyte (NaCl) concentration. The equilibrium between the protonated (charged) and deprotonated (neutral) forms of MKM is proposed to explain the anomalous binding isotherms observed in the presence of the polyelectrolyte. The explanation is supported by theoretical model calculations of the mixed-micelle equilibrium and the competitive binding of the two MKM forms to the surface of the electrode membrane. It is suggested that the presence of even small amounts of the deprotonated form can strongly influence the measured electrode response. Such ionic-nonionic surfactant mixtures are a special case of mixed surfactant systems where the amount of the nonionic component cannot be varied independently as was the case for some of the earlier studies.

  16. Aggregation behaviors of gelatin with cationic gemini surfactant at air/water interface.

    PubMed

    Wu, Dan; Xu, Guiying; Feng, Yujun; Li, Yiming

    2007-03-10

    The dilational rheological properties of gelatin with cationic gemini surfactant 1,2-ethane bis(dimethyl dodecyl ammonium bromide) (C(12)C(2)C(12)) at air/water interface were investigated using oscillating barriers method at low frequency (0.005-0.1 Hz), which was compared with single-chain surfactant dodecyltrimethyl ammonium bromide (DTAB). The results indicate that the maximum dilational modulus and the film stability of gelatin-C(12)C(2)C(12) are higher than those of gelatin-DTAB. At high concentration of C(12)C(2)C(12) or DTAB, the dilational modulus of gelatin-surfactant system becomes close to that corresponding to pure surfactant, suggesting gelatin at interface is replaced by surfactant. This replacement is also observed by surface tension measurement. However, it is found that gelatin-C(12)C(2)C(12) system has two obvious breaks but gelatin-DTAB has not in surface tension isotherms. These phenomena are ascribed to the double charges and strong hydrophobicity of C(12)C(2)C(12). Based on these experimental results, a mechanism of gelatin-surfactant interaction at air/water interface is proposed.

  17. Study of monoprotic acid-base equilibria in aqueous micellar solutions of nonionic surfactants using spectrophotometry and chemometrics.

    PubMed

    Babamoradi, Hamid; Abdollahi, Hamid

    2015-10-01

    Many studies have shown the distribution of solutes between aqueous phase and micellar pseudo-phase in aqueous micellar solutions. However, spectrophotometric studies of acid-base equilibria in these media do not confirm such distribution because of the collinearity between concentrations of chemical species in the two phases. The collinearity causes the number of detected species to be equal to the number of species in a homogenous solution that automatically misinterpreted as homogeneity of micellar solutions, therefore the collinearity is often neglected. This interpretation is in contradiction to the distribution theory in micellar media that must be avoided. Acid-base equilibrium of an indicator was studied in aqueous micellar solutions of a nonionic surfactant to address the collinearity using UV/Visible spectrophotometry. Simultaneous analysis (matrix augmentation) of the equilibrium and solvation data was applied to eliminate the collinearity from the equilibrium data. A model was then suggested for the equilibrium that was fitted to the augmented data to estimate distribution coefficients of the species between the two phases. Moreover, complete resolution of concentration and spectral profiles of species in each phase was achieved.

  18. Elucidating the higher stability of vanadium(V) cations in mixed acid based redox flow battery electrolytes

    NASA Astrophysics Data System (ADS)

    Vijayakumar, M.; Wang, Wei; Nie, Zimin; Sprenkle, Vincent; Hu, JianZhi

    2013-11-01

    The vanadium(V) cation structures in mixed acid based electrolyte solution were analyzed by density functional theory (DFT) based computational modeling and 51V and 35Cl nuclear magnetic resonance (NMR) spectroscopy. The vanadium(V) cation exists as di-nuclear [V2O3Cl2·6H2O]2+ compound at higher vanadium concentrations (≥1.75 M). In particular, at high temperatures (>295 K) this di-nuclear compound undergoes ligand exchange process with nearby solvent chlorine molecule and forms chlorine bonded [V2O3Cl·6H2O]2+ compound. This chlorine bonded [V2O3Cl2·6H2O]2+ compound might be resistant to the de-protonation reaction which is the initial step in the precipitation reaction in vanadium based electrolyte solutions. The combined theoretical and experimental approach reveals that formation of chlorine bonded [V2O3Cl2·6H2O]2+ compound might be central to the observed higher thermal stability of mixed acid based vanadium(V) electrolyte solutions.

  19. Aggregation behavior of a tetrameric cationic surfactant in aqueous solution.

    PubMed

    Hou, Yanbo; Han, Yuchun; Deng, Manli; Xiang, Junfen; Wang, Yilin

    2010-01-01

    A star-shaped tetrameric quaternary ammonium surfactant PATC, which has four hydrophobic chains and charged hydrophilic headgroups connected by amide-type spacer group, has been synthesized in this work. Surface tension, electrical conductivity, ITC, DLS, and NMR have been used to investigate the relationship between its chemical structure and its aggregation properties. Interestingly, a large size distribution around 75 nm is observed below the critical micelle concentration (cmc) of PATC, and the large size distribution starts to decrease beyond the cmc and finally transfers to a small size distribution. It is proved that the large size premicellar aggregates may display network-like structure, and the size decrease beyond the cmc is the transition of the network-like aggregates to micelles. The possible reason is that intramolecular electrostatic repulsion among the charged headgroups below the cmc leads to a star-shaped molecular configuration, which may form the network-like aggregates through intermolecular hydrophobic interaction between hydrocarbon chains, while the hydrophobic effect becomes strong enough to turn the molecular configuration into pyramid-like shape beyond the cmc, which make the transition of network-like aggregates to micelles available. PMID:19947615

  20. Cationic surfactants for control of fresh- and saltwater mollusks in nuclear cooling systems

    SciTech Connect

    Post, R.M.; Mallen, E.; Lehmann, F.

    1991-11-01

    One result of the release of the US Nuclear Regulatory Commission's Generic Letter 89-13, Service Water Problems Affecting Safety-Related Equipment, was the heightened awareness of the nuclear industry to the problems of macrofouling in heat exchange systems. The principal mollusk species that contribute to freshwater macrofouling problems are Asiatic Clam (southern United States) and Zebra Mussel (Great Lakes). The predominant saltwater fouling mollusks are the Blue Mussel (Pacific, northern Atlantic), Ribbed Mussel (southern Atlantic, Gulf Coast), and American Oyster (Atlantic, Gulf Coast). The nuclear community's awareness of macrofouling problems and the ineffectiveness of intermittent chlorination programs have led to the development of several chemical control technologies for eliminating macrofouling organism infestation. One technology that has proven effective for the control of macrofouling organisms is the periodic addition of a combination of two cationic charged surfactants, specifically, alkyldimethylbenzylammonium chloride (QUAT) and dodecyl guanidine hydrochloride (DGH). Experience with the cationic surfactants at several nuclear power plants is reported.

  1. Comparison between the interactions of the cationic surfactant DODAB with xanthan and galactomannan.

    PubMed

    Kaminski, Gabriel A T; Sierakowski, Maria Rita; Pontarolo, Roberto; de Freitas, Rilton Alves

    2015-01-22

    The interactions of the cationic surfactant DODAB with anionic xanthan (XAN) and nonionic galactomannan (GMC) polysaccharides in solution were investigated using tensiometry, differential scanning microcalorimetry (μ-DSC), zeta potential and dynamic light scattering (DLS) techniques and by the calculated thermodynamic parameters of ΔG(ves)(0), ΔG(ads)(0), Γ(max) and a(min). The surfactant formed large unilamellar vesicles (LUV) that aggregated with both the polymers in solution. Increasing DODAB concentrations resulted in greater and greater DODAB-XAN aggregates, high turbidity and even precipitation, while DODAB-GMC aggregates remained equal sized, clear solution and no precipitation observed. Further addition of DODAB to XAN solution was able to resuspend the precipitates. The interactions with both polysaccharides resulted in a more spontaneous adsorption of the DODAB-polymer aggregates at the air/solution interface with lower surfactant population.

  2. Nano ZnO structures synthesized in presence of anionic and cationic surfactant under hydrothermal process

    NASA Astrophysics Data System (ADS)

    Thilagavathi, T.; Geetha, D.

    2012-12-01

    Uniform ZnO nano structures are synthesized in the presence of anionic surfactant, sodium dodecyl benzene sulfonate (SDBS) and cationic surfactant, cetyl tri methyl ammonium bromide (CTAB) at 100 °C using NaOH as the reactant. The particle size, morphology and structure of the nano ZnO particles are collected by X-ray diffraction, scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectra. Rod and cone shaped ZnO nano structure is observed. It may vary in morphology from pure ZnO structure due to the presence of surfactants. The results show that there is an extrinsic relation between the morphology of the samples. Based on the relation, we proposed that there might be two kinds of interactions between SDBS and CTAB with ZnO particles, i.e., inter- and intra-interactions.

  3. Anaerobic biodegradability and inhibitory effects of some anionic and cationic surfactants.

    PubMed

    Pérez-Armendáriz, Beatriz; Moreno, Yésica Mayett; Monroy-Hermosillo, Oscar; Guyot, Jean Pierre; González, Rosa O

    2010-09-01

    The anaerobic biodegradability and inhibitory effects on the methane production of three different surfactants, two anionic: sodium lauryl sulfate (SLS) and sodium dodecylbenzene sulfonate (SDBS), and a cationic surfactant: trialkyl-methylammonium chloride (TMAC), were evaluated with two different anaerobic sludges, granular and flocculent. Five different concentrations of the surfactants, 5, 50, 100, 250 and 500 mg/L, were tested. SLS was biodegraded at concentrations of 5, 50 and 100 mg/L with flocculent sludge and at 100 and 250 mg/L with granular sludge. However an inhibitory effect on methane production was observed in both sludges at 500 mg/L. The results indicate that SDBS was not biodegradable under anoxic conditions. TMAC was slightly degraded 50 and 100 mg/L with the flocculent sludge, and from 100 to 500 mg/L with the granular sludge.

  4. Mesoporous MFI zeolites by microwave induced assembly between sulfonic acid functionalized MFI zeolite nanoparticles and alkyltrimethylammonium cationic surfactants.

    PubMed

    Jin, Hailian; Ansari, Mohd Bismillah; Park, Sang-Eon

    2011-07-14

    Mesoporous MFI zeolites (ZSM-5, TS-1, S-1) having intracrystalline mesoporosity within zeolite crystals were synthesized by microwave induced assembly through the ionic interaction between the sulfonic acid functionalized MFI zeolite nanoparticles and alkyltrimethylammonium cationic surfactants.

  5. Superamphiphilic nanocontainers based on the resorcinarene - Cationic surfactant system: Synergetic self-assembling behavior

    NASA Astrophysics Data System (ADS)

    Gaynanova, Gulnara A.; Bekmukhametova, Alina M.; Kashapov, Ruslan R.; Ziganshina, Albina Yu.; Zakharova, Lucia Ya.

    2016-05-01

    Self-organization in the mixed system based on water-soluble aminomethylated calix[4]arene with sulfonatoethyl groups at the lower rim and classical cationic surfactant cetyltrimethylammonium bromide has been studied by the methods of tensiometry, conductometry, spectrophotometry, dynamic and electrophoretic light scattering. The values of the critical association concentration, the size and zeta potential values, and the solubilization capacity of mixed aggregates toward the hydrophobic probe (Sudan I) were determined.

  6. Aquatic toxicity and biodegradability of advanced cationic surfactant APA-22 compatible with the aquatic environment.

    PubMed

    Yamane, Masayuki; Toyo, Takamasa; Inoue, Katsuhisa; Sakai, Takaya; Kaneko, Youhei; Nishiyama, Naohiro

    2008-01-01

    Cationic surfactant is a chemical substance used in hair conditioner, fabric softener and other household products. By investigating the relationship between the aquatic toxicity and the chemical structures of two types of mono alkyl cationic surfactants, alkyl trimethylammonium salts and alkyl dimethylamine salts, we have found that the C22 alkyl chain length is effective to reduce the toxicity. Besides, we have recognized that the amidopropyl functional group contributes to the enhanced biodegradability by investigating the biodegradation trend of (alkylamidopropyl)dimethylamine salt (alkyl chain length: C18). Based on these findings, we have developed mono alkyl cationic surfactant called APA-22, N-[3-(dimethylamino)propyl]docosanamide salt. APA-22 is formed by the C22 alkyl chain, amidopropyl functional group and di-methyltertiary amine group. We evaluated the aerobic and anaerobic biodegradability of APA-22 by two standard methods (OECD Test Guideline 301B and ECETOC technical document No.28) and found that this substance was degraded rapidly in both conditions. The toxicity to algae, invertebrate and fish of this substance are evaluated by using OECD Test Guideline 201, 202 and 203, respectively. All acute toxicity values are >1 mg/L, which indicates that environmental toxicity of this substance is relatively less toxic to aquatic organism. In addition, we estimated the biodegradation pathway of APA-22 and observed the complete disappearance of APA-22 and its intermediates during the test periods. Based on the environmental data provided above, we concluded that APA22 is more compatible with the aquatic environment compared to other cationic surfactants with mono long alkyl chain.

  7. Morphological and nanomechanical behavior of supported lipid bilayers on addition of cationic surfactants.

    PubMed

    Lima, Lia M C; Giannotti, Marina I; Redondo-Morata, Lorena; Vale, M Luísa C; Marques, Eduardo F; Sanz, Fausto

    2013-07-30

    The addition of surfactants to lipid bilayers is important for the modulation of lipid bilayer properties (e.g., in protein reconstitution and development of nonviral gene delivery vehicles) and to provide insight on the properties of natural biomembranes. In this work, the thermal behavior, organization, and nanomechanical stability of model cationic lipid-surfactant bilayers have been investigated. Two different cationic surfactants, hexadecyltrimethylammonium bromide (CTAB) and a novel derivative of the amino acid serine (Ser16TFAc), have been added (up to 50 mol %) to both liposomes and supported lipid bilayers (SLBs) composed by the zwitterionic phospholipid DPPC. The thermal phase behavior of mixed liposomes has been probed by differential scanning calorimetry (DSC), and the morphology and nanomechanical properties of mixed SLBs by atomic force microscopy-based force spectroscopy (AFM-FS). Although DSC thermograms show different results for the two mixed liposomes, when both are deposited on mica substrates similar trends on the morphology and the mechanical response of the lipid-surfactant bilayers are observed. DSC thermograms indicate microdomain formation in both systems, but while CTAB decreases the degree of organization on the liposome bilayer, Ser16TFAc ultimately induces the opposite effect. Regarding the AFM-FS studies, they show that microphase segregation occurs for these systems and that the effect is dependent on the surfactant content. In both SLB systems, different microdomains characterized by their height and breakthrough force Fb are formed. The molecular organization and composition is critically discussed in the light of our experimental results and literature data on similar lipid-surfactant systems. PMID:23782267

  8. Solubilization of octane in cationic surfactant-anionic polymer complexes: effect of polymer concentration and temperature.

    PubMed

    Zhang, Hui; Deng, Lingli; Zeeb, Benjamin; Weiss, Jochen

    2015-07-15

    Polymers may alter the ability of oppositely charged surfactant micelles to solubilize hydrophobic molecules depending on surfactant-polymer interactions. This study was conducted to investigate the effects of polymer concentration and temperature on the solubilization thermodynamics of an octane oil-in-water emulsion in mixtures of an anionic polymer (carboxymethyl cellulose) and cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles using isothermal titration calorimetry (ITC). Results showed that the CTAB binding capacity of carboxymethyl cellulose increased with increasing temperature from 301 to 323 K, and correspondingly the thermodynamic behavior of octane solubilization in CTAB micelles, either in the absence or presence of polymer, was found to depend on temperature. The addition of carboxymethyl cellulose caused the solubilization in CTAB micelles to be less endothermic, and increased the solubilization capacity. Based on the phase separation model, the solubilization was suggested to be mainly driven by enthalpy gains. Results suggest that increasing concentrations of the anionic polymer gave rise to a larger Gibbs energy decrease and a larger unfavorable entropy increase for octane solubilization in cationic surfactant micelles.

  9. Solubilization of octane in cationic surfactant-anionic polymer complexes: Effect of ionic strength.

    PubMed

    Zhang, Hui; Deng, Lingli; Sun, Ping; Que, Fei; Weiss, Jochen

    2016-01-01

    Polymers may alter the ability of oppositely charged surfactant micelles to solubilize hydrophobic molecules depending on surfactant-polymer interactions. This study was conducted to investigate the effect of ionic strength on the solubilization thermodynamics of an octane oil-in-water emulsion in mixtures of an anionic polymer (carboxymethyl cellulose) and cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles using isothermal titration calorimetry (ITC). Results indicated that the CTAB binding capacity of carboxymethyl cellulose increased with increasing NaCl concentrations up to 100 mM, and the thermodynamic behavior of octane solubilization in CTAB micelles, either in the absence or presence of polymer, was found to have a strong dependence on ionic strength. The increasing ionic strength caused the solubilization in CTAB micelles to be less endothermic or even exothermic, but increased the solubilization capacity. Based on the phase separation model, the solubilization was suggested to be driven by enthalpy. It is indicated that increasing ionic strength gave rise to a larger Gibbs energy decrease but a smaller unfavorable entropy increase for octane solubilization in cationic surfactant micelles.

  10. Mode changes associated with oil droplet movement in solutions of gemini cationic surfactants.

    PubMed

    Banno, Taisuke; Miura, Shingo; Kuroha, Rie; Toyota, Taro

    2013-06-25

    Micrometer-sized self-propelled oil droplets in nonequilibrium systems have attracted much attention, since they form stable emulsions composed of oil, water, and surfactant which represent a primitive type of inanimate chemical machinery. In this work, we examined means of controlling the movement of oil droplets by studying the dynamics of n-heptyloxybenzaldehyde droplets in phosphate buffers containing alkanediyl-α,ω-bis(N-dodecyl-N,N-dimethylammonium bromide) (nG12) with either tetramethylene (4G12), octaethylene (8G12), or dodecamethylene (12G12) chains in the linker moiety. Significant differences in droplet dynamics were observed to be induced by changes in the linker structure of these gemini cationic surfactants. In a phosphate buffer containing 30 mM 4G12, self-propelled motion of droplets concurrent with the formation of molecular aggregates on their surfaces was observed, whereas the fusion of oil droplets was evident in both 8G12 and 12G12 solutions. We also determined that the surface activities and the extent of molecular self-assembly of the surfactants in phosphate buffer were strongly influenced by the alkyl chain length in the linker moiety. We therefore conclude that the surface activities of the gemini cationic surfactant have important effects on the oil-water interfacial tension of oil droplets and the formation of molecular aggregates and that both of these factors induce the unique movement of the droplets.

  11. Adsorption of a cationic surfactant by a magsorbent based on magnetic alginate beads.

    PubMed

    Obeid, Layaly; El Kolli, Nadia; Dali, Noëlle; Talbot, Delphine; Abramson, Sébastien; Welschbillig, Mathias; Cabuil, Valérie; Bée, Agnès

    2014-10-15

    Adsorption of cetylpyridinium chloride (CPC), a cationic surfactant, by magnetic alginate beads (MagAlgbeads) was investigated. The magnetic adsorbent (called magsorbent) was prepared by encapsulation of magnetic functionalized nanoparticles in an alginate gel. The influence on CPC adsorption of several parameters such as contact time, pH and initial surfactant concentration was studied. The equilibrium isotherm shows that adsorption occurs through both electrostatic interactions with charge neutralization of the carboxylate groups of the beads and hydrophobic interactions inducing the formation of surfactant aggregates in the beads. The dosage of calcium ions released in the solution turns out to be a useful tool for understanding the adsorption mechanisms. Adsorption is accompanied by a shrinking of the beads that corresponds to a 45% reduction of the volume. Adsorption kinetic experiments show that equilibrium time is strongly dependent on the surfactant concentration, which monitors the nature of the interactions. On the other hand, since the pH affects the ionization state of adsorption sites, adsorption depends on the pH solution, maximum adsorption being obtained in a large pH range (3.2-12) in agreement with the pKa value of alginate (pKa=3.4-4.2). Finally, due to the formation of micelle-like surfactants aggregates in the magnetic alginate beads, they could be used as a new efficient magsorbent for hydrophobic pollutants. PMID:25086393

  12. Cationic gemini surfactants with cleavable spacer: chemical hydrolysis, biodegradation, and toxicity.

    PubMed

    Tehrani-Bagha, A R; Holmberg, K; van Ginkel, C G; Kean, M

    2015-07-01

    The paper describes synthesis and characterization of a new type of cationic gemini surfactant, which has dodecyl tails and a spacer that contains an ester bond. The nomenclature used to describe the structure is 12Q2OCO1Q12, with Q being a quaternary ammonium group and the numbers indicating the number of methylene or methyl groups. Due to the close proximity to the two quaternary ammonium groups, the ester bond is very stable on the acid side and very labile already at slightly alkaline conditions. The hydrolysis products are two single chain surfactants (i.e. 12Q2OH and 12Q1COOH) which are less surface active than the intact gemini surfactant. 12Q2OCO1Q12 was found to be readily biodegradable, i.e. it gave more than 60% biodegradation after 28 days. This is interesting because similar gemini surfactants but with ester bonds in the tails instead of the spacer, have previously been found not to be readily biodegradable. The gemini surfactant was found to be toxic to aquatic organisms (ErC50 value of 0.27 mg/l), although less toxic than the two hydrolysis products.

  13. Mesomorphic complexes of DNA with the mixtures of a cationic surfactant and a neutral lipid.

    PubMed

    Hsu, Wei-Long; Chen, Hsin-Lung; Liou, Willisa; Lin, Hsien-Kuang; Liu, Wen-Liang

    2005-10-11

    Polyanionic DNA binds to cationic lipids to form electrostatic complexes exhibiting rich self-assembled structures. These types of complexes have been considered as a nonviral carrier in gene therapy and as a template for nanostructure construction. For the latter application where biocompatibility is not the key issue, replacement of cationic lipid by cationic surfactant is advantageous due to the wide availability of surfactant. Here we report the self-assembly behavior of the complexes of DNA with a cationic surfactant, dodecyltrimethylammonium bromide (DTAB), mixed with a neutral lipid, dioleoylphosphatidylethanolamine (DOPE), in fully hydrated state as a function of DTAB-to-DNA base pair molar ratio (x), DOPE-to-DTAB molar ratio (m) and temperature. The binary complexes of DNA with DTAB microphase separated to form hydrophilic and hydrophobic domains without long-range order. Incorporating DOPE into the complexes effectively strengthened the hydrophobic interaction and hence promoted the formations of long-range ordered mesophases, including a condensed multilamellar phase (L(alpha)(c)) at small to intermediate m (m approximately 6). The lyotropic mesophase transition with respect to the change of m was properly predicted by a formula for calculating the packing parameter of amphiphile mixture. In addition to the lyotropic transition, an unusual thermotropic order-order transition (OOT) between L(alpha)(c) and H(II)(c) phases was revealed for the isoelectric complex with m = 3. This OOT was thermally reversible and was postulated to be driven by the reduction of the effective headgroup area due to the release of trapped water molecules.

  14. The charge effect of cationic surfactants on the elimination of fibre beads in the electrospinning of polystyrene

    NASA Astrophysics Data System (ADS)

    Lin, Tong; Wang, Hongxia; Wang, Huimin; Wang, Xungai

    2004-09-01

    Polystyrene nanofibres were electrospun with the inclusion of cationic surfactants, dodecyltrimethylammonium bromide (DTAB) or tetrabutylammonium chloride (TBAC), in the polymer solution. A small amount of cationic surfactant effectively stopped the formation of beaded fibres during the electrospinning. The cationic surfactants were also found to improve the solution conductivity, but had no effect on the viscosity. Only DTAB had an effect on the surface tension of the polymer solution, the surface tension decreasing slightly with an increase in the concentration of DTAB. The formation of beaded fibres was attributed to an insufficient stretch of the filaments during the whipping of the jet, due to a low charge density. Adding the cationic surfactants improved the net charge density that enhanced the whipping instability. The jet was stretched under stronger charge repulsion and at a higher speed, resulting in an exhaustion of the bead structure. In addition, a polymer/surfactant interaction was found in the polystyrene DTAB solution system, while this interaction was not found in the polystyrene TBAC system. The polymer/surfactant interaction led to the formation of thinner fibres than those formed in the absence of the interaction. The effects of a non-ionic surfactant, Triton X-405, on the electrospun fibres were also studied. The addition of Triton X-405 did not eliminate the fibre beads, but reduced the bead numbers and changed the morphology. Triton X-405 slightly improved the solution conductivity, and had a minor effect on the surface tension, but no effect on the viscosity.

  15. Study of the Formation and Solution Properties of Worm-Like Micelles Formed Using Both N-Hexadecyl-N-Methylpiperidinium Bromide-Based Cationic Surfactant and Anionic Surfactant

    PubMed Central

    Yan, Zhihu; Dai, Caili; Feng, Haishun; Liu, Yifei; Wang, Shilu

    2014-01-01

    The viscoelastic properties of worm-like micelles formed by mixing the cationic surfactant N-hexadecyl-N-methylpiperidinium bromide (C16MDB) with the anionic surfactant sodium laurate (SL) in aqueous solutions were investigated using rheological measurements. The effects of sodium laurate and temperature on the worm-like micelles and the mechanism of the observed shear thinning phenomenon and pseudoplastic behavior were systematically investigated. Additionally, cryogenic transmission electron microscopy images further ascertained existence of entangled worm-like micelles. PMID:25296131

  16. Interactions and hybrid complex formation of anionic algal polysaccharides with a cationic glycine betaine-derived surfactant.

    PubMed

    Covis, Rudy; Vives, Thomas; Gaillard, Cédric; Benoit, Maud; Benvegnu, Thierry

    2015-05-01

    The interaction between anionic algal polysaccharides ((κ)-, (ι)-, (λ)-carrageenans, alginate and ulvan) and a cationic glycine betaine (GB) amide surfactant possessing a C18:1 alkyl chain has been studied using isothermal titration calorimetry (ITC), zeta-potential measurements, dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and surface tension measurements. It was observed that this cationic surfactant derived from renewable raw materials induced cooperative binding with the anionic polymers at critical aggregation concentration (CAC) and the CAC values are significantly lower than the corresponding critical micelle concentration (CMC) for the surfactant. The CMC of cationic GB surfactant was obtained at higher surfactant concentration in polysaccharide solution than in pure water. More interestingly, the presence of original polysaccharide/surfactant hybrid complexes formed above the CMC value was evidenced from (κ)-carrageenan by microscopy (TEM and AFM). Preliminary investigations of the structure of these complexes revealed the existence of surfactant nanoparticles surrounded with polysaccharide matrix, probably resulting from electrostatic attraction. In addition, ITC measurements clearly showed that the interactions of the κ-carrageenan was stronger than for other polysaccharides ((ι)-, (λ)-carrageenans, alginate and ulvan). These results may have important impact on the use of the GB amide surfactant in formulations based on algal polysaccharides for several applications such as in food, cosmetics, and detergency fields.

  17. Interactions between fluorinated cationic guar gum and surfactants in the dilute and semi-dilute solutions.

    PubMed

    Wang, Chen; Li, Xiaorui; Li, Peizhi; Niu, Yuhua

    2014-01-01

    The interactions between the fluorinated cationic guar gum (FCGG) and ionic surfactants including cetyl trimethyl ammonium bromide (CTAB) and sodium lauryl sulfate (SDS) were studied by light scattering, fluorescence spectroscopy, UV-spectrophotometer, (19)F NMR and dynamic rheometer, respectively. The FCGG is prepared with cationic guar gum, isophorone diisocyanate and 2,2,3,4,4,4-hexafluoro-1-butanol. The results show that, with the addition of the surfactants, the stretching degree of the FCGG chains is increased in the FCGG/CTAB solutions, while the dramatical shrinking of FCGG chain, the phase separation and the re-stretched macromolecules appear successively because of the electricity neutralization reaction in the FCGG/SDS system. The mixed hydrophobic domains in all solutions will be reinforced and then dismantled. The solution elasticity shows up the maximum value accordingly. The surfactants can be embedded in the micro-domains and then hinder the fluorinated segmental motions. The interactions between FCGG and SDS are much stronger than those between FCGG and CTAB.

  18. Active Demulsification of Photoresponsive Emulsions Using Cationic-Anionic Surfactant Mixtures.

    PubMed

    Takahashi, Yutaka; Koizumi, Nanami; Kondo, Yukishige

    2016-01-26

    The influence of ultraviolet (UV) light irradiation on the emulsification properties of mixtures of an anionic surfactant, sodium dodecyl sulfate (SDS), and a photoresponsive cationic surfactant, 2-(4-(4-butylphenyl)diazenylphenoxy)ethyltrimethylammonium bromide (C4AzoTAB), containing an azobenzene group has been investigated. When mixtures of n-octane and aqueous SDS/trans-C4AzoTAB solution are homogenized, stable emulsions are obtained in regions of specific surfactant concentrations and molar ratios of the mixed surfactants. The stable emulsions are stable for over a week and found to be of the oil-in-water (O/W) type. UV light irradiation of the stable O/W emulsions leads to the coalescence of smaller oil droplets into larger ones in the emulsions, i.e., demulsification. As a result, the oil and aqueous surfactant solution phases are fully separated by UV light irradiation for 90 min, even shorter than our previous result (6 h; Langmuir 2014 , 30 , 41 - 47 ). The use of a microreactor shortens the time required for the photoinduced demulsification into 3.5 min. When mixtures of octane and aqueous SDS/cis-C4AzoTAB solution are homogenized, no emulsions are obtained. The interfacial tension (IFT) between octane and aqueous SDS/cis-C4AzoTAB solution is higher than that between octane and aqueous SDS/trans-C4AzoTAB solution, indicating that the IFT of SDS/trans-C4AzoTAB mixtures increases with the cis photoisomerization of the trans isomer. These results suggest that cis isomerization of the SDS/trans-C4AzoTAB mixtures due to UV light irradiation causes Ostwald ripening of the octane droplets in the emulsions, thereby reducing the interfacial area between the octane and water phases as the IFT between octane and the aqueous surfactant solution increases. Subsequently, the octane and aqueous solution phases separate.

  19. [Case of upper airway stenosis after accidental ingestion of neutral detergent containing cationic surfactant (HDQ Neutral)].

    PubMed

    Nagae, Masaharu; Naito, Hiromichi; Okahara, Shuji; Hikasa, Yukiko; Okada, Daisuke; Hagioka, Shingo; Morimoto, Naoki

    2011-03-01

    We had a case of upper airway stenosis after accidental ingestion of neutral detergent containing cationic surfactant (HDQ Neutral). An 85-year-old man was transported to our hospital by ambulance after ingesting 50 mL of HDQ Neutral. On arrival, he had an edematous buccopharyngeal membrane with bleeding. Laryngeal edema was observed by laryngoscopy, and severe upper airway stenosis occurred. He also had hypoxemia and was therefore intubated and put on mechanical ventilation. After admission, his respiratory condition was stable. On day 3, upper airway edema had improved and extubation was performed. He was cured without other complications. Surfactants generally have low toxicity but can cause damage to the mucous membrane of the respiratory tract and gastrointestinal tract. Therefore, immediate evaluation and treatment are needed for intoxication with them. They can also cause harm to circulation dynamics or the central nerve system, and careful follow-up is therefore needed.

  20. Time-Resolved SAXS Spectra after Rapidly Mixing Anionic and Cationic Surfactants

    SciTech Connect

    Koga, Mayuko; Sasaki, Shigeo

    2006-05-05

    The temporal evolution of nano-structures in mixing the aqueous solutions of anionic and cationic surfactants was investigated by measuring time-resolved SAXS spectra. It is found that vesicles formed just after mixing annihilate to be followed by the lamella formation. The peak intensity due to the vesicle structure decays exponentially with an elapsing time. The peak intensity assigned to the lamella structure grows with a power law of time. The decay time of vesicle and the exponent of power function of time describing the lamella growth increase with NaCl concentration. These results indicate that the electrostatic interaction affects the stability of nano-structures.

  1. Sorption of phenol and 4-chlorophenol onto pumice treated with cationic surfactant.

    PubMed

    Akbal, Feryal

    2005-02-01

    In this study the sorption of phenol and 4-chlorophenol on pumice modified with the cationic surfactants hexadecyltrimethyl ammonium bromide (HDTMA) and benzyldimethyl tetradecylammonium chloride (BDTDA) was investigated. Experimental studies indicate that HDTMA-pumice and BDTDA-pumice have the capability to remove phenol and 4-chlorophenol from aqueous solution. The influence of initial concentration and adsorbent dosage was studied. The adsorption of phenol and 4-chlorophenol increased with increasing initial concentration and decreased with increasing amount of adsorbent used. The Freundlich adsorption isotherm was found to describe well the equilibrium adsorption data. The parameters of the Freundlich model have been determined using the adsorption data.

  2. Oil droplet interaction with a quartz surface in solutions of cationic surfactants

    SciTech Connect

    Ershov, A.P.; Esipova, N.E.; Zakharova, M.A.; Zorin, Z.M.; Iskandaryan, G.A.; Madzharova, E.A.; Sergeeva, I.P.; Sobolev, V.D.; Svitova, T.F.; Churaev, N.V.

    1994-01-01

    Contact angles of oil droplets on a quartz surface, emulsion-film thicknesses between the surfaces of quartz and oil, and their surface charges were measured over a wide range of the cationic CTAB concentrations in the background electrolyte solution (10{sup {minus}4} M KCl). Oil droplet motion in a CTAB solution and the processes of mutual displacement were studied in thin capillaries. Tetradecane and silicone oil were used as the model systems. The equilibrium contact angles calculated from the disjoining pressure isotherms closely approximated their experimental counterparts. The calculations were performed with due regard for molecular, electrostatic, and hydrophobic attraction forces. The electrostatic and hydrophobic forces were shown to make the greatest contribution to droplet adhesion. As the CTAB concentration increased to 10{sup {minus}3} M, adhesion decreased sharply because of the hydrophilization of the oil and quartz surfaces and their high positive charge. The data obtained point to the possibility of controlling droplet adhesion by cationic surfactants.

  3. Cationic surfactants in the form of nanoparticles and micelles elicit different human neutrophil responses: a toxicological study.

    PubMed

    Hwang, Tsong-Long; Sung, Calvin T; Aljuffali, Ibrahim A; Chang, Yuan-Ting; Fang, Jia-You

    2014-02-01

    Cationic surfactants are an ingredient commonly incorporated into nanoparticles for clinical practicability; however, the toxicity of cationic surfactants in nanoparticles is not fully elucidated. We aimed to evaluate the inflammatory responses of cationic nanobubbles and micelles in human neutrophils. Soyaethyl morpholinium ethosulfate (SME) and hexadecyltrimethyl-ammonium bromide (CTAB) are the two cationic surfactants employed in this study. The zeta potential of CTAB nanobubbles was 80 mV, which was the highest among all formulations. Nanobubbles, without cationic surfactants, showed no cytotoxic effects on neutrophils in terms of inflammatory responses. Cationic nanobubbles caused a concentration-dependent cytotoxicity of degranulation (elastase release) and membrane damage (release of lactate dehydrogenase, LDH). Among all nanoparticles and micelles, CTAB-containing nanosystems showed the greatest inflammatory responses. A CTAB nanobubble diluent (1/150) increased the LDH release 80-fold. Propidium iodide staining and scanning electron microscopy (SEM) verified cell death and morphological change of neutrophils treated by CTAB nanobubbles. SME, in a micelle form, strengthened the inflammatory response more than SME-loaded nanobubbles. Membrane interaction and subsequent Ca(2+) influx were the mechanisms that triggered inflammation. The information obtained from this work is beneficial in designing nanoparticulate formulations for balancing clinical activity and toxicity. PMID:24246197

  4. Resonance Rayleigh scattering method for the determination of cationic surfactants with chromium(VI)-iodide system.

    PubMed

    Liu, Shaopu; Shi, Yan; Liu, Zhongfang; Luo, Hongqun; Kong, Ling

    2006-05-01

    A method for detecting and identifying cationic surfactant in some chemical samples for daily use that include Head & Shoulder Ampoule and Slek Shower Lotion has been developed. In an acid medium, chromium(VI) oxidizes I(-) to produce I(2), I(2) binds excess of I(-) to form I(3)(-), and I(3)(-) can further react with a cationic surfactant (CS) (such as cetyldimethyl benzylammonium chloride (CDBAC), Zephiramine (Zeph), cetylpyridinium bromide (CPB), tetradecyl pyridinium bromide (TPB) and cetyltrimethylammonium bromide (CTAB)) to form ion-association complexes [CS][I(3)]. This results in a significant enhancement of resonance Rayleigh scattering (RRS) and appearance of new RRS spectra. The RRS spectral characteristics of the ion-association complexes, the influencing factors and the optimum conditions of the reactions have been investigated. The intensities of RRS are directly proportional to the concentration of CS. CS in samples are collected using a treated anion exchange column and subsequently complexed by I(3)(-); then the RRS intensities of CS complex are determined at 495 nm. The reactions have high sensitivities, and their detection limits are 7.05 - 9.62 ng/mL for different CS. The effects of foreign substances are investigated and the results show that the method has good selectivity.

  5. Resonance Rayleigh scattering study of interaction of heparin with some cationic surfactants and their analytical application

    NASA Astrophysics Data System (ADS)

    Liu, Shao Pu; Luo, Hong Qun; Xu, Hong; Li, Nian Bing

    2005-03-01

    Binding of heparin with a cationic surfactant such as cetyldimethyl benzylammonium chloride (CDBAC), tetradecyldimethyl benzylammonium chloride (Zeph), cetylpyridinium bromide (CPB), tetradecane pyridinium bromide (TPB) and cetyltrimethylammonium bromide (CTAB) in a near-neutral medium can result in a significant enhancement of resonance Rayleigh scattering (RRS) intensities. The results showed that the reaction conditions and RRS spectral characteristics of these reactions are similar, but their sensitivities are obviously different. Among them, the sensitivity of CDBAC with an aryl and large molecular weight is the highest, while that of CTAB without aryl and with small molecular weight is the lowest. The detection limit for heparin of the former is 11 ng ml -1 while that of the latter is 33 ng ml -1. The method has better selectivity and was applied to the determination of trace amounts of heparin in sodium heparin injection samples with satisfactory results. Furthermore, it is discovered that the RRS intensity is related to the structure and molecular weight of the cationic surfactant.

  6. Resonance Rayleigh scattering method for the determination of cationic surfactants with chromium(VI)-iodide system.

    PubMed

    Liu, Shaopu; Shi, Yan; Liu, Zhongfang; Luo, Hongqun; Kong, Ling

    2006-05-01

    A method for detecting and identifying cationic surfactant in some chemical samples for daily use that include Head & Shoulder Ampoule and Slek Shower Lotion has been developed. In an acid medium, chromium(VI) oxidizes I(-) to produce I(2), I(2) binds excess of I(-) to form I(3)(-), and I(3)(-) can further react with a cationic surfactant (CS) (such as cetyldimethyl benzylammonium chloride (CDBAC), Zephiramine (Zeph), cetylpyridinium bromide (CPB), tetradecyl pyridinium bromide (TPB) and cetyltrimethylammonium bromide (CTAB)) to form ion-association complexes [CS][I(3)]. This results in a significant enhancement of resonance Rayleigh scattering (RRS) and appearance of new RRS spectra. The RRS spectral characteristics of the ion-association complexes, the influencing factors and the optimum conditions of the reactions have been investigated. The intensities of RRS are directly proportional to the concentration of CS. CS in samples are collected using a treated anion exchange column and subsequently complexed by I(3)(-); then the RRS intensities of CS complex are determined at 495 nm. The reactions have high sensitivities, and their detection limits are 7.05 - 9.62 ng/mL for different CS. The effects of foreign substances are investigated and the results show that the method has good selectivity. PMID:16770060

  7. Micellization of mixtures of amphiphilic drugs and cationic surfactants: a detailed study.

    PubMed

    Kabir-ud-Din; Rub, Malik Abdul; Naqvi, Andleeb Z

    2012-04-01

    The micellization behaviors of two amphiphilic drugs ((amitriptyline hydrochloride (AMT) and imipramine hydrochloride (IMP)) in presence of cationic surfactants (conventional as well as gemini) have been investigated conductometrically at four mole fractions and four temperatures. The critical micelle concentration (cmc) values come out to be lower than cmc(id) values (cmc(id) is the cmc value at ideal mixing state) indicating attractive interactions between the two components in mixed micelles. Micellar mole fractions of surfactants (X(1) and X(1)(M)), calculated by Rubingh and Motomura models, are always greater than X(1)(id) (micellar mole fraction at ideal mixing). The rigid structure of drugs decreases their contribution in mixed micelles as compared to that predicted by X(1)(id) values. Although α(1) (mole fraction of surfactant) is higher for DTAB than that of 12-4-12, the contribution of 12-4-12 is almost equal to that of DTAB. The interaction parameter (β) is negative at all temperatures and at all compositions indicating attractive interactions. Activity coefficients (f(1) and f(2)) are always less than unity suggesting nonideality in the systems. Thermodynamic parameters suggest dehydration of hydrophobic part of the drug at or above certain temperature which is different for the two drugs.

  8. Structural behaviour of mixed cationic surfactant micelles: a small-angle neutron scattering study.

    PubMed

    Bergström, L Magnus; Garamus, Vasil M

    2012-09-01

    Self-assembly in mixtures of two single-chain cationic surfactants, with different tail lengths (CTAB and DTAB) as well as of a single-chain (DTAB) and a double-chain (DDAB) cationic surfactant, with identical tail lengths, have been investigated with small-angle neutron scattering (SANS) and rationalised in terms of bending elasticity properties. The growth behaviour of micelles with respect to surfactant composition appears completely different in the two surfactant mixtures. DTAB form small oblate spheroidal micelles in presence of [NaBr]=0.1 M that transform into prolate spheroidal mixed CTAB/DTAB micelles upon adding moderate amounts of CTAB, so as to give a mole fraction y=0.20 in solution. Most unexpectedly, upon further addition of CTAB the mixed CTAB/DTAB micelles grow with an almost equal rate in both length and width directions to form tablets. In contrast to this behaviour, mixed DDAB/DTAB micelles grow virtually exclusively in the length direction, in presence of [NaBr]=0.1 M, to form elongated ellipsoidal (tablet-shaped) and subsequently long wormlike micelles as the fraction of DDAB in the micelles increases. Mixed DDAB/DTAB micelles grow to become as long as 2000Å before an abrupt transition to large bilayer structures occurs. This means that the micelles are much longer at the micelle-to-bilayer transition as compared to the same mixture in absence of added salt. It is found that the point of transition from micelles to bilayers is significantly shifted towards higher fractions of aggregated DTAB as an appreciable amount of salt is added to DDAB/DTAB mixtures, indicating a considerable reduction of the spontaneous curvature with an increasing [NaBr]. By means of deducing the various bending elasticity constants from our experimental results, according to a novel approach by ours, we are able to conclude that the different growth behaviours appear as a consequence of a considerably lower bending rigidity, as well as higher saddle-splay constant

  9. Cooperativity or phase transition? Unfolding transition of DNA cationic surfactant complex

    NASA Astrophysics Data System (ADS)

    Mel'nikov, Sergey M.; Sergeyev, Vladimir G.; Yoshikawa, Kenichi; Takahashi, Hiroshi; Hatta, Ichiro

    1997-11-01

    We recently reported that single duplex DNA, with the size above the order of several tens kilobase pairs, undergoes a large discrete transition from an elongated coil into a collapsed globule with the addition of a cationic surfactant. In the present article, we describe the manner of the unfolding transition of compact long DNA, or globule DNA, complexed with cationic surfactants, cetyltrimethylammonium bromide (CTAB) and distearyldimethylammonium bromide (D18DAB), as is induced by the addition of sodium bromide. The conformational dynamics of individual single duplex T4DNA molecules was directly observed with the use of fluorescence microscopy. We found that on the level of individual DNAs, the salt-induced unfolding transition of the globules is largely discrete, or first-order phase transition for the both complexes with CTAB and D18DAB. On the other hand, for the ensemble average of the DNAs, the transition is discrete with CTAB but is continuous (sigmoidal) with D18DAB. The discreteness for the coil-globule transition in the ensemble of DNAs complexed with CTAB is attributed to the existence of the phase transition in whole over the bulk solution: the sphere-rod transition in surfactant micelles. On the other hand, for D18DAB such phase transition on the micelle structure in the bulk solution seems to be absent. In correspondence to such a large difference on the manner of the transition, x-ray diffraction analysis indicates marked difference on the structure of DNA complexes with CTAB and with D18DAB.

  10. Effects of electrokinetics and cationic surfactant cetyltrimethylammonium bromide [CTAB] on the hydrocarbon removal and retention from contaminated soils.

    PubMed

    Ranjan, R Sri; Qian, Y; Krishnapillai, M

    2006-07-01

    Hydrocarbon contaminated soil and groundwater is considered to be a leading cause for increased health risk and environmental contamination. Therefore, an efficient technique is needed to retard the movement or enhance the removal of the contaminant depending on the remediation objective. The goals of this study were to evaluate the impact of the addition of a cationic surfactant on the movement of hydrocarbons within a contaminated clay soil subjected to electrokinetic treatment. Water-flushing and surfactant-flushing experiments were conducted on one-dimensional soil columns. The model diesel fuel was composed of a mixture of benzene, toluene, ethylbenzene, xylenes [BTEX] and three selected polycyclic hydrocarbons [PAHs]. In the water-flushing experiments, the application of an electrokinetic treatment was found to enhance the removal of PAHs from the clay columns by about 20%. In contrast, the application of an electrokinetic treatment, when coupled with cationic surfactant-flushing, retarded the movement of BTEX and the three selected PAHs in the clay columns. Hydraulic columns with surfactant (CTAB) removed 17% more naphthalene and 11% more 2-methylnaphthalene compared to columns subjected to electrokinetic treatment with CTAB. The flux through the electrokinetic columns during water flushing as well as surfactant flushing was higher than the flux due to hydraulic gradient alone. As the solubility of hydrocarbons increased, they moved farther with electrokinetic treatment without CTAB. However, with CTAB the electrokinetic treatment tends to retard the movement. Use of a cationic surfactant coupled with electrokinetic treatment was found to retard the movement of contaminants.

  11. Modification of the surfaces of Wyoming montmorillonite by the cationic surfactants alkyl trimethyl, dialkyl dimethyl, and trialkyl methyl ammonium bromides.

    PubMed

    Xi, Yunfei; Frost, Ray L; He, Hongping

    2007-01-01

    Surfaces of a Wyoming SWy-2 sodium montmorillonite were modified using microwave radiation through intercalation with the cationic surfactants octadecyl-trimethyl ammonium bromide, dimethyldioctadecylammonium bromide, and methyl-tri-octadecyl ammonium bromide by an ion exchange mechanism. Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG) and infrared (IR) spectroscopy. Different configurations of surfactants within montmorillonite interlayer are proposed based on d(001) basal spacings. A range of surfactant molecular environments within the surface-modified montmorillonite are proposed based upon their thermal decomposition. IR spectroscopy using a smart endurance single bounce diamond attenuated total reflection (ATR) cell has been used to study the changes in the spectra of CH asymmetric and symmetric stretching modes of the surfactants to provide more information of the surfactant molecular configurations.

  12. Interaction of bovine serum albumin with N-acyl amino acid based anionic surfactants: Effect of head-group hydrophobicity.

    PubMed

    Ghosh, Subhajit; Dey, Joykrishna

    2015-11-15

    The function of a protein depends upon its structure and surfactant molecules are known to alter protein structure. For this reason protein-surfactant interaction is important in biological, pharmaceutical, and cosmetic industries. In the present work, interactions of a series of anionic surfactants having the same hydrocarbon chain length, but different amino acid head group, such as l-alanine, l-valine, l-leucine, and l-phenylalanine with the transport protein, bovine serum albumin (BSA), were studied at low surfactant concentrations using fluorescence and circular dichroism (CD) spectroscopy, and isothermal titration calorimetry (ITC). The results of fluorescence measurements suggest that the surfactant molecules bind simultaneously to the drug binding site I and II of the protein subdomain IIA and IIIA, respectively. The fluorescence as well as CD spectra suggest that the conformation of BSA goes to a more structured state upon surfactant binding at low concentrations. The binding constants of the surfactants were determined by the use of fluorescence as well as ITC measurements and were compared with that of the corresponding glycine-derived surfactant. The binding constant values clearly indicate a significant head-group effect on the BSA-surfactant interaction and the interaction is mainly hydrophobic in nature.

  13. Experimenting with Synthesis and Analysis of Cationic Gemini Surfactants in a Second-Semester General Chemistry Laboratory

    ERIC Educational Resources Information Center

    Anzovino, Mary E.; Greenberg, Andrew E.; Moore, John W.

    2015-01-01

    A laboratory experiment is described in which students synthesize a variety of cationic gemini surfactants and analyze their efficacy as fabric softeners. Students perform a simple organic synthesis reaction and two analytical tests (one qualitative and one quantitative), and use the class data to assess the synthesized products. The experiment…

  14. Determination of anionic surface active agents using silica coated magnetite nanoparticles modified with cationic surfactant aggregates.

    PubMed

    Pena-Pereira, Francisco; Duarte, Regina M B O; Trindade, Tito; Duarte, Armando C

    2013-07-19

    The development of a novel methodology for extraction and preconcentration of the most commonly used anionic surface active agents (SAAs), linear alkylbenzene sulfonates (LAS), is presented herein. The present method, based on the use of silica-magnetite nanoparticles modified with cationic surfactant aggregates, was developed for determination of C10-C13 LAS homologues. The proposed methodology allowed quantitative recoveries of C10-C13 LAS homologues by using a reduced amount of magnetic nanoparticles. Limits of detection were in the range 0.8-1.9μgL(-1) for C10-C13 LAS homologues, while the repeatability, expressed as relative standard deviation (RSD), ranged from 2.0 to 3.9% (N=6). Finally, the proposed method was successfully applied to the analysis of a variety of natural water samples.

  15. Bioaccumulation and toxicity of a cationic surfactant (DODMAC) in sediment dwelling freshwater invertebrates.

    PubMed

    Comber, S D W; Rule, K L; Conrad, A U; Höss, S; Webb, S F; Marshall, S

    2008-05-01

    Dimethyldioctadecylammonium chloride (DODMAC, CAS No. 107-64-2) is the principal active component of Di(hydrogenated tallow alkyl) dimethylammonium chloride (DHTDMAC, CAS No. 61789-80-8), a cationic surfactant formerly used principally in laundry fabric softeners. After discharge to water, DODMAC partitions strongly to sediment, therefore the assessment of the effects of DODMAC to benthic organisms is essential in any risk assessment. Chronic toxicity studies were conducted with Lumbriculus variegatus (Oligochaete), Tubifex tubifex (Oligochaete) and Caenorhabditis elegans (Nematode). NOECs were greater than 5738, 1515 and 1351 mg/kg dw, respectively, even for sub-lethal effects. Measurement of the route of uptake of DODMAC by L. variegatus demonstrated the relative importance of uptake via ingestion (86%) compared with direct contact with the sediment and via pore water (14%). The overall tendency of DODMAC to bioaccumulate, however, was low with measured accumulation factors of 0.22 and 0.78 for L. variegatus and T. tubifex, respectively. PMID:17889974

  16. Effects of cationic surfactant exposure to a bivalve mollusc in stream mesocosms

    SciTech Connect

    Belanger, S.E.; Davidson, D.H.; Cherry, D.S. . Environmental Science Dept.); Farris, J.L.; Reed, D. . Univ. Center for Environmental and Hazardous Materials Studies and Biology Dept.)

    1993-10-01

    Effects of the cationic surfactant lauryl trimethyl ammonium chloride (C[sub 12]-TMAC) on growth, reproduction, cellulolytic enzyme activity, and larval colonization of Asiatic clams (Corbicula fluminea) were investigated in experimental stream mesocosms. Clams from three different populations and of two known morphotypes were evaluated for growth in two 8-week experiments in fall 1989 and spring 1990. Growth was impaired at 185 [mu]g/L. It is not known at this time to what extent the effects on pediveligers would be manifested relative to recruitment to later life stages. These findings were compared to a published safety assessment for mono-alkyl quanternaries, of which TMAC is a member. The findings reported here do not substantially alter conclusions from previous studies; however, clams appear to be among the more sensitive taxa studied thus far.

  17. Modification of montmorillonite with cationic surfactant and application in electrochemical determination of 4-chlorophenol.

    PubMed

    Yang, Hongyu; Zheng, Xiaojiang; Huang, Wensheng; Wu, Kangbing

    2008-09-01

    Herein, montmorillonite calcium was exchanged with a cationic surfactant: cetyltrimethylammonium bromide (CTAB). The resulting CTAB-modified montmorillonite calcium (CTAB-MMT) shows higher accumulation efficiency to 4-chlorophenol compared with the unmodified MMT. At the CTAB-MMT-modified carbon paste electrode, the oxidation peak current of 4-chlorophenol remarkably increases. Based on this, a novel, sensitive and convenient electrochemical method was developed for the determination of 4-chlorophenol. The oxidation peak current of 4-chlorophenol is proportional to its concentration over the range from 5.0 x 10(-8) to 1.0 x 10(-5) mol L(-1). The limit of detection is evaluated to be 2.0 x 10(-8) mol L(-1) for 2 min accumulation. Finally this newly proposed method was successfully applied to determine 4-chlorophenol in water samples. PMID:18539012

  18. Surfacted ferrofluid based dispersive solid phase extraction; a novel approach to preconcentration of cationic dye in shrimp and water samples.

    PubMed

    Fasih Ramandi, Negin; Shemirani, Farzaneh

    2015-10-15

    Surfacted ferrofluid (S-FF) is a stable colloid dispersion of magnetic nanoparticles in a carrier liquid which possesses magnetic properties and fluidity simultaneously. Specifically in S-FF coating magnetic nanoparticles with a suitable surfactant provides steric repulsions to prevent particles agglomeration. Selecting the function of surfactant can be engineered according to its application. In the present study, for the first time the application of S-FF in dispersive solid phase extraction of methylene blue (as a cationic dye model) in water and shrimp samples was investigated. For this purpose, in order to use ionic liquid as carrier fluid, the surface of Fe3O4 nanoparticles was coated by an anionic surfactant in a polar medium to form a hydrophilic layer around magnetic nanoparticles. In addition to hydrophobic interactions between the analyte and carbonic chain of surfactant, the retention of cationic dye was mainly governed by attractive electrostatic interactions between polar head of surfactant and dye. Under optimized conditions, the relative standard deviation is 2.9%, the limit of detection is 2.5 μg L(-1), and the preconcentration factor is 135. PMID:25952885

  19. DNA Compaction Induced by a Cationic Polymer or Surfactant Impact Gene Expression and DNA Degradation

    PubMed Central

    Ainalem, Marie-Louise; Bartles, Andrew; Muck, Joscha; Dias, Rita S.; Carnerup, Anna M.; Zink, Daniele; Nylander, Tommy

    2014-01-01

    There is an increasing interest in achieving gene regulation in biotechnological and biomedical applications by using synthetic DNA-binding agents. Most studies have so far focused on synthetic sequence-specific DNA-binding agents. Such approaches are relatively complicated and cost intensive and their level of sophistication is not always required, in particular for biotechnological application. Our study is inspired by in vivo data that suggest that DNA compaction might contribute to gene regulation. This study exploits the potential of using synthetic DNA compacting agents that are not sequence-specific to achieve gene regulation for in vitro systems. The semi-synthetic in vitro system we use include common cationic DNA-compacting agents, poly(amido amine) (PAMAM) dendrimers and the surfactant hexadecyltrimethylammonium bromide (CTAB), which we apply to linearized plasmid DNA encoding for the luciferase reporter gene. We show that complexing the DNA with either of the cationic agents leads to gene expression inhibition in a manner that depends on the extent of compaction. This is demonstrated by using a coupled in vitro transcription-translation system. We show that compaction can also protect DNA against degradation in a dose-dependent manner. Furthermore, our study shows that these effects are reversible and DNA can be released from the complexes. Release of DNA leads to restoration of gene expression and makes the DNA susceptible to degradation by Dnase. A highly charged polyelectrolyte, heparin, is needed to release DNA from dendrimers, while DNA complexed with CTAB dissociates with the non-ionic surfactant C12E5. Our results demonstrate the relation between DNA compaction by non-specific DNA-binding agents and gene expression and gene regulation can be achieved in vitro systems in a reliable dose-dependent and reversible manner. PMID:24671109

  20. Effect of cationic and anionic surfactants on the application of calcium carbonate nanoparticles in paper coating.

    PubMed

    Barhoum, Ahmed; Rahier, Hubert; Abou-Zaied, Ragab Esmail; Rehan, Mohamed; Dufour, Thierry; Hill, Gavin; Dufresne, Alain

    2014-02-26

    Modification of calcium carbonate particles with surfactant significantly improves the properties of the calcium carbonate coating on paper. In this study, unmodified and CTAB (hexadecyltetramethylammonium bromide)- and oleate-modified calcium carbonate nanoparticles were prepared using the wet carbonation technique for paper coating. CTAB (cationic surfactant) and sodium oleate (anionic surfactant) were used to modify the size, morphology, and surface properties of the precipitated nanoparticles. The obtained particles were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, zeta potential measurements, thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM). Coating colors were formulated from the prepared unmodified and modified calcium carbonates and examined by creating a thin coating layer on reference paper. The effect of calcium carbonate particle size and surface modification on paper properties, such as coating thickness, coating weight, surface roughness, air permeability, brightness, whiteness, opacity, and hydrophobicity, were investigated and compared with commercial ground (GCC) calcium carbonate-coated papers. The results show that the obtained calcium carbonate nanoparticles are in the calcite phase. The morphology of the prepared calcium carbonate nanoparticles is rhombohedral, and the average particle diameter is less than 100 nm. Compared to commercial GCC, the use of unmodified and CTAB- and oleate-modified calcium carbonate nanoparticles in paper coating improves the properties of paper. The highest measured paper properties were observed for paper coated with oleate-modifed nanoparticles, where an increase in smoothness (decrease in paper roughness) (+23%), brightness (+1.3%), whiteness (+2.8%), and opacity (+2.3%) and a decrease in air permeability (-26%) was obtained with 25% less coat weight. The water contact angle at a drop age time of 10 min was about 112° for the paper

  1. Synergistic effect of cationic and anionic surfactants for the modification of Ca-montmorillonite

    SciTech Connect

    Zhang, Zepeng; Zhang, Jichu; Liao, Libing; Xia, Zhiguo

    2013-05-15

    Highlights: ► The basal spacing of MMT–CTAB–SDS reaches 5.30 nm. ► MMT–CTAB–SDS shows perfect dispersion property and excellent heat resistance. ► SDS helped to improve the heat resistance and decrease the surface energy of the MMT–CTAB–SDS particles. - Abstract: The synergistic effect of cationic surfactant (CTAB) and anionic surfactant (SDS) for the modification of Ca-montmorillonite (Ca-MMT) has been developed, and the novel cation–anion modified organomontmorillonite (MMT–CTAB–SDS) was prepared. X-ray diffraction (XRD) analysis indicates that the interlayer spacing of montmorillonite was well expanded by the intercalation of CTAB and SDS and the basal spacing increased from 1.54 nm (Ca-MMT) to 5.30 nm (MMT–CTAB–SDS). Thermogravimetric analysis (TG) showed that the MMT–CTAB–SDS displayed excellent heat resistance. Scanning electron microscopy (SEM) analysis proved that the MMT–CTAB–SDS exhibited excellent dispersion property and the plates with few silicate layers can be observed. Contact angle tests indicated that the hydrophilicity of MMT–CTAB–SDS was lower than that of Ca-MMT and higher than that of MMT–CTAB. It was verified that SDS contributed to expanding the interlayer space, further improved the heat resistance of the MMT–CTAB and decreased the surface energy of the MMT–CTAB–SDS particles.

  2. Interaction of a biosurfactant, Surfactin with a cationic Gemini surfactant in aqueous solution.

    PubMed

    Jin, Lei; Garamus, Vasil M; Liu, Fang; Xiao, Jingwen; Eckerlebe, Helmut; Willumeit-Römer, Regine; Mu, Bozhong; Zou, Aihua

    2016-11-01

    The interaction between biosurfactant Surfactin and cationic Gemini surfactant ethanediyl-1,3-bis(dodecyldimethylammonium bromide) (abbreviated as 12-3-12) was investigated using turbidity, surface tension, dynamic light scattering (DLS) and small angle neutron scattering (SANS). Analysis of critical micelle concentration (CMC) values in Surfactin/12-3-12 mixture indicates that there is synergism in formation of mixed Surfactin/12-3-12 micelles. Although Surfactin and 12-3-12 are oppositely charged in phosphate buffer solution (PBS, pH7.4), there are no precipitates observed at the concentrations below the CMC of Surfactin/12-3-12 system. However, at the concentration above CMC value, the Surfactin/12-3-12 mixture is severely turbid with high 12-3-12 content. DLS and SANS measurements follow the size and shape changes of mixed Surfactin/12-3-12 aggregates from small spherical micelles via elongated aggregates to large bulk complexes with increasing fraction of Gemini surfactant. PMID:27475707

  3. Determination of the Critical Micelle Concentration of Cationic Surfactants: An Undergraduate Experiment

    NASA Astrophysics Data System (ADS)

    Huang, Xirong; Yang, Jinghe; Zhang, Wenjuan; Zhang, Zhenyu; An, Zesheng

    1999-01-01

    A novel method based on the catalytic effect of micelles exerted by cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB), respectively, on the indicator reaction between H2O2 and bromopyrogallol red (BPR), a triphenylmethane dye, was developed for undergraduates to determine the critical micelle concentration (cmc) of CTAB and CPB. The indicator reaction was monitored by a fixed-time kinetic-spectrophotometric technique. Under the experimental conditions the cmc values of CTAB and CPB were (4.8 ± 0.3) x 10-4 mol/L and (4.5 ± 0.3) x 10-4mol/L, which were close to the literature values of 9.2 x 10-4 mol/L and 9.0 x 10-4 mol/L, respectively. Detailed discussion on the selection of experimental conditions was made to minimize the effect of electrolytes on the cmc's of surfactants and to maintain the high accuracy of the experimental data. As an undergraduate physicochemical laboratory experiment the present method had several attractive features. The procedure is simple and easy to perform, does not require special equipment, and does not need expensive or toxic reagents. In addition, it is a versatile method that can be applied to a wide variety of both anionic and cationic surfactants.

  4. Faster photodegradation rate and higher dioxin yield of triclosan induced by cationic surfactant CTAB.

    PubMed

    Qiao, Xianliang; Zheng, Xiaodong; Xie, Qing; Yang, Xianhai; Xiao, Jie; Xue, Weifeng; Chen, Jingwen

    2014-06-30

    Triclosan has received extensive attention as it has been frequently detected in the aquatic environment. Photolysis was found to be a major pathway governing the fate of triclosan in the aquatic environment. However, the effects of surfactants that usually coexist with triclosan, on the photodegradation of triclosan, are largely unknown. In this study, the effects of selected surfactants on the photodegradation of triclosan were investigated experimentally. The results show that anionic sodium dodecyl benzene sulfonate, sodium dodecyl sulfate and neutral polyoxyethylene (20) sorbitan monooleate inhibit the photolysis of triclosan, whereas cationic cetyltrimethylammonium bromide (CTAB) significantly accelerates the photodegradation rate of triclosan. The interactions between the hydrophilic group of CTAB and anionic triclosan lead to the apparent decrease of pKa of triclosan from 8.4 to 6.1, which increase the fraction of anionic triclosan from 4% to 89% in neutral solution. A red shift in the UV-VIS absorption spectrum is exhibited, thus leading to the increased photodegradation rate of triclosan. The accelerations caused by CTAB were observed under xenon lamp and Hg lamp irradiances, as well as under natural sunlight. Effect of CTAB demonstrated pH dependence with significantly enhancement under pH 5∼9 and inhibition at pH=3. The presence of CTAB also increased the yield of 2,8-dichlorodibenzo-p-dioxin from the photolysis of triclosan about 7 times at pH=7.

  5. Adsorption of Anionic, Cationic and Nonionic Surfactants on Carbonate Rock in Presence of ZrO 2 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Esmaeilzadeh, Pouriya; Bahramian, Alireza; Fakhroueian, Zahra

    The adsorption of surfactants at the solid-water interface is important for the control of wetting, lubrication, detergency and in mineral flotation.We have studied the adsorptions of different types of surfactants, cationic (Dodecyl trimethylammonium bromide, DTAB), anionic (sodium dodecyl sulfate, SDS) and non-anionic (lauryl alcohol-7 mole ethoxylate, LA7) on carbonate rock in presence of zirconium oxide spherical nanoparticles (17-19 nm). ZrO2 nanoparticles with tetrahedral structure have significant effect on adsorption of surfactants on the carbonate rock. We have used the measured conductivities to determine the rate of adsorption of surfactants at rock-water interfaces. The conductivity of DTAB in aqueous solutions containing calcite powder decreases more than the other surfactants in contact with ZrO2 nanoparticles. We have also investigated the adsorption of surfactants at the air-water interface. The presence of nanoparticles, as demonstrated by our experiments, enhances the surface activity and surface adsorption of the surfactants through electrostatic forces or formation of nanostructures. Dynamic light structuring data shows similar aggregation number of nanoparticles in presence of nanoparticles.

  6. Self-assembly thermodynamics of pH-responsive amino-acid-based polymers with a nonionic surfactant.

    PubMed

    Bogomolova, Anna; Keller, Sandro; Klingler, Johannes; Sedlak, Marian; Rak, Dmytro; Sturcova, Adriana; Hruby, Martin; Stepanek, Petr; Filippov, Sergey K

    2014-09-30

    The behavior of pH-responsive polymers poly(N-methacryloyl-l-valine) (P1), poly(N-methacryloyl-l-phenylalanine) (P2), and poly(N-methacryloylglycyne-l-leucine) (P3) has been studied in the presence of the nonionic surfactant Brij98. The pure polymers phase-separate in an acidic medium with critical pHtr values of 3.7, 5.5, and 3.4, respectively. The addition of the surfactant prevents phase separation and promotes reorganization of polymer molecules. The nature of the interaction between polymer and surfactant depends on the amino acid structure in the side chain of the polymer. This effect was investigated by dynamic light scattering, isothermal titration calorimetry, electrophoretic measurements, small-angle neutron scattering, and infrared spectroscopy. Thermodynamic analysis revealed an endothermic association reaction in P1/Brij98 mixture, whereas a strong exothermic effect was observed for P2/Brij98 and P3/Brij98. Application of regular solution theory for the analysis of experimental enthalpograms indicated dominant hydrophobic interactions between P1 and Brij98 and specific interactions for the P2/Brij98 system. Electrophoretic and dynamic light scattering measurements support the applicability of the theory to these cases. The specific interactions can be ascribed to hydrogen bonds formed between the carboxylic groups of the polymer and the oligo(ethylene oxide) head groups of the surfactant. Thus, differences in polymer-surfactant interactions between P1 and P2 polymers result in different structures of polymer-surfactant complexes. Specifically, small-angle neutron scattering revealed pearl-necklace complexes and "core-shell" structures for P1/Brij98 and P2/Brij98 systems, respectively. These results may help in the design of new pH-responsive site-specific micellar drug delivery systems or pH-responsive membrane-disrupting agents.

  7. Oil-in-water microemulsions based on cationic surfactants with a hydroxyalkyl fragment in the head group

    NASA Astrophysics Data System (ADS)

    Mirgorodskaya, Alla B.; Yackevich, Ekaterina I.; Zakharova, Lucia Ya.; Konovalov, Alexander I.

    2013-04-01

    The stable oil-in-water microemulsions with a high water content were formed on the basis of cationic surfactants, including those that contain a hydroxyalkyl fragment in the head group. These systems can bind the water- and oil-soluble reagents into a single aggregate formed by self-assembling components. The size, surface and electrokinetic potentials of aggregates in the surfactant/n-hexane/n-butanol/water microemulsions were determined. Besides, their catalytic effect on the cleavage of carboxylic acid esters was evaluated. The behavior of the system was shown to be determined not only by hydrophobic and electrostatic interactions but also by specific interactions, i.e., hydrogen bonds.

  8. Assessment of the potential irritation and photoirritation of novel amino acid-based surfactants by in vitro methods as alternative to the animal tests.

    PubMed

    Benavides, Tomas; Martínez, Verónica; Mitjans, Montserrat; Infante, María Rosa; Moran, Carmen; Clapés, Pere; Clothier, Richard; Vinardell, María Pilar

    2004-09-01

    The ultraviolet-A radiation damage effects on skin and eyes will be increased by phototoxic compounds which could be present in pharmaceutical or cosmetic formulations. Great efforts have been made in the last years to find surfactants to replace those with phototoxic potential in commercial use. Series of different in vitro models for phototoxicity, included to validated neutral red uptake (NRU) 3T3 phototoxicity assay are useful screening tools. The phototoxic effects of a novel family of glycerol amino acid-based surfactant compounds were examined via these assays. Human red blood cells and two immortalised cell lines, murine fibroblast cell line 3T3, and one human keratinocyte cell line, HaCaT, were the in vitro models employed to predict potential photoirritation. The phototoxic end-points assessed were hemolysis (human red blood cell test) and resazurin transformation to resorufin and NRU in cell culture methods. The results suggest that no phototoxic effects by any new amino acid derived-surfactants, could be identified.

  9. Enhanced aqueous solubility of polycyclic aromatic hydrocarbons by green diester-linked cationic gemini surfactants and their binary solutions

    NASA Astrophysics Data System (ADS)

    Panda, Manorama; Fatma, Nazish; Kabir-ud-Din

    2016-07-01

    Three homologues of a novel biodegradable diester-linked cationic gemini surfactant series, CmH2m+1 (CH3)2N+(CH2COOCH2)2N+(CH3)2CmH2m+1.2Cl- (m-E2-m; m = 12, 14, 16), were used for investigation of the solubilization of polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, anthracene and pyrene in single as well as binary surfactant solutions. Physicochemical parameters of the pure/mixed systems were derived by conductivity and surface tension measurements. Dissolution capacity of the equimolar binary surfactant solutions towards the PAHs was studied from the molar solubilization ratio (MSR), micelle-water partition coefficient (Km) and free energy of solubilization (ΔGs0) of the solubilizates. Influence of hydrophobic chain length of the dimeric surfactants on solubilization was characterized. Aqueous solubility of the PAHs was enhanced linearly with concentration of the surfactant in all the pure and mixed gemini-gemini surfactant systems.

  10. pH-Sensitive self-propelled motion of oil droplets in the presence of cationic surfactants containing hydrolyzable ester linkages.

    PubMed

    Banno, Taisuke; Kuroha, Rie; Toyota, Taro

    2012-01-17

    Self-propelled oil droplets in a nonequilibrium system have drawn much attention as both a primitive type of inanimate chemical machinery and a dynamic model of the origin of life. Here, to create the pH-sensitive self-propelled motion of oil droplets, we synthesized cationic surfactants containing hydrolyzable ester linkages. We found that n-heptyloxybenzaldehyde oil droplets were self-propelled in the presence of ester-containing cationic surfactant. In basic solution prepared with sodium hydroxide, oil droplets moved as molecular aggregates formed on their surface. Moreover, the self-propelled motion in the presence of the hydrolyzable cationic surfactant lasted longer than that in the presence of nonhydrolyzable cationic surfactant. This is probably due to the production of a fatty acid by the hydrolysis of the ester-containing cationic surfactant and the subsequent neutralization of the fatty acid with sodium hydroxide. A complex surfactant was formed in the aqueous solution because of the cation and anion combination. Because such complex formation can induce both a decrease in the interfacial tension of the oil droplet and self-assembly with n-heptyloxybenzaldehyde and lauric acid in the aqueous dispersion, the prolonged movement of the oil droplet may be explained by the increase in heterogeneity of the interfacial tension of the oil droplet triggered by the hydrolysis of the ester-containing surfactant.

  11. Niosomes from glucuronic acid-based surfactant as new carriers for cancer therapy: preparation, characterization and biological properties.

    PubMed

    Tavano, Lorena; Aiello, Rossana; Ioele, Giuseppina; Picci, Nevio; Muzzalupo, Rita

    2014-06-01

    Niosomes are vesicular systems composed of surfactant molecules, claimed to be used as drug delivery carriers thanks to their physico-chemical and biological properties. The aim of this work was to design niosomes obtained with a surfactant synthesized from glucuronic acid. Doxorubicin and 5FU were used as model drugs. Niosomes were prepared with different ratios between surfactant and cholesterol, and characterized in terms of size, morphology, drugs entrapment efficiency and in vitro releases, to identify the optimal formulation to be used in pharmaceutical fields. In addition, the hemolytic activity of all formulations have been also evaluated. Results showed that dodecylglucuronamide surfactant was able to produce vesicular systems with or without the presence of cholesterol. Niosomes resulted regular in size and shape and they have been found to encapsulate and release in a controlled manner both doxorubicin and 5-fluorouracil. Hemolytic tests showed that the capability of disrupting erythrocyte only depend on the size of colloidal aggregates. Finally, our formulations could be potentially used as antitumoral delivery systems in anticancer therapy. PMID:24709252

  12. Amino acid-bile acid based molecules: extremely narrow surfactant nanotubes formed by a phenylalanine-substituted cholic acid.

    PubMed

    Travaglini, Leana; D'Annibale, Andrea; Schillén, Karin; Olsson, Ulf; Sennato, Simona; Pavel, Nicolae V; Galantini, Luciano

    2012-12-21

    An amino acid-substituted bile acid forms tubular aggregates with inner and outer diameters of about 3 and 6 nm. The diameters are unusually small for surfactant self-assembled tubes. The results enhance the spectrum of applications of supramolecular tubules and open up possibilities for investigating a novel class of biological amphiphiles.

  13. Alkyl-imidazolium glycosides: non-ionic-cationic hybrid surfactants from renewable resources.

    PubMed

    Salman, Abbas Abdulameer; Tabandeh, Mojtaba; Heidelberg, Thorsten; Hussen, Rusnah Syahila Duali; Ali, Hapipah Mohd

    2015-08-14

    A series of surfactants combining carbohydrate and imidazolium head groups were prepared and investigated on their assembly behavior. The presence of the imidazolium group dominated the interactions of the surfactants, leading to high CMCs and large molecular surface areas, reflected in curved rather than lamellar surfactant assemblies. The carbohydrate, on the other hand, stabilized molecular assemblies slightly and reduced the surface tension of surfactant solutions considerably. A comparative emulsion study discourages the use of pure alkyl imidazolium glycosides owing to reduced assembly stabilities compared with APGs. However, the surfactants are believed to have potential as component in carbohydrate based surfactant mixtures.

  14. An electronic spectroscopic study of micellisation of surfactants and solvation of homomicelles formed by cationic or anionic surfactants using a solvatochromic electron donor acceptor dye

    NASA Astrophysics Data System (ADS)

    Kedia, Niraja; Sarkar, Amrita; Purkayastha, Pradipta; Bagchi, Sanjib

    2014-10-01

    Solvatochromic absorption and fluorescence bands of a donor-acceptor dye have been utilised for following the micellisation and for probing the polarity of the aqueous homomicellar phase provided separately by cationic (cetyltrimethylammonimum bromide, CTAB and dodecyltrimethylammonimum bromide, DTAB) and anionic (sodium dodecyl sulphate, SDS) surfactant. Results indicate that for a low concentration of surfactant (below cmc) the dye forms a dimer in aqueous solution. In a micellar media, however, the dye exists as monomers. A strong dye-micelle interaction, as indicated by the shift of the solvatochromic intramolecular charge transfer band of the dye, has also been indicated. The absorption and fluorescence parameters of the dye have been utilised for studying the onset of aggregation of the surfactants. An iterative procedure has been developed for the estimation of cmc and the distribution coefficient (KD) of the dye between the aqueous and the micellar phase. All the parameters provide convergent values of cmc. A high value of KD indicates that the dye exists predominantly in the micellar phase. The solvatochromic parameters characterising the dipolarity-polarisability (π*) and H-bond donation ability (α) of modes of solvation interaction in different micellar media have been estimated. The dye is found to distribute itself between two regions in a catanionic vesicle formed by surfactants SDS and DTAB, one being relatively polar than other. The distribution coefficients have been found out using the fluorescence data.

  15. An electronic spectroscopic study of micellisation of surfactants and solvation of homomicelles formed by cationic or anionic surfactants using a solvatochromic electron donor acceptor dye.

    PubMed

    Kedia, Niraja; Sarkar, Amrita; Purkayastha, Pradipta; Bagchi, Sanjib

    2014-10-15

    Solvatochromic absorption and fluorescence bands of a donor-acceptor dye have been utilised for following the micellisation and for probing the polarity of the aqueous homomicellar phase provided separately by cationic (cetyltrimethylammonimum bromide, CTAB and dodecyltrimethylammonimum bromide, DTAB) and anionic (sodium dodecyl sulphate, SDS) surfactant. Results indicate that for a low concentration of surfactant (below cmc) the dye forms a dimer in aqueous solution. In a micellar media, however, the dye exists as monomers. A strong dye-micelle interaction, as indicated by the shift of the solvatochromic intramolecular charge transfer band of the dye, has also been indicated. The absorption and fluorescence parameters of the dye have been utilised for studying the onset of aggregation of the surfactants. An iterative procedure has been developed for the estimation of cmc and the distribution coefficient (KD) of the dye between the aqueous and the micellar phase. All the parameters provide convergent values of cmc. A high value of KD indicates that the dye exists predominantly in the micellar phase. The solvatochromic parameters characterising the dipolarity-polarisability (π(*)) and H-bond donation ability (α) of modes of solvation interaction in different micellar media have been estimated. The dye is found to distribute itself between two regions in a catanionic vesicle formed by surfactants SDS and DTAB, one being relatively polar than other. The distribution coefficients have been found out using the fluorescence data.

  16. Ferrate(VI): green chemistry oxidant for degradation of cationic surfactant.

    PubMed

    Eng, Yong Yong; Sharma, Virender K; Ray, Ajay K

    2006-06-01

    Iron in its familiar form exists in the +2 and +3 oxidation states, however, higher oxidation state of iron +6, ferrate(VI) (Fe(VI)O(4)(2-)) can be obtained. The high oxidation power of ferrate(VI) can be utilized in developing cleaner ("greener") technology for remediation processes. This paper demonstrates the unique property of ferrate(VI) to degrade almost completely the cationic surfactant, cetylpyridinium chloride (C(5)H(5)N(+)(CH(2))(15)CH(3).H(2)O Cl(-), CPC). The Rate law for the oxidation of CPC by ferrate(VI) at pH 9.2 was found to be: -d[Fe(VI)]/dt = k[Fe(VI)][CPC](2). Ferrate(VI) oxidizes CPC within minutes and molar consumption of ferrate(VI) was nearly equal to the oxidized CPC. The decrease in total organic carbon (TOC) from CPC was more than 95%; suggesting mineralization of CPC to carbon dioxide. Ammonium ion was the other product of the oxidation. This is the first report in which Fe(VI)O(4)(2-) ion opens the pyridine ring and mineralizes the aliphatic chain of the organic molecule giving inorganic ions. PMID:16303166

  17. Preparation and property of UV-curable polyurethane acrylate film filled with cationic surfactant treated graphene

    NASA Astrophysics Data System (ADS)

    Xu, Jinghong; Cai, Xia; Shen, Fenglei

    2016-08-01

    The preparation of nanocomposite films composed of UV-curable polyurethane acrylate (PUA) and modified graphene were demonstrated in this paper. Cetyl trimethyl ammonium bromide modified graphene (CTAB-G) was prepared via intercalation of cationic surfactant and subsequently incorporated into PUA by UV curing technology. Fourier transform infrared spectra, wide-angle X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the structure and morphology of CTAB-G, as well as CTAB-G/PUA nanocomposite films. The results revealed that the CTAB-G sheets were layer-by-layer structure and dispersed uniformly in PUA matrix. Thermal gravimetric analysis showed that the thermal stabilities of UV-curable PUA nanocomposite films in this work were much higher than that of PUA nanocomposites previously reported. Dynamic mechanical analysis indicated that the dynamic mechanical properties of nanocomposite films were greatly enhanced in the presence of modified graphene sheets. In addition, the CTAB-G/PUA nanocomposite films exhibited improved dielectric properties and electrical conductivities compared with the pure PUA.

  18. Separation of linear synthetic polymers in non-aqueous capillary zone electrophoresis using cationic surfactant.

    PubMed

    Yamamura, Tomoyuki; Kitagawa, Shinya; Ohtani, Hajime

    2015-05-01

    A method for separating water-insoluble and neutral synthetic polymers using non-aqueous capillary zone electrophoresis (NACZE) was developed. The non-aqueous solvent system comprising a mixture of tetrahydrofuran, acetonitrile, and ethanol containing cetyltrimethylammonium chloride was used for solubilizing and conferring positive charges to the polymers. A mixture of polystyrene (PS, Mn=6500) and polybutadiene (PBD, Mn=5900) was successfully separated by the NACZE method using cationic surfactants. Evaluation of the effect of the molecular weight of the polymers on the electrophoretic behavior demonstrated that PSs with different molecular weights (Mn=6500, 10,200, 19,600, 200,000) were co-eluted as a single peak. That is, the apparent electrophoretic mobility of the PSs was independent of the molecular weight. In contrast, evaluation of PBD and polycarbonate (PC) demonstrated that the solubility of polymers in the medium affected the apparent electrophoretic mobility of the polymers, where low solubility resulted in reduced apparent electrophoretic mobility. Using the proposed method, poly(styrene-co-methylmethacrylate)s with different compositions were successfully separated. PMID:25828544

  19. The Effects of Cationic Surfactants on Marine Biofilm Growth on Hydrogels

    NASA Astrophysics Data System (ADS)

    Smith, M. J.; Adam, G.; Duncan, H. J.; Cowling, M. J.

    2002-09-01

    A method for the quantification of biofilm formation on hydrogel protective coatings for optical sensors and cameras has been developed using fluorescein diacetate (FDA) hydrolysis. In conjunction with these measurements the release of the fouling resistant cationic surfactants benzalkonium chloride, tallowbenzyldimethylammonium chloride and dicocodimethylammonium chloride was measured, using high performance liquid chromatography (HPLC), to enable correlation to be made between release and biofilm resistance and thus determine the active lifetime of such coatings. Results indicate that the twin-chained material, dicocodimethylammonium chloride, produced superior biofouling resistance as, at the 12 week time point, little fouling was detected on this coating. The hydrogel containing the long-chained tallowbenzyldimethylammonium chloride (mainly C16 and C18 chains) was the next best fouling resistant material, withstanding biofilm formation for 9 weeks. This correlates with the fact that each of these materials had an extremely slow to zero release rate, due to their irreversible binding to the hydrogel over the experimental timescale. In comparison the shorter chained benzalkonium chloride (mainly C12 and C14), showed signs of biofilm formation at the 3 week time point.

  20. Thermo-responsive properties driven by hydrogen bonding in aqueous cationic gemini surfactant systems.

    PubMed

    Wei, Xi-Lian; Han, Chuan-Hong; Geng, Pei-Pei; Chen, Xiao-Xiao; Guo, Yan; Liu, Jie; Sun, De-Zhi; Zhang, Jun-Hong; Yu, Meng-Jiao

    2016-02-01

    A series of unexpected thermo-responsive phenomena were discovered in an aqueous solution of the cationic gemini surfactant, 2-hydroxypropyl-1,3-bis(alkyldimethylammonium chloride) (n-3(OH)-n(2Cl), n = 14, 16), in the presence of an inorganic salt. The viscosity change trend for the 14-3(OH)-14(2Cl) system was investigated in the 20-40 °C temperature range. As the temperature increased, the viscosity of the solution first decreased to a minimum point corresponding to 27 °C, and then increased until a maximum was reached, after which the viscosity decreased again. In the 16-3(OH)-16(2Cl) system, the gelling temperature (T(gel)) and viscosity changes upon heating were similar to those in the 14-3(OH)-14(2Cl) system above 27 °C. The reversible conversion of elastic hydrogel to wormlike micelles in the aqueous solution of the 16-3(OH)-16(2Cl) system in the presence of an inorganic salt was observed at relatively low temperatures. Various techniques were used to study and verify the phase-transition processes in these systems, including rheological measurements, cryogenic transmission electron microscopy (cryo-TEM), electric conductivity, and differential scanning calorimetry. The abovementioned phenomena were explained by the formation and destruction of intermolecular hydrogen bonds, and the transition mechanisms of the aggregates were analyzed accordingly.

  1. Effect of cationic surfactants on characteristics and colorimetric behavior of polydiacetylene/silica nanocomposite as time-temperature indicator

    NASA Astrophysics Data System (ADS)

    Nopwinyuwong, Atchareeya; Kitaoka, Takuya; Boonsupthip, Waraporn; Pechyen, Chiravoot; Suppakul, Panuwat

    2014-09-01

    Polydiacetylene (PDA)/silica nanocomposites were synthesized by self-assembly method using polymerizable amphiphilic diacetylene monomers, 10,12-pentacosadiynoic acid (PCDA). Addition of cationic surfactants (PDADMAC and CTAB) to PDA/SiO2 nanocomposites induced higher intermolecular force which affected their size, shape and color transition. Pure PDA, PDA/SiO2, PDA/SiO2/PDADMAC and PDA/SiO2/CTAB were investigated by particle size analysis, TEM, SEM, UV-vis spectroscopy and FT-IR. It was found that the PDA/SiO2 nanocomposites exhibited slightly larger particle sizes than those of other samples. The PDA/SiO2 nanocomposites with a core-shell structure were almost regarded as spherical-shaped particles. Cationic surfactants, especially CTAB, presumably affected the particle size and shape of PDA/SiO2 nanocomposites due to the disruption of hydrogen bonding between PDA head group and ammonium group. The colorimetric response of both PDA/SiO2/surfactant and surfactant-free PDA/SiO2 aqueous solutions directly changed in relation to time and temperature; thus they were expected to be applied as a new polymer-based time-temperature indicator (TTI).

  2. Cationic surfactant-assisted hydrothermal synthesis of few-layer molybdenum disulfide/graphene composites: Microstructure and electrochemical lithium storage

    NASA Astrophysics Data System (ADS)

    Ma, Lin; Huang, Guochuang; Chen, Weixiang; Wang, Zhen; Ye, Jianbo; Li, Haiyang; Chen, Dongyun; Lee, Jim Yang

    2014-10-01

    Few-layer molybdenum disulfide/graphene (FL-MoS2/GNS) composites are fabricated by a facile hydrothermal route and a post-annealing with the assistance of various cationic surfactants (dodecyltrimethylammonium bromide, DTAB; octyltrimethylammonium bromide, OTAB; and tetrabutylammonium bromide, TBAB), which have different alkyl-chain lengths and stereo configurations. The effects of these cationic surfactants on the microstructures and electrochemical performances of the FL-MoS2/GNS for lithium storage are investigated. It is demonstrated the cationic surfactants show some ability to control the microstructure (layer number) of FL-MoS2 in composites. The electrochemical performances of FL-MoS2/GNS composites for lithium storage are greatly improved compared to the bare MoS2. Especially, FL-MoS2/GNS with ∼6 MoS2 layers prepared with the assistance of OTAB exhibits very high reversible capacity of ∼1200 mAh g-1 with excellent cycle stability and enhanced rate capability. Electrochemical impedance spectrum also confirms that the FL-MoS2/GNS composite electrodes exhibit much lower electron-transfer resistance than the MoS2. The remarkable electrochemical performances of FL-MoS2/GNS composites can be attributed to the synergistic interaction between FL-MoS2 and graphene and their quasi-3D architectures, which promote lithium diffusion, electron transfer and electrolyte access.

  3. Oxidation of phenyl propyne catalyzed by copper(II) complexes of a benzimidazolyl schiff base ligand: Effect of acid/base, oxidant, surfactant and morphology

    NASA Astrophysics Data System (ADS)

    Kumar, Ravinder; Mathur, Pavan

    2015-02-01

    Copper(II) complexes with a new N-Substituted benzimidazolyl schiff base ligand are used as catalyst for the oxidation of 1-phenyl propyne. The oxidation is carried out under mild conditions using stoichiometric amounts of oxidant and catalytic amounts of Cu(II) complex as catalyst. Effect of acid/base, oxidant, morphology and surfactant has been studied. Two major products of phenyl propyne oxidation are the α-diketonic product and a terminal aldehyde. Diketone is the major product under acidic conditions while aldehyde formation is highest under basic conditions. The maximum conversion is found with the NO3- bound complex. GC-MS is used to find the percentage yields of products. SEM and PXRD of the reused complexes as catalyst suggest that morphology affects the catalytic efficiency.

  4. Oxidation of phenyl propyne catalyzed by copper(II) complexes of a benzimidazolyl schiff base ligand: effect of acid/base, oxidant, surfactant and morphology.

    PubMed

    Kumar, Ravinder; Mathur, Pavan

    2015-02-01

    Copper(II) complexes with a new N-Substituted benzimidazolyl schiff base ligand are used as catalyst for the oxidation of 1-phenyl propyne. The oxidation is carried out under mild conditions using stoichiometric amounts of oxidant and catalytic amounts of Cu(II) complex as catalyst. Effect of acid/base, oxidant, morphology and surfactant has been studied. Two major products of phenyl propyne oxidation are the α-diketonic product and a terminal aldehyde. Diketone is the major product under acidic conditions while aldehyde formation is highest under basic conditions. The maximum conversion is found with the NO3(-) bound complex. GC-MS is used to find the percentage yields of products. SEM and PXRD of the reused complexes as catalyst suggest that morphology affects the catalytic efficiency. PMID:25448979

  5. Seasonal evolution of anionic, cationic and non-ionic surfactant concentrations in coastal aerosols from Askö, Sweden

    NASA Astrophysics Data System (ADS)

    Gérard, Violaine; Nozière, Barbara; Baduel, Christine

    2015-04-01

    Surfactants present in atmospheric aerosols are expected to enhance the activation into cloud droplets by acting on one of the two key parameters of the Köhler equation: the surface tension, σ. But because the magnitude of this effect and its regional and temporal variability are still highly uncertain [1,2], various approaches have been developed to evidence it directly in the atmosphere. This work presents the analysis of surfactants present in PM2.5 aerosol fractions collected at the coastal site of Askö, Sweden (58° 49.5' N, 17° 39' E) from July to October 2010. The total surfactant fraction was extracted from the samples using an improved double extraction technique. Surface tension measurements performed with the pendant drop technique [3] indicated the presence of very strong surfactants (σ ~ 30 - 35 mN/m) in these aerosols. In addition, these extractions were combined with colorimetric methods to determine the anionic, cationic and non-ionic surfactant concentrations [4,5], and provided for the first time interference-free surfactant concentrations in atmospheric aerosols. At this site, the total surfactant concentration in the PM2.5 samples varied between 7 to 150 mM and was dominated by anionic and non-ionic ones. The absolute surface tension curves obtained for total surfactant fraction displayed Critical Micelle Concentrations (CMC) in the range 50 - 400 uM, strongly suggesting a biological origin for the surfactants. The seasonal evolution of these concentrations and their relationships with environmental or meteorological parameters at the site will be discussed. [1] Ekström, S., Nozière, B. et al., Biogeosciences, 2010, 7, 387 [2] Baduel, C., Nozière, B., Jaffrezo, J.-L., Atmos. Environ., 2012, 47, 413 [3] Nozière, B., Baduel, C., Jaffrezo, J.-L., Nat. Commun., 2014, 5, 1 [4] Latif, M. T.; Brimblecombe, P. Environ. Sci. Technol., 2004, 38, 6501 [5] Pacheco e Silva et al., Method to measure surfactant in fluid, 2013, US 2013/0337568 A1

  6. Long-term effects of dietary anion-cation balance on acid-base status and bone morphology in reproducing ewes.

    PubMed

    Espino, L; Guerrero, F; Suarez, M L; Santamarina, G; Goicoa, A; Fidalgo, L E

    2003-12-01

    The beneficial effects of anionic salts on calcium metabolism have been shown by supplementing rations with such salts during the last 3 weeks of pre-partum. However, there are few reports on the effects of anionic salts supplementation for periods of 4 weeks or longer on acid-base status, mineral metabolism and bone morphology. This study was conducted to evaluate the effects of the long-term dietary supplementation of anionic salts on the acid-base status, plasma minerals concentrations and bone morphology in sheep. Twenty-seven twin-bearing sheep were assigned to two experimental groups and a control group, depending on dietary cation-anion difference (DCAD) (+272.6, -88.9 and + 164.5 mEq/kg DM, respectively). Sheep assigned to each dietary treatment received their respective rations beginning 6 weeks prepartum and continuing until 12 days post-partum. Diets containing anionic salts induced a mild metabolic hyperchloraemic acidosis from 1 week pre-partum to 2 days post-partum that was completely compensated by non-respiratory mechanisms. These changes on acid-base status were accompanied by an increase of plasma ionized calcium levels. Plasma total calcium, phosphorus and magnesium concentrations were not affected by dietary treatment. Parathyroid hormone concentrations were related to the concentration of ionized calcium of plasma and were higher in sheep fed the cationic diet. Plasma osteocalcin levels were increased in sheep fed the anionic diet and cortical bone remodelling occurred in all the animals during late pregnancy in light and electron microscopy observation, but was particularly evident in the sheep fed the anionic diet. Bone turnover might be stimulated because of the role of the bone in buffering systemic acidosis. The data suggest that anionic salts ameliorated calcium metabolism around parturition by increasing bone resorption and the concentration of ionised calcium in plasma, possibly mediated by a mild hyperchloraemic metabolic acidosis

  7. A cationic surfactant-decorated liquid crystal sensing platform for simple and sensitive detection of acetylcholinesterase and its inhibitor.

    PubMed

    Wang, Yi; Hu, Qiongzheng; Guo, Yongxian; Yu, Li

    2015-10-15

    In this paper, construction of the liquid crystal (LC)-based sensing platform for simple and sensitive detection of acetylcholinesterase (AChE) and its inhibitor using a cationic surfactant-decorated LC interface was demonstrated. A change of the optical images of LCs from bright to dark appearance was observed when the cationic surfactant, myristoylcholine chloride (Myr), was transferred onto the aqueous/LC interface, due to the formation of a stable surfactant monolayer at the interface. A dark-to-bright change of the optical appearance was then observed when AChE was transferred onto the Myr-decorated LC interface. The sensitivity of this new type of LC-based sensor is 3 orders of magnitude higher in the serum albumin solution than that only in the buffer solution. Noteworthy is that the AChE LC sensor shows a very high sensitivity for the detection of the enzyme inhibitor, which is around 1 fM. The constructed low-cost LC-based sensor is quite simple and convenient, showing high promise for label-free detection of AChE and its inhibitors. PMID:25957073

  8. pH-induced motion control of self-propelled oil droplets using a hydrolyzable gemini cationic surfactant.

    PubMed

    Miura, Shingo; Banno, Taisuke; Tonooka, Taishi; Osaki, Toshihisa; Takeuchi, Shoji; Toyota, Taro

    2014-07-15

    Self-propelled motion of micrometer-sized substances has drawn much attention as an autonomous transportation system. One candidate vehicle is a chemically driven micrometer-sized oil droplet. However, to the best of our knowledge, there has been no report of a chemical reaction system controlling the three-dimensional motion of oil droplets underwater. In this study, we developed a molecular system that controlled the self-propelled motion of 4-heptyloxybenzaldehyde oil droplets by using novel gemini cationic surfactants containing carbonate linkages (2G12C). We found that, in emulsions containing sodium hydroxide, the motion time of the self-propelled oil droplets was longer in the presence of 2G12C than in the presence of gemini cationic surfactants without carbonate linkages. Moreover, in 2G12C solution, oil droplets at rest underwent unidirectional, self-propelled motion in a gradient field toward a higher concentration of sodium hydroxide. Even though they stopped within several seconds, they restarted in the same direction. 2G12C was gradually hydrolyzed under basic conditions to produce a pair of the corresponding monomeric surfactants, which exhibit different interfacial properties from 2G12C. The prolonged and restart motion of the oil droplets were explained by the increase in the heterogeneity of the interfacial tension of the oil droplets.

  9. Critical roles of cationic surfactants in the preparation of colloidal mesostructured silica nanoparticles: control of mesostructure, particle size, and dispersion.

    PubMed

    Yamada, Hironori; Urata, Chihiro; Higashitamori, Sayuri; Aoyama, Yuko; Yamauchi, Yusuke; Kuroda, Kazuyuki

    2014-03-12

    Mesoporous silica nanoparticles are promising materials for various applications, such as drug delivery and catalysis, but the functional roles of surfactants in the formation and preparation of mesostructured silica nanoparticles (MSN-as) remain to be seen. It was confirmed that the molar ratio of cationic surfactants to Si of alkoxysilanes (Surf/Si) can affect the degree of mesostructure formation (i.e., whether the mesochannels formed inside the nanoparticles actually pass through the outer surface of the particles), the particle diameter, and the dispersibility of MSN-as. Wormhole-like mesostructures formed with low Surf/Si ratios; however, the mesopores did not pass through the outer surface of the particles completely. At high Surf/Si ratios, the mesostructures extended. The particle diameter was 100 nm or larger at low Surf/Si ratios, and the primary particle diameter decreased as the Surf/Si ratio increased. This was because the surfactants enhanced the dispersity of the alkoxysilanes in water and the hydrolysis rate of the alkoxysilanes became faster, leading to an increased nucleation as compared to the particle growth. Moreover, primary particles aggregated at low Surf/Si ratios because of the hydrophobic interactions among the surfactants that were not involved in the mesostructure formation but were adsorbed onto the nanoparticles. At high Surf/Si ratios, the surfactant micelles were adsorbed on the surface of primary particles (admicelles), resulting in the dispersion of the particles due to electrostatic repulsion. In particular, molar ratios of 0.13 or higher were quite effective for the preparation of highly dispersed MSN-as. Surfactants played important roles in the mesostructure formation, decreasing the particle diameters, and the dispersibility of the particles. All of these factors were considerably affected by the Surf/Si ratio. The results suggested novel opportunities to control various colloidal mesostructured nanoparticles from the

  10. Cationic surfactants/copoly(styrene oxide ethylene oxide) systems: A physico-chemical investigation

    NASA Astrophysics Data System (ADS)

    Taboada, Pablo; Castro, Emilio; Barbosa, Silvia; Mosquera, Víctor

    2005-07-01

    The interactions between the diblock copolymer S 15E 63 and the surfactants dodecyltrimethylammonium (DoTAB) and hexadecyltrimethylammoniun (CTAB) bromides have been investigated by dynamic light scattering, transmission electron microscopy and isothermal titration calorimetry. The surfactants with the same headgroup differentiate in their chain length. At 20 °C, the block copolymer is associated into micelles with a hydrodynamic radius of 11.3 nm, which is composed of a hydrophobic styrene oxide (S) core and a water-swollen oxypolyethylene (PEO) corona. The different copolymer/surfactant systems have been studied at a constant copolymer concentration of 2.5 g dm -3 and in a vast range of surfactant concentration, from 5.0 × 10 -6 up to 0.1 M. When DoTAB is added to the block copolymer solution, no important variations are observed in the apparent hydrodynamic radius up to a surfactant concentration of ˜10 -2 M, for which this magnitude starts decreasing abruptly as a consequence of disruption of the copolymer micelles due to surfactant binding. This phenomenon is also observed for CTAB but at much lower concentrations (˜10 -5 M). This decrease is associated to repulsive electrostatic interactions between surfactant headgroups in the micelle. Complete disruption of the mixed aggregates occurs neither for DoTAB nor CTAB in the measured concentration range. Transmission electron microscopy has confirmed this behaviour. Titration calorimetric data of micellised DoTAB present a plateau region indicating no interaction between the copolymer and the surfactant at low surfactant concentrations, followed by an exothermic decrease as a consequence of starting copolymer micelle disruption. For CTAB, an endothermic maximum points out the existence of interactions between copolymer micelles and this surfactant. This maximum is followed by a steep decrease which reflects the disruption of the mixed surfactant/copolymer micelles up to a very shallow exothermic minimum from

  11. Density functional theory study of interaction, bonding and affinity of group IIb transition metal cations with nucleic acid bases

    NASA Astrophysics Data System (ADS)

    Bagchi, Sabyasachi; Mandal, Debasish; Ghosh, Deepanwita; Das, Abhijit K.

    2012-05-01

    The structure, bonding, and energetics of the complexes obtained from the interaction between the most stable tautomeric forms of free DNA and RNA bases and Zn2+, Cd2+ and Hg2+ cations have been studied using density functional B3LYP method. The 6-311+G (2df, 2p) basis set along with LANL2DZ pseudopotentials for the cations are used in the calculations. The tautomerization paths of the nucleobases are investigated and transition states between the tautomeric forms of the free bases are located. The relative stability of the complexes and the tautomers of the free nucleobases are discussed referring to MIA and relative energy values. For uracil, thymine and adenine, interaction of the metal cations with the most stable tautomers form the least stable molecular complexes. For cytosine and guanine, the stability of the metalated complexes differs significantly. The enthalpy (ΔH), entropy (TΔS) and free energy (ΔG) of the complexes at 298 K have also been calculated.

  12. Formation and characteristics of aqueous two-phase systems formed by a cationic surfactant and a series of ionic liquids.

    PubMed

    Wei, Xi-Lian; Wang, Xiu-Hong; Ping, A-Li; Du, Pan-Pan; Sun, De-Zhi; Zhang, Qing-Fu; Liu, Jie

    2013-11-15

    Aqueous two-phase systems (ATPS) were obtained in the aqueous mixtures of a cationic surfactant and a series of ionic liquids (ILs). The effects of IL structure, temperature and additives on the phase separation were systematically investigated. The microstructures of some ATPS were observed by freeze-fracture replication technique. Lyotropic liquid crystal was found in the bottom phase besides micelles under different conditions. Remarkably, both IL structure and additives profoundly affected the formation and properties of the ATPSs. The phase separation can be attributed to the existence of different aggregates and the cation-π interactions of the cationic surfactant with the ILs, which has a significant role in the formation of ATPS. The extraction capacity of the studied ATPS was also evaluated through their application in the extraction of two biosubstances. The results indicate that the ILs with BF4(-) as anion show much better extraction efficiencies than the corresponding ILs with Br(-) as anion do under the same conditions. l-Tryptophan was mainly distributed into the NPTAB-rich phase, while methylene blue and capsochrome were mainly in the IL-rich phase.

  13. Structure and performance of cationic assembly dispersed in amphoteric surfactants solution as a shampoo for hair damaged by coloring.

    PubMed

    Nagahara, Yasuo; Nishida, Yuichi; Isoda, Masanori; Yamagata, Yoshifumi; Nishikawa, Naoki; Takada, Koji

    2007-01-01

    In recent years, hair coloring gains popularity as a trend of consumer's hair care. This coloring frequently damages hair. In response to this, a new shampoo-base was developed for repairing hair damaged by coloring. The new shampoo-base was prepared by dispersing cationic assembly in a solution of amphoteric surfactants. The mixture of behenyl trimethyl ammonium chloride (C22TAC) and behenyl alcohol (C22OH) was applied as the cationic assembly, which are dispersed in amido propyl betaine laurate (LPB) solution. LPB, which behaves as an amphoteric surfactant, was used as the wash-base. It was verified from the results on the measurements of DSC, calorimeter polarization, cryo-SEM and X-ray diffraction that the cationic assembly has a crystalline structure in the LPB solution. The new shampoo-base was highly efficient to change the color-damaged hair from hydrophilic to hydrophobic. The friction level of the hair washed with the new shampoo-base recovered to the same state as that of healthy hair. The exfoliation of cuticle was reduced after washing with the new shampoo-base.

  14. Molten fatty acid based microemulsions.

    PubMed

    Noirjean, Cecile; Testard, Fabienne; Dejugnat, Christophe; Jestin, Jacques; Carriere, David

    2016-06-21

    We show that ternary mixtures of water (polar phase), myristic acid (MA, apolar phase) and cetyltrimethylammonium bromide (CTAB, cationic surfactant) studied above the melting point of myristic acid allow the preparation of microemulsions without adding a salt or a co-surfactant. The combination of SANS, SAXS/WAXS, DSC, and phase diagram determination allows a complete characterization of the structures and interactions between components in the molten fatty acid based microemulsions. For the different structures characterized (microemulsion, lamellar or hexagonal phases), a similar thermal behaviour is observed for all ternary MA/CTAB/water monophasic samples and for binary MA/CTAB mixtures without water: crystalline myristic acid melts at 52 °C, and a thermal transition at 70 °C is assigned to the breaking of hydrogen bounds inside the mixed myristic acid/CTAB complex (being the surfactant film in the ternary system). Water determines the film curvature, hence the structures observed at high temperature, but does not influence the thermal behaviour of the ternary system. Myristic acid is partitioned in two "species" that behave independently: pure myristic acid and myristic acid associated with CTAB to form an equimolar complex that plays the role of the surfactant film. We therefore show that myristic acid plays the role of a solvent (oil) and a co-surfactant allowing the fine tuning of the structure of oil and water mixtures. This solvosurfactant behaviour of long chain fatty acid opens the way for new formulations with a complex structure without the addition of any extra compound. PMID:27241163

  15. [Effect of calcium cations on acid-base properties and free radical oxidation of dopamine and pyrocatechol].

    PubMed

    Lebedev, A V; Ivanova, M V; Timoshin, A A; Ruuge, E K

    2008-01-01

    Ca2+-induced increase in the rate of pyrocatechol and dopamine oxidation by dioxygen and Ca2+-dependent acid-base properties of the catechols were studied by potentiometric titration, UV/Vis-spectrophotometry, EPR-spectroscopy, and by measurement of oxygen consumption. The effect of Ca2+ on the chain reactions of oxidation can be explained by additional deprotonation (decrease in pKai) of the catechols that accelerates one electron transport to dioxygen and formation of calcium semiquinonate, undergoing further oxidation. The described Ca2+-dependent redox-conversion of ortho-phenols proposes that an additional function of calcium in the cell can be its involvement in free radical oxidoreductive reactions at pH > pKai.

  16. Competitive solubilization of phenol by cationic surfactant micelles in the range of low additive and surfactant concentrations.

    PubMed

    Chaghi, Radhouane; de Ménorval, Louis-Charles; Charnay, Clarence; Derrien, Gaëlle; Zajac, Jerzy

    2009-05-01

    Competitive interactions of phenol (PhOH) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) against 1-butanol (BuOH) in aqueous solutions at surfactant concentrations close to the critical micelle concentration (CMC), BuOH concentration of 0.5 mmol kg(-1), and phenol contents of 1, 5, or 10 mmol kg(-1) have been investigated at 303 K by means of (1)H NMR spectroscopy, titration calorimetry, and solution conductimetry. The solubilization loci for phenol were deduced from the composition-dependence of the (1)H chemical shifts assigned to various protons in the surfactant and additive units. Since in pure HTAB solutions phenol is already in competition with Br(-), addition of 1 mmol kg(-1) NaBr to the system weakens the phenol competitiveness. The presence of butanol in the HTAB micelles causes phenol to penetrate deeper toward the hydrophobic micelle core. For higher phenol contents, the butanol molecules are constrained to remain in the bulk solution and are progressively replaced within the HTAB micelles by the aromatic units. The competitive character of phenol solubilization against butanol is well supported by changes in the thermodynamic parameters of HTAB micellization in the presence of both of the additives.

  17. Enhancement of a Lewis acid-base interaction via solvation: ammonia molecules and the benzene radical cation.

    PubMed

    Chiang, Chi-Tung; Freindorf, Marek; Furlani, Thomas; DeLeon, Robert L; Richard, John P; Garvey, James F

    2007-07-12

    The interaction between ammonia and the benzene radical cation has been investigated by gas-phase studies of mass selected ion clusters {C(6)H(6)-(NH(3))(n=0-8)}(+) via tandem quadrupole mass spectrometry and through calculations. Experiments show a special stability for the cluster ion that contains four ammonias: {C(6)H(6)(NH(3))(4)}(+). Calculations provide evidence that the first ammonia forms a weak dative bond to the cyclohexadienyl radical cation, {C(6)H(6)-NH(3)}(+), where there is a transfer of electrons from ammonia to benzene. Additional solvating ammonia molecules form stabilizing hydrogen bonds to the ring-bound ammonia {C(6)H(6)-NH(3)}(+).(NH(3))(n), which cause cooperative changes in the structure of the cluster complex. Free ammonia is a weak hydrogen bond donor, but electron transfer from NH(3) to the benzene ring that strengthens the dative bond will increase the hydrogen acidity and the strength of the cluster hydrogen bonds to the added ammonia. A progressive "tightening" of this dative bond is observed upon addition of the first, second, and third ammonia to give a cluster stabilized by three N-(+)H x N hydrogen bonds. This shows that the energetic cost of tightening the dative bond is recovered with dividends in the formation of stable cluster hydrogen bonds.

  18. Solution Behavior and Interaction of Pepsin with Carnitine Based Cationic Surfactant: Fluorescence, Circular Dichroism, and Calorimetric Studies.

    PubMed

    Ghosh, Subhajit; Dolai, Subhrajyoti; Patra, Trilochan; Dey, Joykrishna

    2015-10-01

    The present work reports the pH-induced conformational changes of pepsin in solution at room temperature. The conformational change makes the protein surface active. The protein was found to be present in the partially denatured state at pH 8 as well as at pH 2. The fluorescence probe and circular dichroism (CD) spectra suggested that the most stable state of pepsin exists at pH 5. The binding affinities of pepsin in its native and denatured states for a D,L-carnitine-based cationic surfactant (3-hexadecylcarbamoyl-2-hydroxypropyl)trimethylammonium chloride (C16-CAR) were examined at very low concentrations of the surfactant. The thermodynamics of the binding processes were investigated by use of isothermal titration calorimetry. The results were compared with those of (3-hexadecylcarbamoylpropyl)trimethylammonium chloride (C16-PTAC), which is structurally similar to C16-CAR, but without the secondary -OH functionality near the headgroup. None of the surfactants were observed to undergo binding with pepsin at pH 2, in which it exists in the acid-denatured state. However, both of the surfactants were found to spontaneously bind to the most stable state at pH 5, the partially denatured state at pH 8, and the alkaline denatured state at pH 11. Despite the difference in the headgroup structure, both of the surfactants bind to the same warfarin binding site. Interestingly, the driving force for binding of C16-CAR was found to be different from that of C16-PTC at pH ≥ 5. The steric interaction of the headgroup in C16-CAR was observed to have a significant effect on the binding process. PMID:26348532

  19. Effect of dietary cation-anion difference on ruminal metabolism, total apparent digestibility, blood and renal acid-base regulation in lactating dairy cows.

    PubMed

    Martins, C M M R; Arcari, M A; Welter, K C; Gonçalves, J L; Santos, M V

    2016-01-01

    The present study aimed to evaluate the effect of dietary cation-anion difference (DCAD) on ruminal fermentation, total apparent digestibility, blood and renal metabolism of lactating dairy cows. Sixteen Holstein cows were distributed in four contemporary 4×4 Latin Square designs, which consisted of four periods of 21 days and four treatments according to DCAD: +290; +192; +98 and -71 milliequivalent (mEq)/kg dry matter (DM). Ruminal pH and concentrations of acetic and butyric acid increased linearly according to the increase of DCAD. Similarly, NDF total apparent digestibility linearly increased by 6.38% when DCAD increased from -71 to 290 mEq/kg DM [Y=65.90 (SE=2.37)+0.0167 (SE=0.0068)×DCAD (mEq/kg DM)]. Blood pH was also increased according to DCAD, which resulted in reduction of serum concentrations of Na, K and ionic calcium (iCa). To maintain the blood acid-base homeostasis, renal metabolism played an important role in controlling serum concentrations of Na and K, since the Na and K urinary excretion increased linearly by 89.69% and 46.06%, respectively, from -71 to 290 mEq/kg DM. Changes in acid-base balance of biological fluids may directly affect the mineral composition of milk, as milk concentrations of Na, K, iCa and chlorides were reduced according to blood pH increased. Thus, it can be concluded that the increase of DCAD raises the pH of ruminal fluid, NDF total apparent digestibility, and blood pH, and decreases the milk concentration of cationic minerals, as well as the efficiency of Na utilization to milk production.

  20. Surfactant Mediated Cationic and Anionic Suspension Polymerization of PEG-Based Resins in Silicon Oil: Beaded SPOCC 1500 and POEPOP 1500.

    PubMed

    Grøtli; Rademan; Groth; Lubell; Miranda; Meldal

    2001-01-01

    A novel surfactant has been synthesized for use in cationic and anionic ring-opening suspension polymerization of PEG-based macromonomers in silicon oil. A polymer of acrylate esters containing pentamethyldisiloxane and PEG was prepared by radical polymerization. The surfactant can stabilize an emulsion of PEG-based macromonomers, initiator, and solvent in silicon oil such that polymer beads are obtained by ring-opening polymerization, initiated either by a Lewis acid (cationic ring opening) or potassium tert-butoxide (anionic ring opening). The average bead size could be controlled by varying the stirring rate and the amount of surfactant and solvent. The surfactant does not interfere with the polymerization and can be removed together with residual silicon oil by a simple washing procedure. PMID:11148061

  1. Highly precise detection, discrimination, and removal of anionic surfactants over the full pH range via cationic conjugated polymer: an efficient strategy to facilitate illicit-drug analysis.

    PubMed

    Hussain, Sameer; Malik, Akhtar H; Iyer, Parameswar K

    2015-02-11

    A water-soluble cationic conjugated polyelectrolyte (CPE), poly(1,4-bis(6-(1-methylimidazolium)-hexyloxy)-benzene bromide) (PMI) displays extraordinary stability over the full pH range of 1-14 as well as in seawater, brine, urine, and other solutions and carries out efficient detection, discrimination, and removal of moderately dissimilar anionic surfactants (viz., sodium dodecyl benzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS)) at very low levels (31.7 and 17.3 parts per billion (ppb), respectively). PMI formed stable hydrogels in the presence of SDS that remained unaffected by strong acids/bases, heating, ultrasonication, or exposure to light, whereas SDBS formed precipitate with PMI as a result of its different interpolymer cofacial arrangement via Columbic attraction. The complex-forming ability of PMI with SDS and SDBS facilitated their elimination from water or drug-doped urine samples without the use of any organic solvent, chromatographic technique, or solid support. This protocol, the first of its kind for the removal of anionic surfactants at very low concentrations from any type of solution and competitive environments, demonstrates an original application using a CPE. The surfactant-free sample solutions could be precisely analyzed for the presence of illicit drugs by any standard methods. Using PMI, a newly developed CPE, a rapid and practical method for the efficient detection, discrimination, and removal of SDS and SDBS at ppb levels from water and urine, under harsh conditions, and in natural chemical environments is demonstrated.

  2. Highly precise detection, discrimination, and removal of anionic surfactants over the full pH range via cationic conjugated polymer: an efficient strategy to facilitate illicit-drug analysis.

    PubMed

    Hussain, Sameer; Malik, Akhtar H; Iyer, Parameswar K

    2015-02-11

    A water-soluble cationic conjugated polyelectrolyte (CPE), poly(1,4-bis(6-(1-methylimidazolium)-hexyloxy)-benzene bromide) (PMI) displays extraordinary stability over the full pH range of 1-14 as well as in seawater, brine, urine, and other solutions and carries out efficient detection, discrimination, and removal of moderately dissimilar anionic surfactants (viz., sodium dodecyl benzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS)) at very low levels (31.7 and 17.3 parts per billion (ppb), respectively). PMI formed stable hydrogels in the presence of SDS that remained unaffected by strong acids/bases, heating, ultrasonication, or exposure to light, whereas SDBS formed precipitate with PMI as a result of its different interpolymer cofacial arrangement via Columbic attraction. The complex-forming ability of PMI with SDS and SDBS facilitated their elimination from water or drug-doped urine samples without the use of any organic solvent, chromatographic technique, or solid support. This protocol, the first of its kind for the removal of anionic surfactants at very low concentrations from any type of solution and competitive environments, demonstrates an original application using a CPE. The surfactant-free sample solutions could be precisely analyzed for the presence of illicit drugs by any standard methods. Using PMI, a newly developed CPE, a rapid and practical method for the efficient detection, discrimination, and removal of SDS and SDBS at ppb levels from water and urine, under harsh conditions, and in natural chemical environments is demonstrated. PMID:25588321

  3. Synthesis of Multibranched Gold Nanoechinus Using a Gemini Cationic Surfactant and Its Application for Surface Enhanced Raman Scattering.

    PubMed

    Vijayaraghavan, Priya; Liu, Cheng-Hong; Hwang, Kuo Chu

    2016-09-14

    High-yield multibranched Au nanoechinus possessing lengthy and dense branched nanorods on the surface were synthesized using a seed-mediated surfactant-directed approach in the presence of gemini cationic surfactant N,N,N'N'-tetramethyl-N,N'-ditetradecylethane-1,2-diaminium bromide (C14C2C14Br2), HAuCl4, AgNO3, and ascorbic acid. C14C2C14Br2 surfactant provides a versatile template in designing the unique morphology of Au nanoechinus with the assistance of AgNO3. UV-vis spectroscopic analysis proves that Au nanoechinus possess a unique intense broad localized surface plasmon resonance (LSPR) peak, which extends from 400 to 1700 nm in the NIR region making a highly potential platform for biomedical applications. Systematic time-dependent TEM, UV-vis-NIR, and XRD analysis were performed to monitor the morphological evolution of multibranched Au nanoechinus. It was found that the surface of branched nanorods of Au NE preferentially grew along (111) crystal planes. Furthermore, as-synthesized Au nanoechinus shows excellent SERS enhancement ability for dopamine inside HeLa cells. PMID:27556284

  4. Synthesis and antimicrobial activity of polysaccharide alginate derived cationic surfactant-metal(II) complexes.

    PubMed

    Tawfik, Salah M; Hefni, Hassan H

    2016-01-01

    New natural polysaccharide carbohydrate derivatives of sodium alginate surfactant and its cobalt, copper and zinc complexes were synthesized. Structures of the synthesized compounds are reported using FTIR, (1)H NMR and UV-vis. The critical micelle concentration (CMC) value of the alginate surfactant and its metal complexes in aqueous solution was found out from surface tension measurements. Surface tension data at different temperatures served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔGmic, ΔHmic, ΔSmic) and adsorption (ΔGads, ΔGads, ΔSads). The surface activities of the synthesized polymeric surfactant and its metal complexes were influenced by their chemical structures and the type of the transition metals. These compounds were evaluated against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and fungi (Candida albicans and Asperigllus niger). The antibacterial and antifungal screening tests of the alginate surfactant metal complexes have shown good results compared to its precursor alginate surfactant.

  5. Growth Behavior, Geometrical Shape, and Second CMC of Micelles Formed by Cationic Gemini Esterquat Surfactants.

    PubMed

    Bergström, L Magnus; Tehrani-Bagha, Alireza; Nagy, Gergely

    2015-04-28

    Micelles formed by novel gemini esterquat surfactants have been investigated with small-angle neutron scattering (SANS). The growth behavior of the micelles is found to differ conspicuously depending on the length of the gemini surfactant spacer group. The gemini surfactant with a long spacer form rather small triaxial ellipsoidal tablet-shaped micelles that grow weakly with surfactant concentration in the entire range of measured concentrations. Geminis with a short spacer, on the other hand, form weakly growing oblates or tablets at low concentrations that start to grow much more strongly into polydisperse rodlike or wormlike micelles at higher concentrations. The latter behavior is consistent with the presence of a second CMC that marks the transition from the weakly to the strongly growing regime. It is found that the growth behavior in terms of aggregation number as a function of surfactant concentration always appear concave in weakly growing regimes, while switching to convex behavior in strongly growing regimes. As a result, we are able to determine the second CMC of the geminis with short spacer by means of suggesting a rather precise definition of it, located at the point of inflection of the growth curve that corresponds to the transition from concave to convex growth behavior. Our SANS results are rationalized by comparison with the recently developed general micelle model. In particular, this theory is able to explain and reproduce the characteristic appearances of the experimental growth curves, including the presence of a second CMC and the convex strongly growing regime beyond. By means of optimizing the agreement between predictions from the general micelle model and results from SANS experiments, we are able to determine the three bending elasticity constants spontaneous curvature, bending rigidity, and saddle-splay constant for each surfactant. PMID:25835031

  6. [Effect of univalent cations on synthesis of surfactants by Acinetobacter calcoaceticus IMV B-7241].

    PubMed

    Pirog, T P; Shevchuk, T A; Antoniuk, S I; Kravchenko, E Iu; Iutinskaia, G A

    2013-01-01

    The effect of univalent cations on activity of key enzymes of C2-metabolism has been investigated in the producer of biosurfactants, Acinetibacter calcoaceticus IMV B-7241 grown on ethanol. It was established that potassium cations are inhibitors of pyroquinolinequinone-dependent alcohol- and acetaldehyde dehydrogenases, the enzymes of biosynthesis of surface-active aminolipids (NADP-dependent glutamate dehydrogenase) and glycolipids (phosphoenopyruvate (PhEP)-carboxikinase), while ammonium cations are activators of these enzymes and PhEP-carboxylase. A decrease of potassium cations concentration in the cultivation medium to 1 mM and increase of the content of amine nitrogen to 10 mM as a result of potassium nitrate substitution by equimolar, as to nitrogen, urea concentration were accompanied by the increase of activity of enzymes of ethanol metabolism and SAS biosynthesis, as well as by the 2-fold increase of conditional concentration of the biosurfactants.

  7. Cationic liposomes formulated with DMPC and a gemini surfactant traverse the cell membrane without causing a significant bio-damage.

    PubMed

    Stefanutti, E; Papacci, F; Sennato, S; Bombelli, C; Viola, I; Bonincontro, A; Bordi, F; Mancini, G; Gigli, G; Risuleo, G

    2014-10-01

    Cationic liposomes have been intensively studied both in basic and applied research because of their promising potential as non-viral molecular vehicles. This work was aimed to gain more information on the interactions between the plasmamembrane and liposomes formed by a natural phospholipid and a cationic surfactant of the gemini family. The present work was conducted with the synergistic use of diverse experimental approaches: electro-rotation measurements, atomic force microscopy, ζ-potential measurements, laser scanning confocal microscopy and biomolecular/cellular techniques. Electro-rotation measurements pointed out that the interaction of cationic liposomes with the cell membrane alters significantly its dielectric and geometric parameters. This alteration, being accompanied by significant changes of the membrane surface roughness as measured by atomic force microscopy, suggests that the interaction with the liposomes causes locally substantial modifications to the structure and morphology of the cell membrane. However, the results of electrophoretic mobility (ζ-potential) experiments show that upon the interaction the electric charge exposed on the cell surface does not vary significantly, pointing out that the simple adhesion on the cell surface of the cationic liposomes or their fusion with the membrane is to be ruled out. As a matter of fact, confocal microscopy images directly demonstrated the penetration of the liposomes inside the cell and their diffusion within the cytoplasm. Electro-rotation experiments performed in the presence of endocytosis inhibitors suggest that the internalization is mediated by, at least, one specific pathway. Noteworthy, the liposome uptake by the cell does not cause a significant biological damage.

  8. Cationic liposomes formulated with DMPC and a gemini surfactant traverse the cell membrane without causing a significant bio-damage.

    PubMed

    Stefanutti, E; Papacci, F; Sennato, S; Bombelli, C; Viola, I; Bonincontro, A; Bordi, F; Mancini, G; Gigli, G; Risuleo, G

    2014-10-01

    Cationic liposomes have been intensively studied both in basic and applied research because of their promising potential as non-viral molecular vehicles. This work was aimed to gain more information on the interactions between the plasmamembrane and liposomes formed by a natural phospholipid and a cationic surfactant of the gemini family. The present work was conducted with the synergistic use of diverse experimental approaches: electro-rotation measurements, atomic force microscopy, ζ-potential measurements, laser scanning confocal microscopy and biomolecular/cellular techniques. Electro-rotation measurements pointed out that the interaction of cationic liposomes with the cell membrane alters significantly its dielectric and geometric parameters. This alteration, being accompanied by significant changes of the membrane surface roughness as measured by atomic force microscopy, suggests that the interaction with the liposomes causes locally substantial modifications to the structure and morphology of the cell membrane. However, the results of electrophoretic mobility (ζ-potential) experiments show that upon the interaction the electric charge exposed on the cell surface does not vary significantly, pointing out that the simple adhesion on the cell surface of the cationic liposomes or their fusion with the membrane is to be ruled out. As a matter of fact, confocal microscopy images directly demonstrated the penetration of the liposomes inside the cell and their diffusion within the cytoplasm. Electro-rotation experiments performed in the presence of endocytosis inhibitors suggest that the internalization is mediated by, at least, one specific pathway. Noteworthy, the liposome uptake by the cell does not cause a significant biological damage. PMID:25017801

  9. Adsorptive removal of cationic surfactants from aqueous solutions onto high-area activated carbon cloth monitored by in situ UV spectroscopy.

    PubMed

    Duman, Osman; Ayranci, Erol

    2010-02-15

    Activated carbon cloth (ACC) was used as adsorbent for the removal of cationic surfactants such as benzyltrimethylammonium chloride (BTMACl), benzyltriethylammonium chloride (BTEACl), benzyltributylammonium chloride (BTBACl), benzyldimethyldecylammonium chloride (BDMDACl), benzyldimethyltetradecyl ammonium chloride (BDMTDACl), benzyldimethylhexadecylammonium chloride (BDMHDACl), N-dodecylpyridinium chloride (N-DPCl) and N-cetylpyridinium chloride (CPCl) from aqueous solutions. The adsorption efficiency of the ACC was evaluated for cationic surfactants. Adsorption process was followed by in situ UV spectroscopic technique. The kinetic data, so obtained, were treated according to the pseudo first-order, the pseudo second-order, the Elovich and the intraparticle diffusion models in order to understand the adsorption mechanism of cationic surfactants onto the ACC. The best fit was found with the pseudo second-order model. The experimental isotherm data were obtained at 30 degrees C and analyzed by the Freundlich and the Langmuir models. The parameters of isotherm equations were determined. The Freundlich model was found to represent the experimental data better than the Langmuir model. The observed adsorption behaviors are discussed in terms of the pH of the solution, the nature of cationic surfactants (e.g. functional groups, size, and hydrophobicity) and the nature of the ACC (e.g. surface charge, pore size). A fair linear correlation was found between some adsorption parameters and apparent molar volumes at infinite dilution for benzyltrialkylammonium chlorides. PMID:19815343

  10. Fabrication, stability and efficacy of dual-component antimicrobial nanoemulsions: essential oil (thyme oil) and cationic surfactant (lauric arginate).

    PubMed

    Chang, Yuhua; McLandsborough, Lynne; McClements, David Julian

    2015-04-01

    The influence of a cationic surfactant (lauric arginate, LAE) on the physical properties and antimicrobial efficacy of thyme oil nanoemulsions was investigated. Nanoemulsions prepared from pure thyme oil were highly unstable due to Ostwald ripening, but they could be stabilized by adding a ripening inhibitor (corn oil) to the oil phase prior to homogenisation. The loading capacity and antimicrobial efficacy of thyme oil nanoemulsions were significantly increased by adding LAE. In the absence of LAE, at least 60 wt% corn oil had to be added to the lipid phase to inhibit Ostwald ripening; but in the presence of 0.1 wt% LAE, only 30 wt% corn oil was needed. LAE addition substantially increased the antimicrobial efficacy of the thyme oil nanoemulsions: 200 μg/ml thyme oil was needed to inhibit growth of a spoilage yeast (Zygosaccharomyces bailii) if LAE was added, whereas ⩾ 400 μg/ml was needed in the absence of LAE.

  11. Influence of a cationic surfactant on adsorption of p-nitrophenol by a magsorbent based on magnetic alginate beads.

    PubMed

    Obeid, Layaly; El Kolli, Nadia; Talbot, Delphine; Welschbillig, Mathias; Bée, Agnès

    2015-11-01

    The paper focuses on the removal of p-nitrophenol by an adsorption process. A magnetic adsorbent was synthesized by encapsulation of magnetic functionalized nanoparticles using alginate as a green biopolymer matrix. A cationic surfactant, cetylpyridinium chloride (CPyCl), was used to confer a hydrophobic character to the magnetic beads and thus to promote their adsorption efficiency. The effect of different parameters such as initial concentrations of both PNP and CPyCl, contact time and solution pH value on the adsorption of PNP in the presence of CPyCl was investigated. It should be noted that combination of magnetic and adsorption properties in a same material is an interesting challenge which could overcome the recovery problems of pollutant-loaded adsorbent. PMID:26188728

  12. Effect of various surfactants (cationic, anionic and non-ionic) on the growth of Aspergillus parasiticus (NRRL 2999) in relation to aflatoxin production.

    PubMed

    Tanuja, Kosuri; Hemalatha, K; Karuna, Rupula; Sashidhar Rao, B

    2010-08-01

    The effect of surfactants (two cationic, one anionic and three non-ionic) at 0.001, 0.01, 0.1 and 1.0 % concentrations on aflatoxin production, ergosterol content and sugar consumption by Aspergillus parasiticus (NRRL 2999) in YES liquid culture medium is reported. At 0.01% concentration, the cationic surfactants, cetyl dimethyl ammonium bromide (CDAB) and dodecyl trimethyl ammonium bromide (DTAB), and the anionic surfactant, sodium dodecyl sulfate (SDS), completely inhibited spore germination, while DTAB also inhibited the production of ergosterol and toxin (p < 0.05). At a concentration of 0.001%, CDAB was found to enhance toxin production, while SDS was found to inhibit it when compared with other surfactants. Non-ionic surfactants, polyoxyethylene sorbitan monolaurate (Tween-20), polyoxyethylene lauryl ether (Brij-35) and ethoxylated p-tert-octylphenol (Triton X-100) delayed the spore germination up to day 5 at all concentrations and inhibited toxin and ergosterol production at 0.001% concentration. The affect was found to be dose-dependent from 0.001% to 1%, for Triton X-100 only. Positive correlation between ergosterol content and toxin production in the presence of different surfactants at various time periods (3, 5, 7, 9 and 12 days) was found. Tween-20 was most effective in inhibiting toxin production on day 7, when aflatoxin production was found to be maximal in control group. Sugar consumption was directly proportional to the ergosterol content, showing a significant correlation with aflatoxin production.

  13. Effect of alkane chain length and counterion on the freezing transition of cationic surfactant adsorbed film at alkane mixture - water interfaces.

    PubMed

    Tokiwa, Yuhei; Sakamoto, Hiroyasu; Takiue, Takanori; Aratono, Makoto; Matsubara, Hiroki

    2015-05-21

    Penetration of alkane molecules into the adsorbed film gives rise to a surface freezing transition of cationic surfactant at the alkane-water interface. To examine the effect of the alkane chain length and counterion on the surface freezing, we employed interfacial tensiometry and ellipsometry to study the interface of cetyltrimethylammonium bromide and cetyltrimethylammonium chloride aqueous solutions against dodecane, tetradecane, hexadecane, and their mixtures. Applying theoretical equations to the experimental results obtained, we found that the alkane molecules that have the same chain length as the surfactant adsorb preferentially into the surface freezing film. Furthermore, we demonstrated that the freezing transition temperature of cationic surfactant adsorbed film was independent of the kind of counterion. PMID:25932500

  14. Sorption-desorption of 1,2,4-trichlorobenzene on soil: Anionic surfactant and cationic polyelectrolyte effects

    SciTech Connect

    DiVincenzo, J.P.; Dentel, S.K.

    1996-11-01

    Anionic surfactants and cationic polymers are two classes of anthropogenic chemicals that are released to the environment in significant amounts. In particular, this occurs in the land disposal of sludges, potentially altering the terrestrial mobility of other contaminants such as hydrophobic organics. Thus, we examined the 1,2,4-trichlorobenzene (TCB) sorption-desorption on soil with sodium dodecyl sulfate (SDS) and/or a cationic polyelectrolyte (Percol 757) present. Initial experiments varying sorbent mass resulted in nonconstant partitioning and a nonlinear isotherm; a model of incomplete colloidal separation by centrifugation could not explain the nonlinearity. A proposed model quantifies this isotherm behavior with a BET isotherm equation related to the limiting sorption capacity of the organic matter phase, Q{sub om}{degrees}. Additions of SDS and/or polyelectrolyte led to significant changes in TCB sorption. The SDS decreased TCB sorption significantly, but only with SDS exceeding the critical micelle concentration (CMC). The CMC value itself varied with electrolyte and soil presence. Increasing the SDS concentration above the CMC caused TCB desorption from soil. The SDS also increased residual colloidal solids, but primarily below the CMC. Percol 757 slightly increased TCP sorption. With polymer added to soil containing SDS, TCB sorption was unaffected until charge equivalence was approached, whereupon sorption increased severalfold. This trend reversed when the SDS exceeded the sum of the polymer equivalence and the CMC. These results are explained in terms of polymer-surfactant interactions. Environmental implications include effects on transport of hydrophobic organics resulting form sludge disposal on land. 27 refs., 10 figs.

  15. Ion chromatographic determination of hydroxide ion on monolithic reversed-phase silica gel columns coated with nonionic and cationic surfactants.

    PubMed

    Xu, Qun; Mori, Masanobu; Tanaka, Kazuhiko; Ikedo, Mikaru; Hu, Wenzhi; Haddad, Paul R

    2004-07-01

    The determination of hydroxide by ion chromatography (IC) is demonstrated using a monolithic octadecylsilyl (ODS)-silica gel column coated first with a nonionic surfactant (polyoxyethylene (POE)) and then with a cationic surfactant (cetyltrimethylammonium bromide (CTAB)). This stationary phase, when used in conjunction with a 10 mmol/l sodium sulfate eluent at pH 8.2, was found to be suitable for the rapid and efficient separation of hydroxide from some other anions, based on a conventional ion-exchange mechanism. The peak directions and detection responses for these ions were in agreement with their known limiting equivalent ionic conductance values. Under these conditions, a linear calibration plot was obtained for hydroxide ion over the range 16 micromol/l to 15 mmol/l, and the detection limit determined at a signal-to-noise ratio of 3 was 6.4 micromol/l. The double-coated stationary phase described above was shown to be superior to a single coating of cetyltrimethylammonium bromide alone, in terms of separation efficiency and stability of the stationary phase. A range of samples comprising solutions of some strong and weak bases was analyzed by the proposed method and the results obtained were in good agreement with those obtained by conventional potentiometric pH measurement.

  16. Non-ionic surfactant modified cationic liposomes mediated gene transfection in vitro and in the mouse lung.

    PubMed

    Ding, Wuxiao; Izumisawa, Tomohiro; Hattori, Yoshiyuki; Qi, Xianrong; Kitamoto, Dai; Maitani, Yoshie

    2009-02-01

    As reported previously, cationic liposomes formulated with dioleoylphosphatidylethanolamine (DOPE) and N,N-methyl hydroxyethyl aminopropane carbamoyl cholesterol (MHAPC-liposomes) achieved efficient gene transfection in the mouse lung following intratracheal injection. We have studied here the role of surfactants, mannosylerythritol lipid-A (MEL-A) and polysorbate 80 (Tween 80), in affecting gene transfection of MHAPC-lipoplexes (complex with pCMV-luc DNA) in A549 cells and in the mouse lung. MEL-A increased gene transfection of MHAPC-lipoplexes significantly in vitro and slightly in the mouse lung, while Tween 80 decreased it both in vitro and in vivo. As assessed by confocal laser scanning microscopy and fluorescence imaging, MEL-A might faciliate gene dissociation from MHAPC-lipoplexes with fluorescein-labeled oligodeoxynucleotide (FITC-ODN) after internalization into the cells and retained the lipoplexes in the mouse lung for prolonged time, while Tween 80 was inefficient to deliver foreign gene into target cells and in the lung. These results demonstrated that MEL-A is advantageous to Tween 80 in the modification of cationic liposomes as gene delivery vectors in the lung. PMID:19182397

  17. Different thermal unfolding pathways of catalase in the presence of cationic surfactants.

    PubMed

    Blanco, Elena; Ruso, Juan M; Prieto, Gerardo; Sarmiento, Félix

    2007-03-01

    In this paper we have corroborated the usefulness of spectroscopic techniques, such as UV-visible, in the study and thermodynamic characterization of the thermal unfolding of catalase as a function of the concentration and alkyl chain length of n-alkyltrimethylammonium bromides (CnTAB, n = 8, 10, and 12). For this reason, a thermodynamic model was used which included experimental data corresponding to the pre- and posttransition into the observable transition. It has been found that n-alkyltrimethylammonium bromides play two opposite roles in the folding and stability of catalase. They act as a structure stabilizer at a low molar concentration and as a destabilizer at a higher concentration. The maximum of the unfolding temperature has been found to decrease with the alkyl chain. The reason for this difference has been suggested to be the side chains involved. In the presence of C8TAB and C10TAB, Gibbs energies of unfolding (DeltaG(T)) decrease with concentration, whereas for C12TAB an increase has been observed. These findings can be explained by the fact that when differences in the hydrophobic nature of the surfactants exist, different pathways of unfolding may occur. Also, the presence of surfactants has been observed to affect the cold denaturation of catalase. Thermodynamic results suggest that the thermal denaturation of catalase in the presence of n-alkyltrimethylammonium bromides is a perfect transition between two states.

  18. Nanostructurated complexes of poly(beta,L-malate) and cationic surfactants: synthesis, characterization and structural aspects.

    PubMed

    Portilla-Arias, José A; García-Alvarez, Montserrat; Martínez de Ilarduya, Antxon; Holler, Eggerhard; Muñoz-Guerra, Sebastián

    2006-01-01

    Ionic complexes of microbially produced poly(beta,L-malic acid) and alkyltrimethylammonium surfactants with linear alkyl chains containing even numbers of carbon atoms from 14 up to 22, were investigated. Complexes with a stoichiometric or nearly stoichiometric composition were prepared by precipitation from equimolar mixtures of aqueous solutions of the two components. All complexes were found to adopt supramolecular stratified structures made of alternating layers of poly(beta,L-malate) and surfactant with a periodicity on the length scale of 3-5 nm, which increased proportionally to the length of the polymethylene chain. In these complexes, alkyl side chains with more than 16 carbon atoms were partially crystallized showing reversible melting at temperatures between 40 and 70 degrees C. After melting, a smectic LC phase that isotropicized at approximately 100 degrees C was observed for all of the complexes. Conformational and dimensional changes taking place in the complexes by effect of heating were analyzed by (13)C CP-MAS NMR and powder X-ray diffraction.

  19. Role of cationic and nonionic surfactants on biocidal efficiency in diesel-water interface.

    PubMed

    Muthukumar, N; Maruthamuthu, S; Palaniswamy, N

    2007-06-15

    Biodegradation occurs at the interface between diesel and water. The microbial contamination can result in inhibitor/fuel degradation that leads to the unacceptable level of turbidity, filter plugging, corrosion of storage tanks, pipeline and souring of stored products. Hence, selection of biocides/inhibitors is an important aspect in petroleum product transporting pipeline. Three biocides (cationic and nonionic) were employed to study the biodegradation of diesel in diesel-water interface. The biocidal efficiency on biodegradation of diesel was examined using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and gas chromatography mass spectrometry (GC-MS). Polyoxyethyleneglycol dodecyl ether [BRIJ-35] and polyethylene glycol-p-isooctylphenyl ether [TRITON-X-100] had higher bactericidal efficiency than Dodecyl ethyl dimethyl ammonium bromide [DDAB]. But the cationic biocide (DDAB) gave good biocidal efficiency at the interface. The data are explained in terms of a model that postulates the formation of "micelle" at the diesel-water interface. PMID:17363228

  20. Cationic vesicles of a carnitine-derived single-tailed surfactant: physicochemical characterization and evaluation of in vitro gene transfection efficiency.

    PubMed

    Patra, Trilochan; Ghosh, Subhajit; Dey, Joykrishna

    2014-12-15

    Spontaneous vesicle formation in water by single-chain surfactants is rare. Here we show that in aqueous solution, a single-chain cationic surfactant 3-(dodecylcarbamoyl-2-hydroxypropyl)-trimethylammonium chloride (C12-CAR) derived from D,L-carnitine spontaneously forms vesicles with hydrodynamic diameters in the range of 30-70 nm. A detailed self-assembly study of the C12-CAR surfactant was performed for the first time by use of a combination of techniques, including surface tension, conductivity, fluorescence probe, dynamic light scattering and transmission electron microscopy. The cationic surfactant was found to have a reasonably low critical aggregation concentration (3.4±0.2 mM) in water at 298 K. The vesicles were observed to be stable at the physiological temperature (310 K) over a long period of time. Although the vesicles formed were found to be unstable and exhibit vesicle-to-tubule transition in the presence of salt, in the presence of 10 mol% cholesterol the stability of vesicles is enhanced. When compared with lipofectamine-2000, the C12-CAR was found to act as an effective gene transfection agent in COS-1 cell line. The surfactant-DNA complex was also found to be nontoxic toward CHO cells. PMID:25268817

  1. Comparative studies on the crystalline to fluid phase transitions of two equimolar cationic/anionic surfactant mixtures containing dodecylsulfonate and dodecylsulfate.

    PubMed

    Wu, Fu-Gen; Yu, Ji-Sheng; Sun, Shu-Feng; Yu, Zhi-Wu

    2011-12-20

    In this work, a cationic surfactant, dodecyltrimethylammonium bromide (DTAB), and an anionic surfactant, sodium dodecylsulfonate (SDSO(3)) or sodium dodecylsulfate (SDSO(4)), were mixed in an equimolar ratio to prepare SDSO(3)-DTAB and SDSO(4)-DTAB binary mixtures. The phase behavior, structure, and morphology of these two surfactant mixtures were investigated by differential scanning calorimetry, synchrotron X-ray scattering, freeze-fracture electron microscopy, and Fourier transform infrared spectroscopy. It was found that upon heating, both of the two systems transform from multilamellar crystalline phase to liquid crystalline (or fluid) phase. It is interesting to find that, although SDSO(3) has a lower molecular weight, the crystalline phase of SDSO(3)-DTAB shows much higher thermostability as compared with that of SDSO(4)-DTAB. Other than this, we observed a large difference in the repeat distances of the two crystalline phases. More interestingly, at 60 °C in the fluid phases, cylindrical micelles formed in the SDSO(3)-DTAB system, while spherical micelles were observed in the SDSO(4)-DTAB system. Our present work demonstrates that a subtle difference in the headgroup structure of the anionic component markedly affects the thermostability, packing structure, and morphology of the surfactant mixtures, which suggests the importance of the match of the head-head and tail-tail interactions between the cationic and anionic surfactants.

  2. A novel viscoelastic system from a cationic surfactant and a hydrophobic counterion.

    PubMed

    Abdel-Rahem, R; Gradzielski, M; Hoffmann, H

    2005-08-15

    The phase behavior of 2-hydroxy-1-naphthoic acid (2,1-HNC) mixed with cetyltrimethylammonium hydroxide (CTAOH) is reported. This novel system is compared with the published one of 3-hydroxy-2-naphthoic acid (3,2-HNC) mixed with CTAOH. We investigated the phase behavior and properties of the phases in aqueous solutions of 100 mM CTAOH with 2,1-HNC. In both systems a multilamellar vesicle phase is formed when the naphthoate/surfactant ratio (r) reaches unity. When an increasing amount of 2,1-HNC is mixed with a micellar solution of 100 mM CTAOH, an isotropic low-viscous micellar solution, a viscoelastic gel (consisting of rodlike micelles), a turbid region (two-phase region), and a viscoelastic liquid crystalline gel (consisting of multilamellar vesicles, MLV) were formed. The vesicular phase is highly viscoelastic and has a yield stress value. The transition from the micellar to the vesicle phase occurs for CTAOH/2,1-HNC over a two-phase region, where micelles and vesicles coexist. Also it was noticed that 2,1-HNC is dissolved in 100 mM CTAOH until the naphthoate/surfactant ratio reaches approximately 1.5, and the liquid crystalline phases were found to change their color systematically when they were viewed between two crossed polarizers. The vesicles have been characterized by differential interference contrast microscopy, freeze-fracture electron microscopy, and cryo-electron microscopy (cryo-TEM). The vesicles were polydisperse and their diameter ranged from 100 to 1000 nm. The interlamellar spacing between the bilayers was determined with small angle neutron scattering and agrees with the results from different microscopical methods. The complex viscosity rises by six orders of magnitude when rodlike micelles are formed. The complex viscosity decreases again in the turbid region, and then rises approximately six orders of magnitude above the water viscosity. This second rising is due to the formation of the liquid crystalline MLV phase.

  3. Photoinduced formation of threadlike micelles from mixtures of a cationic surfactant and a stilbene amphiphile.

    PubMed

    Takahashi, Yutaka; Kishimoto, Mai; Kondo, Yukishige

    2016-05-15

    This study examined the influence of ultraviolet (UV) irradiation on aqueous surfactant solutions containing an anionic stilbene derivative (sodium [4-[(E)-2-(4-butylphenyl)ethenyl]phenoxy]acetate; C4StilNa) as a photoresponsive skeleton. Prior to UV irradiation, an aqueous solution of cetyltrimethylammonium bromide (CTAB) and C4StilNa was a low-viscosity fluid forming spheroidal micelles. Exposure of the low-viscosity fluid to UV light resulted in the formation of threadlike micelles and an increase in the viscosity of the aqueous CTAB/C4StilNa solution. (1)H nuclear magnetic resonance spectroscopy indicated that the photochemically induced isomerization and dimerization reactions of C4StilNa molecules had occurred in the aggregates due to UV irradiation. Overall, the structural transformation of the stilbene groups in the C4StilNa molecules with the photochemical reactions leads to an increase in the critical packing parameter and consequently a photoinduced transition of spheroidal micelles to threadlike micelles. PMID:26967168

  4. Modification of the charge transport properties of the copper phthalocyanine/poly(vinyl alcohol) interface using cationic or anionic surfactant for field-effect transistor performance enhancement

    NASA Astrophysics Data System (ADS)

    Jastrombek, Diana; Nawaz, Ali; Koehler, Marlus; Meruvia, Michelle S.; Hümmelgen, Ivo A.

    2015-08-01

    We report on the performance enhancement of organic field-effect transistors prepared using cross-linked poly(vinyl alcohol) as gate dielectric and copper phthalocyanine as channel semiconductor through gate dielectric surface treatment. The gate dielectric surface was treated using either a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB), or an anionic surfactant, sodium dodecyl sulfate (SDS). We determined the charge-carrier field-effect mobility ( μ FET) in these transistors as a function of the effective channel thickness in the channel bottleneck, near to the transistor source. When compared to the untreated devices, in the devices treated with CTAB or SDS, the channel formation occurs at lower gate voltage and the carrier mobility in the thinnest channel region, corresponding to the immediate vicinity of the insulator/semiconductor interface, is significantly higher. The surfactant treatment leads to a tenfold increase in μ FET and significant enhancement in capacitance, on/off current ratio and transconductance of the transistor.

  5. Study on the effect of chain-length compatibility of mixed anionic-cationic surfactants on the cloud-point extraction of selected organophosphorus pesticides.

    PubMed

    Seebunrueng, Ketsarin; Santaladchaiyakit, Yanawath; Srijaranai, Supalax

    2012-09-01

    The chain-length compatibility of mixed anionic-cationic surfactants was investigated for the extraction of organophosphorus pesticides (OPPs). Cationic surfactants with different chain lengths (n = 12 and 16) were mixed with sodium dodecyl sulfate (SDS; n = 12) for the mixed anionic-cationic surfactants-based extraction. Six OPPs were studied including azinphos-methyl, parathion-methyl, fenitrothion, diazinon, chlorpyrifos, and prothiophos. Reversed-phase high-performance liquid chromatography was used for the determination of the studied OPPs. The extraction was performed using mixtures of SDS and cationic surfactants including dodecyltrimethyl ammonium bromide or dodecyltrimethylammonium bromide (DTAB; n = 12) and cetyltrimethyl ammonium bromide or cetyltrimethyl ammonium bromide (CTAB; n = 16). The parameters affecting the extraction efficiencies of two extraction systems were studied and discussed. The optimum condition for SDS-DTAB was 15 mmol L(-1) SDS and 1 mmol L(-1) DTAB in the presence of 15% (w/v) sodium chloride (NaCl). Meanwhile, the condition for SDS-CTAB was 10 mmol L(-1) SDS and 1.0 mmol L(-1) CTAB with 10% (w/v) NaCl. Under the optimum conditions, the extraction efficiency of SDS-DTAB (66-85%) was slightly higher than that of SDS-CTAB (61-82%). In addition, the SDS-DTAB system also gave greater enrichment factor than SDS-CTAB for all the studied OPPs. This result may be due to the compatibility of chain length between SDS and DTAB. The extraction using SDS-DTAB was successfully applied to determine OPPs in fruit samples (i.e., pomelo, apple, and pineapple). No contamination by the studied OPPs in samples was observed. Good accuracy with recoveries ranging from 77 to 105% was obtained. Low limits of detection were in the range of 0.003-0.01 mg kg(-1) which are below the MRLs established by EU-MRLs for the OPPs residues in fruit samples.

  6. Field study of methidathion in soil amended with biosolid and a cationic surfactant under different irrigation regimes. Solute transport modeling.

    PubMed

    Sánchez, L; Romero, E; Castillo, A; Peña, A

    2006-04-01

    Four experimental plots located in Granada (Spain) were used to investigate the potential movement of the insecticide methidathion during three treatments in a period of three years. To increase pesticide soil retention a municipal biosolid and the cationic surfactant, tetradecyl trimethyl ammonium bromide (TDTMA), were used as soil amendments. The presence of the insecticide was monitored in soil and water samples at different depths up to one meter. Soil solution was sampled by ceramic suction cups installed at three depths (25, 75 and 100 cm). No effect of the amendments on pesticide mobility was observed. Experimental results showed that pesticide leaching occurred in the upper soil layer. Although some sporadic high water soil concentrations were found, these were attributed to preferential flow processes. This was confirmed by the absence of high pesticide concentration in soil samples at similar depths. Pesticide mobility was mainly affected by the irrigation employed. Experimental results were compared with theoretical data simulated with the mathematical model FocusPelmo. The resemblance between theoretical and experimental soil data seems to confirm the preferential flow processes. Otherwise, the lack of fit between the soil water data were attributed to the ceramic devices employed, that could suffer an "ageing process" which would cause bias in the determinations. PMID:16216306

  7. A solid phase extraction-ion chromatography with conductivity detection procedure for determining cationic surfactants in surface water samples.

    PubMed

    Olkowska, Ewa; Polkowska, Żaneta; Namieśnik, Jacek

    2013-11-15

    A new analytical procedure for the simultaneous determination of individual cationic surfactants (alkyl benzyl dimethyl ammonium chlorides) in surface water samples has been developed. We describe this methodology for the first time: it involves the application of solid phase extraction (SPE-for sample preparation) coupled with ion chromatography-conductivity detection (IC-CD-for the final determination). Mean recoveries of analytes between 79% and 93%, and overall method quantification limits in the range from 0.0018 to 0.038 μg/mL for surface water and CRM samples were achieved. The methodology was applied to the determination of individual alkyl benzyl quaternary ammonium compounds in environmental samples (reservoir water) and enables their presence in such types of waters to be confirmed. In addition, it is a simpler, less time-consuming, labour-intensive, avoiding use of toxic chloroform and significantly less expensive methodology than previously described approaches (liquid-liquid extraction coupled with liquid chromatography-mass spectrometry).

  8. Fabrication of tin-cobalt/carbon composite electrodes by electrodeposition using cationic surfactant for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Lee, Cho-Long; Nam, Do-Hwan; Eom, Ji-Yong; Kwon, Hyuk-Sang

    2016-07-01

    Sn-Co alloy and Sn-Co/C composite are fabricated on the nodule-type Cu substrate by co-electrodeposition process using the pulse current in the pyrophosphate bath, and then their cycling performances are examined. To modify the surface property of carbon (acetylene black) particles and improve the dispersion of agglomerated carbon particles, CTAB (Cetrimonium bromide (C16H33)N(CH3)3Br) as a cationic surfactant is added into the electrodeposition bath.10.1007/s13391-016-6077-2 By addition of the CTAB, the amount of the carbon content in the Sn-Co/C composite is increased, and also the carbon particles are uniformly distributed in the Sn-Co electrodeposit. The Sn0.6Co0.4 alloy and (Sn0.6Co0.4)0.71/C0.29 composite are obtained after annealing as the final products. The (Sn0.6Co0.4)0.71/C0.29 composite anode exhibits better the capacity retention than the Sn0.6Co0.4 alloy anode due primarily to the role of the well-dispersed carbon particles as the second buffer phase and electrical conductive path in the Sn-Co/C composite during cycling.

  9. Synthesis of Environmentally Friendly Highly Dispersed Magnetite Nanoparticles Based on Rosin Cationic Surfactants as Thin Film Coatings of Steel

    PubMed Central

    Atta, Ayman M.; El-Mahdy, Gamal A.; Al-Lohedan, Hamad A.; Al-Hussain, Sami A.

    2014-01-01

    This work presents a new method to prepare monodisperse magnetite nanoparticles capping with new cationic surfactants based on rosin. Core/shell type magnetite nanoparticles were synthesized using bis-N-(3-levopimaric maleic acid adduct-2-hydroxy) propyl-triethyl ammonium chloride (LPMQA) as capping agent. Fourier transform infrared spectroscopy (FTIR) was employed to characterize the nanoparticles chemical structure. Transmittance electron microscopies (TEM) and X-ray powder diffraction (XRD) were used to examine the morphology of the modified magnetite nanoparticles. The magnetite dispersed aqueous acid solution was evaluated as an effective anticorrosion behavior of a hydrophobic surface on steel. The inhibition effect of magnetite nanoparticles on steel corrosion in 1 M HCl solution was investigated using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Results obtained from both potentiodynamic polarisation and EIS measurements reveal that the magnetite nanoparticle is an effective inhibitor for the corrosion of steel in 1.0 M HCl solution. Polarization data show that magnetite nanoparticles behave as a mixed type inhibitor. The inhibition efficiencies obtained from potentiodynamic polarization and EIS methods are in good agreement. PMID:24758936

  10. Synthesis of environmentally friendly highly dispersed magnetite nanoparticles based on rosin cationic surfactants as thin film coatings of steel.

    PubMed

    Atta, Ayman M; El-Mahdy, Gamal A; Al-Lohedan, Hamad A; Al-Hussain, Sami A

    2014-04-22

    This work presents a new method to prepare monodisperse magnetite nanoparticles capping with new cationic surfactants based on rosin. Core/shell type magnetite nanoparticles were synthesized using bis-N-(3-levopimaric maleic acid adduct-2-hydroxy) propyl-triethyl ammonium chloride (LPMQA) as capping agent. Fourier transform infrared spectroscopy (FTIR) was employed to characterize the nanoparticles chemical structure. Transmittance electron microscopies (TEM) and X-ray powder diffraction (XRD) were used to examine the morphology of the modified magnetite nanoparticles. The magnetite dispersed aqueous acid solution was evaluated as an effective anticorrosion behavior of a hydrophobic surface on steel. The inhibition effect of magnetite nanoparticles on steel corrosion in 1 M HCl solution was investigated using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Results obtained from both potentiodynamic polarisation and EIS measurements reveal that the magnetite nanoparticle is an effective inhibitor for the corrosion of steel in 1.0 M HCl solution. Polarization data show that magnetite nanoparticles behave as a mixed type inhibitor. The inhibition efficiencies obtained from potentiodynamic polarization and EIS methods are in good agreement.

  11. Acute toxicity of the cationic surfactant C12-benzalkonium in different bioassays: how test design affects bioavailability and effect concentrations.

    PubMed

    Chen, Yi; Geurts, Marc; Sjollema, Sascha B; Kramer, Nynke I; Hermens, Joop L M; Droge, Steven T J

    2014-03-01

    Using an ion-exchange-based solid-phase microextraction (SPME) method, the freely dissolved concentrations of C12-benzalkonium were measured in different toxicity assays, including 1) immobilization of Daphnia magna in the presence or absence of dissolved humic acid; 2) mortality of Lumbriculus variegatus in the presence or absence of a suspension of Organisation for Economic Co-Operation and Development (OECD) sediment; 3) photosystem II inhibition of green algae Chlorella vulgaris; and 4) viability of in vitro rainbow trout gill cell line (RTgill-W1) in the presence or absence of serum proteins. Furthermore, the loss from chemical adsorption to the different test vessels used in these tests was also determined. The C12-benzalkonium sorption isotherms to the different sorbent phases were established as well. Our results show that the freely dissolved concentration is a better indicator of the actual exposure concentration than the nominal or total concentration in most test assays. Daphnia was the most sensitive species to C12-benzalkonium. The acute Daphnia and Lumbriculus tests both showed no enhanced toxicity from possible ingestion of sorbed C12-benzalkonium in comparison with water-only exposure, which is in accordance with the equilibrium partitioning theory. Moreover, the present study demonstrates that commonly used sorbent phases can strongly affect bioavailability and observed effect concentrations for C12-benzalkonium. Even stronger effects of decreased actual exposure concentrations resulting from sorption to test vessels, cells, and sorbent phases can be expected for more hydrophobic cationic surfactants. PMID:24273010

  12. Fabrication of tin-cobalt/carbon composite electrodes by electrodeposition using cationic surfactant for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Lee, Cho-Long; Nam, Do-Hwan; Eom, Ji-Yong; Kwon, Hyuk-Sang

    2016-09-01

    Sn-Co alloy and Sn-Co/C composite are fabricated on the nodule-type Cu substrate by co-electrodeposition process using the pulse current in the pyrophosphate bath, and then their cycling performances are examined. To modify the surface property of carbon (acetylene black) particles and improve the dispersion of agglomerated carbon particles, CTAB (Cetrimonium bromide (C16H33)N(CH3)3Br) as a cationic surfactant is added into the electrodeposition bath.10.1007/s13391-016-6077-2 By addition of the CTAB, the amount of the carbon content in the Sn-Co/C composite is increased, and also the carbon particles are uniformly distributed in the Sn-Co electrodeposit. The Sn0.6Co0.4 alloy and (Sn0.6Co0.4)0.71/C0.29 composite are obtained after annealing as the final products. The (Sn0.6Co0.4)0.71/C0.29 composite anode exhibits better the capacity retention than the Sn0.6Co0.4 alloy anode due primarily to the role of the well-dispersed carbon particles as the second buffer phase and electrical conductive path in the Sn-Co/C composite during cycling.

  13. Microporous membrane liquid-liquid extraction coupled on-line with normal-phase liquid chromatography for the determination of cationic surfactants in river and waste water.

    PubMed

    Norberg, J; Thordarson, E; Mathiasson, L; Jönsson, J A

    2000-02-11

    Membrane-based continuous liquid-liquid extraction combined on-line with normal-phase liquid chromatography is proposed for the determination of cationic surfactants in complex aqueous samples. The technique has the potential for complete automation. Selective enrichment of cationic surfactants from spiked river water and waste-water samples with simultaneous removal of matrix constituents, followed by a quantitative transfer of the extract onto a liquid chromatographic column and separation of the surfactant homologues yielding low detection limits, has been realised. The homologues of alkyldimethylbenzylammonium chloride (Dodigen 226) were chosen as model compounds in the method development. Dodigen homologues were ion-paired with heptanoic acid and extracted into chlorobutane by means of microporous membrane liquid-liquid extraction. It was thereby possible to attain an enrichment of over 250 times for one of the homologues, viz. the concentration in the organic liquid is 250 times higher than in the original sample. Detection limits for the three best-detected homologues of the mixture were in the range 0.7-5 microg/l in spiked river water samples. Ion-pair normal-phase liquid chromatography, again with heptanoic acid as counter-ion, gave the necessary separation of the surfactant homologues.

  14. Synthesis of double-wall nanoscrolls intercalated with polyfluorinated cationic surfactant into layered niobate and their magnetic alignment.

    PubMed

    Nabetani, Yu; Uchikoshi, Akino; Miyajima, Souki; Hassan, Syed Zahid; Ramakrishnan, Vivek; Tachibana, Hiroshi; Yamato, Masafumi; Inoue, Haruo

    2016-04-28

    The orientation of nanomaterials with an anisotropic nature such as nanoscrolls is very important for realizing their efficient and sophisticated functions in devices, including nanostructured electrodes in artificial photosynthetic cells. In this study, we successfully synthesized a nanoscroll by intercalation of a cationic polyfluorinated surfactant into the interlayer spaces of layered niobate and successfully controlled its orientation by applying an external magnetic field in water. The exfoliated niobate nanosheets were efficiently rolled-up to form nanoscrolls, which have a fine layered structure (d020 = 3.64 nm), by mixing with heptafluorobutanoylaminoethylhexadecyldimethylammonium bromide (C3F-S) in water, whereas the corresponding hydrocarbon analogue (C3H-S) did not form nanoscrolls. The synthetic yield for the purified and isolated nanoscrolls from the nanosheets was estimated to be 62% by weight. It was confirmed by atomic force microscopy (AFM) that most of the niobate nanosheets (98%) were converted to nanoscrolls. An external magnetic field was applied to the nanoscrolls to force them to align. After the magnetic treatment, the orientation of the nanoscrolls was investigated by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The non-uniform ring distribution of the SAXS patterns indicates that the nanoscrolls dispersed in water were aligned well on applying the magnetic field. The long axis of the nanoscroll was oriented in the direction of the applied field and long nanoscrolls were aligned more efficiently. When the intercalated C3F-S molecules were removed from the nanoscrolls by treating with an acid, the resultant nanoscrolls did not exhibit magnetic alignment, strongly suggesting that C3F-S plays an important role in the orientation control of the nanoscrolls by the magnetic field. PMID:27074750

  15. Interaction between cationic surfactant of 1-methyl-3-tetradecylimidazolium bromide and anionic polymer of sodium polystyrene sulfonate

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Kang, Wenpei; Sun, Dezhi; Liu, Jie; Wei, Xilian

    2013-08-01

    The interaction between long-chain imidazolium ionic liquid (C14mimBr) and anionic polyelectrolyte of sodium polystyrene sulfonate (NaPSS) has been studied using surface tension, isothermal titration microcalorimetry (ITC), dynamic light scatting (DLS) and conductance methods. The result shows that the surface tension plots have a pronounced hump in the surface tension at surfactant concentrations below the critical micelle concentration (cmc) of the surfactant. The cooperative adsorption of surfactant and polymer on the surface (PSS) and the formation of polymer/surfactant aggregate in bulk solution (PSM) provide a rational explanation about it. The formation of surfactant/polymer complexes is affected by the concentration of the surfactant or NaPSS, which is also ascertained by ITC and DLS measurements. Further, the thermodynamic parameters are derived from calorimetric titration and conductance curves, and the effects of polymer concentration and temperature on the parameters are evaluated in detail.

  16. Enhancement of soil retention for phenanthrene in binary cationic gemini and nonionic surfactant mixtures: characterizing two-step adsorption and partition processes through experimental and modeling approaches.

    PubMed

    Zhao, Shan; Huang, Gordon; An, Chunjiang; Wei, Jia; Yao, Yao

    2015-04-01

    The enhancement of soil retention for phenanthrene (PHE) through the addition of a binary mixture of cationic gemini (12-2-12) and nonionic surfactants (C12E10) was investigated. The maximum apparent sorption coefficient Kd(*) reached 4247.8 mL/g through the addition of mixed 12-2-12 gemini and C12E10 surfactants, which was markedly higher than the summed individual results in the presence of individual 12-2-12 gemini (1148.6 mL/g) or C12E10 (210.0 mL/g) surfactant. However, the sorption of 12-2-12 gemini was inhibited by the increasing C12E10 dose; and a higher initial 12-2-12 gemini dose showed a higher "desorption" rate. The present study also addressed the sorption behavior of the single 12-2-12 gemini surfactant at the soil/aqueous interface. The sorption isotherm was divided into two steps to elucidate the sorption process; and the sorption schematics were proposed to elaborate the growth of surfactant aggregates corresponding to the various steps of the sorption isotherm. Finally, a two-step adsorption and partition model (TAPM) was developed to simulate the sorption process. Analysis of the equilibrium data indicated that the sorption isotherms of 12-2-12 gemini fitted the TAPM model better. Thermodynamic calculations confirmed that the 12-2-12 gemini sorption at the soil/aqueous interface was spontaneous and exothermic from 288 to 308K. PMID:25576782

  17. Surface forces between titanium dioxide surfaces in the presence of cationic surfactant as a function of surfactant concentration, electrolyte concentration, and pH.

    PubMed

    Walsh, Rick B; Wu, Bo; Howard, Shaun C; Craig, Vincent S J

    2014-03-18

    Titanium dioxide (titania) surfaces produced by atomic layer deposition (ALD) are suitable for surfactant adsorption and surface force measurements. Adsorption isotherms for cetyltrimethylammonium bromide (CTAB) on ALD titanium dioxide surfaces were measured using optical reflectometry (OR), and surface force measurements between ALD titanium dioxide surfaces in aqueous CTAB solutions were measured using the colloid probe technique at different pH and electrolyte concentrations. Measurements were performed at a range of concentrations below and above the common intersection point (CIP) where adsorption is dominated by electrostatic and hydrophobic interactions, respectively. An examination of surfactant adsorption above and below the isoelectric point (IEP) was performed. Interestingly, significant levels of adsorption were observed below the IEP where the electrostatic interactions are unfavorable. The adsorption results are used to interpret the force data, which is dependent upon the amount of surfactant adsorbed and the electrolyte concentration and pH. The surface force data is compared to DLVO theory. Poor fits are obtained when Lifshitz theory is used to describe the dispersion forces. However, all of the data are fit well with a dispersion force of reduced magnitude. The kinetics of adsorption was measured and reveals very slow adsorption kinetics below the critical micelle concentration as a result of the monomer-by-monomer formation of aggregates on the surface.

  18. Warm white light emitting ThO{sub 2}:Sm{sup 3+} nanorods: Cationic surfactant assisted reverse micellar synthesis and Photoluminescence properties

    SciTech Connect

    Gupta, Santosh K.; Gupta, Ruma; Natarajan, V.; Godbole, S.V.

    2014-01-01

    Graphical abstract: - Highlights: • ThO{sub 2}:Sm{sup 3+} nanoparticles have been synthesized using cationic surfactant assisted reverse micellar route. • HRTEM shows the formation of thoria nanorods. • Photoluminescence investigation shows host as well as samarium ion emission. • Time resolved fluorescence spectroscopy shows the presence of two types of samarium ion in thoria host. - Abstract: Sm{sup 3+} activated thorium oxide nanorods were synthesized by cationic surfactant assisted reverse micellar route. Phase purity, morphological and luminescent properties were investigated by X-ray diffraction, high resolution transmission electron microscopy and photoluminescence spectroscopy. Upon UV light excitation (245 nm), ThO{sub 2}:Sm{sup 3+} exhibited host emission at 447 nm, along with characteristic emission lines of Sm{sup 3+} at 569, 609, 662 and 716 nm. Lifetime spectroscopy shows the presence of two types of Sm{sup 3+} (τ = 1.1 ms and 4.9 ms) with different asymmetric ratios.

  19. Interaction of cationic surfactant cethyltrimethylammonium bromide with bovine serum albumin in dependence on pH: A study of tryptophan fluorescence

    NASA Astrophysics Data System (ADS)

    Vlasova, Irina M.; Zhuravleva, Valeria V.; Vlasov, Alexander A.; Saletsky, Alexander M.

    2013-02-01

    The interaction of cationic surfactant cethyltrimethylammonium bromide (CTAB) with bovine serum albumin (BSA) at various values of pH has been studied using steady-state non-polarized tryptophan fluorescence of BSA and polarized tryptophan fluorescence of BSA. By analysis of intensity of tryptophan fluorescence of BSA, by analysis of position of maximum of spectrum of BSA tryptophan fluorescence, by analysis of polarization of BSA tryptophan fluorescence the qualitative rearrangements of BSA globules at denaturation under action of CTAB are registered. The estimation of parameters of rotational diffusion of BSA molecules helps one to determine the quantitative changes of size of BSA at CTAB-induced denaturation. It is shown that denaturation of BSA, taking place at interaction of cationic surfactant CTAB with BSA, has one-stage mono-phase character. At interaction of CTAB with BSA the deepest denaturation of BSA is reached at 4 mM CTAB (at pH 3.5-8.0). More intensive denaturation of BSA under action of CTAB takes place at values of pH, higher than the isoelectric point of BSA.

  20. Wetting effects versus ion pairs diffusivity: interactions of anionic surfactants with highly soluble cationic drugs and its impact on tablet dissolution.

    PubMed

    Desai, Divyakant; Wong, Benjamin; Huang, Yande; Ye, Qingmei; Guo, Hang; Huang, Ming; Timmins, Peter

    2015-07-01

    A study was conducted to develop a mechanistic understanding of dissolution of a highly soluble cationic drug, metformin hydrochloride, under the influence of anionic surfactants, sodium alkyl sulfates. The surfactants did not influence the saturated solubility of the drug, but reduced the surface tension of the dissolution media as the alkyl chain length increased. Their influence on tablet wetting based on the contact angles did not show any trend. The dissolution of 850 mg metformin hydrochloride tablets in 0.1 N HCl and pH 4.5 acetate buffer with 0.01% (w/v) sodium n-octyl sulfate (C8), sodium n-decyl sulfate (C10), or sodium n-tetradecyl sulfate (C14) was similar to the control, but was enhanced by sodium lauryl sulfate (C12). At 0.1% (w/v) concentration, the dissolution was not enhanced by C12 because the reduction in surface tension was counterbalanced by an increase in hydrophobic ion pairs that showed slower diffusivity by nuclear magnetic resonance. At 0.1% (w/v), metformin also formed an insoluble salt (1:2 molar ratios) with C10 (pH 1.2), C12, and C14 (pH 1.2 and 4.5) but not with C8. Three competing factors influenced the drug dissolution by surfactants: reduction in surface tension of the dissolution media, ion pairs with low diffusivity, and formation of an insoluble salt. PMID:26017286

  1. Experimental-Theoretical Approach to the Adsorption Mechanisms for Anionic, Cationic, and Zwitterionic Surfactants at the Calcite-Water Interface.

    PubMed

    Durán-Álvarez, Agustín; Maldonado-Domínguez, Mauricio; González-Antonio, Oscar; Durán-Valencia, Cecilia; Romero-Ávila, Margarita; Barragán-Aroche, Fernando; López-Ramírez, Simón

    2016-03-22

    The adsorption of surfactants (DTAB, SDS, and CAPB) at the calcite-water interface was studied through surface zeta potential measurements and multiscale molecular dynamics. The ground-state polarization of surfactants proved to be a key factor for the observed behavior; correlation was found between adsorption and the hard or soft charge distribution of the amphiphile. SDS exhibits a steep aggregation profile, reaching saturation and showing classic ionic-surfactant behavior. In contrast, DTAB and CAPB featured diversified adsorption profiles, suggesting interplay between supramolecular aggregation and desorption from the solid surface and alleviating charge buildup at the carbonate surface when bulk concentration approaches CMC. This manifests as an adsorption profile with a fast initial step, followed by a metastable plateau and finalizing with a sharp decrease and stabilization of surface charge. Suggesting this competition of equilibria, elicited at the CaCO3 surface, this study provides atomistic insight into the adsorption mechanism for ionic surfactants on calcite, which is in accordance with experimental evidence and which is a relevant criterion for developing enhanced oil recovery processes.

  2. Effect of Base Stacking on the Acid-Base Properties of the Adenine Cation Radical [A•+] in Solution: ESR and DFT Studies

    PubMed Central

    Adhikary, Amitava; Kumar, Anil; Khanduri, Deepti

    2015-01-01

    In this study, the acid–base properties of the adenine cation radical are investigated by means of experiment and theory. Adenine cation radical (A•+) is produced by one-electron oxidation of dAdo and of the stacked DNA-oligomer (dA)6 by Cl2•− in aqueous glass (7.5 M LiCl in H2O and in D2O) and investigated by ESR spectroscopy. Theoretical calculations and deuterium substitution at C8–H and N6–H in dAdo aid in our assignments of structure. We find the pKa value of A•+ in this system to be ca. 8 at 150 K in seeming contradiction to the accepted value of ≤ 1 at ambient temperature. However, upon thermal annealing to ≥160 K, complete deprotonation of A•+ occurs in dAdo in these glassy systems even at pH ca. 3. A•+ found in (dA)6 at 150 K also deprotonates on thermal annealing. The stability of A•+ at 150 K in these systems is attributed to charge delocalization between stacked bases. Theoretical calculations at various levels (DFT B3LYP/6-31G*, MPWB95, and HF-MP2) predict binding energies for the adenine stacked dimer cation radical of 12 to 16 kcal/mol. Further DFT B3LYP/6-31G* calculations predict that, in aqueous solution, monomeric A•+ should deprotonate spontaneously (a predicted pKa of ca. −0.3 for A•+). However, the charge resonance stabilized dimer AA•+ is predicted to result in a significant barrier to deprotonation and a calculated pKa of ca. 7 for the AA•+ dimer which is 7 pH units higher than the monomer. These theoretical and experimental results suggest that A•+ isolated in solution and A•+ in adenine stacks have highly differing acid–base properties resulting from the stabilization induced by hole delocalization within adenine stacks. PMID:18611019

  3. Modification of an Iranian clinoptilolite nano-particles by hexadecyltrimethyl ammonium cationic surfactant and dithizone for removal of Pb(II) from aqueous solution.

    PubMed

    Anari-Anaraki, Mostafa; Nezamzadeh-Ejhieh, Alireza

    2015-02-15

    Natural clinoptilolite tuff was mechanically converted to micro (MCP) and nano (NCP) particles. The MCP and NCP powders were respectively modified with hexadecyltrimethyl ammonium bromide (HDTMA) and dithizone (DTZ). The raw and modified samples were characterized by X-ray diffraction (XRD), Fourier transformation infra red (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) and thermogravimetry (TG) and used for the removal of Pb(II) from aqueous solution. The results confirm that both ion exchange and complexation processes are responsible for removal of Pb(II) cations in the modified samples, while Pb(II) cations were only removed via an ion exchange process by the raw clinoptilolite. In this sorbent, the anionic removal property of surfactant modified zeolites (SMZs) changed to cationic removal property by an additional modification step. The best removal efficiency was observed by NCP-HDTMA-DTZ at the following experimental conditions: C(Pb(II)): 800 mg L(-1), HDTMA dosage: 0.2 mol L(-1), DTZ dosage: 5 mmol L(-1), contact time of DTZ with NCP-HDTMA: 1800 min and contact time of the sorbent with Pb(II): 360 min. The NCP-HDTMA-DTZ sorbent showed good efficiency for the removal of lead in the presence of different multivalent cations. Adsorption isotherms of Pb(II) ions obey the Langmuir equation that indicate the monolayer sorption of Pb(II). The adsorption kinetics based on the pseudo-second-order rate equation indicates that the rate limiting step involving a chemical reaction. The negative ΔH and ΔG indicate an exothermic and spontaneous process. PMID:25460715

  4. Modification of an Iranian clinoptilolite nano-particles by hexadecyltrimethyl ammonium cationic surfactant and dithizone for removal of Pb(II) from aqueous solution.

    PubMed

    Anari-Anaraki, Mostafa; Nezamzadeh-Ejhieh, Alireza

    2015-02-15

    Natural clinoptilolite tuff was mechanically converted to micro (MCP) and nano (NCP) particles. The MCP and NCP powders were respectively modified with hexadecyltrimethyl ammonium bromide (HDTMA) and dithizone (DTZ). The raw and modified samples were characterized by X-ray diffraction (XRD), Fourier transformation infra red (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) and thermogravimetry (TG) and used for the removal of Pb(II) from aqueous solution. The results confirm that both ion exchange and complexation processes are responsible for removal of Pb(II) cations in the modified samples, while Pb(II) cations were only removed via an ion exchange process by the raw clinoptilolite. In this sorbent, the anionic removal property of surfactant modified zeolites (SMZs) changed to cationic removal property by an additional modification step. The best removal efficiency was observed by NCP-HDTMA-DTZ at the following experimental conditions: C(Pb(II)): 800 mg L(-1), HDTMA dosage: 0.2 mol L(-1), DTZ dosage: 5 mmol L(-1), contact time of DTZ with NCP-HDTMA: 1800 min and contact time of the sorbent with Pb(II): 360 min. The NCP-HDTMA-DTZ sorbent showed good efficiency for the removal of lead in the presence of different multivalent cations. Adsorption isotherms of Pb(II) ions obey the Langmuir equation that indicate the monolayer sorption of Pb(II). The adsorption kinetics based on the pseudo-second-order rate equation indicates that the rate limiting step involving a chemical reaction. The negative ΔH and ΔG indicate an exothermic and spontaneous process.

  5. Thermodynamic and spectroscopic investigation of interactions between reactive red 223 and reactive orange 122 anionic dyes and cetyltrimethyl ammonium bromide (CTAB) cationic surfactant in aqueous solution.

    PubMed

    Irfan, Muhammad; Usman, Muhammad; Mansha, Asim; Rasool, Nasir; Ibrahim, Muhammad; Rana, Usman Ali; Siddiq, Mohammad; Zia-Ul-Haq, Muhammad; Jaafar, Hawa Z E; Khan, Salah Ud-Din

    2014-01-01

    The present study describes the conductometric and spectroscopic study of the interaction of reactive anionic dyes, namely, reactive red 223 and reactive orange 122 with the cationic surfactant cetyltrimethyl ammonium bromide (CTAB). In a systematic investigation, the electrical conductivity data was used to calculate various thermodynamic parameters such as free energy (ΔG), enthalpy (ΔH), and the entropy (ΔS) of solubilization. The trend of change in these thermodynamic quantities indicates toward the entropy driven solubilization process. Moreover, the results from spectroscopic data reveal high degree of solubilization, with strong interactions observed in the cases of both dyes and the CTAB. The spontaneous nature of solubilization and binding was evident from the observed negative values of free energies (ΔG p and ΔG b).

  6. Thermodynamic and spectroscopic investigation of interactions between reactive red 223 and reactive orange 122 anionic dyes and cetyltrimethyl ammonium bromide (CTAB) cationic surfactant in aqueous solution.

    PubMed

    Irfan, Muhammad; Usman, Muhammad; Mansha, Asim; Rasool, Nasir; Ibrahim, Muhammad; Rana, Usman Ali; Siddiq, Mohammad; Zia-Ul-Haq, Muhammad; Jaafar, Hawa Z E; Khan, Salah Ud-Din

    2014-01-01

    The present study describes the conductometric and spectroscopic study of the interaction of reactive anionic dyes, namely, reactive red 223 and reactive orange 122 with the cationic surfactant cetyltrimethyl ammonium bromide (CTAB). In a systematic investigation, the electrical conductivity data was used to calculate various thermodynamic parameters such as free energy (ΔG), enthalpy (ΔH), and the entropy (ΔS) of solubilization. The trend of change in these thermodynamic quantities indicates toward the entropy driven solubilization process. Moreover, the results from spectroscopic data reveal high degree of solubilization, with strong interactions observed in the cases of both dyes and the CTAB. The spontaneous nature of solubilization and binding was evident from the observed negative values of free energies (ΔG p and ΔG b). PMID:25243216

  7. Adsorption isotherms and structure of cationic surfactants adsorbed on mineral oxide surfaces prepared by atomic layer deposition.

    PubMed

    Wangchareansak, Thipvaree; Craig, Vincent S J; Notley, Shannon M

    2013-12-01

    The adsorption isotherms and aggregate structures of adsorbed surfactants on smooth thin-film surfaces of mineral oxides have been studied by optical reflectometry and atomic force microscopy (AFM). Films of the mineral oxides of titania, alumina, hafnia, and zirconia were produced by atomic layer deposition (ALD) with low roughness. We find that the surface strongly influences the admicelle organization on the surface. At high concentrations (2 × cmc) of cetyltrimethylammonium bromide (CTAB), the surfactant aggregates on a titania surface exhibit a flattened admicelle structure with an average repeat distance of 8.0 ± 1.0 nm whereas aggregates on alumina substrates exhibit a larger admicelle with an average separation distance of 10.5 ± 1.0 nm. A wormlike admicelle structure with an average separation distance of 7.0 ± 1.0 nm can be observed on zirconia substrates whereas a bilayered aggregate structure on hafnia substrates was observed. The change in the surface aggregate structure can be related to an increase in the critical packing parameter through a reduction in the effective headgroup area of the surfactant. The templating strength of the surfaces are found to be hafnia > alumina > zirconia > titania. Weakly templating surfaces are expected to have superior biocompatibility.

  8. Fluorescence of aminofluoresceins as an indicative process allowing one to distinguish between micelles of cationic surfactants and micelle-like aggregates

    NASA Astrophysics Data System (ADS)

    Mchedlov-Petrossyan, Nikolay O.; Cheipesh, Tatiana A.; Roshal, Alexander D.; Doroshenko, Andrey O.; Vodolazkaya, Natalya A.

    2016-09-01

    Among the vast set of fluorescein derivatives, the double charged R2‑ anions of aminofluoresceins are known to exhibit only low quantum yields of fluorescence, \\varphi . The \\varphi value becomes as high as that of the fluorescein dianion when the lone electron pair of the amino group is involved in a covalent bond. According to Munkholm et al (1990 J. Am. Chem. Soc. 112 2608–12), a much smaller increase in the emission intensity can be observed in the presence of surfactant micelles. However, all these observations refer to aqueous or alcoholic solvents. In this paper, we show that in the non-hydrogen bond donor (or ‘aprotic’) solvents DMSO and acetone, the quantum yields, φ, of the 4‧- (or 5‧)-aminofluorescein R2‑ species amount to 61–67% and approach that of fluorescein (φ  =  87%), whereas in water φ is only 0.6–0.8%. In glycerol, a solvent with an extremely high viscosity, the φ value is only 6–10%. We report on the enhancement of the fluorescence of the aminofluorescein dianions as an indicative process, which allows us to distinguish between the micelle-like aggregates of cationic dendrimers of low generation, common spherical surfactant micelles, and surfactant bilayers. Some of these colloidal aggregates partly restore the fluorescence of aminofluoresceins in aqueous media. By contrast, other positively charged micellar-like aggregates do not enhance the quantum yield of aminofluorescein R2‑ species. Results for several related systems, such as CTAB-coated SiO2 particles and reverse microemulsions, are briefly described, and the possible reasons for the observed phenomena are discussed.

  9. Fluorescence of aminofluoresceins as an indicative process allowing one to distinguish between micelles of cationic surfactants and micelle-like aggregates

    NASA Astrophysics Data System (ADS)

    Mchedlov-Petrossyan, Nikolay O.; Cheipesh, Tatiana A.; Roshal, Alexander D.; Doroshenko, Andrey O.; Vodolazkaya, Natalya A.

    2016-09-01

    Among the vast set of fluorescein derivatives, the double charged R2- anions of aminofluoresceins are known to exhibit only low quantum yields of fluorescence, \\varphi . The \\varphi value becomes as high as that of the fluorescein dianion when the lone electron pair of the amino group is involved in a covalent bond. According to Munkholm et al (1990 J. Am. Chem. Soc. 112 2608-12), a much smaller increase in the emission intensity can be observed in the presence of surfactant micelles. However, all these observations refer to aqueous or alcoholic solvents. In this paper, we show that in the non-hydrogen bond donor (or ‘aprotic’) solvents DMSO and acetone, the quantum yields, φ, of the 4‧- (or 5‧)-aminofluorescein R2- species amount to 61-67% and approach that of fluorescein (φ  =  87%), whereas in water φ is only 0.6-0.8%. In glycerol, a solvent with an extremely high viscosity, the φ value is only 6-10%. We report on the enhancement of the fluorescence of the aminofluorescein dianions as an indicative process, which allows us to distinguish between the micelle-like aggregates of cationic dendrimers of low generation, common spherical surfactant micelles, and surfactant bilayers. Some of these colloidal aggregates partly restore the fluorescence of aminofluoresceins in aqueous media. By contrast, other positively charged micellar-like aggregates do not enhance the quantum yield of aminofluorescein R2- species. Results for several related systems, such as CTAB-coated SiO2 particles and reverse microemulsions, are briefly described, and the possible reasons for the observed phenomena are discussed.

  10. Effect of alkali cations on two-dimensional networks of two new quaternary thioarsenates (III) prepared by a facile surfactant-thermal method

    NASA Astrophysics Data System (ADS)

    Yan, Dongming; Hou, Peipei; Liu, Chang; Chai, Wenxiang; Zheng, Xuerong; Zhang, Luodong; Zhi, Mingjia; Zhou, Chunmei; Liu, Yi

    2016-09-01

    Two new quaternary thioarsenates(III) NaAg2AsS3·H2O (1) and KAg2AsS3 (2) with high yields have been successfully prepared through a facile surfactant-thermal method. It is interesting that 2 can only be obtained with the aid of ethanediamine (en), which indicates that weak basicity of solvent is beneficial to the growth of 2 compared with 1. Both 1 and 2 feature the similar two-dimensional (2D) layer structures. However, the distortion of the primary honeycomb-like nets in 2 is more severe than that of 1, which demonstrates that Na+ and K+ cations have different structure directing effects on these two thioarsenates(III). Both experimental and theoretical studies confirm 1 and 2 are semiconductors with band gaps in the visible region. Our success in preparing these two quaternary thioarsenates(III) proves that surfactant-thermal technique is a powerful yet facile synthetic method to explore new complex chalcogenides.

  11. Fabric softeners: nearly instantaneous characterization and quality control of cationic surfactants by easy ambient sonic-spray ionization mass spectrometry.

    PubMed

    Saraiva, Sérgio A; Abdelnur, Patrícia V; Catharino, Rodrigo R; Nunes, George; Eberlin, Marcos N

    2009-02-01

    A tiny droplet of typical samples of fabric softeners from different commercial brands placed on a smooth paper surface was subjected to easy ambient sonic-spray ionization mass spectrometry (EASI-MS). With no need for sample-preparation or pre-separation procedures, EASI-MS and EASI-MS/MS identify nearly instantaneously the main surfactants and the homologous series employed in their formulations. Adulterated and low quality samples containing no or less efficient softeners are also easily recognized. PMID:19127530

  12. Formation, characterization and enzyme activity in water-in-hydrophobic ionic liquid microemulsion stabilized by mixed cationic/nonionic surfactants.

    PubMed

    Sun, Yanwen; Yan, Keqian; Huang, Xirong

    2014-10-01

    The phase behavior of the pseudo ternary system 1-tetradecyl-3-methylimidazolium bromide ([C14mim]Br)/Triton X-100/H2O/1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) has been studied at 35°C. With the increase in the mole fraction of Triton X-100 in the mixed surfactants, the water solubilization capacity increases and the monophasic area enlarges. The H2O-in-[Bmim]PF6 (W/IL) microemulsion was identified via electrical conductivity measurement. The existence of bulk water in the W/IL microemulsion was demonstrated based on the change of the O-D vibration frequency with content of D2O added and confirmed using UV-vis technique with CoCl2 as probe. Laccase can be solubilized in the W/IL microemulsion and exhibits a catalytic activity. The interface of the W/IL microemulsion has an inhibitory effect on the expression of the laccase activity, and the inhibitory effect is varied with the molar ratio of the mixed surfactants.

  13. Formation, characterization and enzyme activity in water-in-hydrophobic ionic liquid microemulsion stabilized by mixed cationic/nonionic surfactants.

    PubMed

    Sun, Yanwen; Yan, Keqian; Huang, Xirong

    2014-10-01

    The phase behavior of the pseudo ternary system 1-tetradecyl-3-methylimidazolium bromide ([C14mim]Br)/Triton X-100/H2O/1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) has been studied at 35°C. With the increase in the mole fraction of Triton X-100 in the mixed surfactants, the water solubilization capacity increases and the monophasic area enlarges. The H2O-in-[Bmim]PF6 (W/IL) microemulsion was identified via electrical conductivity measurement. The existence of bulk water in the W/IL microemulsion was demonstrated based on the change of the O-D vibration frequency with content of D2O added and confirmed using UV-vis technique with CoCl2 as probe. Laccase can be solubilized in the W/IL microemulsion and exhibits a catalytic activity. The interface of the W/IL microemulsion has an inhibitory effect on the expression of the laccase activity, and the inhibitory effect is varied with the molar ratio of the mixed surfactants. PMID:25016546

  14. The photocatalytic degradation of cationic surfactant from wastewater in the presence of nano-zinc oxide using Taguchi method

    NASA Astrophysics Data System (ADS)

    Giahi, M.; Moradidoost, A.; Bagherinia, M. A.; Taghavi, H.

    2013-12-01

    The photocatalytic degradation of cetyl pyridinium chloride (CPC) has been investigated in aqueous phase using ultraviolet (UV) and ZnO nanopowder. Kinetic analysis showed that the extent of surfactant photocatalytic degradation can be fitted with pseudo-first-order model and photochemical elimination of CPC could be studied by Taguchi method. Our experimental design was based on testing five factors, i.e., dosage of K2S2O8, concentration of CPC, amount of ZnO, irradiation time and initial pH. Each factor was tested at four levels. The optimum parameters were found to be pH 5.0; amount of ZnO 11 mg; K2S2O8 3 mM; CPC 10 mg/L; irradiation time, 8 h.

  15. Self-organization at the interface and in aqueous solution of a cationic gemini surfactant from the dioctyl ester of cystine.

    PubMed

    Angayarkanny, S; Vijay, R; Baskar, Geetha; Mandal, A B

    2012-02-01

    The cationic surfactant, dioctyl ester of cystine hydrochloride (DOEC), was characterized for interfacial adsorption and aggregation behavior in water. The cmc of DOEC was measured as 1.42±0.27×10(-5) mol dm(-3) using the techniques of tensiometry, conductivity and fluorimetry. From specific conductivity measurements, the degree of dissociation (α) of the amine hydrochloride was measured as 0.612. The standard free energy change of micellization (ΔG(m)(°)) and adsorption (ΔG(a)(°)) were calculated to be -25.07 and -44.37 kJ mol(-1), respectively. The aggregated structures provide non-polar microdomains as inferred from the I(3)/I(1) emission intensity ratio of 1.05 of pyrene fluoroprobe and also a blue shift of fluorescence emission wave length (λ(emi.)) maximum down to 470 nm with enhanced intensity of ANS probe in micellar solutions. From Langmuir film balance experiments, it is shown that DOEC forms stable viscoelastic films at the interface with A(0) at 0.69 nm(2)molecule(-1) that agree with the result from surface tension measurements. Molecular modeling suggests the tilted orientation of DOEC at the interface. A large packing parameter (P) of 0.58 and the fibril structures as observed from microscopy studies demonstrate that DOEC favors one-dimensional growth to form elongated micelles.

  16. Characterization, kinetic, and isotherm data for Cr (VI) removal from aqueous solution by Populus alba biochar modified by a cationic surfactant.

    PubMed

    Shahverdi, Maryam; Kouhgardi, Esmaeil; Ramavandi, Bahman

    2016-12-01

    Populus alba is fast and auto- growing tree which profoundly accessible in around the world. The usage of the wastes of this tree would be admirable from environmental and solid waste management point of view. Thus, herein, this data set presents a facile method for providing an adsorbent from wastes of P. alba tree. The prepared adsorbent was modified by the cationic surfactant of (C16H33)N(CH3)3Br and applied to remove Cr (VI) from aqueous solution. The characterization data of the modified adsorbent were analyzed using FTIR and SEM methods. The information regarding kinetics, isotherms, and thermodynamics of chromium ions adsorption were listed. The data implied that the maximum adsorption capacity of adsorbent to uptake Cr (VI) from aqueous solution was obtained 52.63 mg/g. The acquired data indicated that the adsorption of Cr (VI) by the adsorbent prepared from P. alba is an promising technique for treating Cr-bearing wastewaters. PMID:27656668

  17. Effects of long-chain surfactants, short-chain alcohols and hydrolizable cations on the hydrophobic and hydration forces

    NASA Astrophysics Data System (ADS)

    Subramanian, Vivek

    Various experiments conducted in recent years showed that DLVO theory is applicable only to those particles whose advancing water contact angles (thetaa) are in the range of 15--60°. For example, direct surface force measurements conducted between silica substrates, whose theta a values are less than 15°, exhibited the existence of repulsive hydration forces at relatively short separation distances. On the other hand, substrates, for which thetaa is greater than 60°, exhibit long-range attractive hydrophobic forces not considered in the DLVO theory. It is the objective of the present study to measure the hydrophobic and hydration forces under different conditions. The measurements were conducted using both the Surface Forces Apparatus (SFA) and the Atomic Force Microscope (AFM). Mica and Silica were used as substrates, and the effects of dioctylammonium- hydrochloride (DOAHCl), octanol, methanol, ethanol, trifluoroethanol (TTE), pyridine, CaCl2, MgCl2 and sodium oleate were studied. A Mark IV SFA was used to conduct force measurements between mica surfaces in aqueous solutions of DOAHCl. At 7 x 10-6M DOAHCl, the mica surfaces were rendered electrically neutral, and net attractive hydrophobic forces were observed. The measured forces can be represented by a double-exponential function with the larger decay length (D2) of 5.1 nm. The measured hydrophobic forces are substantially stronger than those reported in literature between self-assembled monolayers of soluble single-chain surfactants. Force measurements were also conducted using the AFM between a silica plate and a glass sphere in aqueous solutions of methanol, ethanol, TFE and pyridine to study their effect on the hydration force. In Nanopure water, silica surfaces exhibit a strong shortrange hydration repulsion, which can be represented by a double-exponential function with its longer decay length (D2) of 2.4 nm. In solutions containing 15% methanol, however, the hydration force disappears completely

  18. Adsorption of a cationic dye, methylene blue, on to chitosan hydrogel beads generated by anionic surfactant gelation.

    PubMed

    Chatterjee, Sudipta; Chatterjee, Tania; Lim, Seong-Rin; Woo, Seung H

    2011-10-01

    Chitosan hydrogel beads (CSB) formed by sodium dodecyl sulphate (SDS) gelation were used for the removal of a cationic dye, methylene blue (MB), from aqueous solutions. The adsorption capacity of chitosan beads (CB) formed by alkali gelation was low because of charge repulsions between the chitosan (CS) and the MB. The adsorption capacity of CSB (4 g/L SDS gelation) for MB (100 mg/L) was 129.44 mg/g, and it decreased significantly with increasing SDS concentration during gelation. This decrease was a result of increased density of the CSB membrane materials. The CSB membrane materials formed with the 4 g/L SDS gelation showed the highest volumetric adsorption capacity. The MB adsorption on to CB and CSB increased with increasing values for the initial pH of solution. Data from both CB and CSB showed good fit to Sips isotherm models, and the maximum adsorption capacity of CSB (226.24 mg/g) was higher than that of CB (99.01 mg/g).

  19. Hexafluoroisopropanol-induced coacervation in aqueous mixed systems of cationic and anionic surfactants for the extraction of sulfonamides in water samples.

    PubMed

    Chen, Dan; Zhang, Pei; Li, Yunfang; Mei, Zhinan; Xiao, Yuxiu

    2014-09-01

    Hexafluoroisopropanol (HFIP)-induced coacervation in aqueous mixed systems of catanionic surfactants of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) was described in detail, and its application in the extraction of strongly polar sulfonamides (SAs) was investigated. With 10 % (v/v) HFIP inclusion, coacervation formation and two-phase separation occur in a wide range of SDS/DTAB mole ratios (88:12∼0:100 mol/mol) and total surfactant concentrations (10∼200 mmol/L). The interactions between HFIP and DTAB play an important role in coacervation formation. The HFIP-induced SDS-DTAB coacervation extraction proves to be an efficient method for the extraction and preconcentration of SAs. Both hydrophobic interaction and polar interactions (hydrogen-bond, electrostatic, and π-cation) contribute to the distribution of SAs into coacervate phase. The proposed HFIP-induced SDS-DTAB coacervation extraction combined with HPLC-UV was employed for the extraction and quantitative determination of SAs in environmental water samples. Limits of detection were 1.4∼2.5 ng mL(-1). Excellent linearity with correlation coefficients from 0.9990 to 0.9995 was obtained in the concentration of 0.01∼10 μg mL(-1). Relative recoveries were in the range of 93.4∼105.9 % for analysis of the lake, underground, and tap water samples spiked with SAs at 0.01, 1.0, and 10 μg/mL, respectively. Relative standard deviations were 0.7∼3.2 % for intraday precision and 1.3∼4.6 % for interday precision (n = 3). Concentration factors were 17∼49 for three water samples spiked with 0.01 μg/mL SAs. The results demonstrate that the proposed extraction method is feasible for the preconcentration and determination of trace SAs in real water samples.

  20. Hydrogen production by steam reforming of liquefied natural gas (LNG) over nickel catalysts supported on cationic surfactant-templated mesoporous aluminas

    NASA Astrophysics Data System (ADS)

    Seo, Jeong Gil; Youn, Min Hye; Park, Sunyoung; Jung, Ji Chul; Kim, Pil; Chung, Jin Suk; Song, In Kyu

    Two types of mesoporous γ-aluminas (denoted as A-A and A-S) are prepared by a hydrothermal method under different basic conditions using cationic surfactant (cetyltrimethylammonium bromide, CTAB) as a templating agent. A-A and A-S are synthesized in a medium of ammonia solution and sodium hydroxide solution, respectively. Ni/γ-Al 2O 3 catalysts (Ni/A-A and Ni/A-S) are then prepared by an impregnation method, and are applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of a mesoporous γ-Al 2O 3 support on the catalytic performance of Ni/γ-Al 2O 3 is investigated. The identity of basic solution strongly affects the physical properties of the A-A and A-S supports. The high surface-area of the mesoporous γ-aluminas and the strong metal-support interaction of supported catalysts greatly enhance the dispersion of nickel species on the catalyst surface. The well-developed mesopores of the Ni/A-A and Ni/A-S catalysts prohibit the polymerization of carbon species on the catalyst surface during the reaction. In the steam reforming of LNG, both Ni/A-A and Ni/A-S catalysts give better catalytic performance than the nickel catalyst supported on commercial γ-Al 2O 3 (Ni/A-C). In addition, the Ni/A-A catalyst is superior to the Ni/A-S catalyst. The relatively strong metal-support interaction of Ni/A-A catalyst effectively suppresses the sintering of metallic nickel and the carbon deposition in the steam reforming of LNG. The large pores of the Ni/A-A catalyst also play an important role in enhancing internal mass transfer during the reaction.

  1. Polymeric cationic substituted acrylamide surfactants

    SciTech Connect

    Nieh, E.C.Y.

    1983-11-15

    A new composition of matter comprises a copolymer of a surface active quaternary ammonium monomer salt and from 50 to 97% by wt of acrylamide. The new copolymers can have molecular weights substantially greater than 10,000 and still remain water soluble and surface active. Copolymers are prepared by polymerization techniques known in the art. The quaternary ammonium monomer is dispersed under inert atmosphere in aqueous solution which may additionally contain dissolved therein a low molecular weight alcohol such as ethanol, isopropanol, and the like. Acidic polymerization initiator such as the azo initiators, organic peroxides, or redox initiators such as the sulfite- persulfate system is then added in an amount calculated to yield a polymer product of desired molecular weight. (14 claims.

  2. Jammed acid-base reactions at interfaces.

    PubMed

    Gibbs-Davis, Julianne M; Kruk, Jennifer J; Konek, Christopher T; Scheidt, Karl A; Geiger, Franz M

    2008-11-19

    Using nonlinear optics, we show that acid-base chemistry at aqueous/solid interfaces tracks bulk pH changes at low salt concentrations. In the presence of 10 to 100 mM salt concentrations, however, the interfacial acid-base chemistry remains jammed for hours, until it finally occurs within minutes at a rate that follows the kinetic salt effect. For various alkali halide salts, the delay times increase with increasing anion polarizability and extent of cation hydration and lead to massive hysteresis in interfacial acid-base titrations. The resulting implications for pH cycling in these systems are that interfacial systems can spatially and temporally lag bulk acid-base chemistry when the Debye length approaches 1 nm.

  3. Acid-base equilibria involved in secondary reactions following the 4-carboxybenzophenone sensitized photooxidation of methionylglycine in aqueous solution. Spectral and time resolution of the decaying (S...N){sup +} radical cation

    SciTech Connect

    Hug, G.L.; Marciniak, B. |; Bobrowski, K. ||

    1996-09-05

    A radical cation with an intramolecular sulfur-nitrogen bond was formed in the photoinitiated transfer of an electron from the sulfur atom of the dipeptide Met-Gly to 4-carboxybenzophenone in its triplet state. The sulfur-nitrogen coupling involved two-center, three-electron bonds. The kinetics of the reactions of these radical cations, which were initiated by a laser flash, were followed over time. The principal method of implementing the spectral resolutions was accomplished through a multiple linear regression technique. This spectral analysis was repeated for numerous time windows during the lifetime of the transients` decays. The resulting concentrations of the transients were consistent with an independent factor analysis. It was found that the decay of the radical cations was multiexponential and that the decay varied with pH. A simplified reaction scheme was proposed whereby the absorbing radical cations can alternatively decay by an irreversible channel or react reversibly with OH{sup -}. Rate constants for the three elementary reactions of this scheme were determined from an analysis of the decay of the concentration of the radical cations. In addition, the equilibrium constant for the reversible reaction was determined by two separate procedures. 35 refs., 7 figs., 2 tabs.

  4. Cationic Porphyrin-Anionic Surfactant Mixtures for the Promotion of Self-Organized 1:4 Ion Pairs in Water with Strong Aggregation Properties.

    PubMed

    Pradines, Vincent; Bijani, Christian; Stigliani, Jean-Luc; Blanzat, Muriel; Rico-Lattes, Isabelle; Pratviel, Geneviève

    2015-12-21

    We performed a systematic study on the spectroscopic and aggregation properties of stoichiometric mixtures (1:4) of the tetracationic meso-tetrakis(4-N-methylpyridinium)porphyrin (H2 TMPyP) and three sodium alkylsulfate surfactants (tetradecyl, hexadecyl, and octadecylsulfate) in an aqueous solution. The objective was to build a supramolecular aggregate, which would favor the internalization of tetracationic porphyrins in cells without chemical modification of the structure of the porphyrin. We show that stoichiometric H2 TMPyP/alkylsulfate (1:4) mixtures lead to the formation of large hollow spherical aggregates (60-160 nm). The TEM images show that the membrane of these aggregates are composed of smaller aggregates, which are probably rod-like micelles. These rod-like micelles have a hydrophobic core composed of the alkyl chains of the alkylsulfate surfactant, whereas the charged surface corresponds to the tetracationic porphyrins.

  5. Self-Assembled Cationic Biodegradable Nanoparticles from pH-Responsive Amino-Acid-Based Poly(Ester Urea Urethane)s and Their Application As a Drug Delivery Vehicle.

    PubMed

    He, Mingyu; Potuck, Alicia; Kohn, Julie C; Fung, Katharina; Reinhart-King, Cynthia A; Chu, Chih-Chang

    2016-02-01

    The objective of this study is to develop a new family of biodegradable and biologically active copolymers and their subsequent self-assembled cationic nanoparticles as better delivery vehicles for anticancer drugs to achieve the synergism between the cytotoxicity effects of the loaded drugs and the macrophage inflammatory response of the delivery vehicle. This family of cationic nanoparticles was formulated from a new family of amphiphilic cationic Arginine-Leucine (Arg-Leu)-based poly(ester urea urethane) (Arg-Leu PEUU) synthesized from four building blocks (amino acids, diols, glycerol α-monoallyl ether, and 1,6 hexamethylene diisocyanate). The chemical, physical, and biological properties of Arg-Leu PEUU biomaterials can be tuned by controlling the feed ratio of the four building blocks. The Arg-Leu PEUU copolymers have weight-average molecular weights from 13.4 to 16.8 kDa and glass-transition temperatures from -3.4 to -4.6 °C. The self-assembled cationic nanoparticles (Arg-Leu PEUU NPs) were prepared using a facile dialysis method. Arg-Leu PEUU NPs have average diameters ranging from 187 to 272 nm, show good biocompatibility with 3T3 fibroblasts, and they support bovine aortic endothelial cell (BAEC) proliferation and adhesion. Arg-Leu PEUU NPs also enhanced the macrophages' production of tumor necrosis factor-α (TNF-α) and nitric oxide (NO), but produced relatively low levels of interleukin-10 (IL-10), and therefore, the antitumor activity of macrophages might be enhanced. Arg-Leu PEUU NPs were taken up by HeLa cells after 4 h of incubation. The in vitro hemolysis assay showed the cationic Arg-Leu PEUU NPs increased their chance of endosomal escape at a more acidic pH. Doxorubicin (DOX) was successfully incorporated into the Arg-Leu PEUU NPs, and the DOX-loaded Arg-Leu PEUU NPs exhibited a pH-dependent drug release profile with accelerated release kinetics in a mild acidic condition. The DOX-loaded 6-Arg-4-Leu-4 A/L-2/1 NPs showed higher HeLa cell

  6. [Sensitive Determination of Chondroitin Sulfate by Fluorescence Recovery of an Anionic Aluminum Phthalocyanine-Cationic Surfactant Ion-Association Complex Used as a Fluorescent Probe Emitting at Red Region].

    PubMed

    Chen, Lin; Huang, Ping; Yang, Hui-qing; Deng, Ya-bin; Guo, Meng-lin; Li, Dong-hui

    2015-08-01

    Determination of chondroitin sulfate in the biomedical field has an important value. The conventional methods for the assay of chondroitin sulfate are still unsatisfactory in sensitivity, selectivity or simplicity. This work aimed at developing a novel method for sensitive and selective determination of chondroitin sulfate by fluorimetry. We found that some kinds of cationic surfactants have the ability to quench the fluorescence of tetrasulfonated aluminum phthalocyanine (AlS4Pc), a strongly fluorescent compound which emits at red region, with high efficiency. But, the fluorescence of the above-mentioned fluorescence quenching system recovered significantly when chondroitin sulfate (CS) exits. Tetradecyl dimethyl benzyl ammonium chloride(TDBAC) which was screened from all of the candidates of cationic surfactants was chosen as the quencher because it shows the most efficient quenching effect. It was found that the fluorescence of AlS4Pc was extremely quenched by TDBAC because of the formation of association complex between AlS4Pc and TDBAC. Fluorescence of the association complex recovered dramatically after the addition of chondroitin sulfate (CS) due to the ability of chondroitin sulfate to shift the association equilibrium of the association, leading to the release of AlS4Pc, thus resulting in an increase in the fluorescence of the reaction system. Based on this phenomenon, a novel method with simplicity, accuracy and sensitivity was developed for quantitative determination of CS. Factors including the reaction time, influencing factors and the effect of coexisting substances were investigated and discussed. Under optimum conditions the linear range of the calibration curve was 0.20~10.0 μg · mL(-1). The detection limit for CS was 0.070 μg · mL(-1). The method has been applied to the analysis of practical samples with satisfied results. This work expands the applications of AlS4Pc in biomedical area. PMID:26672294

  7. [Sensitive Determination of Chondroitin Sulfate by Fluorescence Recovery of an Anionic Aluminum Phthalocyanine-Cationic Surfactant Ion-Association Complex Used as a Fluorescent Probe Emitting at Red Region].

    PubMed

    Chen, Lin; Huang, Ping; Yang, Hui-qing; Deng, Ya-bin; Guo, Meng-lin; Li, Dong-hui

    2015-08-01

    Determination of chondroitin sulfate in the biomedical field has an important value. The conventional methods for the assay of chondroitin sulfate are still unsatisfactory in sensitivity, selectivity or simplicity. This work aimed at developing a novel method for sensitive and selective determination of chondroitin sulfate by fluorimetry. We found that some kinds of cationic surfactants have the ability to quench the fluorescence of tetrasulfonated aluminum phthalocyanine (AlS4Pc), a strongly fluorescent compound which emits at red region, with high efficiency. But, the fluorescence of the above-mentioned fluorescence quenching system recovered significantly when chondroitin sulfate (CS) exits. Tetradecyl dimethyl benzyl ammonium chloride(TDBAC) which was screened from all of the candidates of cationic surfactants was chosen as the quencher because it shows the most efficient quenching effect. It was found that the fluorescence of AlS4Pc was extremely quenched by TDBAC because of the formation of association complex between AlS4Pc and TDBAC. Fluorescence of the association complex recovered dramatically after the addition of chondroitin sulfate (CS) due to the ability of chondroitin sulfate to shift the association equilibrium of the association, leading to the release of AlS4Pc, thus resulting in an increase in the fluorescence of the reaction system. Based on this phenomenon, a novel method with simplicity, accuracy and sensitivity was developed for quantitative determination of CS. Factors including the reaction time, influencing factors and the effect of coexisting substances were investigated and discussed. Under optimum conditions the linear range of the calibration curve was 0.20~10.0 μg · mL(-1). The detection limit for CS was 0.070 μg · mL(-1). The method has been applied to the analysis of practical samples with satisfied results. This work expands the applications of AlS4Pc in biomedical area.

  8. Understanding Acid Base Disorders.

    PubMed

    Gomez, Hernando; Kellum, John A

    2015-10-01

    The concentration of hydrogen ions is regulated in biologic solutions. There are currently 3 recognized approaches to assess changes in acid base status. First is the traditional Henderson-Hasselbalch approach, also called the physiologic approach, which uses the relationship between HCO3(-) and Pco2; the second is the standard base excess approach based on the Van Slyke equation. The third approach is the quantitative or Stewart approach, which uses the strong ion difference and the total weak acids. This article explores the origins of the current concepts framing the existing methods to analyze acid base balance.

  9. Clouding behaviour in surfactant systems.

    PubMed

    Mukherjee, Partha; Padhan, Susanta K; Dash, Sukalyan; Patel, Sabita; Mishra, Bijay K

    2011-02-17

    A study on the phenomenon of clouding and the applications of cloud point technology has been thoroughly discussed. The phase behaviour of clouding and various methods adopted for the determination of cloud point of various surfactant systems have been elucidated. The systems containing anionic, cationic, nonionic surfactants as well as microemulsions have been reviewed with respect to their clouding phenomena and the effects of structural variation in the surfactant systems have been incorporated. Additives of various natures control the clouding of surfactants. Electrolytes, nonelectrolytes, organic substances as well as ionic surfactants, when present in the surfactant solutions, play a major role in the clouding phenomena. The review includes the morphological study of clouds and their applications in the extraction of trace inorganic, organic materials as well as pesticides and protein substrates from different sources.

  10. Clouding behaviour in surfactant systems.

    PubMed

    Mukherjee, Partha; Padhan, Susanta K; Dash, Sukalyan; Patel, Sabita; Mishra, Bijay K

    2011-02-17

    A study on the phenomenon of clouding and the applications of cloud point technology has been thoroughly discussed. The phase behaviour of clouding and various methods adopted for the determination of cloud point of various surfactant systems have been elucidated. The systems containing anionic, cationic, nonionic surfactants as well as microemulsions have been reviewed with respect to their clouding phenomena and the effects of structural variation in the surfactant systems have been incorporated. Additives of various natures control the clouding of surfactants. Electrolytes, nonelectrolytes, organic substances as well as ionic surfactants, when present in the surfactant solutions, play a major role in the clouding phenomena. The review includes the morphological study of clouds and their applications in the extraction of trace inorganic, organic materials as well as pesticides and protein substrates from different sources. PMID:21296314

  11. Determination of aluminium with 8-hydroxyquinoline-5-sulfonic acid in presence of a cationic surfactant by first and second derivative synchronous fluorimetry

    SciTech Connect

    Salinas, F.; de la Pena, A.; Duran, M.S.

    1988-08-01

    An analytical method has been developed for the fluorimetric determination of nanogram amounts of aluminium in solution. The method is based on the reaction of aluminium with 8-hydroxyquinoline-5-sulfonic acid presence of hexadeciltrimethylammonium bromide as a surfactant agent. Synchronous scanned first and second derivative fluorimetry has been employed to increase the sensitivity of the method. The influence of reaction variables as well as instrumental parameters is discussed. The interference of various foreign ions has also been examined and in some cases eliminated or reduced by addition of 1,10-phenanthroline.

  12. Acid-Base Homeostasis.

    PubMed

    Hamm, L Lee; Nakhoul, Nazih; Hering-Smith, Kathleen S

    2015-12-01

    Acid-base homeostasis and pH regulation are critical for both normal physiology and cell metabolism and function. The importance of this regulation is evidenced by a variety of physiologic derangements that occur when plasma pH is either high or low. The kidneys have the predominant role in regulating the systemic bicarbonate concentration and hence, the metabolic component of acid-base balance. This function of the kidneys has two components: reabsorption of virtually all of the filtered HCO3(-) and production of new bicarbonate to replace that consumed by normal or pathologic acids. This production or generation of new HCO3(-) is done by net acid excretion. Under normal conditions, approximately one-third to one-half of net acid excretion by the kidneys is in the form of titratable acid. The other one-half to two-thirds is the excretion of ammonium. The capacity to excrete ammonium under conditions of acid loads is quantitatively much greater than the capacity to increase titratable acid. Multiple, often redundant pathways and processes exist to regulate these renal functions. Derangements in acid-base homeostasis, however, are common in clinical medicine and can often be related to the systems involved in acid-base transport in the kidneys.

  13. Interactions of phenol with cationic micelles of hexadecyltrimethylammonium bromide studied by titration calorimetry, conductimetry, and 1H NMR in the range of low additive and surfactant concentrations.

    PubMed

    Chaghi, Radhouane; de Ménorval, Louis-Charles; Charnay, Clarence; Derrien, Gaëlle; Zajac, Jerzy

    2008-10-01

    Interactions of phenol (PhOH) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions at surfactant concentrations close to the CMC and phenol contents of 1, 5, or 10 mmol kg(-1) have been investigated at 303 K by means of titration calorimetry, solution conductimetry, and (1)H NMR spectroscopy. Estimates of the main thermodynamic parameters related to HTAB micellization were made for PhOH/HTAB/H(2)O systems based on the specific conductivity measurements and calorimetric determination of the cumulative enthalpy of dilution as functions of the surfactant concentration at a fixed additive content. The combined analysis of the results obtained in H(2)O solutions pointed to the preferential location of PhOH in the outer micelle parts by an enthalpy-driven mechanism. Additional PhOH molecules were located increasingly deeper within the micelle core. The (1)H NMR study of PhOH solubilization by 1.5 mmol kg(-1) HTAB solutions in D(2)O indicated that the two categories of the solubilization site became saturated with the solubilizate already at the lowest additive content. Dissimilar amounts of the solubilized material in H(2)O and D(2)O solutions were ascribed to the difference in the initial micelle structures formed in the two solvents, as inferred from calorimetry and (1)H NMR studies of the HTAB micellization in D(2)O and H(2)O.

  14. Characterization of Rhinodrilus alatus hemoglobin (HbRa) and its subunits: evidence for strong interaction with cationic surfactants DTAB and CTAC.

    PubMed

    Carvalho, Francisco A O; Carvalho, José W P; Biazin, Ezer; Santiago, Patrícia S; Tabak, Marcel

    2014-01-01

    Rhinodrilus alatus is an annelid and its giant extracellular hemoglobin (HbRa) has a molecular mass (MM) of 3500kDa. In the current study, the characterization of MM values of the HbRa subunits, and the effects of surfactants and alkaline pH upon HbRa stability were monitored. Electrophoresis, MALDI-TOF-MS and AUC show that the MM values of HbRa subunits are very close, but not identical to the Glossoscolex paulistus hemoglobin (HbGp). The monomer d is found to exist in, at least, two isoforms: the main one, d1, displays a MM of 16,166±16Da, and the second one, d2, is less intense with MM of 16,490±20Da. For the trimer abc and tetramer abcd, single contributions around 51,470Da and 67,690Da were observed, respectively. Finally, the monomers a, b, and c, present MM values of 17,133, 17,290 and 15,506Da, respectively. Both CTAC and DTAB interact strongly with HbRa, and up to seven surfactant molecules are bound to the protein. On the other hand, spectroscopic studies show that HbRa is more stable at alkaline pH, as compared to HbGp. Thus, our data suggest that alkaline medium, up to pH10.0, induces the oligomeric dissociation, without promoting the subunits unfolding and heme iron oxidation. Our results suggest that the MM of the annelid hemoglobin subunits is conserved to a great extent in the evolution process of these species.

  15. Interaction of Surfactants with Block Polyelectrolyte Gels

    NASA Astrophysics Data System (ADS)

    Crichton, Mark; Bhatia, Surita

    2002-03-01

    We present SANS and rheology for poly(styrene)-poly(acrylic acid) polymers in aqueous solutions. These polymers self-assemble to form spherical micelles in aqueous solutions, and the micelles associate to create elastic, transparent gels at moderate polymer concentrations. The addition of cationic and anionic surfactants (DTAB and SDS) can be used to modify the associative interactions and solution rheology. Addition of an anionic surfactant acts to screen attractive interactions and causes a monotonic decrease in the elastic modulus. However, the addition of a cationic surfactant appears to initially induce a stronger intermicellar attraction, leading to gels with a higher elastic modulus. At higher surfactant concentrations, the cationic surfactant begins to screen intermicellar association, leading to a decrease in the strength of the gel.

  16. Preparation and characterization of zwitterionic surfactant-modified montmorillonites.

    PubMed

    Zhu, Jianxi; Qing, Yanhong; Wang, Tong; Zhu, Runliang; Wei, Jingming; Tao, Qi; Yuan, Peng; He, Hongping

    2011-08-15

    A series of zwitterionic surfactant-modified montmorillonites (ZSMMs) were synthesized using montmorillonite and three zwitterionic surfactants with different alkyl chain lengths at different concentrations [0.2-4.0 cation exchange capacity (CEC)]. These ZSMMs were characterized by X-ray diffraction (XRD), thermo-gravimetric analysis and differential thermo-gravimetric (TG/DTG) analyses. The zwitterionic surfactant could be intercalated into the interlayer spaces of montmorillonites and causing interlayer space-swelling. From XRD measurements, the amount of the surfactants loaded and the basal spacing increased with surfactant concentration and alkyl chain length. One endothermic DTG peak occurred at ~390 °C, which was assigned to the decomposition of the zwitterionic surfactant on the organo-montmorillonites from 0.2 to 0.6 CEC. When the surfactant loading was increased, a new endothermic peak appeared at ~340 °C. From the microstructures of these ZSMMs, the mechanism of zwitterionic surfactant adsorption was proposed. At relatively low loadings of the zwitterionic surfactant, most of surfactants enter the spacing by an ion-exchange mechanism and are adsorbed onto the interlayer cation sites. When the concentration of the zwitterionic surfactant exceeds the CEC of montmorillonite, the surfactant molecules then adhere to the surface-adsorbed surfactant. Some surfactants enter the interlayers, whereas the others are attached to the clay surface. When the concentration of surfactant increases further beyond 2.0 CEC, the surfactants may occupy the inter-particle space within the house-of-cards aggregate structure.

  17. New Lyotropic Liquid Crystals Based on Surfactants

    NASA Astrophysics Data System (ADS)

    Honciuc, Maria; Borlescu, C.; Popa, Carmen

    We presented here the phase diagrams and the influence of the external electric field on the lyotropic liquid crystal phase (LLC) for some binary and pseudoternary systems based on surfactants. Binary systems are of the type surfactant/water (S/W) and the pseudoternary systems are of the type surfactant/oil/water (S/O/W). Two surfactants have been used: the lauryl alcohol ethoxilated with 11 molecules of ethylene oxide (LA11EO), which is a nonionic compound, and a mixture of LA11EO with the cationic surfactant named alkyl C12-C14-dimethyl-benzyl ammonium chloride. Based on these two types of surfactants, pseudoternary systems were prepared. Pine oil has been used as the oil. The region where the LLC phase appears depends on the concentration of the surfactant and that of the pine oil, respectively. It is strongly influenced by the nature of the surfactant and by the presence of the pine oil for the same type of surfactant. The influence of the external electric field, investigated by measuring the electric current appearing in the samples for different concentrations of surfactant and pine oil was found to be more important in the case of the systems based on the nonionic-cationic mixture of surfactants. The results are discussed in terms of a theoretical model based on the local thermal equilibrium approach for systems running nonstatic processes.

  18. Lung surfactant.

    PubMed Central

    Rooney, S A

    1984-01-01

    Aspects of pulmonary surfactant are reviewed from a biochemical perspective. The major emphasis is on the lipid components of surfactant. Topics reviewed include surfactant composition, cellular and subcellular sites as well as pathways of biosynthesis of phosphatidylcholine, disaturated phosphatidylcholine and phosphatidylglycerol. The surfactant system in the developing fetus and neonate is considered in terms of phospholipid content and composition, rates of precursor incorporation, activities of individual enzymes of phospholipid synthesis and glycogen content and metabolism. The influence of the following hormones and other factors on lung maturation and surfactant production is discussed: glucocorticoids, thyroid hormone, estrogen, prolactin, cyclic AMP, beta-adrenergic and cholinergic agonists, prostaglandins and growth factors. The influence of maternal diabetes, fetal sex, stress and labor are also considered. Nonphysiologic and toxic agents which influence surfactant in the fetus, newborn and adult are reviewed. PMID:6145585

  19. Interactions of organic contaminants with mineral-adsorbed surfactants

    USGS Publications Warehouse

    Zhu, L.; Chen, B.; Tao, S.; Chiou, C.T.

    2003-01-01

    Sorption of organic contaminants (phenol, p-nitrophenol, and naphthalene) to natural solids (soils and bentonite) with and without myristylpyridinium bromide (MPB) cationic surfactant was studied to provide novel insight to interactions of contaminants with the mineral-adsorbed surfactant. Contaminant sorption coefficients with mineral-adsorbed surfactants, Kss, show a strong dependence on surfactant loading in the solid. At low surfactant levels, the Kss values increased with increasing sorbed surfactant mass, reached a maximum, and then decreased with increasing surfactant loading. The Kss values for contaminants were always higher than respective partition coefficients with surfactant micelles (Kmc) and natural organic matter (Koc). At examined MPB concentrations in water the three organic contaminants showed little solubility enhancement by MPB. At low sorbed-surfactant levels, the resulting mineral-adsorbed surfactant via the cation-exchange process appears to form a thin organic film, which effectively "adsorbs" the contaminants, resulting in very high Kss values. At high surfactant levels, the sorbed surfactant on minerals appears to form a bulklike medium that behaves essentially as a partition phase (rather than an adsorptive surface), with the resulting Kss being significantly decreased and less dependent on the MPB loading. The results provide a reference to the use of surfactants for remediation of contaminated soils/sediments or groundwater in engineered surfactant-enhanced washing.

  20. Interactions of organic contaminants with mineral-adsorbed surfactants.

    PubMed

    Zhu, Lizhong; Chen, Baoliang; Tao, Shu; Chiou, Cary T

    2003-09-01

    Sorption of organic contaminants (phenol, p-nitrophenol, and naphthalene) to natural solids (soils and bentonite) with and without myristylpyridinium bromide (MPB) cationic surfactant was studied to provide novel insightto interactions of contaminants with the mineral-adsorbed surfactant. Contaminant sorption coefficients with mineral-adsorbed surfactants, Kss, show a strong dependence on surfactant loading in the solid. At low surfactant levels, the Kss values increased with increasing sorbed surfactant mass, reached a maximum, and then decreased with increasing surfactant loading. The Kss values for contaminants were always higher than respective partition coefficients with surfactant micelles (Kmc) and natural organic matter (Koc). At examined MPB concentrations in water the three organic contaminants showed little solubility enhancement by MPB. At low sorbed-surfactant levels, the resulting mineral-adsorbed surfactant via the cation-exchange process appears to form a thin organic film, which effectively "adsorbs" the contaminants, resulting in very high Kss values. At high surfactant levels, the sorbed surfactant on minerals appears to form a bulklike medium that behaves essentially as a partition phase (rather than an adsorptive surface), with the resulting Kss being significantly decreased and less dependent on the MPB loading. The results provide a reference to the use of surfactants for remediation of contaminated soils/sediments or groundwater in engineered surfactant-enhanced washing.

  1. Surfactant-enhanced low-pH alkaline flooding

    SciTech Connect

    Peru, D.A. and Co., Columbia, MD . Research Div.); Lorenz, P.B. )

    1990-08-01

    This paper reports sodium bicarbonate investigated as a potential alkaline agent in surfactant-enhanced alkaline flooding because it has very little tendency to dissolve silicate minerals. In experiments performed with Wilmington, CA, crude oil and three types of surfactants, the bicarbonate/surfactant combination caused a marked lowering of interfacial tension (IFT). Bicarbonate protected the surfactant against divalent cations and reduced adsorption of surfactant and polymer on various minerals. Coreflood test confirm that sodium bicarbonate plus surfactant can be an effective alternative to the high-pH flooding process.

  2. Actinide cation-cation complexes

    SciTech Connect

    Stoyer, N.J.; Seaborg, G.T.

    1994-12-01

    The +5 oxidation state of U, Np, Pu, and Am is a linear dioxo cation (AnO{sub 2}{sup +}) with a formal charge of +1. These cations form complexes with a variety of other cations, including actinide cations. Other oxidation states of actinides do not form these cation-cation complexes with any cation other than AnO{sub 2}{sup +}; therefore, cation-cation complexes indicate something unique about AnO{sub 2}{sup +} cations compared to actinide cations in general. The first cation-cation complex, NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, was reported by Sullivan, Hindman, and Zielen in 1961. Of the four actinides that form AnO{sub 2}{sup +} species, the cation-cation complexes of NpO{sub 2}{sup +} have been studied most extensively while the other actinides have not. The only PuO{sub 2}{sup +} cation-cation complexes that have been studied are with Fe{sup 3+} and Cr{sup 3+} and neither one has had its equilibrium constant measured. Actinides have small molar absorptivities and cation-cation complexes have small equilibrium constants; therefore, to overcome these obstacles a sensitive technique is required. Spectroscopic techniques are used most often to study cation-cation complexes. Laser-Induced Photacoustic Spectroscopy equilibrium constants for the complexes NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, NpO{sub 2}{sup +}{center_dot}Th{sup 4+}, PuO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, and PuO{sub 2}{sup +}{center_dot}Th{sup 4+} at an ionic strength of 6 M using LIPAS are 2.4 {plus_minus} 0.2, 1.8 {plus_minus} 0.9, 2.2 {plus_minus} 1.5, and {approx}0.8 M{sup {minus}1}.

  3. Aqueous Foam Stabilized by Tricationic Amphiphilic Surfactants

    NASA Astrophysics Data System (ADS)

    Heerschap, Seth; Marafino, John; McKenna, Kristin; Caran, Kevin; Feitosa, Klebert; Kevin Caran's Research Group Collaboration

    2015-03-01

    The unique surface properties of amphiphilic molecules have made them widely used in applications where foaming, emulsifying or coating processes are needed. The development of novel architectures with multi-cephalic/tailed molecules have enhanced their anti-bacterial activity in connection with tail length and the nature of the head group. Here we report on the foamability of two triple head double, tail cationic surfactants (M-1,14,14, M-P, 14,14) and a triple head single tail cationic surfactant (M-1,1,14) and compare them with commercially available single headed, single tailed anionic and cationic surfactants (SDS,CTAB and DTAB). The results show that bubble rupture rate decrease with the length of the carbon chain irrespective of head structure. The growth rate of bubbles with short tailed surfactants (SDS) and longer, single tailed tricationic surfactants (M-1,1,14) was shown to be twice as high as those with longer tailed surfactants (CTAB, M-P,14,14, M-1,14,14). This fact was related to the size variation of bubbles, where the foams made with short tail surfactants exhibited higher polydispersivity than those with short tails. This suggests that foams with tricationic amphiphilics are closed linked to their tail length and generally insensitive to their head structure.

  4. Amino acid–based surfactants: New antimicrobial agents.

    PubMed

    Pinazo, A; Manresa, M A; Marques, A M; Bustelo, M; Espuny, M J; Pérez, L

    2016-02-01

    The rapid increase of drug resistant bacteria makes necessary the development of new antimicrobial agents. Synthetic amino acid-based surfactants constitute a promising alternative to conventional antimicrobial compounds given that they can be prepared from renewable raw materials. In this review, we discuss the structural features that promote antimicrobial activity of amino acid-based surfactants. Monocatenary, dicatenary and gemini surfactants that contain different amino acids on the polar head and show activity against bacteria are revised. The synthesis and basic physico-chemical properties have also been included.

  5. Bipolar Membranes for Acid Base Flow Batteries

    NASA Astrophysics Data System (ADS)

    Anthamatten, Mitchell; Roddecha, Supacharee; Jorne, Jacob; Coughlan, Anna

    2011-03-01

    Rechargeable batteries can provide grid-scale electricity storage to match power generation with consumption and promote renewable energy sources. Flow batteries offer modular and flexible design, low cost per kWh and high efficiencies. A novel flow battery concept will be presented based on acid-base neutralization where protons (H+) and hydroxyl (OH-) ions react electrochemically to produce water. The large free energy of this highly reversible reaction can be stored chemically, and, upon discharge, can be harvested as usable electricity. The acid-base flow battery concept avoids the use of a sluggish oxygen electrode and utilizes the highly reversible hydrogen electrode, thus eliminating the need for expensive noble metal catalysts. The proposed flow battery is a hybrid of a battery and a fuel cell---hydrogen gas storing chemical energy is produced at one electrode and is immediately consumed at the other electrode. The two electrodes are exposed to low and high pH solutions, and these solutions are separated by a hybrid membrane containing a hybrid cation and anion exchange membrane (CEM/AEM). Membrane design will be discussed, along with ion-transport data for synthesized membranes.

  6. Micellar acid-base potentiometric titrations of weak acidic and/or insoluble drugs.

    PubMed

    Gerakis, A M; Koupparis, M A; Efstathiou, C E

    1993-01-01

    The effect of various surfactants [the cationics cetyl trimethyl ammonium bromide (CTAB) and cetyl pyridinium chloride (CPC), the anionic sodium dodecyl sulphate (SDS), and the nonionic polysorbate 80 (Tween 80)] on the solubility and ionization constant of some sparingly soluble weak acids of pharmaceutical interest was studied. Benzoic acid (and its 3-methyl-, 3-nitro-, and 4-tert-butyl-derivatives), acetylsalicylic acid, naproxen and iopanoic acid were chosen as model examples. Precise and accurate acid-base titrations in micellar systems were made feasible using a microcomputer-controlled titrator. The response curve, response time and potential drift of the glass electrode in the micellar systems were examined. The cationics CTAB and CPC were found to increase considerably the ionization constant of the weak acids (delta pKa ranged from -0.21 to -3.57), while the anionic SDS showed negligible effect and the nonionic Tween 80 generally decreased the ionization constants. The solubility of the acids in aqueous micellar and acidified micellar solutions was studied spectrophotometrically and it was found increased in all cases. Acetylsalicylic acid, naproxen, benzoic acid and iopanoic acid could be easily determined in raw material and some of them in pharmaceutical preparations by direct titration in CTAB-micellar system instead of using the traditional non-aqueous or back titrimetry. Precisions of 0.3-4.3% RSD and good correlation with the official tedious methods were obtained. The interference study of some excipients showed that a preliminary test should be carried out before the assay of formulations.

  7. Structural study of surfactant-dependent interaction with protein

    SciTech Connect

    Mehan, Sumit; Aswal, Vinod K.; Kohlbrecher, Joachim

    2015-06-24

    Small-angle neutron scattering (SANS) has been used to study the complex structure of anionic BSA protein with three different (cationic DTAB, anionic SDS and non-ionic C12E10) surfactants. These systems form very different surfactant-dependent complexes. We show that the structure of protein-surfactant complex is initiated by the site-specific electrostatic interaction between the components, followed by the hydrophobic interaction at high surfactant concentrations. It is also found that hydrophobic interaction is preferred over the electrostatic interaction in deciding the resultant structure of protein-surfactant complexes.

  8. Structural study of surfactant-dependent interaction with protein

    NASA Astrophysics Data System (ADS)

    Mehan, Sumit; Aswal, Vinod K.; Kohlbrecher, Joachim

    2015-06-01

    Small-angle neutron scattering (SANS) has been used to study the complex structure of anionic BSA protein with three different (cationic DTAB, anionic SDS and non-ionic C12E10) surfactants. These systems form very different surfactant-dependent complexes. We show that the structure of protein-surfactant complex is initiated by the site-specific electrostatic interaction between the components, followed by the hydrophobic interaction at high surfactant concentrations. It is also found that hydrophobic interaction is preferred over the electrostatic interaction in deciding the resultant structure of protein-surfactant complexes.

  9. Probing nanoparticle effect in protein-surfactant complexes

    NASA Astrophysics Data System (ADS)

    Mehan, Sumit; Aswal, V. K.; Kohlbrecher, J.

    2015-06-01

    SANS experiments have been carried to probe the role of anionic silica nanoparticles in the anionic BSA protein-cationic DTAB surfactant complexes. In protein-surfactant complex, surfactant molecules aggregate to form micelle-like clusters along the unfolded polypeptide chains of the protein. The nanoparticle aggregation mediated by oppositely charged protein-surfactant complex coexists with the free protein-surfactant complexes in the nanoparticle-protein-surfactant system. There is rearrangement of micelles in adsorbed protein-surfactant complex on nanoparticles in leading to their (nanoparticle) aggregation. On the other hand, the unfolding of protein in free protein-surfactant complex is found to be significantly enhanced in presence of nanoparticles.

  10. Enhancement of enzymatic hydrolysis of cellulose by surfactant

    SciTech Connect

    Ooshima, H.; Sakata, M.; Harano, Y.

    1986-01-01

    Effects of surfactants on enzymatic saccharification of cellulose have been studied. Nonionic, amphoteric, and cationic surfactants enhanced the saccharification, while anionic surfactant did not. Cationic and anionic surfactants denatured cellulase in their relatively low concentrations, namely, more than 0.008 and 0.001%, respectively. Using nonionic surfactant Tween 20, which is most effective to the enhancement (e.g., the fractional conversion attained by 72 h saccharification of 5 wt % Avicel in the presence of 0.05 wt % Tween 20 is increased by 35%), actions of surfactant have been examined. As the results, it was suggested that Tween 20 plays an important role in the hydrolysis of crystalline cellulose and that Tween 20 disturbs the adsorption of endoglucanase on cellulose, i.e., varies the adsorption balance of endo- and exoglucanase, resulting in enhancing the reaction. The influence of Tween 20 to the saccharification was found to remain in simultaneous saccharification and fermentation of Avicel.

  11. Surfactant-enhanced cellulose nanocrystal Pickering emulsions.

    PubMed

    Hu, Zhen; Ballinger, Sarah; Pelton, Robert; Cranston, Emily D

    2015-02-01

    The effect of surfactants on the properties of Pickering emulsions stabilized by cellulose nanocrystals (CNCs) was investigated. Electrophoretic mobility, interfacial tension, confocal microscopy and three-phase contact angle measurements were used to elucidate the interactions between anionic CNCs and cationic alkyl ammonium surfactants didecyldimethylammonium bromide (DMAB) and cetyltrimethylammonium bromide (CTAB). Both surfactants were found to adsorb onto CNCs with concentration-dependent morphology. At low concentrations, individual surfactant molecules adsorbed with alkyl tails pointing outward leading to hydrophobic CNCs. At higher concentrations, above the surfactant's apparent critical micelle concentration, surfactant aggregate morphologies on CNCs were inferred and the hydrophobicity of CNCs decreased. DMAB, which has two alkyl tails, rendered the CNCs more hydrophobic than CTAB which has only a single alkyl tail, at all surfactant concentrations. The change in CNC wettability from surfactant adsorption was directly linked to emulsion properties; adding surfactant increased the emulsion stability, decreased the droplet size, and controlled the internal phase of CNC Pickering emulsions. More specifically, a double transitional phase inversion, from oil-in-water to water-in-oil and back to oil-in-water, was observed for emulsions with CNCs and increasing amounts of DMAB (the more hydrophobic surfactant). With CNCs and CTAB, no phase inversion was induced. This work represents the first report of CNC Pickering emulsions with surfactants as well as the first CNC Pickering emulsions that can be phase inverted. The ability to surface modify CNCs in situ and tailor emulsions by adding surfactants may extend the potential of CNCs to new liquid formulations and extruded/spray-dried materials.

  12. Radiometric acid-base titrations.

    PubMed

    Erdey, L; Gimesi, O; Szabadváry, F

    1969-03-01

    Acid-base titrations can be performed with radiometric end-point detection by use of labelled metal salts (e.g., ZnCl(2), HgCl(2)). Owing to the formation or dissolution of the corresponding hydroxide after the equivalence point, the activity of the titrated solution linearly increases or decreases as excess of standard solution is added. The end-point of the titration is determined graphically.

  13. Surfactant compositions

    SciTech Connect

    Novakovic, M.; Abend, P.G.

    1987-09-29

    A surfactant composition is described for subsequent addition to a soap slurring comprising an acyloxy alkane sulfonate salt. The sulfonate salt is present in an amount by weight of about 44 percent of about 56 percent. The polyol is present in an amount by weight of about 2 percent to about 6 percent, and water is present in an amount by weight of 26 to 36 percent. The composition constituting a solid reversible solution at ambient temperature and having a solids content of about 58 to 72 percent, whereby subsequent addition of the surfactant composition to a soap slurry results in formation of a soap/detergent bar having a smooth texture, uniform wear properties and a lack of grittiness.

  14. Removal of 226Ra and 228Ra from TENORM sludge waste using surfactants solutions.

    PubMed

    Attallah, M F; Hamed, Mostafa M; El Afifi, E M; Aly, H F

    2015-01-01

    The feasibility of using surfactants as extracting agent for the removal of radium species from TENORM sludge produced from petroleum industry is evaluated. In this investigation cationic and nonionic surfactants were used as extracting agents for the removal of radium radionuclides from the sludge waste. Two surfactants namely cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX100) were investigated as the extracting agents. Different parameters affecting the removal of both (226)Ra and (228)Ra by the two surfactants as well as their admixture were studied by the batch technique. These parameters include effect of shaking time, surfactants concentration and temperature as well as the effect of surfactants admixture. It was found that, higher solution temperature improves the removal efficiency of radium species. Combined extraction of nonionic and cationic surfactants produces synergistic effect in removal both (226)Ra and (228)Ra, where the removals reached 84% and 80% for (226)Ra and (228)Ra, respectively, were obtained using surfactants admixture.

  15. Removal of 226Ra and 228Ra from TENORM sludge waste using surfactants solutions.

    PubMed

    Attallah, M F; Hamed, Mostafa M; El Afifi, E M; Aly, H F

    2015-01-01

    The feasibility of using surfactants as extracting agent for the removal of radium species from TENORM sludge produced from petroleum industry is evaluated. In this investigation cationic and nonionic surfactants were used as extracting agents for the removal of radium radionuclides from the sludge waste. Two surfactants namely cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX100) were investigated as the extracting agents. Different parameters affecting the removal of both (226)Ra and (228)Ra by the two surfactants as well as their admixture were studied by the batch technique. These parameters include effect of shaking time, surfactants concentration and temperature as well as the effect of surfactants admixture. It was found that, higher solution temperature improves the removal efficiency of radium species. Combined extraction of nonionic and cationic surfactants produces synergistic effect in removal both (226)Ra and (228)Ra, where the removals reached 84% and 80% for (226)Ra and (228)Ra, respectively, were obtained using surfactants admixture. PMID:25464043

  16. Responsive Aqueous Foams Stabilized by Silica Nanoparticles Hydrophobized in Situ with a Conventional Surfactant.

    PubMed

    Zhu, Yue; Pei, Xiaomei; Jiang, Jianzhong; Cui, Zhenggang; Binks, Bernard P

    2015-12-01

    In the recent past, switchable surfactants and switchable/stimulus-responsive surface-active particles have been of great interest. Both can be transformed between surface-active and surface-inactive states via several triggers, making them recoverable and reusable afterward. However, the synthesis of these materials is complicated. In this paper we report a facile protocol to obtain responsive surface-active nanoparticles and their use in preparing responsive particle-stabilized foams. Hydrophilic silica nanoparticles are initially hydrophobized in situ with a trace amount of a conventional cationic surfactant in water, rendering them surface-active such that they stabilize aqueous foams. The latter can then be destabilized by adding equal moles of an anionic surfactant, and restabilized by adding another trace amount of the cationic surfactant followed by shaking. The stabilization-destabilization of the foams can be cycled many times at room temperature. The trigger is the stronger electrostatic interaction between the oppositely charged surfactants than that between the cationic surfactant and the negatively charged particles. The added anionic surfactant tends to form ion pairs with the cationic surfactant, leading to desorption of the latter from particle surfaces and dehydrophobization of the particles. Upon addition of another trace amount of cationic surfactant, the particles are rehydrophobized in situ and can then stabilize foams again. This principle makes it possible to obtain responsive surface-active particles using commercially available inorganic nanoparticles and conventional surfactants.

  17. Turbulent drag reduction in nonionic surfactant solutions

    NASA Astrophysics Data System (ADS)

    Tamano, Shinji; Itoh, Motoyuki; Kato, Katsuo; Yokota, Kazuhiko

    2010-05-01

    There are only a few studies on the drag-reducing effect of nonionic surfactant solutions which are nontoxic and biodegradable, while many investigations of cationic surfactant solutions have been performed so far. First, the drag-reducing effects of a nonionic surfactant (AROMOX), which mainly consisted of oleyldimethylamineoxide, was investigated by measuring the pressure drop in the pipe flow at solvent Reynolds numbers Re between 1000 and 60 000. Second, we investigated the drag-reducing effect of a nonionic surfactant on the turbulent boundary layer at momentum-thickness Reynolds numbers Reθ from 443 to 814 using two-component laser-Doppler velocimetry and particle image velocimetry systems. At the temperature of nonionic surfactant solutions, T =25 °C, the maximum drag reduction ratio for AROMOX 500 ppm was about 50%, in the boundary layer flow, although the drag reduction ratio was larger than 60% in pipe flow. Turbulence statistics and structures for AROMOX 500 ppm showed the behavior of typical drag-reducing flow such as suppression of turbulence and modification of near-wall vortices, but they were different from those of drag-reducing cationic surfactant solutions, in which bilayered structures of the fluctuating velocity vectors were observed in high activity.

  18. Influence of surfactant charge on antimicrobial efficacy of surfactant-stabilized thyme oil nanoemulsions.

    PubMed

    Ziani, Khalid; Chang, Yuhua; McLandsborough, Lynne; McClements, David Julian

    2011-06-01

    Thyme oil-in-water nanoemulsions stabilized by a nonionic surfactant (Tween 80, T80) were prepared as potential antimicrobial delivery systems (pH 4). The nanoemulsions were highly unstable to droplet growth and phase separation, which was attributed to Ostwald ripening due to the relatively high water solubility of thyme oil. Ostwald ripening could be inhibited by incorporating ≥75% of corn oil (a hydrophobic material with a low water solubility) into the nanoemulsion droplets. The electrical characteristics of the droplets in the nanoemulsions were varied by incorporating ionic surfactants with different charges after homogenization: a cationic surfactant (lauric arginate, LAE) or an anionic surfactant (sodium dodecyl sulfate, SDS). The antifungal activity of nanoemulsions containing positive, negative, or neutral thymol droplets was then conducted against four strains of acid-resistant spoilage yeasts: Zygosaccharomyces bailli, Saccharomyces cerevisiae, Brettanomyces bruxellensis, and Brettanomyces naardenensis. The antifungal properties of the three surfactants (T80, LAE, SDS) were also tested in the absence of thymol droplets. Both ionic surfactants showed strong antifungal activity in the absence of thymol droplets, but no antimicrobial activity in their presence. This effect was attributed to partitioning of the antimicrobial surfactant molecules between the oil droplet and microbial surfaces, thereby reducing the effective concentration of active surfactants available to act as antimicrobials. This study shows oil droplets may decrease the efficacy of surfactant-based antimicrobials, which has important consequences for formulating effective antimicrobial agents for utilization in emulsion-based food and beverage products. PMID:21520914

  19. The Influence of Surfactants on the Zeta Potential of Coals

    SciTech Connect

    Marsalek, R.

    2009-07-01

    The surface of three different kinds of coal was modified by three surfactants (cationic, anionic, and non-ionic). Changes on coal surface were examined by the zeta potential technique. The influence of the dispersion of pH, concentration of surfactants, and contact time were investigated. The most significant change in zeta potential resulting from adding surfactants was observed in activated coal (hydrophobic surface, largest BET surface area). Adding the cationic surfactant led to an increase of the zeta potential, contrary to measuring done in water. The anionic surfactant decreased the value of the zeta potential; however, this change was not too remarkable. The results proved that even a very low concentration of the cationic surfactant (0.01 mmol/L) causes a remarkable change of the zeta potential. On the other hand, a similar effect was observed until the concentration of the anionic surfactant reached about 10 mmol/L. The mechanism of binding surfactants is not simple, but preferential hydrophobic interactions were discovered.

  20. Interactions in Calcium Oxalate Hydrate/Surfactant Systems.

    PubMed

    Sikiric; Filipovic-Vincekovic; Babic-Ivancić Vdović Füredi-Milhofer

    1999-04-15

    Phase transformation of calcium oxalate dihydrate (COD) into the thermodynamically stable monohydrate (COM) in anionic (sodium dodecyl sulfate (SDS)) and cationic (dodecylammonium chloride) surfactant solutions has been studied. Both surfactants inhibit, but do not stop transformation from COD to COM due to their preferential adsorption at different crystal faces. SDS acts as a stronger transformation inhibitor. The general shape of adsorption isotherms of both surfactants at the solid/liquid interface is of two-plateau-type, but differences in the adsorption behavior exist. They originate from different ionic and molecular structures of crystal surfaces and interactions between surfactant headgroups and solid surface. Copyright 1999 Academic Press.

  1. Anionic/cationic complexes in hair care.

    PubMed

    O'Lenick, Tony

    2011-01-01

    The formulation of cosmetic products is always more complicated than studying the individual components in aqueous solution. This is because there are numerous interactions between the components, which make the formulation truly more than the sum of the parts. This article will look at interactions between anionic and cationic surfactants and offer insights into how to use these interactions advantageously in making formulations.

  2. DNA compaction by azobenzene-containing surfactant

    NASA Astrophysics Data System (ADS)

    Zakrevskyy, Yuriy; Kopyshev, Alexey; Lomadze, Nino; Morozova, Elena; Lysyakova, Ludmila; Kasyanenko, Nina; Santer, Svetlana

    2011-08-01

    We report on the interaction of cationic azobenzene-containing surfactant with DNA investigated by absorption and fluorescence spectroscopy, dynamic light scattering, and atomic force microscopy. The properties of the surfactant can be controlled with light by reversible switching of the azobenzene unit, incorporated into the surfactant tail, between a hydrophobic trans (visible irradiation) and a hydrophilic cis (UV irradiation) configuration. The influence of the trans-cis isomerization of the azobenzene on the compaction process of DNA molecules and the role of both isomers in the formation and colloidal stability of DNA-surfactant complexes is discussed. It is shown that the trans isomer plays a major role in the DNA compaction process. The influence of the cis isomer on the DNA coil configuration is rather small. The construction of a phase diagram of the DNA concentration versus surfactant/DNA charge ratio allows distancing between three major phases: colloidally stable and unstable compacted globules, and extended coil conformation. There is a critical concentration of DNA above which the compacted globules can be hindered from aggregation and precipitation by adding an appropriate amount of the surfactant in the trans configuration. This is because of the compensation of hydrophobicity of the globules with an increasing amount of the surfactant. Below the critical DNA concentration, the compacted globules are colloidally stable and can be reversibly transferred with light to an extended coil state.

  3. DNA compaction by azobenzene-containing surfactant

    SciTech Connect

    Zakrevskyy, Yuriy; Kopyshev, Alexey; Lomadze, Nino; Santer, Svetlana

    2011-08-15

    We report on the interaction of cationic azobenzene-containing surfactant with DNA investigated by absorption and fluorescence spectroscopy, dynamic light scattering, and atomic force microscopy. The properties of the surfactant can be controlled with light by reversible switching of the azobenzene unit, incorporated into the surfactant tail, between a hydrophobic trans (visible irradiation) and a hydrophilic cis (UV irradiation) configuration. The influence of the trans-cis isomerization of the azobenzene on the compaction process of DNA molecules and the role of both isomers in the formation and colloidal stability of DNA-surfactant complexes is discussed. It is shown that the trans isomer plays a major role in the DNA compaction process. The influence of the cis isomer on the DNA coil configuration is rather small. The construction of a phase diagram of the DNA concentration versus surfactant/DNA charge ratio allows distancing between three major phases: colloidally stable and unstable compacted globules, and extended coil conformation. There is a critical concentration of DNA above which the compacted globules can be hindered from aggregation and precipitation by adding an appropriate amount of the surfactant in the trans configuration. This is because of the compensation of hydrophobicity of the globules with an increasing amount of the surfactant. Below the critical DNA concentration, the compacted globules are colloidally stable and can be reversibly transferred with light to an extended coil state.

  4. Adsorption of dimeric surfactants in lamellar silicates

    NASA Astrophysics Data System (ADS)

    Balcerzak, Mateusz; Pietralik, Zuzanna; Domka, Ludwik; Skrzypczak, Andrzej; Kozak, Maciej

    2015-12-01

    The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay - hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1‧-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d001) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH2 and CH3 groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

  5. Structure and dynamics of polyelectrolyte surfactant mixtures under conditions of surfactant excess

    NASA Astrophysics Data System (ADS)

    Hoffmann, Ingo; Simon, Miriam; Farago, Bela; Schweins, Ralf; Falus, Peter; Holderer, Olaf; Gradzielski, Michael

    2016-09-01

    Oppositely charged polyelectrolyte (PE) surfactant mixtures can self-assemble into a large variety of mesoscopic structures, so-called polyelectrolyte surfactant complexes (PESCs). These structures directly affect the macroscopic behavior of such solutions. In this study, we investigated mixtures of the cationically charged PE JR 400 and the anionic surfactant SDS with the help of different neutron scattering and fluorescence methods. While an excess of PE charges in semi-dilute solutions causes an increase of viscosity, it has been observed that an excess of surfactant charges reduces the viscosity while precipitation is observed at charge equilibrium. The increase in viscosity had been investigated before and was attributed to the formation of cross links between PE chains. In this publication we focus our attention on the reduction of viscosity which is observed with an excess of surfactant charges. It is found that the PE chains form relatively large and densely packed clusters near the phase boundary on the surfactant rich side, thereby occupying less space and reducing the viscosity. For even higher surfactant concentrations, individual surfactant decorated PE chains are observed and their viscosity is found to be similar to that of the pure PE.

  6. Analysis of supercooling activities of surfactants.

    PubMed

    Kuwabara, Chikako; Terauchi, Ryuji; Tochigi, Hiroshi; Takaoka, Hisao; Arakawa, Keita; Fujikawa, Seizo

    2014-08-01

    Supercooling-promoting activities (SCAs) of 25 kinds of surfactants including non-ionic, anionic, cationic and amphoteric types were examined in solutions (buffered Milli-Q water, BMQW) containing the ice nucleation bacterium (INB) Erwinia ananas, silver iodide (AgI) or BMQW alone, which unintentionally contained unidentified ice nucleators, by a droplet freezing assay. Most of the surfactants exhibited SCA in solutions containing AgI but not in solutions containing the INB E. ananas or BMQW alone. SCAs of many surfactants in solutions containing AgI were very high compared with those of previously reported supercooling-promoting substances. Cationic surfactants, hexadecyltrimethylammonium bromide (C16TAB) and hexadecyltrimethylammonium chloride (C16TAC), at concentrations of 0.01% (w/v) exhibited SCA of 11.8 °C, which is the highest SCA so far reported. These surfactants also showed high SCAs at very low concentrations in solutions containing AgI. C16TAB exhibited SCA of 5.7 °C at a concentration of 0.0005% (w/v). PMID:24792543

  7. Analysis of supercooling activities of surfactants.

    PubMed

    Kuwabara, Chikako; Terauchi, Ryuji; Tochigi, Hiroshi; Takaoka, Hisao; Arakawa, Keita; Fujikawa, Seizo

    2014-08-01

    Supercooling-promoting activities (SCAs) of 25 kinds of surfactants including non-ionic, anionic, cationic and amphoteric types were examined in solutions (buffered Milli-Q water, BMQW) containing the ice nucleation bacterium (INB) Erwinia ananas, silver iodide (AgI) or BMQW alone, which unintentionally contained unidentified ice nucleators, by a droplet freezing assay. Most of the surfactants exhibited SCA in solutions containing AgI but not in solutions containing the INB E. ananas or BMQW alone. SCAs of many surfactants in solutions containing AgI were very high compared with those of previously reported supercooling-promoting substances. Cationic surfactants, hexadecyltrimethylammonium bromide (C16TAB) and hexadecyltrimethylammonium chloride (C16TAC), at concentrations of 0.01% (w/v) exhibited SCA of 11.8 °C, which is the highest SCA so far reported. These surfactants also showed high SCAs at very low concentrations in solutions containing AgI. C16TAB exhibited SCA of 5.7 °C at a concentration of 0.0005% (w/v).

  8. Tuning of nanoparticle-surfactant interactions in aqueous system

    NASA Astrophysics Data System (ADS)

    Kumar, Sugam; Aswal, V. K.

    2011-01-01

    The interaction of charged (anionic) silica nanoparticles with ionic and nonionic surfactants has been studied using small-angle neutron scattering (SANS). The surfactants used are anionic sodium dodecyl sulfate (SDS), cationic dodecyltrimethyl ammonium bromide (DTAB) and nonionic decaoxyethylene n-dodecylether (C12E10). The measurements are carried out at fixed concentration (1 wt%) of silica nanoparticles and with surfactant concentration varied in the range 0-2 wt%. It is found that there is no direct interaction between the nanoparticles and the surfactant (SDS) when they both are similarly charged. Both the silica nanoparticles and micelles coexist individually with no significant change in the structure of the micelles with respect to that in the pure surfactant solution. On the other hand, the presence of oppositely charged surfactant (DTAB) leads to the aggregation of silica nanoparticles even with very low surfactant concentration. The aggregation of silica nanoparticles is characterized by fractal structure and its fractal dimension remains constant with the increase in the surfactant concentration. In the case of nonionic surfactant, it interacts with the individual silica nanoparticles. The interaction is examined using two models: one that considers the surfactant layer coating on silica nanoparticles and a second one where the surface of the nanoparticles is decorated by the micelles. Contrast variation SANS measurements confirm the uniform decoration of nonionic micelles on the nanoparticles.

  9. Mechanisms of Particle Charging by Surfactants in Nonpolar Dispersions.

    PubMed

    Lee, Joohyung; Zhou, Zhang-Lin; Alas, Guillermo; Behrens, Sven Holger

    2015-11-10

    Electric charging of colloidal particles in nonpolar solvents plays a crucial role for many industrial applications and products, including rubbers, engine oils, toners, or electronic displays. Although disfavored by the low solvent permittivity, particle charging can be induced by added surfactants, even nonionic ones, but the underlying mechanism is poorly understood, and neither the magnitude nor the sign of charge can generally be predicted from the particle and surfactant properties. The conclusiveness of scientific studies has been limited partly by a traditional focus on few surfactant types with many differences in their chemical structure and often poorly defined composition. Here we investigate the surface charging of poly(methyl methacrylate) particles dispersed in hexane-based solutions of three purified polyisobutylene succinimide polyamine surfactants with "subtle" structural variations. We precisely vary the surfactant chemistry by replacing only a single electronegative atom located at a fixed position within the polar headgroup. Electrophoresis reveals that these small differences between the surfactants lead to qualitatively different particle charging. In the respective particle-free surfactant solutions we also find potentially telling differences in the size of the surfactant aggregates (inverse micelles), the residual water content, and the electric solution conductivity as well as indications for a significant size difference between oppositely charged inverse micelles of the most hygroscopic surfactant. An analysis that accounts for the acid/base properties of all constituents suggests that the observed particle charging is better described by asymmetric adsorption of charged inverse micelles from the liquid bulk than by charge creation at the particle surface. Intramicellar acid-base interaction and intermicellar surfactant exchange help rationalize the formation of micellar ions pairs with size asymmetry. PMID:26484617

  10. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2004-01-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Anionic surfactants (SS-6656, Alfoterra 35, 38, 63,65,68) have been identified which can change the wettability of the calcite surface to intermediate/water-wet condition as well or better than the cationic surfactant DTAB with a West Texas crude oil in the presence of Na{sub 2}CO{sub 3}. All the carbonate surfaces (Lithographic Limestone, Marble, Dolomite and Calcite) show similar behavior with respect to wettability alteration with surfactant 4-22. Anionic surfactants (5-166, Alfoterra-33 and Alfoterra-38 and Alfoterra-68), which lower the interfacial tension with a West Texas crude oil to very low values (<10{sup -2} nM/m), have also been identified. Plans for the next quarter include conducting wettability, mobilization, and imbibition studies.

  11. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2005-01-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Imbibition in an originally oil-wet 2D capillary is the fastest in the case of Alf-38 and slowest in the case of DTAB (among the surfactants studied). Force of adhesion studies and contact angle measurements show that greater wettability alteration is possible with these anionic surfactants than the cationic surfactant studied. The water imbibition rate does not increase monotonically with an increase in the surfactant concentration. A numerical model has been developed that fits the rate of imbibition. Plans for the next quarter include conducting simulation and imbibition studies.

  12. Effect of surfactant types and their concentration on the structural characteristics of nanoclay

    NASA Astrophysics Data System (ADS)

    Zawrah, M. F.; Khattab, R. M.; Saad, E. M.; Gado, R. A.

    2014-03-01

    A series of organo-modified nanoclays was synthesized using three different surfactants having different alkyl chain lengths and concentrations [0.5-5.0 cation exchange capacity (CEC)]. These surfactants were Ethanolamine (EA), Cetyltrimethylammoniumbromide (CTAB) and Tetraoctadecylammoniumbromide (TO). The obtained modified nanoclays were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) and compared with unmodified nanoclay. The results of XRD analysis indicated that the basal d-spacing has increased with increasing alkyl chain length and surfactant concentration. From the obtained microstructures of these organo-modified nanoclays, the mechanism of surfactant adsorption was proposed. At relatively low loading of surfactant, most of surfactant entered the spacing by an ion-exchange mechanism and is adsorbed onto the interlayer cation sites. When the concentration of the surfactant exceeds the CEC of clay, the surfactant molecules then adhere to the surface adsorbed surfactant. Some surfactants entered the interlayers, whereas the others were attached to the clay surface. When the concentration of surfactant increased further beyond 2.0 CEC, the surfactants might occupy the inter-particle space within the house-of-cards aggregate structure.

  13. Surfactant-stabilized small hydrogel particles in oil: hosts for remarkable activation of enzymes in organic solvents.

    PubMed

    Das, Dibyendu; Roy, Sangita; Debnath, Sisir; Das, Prasanta Kumar

    2010-04-26

    Hydrogels of amino acid based cationic surfactant having C(16) tails were used to immobilize heme proteins and enzyme. These hydrogel-entrapped proteins/enzyme showed remarkable activation when dispersed in organic solvent. The activation effect (ratio of the activity of the hydrogel-entrapped enzyme in organic solvent to the activity of the native enzyme in water) of cytochrome c increased up to 350-fold with varying protein and gelator concentration. Hydrogel-entrapped hemoglobin and horseradish peroxidase (HRP) also showed markedly improved activity in organic solvent. Alteration in the structure of the gelator and its supramolecular arrangement showed that the protein immobilized within amphiphilic networks with larger interstitial space exhibited higher activation. This striking activation of hydrogel-entrapped proteins stems from the following effects: 1) the hydrophilic domain of the amphiphilic networks facilitates accessibility of the enzyme to the water-soluble substrate. 2) the surfactant, as an integral part of the amphiphilic network, assists in the formation of a distinct interface through which reactants and products are easily transferred between hydrophilic and hydrophobic domains. 3) Surfactant gelators help in the dispersion and stabilization of gel matrix into small particles in organic solvent, which enhances the overall surface area and results in improved mass transfer. The activation was dramatically improved up to 675-fold in the presence of nongelating anionic surfactants that helped in disintegration of the gel into further smaller-sized particles. Interestingly, hydrogel-immobilized HRP exhibited about 2000-fold higher activity in comparison to the activity of the suspended enzyme in toluene. Structural changes of the entrapped enzyme and the morphology of the matrix were investigated to understand the mechanism of this activation.

  14. Thermally cleavable surfactants

    DOEpatents

    McElhanon, James R.; Simmons, Blake A.; Zifer, Thomas; Jamison, Gregory M.; Loy, Douglas A.; Rahimian, Kamyar; Long, Timothy M.; Wheeler, David R.; Staiger, Chad L.

    2009-11-24

    Two new surfactant molecules are reported which contain thermally labile Diels-Alder adducts connecting the polar and non-polar sections of each molecule. The two surfactants possess identical non-polar dodecyl tail segments but exhibit different polar headgroups. The surfactants become soluble in water when anionic salts are formed through the deprotonation of the surfactant headgroups by the addition of potassium hydroxide. When either surfactant is exposed to temperature above about 60.degree. C., the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments or the aqueous solutions of the surfactants subsequently exhibit loss of all surface-active behavior.

  15. Thermally cleavable surfactants

    DOEpatents

    McElhanon, James R.; Simmons, Blake A.; Zifer, Thomas; Jamison, Gregory M.; Loy, Douglas A.; Rahimian, Kamyar; Long, Timothy M.; Wheeler, David R.; Staiger, Chad L.

    2009-09-29

    Two new surfactant molecules are reported which contain thermally labile Diels-Alder adducts connecting the polar and non-polar sections of each molecule. The two surfactants possess identical non-polar dodecyl tail segments but exhibit different polar headgroups. The surfactants become soluble in water when anionic salts are formed through the deprotonation of the surfactant headgroups by the addition of potassium hydroxide. When either surfactant is exposed to temperature above about 60.degree. C., the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments or the aqueous solutions of the surfactants subsequently exhibit loss of all surface-active behavior.

  16. Thermally cleavable surfactants

    DOEpatents

    McElhanon, James R.; Simmons, Blake A.; Zifer, Thomas; Jamison, Gregory M.; Loy, Douglas A.; Rahimian, Kamyar; Long, Timothy M.; Wheeler, David R.; Staiger, Chad L.

    2006-04-04

    Two new surfactant molecules are reported which contain thermally labile Diels-Alder adducts connecting the polar and non-polar sections of each molecule. The two surfactants possess identical non-polar dodecyl tail segments but exhibit different polar headgroups. The surfactants become soluble in water when anionic salts are formed through the deprotonation of the surfactant headgroups by the addition of potassium hydroxide. When either surfactant is exposed to temperature above about 60.degree. C., the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments and the aqueous solutions of the surfactants subsequently exhibit loss of all surface-active behavior.

  17. Surfactant Modified/Mediated Thin-Layer Chromatographic Systems for the Analysis of Amino Acids

    PubMed Central

    Bhawani, Showkat A.; Albishri, Hassan M.; Mohamad Ibrahim, Mohamad N.; Mohammad, A.

    2013-01-01

    This review incorporates a large number of chromatographic systems modified by the surfactants. A large number of solvent systems and stationary phases are summarized in this paper. Three different kinds of surfactants (anionic, cationic, and nonionic) are used as modifiers for stationary phases as well as solvent systems. Surfactants are used at all the three different concentration levels (below, above, and at critical micelle concentration) where surfactants behave differently. Modifications of both stationary phases and solvent systems by surfactants produced a new generation of chromatographic systems. Microemulsion solvent systems are also incorporated in this paper. Microemulsion thin-layer chromatography is a new approach in the field of chromatography. PMID:24455427

  18. Next Generation Surfactants for Improved Chemical Flooding Technology

    SciTech Connect

    Laura Wesson; Prapas Lohateeraparp; Jeffrey Harwell; Bor-Jier Shiau

    2012-05-31

    The principle objective of this project was to characterize and test current and next generation high performance surfactants for improved chemical flooding technology, focused on reservoirs in the Pennsylvanian-aged (Penn) sands. In order to meet this objective the characteristic curvatures (Cc) of twenty-eight anionic surfactants selected for evaluation for use in chemical flooding formulations were determined. The Cc values ranged from -6.90 to 2.55 with the majority having negative values. Crude oil samples from nine Penn sand reservoirs were analyzed for several properties pertinent to surfactant formulation for EOR application. These properties included equivalent alkane carbon numbers, total acid numbers, and viscosity. The brine samples from these same reservoirs were analyzed for several cations and for total dissolved solids. Surfactant formulations were successfully developed for eight reservoirs by the end of the project period. These formulations were comprised of a tertiary mixture of anionic surfactants. The identities of these surfactants are considered proprietary, but suffice to say the surfactants in each mixture were comprised of varying chemical structures. In addition to the successful development of surfactant formulations for EOR, there were also two successful single-well field tests conducted. There are many aspects that must be considered in the development and implementation of effective surfactant formulations. Taking into account these other aspects, there were four additional studies conducted during this project. These studies focused on the effect of the stability of surfactant formulations in the presence of polymers with an associated examination of polymer rheology, the effect of the presence of iron complexes in the brine on surfactant stability, the potential use of sacrificial agents in order to minimize the loss of surfactant to adsorption, and the effect of electrolytes on surfactant adsorption. In these last four studies

  19. Conformational and phase transitions in DNA--photosensitive surfactant solutions: Experiment and modeling.

    PubMed

    Kasyanenko, N; Lysyakova, L; Ramazanov, R; Nesterenko, A; Yaroshevich, I; Titov, E; Alexeev, G; Lezov, A; Unksov, I

    2015-02-01

    DNA binding to trans- and cis-isomers of azobenzene containing cationic surfactant in 5 mM NaCl solution was investigated by the methods of dynamic light scattering (DLS), low-gradient viscometry (LGV), atomic force microscopy (AFM), circular dichroism (CD), gel electrophoresis (GE), flow birefringence (FB), UV-Vis spectrophotometry. Light-responsive conformational transitions of DNA in complex with photosensitive surfactant, changes in DNA optical anisotropy and persistent length, phase transition of DNA into nanoparticles induced by high surfactant concentration, as well as transformation of surfactant conformation under its binding to macromolecule were studied. Computer simulations of micelles formation for cis- and trans-isomers of azobenzene containing surfactant, as well as DNA-surfactant interaction, were carried out. Phase diagram for DNA-surfactant solutions was designed. The possibility to reverse the DNA packaging induced by surfactant binding with the dilution and light irradiation was shown.

  20. The Kidney and Acid-Base Regulation

    ERIC Educational Resources Information Center

    Koeppen, Bruce M.

    2009-01-01

    Since the topic of the role of the kidneys in the regulation of acid base balance was last reviewed from a teaching perspective (Koeppen BM. Renal regulation of acid-base balance. Adv Physiol Educ 20: 132-141, 1998), our understanding of the specific membrane transporters involved in H+, HCO , and NH transport, and especially how these…

  1. The Conjugate Acid-Base Chart.

    ERIC Educational Resources Information Center

    Treptow, Richard S.

    1986-01-01

    Discusses the difficulties that beginning chemistry students have in understanding acid-base chemistry. Describes the use of conjugate acid-base charts in helping students visualize the conjugate relationship. Addresses chart construction, metal ions, buffers and pH titrations, and the organic functional groups and nonaqueous solvents. (TW)

  2. Gemini ester quat surfactants and their biological activity.

    PubMed

    Łuczyński, Jacek; Frąckowiak, Renata; Włoch, Aleksandra; Kleszczyńska, Halina; Witek, Stanisław

    2013-03-01

    Cationic gemini surfactants are an important class of surface-active compounds that exhibit much higher surface activity than their monomeric counterparts. This type of compound architecture lends itself to the compound being easily adsorbed at interfaces and interacting with the cellular membranes of microorganisms. Conventional cationic surfactants have high chemical stability but poor chemical and biological degradability. One of the main approaches to the design of readily biodegradable and environmentally friendly surfactants involves inserting a bond with limited stability into the surfactant molecule to give a cleavable surfactant. The best-known example of such a compound is the family of ester quats, which are cationic surfactants with a labile ester bond inserted into the molecule. As part of this study, a series of gemini ester quat surfactants were synthesized and assayed for their biological activity. Their hemolytic activity and changes in the fluidity and packing order of the lipid polar heads were used as the measures of their biological activity. A clear correlation between the hemolytic activity of the tested compounds and their alkyl chain length was established. It was found that the compounds with a long hydrocarbon chain showed higher activity. Moreover, the compounds with greater spacing between their alkyl chains were more active. This proves that they incorporate more easily into the lipid bilayer of the erythrocyte membrane and affect its properties to a greater extent. A better understanding of the process of cell lysis by surfactants and of their biological activity may assist in developing surfactants with enhanced selectivity and in widening their range of application.

  3. Effects of concentration, temperature and solvent composition on density and apparent molar volume of the binary mixtures of cationic-anionic surfactants in methanol-water mixed solvent media.

    PubMed

    Bhattarai, Ajaya; Chatterjee, Sujeet Kumar; Niraula, Tulasi Prasad

    2013-01-01

    The accurate measurements on density of the binary mixtures of cetyltrimethylammonium bromide and sodium dodecyl sulphate in pure water and in methanol(1) + water (2) mixed solvent media containing (0.10, 0.20, and 0.30) volume fractions of methanol at 308.15, 318.15, and 323.15 K are reported. The concentrations are varied from (0.03 to 0.12) mol.l(-1) of sodium dodecyl sulphate in presence of ~ 5.0×10(-4) mol.l(-1) cetyltrimethylammonium bromide. The results showed almost increase in the densities with increasing surfactant mixture concentration, also the densities are found to decrease with increasing temperature over the entire concentration range, investigated in a given mixed solvent medium and these values are found to decrease with increasing methanol content in the solvent composition. The concentration dependence of the apparent molar volumes appear to be negligible over the entire concentration range, investigated in a given mixed solvent medium and the apparent molar volumes increase with increasing temperature and are found to decrease with increasing methanol content in the solvent composition.

  4. Controlling an electrostatic repulsion by oppositely charged surfactants towards positively charged fluorescent gold nanoclusters.

    PubMed

    Corpuz, Ryan D; Ishida, Yohei; Yonezawa, Tetsu

    2016-04-01

    A novel positively charged fluorescent gold nanocluster was successfully synthesized using the shortest cationic thiol, thiocholine. Effective control of electrostatic repulsion by the introduction of an anionic surfactant afforded a nanocluster that showed blue fluorescence emission.

  5. Aqueous foam surfactants for geothermal drilling fluids: 1. Screening

    SciTech Connect

    Rand, P.B.

    1980-01-01

    Aqueous foam is a promising drilling fluid for geothermal wells because it will minimize damage to the producing formation and would eliminate the erosion problems of air drilling. Successful use of aqueous foam will require a high foaming surfactant which will: (1) be chemically stable in the harsh thermal and chemical environment, and (2) form stable foams at high temperatures and pressures. The procedures developed to generate and test aqueous foams and the effects of a 260/sup 0/C temperature cycle on aqueous surfactant solutions are presented. More than fifty selected surfactants were evaluated with representatives from the amphoteric, anionic, cationic, and nonionic classes included. Most surfactants were severely degraded by this temperature cycle; however, some showed excellent retention of their properties. The most promising surfactant types were the alkyl and alkyl aryl sulfonates and the ethoxylated nonionics.

  6. The removal of anionic surfactants from water in coagulation process.

    PubMed

    Kaleta, Jadwiga; Elektorowicz, Maria

    2013-01-01

    This paper presents the results of a laboratory study on the effectiveness of the coagulation process in removing surfactants from water. The application of traditional coagulants (aluminium sulfate and iron chlorides) has not brought satisfactory results, the reduction in anionic surfactant (AS) content reached 7.6% and 10%, respectively. Adding cationic polyelectrolyte (Zetag-50) increased the removal efficiency to 24%. Coagulation using a polyelectrolyte alone proved to be more efficient, the reduction in surfactant content fluctuated at a level of about 50%. Complete surfactant removal was obtained when powdered activated carbon was added 5 minutes before the basic coagulant to the coagulation process. The efficiency of surfactant coagulation also increased after the application of powdered clinoptilolite, but to a smaller degree. Then the removal of AS was found to be improved by dosing powdered clinoptilolite simultaneously or with short delay after the addition of the basic coagulant. PMID:23837351

  7. Interaction between casein and the oppositely charged surfactant.

    PubMed

    Liu, Yan; Guo, Rong

    2007-09-01

    The interactions between the classical cationic surfactant dodecyltrimethylammonium bromide (DTAB) and 2.0 mg/mL casein were investigated using isothermal titration calorimetry (ITC), turbidity, dynamic light scattering (DLS), and fluorescence spectra measurements. The results suggest that the cationic headgroup of the surfactant individually binds to the negatively charged amino acid sites on the casein chains because of the electrostatic attraction upon the addition of DTAB. When the surfactant concentration reaches a critical value c1, DTAB forms micelle-like aggregates on the casein chain, resulting in the formation of insoluble casein/DTAB complexes. Further addition of DTAB leads to the redissolution of casein/DTAB complexes because of the net positive charge on casein/DTAB complexes and the formation of DTAB free micelles. The addition of salt screens the repulsion between the surfactant headgroups and the attraction between casein and surfactant molecules, which weakens the binding of surfactant onto the casein chain, favoring the formation of free surfactant micelles.

  8. Surfactants in atmospheric aerosols and rainwater around lake ecosystem.

    PubMed

    Razak, Intan Suraya; Latif, Mohd Talib; Jaafar, Shoffian Amin; Khan, Md Firoz; Mushrifah, Idris

    2015-04-01

    This study was conducted to determine the composition of surfactants in atmospheric aerosols and rainwater in the vicinity of Lake Chini, Malaysia. Samples of atmospheric aerosol and rainwater were collected between March and September 2011 using a high volume air sampler (HVAS) and glass bottles equipped with funnel. Colorimetric analysis was undertaken to determine the concentration of anionic surfactants as methylene blue active substances (MBAS) and cationic surfactants as disulphine blue active substances (DBAS). The water-soluble ionic compositions were determined using inductively coupled plasma mass spectrometry for cations (Na, K, Mg and Ca) and ion chromatography equipped with a conductivity detector for anions (F(-), Cl(-), NO3(-), and SO4(2-)) and the Nessler Method was used to obtain the NH4(+) concentrations. The source apportionment of MBAS and DBAS in atmospheric aerosols was identified using a combination of principal component analysis (PCA) and multiple linear regression (MLR). The results revealed that the concentrations of surfactants in atmospheric aerosols and rainwater were dominated by anionic surfactants as MBAS. The concentration of surfactants as MBAS and DBAS was dominated in fine mode compared to coarse mode aerosols. Using PCA/MLR analysis, two major sources of atmospheric surfactants to Lake Chini were identified as soil dust (75 to 93%) and biomass burning (2 to 22%).

  9. Switchable pickering emulsions stabilized by silica nanoparticles hydrophobized in situ with a switchable surfactant.

    PubMed

    Jiang, Jianzhong; Zhu, Yue; Cui, Zhenggang; Binks, Bernard P

    2013-11-18

    Back and forth: The CO2 /N2 trigger of a switchable surfactant (neutral amidine/cationic amidinium) was transferred to mineral nanoparticles through in situ hydrophobization in water. Switchable oil-in-water Pickering emulsions that entail a CO2 /N2 trigger were obtained by using negatively charged silica nanoparticles and a trace amount of the switchable surfactant as the stabilizer.

  10. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2004-10-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Simulation studies indicate that both wettability alteration and gravity-driven flow play significant role in oil recovery from fractured carbonates. Anionic surfactants (Alfoterra 35, 38) recover about 55% of the oil in about 150 days by imbibition driven by wettability alteration and low tension in the core-scale. Anionic surfactant, Alfoterra-68, recovers about 40% of the oil by lower tension aided gravity-driven imbibition in the core-scale. Cationic surfactant, DTAB recovers about 35% of the oil. Plans for the next quarter include conducting simulation and imbibition studies.

  11. Bending elasticity of charged surfactant layers: the effect of mixing.

    PubMed

    Bergström, L Magnus

    2006-08-01

    surfactants, and k(c) is further reduced in anionic/cationic surfactant mixtures where the surfactant in excess has the smaller tail volume. Likewise, the reduction of k(c) is enhanced in mixtures of an ionic and a nonionic surfactant where the ionic surfactant has the smaller tail. The effective bilayer bending constant (k(bi)) is also found to be reduced by mixing, and as a result, k(bi) is seen to go through a minimum at some intermediate composition. The reduction of k(bi) is expected to be most pronounced in mixtures of two oppositely charged surfactants where the surfactant in excess has the smaller tail in agreement with experimental observations.

  12. Surfactant effect on functionalized carbon nanotube coated snowman-like particles and their electro-responsive characteristics

    SciTech Connect

    Zhang, Ke; Liu, Ying Dan; Choi, Hyoung Jin

    2012-10-15

    The core–shell structured snowman-like (SL) microparticles coated by functionalized multi-walled carbon nanotube (MWNT) were prepared in the presence of different surfactants including cationic surfactant-cetyl trimethylammonium bromide (CTAB) and anionic surfactant-sodium lauryl sulfate (SDS). The effect of surfactants on adsorption onto SL particles was characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and conductivity. The cationic surfactant is found to be more effective than anionic surfactant for helping nanotube adsorbed onto microparticle due to the presence of electrostatic interaction between the functionalized MWNT and the surfactant. Furthermore, the MWNT/SL particles dispersed in silicone oil exhibited a typical fibril structure of the electrorheological characteristics under an applied electric field observed by an optical microscope (OM), in which the state of nanotubes wrapped on the particles strongly affects their electro-responsive characteristics.

  13. Influence of Structure, Charge, and Concentration on the Pectin-Calcium-Surfactant Complexes.

    PubMed

    Joshi, Nidhi; Rawat, Kamla; Bohidar, H B

    2016-05-12

    Polymer-surfactant complex formation of pectin with different types of surfactants, cationic (cetyltrimethylammonium bromide, CTAB and dodecyl trimethylammonium bromide, DTAB), anionic (sodium dodecyl sulfate, SDS), and neutral (Triton X-100, TX-100), was investigated at room temperature in the presence and absence of cross-linker calcium chloride using light scattering, zeta potential, rheology, and UV-vis spectroscopic measurements where the surfactant concentration was maintained below their critical micellar concentration (CMC). Results indicated that the interaction of cationic surfactant with pectin in the presence and absence of calcium chloride was much stronger compared to anionic and neutral surfactants. The neutral surfactant showed identifiable interaction despite the absence of any charged headgroup, while anionic surfactant showed feeble or very weak interaction with the polymer. The pectin-CTAB or DTAB complex formation was attributed to associative electrostatic and hydrophobic interactions. On comparison between the cationic surfactants, it was found that CTAB interacts strongly with pectin because of its long hydrocarbon chain. The morphology of complexes formed exhibited random coil structures while at higher concentration of surfactant, rod-like or extended random coil structures were noticed. Thus, functional characteristics of the complex could be tuned by varying the type of surfactant (charge and structure) and its concentration. The differential network rigidity (pectin-CTAB versus pectin-DTAB gels) obtained from rheology measurements showed that addition of a very small amount of surfactant (concentration ≪ CMC) was required for enhancing network strength, while the presence of a large amount of surfactant resulted in the formation of fragile gels. No gel formation occurred when the surfactant concentration was close to their CMC values. Considering the importance of pectin in food and pharmaceutical industry, this study is relevant.

  14. Use of an Acid-Base Table.

    ERIC Educational Resources Information Center

    Willis, Grover; And Others

    1986-01-01

    Identifies several ways in which an acid-base table can provide students with information about chemical reactions. Cites examples of the chart's use and includes a table which indicates the strengths of some common acids and bases. (ML)

  15. History of medical understanding and misunderstanding of Acid base balance.

    PubMed

    Aiken, Christopher Geoffrey Alexander

    2013-09-01

    To establish how controversies in understanding acid base balance arose, the literature on acid base balance was reviewed from 1909, when Henderson described how the neutral reaction of blood is determined by carbonic and organic acids being in equilibrium with an excess of mineral bases over mineral acids. From 1914 to 1930, Van Slyke and others established our acid base principles. They recognised that carbonic acid converts into bicarbonate all non-volatile mineral bases not bound by mineral acids and determined therefore that bicarbonate represents the alkaline reserve of the body and should be a physiological constant. They showed that standard bicarbonate is a good measure of acidosis caused by increased production or decreased elimination of organic acids. However, they recognised that bicarbonate improved low plasma bicarbonate but not high urine acid excretion in diabetic ketoacidosis, and that increasing pCO2 caused chloride to shift into cells raising plasma titratable alkali. Both indicate that minerals influence pH. In 1945 Darrow showed that hyperchloraemic metabolic acidosis in preterm infants fed milk with 5.7 mmol of chloride and 2.0 mmol of sodium per 100 kcal was caused by retention of chloride in excess of sodium. Similar findings were made but not recognised in later studies of metabolic acidosis in preterm infants. Shohl in 1921 and Kildeberg in 1978 presented the theory that carbonic and organic acids are neutralised by mineral base, where mineral base is the excess of mineral cations over anions and organic acid is the difference between mineral base, bicarbonate and protein anion. The degree of metabolic acidosis measured as base excess is determined by deviation in both mineral base and organic acid from normal.

  16. Interaction of photosensitive surfactant with DNA and poly acrylic acid

    SciTech Connect

    Zakrevskyy, Yuriy Paasche, Jens; Lomadze, Nino; Santer, Svetlana; Cywinski, Piotr; Cywinska, Magdalena; Reich, Oliver; Löhmannsröben, Hans-Gerd

    2014-01-28

    In this paper, we investigate interactions and phase transitions in polyelectrolyte-surfactant complexes formed between a cationic azobenzene-containing surfactant and two types of polyelectrolytes: natural (DNA) or synthetic (PAA: poly acrylic acid). The construction of a phase diagram allowed distancing between four major phases: extended coil conformation, colloidally stable compacted globules, colloidal instability range, and surfactant-stabilized compact state. Investigation on the complexes’ properties in different phases and under irradiation with UV light provides information about the role of the surfactant's hydrophobic trans isomers both in the formation and destruction of DNA and PAA globules as well as in their colloidal stabilization. The trans isomer shows much stronger affinity to the polyelectrolytes than the hydrophilic cis counterpart. There is no need for complete compensation of the polyelectrolyte charges to reach the complete compaction. On contrary to the findings previously reported in the literature, we demonstrate – for the first time – complete polyelectrolyte compaction which occurs already at 20% of DNA (and at 50% of PAA) charge compensation. The trans isomer plays the main role in the compaction. The aggregation between azobenzene units in the photosensitive surfactant is a driving force of this process. The decompaction can be realized during UV light irradiation and is strongly influenced by the interplay between surfactant-surfactant and surfactant-DNA interactions in the compacted globules.

  17. Interaction of photosensitive surfactant with DNA and poly acrylic acid.

    PubMed

    Zakrevskyy, Yuriy; Cywinski, Piotr; Cywinska, Magdalena; Paasche, Jens; Lomadze, Nino; Reich, Oliver; Löhmannsröben, Hans-Gerd; Santer, Svetlana

    2014-01-28

    In this paper, we investigate interactions and phase transitions in polyelectrolyte-surfactant complexes formed between a cationic azobenzene-containing surfactant and two types of polyelectrolytes: natural (DNA) or synthetic (PAA: poly acrylic acid). The construction of a phase diagram allowed distancing between four major phases: extended coil conformation, colloidally stable compacted globules, colloidal instability range, and surfactant-stabilized compact state. Investigation on the complexes' properties in different phases and under irradiation with UV light provides information about the role of the surfactant's hydrophobic trans isomers both in the formation and destruction of DNA and PAA globules as well as in their colloidal stabilization. The trans isomer shows much stronger affinity to the polyelectrolytes than the hydrophilic cis counterpart. There is no need for complete compensation of the polyelectrolyte charges to reach the complete compaction. On contrary to the findings previously reported in the literature, we demonstrate - for the first time - complete polyelectrolyte compaction which occurs already at 20% of DNA (and at 50% of PAA) charge compensation. The trans isomer plays the main role in the compaction. The aggregation between azobenzene units in the photosensitive surfactant is a driving force of this process. The decompaction can be realized during UV light irradiation and is strongly influenced by the interplay between surfactant-surfactant and surfactant-DNA interactions in the compacted globules. PMID:25669583

  18. A novel biosensor method for surfactant determination based on acetylcholinesterase inhibition

    NASA Astrophysics Data System (ADS)

    Kucherenko, I. S.; Soldatkin, O. O.; Arkhypova, V. M.; Dzyadevych, S. V.; Soldatkin, A. P.

    2012-06-01

    A novel enzyme biosensor based on acetylcholinesterase inhibition for the determination of surfactants in aqueous solutions is described. Acetylcholinesterase-based bioselective element was deposited via glutaraldehyde on the surface of conductometric transducers. Different variants of inhibitory analysis of surfactants were tested, and finally surfactant's concentration was evaluated by measuring initial rate of acetylcholinesterase inhibition. Besides, we studied the effect of solution characteristics on working parameters of the biosensor for direct measurement of acetylcholine and for inhibitory determination of surfactants. The biosensor's sensitivity to anionic and cationic surfactants (0.35 mg l-1) was tested. The high operational stability of the biosensor during determination of acetylcholine (RSD 2%) and surfactants (RSD 11%) was shown. Finally, we discussed the selectivity of the biosensor toward surfactants and other AChE inhibitors. The proposed biosensor can be used as a component of the multibiosensor for ecological monitoring of toxicants.

  19. [Acute toxicity of different type pesticide surfactants to Daphnia magna].

    PubMed

    Li, Xiu-huan; Li, Hua; Chen, Cheng-yu; Li, Jian-tao; Liu, Feng

    2013-08-01

    By using the standard test methods in Experimental Guideline for Environmental Safety Evaluation of Chemical Pesticide to aquatic organisms, a comparative study was conducted on the acute toxicity of 39 nonionic, 6 anionic, and 3 cationic surfactants to Daphnia magna. The acute toxicity of three cationic surfactants 1427, 1227 and C8-10 to D. magna belonged to virulent level, and the toxicity of 1427 was the highest, with the EC50 value being 0.97 x 10(-2) mg x L(-1). The acute toxicity of nonionic surfactants polyoxyethylene ether castor oil EL, Tween, and Span emulsifiers belonged to low level, but the toxicity of alkylphenol polyoxyethylene ether and fatty alcohol polyoxyethylene ether surfactants was relatively high, of which, AEO-7 and AEO-5 displayed high toxicity, with the EC50 value being 0.82 and 0.97 mg x L(-1), respectively. In these surfactants, the more liposolubility, the higher the toxicity was. Most of the anionic surfactants were medium in toxicity, but the acute toxicity of NNO belonged to high toxicity, with the EC50 value being 0.17 mg x L(-1).

  20. Absorption, fluorescence, and acid-base equilibria of rhodamines in micellar media of sodium dodecyl sulfate.

    PubMed

    Obukhova, Elena N; Mchedlov-Petrossyan, Nikolay O; Vodolazkaya, Natalya A; Patsenker, Leonid D; Doroshenko, Andrey O; Marynin, Andriy I; Krasovitskii, Boris M

    2017-01-01

    Rhodamine dyes are widely used as molecular probes in different fields of science. The aim of this paper was to ascertain to what extent the structural peculiarities of the compounds influence their absorption, emission, and acid-base properties under unified conditions. The acid-base dissociation (HR(+)⇄R+H(+)) of a series of rhodamine dyes was studied in sodium n-dodecylsulfate micellar solutions. In this media, the form R exists as a zwitterion R(±). The indices of apparent ionization constants of fifteen rhodamine cations HR(+) with different substituents in the xanthene moiety vary within the range of pKa(app)=5.04 to 5.53. The distinct dependence of emission of rhodamines bound to micelles on pH of bulk water opens the possibility of using them as fluorescent interfacial acid-base indicators.

  1. Absorption, fluorescence, and acid-base equilibria of rhodamines in micellar media of sodium dodecyl sulfate.

    PubMed

    Obukhova, Elena N; Mchedlov-Petrossyan, Nikolay O; Vodolazkaya, Natalya A; Patsenker, Leonid D; Doroshenko, Andrey O; Marynin, Andriy I; Krasovitskii, Boris M

    2017-01-01

    Rhodamine dyes are widely used as molecular probes in different fields of science. The aim of this paper was to ascertain to what extent the structural peculiarities of the compounds influence their absorption, emission, and acid-base properties under unified conditions. The acid-base dissociation (HR(+)⇄R+H(+)) of a series of rhodamine dyes was studied in sodium n-dodecylsulfate micellar solutions. In this media, the form R exists as a zwitterion R(±). The indices of apparent ionization constants of fifteen rhodamine cations HR(+) with different substituents in the xanthene moiety vary within the range of pKa(app)=5.04 to 5.53. The distinct dependence of emission of rhodamines bound to micelles on pH of bulk water opens the possibility of using them as fluorescent interfacial acid-base indicators. PMID:27423469

  2. Acid-base properties of sorbents based on modified zirconium(IV) phosphates

    SciTech Connect

    Bekrenev, A.V.; Pyartman, A.K.

    1995-11-01

    Modifying and doping syntheses are widely used to improve the reproducibility of ion-exchange properties and to increase the capacity of inorganic ion exchangers. Numerous examples of doping zirconium phosphate ion exchangers with cationic or anionic additives are known. The aim of this work was to investigate the acid-base properties of zirconium phosphates modified with anionic additives (phthalate and sulfosalicylate ions) in comparison with unmodified samples.

  3. [Kidney, Fluid, and Acid-Base Balance].

    PubMed

    Shioji, Naohiro; Hayashi, Masao; Morimatsu, Hiroshi

    2016-05-01

    Kidneys play an important role to maintain human homeostasis. They contribute to maintain body fluid, electrolytes, and acid-base balance. Especially in fluid control, we, physicians can intervene body fluid balance using fluid resuscitation and diuretics. In recent years, one type of fluid resuscitation, hydroxyl ethyl starch has been extensively studied in the field of intensive care. Although their effects on fluid resuscitation are reasonable, serious complications such as kidney injury requiring renal replacement therapy occur frequently. Now we have to pay more attention to this important complication. Another topic of fluid management is tolvaptan, a selective vasopressin-2 receptor antagonist Recent randomized trial suggested that tolvaptan has a similar supportive effect for fluid control and more cost effective compared to carperitide. In recent years, Stewart approach is recognized as one important tool to assess acid-base balance in critically ill patients. This approach has great value, especially to understand metabolic components in acid-base balance. Even for assessing the effects of kidneys on acid-base balance, this approach gives us interesting insight. We should appropriately use this new approach to treat acid-base abnormality in critically ill patients. PMID:27319095

  4. Perfluorinated Alcohols Induce Complex Coacervation in Mixed Surfactants.

    PubMed

    Jenkins, Samuel I; Collins, Christopher M; Khaledi, Morteza G

    2016-03-15

    Recently, we reported a unique and nearly ubiquitous phenomenon of inducing simple and complex coacervation in solutions of a broad variety of individual and mixed amphiphiles and over a wide range of concentrations and mole fractions. This paper describes a novel type of biphasic separation in aqueous solutions of mixed cationic-anionic (catanionic) surfactants induced by hexafluoroisopropanol (HFIP). The test cases included mixtures of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) (surfactants with different carbon chain lengths) as well as dodecyltrimethylammonium bromide (DTAB) with SDS (surfactants with the same carbon chain lengths). The CTAB-SDS-HFIP coacervate systems can be produced at many different mole ratios of surfactant, but DTAB-SDS-HFIP formed only coacervates at equimolar (1:1) mole ratios of DTAB and SDS. The phase-transition behavior of both systems was studied over a wide range of surfactant and HFIP concentrations at the stoichiometric (1:1) mole ratio of cationic/anionic surfactants. The chemical compositions of each of the two phases (aqueous-rich and coacervate phases) were studied with regard to the concentrations of HFIP, water, and individual surfactants. It is revealed that the surfactant-rich phase (coacervate phase) contains a large percentage of fluoroalcohol relative to the aqueous phase and is enriched in both surfactants but contains a small percentage of water. Surprisingly, the concentration of water in the coacervate phase increases as the total HFIP concentration is increased while the concentration of HFIP in the coacervate phase remains relatively constant, which means a larger amount of water associated with HFIP molecules is extracted into the coacervate phase, which results in the growth of the phase. The volume of the coacervate phase increases with an increase in surfactant concentration and total HFIP %. The coacervate phase is highly enriched in the two amphiphilic ions (DTA(+) and DS

  5. Biomimetic Approach for Ion Channels Based on Surfactant Encapsulated Spherical Porous Metal-Oxide Capsules.

    PubMed

    Mahon, Eugene; Garai, Somenath; Müller, Achim; Barboiu, Mihail

    2015-09-16

    Distinguished hybrid clusters with hydrophilic and hydrophobic interiors embedded within cationic surfactant shells are spontaneously inserted into lipid bilayers, showing well-defined ionic conductance behaviors. The transport via the narrow pore gates acting as selectivity filters is controlled by the dehydration energy of the cations.

  6. Dendrimer-surfactant interactions.

    PubMed

    Cheng, Yiyun; Zhao, Libo; Li, Tianfu

    2014-04-28

    In this article, we reviewed the interactions between dendrimers and surfactants with particular focus on the interaction mechanisms and physicochemical properties of the yielding dendrimer-surfactant aggregates. In order to provide insight into the behavior of dendrimers in biological systems, the interactions of dendrimers with bio-surfactants such as phospholipids in bulk solutions, in solid-supported bilayers and at the interface of phases or solid-states were discussed. Applications of the dendrimer-surfactant aggregates as templates to guide the synthesis of nanoparticles and in drug or gene delivery were also mentioned.

  7. Surfactant phospholipid metabolism

    PubMed Central

    Agassandian, Marianna; Mallampalli, Rama K.

    2012-01-01

    Pulmonary surfactant is essential for life and is comprised of a complex lipoprotein-like mixture that lines the inner surface of the lung to prevent alveolar collapse at the end of expiration. The molecular composition of surfactant depends on highly integrated and regulated processes involving its biosynthesis, remodeling, degradation, and intracellular trafficking. Despite its multicomponent composition, the study of surfactant phospholipid metabolism has focused on two predominant components, disaturated phosphatidylcholine that confers surface-tension lowering activities, and phosphatidylglycerol, recently implicated in innate immune defense. Future studies providing a better understanding of the molecular control and physiological relevance of minor surfactant lipid components are needed. PMID:23026158

  8. Genetics Home Reference: surfactant dysfunction

    MedlinePlus

    ... Me Understand Genetics Home Health Conditions surfactant dysfunction surfactant dysfunction Enable Javascript to view the expand/collapse boxes. Download PDF Open All Close All Description Surfactant dysfunction is a lung disorder that causes breathing ...

  9. Surfactant media for constant-current coulometry. Application for the determination of antioxidants in pharmaceuticals.

    PubMed

    Ziyatdinova, Guzel; Ziganshina, Endzhe; Budnikov, Herman

    2012-09-26

    Effect of surfactant presence on electrochemical generation of titrants has been evaluated and discussed for the first time. Cationic (1-dodecylpyridinium and cetylpyridinium bromide), anionic (sodium dodecyl sulfate) and nonionic (Triton X100 and Brij(®) 35) surfactants as well as nonionic high molecular weight polymer (PEG 4000) do not react with the electrogenerated bromine, iodine and hexacyanoferrate(III) ions. The electrogenerated chlorine chemically interact with Triton X100 and Brij(®) 35. The allowable range of surfactants concentrations providing 100% current yield has been found. Chain-breaking low molecular weight antioxidants (ascorbic acid, rutin, α-tocopherol and retinol) were determined by reaction with the electrogenerated titrants in surfactant media. Nonionic and cationic surfactants can be used for the determination of antioxidants by reaction with the electrogenerated halogens. On contrary, cationic surfactants gives significantly overstated results of antioxidants determination with electrogenerated hexacyanoferrate(III) ions. The use of surfactants in coulometry of α-tocopherol and retinol provides their solubilization and allows to perform titration in water media. Simple, express and reliable coulometric approach for determination of α-tocopherol, rutin and ascorbic acid in pharmaceuticals using surfactant media has been developed. The relative standard deviation of the measurements does not exceed of 5%.

  10. Dilute Surfactant Methods for Carbonate Formations

    SciTech Connect

    Kishore K. Mohanty

    2006-02-01

    There are many fractured carbonate reservoirs in US (and the world) with light oil. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). The process of using dilute anionic surfactants in alkaline solutions has been investigated in this work for oil recovery from fractured oil-wet carbonate reservoirs both experimentally and numerically. This process is a surfactant-aided gravity drainage where surfactant diffuses into the matrix, lowers IFT and contact angle, which decrease capillary pressure and increase oil relative permeability enabling gravity to drain the oil up. Anionic surfactants have been identified which at dilute concentration of 0.05 wt% and optimal salinity can lower the interfacial tension and change the wettability of the calcite surface to intermediate/water-wet condition as well or better than the cationic surfactant DTAB with a West Texas crude oil. The force of adhesion in AFM of oil-wet regions changes after anionic surfactant treatment to values similar to those of water-wet regions. The AFM topography images showed that the oil-wetting material was removed from the surface by the anionic surfactant treatment. Adsorption studies indicate that the extent of adsorption for anionic surfactants on calcite minerals decreases with increase in pH and with decrease in salinity. Surfactant adsorption can be minimized in the presence of Na{sub 2}CO{sub 3}. Laboratory-scale surfactant brine imbibition experiments give high oil recovery (20-42% OOIP in 50 days; up to 60% in 200 days) for initially oil-wet cores through wettability alteration and IFT reduction. Small (<10%) initial gas saturation does not affect significantly the rate of oil recovery in the imbibition process, but larger gas saturation decreases the oil recovery rate. As the core permeability decreases, the rate of oil recovery reduces

  11. Surfactant titration of nanoparticle-protein corona.

    PubMed

    Maiolo, Daniele; Bergese, Paolo; Mahon, Eugene; Dawson, Kenneth A; Monopoli, Marco P

    2014-12-16

    Nanoparticles (NP), when exposed to biological fluids, are coated by specific proteins that form the so-called protein corona. While some adsorbing proteins exchange with the surroundings on a short time scale, described as a "dynamic" corona, others with higher affinity and long-lived interaction with the NP surface form a "hard" corona (HC), which is believed to mediate NP interaction with cellular machineries. In-depth NP protein corona characterization is therefore a necessary step in understanding the relationship between surface layer structure and biological outcomes. In the present work, we evaluate the protein composition and stability over time and we systematically challenge the formed complexes with surfactants. Each challenge is characterized through different physicochemical measurements (dynamic light scattering, ζ-potential, and differential centrifugal sedimentation) alongside proteomic evaluation in titration type experiments (surfactant titration). 100 nm silicon oxide (Si) and 100 nm carboxylated polystyrene (PS-COOH) NPs cloaked by human plasma HC were titrated with 3-[(3-Cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS, zwitterionic), Triton X-100 (nonionic), sodium dodecyl sulfate (SDS, anionic), and dodecyltrimethylammonium bromide (DTAB, cationic) surfactants. Composition and density of HC together with size and ζ-potential of NP-HC complexes were tracked at each step after surfactant titration. Results on Si NP-HC complexes showed that SDS removes most of the HC, while DTAB induces NP agglomeration. Analogous results were obtained for PS NP-HC complexes. Interestingly, CHAPS and Triton X-100, thanks to similar surface binding preferences, enable selective extraction of apolipoprotein AI (ApoAI) from Si NP hard coronas, leaving unaltered the dispersion physicochemical properties. These findings indicate that surfactant titration can enable the study of NP-HC stability through surfactant variation and also selective separation

  12. Treating chemical mechanical polishing (CMP) wastewater by electro-coagulation-flotation process with surfactant.

    PubMed

    Hu, C Y; Lo, S L; Li, C M; Kuan, W H

    2005-04-11

    The effect of surfactants on the treatment of chemical mechanical polishing (CMP) wastewater by electro-coagulation-flotation (ECF) process was studied. Two surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) were employed in this study to compare the effect of cationic (CTAB) and anodic (SDS) surfactants on ECF. The cationic surfactant can enhance the removal of the turbidity, but anodic surfactant cannot. It can be explained by the hetero-coagulation theory. Moreover, the addition of CTAB in CMP wastewater can reduce the sludge volume and the flotation/sedimentation time in ECF process. The residual turbidity and dissolved silicon dropped with the increase of charge loading. No CTAB pollution problem exists after the ECF process. PMID:15811659

  13. Treating chemical mechanical polishing (CMP) wastewater by electro-coagulation-flotation process with surfactant.

    PubMed

    Hu, C Y; Lo, S L; Li, C M; Kuan, W H

    2005-04-11

    The effect of surfactants on the treatment of chemical mechanical polishing (CMP) wastewater by electro-coagulation-flotation (ECF) process was studied. Two surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) were employed in this study to compare the effect of cationic (CTAB) and anodic (SDS) surfactants on ECF. The cationic surfactant can enhance the removal of the turbidity, but anodic surfactant cannot. It can be explained by the hetero-coagulation theory. Moreover, the addition of CTAB in CMP wastewater can reduce the sludge volume and the flotation/sedimentation time in ECF process. The residual turbidity and dissolved silicon dropped with the increase of charge loading. No CTAB pollution problem exists after the ECF process.

  14. Effect of monovalent salt on the conformation of polyelectrolyte-surfactant complexes

    NASA Astrophysics Data System (ADS)

    Diehl, A.; Kuhn, P. S.

    2009-01-01

    We study the conformation of polyelectrolyte-surfactant complexes in the presence of monovalent salt. A simple model for the formation of these structures is presented in the framework of the Debye-Hückel-Bjerrum-Manning and Flory theories, with the hydrophobic interactions between the hydrocarbon tails of surfactant molecules treated in the spirit of van der Waals theory as an effective attraction. The extension of the polyelectrolyte-surfactant complexes is analyzed as a function of the salt concentration and a discrete conformational transition between a compact globule and an elongated coil is found, in agreement with experimental results for the unfolding transition of a DNA-cationic surfactant complex.

  15. Comparative acute toxicities of surfactants to aquatic invertebrates

    SciTech Connect

    Lewis, M.A.; Suprenant, D.

    1983-06-01

    Investigations of the toxicity of surfactants to aquatic invertebrates have been limited primarily to determining the effects on a few species. In this study, the 48-hr LC50 values for three surfactants are reported for six species of aquatic invertebrates. The acute toxicities (LC50) for each surfactant (mg/liter) varied 159 to 580 X and were as follows: C11.8LAS (anionic), 1.7 (Dero sp.) to 270 (Asellus sp.); C14-15 alkylethoxylate (nonionic), 1.0 (Dugesia sp.) to 6.8 (Rhabditis sp.); CTAC (cationic), 0.1 (Gammarus sp.) to 58 (Asellus sp.). When compared to previously developed data, Daphnia magna was typically found to be the most sensitive of all species tested, including fish, to the surfactants.

  16. Surfactant waterflood oil recovery process

    SciTech Connect

    Kudchadker, M.V.; Whittington, L.E.

    1982-03-16

    Disclosed is a surfactant waterflooding oil recovery process for use in high salinity water-containing formations employing two separate surfactant-containing slugs or a single slug in which the composition is changed from the first to the last portion of the slug injected into the formation. The first portion of the surfactant fluid contains a surfactant combination which exhibits optimum low surface tension characteristics, and the second or latter portion of the surfactant slug contains a blend of surfactants which produces a high viscosity fluid. Use of hydrophilic viscosity-increasing polymer is thus avoided, eliminating the interaction between polymer and surfactant which causes a reduction in surfactant effectiveness.

  17. Mechanisms to explain surfactant responses.

    PubMed

    Jobe, Alan H

    2006-01-01

    Surfactant is now standard of care for infants with respiratory distress syndrome. Surfactant treatments are effective because of complex metabolic interactions between surfactant and the preterm lung. The large treatment dose functions as substrate; it is taken up by the preterm lung and is reprocessed and secreted with improved function. The components of the treatment surfactant remain in the preterm lung for days. If lung injury is avoided, then surfactant inhibition is minimized. Prenatal corticosteroids complement surfactant to further enhance lung function. The magic of surfactant therapy results from the multiple interactions between surfactant and the preterm lung.

  18. Photosensitive surfactants: micellization and interaction with DNA.

    PubMed

    Zakrevskyy, Yuriy; Roxlau, Julian; Brezesinski, Gerald; Lomadze, Nino; Santer, Svetlana

    2014-01-28

    Recently, photosensitive surfactants have re-attracted considerable attention. It has been shown that their association with oppositely charged biologically important polyelectrolytes, such as DNA or microgels, can be efficiently manipulated simply by light exposure. In this article, we investigate the self-assembly of photosensitive surfactants as well as their interactions with DNA by calorimetric and spectroscopic methods. Critical micelle concentration (CMC), standard micellization enthalpy, entropy, and Gibbs energy were determined in different conditions (ionic strengths and temperatures) for a series of cationic surfactants with an azobenzene group in their tail. It is shown, that aggregation forces of photosensitive units play an important role in the micellization giving the major contribution to the micellization enthalpy. The onset of the aggregation can be traced from shift of the absorption peak position in the UV-visible spectrum. Titration UV-visible spectroscopy is used as an alternative, simple, and sensitive approach to estimate CMC. The titration UV-visible spectroscopy was also employed to investigate interactions (CAC: critical aggregation concentration, precipitation, and colloidal stabilization) in the DNA-surfactant complex.

  19. SURFACTANTS AND SUBSURFACE REMEDIATION

    EPA Science Inventory

    Because of the limitations of pump-and-trat technology, attention is now focused on the feasibility of surfactant use to increase its efficiency. Surfactants have been studied for use in soil washing and enhanced oil recovery. Although similarities exist between the application...

  20. Potential irritation of lysine derivative surfactants by hemolysis and HaCaT cell viability.

    PubMed

    Sanchez, L; Mitjans, M; Infante, M R; Vinardell, M P

    2006-02-01

    Surfactants represent one of the most common constituents in topical pharmaceutical and cosmetic applications or cleansers. Since adverse skin and ocular reactions can be caused by them, it is important to evaluate damaging effects. Amino acid-based surfactants deserve particular attention because of their low toxicity and environmental friendly properties. New lysine derivative surfactants associated with heavy and light counterions were tested. The ocular irritancy was assessed by hemolysis, and photohemolysis was employed to evaluate their phototoxicity. Cytotoxicity on HaCaT cells was determined by neutral red uptake and MTT assay to predict skin irritation. All lysine derivative surfactants were less hemolytic and thus less eye-irritating than the commercial surfactants used as model irritants. No phototoxic effects were found. All surfactants presented cytotoxic effects as demonstrated by decrease of neutral red uptake and reduction of MTT salt, with clear concentration-effect profiles. However, the rates of cytotoxicity on HaCaT for the new surfactants suggested that they were less cytotoxic and then, less skin-irritating than the reference ones; surfactants with heavy counterions were the less cytotoxic. The anionic surfactants investigated in the present work may constitute a promising class of surfactants given their low irritancy potential for pharmaceutical and cosmetic preparations. PMID:16135402

  1. Modeling Aggregation of Ionic Surfactants Using a Smeared Charge Approximation in Dissipative Particle Dynamics Simulations.

    PubMed

    Mao, Runfang; Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V

    2015-09-01

    Using dissipative particle dynamics (DPD) simulations, we explore the specifics of micellization in the solutions of anionic and cationic surfactants and their mixtures. Anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant cetyltrimethylammonium bromide (CTAB) are chosen as characteristic examples. Coarse-grained models of the surfactants are constructed and parameterized using a combination of atomistic molecular simulation and infinite dilution activity coefficient calibration. Electrostatic interactions of charged beads are treated using a smeared charge approximation: the surfactant heads and dissociated counterions are modeled as beads with charges distributed around the bead center in an implicit dielectric medium. The proposed models semiquantitatively describe self-assembly in solutions of SDS and CTAB at various surfactant concentrations and molarities of added electrolyte. In particular, the model predicts a decline in the free surfactant concentration with the increase of the total surfactant loading, as well as characteristic aggregation transitions in single-component surfactant solutions caused by the addition of salt. The calculated values of the critical micelle concentration reasonably agree with experimental observations. Modeling of catanionic SDS-CTAB mixtures show consecutive transitions to worm-like micelles and then to vesicles caused by the addition of CTAB to micellar solution of SDS. PMID:26241704

  2. The interfacial interactions of Tb-doped silica nanoparticles with surfactants and phospholipids revealed through the fluorescent response.

    PubMed

    Bochkova, Olga D; Mustafina, Asiya R; Mukhametshina, Alsu R; Burilov, Vladimir A; Skripacheva, Viktoriya V; Zakharova, Lucia Ya; Fedorenko, Svetlana V; Konovalov, Alexander I; Soloveva, Svetlana E; Antipin, Igor S

    2012-04-01

    The quenching effect of dyes (phenol red and bromothymol blue) on Tb(III)-centered luminescence enables to sense the aggregation of cationic and anionic surfactants near the silica surface of Tb-doped silica nanoparticles (SN) in aqueous solutions. The Tb-centered luminescence of non-decorated SNs is diminished by the inner filter effect of both dyes. The decoration of the silica surface by cationic surfactants induces the quenching through the energy transfer between silica coated Tb(III) complexes and dye anions inserted into surfactant aggregates. Thus the distribution of surfactants aggregates at the silica/water interface and in the bulk of solution greatly affects dynamic quenching efficiency. The displacement of dye anions from the interfacial surfactant adlayer by anionic surfactants and phospholipids is accompanied by the "off-on" switching of Tb(III)-centered luminescence. PMID:22209651

  3. Characterization and control of surfactant-mediated Norovirus interactions.

    PubMed

    Mertens, Brittany S; Velev, Orlin D

    2015-11-28

    Understanding of the colloidal interactions of Norovirus particles in aqueous medium could provide insights on the origins of the notorious stability and infectivity of these widespread viral agents. We characterized the effects of solution pH and surfactant type and concentration on the aggregation, dispersion, and disassembly of Norovirus virus-like particles (VLPs) using dynamic light scattering, electrophoretic light scattering, and transmission electron microscopy. Owing to net negative surface charge of the VLPs at neutral pH, low concentrations of cationic surfactant tend to aggregate the VLPs, whereas low concentrations of anionic surfactant tend to disperse the particles. Increasing the concentration of these surfactants beyond their critical micelle concentration leads to virus capsid disassembly and breakdown of aggregates. Non-ionic surfactants, however, had little effect on virus interactions and likely stabilized them additionally in suspension. The data were interpreted on the basis of simple models for surfactant binding and re-charging of the virus capsid. We used zeta potential data to characterize virus surface charge and interpret the mechanisms behind these demonstrated surfactant-virus interactions. The fundamental understanding and control of these interactions will aid in practical formulations for virus inactivation and removal from contaminated surfaces.

  4. Effects of Surfactants on Chlorobenzene Absorption on Pyrite Surface

    NASA Astrophysics Data System (ADS)

    Hoa, P. T.; Suto, K.; Inoue, C.; Hara, J.

    2007-03-01

    Recently, both surfactant extraction of chlorinated compounds from contaminated soils and chemical reduction of chlorinated compounds by pyrite have had received a lot of attention. The reaction of the natural mineral pyrite was found as a surface controlling process which strongly depends on absorption of contaminants on the surface. Surfactants were not only aggregated into micelle which increase solubility of hydrophobic compounds but also tend to absorb on the solid surface. This study investigated effects of different kinds of Surfactants on absorption of chlorobenzene on pyrite surface in order to identify coupling potential of surfactant application and remediation by pyrite. Surfactants used including non-ionic, anionic and cationic which were Polyoxyethylene (23) Lauryl Ether (Brij35), Sodium Dodecyl Sulfate (SDS) and Cetyl TrimethylAmmonium Bromide (CTAB) respectively were investigated with a wide range of surfactant concentration up to 4 times of each critical micelle concentration (CMC). Chlorobenzene was chosen as a representative compound. The enhancement or competition effects of Surfactants on absorption were discussed.

  5. Magnetic Surfactants and Polymers with Gadolinium Counterions for Protein Separations.

    PubMed

    Brown, Paul; Bromberg, Lev; Rial-Hermida, M Isabel; Wasbrough, Matthew; Hatton, T Alan; Alvarez-Lorenzo, Carmen

    2016-01-26

    New magnetic surfactants, (cationic hexadecyltrimethlyammonium bromotrichlorogadolinate (CTAG), decyltrimethylammonium bromotrichlorogadolinate (DTAG), and a magnetic polymer (poly(3-acrylamidopropyl)trimethylammonium tetrachlorogadolinate (APTAG)) have been synthesized by the simple mixing of the corresponding surfactants and polymer with gadolinium metal ions. A magnetic anionic surfactant, gadolinium tri(1,4-bis(2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate) (Gd(AOT)3), was synthesized via metathesis. Both routes enable facile preparation of magnetically responsive magnetic polymers and surfactants without the need to rely on nanocomposites or organic frameworks with polyradicals. Electrical conductivity, surface tensiometry, SQUID magnetometry, and small-angle neutron scattering (SANS) demonstrate surface activity and self-aggregation behavior of the magnetic surfactants similar to their magnetically inert parent analogues but with added magnetic properties. The binding of the magnetic surfactants to proteins enables efficient separations under low-strength (0.33 T) magnetic fields in a new, nanoparticle-free approach to magnetophoretic protein separations and extractions. Importantly, the toxicity of the magnetic surfactants and polymers is, in some cases, lower than that of their halide analogues.

  6. Separation of Acids, Bases, and Neutral Compounds

    NASA Astrophysics Data System (ADS)

    Fujita, Megumi; Mah, Helen M.; Sgarbi, Paulo W. M.; Lall, Manjinder S.; Ly, Tai Wei; Browne, Lois M.

    2003-01-01

    Separation of Acids, Bases, and Neutral Compounds requires the following software, which is available for free download from the Internet: Netscape Navigator, version 4.75 or higher, or Microsoft Internet Explorer, version 5.0 or higher; Chime plug-in, version compatible with your OS and browser (available from MDL); and Flash player, version 5 or higher (available from Macromedia).

  7. Jigsaw Cooperative Learning: Acid-Base Theories

    ERIC Educational Resources Information Center

    Tarhan, Leman; Sesen, Burcin Acar

    2012-01-01

    This study focused on investigating the effectiveness of jigsaw cooperative learning instruction on first-year undergraduates' understanding of acid-base theories. Undergraduates' opinions about jigsaw cooperative learning instruction were also investigated. The participants of this study were 38 first-year undergraduates in chemistry education…

  8. The Magic Sign: Acids, Bases, and Indicators.

    ERIC Educational Resources Information Center

    Phillips, Donald B.

    1986-01-01

    Presents an approach that is used to introduce elementary and junior high students to a series of activities that will provide concrete experiences with acids, bases, and indicators. Provides instructions and listings of needed solutions and materials for developing this "magic sign" device. Includes background information and several student…

  9. The effect of surfactant composition on the chemical and structural properties of nanostructured lipid carriers.

    PubMed

    Karn-Orachai, Kullavadee; Smith, Siwaporn Meejoo; Phunpee, Sarunya; Treethong, Alongkot; Puttipipatkhachorn, Satit; Pratontep, Sirapat; Ruktanonchai, Uracha Rungsardthong

    2014-01-01

    Fine-tuning the nanoscale structure and morphology of nanostructured lipid carriers (NLCs) is central to improving drug loading and stability of the particles. The role of surfactant charge on controlling the structure, the physicochemical properties and the stability of NLCs has been investigated using three surfactant types (cationic, anionic, non-ionic), and mixed surfactants. Either one, a mixture of two, or a mixture of three surfactants were used to coat the NLCs, with these classified as one, two and three surfactant systems, respectively. The mixed (two and three) surfactant systems produced smaller NLC particles and yielded NLCs with lower crystallinity than the one surfactant system. The combined effects of the ionic and the non-ionic surfactants may play a key role in assisting the lipid-oil mixing, as well as maintaining colloidal repulsion between NLC particles. In contrast, for the three surfactant system, the lipid-oil mixture in the NLCs appeared less homogenous. This was also reflected in the results of the stability study, which indicated that NLC particle sizes in two surfactant systems appeared to be retained over longer periods than for other surfactant systems. PMID:24861323

  10. Surfactant controlled synthesis of crystalline phosphovanadate nanorods

    SciTech Connect

    Asnani, Minakshi; Thomas, Jency; Sen, Prasenjit; Ramanan, Arunachalam . E-mail: aramanan@chemistry.iitd.ac.in

    2007-04-12

    Phosphovanadate nanorods were obtained in a reaction of vanadium (V) oxide as a precursor and a cationic surfactant, dodecylpyridinium chloride, as structure directing template at pH {approx}3 at room temperature. The composition and morphology of the nanorods was established by powder X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), fourier transform infra-red spectroscopy (FTIR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The obtained nanorods have diameters of 40-60 nm with lengths up to 1 {mu}m. The effect of reaction parameters such as concentration of surfactant and pH of the solution on the growth of nanorods has been investigated. A plausible mechanism involving the coalescence of nanoparticle 'seeds' leading to one-dimensional nanorods is also discussed. The same reaction when performed under hydrothermal condition, keeping other reaction parameters unchanged, resulted in the formation of phosphovanadate nanospheres of diameter 10-15 nm.

  11. Biological properties of sodium alkyl methyl ester sulfonate/alkyltrimethylammonium bromide surfactant mixtures.

    PubMed

    Wong, S P; Lim, W H; Cheng, S F; Chuah, C H

    2012-01-01

    Quaternary ammonium compounds (QACs) are commonly used as disinfectant in medical care, food industry, detergents and glue industries. This is due to a small concentration of QACs is sufficient to inhibit the growth of various bacteria strains. In this work, the inhibitive power of cationic surfactants, alkyltrimethylammonium bromide (C(n)TAB) in the presence of anionic surfactants, sodium alkyl methyl ester α-sulfonate (C(n)MES) was studied. The growth inhibition test with gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria were used to determine the toxicity of single and mixed surfactants. Results from this work showed that certain mixed surfactants have lower minimum inhibition concentration (MIC) as compared to the single C(n)TAB surfactants. Besides that, it was also found that alkyl chain length and the mixing ratios of the surfactants play a significant role in determining the mixture inhibitive power.

  12. The role of ionic surfactants in compression dewatering of alum sludge

    SciTech Connect

    Chu, C.P.; Lee, D.J.; Huang, C.

    1998-10-01

    This work has experimentally investigated the characteristics of filtration followed by consolidation dewatering of an alum sludge, with especial attention to the effects of adding ionic surfactants (SDS or CTAB). The filtration and consolidation stages at a pressure of 3000 psi were discussed separately. The efficiency of filtration is enhanced in the presence of surfactant molecules; however, the cationic surfactant (CTAB) raises the consolidation rate while the anionic surfactant (SDS) retards it. A newly proposed theological model has been employed for interpreting the consolidation data. CTAB would not alter markedly the moisture distribution in the sludge, but SDS does increase markedly the amount of the tightly bound moisture by diminishing the portion occupied by pore water. The possible role of surfactants in the sludge flocs is considered. Both surfactants can be used as conditioning aids during the filtration stage. However, the applications of SDS to the consolidation stage are not encouraged.

  13. Surface properties of coal fines in water. 1. Electrokinetics and surfactant adsorption

    SciTech Connect

    Ayub, A.L.; Al Taweel, A.M.; Kwak, J.C.T.

    1985-01-01

    The adsorption of phenol, p-nitrophenol, the nonionic surfactant Triton X-100 (a commercial mixture of octylphenol poly ethoxylates) and the cationic surfactant dodecyltrimethyl ammonium bromide (DTAB) from aqueous solution on coal fines from a coal washing plant has been studied. Adsorbate solution concentrations range from 0-8 x 10/sup -4/ m. For the cationic and nonionic surfactants both adsorption isotherms and electrokinetic isotherms were determined. The adsorption of phenol, but not of Triton X-100 and DTAB, is found to increase with time for periods up to three hundred h. For short contract times (less than thirty h.), the amount of Triton X-100 adsorbed is about three times higher than the amount of phenol adsorbed at the same solution concentration. The electrokinetic data show that the zeta potential of the coal is not affected by the adsorption of Triton X-100. On the other hand, adsorption of the cationic surfactant strongly influences the zeta potential. For negatively charged coal, i.e., at higher solution pH (iep of the coal used is 5.3), the adsorption of cationic surfactant leads to charge reversal at a typical free surfactant concentration often well below 10/sup -4/ molal. 20 references.

  14. Metathesis depolymerizable surfactants

    DOEpatents

    Jamison, Gregory M.; Wheeler, David R.; Loy, Douglas A.; Simmons, Blake A.; Long, Timothy M.; McElhanon, James R.; Rahimian, Kamyar; Staiger, Chad L.

    2008-04-15

    A class of surfactant molecules whose structure includes regularly spaced unsaturation in the tail group and thus, can be readily decomposed by ring-closing metathesis, and particularly by the action of a transition metal catalyst, to form small molecule products. These small molecules are designed to have increased volatility and/or enhanced solubility as compared to the original surfactant molecule and are thus easily removed by solvent extraction or vacuum extraction at low temperature. By producing easily removable decomposition products, the surfactant molecules become particularly desirable as template structures for preparing meso- and microstructural materials with tailored properties.

  15. Adsorption of surfactants on sand surface in enhanced oil recovery: Isotherms, kinetics and thermodynamic studies

    NASA Astrophysics Data System (ADS)

    Bera, Achinta; Kumar, T.; Ojha, Keka; Mandal, Ajay

    2013-11-01

    Adsorption of surfactants onto reservoir rock surface may result in the loss and reduction of their concentrations in surfactant flooding, which may render them less efficient or ineffective in practical applications of enhanced oil recovery (EOR) techniques. Surfactant flooding for EOR received attraction due to its ability to increase the displacement efficiency by lowering the interfacial tension between oil and water and mobilizing the residual oil. This article highlights the adsorption of surfactants onto sand surface with variation of different influencing factors. It has been experimentally found that adsorption of cationic surfactant on sand surface is more and less for anionic surfactant, while non-ionic surfactant shows intermediate behaviour. X-ray diffraction (XRD) study of clean sand particles has been made to determine the main component present in the sand particles. The interaction between sand particles and surfactant has been studied by Fourier Transform Infrared (FTIR) Spectroscopy of the sand particles before and after aging with surfactant. Salinity plays an important role in adsorption of anionic surfactant. Batch experiments were also performed to understand the effects of pH and adsorbent dose on the sorption efficiency. The sand particles exhibited high adsorption efficiency at low pH for anionic and nonionic surfactants. But opposite trend was found for cationic surfactant. Adsorption data were analyzed by fitting with Langmuir, Freundlich, Redlich-Peterson, and Sips isotherm models. Results show that the Langmuir isotherm and pseudo-second order kinetics models suit the equilibrium and kinetics of adsorption on sand surface. Thermodynamics feasibility of the adsorption process was also studied to verify the spontaneity of the process.

  16. Spectral behaviour of eosin Y in different solvents and aqueous surfactant media.

    PubMed

    Chakraborty, Moumita; Panda, Amiya Kumar

    2011-10-15

    Photophysical behaviour of the anionic xanthene dye, eosin Y (EY) was investigated in solvents of different polarities as well as in the presence of aqueous cationic surfactants. From the correlation between E(T)(30) and Kosower Z values of EY in different solvents, subsequent parameters for EY were determined in the presence of surfactants. A red shift, both in the absorption and emission spectra of EY, was observed with decreasing solvent polarity. Dimerisation of EY was found to be dependent on solvent polarity. Cationic surfactants retarded the process of dimerisation, which were evident from the lower dimerisation constant (K(D)) values, compared to that of in pure water. Dye-surfactant interaction constants were determined at different temperatures (298-318 K) and subsequently the thermodynamic parameters, viz., ΔG°, ΔH° and ΔS° were evaluated using the interaction constant values. The fluorescence spectra of EY followed the same trend as in the absorption spectra, although with lesser extents. Stokes shifts were calculated and correlated with the polarity of the medium. Fluorescence of EY was initially quenched by the cationic surfactants in their pre-micellar region, which then followed a red shift with intensity enhancement. Fluorescence quenching was found to be of Stern-Volmer type where the excited state lifetime of EY remained unchanged in different surfactant media. However, the anisotropy value of EY was changed in the post micellar region of surfactants.

  17. Controlling colloid charge in nonpolar liquids with surfactants.

    PubMed

    Smith, Gregory N; Eastoe, Julian

    2013-01-14

    The formation of ions in nonpolar solvents (with relative permittivity ε(r) of approximately 2) is more difficult than in polar liquids; however, these charged species play an important role in many applications, such as electrophoretic displays. The low relative permittivities of these solvents mean that charges have to be separated by large distances to be stable (approximately 28 nm or 40 times that in water). The inverse micelles formed by surfactants in these solvents provide an environment to stabilize ions and charges. Common surfactants used are sodium dioctylsulfosuccinate (Aerosol OT or AOT), polyisobutylene succinimide, sorbitan oleate, and zirconyl 2-ethyl hexanoate. The behavior of charged inverse micelles has been studied on both the bulk and on the microscopic scale and can be used to determine the motion of the micelles, their structure, and the nature of the electrostatic double layer. Colloidal particles are only weakly charged in the absence of surfactant, but in the presence of surfactants, many types, including polymers, metal oxides, carbon blacks, and pigments, have been observed to become positively or negatively charged. Several mechanisms have been proposed as the origin of surface charge, including acid-base reactions between the colloid and the inverse micelle, preferential adsorption of charged inverse micelles, or dissolution of surface species. While most studies vary only the concentration of surfactant, systematic variation of the particle surface chemistry or the surfactant structure have provided insight into the origin of charging in nonpolar liquids. By carefully varying system parameters and working to understand the interactions between surfactants and colloidal surfaces, further advances will be made leading to better understanding of the origin of charge and to the development of more effective surfactants. PMID:23187453

  18. Tuning of protein-surfactant interaction to modify the resultant structure.

    PubMed

    Mehan, Sumit; Aswal, Vinod K; Kohlbrecher, Joachim

    2015-09-01

    Small-angle neutron scattering and dynamic light scattering studies have been carried out to examine the interaction of bovine serum albumin (BSA) protein with different surfactants under varying solution conditions. We show that the interaction of anionic BSA protein (pH7) with surfactant and the resultant structure are strongly modified by the charge head group of the surfactant, ionic strength of the solution, and mixed surfactants. The protein-surfactant interaction is maximum when two components are oppositely charged, followed by components being similarly charged through the site-specific binding, and no interaction in the case of a nonionic surfactant. This interaction of protein with ionic surfactants is characterized by the fractal structure representing a bead-necklace structure of micellelike clusters adsorbed along the unfolded protein chain. The interaction is enhanced with ionic strength only in the case of site-specific binding of an anionic surfactant with an anionic protein, whereas it is almost unchanged for other complexes of cationic and nonionic surfactants with anionic proteins. Interestingly, the interaction of BSA protein with ionic surfactants is significantly suppressed in the presence of nonionic surfactant. These results with mixed surfactants thus can be used to fold back the unfolded protein as well as to prevent surfactant-induced protein unfolding. For different solution conditions, the results are interpreted in terms of a change in fractal dimension, the overall size of the protein-surfactant complex, and the number of micelles attached to the protein. The interplay of electrostatic and hydrophobic interactions is found to govern the resultant structure of complexes.

  19. Phosphine oxide surfactants revisited.

    PubMed

    Stubenrauch, Cosima; Preisig, Natalie; Laughlin, Robert G

    2016-04-01

    This review summarizes everything we currently know about the nonionic surfactants alkyl dimethyl (C(n)DMPO) and alkyl diethyl (C(n)DEPO) phosphine oxide (PO surfactants). The review starts with the synthesis and the general properties (Section 2) of these compounds and continues with their interfacial properties (Section 3) such as surface tension, surface rheology, interfacial tension and adsorption at solid surfaces. We discuss studies on thin liquid films and foams stabilized by PO surfactants (Section 4) as well as studies on their self-assembly into lyotropic liquid crystals and microemulsions, respectively (Section 5). We aim at encouraging colleagues from both academia and industry to take on board PO surfactants whenever possible and feasible because of their broad variety of excellent properties. PMID:26869216

  20. Zeolite molecular sieves have dramatic acid-base effects on enzymes in nonaqueous media.

    PubMed

    Fontes, Nuno; Partridge, Johann; Halling, Peter J; Barreiros, Susana

    2002-02-01

    Zeolite molecular sieves very commonly are used as in situ drying agents in reaction mixtures of enzymes in nonaqueous media. They often affect enzyme behavior, and this has been interpreted in terms of altered hydration. Here, we show that zeolites can also have dramatic acid-base effects on enzymes in low water media, resulting from their cation-exchange ability. Initial rates of transesterification catalyzed by cross-linked crystals of subtilisin were compared in supercritical ethane, hexane, and acetonitrile with water activity fixed by pre-equilibration. Addition of zeolite NaA (4 A powder) still caused remarkable rate enhancements (up to 20-fold), despite the separate control of hydration. In the presence of excess of an alternative solid-state acid-base buffer, however, zeolite addition had no effect. The more commonly used Merck molecular sieves (type 3 A beads) had similar but somewhat smaller effects. All zeolites have ion-exchange ability and can exchange H+ for cations such as Na+ and K+. These exchanges will tend to affect the protonation state of acidic groups in the protein and, hence, enzymatic activity. Zeolites pre-equilibrated in aqueous suspensions of varying pH-pNa gave very different enzyme activities. Their differing basicities were demonstrated directly by equilibration with an indicator dissolved in toluene. The potential of zeolites as acid-base buffers for low-water media is discussed, and their ability to overcome pH memory is demonstrated.

  1. Acid-base interactions and complex formation while recovering copper(II) ions from aqueous solutions using cellulose adsorbent in the presence of polyvinylpyrrolidone

    NASA Astrophysics Data System (ADS)

    Nikiforova, T. E.; Kozlov, V. A.; Islyaikin, M. K.

    2012-12-01

    The sorption properties of nontreated cotton cellulose and cellulose modified with polyvinylpyrrolidone with respect to copper(II) ions are investigated. It is established that modified cellulose adsorbents have high sorption capability associated with the formation of new sorption centers during treatment with nitrogen-containing polymer. A mechanism is proposed for acid-base interactions in aqueous solutions of acids, bases, and salts during copper(II) cation recovery using cellulose adsorbent with the participation of polyvinylpyrrolidone.

  2. Impact of Polyelectrolyte Chemistry on the Thermodynamic Stability of Oppositely Charged Macromolecule/Surfactant Mixtures.

    PubMed

    Bodnár, Katalin; Fegyver, Edit; Nagy, Miklós; Mészáros, Róbert

    2016-02-01

    The complexation between hexadecyl- and dodecyltrimethylammonium bromides (CTAB and DTAB) with sodium poly[(vinyl alcohol)-co-(vinyl sulfate)] (PVAS) copolymer of low charge density has been investigated using pyrene fluorescence spectroscopy, electrophoretic mobility, turbidity, and dynamic light scattering measurements. The results indicate that the binding of the cationic surfactant occurs in three steps. At low surfactant concentrations, the cationic amphiphile binds to the vinyl sulfate groups. Above charge neutralization, surfactant binding may occur on the surface of the hydrophobic vinyl sulfate/CnTAB nanoassemblies. At even higher concentrations, the surfactant binds on the nonionic vinyl alcohol units of the polyion which reswells the PVAS/CnTAB complexes and makes them highly soluble in water. In earlier studies on oppositely charged ionic surfactants and homopolyelectrolytes the impact of mixing protocols was found remarkable, especially at surfactant excess, where these systems can be trapped in the charge stabilized colloidal dispersion state. In contrast, in the case of PVAS/CnTAB mixtures the effect of mixing is less pronounced and diminishes with increasing ionic strength or decreasing alkyl chain length of the surfactant. These findings are rationalized by taking into account the different binding mechanism of surfactants on oppositely charged homopolyelectrolytes and double hydrophilic copolymers.

  3. Enhancement of DNA compaction by negatively charged nanoparticles: effect of nanoparticle size and surfactant chain length.

    PubMed

    Rudiuk, Sergii; Yoshikawa, Kenichi; Baigl, Damien

    2012-02-15

    We study the compaction of genomic DNA by a series of alkyltrimethylammonium bromide surfactants having different hydrocarbon chain lengths n: dodecyl-(DTAB, n=12), tetradecyl-(TTAB, n=14) and hexadecyl-(CTAB, n=16), in the absence and in the presence of negatively charged silica nanoparticles (NPs) with a diameter in the range 15-100 nm. We show that NPs greatly enhance the ability of all cationic surfactants to induce DNA compaction and that this enhancement increases with an increase in NP diameter. In the absence of NP, the ability of cationic surfactants to induce DNA compaction increases with an increase in n. Conversely, in the presence of NPs, the enhancement of DNA compaction increases with a decrease in n. Therefore, although CTAB is the most efficient surfactant to compact DNA, maximal enhancement by NPs is obtained for the largest NP diameter (here, 100 nm) and the smallest surfactant chain length (here, DTAB). We suggest a mechanism where the preaggregation of surfactants on NP surface mediated by electrostatic interactions promotes cooperative binding to DNA and thus enhances the ability of surfactants to compact DNA. We show that the amplitude of enhancement is correlated with the difference between the surfactant concentration corresponding to aggregation on DNA alone and that corresponding to the onset of adsorption on nanoparticles.

  4. Modeling of alkyl quaternary ammonium cations intercalated into montmorillonite lattice

    SciTech Connect

    Daoudi, El Mehdi; Boughaleb, Yahia; El Gaini, Layla; Meghea, Irina; Bakasse, Mina

    2013-05-15

    Highlights: ► The modification of montmorillonites by three surfactants increases the basal spacing. ► The model proposed show a bilayer conformation for the surfactant ODTMA. ► The DODMA and TOMA surfactants adopt a paraffin type arrangement. ► Behavior of surfactants in interlayer space was confirmed by TGA and ATR analysis. - Abstract: The objective of this work was to study the conformation of the quaternary ammonium cations viz., octadecyl trimethyl ammonium (ODTMA), dioctadecyl dimethyl ammonium (DMDOA) and trioctadecyl methyl ammonium (TOMA) intercalated within montmorillonite. The modified montmorillonite was characterized by X-ray diffraction in small angle (SAXS), thermal analysis (TGA) and infrared spectroscopy of attenuated total reflection (ATR). The modification of organophilic montmorillonites by the three surfactants ODTMA, DMDOA and TOMA increases the basal spacing from their respective intercalated distances of 1.9 nm, 2.6 nm and 3.4 nm respectively. The increase in the spacing due to the basic organic modification was confirmed by the results of thermal analysis (TGA) and infrared spectroscopy (ATR), and also supported by theoretical calculations of longitudinal and transversal chain sizes of these alkyl quaternary ammonium cations.

  5. Highly stable surfactant assisted polyaniline nanostructures with enhanced electroactivity

    NASA Astrophysics Data System (ADS)

    Jamdegni, Monika; Kaur, Amarjeet

    2016-05-01

    Different nanostructures of Polyaniline(PANI) i.e. nanospheres, nanorods, nanofibers and layered structures have been successfully synthesized using varied concentration of anionic sodium dodecyl sulphate(SDS) and cationic Hexamethyltriammonium bromide (HTAB) by electrochemical method. Surfactant assisted morphology has been studied using FESEM. Incorporation of surfactants to the polymer matrix has been confirmed using FTIR spectroscopy. Electro activity and stability towards reversible redox activity was studied using cyclic voltammatry and chronoamperometry.The anionic surfactant severely enhances electroactivity and areal capacitance (3 Fcm-2) which was found to be two order higher than PANI film prepared without surfactant (0.039 Fcm-2), attributable to its additional doping effect. Immobilization of large surfactant molecule to polymer matrix inhibits its degradation due to nuleophilic attack ascribed to hydrophobic effect of surfactant. For PANI-SDS redox behavior remained almost same after 1000 reverse redox cycles while for PANI-HTAB we got only marginal changes.Our PANI-SDS samples are promising candidates for electro chromic applications.

  6. Large scale molecular dynamics study of polymer-surfactant complex

    NASA Astrophysics Data System (ADS)

    Goswami, Monojoy; Sumpter, Bobby

    2012-02-01

    In this work, we study the self-assembly of cationic polyelectrolytes mediated by anionic surfactants in dilute or semi-dilute and gel states. The understanding of the dilute system is a requirement for the understanding of gel states. The importance of polyelectrolyte with oppositely charged colloidal particles can be found in biological systems, such as immobilization of enzymes in polyelectrolyte complexes or nonspecific association of DNA with protein. With the same understanding, interaction of surfactants with polyelectrolytes shows intriguing phenomena that are important for both in academic research as well as industrial applications. Many useful properties of PE surfactant complexes come from the highly ordered structures of surfactant self-assembly inside the PE aggregate. We do large scale molecular dynamics simulation using LAMMPS to understand the structure and dynamics of PE-surfactant systems. Our investigation shows highly ordered ring-string structures that have been observed experimentally in biological systems. We will investigate many different properties of PE-surfactant complexation which will be helpful for pharmaceutical, engineering and biological applications.

  7. Potential use of ascorbic acid-based surfactants as skin penetration enhancers.

    PubMed

    Palma, S D; Maletto, B; Lo Nostro, P; Manzo, R H; Pistoresi-Palencia, M C; Allemandi, D A

    2006-08-01

    6-O-Ascorbic acid alkanoates (ASCn) are amphiphilic molecules having physical-chemical properties that depend on the alkyl chain length. The derivatives of low molecular weight (n < 11) have enough aqueous solubility to produce self-assemblies at room temperature ( approximately 25 degrees C), while those with longer alkyl chains possess a critical micellar temperature (CMT) higher than 30 degrees C. At higher temperatures (T degrees > CMT), ASCn aqueous suspensions turn into either micellar solutions or gel phases, depending on the length of the hydrophobic chain. On cooling, coagels are produced, which possess a lamellar structure that exhibit sharp X-ray diffraction patterns and optical birefringence. The semisolid consistency of such coagels is an interesting property to formulate dermatological pharmaceutical dosage forms able to solubilize and stabilize different drugs. The objective of the present study was the evaluation of the enhancing permeation effect of ASCn with different chain lengths and to correlate permeability changes with histological effects. With this purpose, ASCn coagels containing anthralin (antipsoriasic drug) or fluorescein isothiocyanate (FITC, hydrophobic fluorescent marker) were assayed on rat skin (ex vivo) and mice skin (in vivo), respectively. Also, histological studies were performed aimed at detecting some possible side effects of ASCn. No inflammatory cellular response was observed in the skin when ASCn coagels were applied, suggesting non-irritating properties. Light microscopy indicated slight disruption and fragmentation of stratum corneum. The penetration of ASCn through rat skin epidermis was very fast and quantitatively significant. The permeation of anthralin was significantly increased when the drug was vehiculized in ASCn coagels, compared to other pharmaceutical systems. The results indicated that ASC12 seems to have the highest enhancing effect on FITC permeation. ASC12 appears to be the compound that possesses the highest capacity to enhance the penetration of the drugs. Furthermore, it has the highest permeation of the serie.

  8. Effect of surfactants on the dissociation constants of ascorbic and maleic acids.

    PubMed

    Jaiswal, P V; Ijeri, V S; Srivastava, A K

    2005-11-25

    The dissociation equilibria of ascorbic and maleic acids have been studied in certain cationic, anionic and non-ionic micellar media and their pK(a) values have been evaluated by the potentiometric, conductometric and spectrophotometric techniques. These pK(a) values have been found to shift in micellar media as compared to those in pure water. The differences in the values have been attributed to the solvent properties of the interfacial and bulk phases involving contribution from the micellar surface potential in the case of charged micelles. The values of the limiting molar conductance of the acids have been determined in the various surfactants and were found to be different in different surfactants. In case of the cationic surfactants the limiting molar conductance was found to increase with increase in surfactant concentration.

  9. Adsorption of micelle-forming surfactants from aqueous solutions on disperse titanium boride

    SciTech Connect

    Grodskii, A.S.; Komleva, E.A.; Frolov, Yu.G.

    1988-08-10

    Adsorption studies showed that nonionogenic and cationic surfactants are adsorbed on the surface of disperse titanium boride. Anionic surfactants are virtually not adsorbed due to the negative charge of the particles. It was found that in the region of low concentrations of surfactants in the solution, adsorption of Sintanols takes place in lyophobic regions and the surface of the particles becomes hydrophilic. The Sintamid molecules are adsorbed on the entire interface, including both hydrophobic and hydrophilic sections, with subsequent formation of bimolecular layers by adsorption on hydrophobic sections. Catamine-AB is adsorbed on hydrophilic sections of the surface also with the formation of bimolecular layers. Developed polymolecular layers up to 10-15 nm thick are formed on titanium boride particles from micellar solutions of nonionigenic and cationic surfactants.

  10. Effect of surfactants and temperature on the hyperfiltration performance of poly(ether/urea) membranes

    NASA Technical Reports Server (NTRS)

    Leban, M. I.; Wydeven, T. J.

    1984-01-01

    The individual and combined effects of pasteurization temperature (347 K) and surfactants (anionic, cationic, and neutral) on a poly(ether/urea) thin-film hyperfiltration membrane were studied. Performance of this positively charged membrane was measured in terms of sodium chloride rejection and water flux. The observed effect was mostly on water flux and minimal on salt rejection. Pasteurization temperature caused an irreversible flux decline (flux decline slope of 0.09). The gradual flux reduction caused by neutral and cationic surfactants was reversible, whereas the flux reduction caused by anionic surfactant was irreversible and of similar magnitude to flux reduction caused by pasteurization temperature. The effects of anionic surfactant and pasteurization temperature were additive. Because of flux decline at elevated temperatures the poly(ether/urea) membrane is not very attractive for long-term spaceflight use.

  11. Comparative study on toxic effects induced by oral or intravascular administration of commonly used disinfectants and surfactants in rats.

    PubMed

    Xue, Yuying; Zhang, Shanshan; Tang, Meng; Zhang, Ting; Wang, Yiqing; Hieda, Yoko; Takeshita, Haruo

    2012-07-01

    Accidental ingestion or injection of household products sometimes occurs due to their accessibility, but the toxic manifestations have not been well characterized when they are internally administered. The aim of this study was to investigate the toxic effects induced by ingestion or injection of different ionic surfactants and disinfectants in rats. The test drugs involved benzalkonium and benzethonium (BZK and BZT, both cationic surfactants used as disinfectants), alkyldiaminoethylglycine (AEG, an amphoteric surfactant used as a disinfectant), linear alkylbenzenesulfonate (LAS, an anionic surfactant), polyoxyethylene cetylether (PEC, a nonionic surfactant), chlorhexidine (CHX, not a surfactant but a disinfectant) and saline (control). Male Sprague-Dawley rats were administered one of the test drugs orally (p.o.), intravenously (i.v.) or intraarterially (i.a.). The fatal effects appeared rapidly (<30 min) in i.v.-administered rats, while taking hours (>5 h) in i.a./p.o.-administered rats after a dose of around LD(50) , although the progress and degree of toxic effects varied among the drugs tested. In intravascular administration, BZK and BZT were fatal at doses of 15-20 mg kg(-1) . Higher concentrations in lung and kidney than in blood were determined. CHX showed a high toxic effect compared with cationic surfactants. The rats administered anionic (LAS) or amphoteric (AEG) surfactant died in less than 24 h at doses over 100 mg kg(-1) . In p.o. administration, the toxic effects were concentration/dose-dependent, and all rats administered high doses of surfactants except for PEC died at 5-20 h. The overall toxic ranks could be: cationic surfactant/CHX> anionic/amphoteric surfactant > nonionic surfactant.

  12. Direct observation of unstable reaction intermediates by acid-base complex formation.

    PubMed

    Ohashi, Yuji

    2013-06-01

    The structures of several unstable or metastable reaction intermediates that were photoproduced in crystals were analyzed by using X-ray techniques. The presence of enough void space around the reactive group(s) is an essential factor for the reaction to occur with retention of the single-crystal form. To expand the void space, an acid group (COOH) was substituted onto the reactant molecule and acid-base complex crystals were prepared with several amines, such as dibenzylamine and dicyclohexylamine. Following the formation of such acid-base complexes in crystals, the metastable structures of nitrenes and red species of photochromic salicylideneanilines have been successfully analyzed by using X-ray techniques. Moreover, the structure of a Pt complex anion in the excited state has been analyzed, which formed acid-base complex crystals with various alkylammonium cations. The formation of acid-base complexes will be a powerful tool for directly observing the structure of unstable or metastable reaction intermediates by using X-ray techniques.

  13. Mathematical modeling of acid-base physiology

    PubMed Central

    Occhipinti, Rossana; Boron, Walter F.

    2015-01-01

    pH is one of the most important parameters in life, influencing virtually every biological process at the cellular, tissue, and whole-body level. Thus, for cells, it is critical to regulate intracellular pH (pHi) and, for multicellular organisms, to regulate extracellular pH (pHo). pHi regulation depends on the opposing actions of plasma-membrane transporters that tend to increase pHi, and others that tend to decrease pHi. In addition, passive fluxes of uncharged species (e.g., CO2, NH3) and charged species (e.g., HCO3− , NH4+) perturb pHi. These movements not only influence one another, but also perturb the equilibria of a multitude of intracellular and extracellular buffers. Thus, even at the level of a single cell, perturbations in acid-base reactions, diffusion, and transport are so complex that it is impossible to understand them without a quantitative model. Here we summarize some mathematical models developed to shed light onto the complex interconnected events triggered by acids-base movements. We then describe a mathematical model of a spherical cell–which to our knowledge is the first one capable of handling a multitude of buffer reaction–that our team has recently developed to simulate changes in pHi and pHo caused by movements of acid-base equivalents across the plasma membrane of a Xenopus oocyte. Finally, we extend our work to a consideration of the effects of simultaneous CO2 and HCO3− influx into a cell, and envision how future models might extend to other cell types (e.g., erythrocytes) or tissues (e.g., renal proximal-tubule epithelium) important for whole-body pH homeostasis. PMID:25617697

  14. Mathematical modeling of acid-base physiology.

    PubMed

    Occhipinti, Rossana; Boron, Walter F

    2015-01-01

    pH is one of the most important parameters in life, influencing virtually every biological process at the cellular, tissue, and whole-body level. Thus, for cells, it is critical to regulate intracellular pH (pHi) and, for multicellular organisms, to regulate extracellular pH (pHo). pHi regulation depends on the opposing actions of plasma-membrane transporters that tend to increase pHi, and others that tend to decrease pHi. In addition, passive fluxes of uncharged species (e.g., CO2, NH3) and charged species (e.g., HCO3(-), [Formula: see text] ) perturb pHi. These movements not only influence one another, but also perturb the equilibria of a multitude of intracellular and extracellular buffers. Thus, even at the level of a single cell, perturbations in acid-base reactions, diffusion, and transport are so complex that it is impossible to understand them without a quantitative model. Here we summarize some mathematical models developed to shed light onto the complex interconnected events triggered by acids-base movements. We then describe a mathematical model of a spherical cells-which to our knowledge is the first one capable of handling a multitude of buffer reactions-that our team has recently developed to simulate changes in pHi and pHo caused by movements of acid-base equivalents across the plasma membrane of a Xenopus oocyte. Finally, we extend our work to a consideration of the effects of simultaneous CO2 and HCO3(-) influx into a cell, and envision how future models might extend to other cell types (e.g., erythrocytes) or tissues (e.g., renal proximal-tubule epithelium) important for whole-body pH homeostasis.

  15. Mechanistic insights into the interactions of magnetic nanoparticles with bovine serum albumin in presence of surfactants.

    PubMed

    Joseph, Delina; Sachar, Shilpee; Kishore, Nand; Chandra, Sudeshna

    2015-11-01

    This work reports the physicochemical parameters and the nature of association between magnetic nanoparticles and bovine serum albumin (BSA) in presence of cationic and anionic surfactants. Magnetic iron oxide nanoparticles (MNPs) are first synthesized using chemical co-precipitation method and subsequently characterized by FTIR, XRD, DLS, TEM and Zeta potential. The bare nanoparticles are then coated with BSA and their interactions studied using fluorescence spectroscopy, dynamic light scattering and circular dichroism techniques. The spectroscopic investigation sheds light into various aspects of binding and size variation during the molecular association of BSA with the MNPs in absence and presence of cationic and anionic surfactants. Isothermal titration calorimetry was used to probe the thermodynamic parameters of the systems. MNPs-BSA system was found to be more stable in presence of cationic surfactant. This study provides valuable mechanistic insights into the interactions taking place at the interface of the nanoparticles which further helps in designing a stable colloidal MNPs systems.

  16. Mixed surfactants-directed the mesoporous silica materials with various morphologies and structures

    SciTech Connect

    Lin Huiming; Qu Fengyu; Wu Xiang; Xue Ming; Zhu Guangshan; Qiu Shilun

    2011-06-15

    A new mixed surfactants system using alkyl carboxylic acids and quaternized poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl] urea] (PEPU) as the co-template was used to synthesize mesoporous silica materials with various morphologies and structures, including flakes, regular spheres, nanoparticles, and tube-spheres. The cationic polymer connected the anionic surfactant micelle to the anionic polysilicate species to induce the synthesis of the mesoporous silica materials. The structure and property of the surfactant and the cationic polymer determined the formation of mesoporous silica, and also had a signification influence on the morphology and structure of the final materials. To further explore the possible formation mechanism of these mesoporous materials, zeta potential was utilized to evaluate the interaction between the anionic surfactant and the cationic co-template. In addition, the structure, morphology, and porosity of these materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N{sub 2} adsorption-desorption measurements. - Graphical abstract: A new mixed surfactants system using alkyl carboxylic acids and PEPU as the co-template was used to synthesize mesoporous silica materials with various morphologies and structures. Highlights: {yields}A new mixed surfactants system induced the mesoporous silica materials with various morphologies and structure. > It is a development of the type S{sup -}N{sup +}I{sup -} route of the mesoporous formation. > Zeta potential was utilized to evaluate the interaction between the anionic surfactant and the cationic co-template. > The property and amount of surfactant and polymer determined the formation of the mesoporous materials.

  17. Effects of surfactants on the adsorptive removal of basic dyes from water using an organomineral sorbent-iron humate.

    PubMed

    Janos, Pavel; Smídová, Veronika

    2005-11-01

    The sorption of basic dyes (methylene blue, malachite green, rhodamine B, crystal violet) onto a nonconventional organomineral sorbent-iron humate-was examined in the presence of various kinds of surfactants. It was found that nonionic (Triton X-100) and cationic (cetyltrimethylammonium bromide) surfactants exhibited a relatively small effect on the dye sorption. Anionic surfactants (sodium dodecyl sulfate), on the other hand, affected (in most cases) dramatically the sorption of basic (cationic) dyes. Typically, the dye sorption was enhanced in the presence of low concentrations of anionic surfactants. At high surfactant concentrations, a steep decrease in the dye sorption was observed in some systems, probably due to the formation of micelles that solubilize the dye molecules and prevent their sorption. A model describing these experimental dependencies was proposed. The sorption of basic dyes onto iron humate may be described by the pseudo-second-order kinetic equation. Diffusion processes were identified as the main mechanisms controlling the rate of the dye sorption.

  18. Atrazine and Diuron partitioning within a soil-water-surfactant system

    NASA Astrophysics Data System (ADS)

    Wang, P.; Keller, A.

    2006-12-01

    The interaction between pesticide and soil and water is even more complex in the presence of surfactants. In this study, batch equilibrium was employed to study the sorption of surfactants and the partitioning behaviors of Atrazine and Diuron within a soil-water-surfactant system. Five soils and four surfactants (nonionic Triton- 100, cationic Benzalkonium Chloride (BC), anionic Linear Alkylbenzenesulfonate (LAS), and anionic Sodium Dodecyl Sulfate (SDS)) were used. All surfactant sorption isotherms exhibited an initial linear increase at low surfactant concentrations but reached an asymptotic value as the surfactant concentrations increased. Among the surfactants, BC had the highest sorption onto all soils, followed by Triton-100 and then by LAS and SDS, implying that the nature of the charge significantly influences surfactant sorption. Sorption of either Triton-100 or BC was highly correlated with soil Cation Exchange Capacity (CEC) while that of LAS and SDS was complicated by the presence of Ca2+ and Mg2+ in the aqueous phase and the CEC sites. Both LAS and SDS formed complexes with Ca2+ and Mg2+, resulting in a significant decrease in the detergency of the surfactants. At high surfactant concentrations and with micelles present in the aqueous phase, the micelles formed a more competitive partitioning site for the pesticides, resulting in less pesticide sorbed to the soil. At low Triton-100 and BC concentration, the sorption of the surfactants first resulted in less Atrazine sorption but more Diuron sorption, implying competition between the surfactants and Atrazine, which serves as an indirect evidence that there is a different sorption mechanism for Atrazine. Atrazine is a weak base and it protonates and becomes positively charged near particle surfaces where the pH is much lower than in the bulk solution. The protonated Atrazine may then be held on the CEC sites via electrostatic attraction. Triton-100, LAS and SDS sorbed on the soil showed similar

  19. Acid-base properties of humic and fulvic acids formed during composting.

    PubMed

    Plaza, César; Senesi, Nicola; Polo, Alfredo; Brunetti, Gennaro

    2005-09-15

    The soil acid-base buffering capacity and the biological availability, mobilization, and transport of macro- and micronutrients, toxic metal ions, and xenobiotic organic cations in soil are strongly influenced by the acid-base properties of humic substances, of which humic and fulvic acids are the major fractions. For these reasons, the proton binding behavior of the humic acid-like (HA) and fulvic acid-like (FA) fractions contained in a compost are believed to be instrumental in its successful performance in soil. In this work, the acid-base properties of the HAs and FAs isolated from a mixture of the sludge residue obtained from olive oil mill wastewater (OMW) evaporated in an open-air pond and tree cuttings (TC) at different stages of composting were investigated by a current potentiometric titration method and the nonideal competitive adsorption (NICA)-Donnan model. The NICA-Donnan model provided an excellent description of the acid-base titration data, and pointed out substantial differences in site density and proton-binding affinity between the HAs and FAs examined. With respect to FAs, HAs were characterized by a smaller content of carboxylic- and phenolic-type groups and their larger affinities for proton binding. Further, HAs featured a greater heterogeneity in carboxylic-type groups than FAs. The composting process increased the content and decreased the proton affinity of carboxylic- and phenolic-type groups of HAs and FAs, and increased the heterogeneity of phenolic-type groups of HAs. As a whole, these effects indicated that the composting process could produce HA and FA fractions with greater cation binding capacities. These results suggest that composting of organic materials improves their agronomic and environmental value by increasing their potential to retain and exchange macro- and micronutrients, and to reduce the bioavailability of organic and inorganic pollutants.

  20. Modern quantitative acid-base chemistry.

    PubMed

    Stewart, P A

    1983-12-01

    Quantitative analysis of ionic solutions in terms of physical and chemical principles has been effectively prohibited in the past by the overwhelming amount of calculation it required, but computers have suddenly eliminated that prohibition. The result is an approach to acid-base which revolutionizes our ability to understand, predict, and control what happens to hydrogen ions in living systems. This review outlines that approach and suggests some of its most useful implications. Quantitative understanding requires distinctions between independent variables (in body fluids: pCO2, net strong ion charge, and total weak acid, usually protein), and dependent variables [( HCO-3], [HA], [A-], [CO(2-)3], [OH-], and [H+] (or pH]. Dependent variables are determined by independent variables, and can be calculated from the defining equations for the specific system. Hydrogen ion movements between solutions can not affect hydrogen ion concentration; only changes in independent variables can. Many current models for ion movements through membranes will require modification on the basis of this quantitative analysis. Whole body acid-base balance can be understood quantitatively in terms of the three independent variables and their physiological regulation by the lungs, kidneys, gut, and liver. Quantitative analysis also shows that body fluids interact mainly by strong ion movements through the membranes separating them.

  1. Teaching Acid/Base Physiology in the Laboratory

    ERIC Educational Resources Information Center

    Friis, Ulla G.; Plovsing, Ronni; Hansen, Klaus; Laursen, Bent G.; Wallstedt, Birgitta

    2010-01-01

    Acid/base homeostasis is one of the most difficult subdisciplines of physiology for medical students to master. A different approach, where theory and practice are linked, might help students develop a deeper understanding of acid/base homeostasis. We therefore set out to develop a laboratory exercise in acid/base physiology that would provide…

  2. A General Simulator for Acid-Base Titrations

    NASA Astrophysics Data System (ADS)

    de Levie, Robert

    1999-07-01

    General formal expressions are provided to facilitate the automatic computer calculation of acid-base titration curves of arbitrary mixtures of acids, bases, and salts, without and with activity corrections based on the Davies equation. Explicit relations are also given for the buffer strength of mixtures of acids, bases, and salts.

  3. Using Willie's Acid-Base Box for Blood Gas Analysis

    ERIC Educational Resources Information Center

    Dietz, John R.

    2011-01-01

    In this article, the author describes a method developed by Dr. William T. Lipscomb for teaching blood gas analysis of acid-base status and provides three examples using Willie's acid-base box. Willie's acid-base box is constructed using three of the parameters of standard arterial blood gas analysis: (1) pH; (2) bicarbonate; and (3) CO[subscript…

  4. Surfactant-Amino Acid and Surfactant-Surfactant Interactions in Aqueous Medium: a Review.

    PubMed

    Malik, Nisar Ahmad

    2015-08-01

    An overview of surfactant-amino acid interactions mainly in aqueous medium has been discussed. Main emphasis has been on the solution thermodynamics and solute-solvent interactions. Almost all available data on the topic has been presented in a lucid and simple way. Conventional surfactants have been discussed as amphiphiles forming micelles and amino acids as additives and their effect on the various physicochemical properties of these conventional surfactants. Surfactant-surfactant interactions in aqueous medium, various mixed surfactant models, are also highlighted to assess their interactions in aqueous medium. Finally, their applied part has been taken into consideration to interpret their possible uses.

  5. Phase Transitions in Nanostructured Polyelectrolyte-Surfactant Complexes

    NASA Astrophysics Data System (ADS)

    Leonard, Michael; Strey, Helmut

    2001-03-01

    When a water-soluble polyelectrolyte is combined with an oppositely-charged surfactant solution at a stoichiometric charge ratio, self-assembly into highly-ordered, water-insoluble structures occurs. We have prepared such complexes with poly(sodium acrylate)-co-acrylamide, alginic acid, and chitosan, combined with cationic and anionic surfactants. The phases exhibited by these complexes in aqueous solution are highly sensitive to such factors as osmotic pressure, salt type, ionic strength, and polyelectrolyte charge density. In this study, we have used small angle X-ray scattering to examine osmotic stress-induced structural phase transitions in these complexes under these various environmental conditions. The morphological consequences of combining polyelectrolytes with swollen, emulsion-bound surfactant micelles were also investigated. Results of this work, as well as the potential to use these complexes as nanoporous, biocompatible materials, will be discussed.

  6. Mechanisms of Polyelectrolyte Enhanced Surfactant Adsorption at the Air-Water Interface

    PubMed Central

    Stenger, Patrick C.; Palazoglu, Omer A.; Zasadzinski, Joseph A.

    2009-01-01

    Chitosan, a naturally occurring cationic polyelectrolyte, restores the adsorption of the clinical lung surfactant Survanta to the air-water interface in the presence of albumin at much lower concentrations than uncharged polymers such as polyethylene glycol. This is consistent with the positively charged chitosan forming ion pairs with negative charges on the albumin and lung surfactant particles, reducing the net charge in the double-layer, and decreasing the electrostatic energy barrier to adsorption to the air-water interface. However, chitosan, like other polyelectrolytes, cannot perfectly match the charge distribution on the surfactant, which leads to patches of positive and negative charge at net neutrality. Increasing the chitosan concentration further leads to a reduction in the rate of surfactant adsorption consistent with an over-compensation of the negative charge on the surfactant and albumin surfaces, which creates a new repulsive electrostatic potential between the now cationic surfaces. This charge neutralization followed by charge inversion explains the window of polyelectrolyte concentration that enhances surfactant adsorption; the same physical mechanism is observed in flocculation and re-stabilization of anionic colloids by chitosan and in alternate layer deposition of anionic and cationic polyelectrolytes on charged colloids. PMID:19366599

  7. Essentials in the diagnosis of acid-base disorders and their high altitude application.

    PubMed

    Paulev, P E; Zubieta-Calleja, G R

    2005-09-01

    This report describes the historical development in the clinical application of chemical variables for the interpretation of acid-base disturbances. The pH concept was already introduced in 1909. Following World War II, disagreements concerning the definition of acids and bases occurred, and since then two strategies have been competing. Danish scientists in 1923 defined an acid as a substance able to give off a proton at a given pH, and a base as a substance that could bind a proton, whereas the North American Singer-Hasting school in 1948 defined acids as strong non-buffer anions and bases as non-buffer cations. As a consequence of this last definition, electrolyte disturbances were mixed up with real acid-base disorders and the variable, strong ion difference (SID), was introduced as a measure of non-respiratory acid-base disturbances. However, the SID concept is only an empirical approximation. In contrast, the Astrup/Siggaard-Andersen school of scientists, using computer strategies and the Acid-base Chart, has made diagnosis of acid-base disorders possible at a glance on the Chart, when the data are considered in context with the clinical development. Siggaard-Andersen introduced Base Excess (BE) or Standard Base Excess (SBE) in the extracellular fluid volume (ECF), extended to include the red cell volume (eECF), as a measure of metabolic acid-base disturbances and recently replaced it by the term Concentration of Titratable Hydrogen Ion (ctH). These two concepts (SBE and ctH) represent the same concentration difference, but with opposite signs. Three charts modified from the Siggaard-Andersen Acid-Base Chart are presented for use at low, medium and high altitudes of 2500 m, 3500 m, and 4000 m, respectively. In this context, the authors suggest the use of Titratable Hydrogen Ion concentration Difference (THID) in the extended extracellular fluid volume, finding it efficient and better than any other determination of the metabolic component in acid-base

  8. Essentials in the diagnosis of acid-base disorders and their high altitude application.

    PubMed

    Paulev, P E; Zubieta-Calleja, G R

    2005-09-01

    This report describes the historical development in the clinical application of chemical variables for the interpretation of acid-base disturbances. The pH concept was already introduced in 1909. Following World War II, disagreements concerning the definition of acids and bases occurred, and since then two strategies have been competing. Danish scientists in 1923 defined an acid as a substance able to give off a proton at a given pH, and a base as a substance that could bind a proton, whereas the North American Singer-Hasting school in 1948 defined acids as strong non-buffer anions and bases as non-buffer cations. As a consequence of this last definition, electrolyte disturbances were mixed up with real acid-base disorders and the variable, strong ion difference (SID), was introduced as a measure of non-respiratory acid-base disturbances. However, the SID concept is only an empirical approximation. In contrast, the Astrup/Siggaard-Andersen school of scientists, using computer strategies and the Acid-base Chart, has made diagnosis of acid-base disorders possible at a glance on the Chart, when the data are considered in context with the clinical development. Siggaard-Andersen introduced Base Excess (BE) or Standard Base Excess (SBE) in the extracellular fluid volume (ECF), extended to include the red cell volume (eECF), as a measure of metabolic acid-base disturbances and recently replaced it by the term Concentration of Titratable Hydrogen Ion (ctH). These two concepts (SBE and ctH) represent the same concentration difference, but with opposite signs. Three charts modified from the Siggaard-Andersen Acid-Base Chart are presented for use at low, medium and high altitudes of 2500 m, 3500 m, and 4000 m, respectively. In this context, the authors suggest the use of Titratable Hydrogen Ion concentration Difference (THID) in the extended extracellular fluid volume, finding it efficient and better than any other determination of the metabolic component in acid-base

  9. Revisiting the Thermodynamics of Water Surfaces and the Effects of Surfactant Head Group.

    PubMed

    Hu, Dan; Mafi, Amirhossein; Chou, Keng C

    2016-03-10

    It is common knowledge that surfactants lower the surface tension of water. The typical textbook explanation of this phenomenon is that the force of attraction between surfactant and water molecules is less than that between two water molecules; hence the surface contraction force decreases in the presence of surfactants; however, this common description, based on the strength of intermolecular interactions, is overly simplified because it ignores an important thermodynamic function: the surface entropy of water. Here we report separate measurements of water's surface enthalpy and surface entropy in the presence of nonionic, zwitterionic, anionic, and cationic surfactants. While all of these surfactants decreased the surface enthalpy of water by 50-70%, the surface entropy of water could drop to near-zero or even negative values for ionic surfactants. Studies of this zero-entropy state of water surface using phase-sensitive sum-frequency generation (SFG) vibrational spectroscopy and molecular dynamics (MD) simulations suggested that the zero-entropy state of the water surface was associated with surfactant-induced ordering of water molecules and enhanced hydrogen bond formation at the water surface. Both effects reduce water molecules' degrees of freedom for motion and thus lower the surface entropy of water. The ability of a surfactant to decrease the surface entropy of water is in the order ionic > zwitterionic > nonionic. For all surfactant head groups surface entropy plays a critical role in determining the surface tension of water. The description of water's surface tension is not complete without considering its surface entropy.

  10. NMR spectroscopy of proteins encapsulated in a positively charged surfactant.

    PubMed

    Lefebvre, Brian G; Liu, Weixia; Peterson, Ronald W; Valentine, Kathleen G; Wand, A Joshua

    2005-07-01

    Traditionally, large proteins, aggregation-prone proteins, and membrane proteins have been difficult to examine by modern multinuclear and multidimensional solution NMR spectroscopy. A major limitation presented by these protein systems is that their slow molecular reorientation compromises many aspects of the more powerful solution NMR methods. Several approaches have emerged to deal with the various spectroscopic difficulties arising from slow molecular reorientation. One of these takes the approach of actively seeking to increase the effective rate of molecular reorientation by encapsulating the protein of interest within the protective shell of a reverse micelle and dissolving the resulting particle in a low viscosity fluid. Since the encapsulation is largely driven by electrostatic interactions, the preparation of samples of acidic proteins suitable for NMR spectroscopy has been problematic owing to the paucity of suitable cationic surfactants. Here, it is shown that the cationic surfactant CTAB may be used to prepare samples of encapsulated anionic proteins dissolved in low viscosity solvents. In a more subtle application, it is further shown that this surfactant can be employed to encapsulate a highly basic protein, which is completely denatured upon encapsulation using an anionic surfactant. PMID:15949753

  11. Comparative insight into surfactants mediated amyloidogenesis of lysozyme.

    PubMed

    Chaturvedi, Sumit K; Khan, Javed M; Siddiqi, Mohammad K; Alam, Parvez; Khan, Rizwan H

    2016-02-01

    Electrostatic and hydrophobic interactions have an important role in the protein aggregation. In this study, we have investigated the effect of charge and hydrophobicity of oppositely charged surfactants i.e., anionic (AOT and SDS) and cationic (CTAB and DTAB) on hen egg white lysozyme at pH 9.0 and 13.0, respectively. We have employed various methods such as turbidity measurements, Rayleigh light scattering, ThT, Congo red and ANS dye binding assays, far-UV CD, atomic force microscopy, transmission electron and fluorescence microscopy. At lower molar ratio, both anionic and cationic surfactants promote amyloid fibril formation in lysozyme at pH 9.0 and 13.0, respectively. The aggregation was proportionally increased with respect to protein concentration and hydrophobicity of surfactant. The morphology of aggregates at both the pH was fibrillar in structure, as visualized by dye binding and microscopic imaging techniques. Initially, the interaction between surfactants and lysozyme was electrostatic and then hydrophobic as investigated by ITC. This study demonstrates the crucial role of charge and hydrophobicity during amyloid fibril formation.

  12. Direct Observation Of Nanoparticle-Surfactant Interactions Using Small Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Kumar, Sugam; Aswal, V. K.

    2010-12-01

    Interactions of anionic silica nanoparticles with anionic, cationic and nonionic surfactants have directly been studied by contrast variation small angle neutron scattering (SANS). The measurements are performed on 1 wt% of both silica nanoparticles and surfactants of anionic sodium dodecyle sulphate (SDS), cationic dodecyltrimethyl ammonium bromide (DTAB) and non-ionic polyoxyethylene 10 lauryl ether (C12E10) in aqueous solution. We show that there is no direct interaction in the case of SDS with silica particles, whereas strong interaction for DTAB leads to the aggregation of silica particles. The interaction of C12E10 is found through the micelles adsorbed on the silica particles.

  13. Influence of the surfactant nature on the calcium carbonate synthesis in water-in-oil emulsion

    NASA Astrophysics Data System (ADS)

    Szcześ, Aleksandra

    2009-02-01

    Calcium carbonate has been precipitated from water-in-oil emulsions consisting of n-hexane/nonionic surfactant (Brij 30) and its mixture with cationic (DTAB) or anionic surfactant (SDS) to which calcium chloride and sodium carbonate were added. It was found that the surfactant kind and its amount can regulate the size, form and morphology of the precipitated particles. In case of nonionic surfactant the water/surfactant ratio is the most important parameter that allows to obtain small and regular calcium carbonate crystals. Addition of the DTAB results in different morphology of particles having the same crystal form, whereas addition of SDS changes the kind of emulsion from water-in-oil to oil-in-water. Moreover, light transmittance and backscattering light measurements have been used as a method to study the kinetics of calcium carbonate precipitation in emulsion systems.

  14. Effects of ionic and zwitterionic surfactants on the stabilization of bovine catalase.

    PubMed

    Spreti, N; Bartoletti, A; Di Profio, P; Germani, R; Savelli, G

    1995-01-01

    The activity and stability of beef liver catalase have been investigated in the presence of different ionic and zwitterionic surfactants. All cationic and zwitterionic surfactants used in this work have no effect on the initial activity of catalase, but several of them allow the enzyme to retain a high residual activity for longer periods of time than those observed in the absence of any additives. However, the interactions between surfactants and catalase appear to be very peculiar, and certain zwitterionic surfactants have been found to remarkably slow down enzyme degradation, with the enzyme completely preserving its activity after several weeks at temperatures of up to 30 degrees C. This effect is probably due to an interaction between the surfactant and the intersubunit region of the protein; this interaction could stabilize the quaternary structure of the enzyme. PMID:7765984

  15. Surfactant mixing rules applied to surfactant enhanced alkaline flooding

    SciTech Connect

    Taylor, K.C. )

    1992-01-01

    This paper discusses surfactant mixing rules which have been used to describe crude oil/alkali/surfactant phase behavior, using David Lloydminster crude oil and the surfactant Neodol 25-3S. It was found that at a fixed salinity and alkali concentration, a specific mole fraction of synthetic surfactant to petroleum soap was required to produce optimal phase behavior as the water-to-oil ratio varied. This methodology is useful in understanding the relationship between the variables of water-to-oil ratio and synthetic surfactant concentration in phase behavior systems that produce a petroleum soap.

  16. Isothermal titration calorimetric analysis on solubilization of an octane oil-in-water emulsion in surfactant micelles and surfactant-anionic polymer complexes.

    PubMed

    Zhang, Hui; Zeeb, Benjamin; Salminen, Hanna; Weiss, Jochen

    2015-01-15

    Polymers may alter the ability of surfactant micelles to solubilize hydrophobic molecules depending on surfactant-polymer interactions. In this study, isothermal titration calorimetry (ITC) was used to investigate the solubilization thermodynamics of an octane oil-in-water emulsion in anionic sodium dodecylsulphate (SDS), nonionic polyoxyethylene sorbitan monooleate (Tween 80), cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles and respective complexes formed by these micelles and an anionic polymer (carboxymethyl cellulose). Results indicated that the oil solubilization in single ionic micelles was endothermic, while in nonionic micelles or mixed ionic/nonionic micelles it was exothermic. The addition of carboxymethyl cellulose did not influence the solubilization behavior in these micelles, but affected the solubilization capacities of these systems. The solubilization capacity of cationic micelles or mixed cationic/nonionic micelles was enhanced while that of nonionic or anionic micelles was decreased. Based on the phase separation model, a molecular pathway mechanism driven by enthalpy was proposed for octane solubilization in surfactant micelles and surfactant-polymer complexes.

  17. Hydrophobic, electrostatic, and dynamic polymer forces at silicone surfaces modified with long-chain bolaform surfactants.

    PubMed

    Rapp, Michael V; Donaldson, Stephen H; Gebbie, Matthew A; Das, Saurabh; Kaufman, Yair; Gizaw, Yonas; Koenig, Peter; Roiter, Yuri; Israelachvili, Jacob N

    2015-05-01

    Surfactant self-assembly on surfaces is an effective way to tailor the complex forces at and between hydrophobic-water interfaces. Here, the range of structures and forces that are possible at surfactant-adsorbed hydrophobic surfaces are demonstrated: certain long-chain bolaform surfactants-containing a polydimethylsiloxane (PDMS) mid-block domain and two cationic α, ω-quarternary ammonium end-groups-readily adsorb onto thin PDMS films and form dynamically fluctuating nanostructures. Through measurements with the surface forces apparatus (SFA), it is found that these soft protruding nanostructures display polymer-like exploration behavior at the PDMS surface and give rise to a long-ranged, temperature- and rate-dependent attractive bridging force (not due to viscous forces) on approach to a hydrophilic bare mica surface. Coulombic interactions between the cationic surfactant end-groups and negatively-charged mica result in a rate-dependent polymer bridging force during separation as the hydrophobic surfactant mid-blocks are pulled out from the PDMS interface, yielding strong adhesion energies. Thus, (i) the versatile array of surfactant structures that may form at hydrophobic surfaces is highlighted, (ii) the need to consider the interaction dynamics of such self-assembled polymer layers is emphasized, and (iii) it is shown that long-chain surfactants can promote robust adhesion in aqueous solutions. PMID:25504803

  18. Interactions of univalent counterions with headgroups of monomers and dimers of an anionic surfactant.

    PubMed

    Jakubowska, Anna

    2015-03-24

    Specific ion effects in solution are related to the hydrated ion size and ion hydration, electrostatic interactions, dispersion forces, ion effects on water structure, and ion modification of surface tension. In this study, we tried to identify which factor determines the ion specificity observed. The preference and energy of metal cations binding with the headgroups of dodecylsulfate (DS) monomers and dimers were determined by mass spectrometry. In the gas phase, cation binding to DS dimer headgroups depends strongly on the cation radius. On the other hand, the interactions between DS monomer headgroups and chaotropic ions depend on the cation polarizability, and the binding of kosmotropic cations to DS monomer headgroups strongly depends on the Gibbs free energies of ion hydration. DS dimers are related to surfactants having doubly charged headgroups, and DS monomers are related to surfactants with singly charged headgroups. Our spectrometric study of the strength of counterion binding to free monomers of a surfactant provides insight into surfactant-counterion interactions at micellar interfaces in bulk solution.

  19. An evaluation of lignosulfonate as a sacrificial adsorbate in surfactant flooding

    SciTech Connect

    Hong, S.A.; Bae, J.H.; Lewis, G.R.

    1987-02-01

    A study was conducted to investigate the feasibility of using lignosulfonate as a sacrificial agent in the surfactant flooding process. An analytical technique based on high-performance liquid chromatography (HPLC) analysis was used to determine the concentration of lignosulfonate and petroleum sulfonate. Lignosulfonate and petroleum sulfonate adsorption isotherms were established and used to assess the sacrificial effect of lignosulfonate. A simple model to describe the ion exchange in the presence of lignosulfonate was developed. This model includes the association of cations with lignosulfonate. The main results of this study are as follows. First, surfactant loss can be reduced significantly (> 50% reduction) by pretreatment with a lignosulfonate preflush. However, no significant reduction is obtained when lignosulfonate is incorporated with the surfactant slug. Second, more cations are exchanged from the rock in the presence of lignosulfonate. This enhanced cation exchange is a result of the association of divalent cations with lignosulfonate. Third, lingosulfonate causes dissolution of soluble minerals to a much greater extent than brine or petroleum sulfonate, producing undesirable bivalent cations. Finally, the brine tolerance and optimal salinity of petroleum sulfonate are not greatly affected by lignosulfonate. From these laboratory results, we conclude that lignosulfonate has potential as a sacrificial adsorbate for surfactant flooding.

  20. An evaluation of lignosulfonate as a sacrificial adsorbate in surfactant flooding

    SciTech Connect

    Hong, S.A.; Bae, J.H.; Lewis, G.R.

    1984-04-01

    A study was conducted to investigate the feasibility of using lignosulfonate as a sacrificial agent in the surfactant flooding process. An analytical technique based on HPLC analysis was used to determine the concentration of lignosulfonate and petroleum sulfonate. Lignosulfonate and petroleum sulfonate adsorption isotherms were established and used to assess the sacrificial effect of lignosulfonate. A simple model to describe the ion exchange in the presence of lignosulfonate was developed. This model includes the association of cations with lignosulfonate. The main results of this study are as follows. First, surfactant loss can be reduced significantly > 50% reduction) by pretreatment with a lignosulfonate preflush. However, no significant reduction is obtained when lignosulfonate is incorporated with the surfactant slug. Second, more cations are exchanged from the rock in the presence of lignosulfonate. This enchanced cation-exchange is due to the association of divalent cations with lignosulfonate. Third, lignosulfonate causes dissolution of soluble minerals to a much greater extent than brine or petroleum sulfonate, producing undesirable divalent cations. Finally, the brine tolerance and optimal salinity of petroleum sulfonate are not greatly affected by lignosulfonate. Based on these laboratory results, we conclude that lignosulfonate has potential as a sacrificial adsorbate for surfactant flooding.

  1. Utilizing surfactants to control the sorption, desorption, and biodegradation of phenanthrene in soil-water system.

    PubMed

    Jin, Haiwei; Zhou, Wenjun; Zhu, Lizhong

    2013-07-01

    An integrative technology including the surfactant enhanced sorption and subsequent desorption and biodegradation of phenanthrene in the soil-water system was introduced and tested. For slightly contaminated agricultural soils, cationic-nonionic mixed surfactant-enhanced sorption of organic contaminants onto soils could reduce their transfer to plants, therefore safe-guarding agricultural production. After planting, residual surfactants combined with added nonionic surfactant could also promote the desorption and biodegradation of residual phenanthrene, thus providing a cost-effective pollution remediation technology. Our results showed that the cationic-nonionic mixed surfactants dodecylpyridinium bromide (DDPB) and Triton X-100 (TX100) significantly enhanced soil retention of phenanthrene. The maximum sorption coefficient Kd of phenanthrene for contaminated soils treated by mixed surfactants was about 24.5 times that of soils without surfactant (Kd) and higher than the combined effects of DDPB and TX100 individually, which was about 16.7 and 1.5 times Kd, respectively. On the other hand, TX100 could effectively remove phenanthrene from contaminated soils treated by mixed surfactants, improving the bioavailability of organic pollutants. The desorption rates of phenanthrene from these treated soils were greater than 85% with TX100 concentration above 2000 mg/L and approached 100% with increasing TX100 concentration. The biodegradation rates of phenanthrene in the presence of surfactants reached over 95% in 30 days. The mixed surfactants promoted the biodegradation of phenanthrene to some extent in 10-22 days, and had no obvious impact on phenanthrene biodegradation at the end of the experiment. Results obtained from this study provide some insight for the production of safe agricultural products and a remediation scheme for soils slightly contaminated with organic pollutants.

  2. Sizing up surfactant synthesis.

    PubMed

    Han, SeungHye; Mallampalli, Rama K

    2014-08-01

    Phosphatidylcholine is generated through de novo synthesis and remodeling involving a lysophospholipid. In this issue of Cell Metabolism, research from the Shimizu lab (Harayama et al., 2014) demonstrates the highly selective enzymatic behavior of lysophospholipid acyltransferases. The authors present an enzymatic model for phosphatidylcholine molecular species diversification that impacts surfactant formation.

  3. Surfactant-enhanced bioremediation

    SciTech Connect

    Churchill, P.F.; Dudley, R.J.; Churchill, S.A.

    1995-12-31

    This study was undertaken to examine the effect of three structurally related, non-ionic surfactants, Triton X-45, Triton X-100 and Triton X-165, as well as the oleophilic fertilizer, Inipol EAP 22, on the rate of biodegradation of phenanthrene by pure bacterial cultures. Each surfactant dramatically increased the apparent aqueous solubility of phenanthrene. Model studies were conducted to investigate the ability of these surfactants to enhance the rate of transport and uptake of polycyclic aromatic hydrocarbons into bacterial cells, and to assess the impact that increasing the aqueous solubility of hydrocarbons has on their rate of biodegradation. The results indicate that increasing the apparent aqueous solubility of hydrocarbons can lead to enhanced biodegradation rates by two Pseudomonas saccharophila strains. However, the experiments also suggest that some surfactants can inhibit aromatic hydrocarbon biodegradation by certain bacteria. The data also support the hypothesis that surface-active components present in the oleophilic fertilizer formulation, Inipol EAP 22, may have significantly contributed to the positive results reported in tests of remedial agent impact on bioremediation, which was used as a supplemental clean-up technology on Exxon Valdez crude oil-contaminated Alaskan beaches.

  4. Cation-Coupled Bicarbonate Transporters

    PubMed Central

    Aalkjaer, Christian; Boedtkjer, Ebbe; Choi, Inyeong; Lee, Soojung

    2016-01-01

    Cation-coupled HCO3− transport was initially identified in the mid-1970s when pioneering studies showed that acid extrusion from cells is stimulated by CO2/HCO3− and associated with Na+ and Cl− movement. The first Na+-coupled bicarbonate transporter (NCBT) was expression-cloned in the late 1990s. There are currently five mammalian NCBTs in the SLC4-family: the electrogenic Na,HCO3-cotransporters NBCe1 and NBCe2 (SLC4A4 and SLC4A5 gene products); the electroneutral Na,HCO3-cotransporter NBCn1 (SLC4A7 gene product); the Na+-driven Cl,HCO3-exchanger NDCBE (SLC4A8 gene product); and NBCn2/NCBE (SLC4A10 gene product), which has been characterized as an electroneutral Na,HCO3-cotransporter or a Na+-driven Cl,HCO3-exchanger. Despite the similarity in amino acid sequence and predicted structure among the NCBTs of the SLC4-family, they exhibit distinct differences in ion dependency, transport function, pharmacological properties, and interactions with other proteins. In epithelia, NCBTs are involved in transcellular movement of acid-base equivalents and intracellular pH control. In nonepithelial tissues, NCBTs contribute to intracellular pH regulation; and hence, they are crucial for diverse tissue functions including neuronal discharge, sensory neuron development, performance of the heart, and vascular tone regulation. The function and expression levels of the NCBTs are generally sensitive to intracellular and systemic pH. Animal models have revealed pathophysiological roles of the transporters in disease states including metabolic acidosis, hypertension, visual defects, and epileptic seizures. Studies are being conducted to understand the physiological consequences of genetic polymorphisms in the SLC4-members, which are associated with cancer, hypertension, and drug addiction. Here, we describe the current knowledge regarding the function, structure, and regulation of the mammalian cation-coupled HCO3− transporters of the SLC4-family. PMID:25428855

  5. Binding of 12-s-12 dimeric surfactants to calf thymus DNA: Evaluation of the spacer length influence.

    PubMed

    Sarrión, Beatriz; Bernal, Eva; Martín, Victoria Isabel; López-López, Manuel; López-Cornejo, Pilar; García-Calderón, Margarita; Moyá, María Luisa

    2016-08-01

    Several cationic dimeric surfactants have shown high affinity towards DNA. Bis-quaternary ammonium salts (m-s-m) have been the most common type of dimeric surfactants investigated and it is generally admitted that those that posses a short spacer (s≤3) show better efficiency to bind or compact DNA. However, experimental results in this work show that 12-s-12 surfactants with long spacers make the surfactant/ctDNA complexation more favorable than those with short spacers. A larger contribution of the hydrophobic interactions, which control the binding Gibbs energy, as well as a higher average charge of the surfactant molecules bound to the nucleic acid, which favors the electrostatic attractions, could explain the experimental observations. Dimeric surfactants with intermediate spacer length seem to be the less efficient for DNA binding.

  6. Hot water, surfactant, and polymer flooding process for heavy oil

    SciTech Connect

    Ashrawi, S.S.

    1992-01-28

    This patent describes a method of recovering viscous petroleum from a subterranean, porous and permeable formation penetrated by at least one injection well and by at least one production well, both in fluid communication with the formation. It comprises injecting a thermal recovery fluid into the formation to heat the formation above its natural temperature; injecting a surfactant solution into the formation, the surfactant solution comprising a mixture of petrochemical sulfonate and a co-surfactant, the co-surfactant being an olefin sulfonate having the general formula CH{sub 3}{emdash}(CH{sub 2}){sub x}{emdash}CH{double bond}CH{emdash}(CH{sub 2}){sub y}{emdash}SO{sub 3}{sup {minus}}M{sup +}, wherein x is 0 to 15, x + y is 9 to 15, and M is a monovalent cation; injecting a water-soluble polymer solution into the formation through the same well the surfactant solution was injected into; and recovering petroleum through a production well.

  7. Surfactant/detergent titration analysis method and apparatus for machine working fluids, surfactant-containing wastewater and the like

    DOEpatents

    Smith, Douglas D.; Hiller, John M.

    1998-01-01

    The present invention is an improved method and related apparatus for quantitatively analyzing machine working fluids and other aqueous compositions such as wastewater which contain various mixtures of cationic, neutral, and/or anionic surfactants, soluble soaps, and the like. The method utilizes a single-phase, non-aqueous, reactive titration composition containing water insoluble bismuth nitrate dissolved in glycerol for the titration reactant. The chemical reaction of the bismuth ion and glycerol with the surfactant in the test solutions results in formation of micelles, changes in micelle size, and the formation of insoluble bismuth soaps. These soaps are quantified by physical and chemical changes in the aqueous test solution. Both classical potentiometric analysis and turbidity measurements have been used as sensing techniques to determine the quantity of surfactant present in test solutions. This method is amenable to the analysis of various types of new, in-use, dirty or decomposed surfactants and detergents. It is a quick and efficient method utilizing a single-phase reaction without needing a separate extraction from the aqueous solution. It is adaptable to automated control with simple and reliable sensing methods. The method is applicable to a variety of compositions with concentrations from about 1% to about 10% weight. It is also applicable to the analysis of waste water containing surfactants with appropriate pre-treatments for concentration.

  8. Surfactant/detergent titration analysis method and apparatus for machine working fluids, surfactant-containing wastewater and the like

    DOEpatents

    Smith, D.D.; Hiller, J.M.

    1998-02-24

    The present invention is an improved method and related apparatus for quantitatively analyzing machine working fluids and other aqueous compositions such as wastewater which contain various mixtures of cationic, neutral, and/or anionic surfactants, soluble soaps, and the like. The method utilizes a single-phase, non-aqueous, reactive titration composition containing water insoluble bismuth nitrate dissolved in glycerol for the titration reactant. The chemical reaction of the bismuth ion and glycerol with the surfactant in the test solutions results in formation of micelles, changes in micelle size, and the formation of insoluble bismuth soaps. These soaps are quantified by physical and chemical changes in the aqueous test solution. Both classical potentiometric analysis and turbidity measurements have been used as sensing techniques to determine the quantity of surfactant present in test solutions. This method is amenable to the analysis of various types of new, in-use, dirty or decomposed surfactants and detergents. It is a quick and efficient method utilizing a single-phase reaction without needing a separate extraction from the aqueous solution. It is adaptable to automated control with simple and reliable sensing methods. The method is applicable to a variety of compositions with concentrations from about 1% to about 10% weight. It is also applicable to the analysis of waste water containing surfactants with appropriate pre-treatments for concentration. 1 fig.

  9. Surfactant treatments alter endogenous surfactant metabolism in rabbit lungs

    SciTech Connect

    Oetomo, S.B.; Lewis, J.; Ikegami, M.; Jobe, A.H. )

    1990-04-01

    The effect of exogenous surfactant on endogenous surfactant metabolism was evaluated using a single-lobe treatment strategy to compare effects of treated with untreated lung within the same rabbit. Natural rabbit surfactant, Survanta, or 0.45% NaCl was injected into the left main stem bronchus by use of a Swan-Ganz catheter. Radiolabeled palmitic acid was then given by intravascular injection at two times after surfactant treatment, and the ratios of label incorporation and secretion in the left lower lobe to label incorporation and secretion in the right lung were compared. The treatment procedure resulted in a reasonably uniform surfactant distribution and did not disrupt lobar pulmonary blood flow. Natural rabbit surfactant increased incorporation of palmitate into saturated phosphatidylcholine (Sat PC) approximately 2-fold (P less than 0.01), and secretion of labeled Sat PC increased approximately 2.5-fold in the surfactant-treated left lower lobe relative to the right lung (P less than 0.01). Although Survanta did not alter incorporation, it did increase secretion but not to the same extent as rabbit surfactant (P less than 0.01). Alteration of endogenous surfactant Sat PC metabolism in vivo by surfactant treatments was different from that which would have been predicted by previous in vitro studies.

  10. Surfactant-Triggered Fluorescence Turn "on/off" Behavior of a Polythiophene-graft-Polyampholyte.

    PubMed

    Ghosh, Radhakanta; Das, Sandip; Chatterjee, Dhruba P; Nandi, Arun K

    2016-08-23

    Polythiophene-graft-polyampholyte (PTP) is synthesized using N,N-dimethylaminoethyl methacrylate and tert-butyl methacrylate monomers by grafting from polythiophene backbone, followed by hydrolysis. The resulting polymer exhibits aqueous solubility via formation of small-sized miceller aggregates with hydrophobic polythiophene at the center and radiating polyionic side chains (cationic or anionic depending on the pH of the medium) at the outer periphery. The critical micelle concentration of PTP in acidic solution (0.025 mg/mL, pH = 2.7) is determined from fluorescence spectroscopy. PTP exhibits reversible fluorescence on and off response in both acidic and basic medium with the sequential addition of differently charged ionic surfactants, repeatedly. The fluorescence intensity of PTP at pH 2.7 increases with the addition of an anionic surfactant, sodium dodecyl benzenesulfonate (SDBS), due to the self-aggregation forming compound micelles. The fluorescence intensity of these solutions again decreases on addition of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), because of assembling of SDBS with CTAB, thus deassembling the PTP-SDBS aggregates. At pH 9.2, these turn on and turn off responses are also shown by PTP with the sequential addition of cationic surfactant (CTAB) and anionic surfactant (SDBS), respectively. This result shows that PTP has potential for surfactant-induced reversible fluorescence turn on and off using ionic surfactant (SDBS and CTAB) through self-assembling and deassembling of the ionic aggregates. The reversible aggregation and disaggregation process of PTP with the surfactants at both acidic and basic pH is supported from dynamic light scattering and Fourier transform infrared spectroscopy. The morphology of the above systems studied by transmission and scanning electron microscopy also supports the above aggregation and disaggregation process. PMID:27465928

  11. Drug-induced acid-base disorders.

    PubMed

    Kitterer, Daniel; Schwab, Matthias; Alscher, M Dominik; Braun, Niko; Latus, Joerg

    2015-09-01

    The incidence of acid-base disorders (ABDs) is high, especially in hospitalized patients. ABDs are often indicators for severe systemic disorders. In everyday clinical practice, analysis of ABDs must be performed in a standardized manner. Highly sensitive diagnostic tools to distinguish the various ABDs include the anion gap and the serum osmolar gap. Drug-induced ABDs can be classified into five different categories in terms of their pathophysiology: (1) metabolic acidosis caused by acid overload, which may occur through accumulation of acids by endogenous (e.g., lactic acidosis by biguanides, propofol-related syndrome) or exogenous (e.g., glycol-dependant drugs, such as diazepam or salicylates) mechanisms or by decreased renal acid excretion (e.g., distal renal tubular acidosis by amphotericin B, nonsteroidal anti-inflammatory drugs, vitamin D); (2) base loss: proximal renal tubular acidosis by drugs (e.g., ifosfamide, aminoglycosides, carbonic anhydrase inhibitors, antiretrovirals, oxaliplatin or cisplatin) in the context of Fanconi syndrome; (3) alkalosis resulting from acid and/or chloride loss by renal (e.g., diuretics, penicillins, aminoglycosides) or extrarenal (e.g., laxative drugs) mechanisms; (4) exogenous bicarbonate loads: milk-alkali syndrome, overshoot alkalosis after bicarbonate therapy or citrate administration; and (5) respiratory acidosis or alkalosis resulting from drug-induced depression of the respiratory center or neuromuscular impairment (e.g., anesthetics, sedatives) or hyperventilation (e.g., salicylates, epinephrine, nicotine).

  12. Nano-vectors for the Ocular Delivery of Nucleic Acid-based Therapeutics

    PubMed Central

    Khar, R. K.; Jain, G. K.; Warsi, M. H.; Mallick, N.; Akhter, S; Pathan, S. A.; Ahmad, F. J.

    2010-01-01

    Nucleic acid-based therapeutics have gained a lot of interest for the treatment of diverse ophthalmic pathologies. The first to enter in clinic has been an oligonucleotide, Vitravene® for the treatment of cytomegalovirus infection. More recently, research on aptamers for the treatment of age related macular degeneration has led to the development of Macugen®. Despite intense potential, effective ocular delivery of nucleic acids is a major challenge since therapeutic targets for nucleic acid-based drugs are mainly located in the posterior eye segment, requiring repeated invasive administration. Of late, nanotechnology-based nano-vectors have been developed in order to overcome the drawbacks of viral and other non-viral vectors. The diversity of nano-vectors allows for ease of use, flexibility in application, low-cost of production, higher transfection efficiency and enhanced genomic safety. Using nano-vector strategies, nucleic acids can be delivered either encapsulated or complexed with cationic lipids, polymers or peptides forming sustained release systems, which can be tailored according to the ocular tissue being targeted. The present review focuses on developments and advances in various nano-vectors for the ocular delivery of nucleic acid-based therapeutics, the barriers that such delivery systems face and methods to overcome them. PMID:21969738

  13. Studies on the acid-base properties of the AIBr sub 3 -NaBr melts

    SciTech Connect

    Hayashi, H. ); Hayashi, N.; Takehara, Z. ); Katagiri, A. )

    1989-09-01

    Recently, a lot of work has been performed on the acid-base properties of Lewis acidic molten salts. One of the most extensively investigated melt systems is the sodium chloroaluminate melt (175{degrees}-220{degrees}C) in which the chloride ion activity is dependent upon the composition of the melt. It is well known that unusual higher oxidation state ionic species, such as S(IV) or lower oxidation state cluster compounds, such as W{sub 6}CI{sub 8}{sup 4 +}, can be stable in the chloroaluminate melts because of the strong Lewis acidity of these solvents. These melts are now one of the potential solvents. These melts are now one of the potential materials for use in low-temperature molten salt batteries or as solvents for organic syntheses. The aluminum bromide-sodium bromide melts also show the variable Lewis acidity. Some physical properties of the haloaluminate melts are dependent on the halide species. Therefore, the acid-base properties of the melts also may vary with the anion component, even with the same cationic constituent. The authors discuss how they investigated the acid-base properties of the AIBr{sub 3}-NaBr melts and compared their characteristics with those of the chloroaluminate melts.

  14. Using quantitative acid-base analysis in the ICU.

    PubMed

    Lloyd, P; Freebairn, R

    2006-03-01

    The quantitative acid-base 'Strong Ion' calculator is a practical application of quantitative acid-base chemistry, as developed by Peter Stewart and Peter Constable. It quantifies the three independent factors that control acidity, calculates the concentration and charge of unmeasured ions, produces a report based on these calculations and displays a Gamblegram depicting measured ionic species. Used together with the medical history, quantitative acid-base analysis has advantages over traditional approaches.

  15. Implicit solvent model simulations of surfactant self-assembly in aqueous solutions.

    PubMed

    Morisada, Shintaro; Shinto, Hiroyuki

    2010-05-20

    The behaviors of the cationic surfactants of n-decyltrimethylammonium chloride (C(10)TAC) in water have been studied by the molecular dynamics (MD) simulations using the implicit solvent model proposed in our previous report (J. Chem. Theory Comput. 2007, 3, 1163). The MD simulations of 343 C(10)TAC surfactants in water at the surfactant concentrations of 5-100 mM have been performed for 25 ns, where the surfactant monomers at the initial configurations are uniformly dispersed. As a result, it was found that the C(10)TAC surfactants exist as monomers or oligomers at 5-15 mM, whereas they self-assemble to form surfactant aggregates at 30-100 mM. The growth and the breakup of these surfactant aggregates were repeatedly observed during the 25 ns simulations. The size distributions and the free monomer concentrations indicate that the critical micelle concentration of C(10)TAC surfactant in water represented by the ISM-3 lies between 15 and 30 mM, which fairly agrees with the experimental values of 50-65 mM.

  16. Facile Directed Assembly of Hollow Polymer Nanocapsules within Spontaneously Formed Catanionic Surfactant Vesicles

    SciTech Connect

    Kim, Mariya D.; Dergunov, Sergey; Richter, Andrew; Durbin, Jeffrey; Shmakov, Sergey; Jia, Ying; Kenbeilova, Saltanat; Orazbekuly, Yerbolat; Kengpeiil, Aigerim; Lindner, Erno; Pingali, Sai Venkatesh; Urban, Volker S; Weigand, Steven; Pinkhassik, Eugene

    2014-01-01

    Surfactant vesicles containing monomers in the interior of the bilayer were used to template hollow polymer nanocapsules. This study investigated the formation of surfactant/monomer assemblies by two loading methods, concurrent loading and diffusion loading. The assembly process and the resulting aggregates were investigated with dynamic light scattering, small angle neutron scattering, and small-angle X-ray scattering. Acrylic monomers formed vesicles with a mixture of cationic and anionic surfactants in a broad range of surfactant ratios. Regions with predominant formation of vesicles were broader for compositions containing acrylic monomers compared with blank surfactants. This observation supports the stabilization of the vesicular structure by acrylic monomers. Diffusion loading produced monomer-loaded vesicles unless vesicles were composed from surfactants at the ratios close to the boundary of a vesicular phase region on a phase diagram. Both concurrent-loaded and diffusion-loaded surfactant/monomer vesicles produced hollow polymer nanocapsules upon the polymerization of monomers in the bilayer followed by removal of surfactant scaffolds.

  17. Mixed surfactant systems for enhanced oil recovery

    SciTech Connect

    Llave, F.M.; Gall, B.L.; Noll, L.A.

    1990-12-01

    The results of an evaluation of mixed surfactant systems for enhanced oil recovery are described. Several surfactant combinations have been studied. These include alkyl aryl sulfonates as primary surfactants and carboxymethylated ethoxylated (CME) surfactants and ethoxylated sulfonates (ES) as secondary surfactants. The ethoxylated surfactants increase the salinity tolerance of the primary surfactants and, in theory, allow tailoring of the surfactant system to match selected reservoir conditions. The experiments conducted included interfacial tension (IFT) measurements, phase behavior measurements, adsorption and/or chromatographic separation of mixed surfactant systems, measurements of solution properties such as the critical micelle concentration (CMC) of surfactant mixtures, and crude oil displacement experiments. The effects of temperature, surfactant concentration, salinity, presence of divalent ions, hydrocarbon type, and component proportions in the mixed surfactant combinations, and injection strategies on the performance potential of the targeted surfactant/hydrocarbon systems were studied. 40 refs., 37 figs., 8 tabs.

  18. Enhancement of deoxyribozyme activity by cationic copolymers.

    PubMed

    Gao, Jueyuan; Shimada, Naohiko; Maruyama, Atsushi

    2015-02-01

    Deoxyribozymes, or DNAzymes, are DNA molecules with enzymatic activity. DNAzymes with ribonuclease activity have various potential applications in biomedical and bioanalytical fields; however, most constructs have limited turnover despite optimization of reaction conditions and DNAzyme structures. A cationic comb-type copolymer accelerates DNA hybridization and strand exchange rates, and we hypothesized that the copolymer would enhance deoxyribozyme activity by promoting turnover. The copolymer did not change DNAzyme activity under single-turnover conditions, suggesting that the copolymer affects neither the folding structure of DNAzyme nor the association of a divalent cation, a catalytic cofactor, to DNAzyme. The copolymer enhanced activity of the evaluated DNAzyme over a wide temperature range under multiple-turnover conditions. The copolymer increased the DNAzyme kcat/KM by fifty-fold at 50 °C, the optimal temperature for the DNAzyme in the absence of the copolymer. The acceleration effect was most significant when the reaction temperature was slightly higher than the melting temperature of the enzyme/substrate complex; acceleration of two orders of magnitude was observed. We concluded that the copolymer accelerated the turnover step without influencing the chemical cleavage step. In contrast to the copolymer, a cationic surfactant, CTAB, strongly inhibited the DNAzyme activity under either single- or multiple-turnover conditions. PMID:26218121

  19. Tuning metal–carboxylate coordination in crystalline metal–organic frameworks through surfactant media

    SciTech Connect

    Gao, Junkuo; Ye, Kaiqi; He, Mi; Xiong, Wei-Wei; Cao, Wenfang; Lee, Zhi Yi; Wang, Yue; Wu, Tom; Huo, Fengwei; Liu, Xiaogang; Zhang, Qichun

    2013-10-15

    Although it has been widely demonstrated that surfactants can efficiently control the size, shape and surface properties of micro/nanocrystals of metal–organic frameworks (MOFs) due to the strong interactions between surfactants and crystal facets of MOFs, the use of surfactants as reaction media to grow MOF single crystals is unprecedented. In addition, compared with ionic liquids, surfactants are much cheaper and can have multifunctional properties such as acidic, basic, neutral, cationic, anionic, or even block. These factors strongly motivate us to develop a new synthetic strategy: growing crystalline MOFs in surfactants. In this report, eight new two-dimensional (2D) or three-dimensional (3D) MOFs have been successfully synthesized in an industrially-abundant and environmentally-friendly surfactant: polyethylene glycol-200 (PEG-200). Eight different coordination modes of carboxylates, ranging from monodentate η{sup 1} mode to tetra-donor coordination µ{sub 3}-η{sup 1}:η{sup 2}:η{sup 1} mode, have been founded in our research. The magnetic properties of Co-based MOFs were investigated and MOF NTU-Z6b showed a phase transition with a Curie temperature (T{sub c}) at 5 K. Our strategy of growing crystalline MOFs in surfactant could offer exciting opportunities for preparing novel MOFs with diverse structures and interesting properties. - Graphical abstract: Surfactants have been used as reaction media to grow MOF single crystals for the first time. Eight new two-dimensional or three-dimensional MOFs were successfully synthesized in surfactant polyethylene glycol-200 (PEG-200). Coordination modes of carboxylates up to eight were founded. Our strategy of growing crystalline MOFs in surfactant could offer exciting opportunities for preparing novel MOFs with diverse structures and interesting properties. Display Omitted - Highlights: • Surfactant-thermal synthesis of crystalline metal–organic frameworks. • Eight new 2-D or 3-D metal–organic frameworks

  20. Renal acid-base metabolism after ischemia.

    PubMed

    Holloway, J C; Phifer, T; Henderson, R; Welbourne, T C

    1986-05-01

    The response of the kidney to ischemia-induced cellular acidosis was followed over the immediate one hr post-ischemia reflow period. Clearance and extraction experiments as well as measurement of cortical intracellular pH (pHi) were performed on Inactin-anesthetized Sprague-Dawley rats. Arteriovenous concentration differences and para-aminohippurate extraction were obtained by cannulating the left renal vein. Base production was monitored as bicarbonate released into the renal vein and urine; net base production was related to the renal handling of glutamine and ammonia as well as to renal oxygen consumption and pHi. After a 15 min control period, the left renal artery was snared for one-half hr followed by release and four consecutive 15 min reflow periods. During the control period, cortical cell pHi measured by [14C]-5,5-Dimethyl-2,4-Oxazolidinedione distribution was 7.07 +/- 0.08, and Q-O2 was 14.1 +/- 2.2 micromoles/min; neither net glutamine utilization nor net bicarbonate generation occurred. After 30 min of ischemia, renal tissue pH fell to 6.6 +/- 0.15. However, within 45 min of reflow, cortical cell pH returned and exceeded the control value, 7.33 +/- 0.06 vs. 7.15 +/- 0.08. This increase in pHi was associated with a significant rise in cellular metabolic rate, Q-O2 increased to 20.3 +/- 6.4 micromoles/min. Corresponding with cellular alkalosis was a net production of bicarbonate and a net ammonia uptake and glutamine release; urinary acidification was abolished. These results are consistent with a nonexcretory renal metabolic base generating mechanism governing cellular acid base homeostasis following ischemia. PMID:3723929

  1. Surfactants at the Design Limit.

    PubMed

    Czajka, Adam; Hazell, Gavin; Eastoe, Julian

    2015-08-01

    This article analyzes how the individual structural elements of surfactant molecules affect surface properties, in particular, the point of reference defined by the limiting surface tension at the aqueous cmc, γcmc. Particular emphasis is given to how the chemical nature and structure of the hydrophobic tails influence γcmc. By comparing the three different classes of surfactants, fluorocarbon, silicone, and hydrocarbon, a generalized surface packing index is introduced which is independent of the chemical nature of the surfactants. This parameter ϕcmc represents the volume fraction of surfactant chain fragments in a surface film at the aqueous cmc. It is shown that ϕcmc is a useful index for understanding the limiting surface tension of surfactants and can be useful for designing new superefficient surfactants.

  2. Solubilization of octane in electrostatically-formed surfactant-polymer complexes.

    PubMed

    Zhang, Hui; Zeeb, Benjamin; Salminen, Hanna; Feng, Fengqin; Weiss, Jochen

    2014-03-01

    Polymers can be used to modulate the stability and functionality of surfactant micelles. The purpose of this study was to investigate the solubilization of an octane oil-in-water emulsion in mixtures of an anionic polymer (carboxymethyl cellulose) and anionic sodium dodecylsulphate (SDS), nonionic polyoxyethylene sorbitan monooleate (Tween 80) and cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles using dynamic light scattering, microelectrophoresis and turbidity measurements. The results showed that the addition of anionic carboxymethyl cellulose accelerated octane solubilization in cationic CTAB and CTAB-Tween 80 micelles, but did not affect the solubilization behaviors of micelles that were nonionic and anionic. The surfactant-polymer interactions were also studied using isothermal titration calorimetry (ITC) to characterize different physiochemical interaction regions depending on surfactant concentration in surfactant-polymer systems. Upon octane solubilization in CTAB-carboxymethyl cellulose mixtures, shape transitions of polymer-micelle complexes may have taken place that altered light scattering behavior. Based on these results, we suggest a mechanism for oil solubilization in electrostatically-formed surfactant-polymer complexes.

  3. Ecotoxicities of polyquaterniums and their associated polyelectrolyte-surfactant aggregates (PSA) to Gambusia holbrooki.

    PubMed

    Cumming, Janet L; Hawker, Darryl W; Nugent, Kerry W; Chapman, Heather F

    2008-02-01

    The toxicity of 11 polyquaterniums used in cosmetic applications, and polydimethyldiallylammonium chloride (poly(DADMAC)) were studied for toxicity of the polyquaternium alone, and of a polyquaternium/anionic surfactant complex as occurs in some cosmetic formulations. The surfactant used in the study was sodium dodecyl sulfate (SDS), which is used in cosmetic formulations under its International Nomenclature of Cosmetic Ingredients (INCI) name Sodium Laurel Sulfate. In fish immobilization studies with Gambusia holbrooki, the EC(50) of the polyquaternium/surfactant complex was found to be the same as or similar to the EC(50) for the polyquaternium alone. The toxicity of the polyquaterniums investigated was similar to the published values for other cationic polyelectrolytes and cationic surfactants, in the range from < 1.0 to 10 mg/L, with the exception of low charge density cellulosic polyquaterniums. The anionic surfactant alone was not toxic to fish in the concentration range tested. Results thus showed the toxicity of the polyquaternium was not mitigated by the presence of the anionic surfactant.

  4. Ecotoxicities of polyquaterniums and their associated polyelectrolyte-surfactant aggregates (PSA) to Gambusia holbrooki.

    PubMed

    Cumming, Janet L; Hawker, Darryl W; Nugent, Kerry W; Chapman, Heather F

    2008-02-01

    The toxicity of 11 polyquaterniums used in cosmetic applications, and polydimethyldiallylammonium chloride (poly(DADMAC)) were studied for toxicity of the polyquaternium alone, and of a polyquaternium/anionic surfactant complex as occurs in some cosmetic formulations. The surfactant used in the study was sodium dodecyl sulfate (SDS), which is used in cosmetic formulations under its International Nomenclature of Cosmetic Ingredients (INCI) name Sodium Laurel Sulfate. In fish immobilization studies with Gambusia holbrooki, the EC(50) of the polyquaternium/surfactant complex was found to be the same as or similar to the EC(50) for the polyquaternium alone. The toxicity of the polyquaterniums investigated was similar to the published values for other cationic polyelectrolytes and cationic surfactants, in the range from < 1.0 to 10 mg/L, with the exception of low charge density cellulosic polyquaterniums. The anionic surfactant alone was not toxic to fish in the concentration range tested. Results thus showed the toxicity of the polyquaternium was not mitigated by the presence of the anionic surfactant. PMID:18172802

  5. Gemini surfactants with a disaccharide spacer.

    PubMed

    Menger, F M; Mbadugha, B N

    2001-02-01

    A gemini surfactant is an amphiphile possessing (in sequence) the following: hydrocarbon tail/polar group/spacer/polar group/hydrocarbon tail. Widespread interest in geminis has emerged recently from both industrial and academic laboratories. In the present contribution, two related families of geminis have been synthesized, both with trehalose, a disaccharide, as a polar spacer. One family, Series-A, is nonionic and has amide groups separating the long chains from the trehalose spacer. The other family, Series-B, has quaternary ammonium ions connecting the long chains to the trehalose spacer. It was found that Series-A geminis are water insoluble despite the two amides and multiple hydroxyls. When hydrated or extruded, these geminis form microscopically visible vesicular and tubular structures above their transition temperatures (which were determined calorimetrically). Insoluble monomolecular films, constructed from these geminis, have interfacial areas that are dominated by the sugar spacer although intermolecular chain/chain interactions seem to stabilize the films. Thus, the behavior of Series-A geminis in many ways parallels that of phospholipids and simple double-chain surfactants. It is as if the trehalose is less of a spacer than a large but conventional headgroup. In contrast, cationic Series-B geminis are water soluble and form micelles with critical micelle concentrations an order of magnitude lower than that of corresponding conventional surfactants. Molecular modeling using the Amber force field explains the difference in properties between the two families of geminis. Series-A are tubular in shape and thus prefer bilayer packing as do other amphiphiles in which the headgroups are similar in width to the sum of the tail diameters. Series-B geminis are conical-shaped and pack more readily into spherical micelles. This work entails synthesis, tensiometry, conductance, microscopy, surface balance studies, calorimetry, light scattering, and molecular

  6. Structural features of the nonionic surfactants stabilizing long-lived bubble nuclei

    NASA Technical Reports Server (NTRS)

    Darrigo, J. S.

    1980-01-01

    A study of the effects of various electrolytes and one organic compound on bubble production in agarose gels is presented. Several preparations of ultrapure agarose were compared for 42 electrolytes and phenol to identify trends in bubble formation. The anion and cation sequences of bubble suppression are similar to processes for salting out of nonionic surfactants. The reduction of bubble number by polyvalent ions and 1% phenol suggests that the polar portions of these nonionic surfactants represent amide groups. The evidence for amide groups is consistent with the relative positions of Mg(2+) in all cation sequences; this result makes it unlikely that either linkages contribute to the hydrophilicity of the nonionic surfactants stabilizing bubble nuclei in the different aqueous gels tested.

  7. Roles of urea production, ammonium excretion, and amino acid oxidation in acid-base balance.

    PubMed

    Mackenzie, W

    1986-02-01

    Atkinson and colleagues recently proposed several concepts that contrast with traditional views: first, that acid-base balance is regulated chiefly by the reactions leading to urea production in the liver; second, that ammonium excretion by the kidney plays no role in acid-base homeostasis; and third, that ammonium does not stimulate ureagenesis (except indirectly). To examine these concepts, plasma ions other than bicarbonate are categorized as 1) fixed cations (Na+, K+, Ca2+, and Mg2+, symbolized M+) and anions (Cl-), 2) buffer anions (A-), 3) other anions (X-), and 4) ammonium plus charged amino groups (N+). Since electroneutrality dictates that M+ + N+ = Cl- + HCO3- + A- + X-, it follows that delta HCO3- = delta(M+ - Cl-) - delta A- - delta X- + delta N+. Therefore acid-base disturbances (changes in HCO3-) can be categorized as to how they affect bodily content and hence plasma concentration of each of these four types of ions. The stoichiometry of ureagenesis, glutamine hydrolysis, ammonium and titratable acid excretion, oxidation of neutral, acidic, and basic amino acids, and oxidation of methionine, phosphoserine, and protein are examined to see how they alter these quantities. It is concluded that 1) although ureagenesis is pH dependent and also counteracts a tendency of amino acid oxidation to cause alkalosis, this tendency is inherently limited by the hyperammonemia (delta N+) that necessarily accompanies it, 2) ammonium excretion is equivalent to hydrogen excretion in its effects on acid-base balance if, and only if, it occurs in exchange for sodium or is accompanied by chloride excretion and only when the glutamate generated by glutamine hydrolysis is oxidized.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3511732

  8. Surfactant waterflooding oil recovery method

    SciTech Connect

    Schievelbein, V.H.

    1981-12-29

    Oil is recovered from an underground petroleum reservoir which contains a brine having a salinity of from 50 to 220 kg/m3 total dissolved solids by injecting an alkylarylpolyalkoxy sulfate or alkylpolyalkoxy sulfate surfactant that exhibits phase stability in the brine or diluted brine. The surfactant is injected in an aqueous solution which is prepared with diluted brine which has a salinity slightly less than that required to cause partitioning of the surfactant out of the aqueous phase into the oil-water interface or oil phase. The injection of surfactant is followed by the injecting of a driving slug comprised of either diluted brine or thickened diluted brine.

  9. Surfactant and process for enhanced oil recovery

    SciTech Connect

    Stapp, P. R.

    1984-12-11

    A novel surfactant is formed by reacting maleic anhydride with either a petroleum sulfonate or an alkaryl sulfonate. A surfactant system containing the above surfactant useful in enhanced oil recovery processes is also provided.

  10. What is the Ultimate Goal in Acid-Base Regulation?

    ERIC Educational Resources Information Center

    Balakrishnan, Selvakumar; Gopalakrishnan, Maya; Alagesan, Murali; Prakash, E. Sankaranarayanan

    2007-01-01

    It is common to see chapters on acid-base physiology state that the goal of acid-base regulatory mechanisms is to maintain the pH of arterial plasma and not arterial PCO [subscript 2] (Pa[subscript CO[subscript 2

  11. A Closer Look at Acid-Base Olfactory Titrations

    ERIC Educational Resources Information Center

    Neppel, Kerry; Oliver-Hoyo, Maria T.; Queen, Connie; Reed, Nicole

    2005-01-01

    Olfactory titrations using raw onions and eugenol as acid-base indicators are reported. An in-depth investigation on olfactory titrations is presented to include requirements for potential olfactory indicators and protocols for using garlic, onions, and vanillin as acid-base olfactory indicators are tested.

  12. A Modern Approach to Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Drago, Russell S.

    1974-01-01

    Summarizes current status of our knowledge about acid-base interactions, including Lewis considerations, experimental design, data about donor-acceptor systems, common misconceptions, and hard-soft acid-base model. Indicates that there is the possibility of developing unifying concepts for chemical reactions of inorganic compounds. (CC)

  13. Cationic additives in nanosystems activate cytotoxicity and inflammatory response of human neutrophils: lipid nanoparticles versus polymeric nanoparticles

    PubMed Central

    Hwang, Tsong-Long; Aljuffali, Ibrahim A; Lin, Chwan-Fwu; Chang, Yuan-Ting; Fang, Jia-You

    2015-01-01

    This report compares the effect of lipid and polymeric nanoparticles upon human neutrophils in the presence of cationic surfactants. Nanostructured lipid carriers and poly(lactic-co-glycolic) acid nanoparticles were manufactured as lipid and polymeric systems, respectively. Some cytotoxic and proinflammatory mediators such as lactate dehydrogenase (LDH), elastase, O2•−, and intracellular Ca2+ were examined. The nanoparticles showed a size of 170–225 nm. Incorporation of cetyltrimethylammonium bromide or soyaethyl morpholinium ethosulfate, the cationic surfactant, converted zeta potential from a negative to a positive charge. Nanoparticles without cationic surfactants revealed a negligible change on immune and inflammatory responses. Cationic surfactants in both nanoparticulate and free forms induced cell death and the release of mediators. Lipid nanoparticles generally demonstrated a greater response compared to polymeric nanoparticles. The neutrophil morphology observed by electron microscopy confirmed this trend. Cetyltrimethylammonium bromide as the coating material showed more significant activation of neutrophils than soyaethyl morpholinium ethosulfate. Confocal microscope imaging displayed a limited internalization of nanoparticles into neutrophils. It is proposed that cationic nanoparticles interact with the cell membrane, triggering membrane disruption and the following Ca2+ influx. The elevation of intracellular Ca2+ induces degranulation and oxidative stress. The consequence of these effects is cytotoxicity and cell death. Caution should be taken when selecting feasible nanoparticulate formulations and cationic additives for consideration of applicability and toxicity. PMID:25609950

  14. Assessment of acid-base balance. Stewart's approach.

    PubMed

    Fores-Novales, B; Diez-Fores, P; Aguilera-Celorrio, L J

    2016-04-01

    The study of acid-base equilibrium, its regulation and its interpretation have been a source of debate since the beginning of 20th century. Most accepted and commonly used analyses are based on pH, a notion first introduced by Sorensen in 1909, and on the Henderson-Hasselbalch equation (1916). Since then new concepts have been development in order to complete and make easier the understanding of acid-base disorders. In the early 1980's Peter Stewart brought the traditional interpretation of acid-base disturbances into question and proposed a new method. This innovative approach seems more suitable for studying acid-base abnormalities in critically ill patients. The aim of this paper is to update acid-base concepts, methods, limitations and applications.

  15. Surfactant phosphatidylcholine metabolism and surfactant function in preterm, ventilated lambs

    SciTech Connect

    Jobe, A.H.; Ikegami, M.; Seidner, S.R.; Pettenazzo, A.; Ruffini, L.

    1989-02-01

    Preterm lambs were delivered at 138 days gestational age and ventilated for periods up to 24 h in order to study surfactant metabolism and surfactant function. The surfactant-saturated phosphatidylcholine pool in the alveolar wash was 13 +/- 4 mumol/kg and did not change from 10 min to 24 h after birth. Trace amounts of labeled natural sheep surfactant were mixed with fetal lung fluid at birth. By 24 h, 80% of the label had become lung-tissue-associated, yet there was no loss of label from phosphatidylcholine in the lungs when calculated as the sum of the lung tissue plus alveolar wash. De novo synthesized phosphatidylcholine was labeled with choline given by intravascular injection at 1 h of age. Labeled phosphatidylcholine accumulated in the lung tissue linearly to 24 h, and the labeled phosphatidylcholine moved through lamellar body to alveolar pools. The turnover time for alveolar phosphatidylcholine was estimated to be about 13 h, indicating an active metabolic pool. A less surface-active surfactant fraction recovered as a supernatant after centrifugation of the alveolar washes at 40,000 x g increased from birth to 10 min of ventilation, but no subsequent changes in the distribution of surfactant phosphatidylcholine in surfactant fractions occurred. The results were consistent with recycling pathway(s) that maintained surface-active surfactant pools in preterm ventilated lambs.

  16. Synthesis and bio-physicochemical properties of amide-functionalized N-methylpiperazinium surfactants.

    PubMed

    Chauhan, Vinay; Singh, Sukhprit; Mishra, Rachana; Kaur, Gurcharan

    2014-12-15

    Four new amide functionalized N-methylpiperazinium amphiphiles having tetradecyl, hexadecyl alkyl chain lengths and counterions; chloride or bromide have been synthesized and characterized by various spectroscopic techniques. These new surfactants have been investigated in detail for their self-assembling behavior by surface tension, conductivity and fluorescence measurements. The thermodynamic parameters of these surfactants indicate that micellization is exothermic and entropy-driven. The dynamic light scattering (DLS) and transmission electron microscopy (TEM) experiments have been performed to insight the aggregate size of these cationics. Thermal degradation of these new surfactants has also been evaluated by thermal gravimetric analysis (TGA). These new surfactants form stable complexes with DNA as acknowledged by agarose gel electrophoresis, ethidium bromide exclusion and zeta potential measurements. They have also been found to have low cytotoxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on the C6 glioma cell line.

  17. Effect of surfactants on the survival and sorption of viruses.

    PubMed

    Chattopadhyay, Devamita; Chattopadhyay, Sandip; Lyon, William G; Wilson, John T

    2002-10-01

    There is an increasing concern about the protection of groundwater from contamination by enteric viruses and the prevention of outbreaks of waterborne diseases. Knowledge of survivability and transport of viruses from their point of origin is necessary to determine their potential effects on the neighboring groundwater systems. The distribution of virus is, in turn, dependent on the physical and chemical compositions of the surrounding soil and subsurface systems. For the present study, we have determined the effects of different surfactants (cationic, anionic, nonionic, and biological) and natural organic matter (NOM) on bacteriophages. Results indicated that surfactants and NOM adversely affect phage survival in binary systems, with surfactants being the most harmful. Studies with ternary systems also showed that the presence of surfactants reduced sorption of phages on sorbents either by occupying available sorption sites on the sorbent material or by displacing the sorbed phages from the sorbent surface. Water contact angles of the selected phages and different sorbent surfaces have been measured. Experimental data demonstrated that the sorption of hydrophobic viruses was favored by hydrophobic sorbents, while the sorption of hydrophilic viruses was favored by hydrophilic sorbents.

  18. Influence of polymer-surfactant aggregates on fluid flow.

    PubMed

    Malcher, Tadeusz; Gzyl-Malcher, Barbara

    2012-10-01

    This paper describes the influence of interactions of poly(ethylene oxide) (PEO) with cationic cetyltrimethylammonium bromide (CTAB) micelles on drag reduction. Since the interactions between PEO and CTAB micelles alone are weak, salicylate ions were used as CTAB counterions. They facilitate formation of polymer-micelle aggregates by screening the electrostatic repulsions between the charged surfactant headgroups. The influence of polymer-surfactant interactions on drag reduction is of biomedical engineering importance. Drag reducing additives introduced to blood produce beneficial effects on blood circulation, representing a novel way to treat cardiovascular disorders. PEO is a blood-compatible polymer. However, it quickly mechanically degrades when subjected to high shear stresses. Thus, there is a need to search for other additives able to reduce drag, which would be more mechanically stable, e.g. polymer-surfactant aggregates. Numerical simulations of the flow were performed using the CFX software. Based on the internal structure of the polymer-surfactant solution, a hypothesis explaining the reason of increase of drag reduction and decrease in dynamic viscosity with increasing shear rate was proposed. It was suggested that the probable reason for the abrupt increase in friction factor, observed when the critical Reynolds number was exceeded, was the disappearance of the difference in the dynamic viscosity.

  19. Enhanced oil recovery by surfactant-enhanced volumetric sweep efficiency: First annual report for the period September 30, 1985-September 30, 1986. [Sandpacks

    SciTech Connect

    Harwell, J H; Scamehorn, J F

    1987-05-01

    Surfactant-enhanced volumetric sweep efficiency is a novel EOR method which utilizes precipitation/coacervation of surfactants to plug the most permeable regions of the reservoir, improving the efficiency of a waterflooding operation. This technique does not rely on reduction of interfacial tension between aqueous and oleic phases to enhance oil recovery. Therefore, even though surfactants are involved, this new technique is not a substitute or improvement on classical surfactant flooding; however, it has the potantial to compete with polymer flooding as an alternative sweep efficiency improvement method. In surfactant-enhanced volumetric sweep efficiency, a slug containing one kind of surfactant is injected into the reservoir, followed by a brine spacer. This is followed by injection of a second kind of surfactant which has lower adsorption than the first surfactant used. Anionic and cationic surfactants are one possible combination for this application. These may form either a precipitate or a coacervate upon mixing. Phase boundaries for some specific systems of this type have been determined over a wide range of conditions and a model developed to describe this behavior. Another possibility is the use of nonionic surfactants, which may form coacervate under proper conditions. The adsorption behavior of mixtures of anionic and nonionic surfactants was measured to aid in modeling the chromatographic effects with these surfactants in the reservoir. Studies with sandpacks of different permeabilities in parallel configuration using mixtures of anionic and cationic surfactants have demonstrated the capability of this method to reduce flow rates through a more permeable sandpack more than that through a less permeable sandpack. 4 refs., 23 figs., 8 tabs.

  20. Surfactant adsorption kinetics in microfluidics

    PubMed Central

    Riechers, Birte; Maes, Florine; Akoury, Elias; Semin, Benoît; Gruner, Philipp; Baret, Jean-Christophe

    2016-01-01

    Emulsions are metastable dispersions. Their lifetimes are directly related to the dynamics of surfactants. We design a microfluidic method to measure the kinetics of adsorption of surfactants to the droplet interface, a key process involved in foaming, emulsification, and droplet coarsening. The method is based on the pH decay in the droplet as a direct measurement of the adsorption of a carboxylic acid surfactant to the interface. From the kinetic measurement of the bulk equilibration of the pH, we fully determine the adsorption process of the surfactant. The small droplet size and the convection during the droplet flow ensure that the transport of surfactant through the bulk is not limiting the kinetics of adsorption. To validate our measurements, we show that the adsorption process determines the timescale required to stabilize droplets against coalescence, and we show that the interface should be covered at more than 90% to prevent coalescence. We therefore quantitatively link the process of adsorption/desorption, the stabilization of emulsions, and the kinetics of solute partitioning—here through ion exchange—unraveling the timescales governing these processes. Our method can be further generalized to other surfactants, including nonionic surfactants, by making use of fluorophore–surfactant interactions. PMID:27688765

  1. Surfactant-assisted coal liquefaction

    NASA Technical Reports Server (NTRS)

    Hsu, G. C.

    1977-01-01

    Improved process of coal liquefaction utilizing nonaqueous surfactant has increased oil yield from 50 to about 80%. Asphaltene molecule formation of colloid particles is prevented by surfactant. Separated molecules present more surface area for hydrogenation reaction. Lower requirements for temperature, pressure, and hydrogen lead to reduction in capital and operation costs.

  2. Novel Approaches to Surfactant Administration

    PubMed Central

    Gupta, Samir; Donn, Steven M.

    2012-01-01

    Surfactant replacement therapy has been the mainstay of treatment for preterm infants with respiratory distress syndrome for more than twenty years. For the most part, surfactant is administered intratracheally, followed by mechanical ventilation. In recent years, the growing interest in noninvasive ventilation has led to novel approaches of administration. This paper will review these techniques and the associated clinical evidence. PMID:23243504

  3. ADSORPTION OF SURFACTANT ON CLAYS

    EPA Science Inventory

    Surfactants used to enhance remediation of soils by soil washing are often lost in the process. Neither the amount nor the cause of this loss is known. It is assumed that clays present in the soil are responsible for the loss of the surfactant. In this papere, adsorption prope...

  4. Surfactant monitoring by foam generation

    DOEpatents

    Mullen, Ken I.

    1997-01-01

    A device for monitoring the presence or absence of active surfactant or other surface active agents in a solution or flowing stream based on the formation of foam or bubbles is presented. The device detects the formation of foam with a light beam or conductivity measurement. The height or density of the foam can be correlated to the concentration of the active surfactant present.

  5. Microstructure of Mixed Surfactant Solutions by Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Naranjo, Edward

    1995-01-01

    Surfactant mixtures add a new dimension to the design of complex fluid microstructure. By combining different surfactants it is not only possible to modify aggregate morphology and control the macrascopic properties of colloidal dispersions but also to produce a variety of novel synergistic phases. Mixed systems produce new microstructures by altering the intermolecular and interaggregate forces in ways impossible for single component systems. In this dissertation, we report on the phase behavior and microstructure of several synthetic and biological surfactant mixtures as elucidated by freeze-fracture and cryo-transmission electron microscopy. We have discovered that stable, spontaneous unilamellar vesicles can be prepared from aqueous mixtures of commercially available single-tailed cationic and anionic surfactants. Vesicle stability is determined by the length and volume of the hydrocarbon chains of the "catanionic" pairs. Mixtures containing bulky or branched surfactant pairs (C _{16}/C_{12 -14}) in water produce defect-free fairly monodisperse equilibrium vesicles at high dilution. In contrast, mixtures of catanionic surfactants with highly asymmetric tails (C_{16}/C_8 ) form phases of porous vesicles, dilute lamellar L_{alpha}, and anomalous isotropic L_3 phases. Images of the microstructure by freeze-fracture microscopy show that the L_3 phase consists of multiconnected self-avoiding bilayers with saddle shaped curvature. The forces between bilayers of vesicle-forming cationic and anionic surfactant mixtures were also measured using the Surface Force Apparatus (SFA). We find that the vesicles are stabilized by a long range electrostatic repulsion at large separations (>20 A) and an additional salt-independent repulsive force below 20 A. The measured forces correlate very well with the ternary phase diagram and the vesicle microstructures observed by electron microscopy. In addition to studying ionic surfactants, we have also done original work with

  6. Selective adsorption of nonionic surfactant on hexagonal mesoporous silicates (HMSs) in the presence of ionic dyes.

    PubMed

    Punyapalakul, Patiparn; Takizawa, Satoshi

    2006-10-01

    Selective adsorption of alkylphenol polyethoxylates (APnEOs) from synthetic textile wastewater was investigated using hexagonal mesoporous silicates (HMSs). HMSs are synthetic silicate that have uniform mesopores, large surface areas and uniform surface functional groups. Five different types of HMSs were synthesized by surfactant-templating methods, and three of them were grafted with organic surface functional groups, i.e., n-octyldimethyl-, 3-aminopropyltriethoxy-, and 3-mercaptopropyl-groups. Titanium-substituted HMS was also made in the same way as HMS. Adsorption capacities and selectivities of these HMSs for APnEOs were investigated in batch adsorption experiments either in single-solute APnEO solutions or in mixed solutions with ionic dyes. Triton X-100 was used as a model APnEO and either Basic Yellow 1 or Acid Blue 45 was used as cationic or anionic dyes, respectively. All the HMSs except 3-aminopropyltriethoxy-grafted HMS had higher adsorption capacities of Triton X-100 than powdered activated carbon. HMS and Ti-HMS had the highest BET surface areas and mesopore volumes measured by the nitrogen adsorption method, and thereby the highest adsorption capacities for Triton X-100. Surface charge was the most important attractive force between HMSs and dyes. FT-IR spectra proved that hydrophilic HMSs adsorbed both Basic Yellow 1 and Acid Blue 45 by hydrogen bonding. Acid-base titration experiments revealed that all the HMSs except 3-aminopropyltriethoxy-grafted HMS were negatively charged at neutral pH, whereas PAC and 3-aminopropyltriethoxy-grafted HMS were positively charged. Due to negative surface charge, the anionic dye (Acid Blue 45) was not adsorbed on the four HMSs, which proves high selectivities of these HMSs for Triton X-100 over Acid Blue 45. On the contrary, a small amount of cationic dye (Basic Yellow 1) was adsorbed on all HMSs, but 3-aminopropyltriethoxy-grafted HMS showed the lowest adsorption capacity for Basic Yellow 1 due to positive

  7. Role of spacer length in interaction between novel gemini imidazolium surfactants and Rhizopus oryzae lipase.

    PubMed

    Adak, Sunita; Datta, Sougata; Bhattacharya, Santanu; Banerjee, Rintu

    2015-11-01

    An insight into the effects of new ionic liquid-type gemini imidazolium cationic surfactants on the structure and function of the lipases is of prime importance for their potential application. Changes in the activity, stability and structure of Rhizopus oryzae lipase in the presence of novel gemini surfactants, [C16-3-C16im]Br2 and [C16-12-C16im]Br2 were probed in the present study. Surfactant with shorter spacer length, [C16-3-C16im]Br2 was found to be better in improving the hydrolytic activity and thermal stability of the lipase. For both the surfactants, activation was concentration dependent. CD spectroscopy results showed a decrease in α-helix and an increase in β-sheet content in the presence of these surfactants. A higher structural change observed in presence of [C16-12-C16im]Br2 correlated with lower enzyme activity. Isothermal titration calorimetric studies showed the binding to be spontaneous in nature based on sequential two site binding model. The forces involved in binding were found to differ for the two surfactants proving that the spacer length is an important factor which governs the interaction. These surfactants could be used as promising components both in enzyme modification and media engineering for attaining the desired goals in biocatalytic reactions.

  8. Zeta potential of soils with surfactants and its relevance to electrokinetic remediation.

    PubMed

    Kaya, Abidin; Yukselen, Yeliz

    2005-04-11

    There are numerous studies on the application of electrokinetic decontamination technique to remediate heavy metal contaminated fine-grained soils. In recent studies, surfactants have been used to increase the efficiency of contaminant removal. However, there is limited data available on how physicochemical parameters such as zeta potential (zeta) of soils changes in the presence of surfactants. Understanding the zeta potential variations of soils with surfactant addition is important because it controls the direction and magnitude of electro-osmotic permeability, which plays important role on the efficiency of electrokinetic remediation. In this study, zeta potentials of kaolinite, montmorillonite and quartz powder with Li+, Ca+2, Cu+2, Pb+2 and Al+3 in the presence of anionic, cationic and non-ionic surfactants were determined. The results indicate that anionic surfactants produce negative zeta potentials. The other surfactants produce both positive and negative zeta potentials depending on soil type and ion present in the system. The results also indicate that the zeta potential of kaolinite and quartz powder with surfactants showed similar trends; however, the absolute magnitude of the zeta potential of quartz powder is higher than that of kaolinite. The zeta potential of montmorillonite commonly shows a different trend from those of kaolinite and quartz powder. Based on the test results, it is recommended that zeta potential of soils be determined before the electrokinetic decontamination in order to maximize the efficiency of the technique. PMID:15811672

  9. Surfactant-adsorption-induced initial depinning behavior in evaporating water and nanofluid sessile droplets.

    PubMed

    Zhong, Xin; Duan, Fei

    2015-05-19

    A surfactant-induced autophobic effect has been observed to initiate an intense depinning behavior at the initial stage of evaporation in both pure water and nanofluid sessile droplets. The cationic surfactant adsorbing to the negatively charged silicon wafer makes the solid surface more hydrophobic. The autophobing-induced depinning behavior, leading to an enlarged contact angle and a shortened base diameter, takes place only when the surfactant concentration is below its critical micelle concentration (cmc). The initial spreading degree right before the droplet retraction, the retracting velocity of the contact line, and the duration of the initial droplet retraction are shown to depend negatively on the surfactant concentration below the cmc. An unexpected enhancement in the initial depinning has been found in the nanofluid droplets, possibly resulting from the hydrophilic interplay between the graphite nanoparticle deposition and the surfactant molecules. Such promotion of the initial depinning due to the nanoparticle deposition makes the droplet retract even at a surfactant concentration higher than the cmc (1.5 cmc). The resulting deposition formed in the presence of the depinning behavior has great enhancement for coffee-ring formation as compared to the one free of surfactant, implying that the formation of a coffee ring does not require the pinning of the contact line during the entire drying process. PMID:25923721

  10. On-line surfactant monitoring

    SciTech Connect

    Mullen, K.I.; Neal, E.E.; Soran, P.D.; Smith, B.

    1995-04-01

    This group has developed a process to extract metal ions from dilute aqueous solutions. The process uses water soluble polymers to complex metal ions. The metal/polymer complex is concentrated by ultrafiltration and the metals are recovered by a pH adjustment that frees the metal ions. The metal ions pass through the ultrafiltration membrane and are recovered in a concentrated form suitable for reuse. Surfactants are present in one of the target waste streams. Surfactants foul the costly ultrafiltration membranes. It was necessary to remove the surfactants before processing the waste stream. This paper discusses an on-line device the authors fabricated to monitor the process stream to assure that all the surfactant had been removed. The device is inexpensive and sensitive to very low levels of surfactants.

  11. Surfactant loss control in chemical flooding spectroscopic and calorimetric study of adsorption and precipitation on reservoir minerals. Annual report, September 30, 1993--September 30, 1994

    SciTech Connect

    Somasundaran, P.

    1995-06-01

    The aim of this project is to elucidate the mechanisms underlying adsorption and surface precipitation of flooding surfactants on reservoir minerals. Effect of surfactant structure, surfactant combinations, other inorganic and polymeric species is being studied. A multi-pronged approach consisting of micro and nano spectroscopy, microcalorimetry, electrokinetics, surface tension and wettability is used to achieve the goals. The results of this study should help in controlling surfactant loss in chemical flooding and also in developing optimum structures and conditions for efficient chemical flooding processes. During the second year of this three year contract, adsorption/desorption of single surfactants and select surfactant mixtures on alumina and silica was studied. Surfactants studied include the anionic sodium dodecyl sulfate (SDS), cationic tetradecyl trimethyl ammonium chloride (TTAC), nonionic pentadecylethoxylated nonyl phenol (NP-15) and the nonionic octaethylene glycol n-dodecyl ether (C{sub 12}EO{sub 8}) of varying hydrocarbon chain length. The microstructure of the adsorbed layer in terms of micropolarity and aggregation numbers was probed using fluorescence spectroscopy. Changes of microstructure upon dilution (desorption) were also studied. Presence of the nonionic surfactant in the mixed aggregate led to shielding of the charge of the ionic surfactant which in-turn promoted aggregation but reduced electrostatic attraction between the charged surfactant and the mineral surface. Strong consequences of surfactant interactions in solution upon adsorption as well as correlations between monomer concentrations in mixtures and adsorption were revealed.

  12. Adsorption of zwitterionic surfactant on limestone measured with high-performance liquid chromatography: micelle-vesicle influence.

    PubMed

    Nieto-Alvarez, David Aaron; Zamudio-Rivera, Luis S; Luna-Rojero, Erick E; Rodríguez-Otamendi, Dinora I; Marín-León, Adlaí; Hernández-Altamirano, Raúl; Mena-Cervantes, Violeta Y; Chávez-Miyauchi, Tomás Eduardo

    2014-10-21

    Herein is presented a new methodology to determine the static adsorption of a zwitterionic surfactant on limestone in three different aqueous media [high-performance liquid chromatography (HPLC) water, seawater, and connate water] with the use of HPLC at room temperature and 70 °C. The results showed that, in both HPLC water and seawater, the surfactant adsorption followed a monolayer Langmuir tendency. In contrast, for connate water, the surfactant presented a new adsorption profile, characterized by two regions: (i) At surfactant concentrations below 1500 mg L(-1), an increase of adsorption is observed as the amount of divalent cations increases in the aqueous media. (ii) At surfactant concentrations above 1500 mg L(-1), the adsorption decreases because the equilibrium, monomer ⇆ micelle ⇆ vesicle, is shifted to the formation of vesicles, giving as a result a decrease in the concentration of monomers, thus reducing the interaction between the surfactant and the rock, and therefore, lower adsorption values were obtained. The behavior of the surfactant adsorption under different concentrations of divalent cations was well-described by the use of a new modified Langmuir model: (dΓ/dt)ads = k(ads)c(Γ∞ - Γ) - k(cmc)(c - c(cmc))(n)ΓH(c - c(cmc)). It was also observed that, as the temperature increases, the adsorption is reduced because of the exothermic nature of the adsorption processes. PMID:25254947

  13. Adsorption of zwitterionic surfactant on limestone measured with high-performance liquid chromatography: micelle-vesicle influence.

    PubMed

    Nieto-Alvarez, David Aaron; Zamudio-Rivera, Luis S; Luna-Rojero, Erick E; Rodríguez-Otamendi, Dinora I; Marín-León, Adlaí; Hernández-Altamirano, Raúl; Mena-Cervantes, Violeta Y; Chávez-Miyauchi, Tomás Eduardo

    2014-10-21

    Herein is presented a new methodology to determine the static adsorption of a zwitterionic surfactant on limestone in three different aqueous media [high-performance liquid chromatography (HPLC) water, seawater, and connate water] with the use of HPLC at room temperature and 70 °C. The results showed that, in both HPLC water and seawater, the surfactant adsorption followed a monolayer Langmuir tendency. In contrast, for connate water, the surfactant presented a new adsorption profile, characterized by two regions: (i) At surfactant concentrations below 1500 mg L(-1), an increase of adsorption is observed as the amount of divalent cations increases in the aqueous media. (ii) At surfactant concentrations above 1500 mg L(-1), the adsorption decreases because the equilibrium, monomer ⇆ micelle ⇆ vesicle, is shifted to the formation of vesicles, giving as a result a decrease in the concentration of monomers, thus reducing the interaction between the surfactant and the rock, and therefore, lower adsorption values were obtained. The behavior of the surfactant adsorption under different concentrations of divalent cations was well-described by the use of a new modified Langmuir model: (dΓ/dt)ads = k(ads)c(Γ∞ - Γ) - k(cmc)(c - c(cmc))(n)ΓH(c - c(cmc)). It was also observed that, as the temperature increases, the adsorption is reduced because of the exothermic nature of the adsorption processes.

  14. Innovation in surfactant therapy II: surfactant administration by aerosolization.

    PubMed

    Pillow, J Jane; Minocchieri, S

    2012-01-01

    Instilled bolus surfactant is the only approved surfactant treatment for neonatal respiratory distress syndrome. However, recent trends towards increased utilization of noninvasive respiratory support for preterm infants with surfactant deficiency have created a demand for a similarly noninvasive means of administering exogenous surfactant. Past approaches to surfactant nebulization met with varying success due to inefficient aerosol devices resulting in low intrapulmonary delivery doses of surfactant with variable clinical effectiveness. The recent development of vibrating membrane nebulizers, coupled with appropriate positioning of the interface device, indicates that efficient delivery of aerosolized surfactant is now a realistic goal in infants. Evidence of clinical effect despite low total administered dose in pilot studies, together with suggestions of enhanced homogeneity of pulmonary distribution indicate that this therapy may be applied in a cost-effective manner, with minimal patient handling and disruption. These studies need to be subjected to appropriately designed randomized controlled trials. Further work is also required to determine the optimum delivery route (mask, intranasal prong, nasopharyngeal or laryngeal), dosing amount and redosing interval.

  15. Factors Affecting the Design of Slow Release Formulations of Herbicides Based on Clay-Surfactant Systems. A Methodological Approach

    PubMed Central

    Galán-Jiménez, María del Carmen; Mishael, Yael-Golda; Nir, Shlomo; Morillo, Esmeralda; Undabeytia, Tomás

    2013-01-01

    A search for clay-surfactant based formulations with high percentage of the active ingredient, which can yield slow release of active molecules is described. The active ingredients were the herbicides metribuzin (MZ), mesotrione (MS) and flurtamone (FL), whose solubilities were examined in the presence of four commercial surfactants; (i) neutral: two berols (B048, B266) and an alkylpolyglucoside (AG6202); (ii) cationic: an ethoxylated amine (ET/15). Significant percent of active ingredient (a.i.) in the clay/surfactant/herbicide formulations could be achieved only when most of the surfactant was added as micelles. MZ and FL were well solubilized by berols, whereas MS by ET/15. Sorption of surfactants on the clay mineral sepiolite occurred mostly by sorption of micelles, and the loadings exceeded the CEC. Higher loadings were determined for B266 and ET/15. The sorption of surfactants was modeled by using the Langmuir-Scatchard equation which permitted the determination of binding coefficients that could be used for further predictions of the sorbed amounts of surfactants under a wide range of clay/surfactant ratios. A possibility was tested of designing clay-surfactant based formulations of certain herbicides by assuming the same ratio between herbicides and surfactants in the formulations as for herbicides incorporated in micelles in solution. Calculations indicated that satisfactory FL formulations could not be synthesized. The experimental fractions of herbicides in the formulations were in agreement with the predicted ones for MS and MZ. The validity of this approach was confirmed in in vitro release tests that showed a slowing down of the release of a.i. from the designed formulations relative to the technical products. Soil dissipation studies with MS formulations also showed improved bioactivity of the clay-surfactant formulation relative to the commercial one. This methodological approach can be extended to other clay-surfactant systems for encapsulation and

  16. Factors affecting the design of slow release formulations of herbicides based on clay-surfactant systems. A methodological approach.

    PubMed

    Galán-Jiménez, María Del Carmen; Mishael, Yael-Golda; Nir, Shlomo; Morillo, Esmeralda; Undabeytia, Tomás

    2013-01-01

    A search for clay-surfactant based formulations with high percentage of the active ingredient, which can yield slow release of active molecules is described. The active ingredients were the herbicides metribuzin (MZ), mesotrione (MS) and flurtamone (FL), whose solubilities were examined in the presence of four commercial surfactants; (i) neutral: two berols (B048, B266) and an alkylpolyglucoside (AG6202); (ii) cationic: an ethoxylated amine (ET/15). Significant percent of active ingredient (a.i.) in the clay/surfactant/herbicide formulations could be achieved only when most of the surfactant was added as micelles. MZ and FL were well solubilized by berols, whereas MS by ET/15. Sorption of surfactants on the clay mineral sepiolite occurred mostly by sorption of micelles, and the loadings exceeded the CEC. Higher loadings were determined for B266 and ET/15. The sorption of surfactants was modeled by using the Langmuir-Scatchard equation which permitted the determination of binding coefficients that could be used for further predictions of the sorbed amounts of surfactants under a wide range of clay/surfactant ratios. A possibility was tested of designing clay-surfactant based formulations of certain herbicides by assuming the same ratio between herbicides and surfactants in the formulations as for herbicides incorporated in micelles in solution. Calculations indicated that satisfactory FL formulations could not be synthesized. The experimental fractions of herbicides in the formulations were in agreement with the predicted ones for MS and MZ. The validity of this approach was confirmed in in vitro release tests that showed a slowing down of the release of a.i. from the designed formulations relative to the technical products. Soil dissipation studies with MS formulations also showed improved bioactivity of the clay-surfactant formulation relative to the commercial one. This methodological approach can be extended to other clay-surfactant systems for encapsulation and

  17. An Olfactory Indicator for Acid-Base Titrations.

    ERIC Educational Resources Information Center

    Flair, Mark N.; Setzer, William N.

    1990-01-01

    The use of an olfactory acid-base indicator in titrations for visually impaired students is discussed. Potential olfactory indicators include eugenol, thymol, vanillin, and thiophenol. Titrations performed with each indicator with eugenol proved to be successful. (KR)

  18. Biologist's Toolbox. Acid-base Balance: An Educational Computer Game.

    ERIC Educational Resources Information Center

    Boyle, Joseph, III; Robinson, Gloria

    1987-01-01

    Describes a microcomputer program that can be used in teaching the basic physiological aspects of acid-base (AB) balance. Explains how its game format and graphic approach can be applied in diagnostic and therapeutic exercises. (ML)

  19. The Bronsted-Lowery Acid-Base Concept.

    ERIC Educational Resources Information Center

    Kauffman, George B.

    1988-01-01

    Gives the background history of the simultaneous discovery of acid-base relationships by Johannes Bronsted and Thomas Lowry. Provides a brief biographical sketch of each. Discusses their concept of acids and bases in some detail. (CW)

  20. Surfactant and process for enhanced oil recovery

    SciTech Connect

    Stapp, P. R.

    1985-03-12

    A novel surfactant is formed by reacting maleic anhydride with a polynuclear aromatic compound having a molecular weight of at least 155. A novel surfactant system useful in enhanced oil recovery containing the above surfactant is also provided. In addition, an improved process for the enhanced recovery of oil is provided utilizing the novel surfactant system.

  1. Critical micelle concentration values for different surfactants measured with solid-phase microextraction fibers.

    PubMed

    Haftka, Joris J-H; Scherpenisse, Peter; Oetter, Günter; Hodges, Geoff; Eadsforth, Charles V; Kotthoff, Matthias; Hermens, Joop L M

    2016-09-01

    The amphiphilic nature of surfactants drives the formation of micelles at the critical micelle concentration (CMC). Solid-phase microextraction (SPME) fibers were used in the present study to measure CMC values of 12 nonionic, anionic, cationic, and zwitterionic surfactants. The SPME-derived CMC values were compared to values determined using a traditional surface tension method. At the CMC of a surfactant, a break in the relationship between the concentration in SPME fibers and the concentration in water is observed. The CMC values determined with SPME fibers deviated by less than a factor of 3 from values determined with a surface tension method for 7 out of 12 compounds. In addition, the fiber-water sorption isotherms gave information about the sorption mechanism to polyacrylate-coated SPME fibers. A limitation of the SPME method is that CMCs for very hydrophobic cationic surfactants cannot be determined when the cation exchange capacity of the SPME fibers is lower than the CMC value. The advantage of the SPME method over other methods is that CMC values of individual compounds in a mixture can be determined with this method. However, CMC values may be affected by the presence of compounds with other chain lengths in the mixture because of possible mixed micelle formation. Environ Toxicol Chem 2016;35:2173-2181. © 2016 SETAC. PMID:26873883

  2. Interactions between kappa-carrageenan and some surfactants in the bulk solution and at the surface of alumina.

    PubMed

    Grządka, E

    2015-06-01

    The interactions between surfactants (SDS, CTAB, TX-100 or their equimolar mixtures) and kappa-carrageenan (Carr) in the bulk solution and at the surface of alumina were determined using the surface tension and the spectrophotometric adsorption measurements. The obtained results show that Carr has the ability to create the multilayer complexes with CTAB, TX-100 and the equimolar mixtures of surfactants (CTAB/TX-100), but does not interact with SDS. The created complexes are electrostatic (with CTAB) or they are of different mechanisms such as the hydrogen bonding or the acid-base interactions (with TX-100). The electrokinetic measurements (the surface charge density and the zeta potential) allow to analyze the structure of the adsorption layer: polymer/surfactant/metal oxide. It turned out that the macromolecules of Carr are directly bonded to the surface whereas the surfactants are present in the upper parts of the electrical double layer.

  3. Acid-base homeostasis in the human system

    NASA Technical Reports Server (NTRS)

    White, R. J.

    1974-01-01

    Acid-base regulation is a cooperative phenomena in vivo with body fluids, extracellular and intracellular buffers, lungs, and kidneys all playing important roles. The present account is much too brief to be considered a review of present knowledge of these regulatory systems, and should be viewed, instead, as a guide to the elements necessary to construct a simple model of the mutual interactions of the acid-base regulatory systems of the body.

  4. Effects of radiation and temperature on iodide sorption by surfactant-modified bentonite.

    PubMed

    Choung, Sungwook; Kim, Minkyung; Yang, Jung-Seok; Kim, Min-Gyu; Um, Wooyong

    2014-08-19

    Bentonite, which is used as an engineered barrier in geological repositories, is ineffective for sorbing anionic radionuclides because of its negatively charged surface. This study modified raw bentonite using a cationic surfactant (i.e., hexadecyltrimethylammonium [HDTMA]-Br) to improve its sorption capability for radioactive iodide. The effects of temperature and radiation on the iodide sorption of surfactant-modified bentonite (SMB) were also evaluated under alkaline pH condition similar to that found in repository environments. Different amounts of surfactant, equivalent to the 50, 100, and 200% cation-exchange capacity of the bentonite, were used to produce the HDTMA-SMB for iodide sorption. The sorption reaction of the SMB with iodide reached equilibrium rapidly within 10 min regardless of temperature and radiation conditions. The rate of iodide sorption increased as the amount of the added surfactant was increased and nonlinear sorption behavior was exhibited. However, high temperature and γ-irradiation ((60)Co) resulted in significantly (∼2-10 times) lower iodide Kd values for the SMB. The results of FTIR, NMR, and XANES spectroscopy analysis suggested that the decrease in iodide sorption may be caused by weakened physical electrostatic force between the HDTMA and iodide, and by the surfactant becoming detached from the SMB during the heating and irradiation processes.

  5. Effects of Radiation and Temperature on Iodide Sorption by Surfactant-Modified Bentonite

    SciTech Connect

    Choung, Sungwook; Kim, Min Kyung; Yang, Jungseok; Kim, Min-Gyu; Um, Wooyong

    2014-08-04

    Bentonite, which is used as an engineered barrier in geological repositories, is ineffective for sorbing anionic radionuclides because of its negatively charged surface. This study modified raw bentonite using a cationic surfactant (i.e., hexadecyltrimethylammonium [HDTMA]-Br) to improve its sorption capability for radioactive iodide. The effects of temperature and radiation on the iodide sorption of surfactant-modified bentonite (SMB) were evaluated under alkaline pH condition similar to that found in repository environments. Different amounts of surfactant, equivalent to the 50, 100, and 200% cation-exchange capacity of the bentonite, were used to produce the HDTMA-SMB for iodide sorption. The sorption reaction of the SMB with iodide reached equilibrium rapidly within 10 min regardless of temperature and radiation conditions. The rate of iodide sorption increased as the amount of the added surfactant was increased and nonlinear sorption behavior was exhibited. However, high temperature and γ-irradiation (60Co) resulted in significantly (~2–10 times) lower iodide Kd values for the SMB. The results of Fourier transform infrared spectroscopy analysis suggested that the decrease in iodide sorption may be caused by weakened physical electrostatic force between the HDTMA and iodide, and by the surfactant becoming detached from the SMB during the heating and irradiation processes.

  6. A new model for assessing the damaging effects of soaps and surfactants on human stratum corneum.

    PubMed

    Shukuwa, T; Kligman, A M; Stoudemayer, T J

    1997-01-01

    To elucidate the damage to the horny layers of human skin produced by surfactants and soaps, we evaluated the cytological alterations of corneocytes using an in vitro assay. Suction blisters, 8 mm in diameter, were raised on the forearms of young adult Caucasoids. The roofs were cut off and the viable epidermis was removed. The discs of stratum corneum were then agitated for up to 6 h at 60 degrees C in 1% solution of five soap bars of differing irritancy. Additionally, individual examples of anionic, cationic and nonionic surfactants were similarly evaluated. Measurements of corneocytes included: (1) the number released with time (disaggregation), (2) size (swelling) and (3) morphologic degradation. The effects of the cationic and non-ionic surfactants did not differ significantly from those of distilled water. The anionic surfactant caused more release and less swelling and morphological change. The test soaps had vastly different effects on the structural integrity of the stratum corneum. The harsher ones caused greater disaggregation, more swelling and greater morphologic deterioration of corneocytes, whereas the milder ones had less marked effects on these parameters. This model would be a useful screening technique for formulating milder soaps and might also provide insights into the complex modes of action of surfactants on the stratum corneum. PMID:9059673

  7. Surfactant waterflooding enhanced oil recovery process

    SciTech Connect

    Schievelbein, V.H.

    1984-07-17

    Disclosed is a surfactant waterflooding enhanced oil recovery process and surfactant fluid suitable for use in an enhanced oil recovery process which accomplishes an increase in the amount of oil recovered over prior art methods. The surfactant fluid contains an alkylpolyalkoxy sulfate or alkylarylpolyalkoxy sulfate, or an alkylpolyalkoxyalkylene sulfonate or alkylarylpolyalkoxyalkylene sulfonate, either alone or in combination with an organic sulfonate anionic surfactant, such as petroleum sulfonate. The optimum average degree of ethoxylation of the alkoxy sulfate or alkoxy sulfonate surfactant is identified, and the surfactant fluid is formulated with a mixture of ethoxylated and sulfated or ethoxylated and sulfonated surfactants, having a broad even range of degree of ethoxylation.

  8. Carbonic anhydrase and acid-base regulation in fish.

    PubMed

    Gilmour, K M; Perry, S F

    2009-06-01

    Carbonic anhydrase (CA) is the zinc metalloenzyme that catalyses the reversible reactions of CO(2) with water. CA plays a crucial role in systemic acid-base regulation in fish by providing acid-base equivalents for exchange with the environment. Unlike air-breathing vertebrates, which frequently utilize alterations of breathing (respiratory compensation) to regulate acid-base status, acid-base balance in fish relies almost entirely upon the direct exchange of acid-base equivalents with the environment (metabolic compensation). The gill is the critical site of metabolic compensation, with the kidney playing a supporting role. At the gill, cytosolic CA catalyses the hydration of CO(2) to H(+) and HCO(3)(-) for export to the water. In the kidney, cytosolic and membrane-bound CA isoforms have been implicated in HCO(3)(-) reabsorption and urine acidification. In this review, the CA isoforms that have been identified to date in fish will be discussed together with their tissue localizations and roles in systemic acid-base regulation.

  9. Pulmonary surfactant for neonatal respiratory disorders.

    PubMed

    Merrill, Jeffrey D; Ballard, Roberta A

    2003-04-01

    Surfactant therapy has revolutionized neonatal care and is used routinely for preterm infants with respiratory distress syndrome. Recent investigation has further elucidated the function of surfactant-associated proteins and their contribution toward surfactant and lung immune defense functions. As the field of neonatology moves away from intubation and mechanical ventilation of preterm infants at birth toward more aggressive use of nasal continuous positive airway pressure, the optimal timing of exogenous surfactant therapy remains unclear. Evidence suggests that preterm neonates with bronchopulmonary dysplasia and prolonged mechanical ventilation also experience surfactant dysfunction; however, exogenous surfactant therapy beyond the first week of life has not been well studied. Surfactant replacement therapy has been studied for use in other respiratory disorders, including meconium aspiration syndrome and pneumonia. Commercial surfactant preparations currently available are not optimal, given the variability of surfactant protein content and their susceptibility to inhibition. Further progress in the treatment of neonatal respiratory disorders may include the development of "designer" surfactant preparations.

  10. Structural Studies of Protein-Surfactant Complexes

    SciTech Connect

    Chodankar, S. N.; Aswal, V. K.; Wagh, A. G.

    2008-03-17

    The structure of protein-surfactant complexes of two proteins bovine serum albumin (BSA) and lysozyme in presence of anionic surfactant sodium dodecyl sulfate (SDS) has been studied using small-angle neutron scattering (SANS). It is observed that these two proteins form different complex structures with the surfactant. While BSA protein undergoes unfolding on addition of surfactant, lysozyme does not show any unfolding even up to very high surfactant concentrations. The unfolding of BSA protein is caused by micelle-like aggregation of surfactant molecules in the complex. On the other hand, for lysozyme protein there is only binding of individual surfactant molecules to protein. Lysozyme in presence of higher surfactant concentrations has protein-surfactant complex structure coexisting with pure surfactant micelles.

  11. Pulmonary surfactant for neonatal respiratory disorders.

    PubMed

    Merrill, Jeffrey D; Ballard, Roberta A

    2003-04-01

    Surfactant therapy has revolutionized neonatal care and is used routinely for preterm infants with respiratory distress syndrome. Recent investigation has further elucidated the function of surfactant-associated proteins and their contribution toward surfactant and lung immune defense functions. As the field of neonatology moves away from intubation and mechanical ventilation of preterm infants at birth toward more aggressive use of nasal continuous positive airway pressure, the optimal timing of exogenous surfactant therapy remains unclear. Evidence suggests that preterm neonates with bronchopulmonary dysplasia and prolonged mechanical ventilation also experience surfactant dysfunction; however, exogenous surfactant therapy beyond the first week of life has not been well studied. Surfactant replacement therapy has been studied for use in other respiratory disorders, including meconium aspiration syndrome and pneumonia. Commercial surfactant preparations currently available are not optimal, given the variability of surfactant protein content and their susceptibility to inhibition. Further progress in the treatment of neonatal respiratory disorders may include the development of "designer" surfactant preparations. PMID:12640270

  12. Quantitative methods for evaluating optical and frictional properties of cationic polymers.

    PubMed

    Wu, W; Alkema, J; Shay, G D; Basset, D R

    2001-01-01

    This paper presents three quantitative methods to examine gloss, opacity, and friction of cationic polymers. The adsorption of cationic polymers onto hair and skin can be regarded as a thin film coating. Therefore, optical and frictional properties of polymer films are of significant relevance to the applications of cationic polymers in hair care products. Such properties reflect the desirable hair condition attributes consumers seek in shampoo and conditioner products. Using these test methods, polyquaternium-10 and cationic guar samples of varying molecular weight and cationic substitution were compared. The effect of an anionic surfactant, sodium dodecyl sulfate (SDS), on polymer film properties was also investigated. Neat guar hydroxypropyl trimonium chloride imparts less friction than polyquaternium-10 but dulls the substrate employed in this study. The optical data show that polyquaternium-10 provides greater film clarity and gloss than cationic guars. In the presence of SDS, polyquaternium-10 also displays similar or lower friction than cationic guar. The comparative optical and frictional results are in good agreement with the visual assessment of the cationic polymer films. These results clearly demonstrate that polyquaternium-10 exhibits superior film properties in the forms of both neat polymer and polymer/surfactant complex. In addition, microscopic techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM) provide powerful explanations for the differences noted between the two popular classes of cationic polymers. The test methods described in this paper can be utilized to differentiate the upper performance potential of cationic polymers. These objective and standardized test methods derived from the coatings industry are not affected by the variability of hair or the formulation complexity of end products. They can be useful tools in the product development process in quickly screening the relative performance of

  13. Clinical utility of anion gap in deciphering acid-base disorders.

    PubMed

    Reddy, P; Mooradian, A D

    2009-10-01

    The anion gap (AG) measurement is a very useful tool in the evaluation of patients with acid-base disorders. Once metabolic acidosis is identified, AG will provide the important first step in the differential diagnosis of disorders that either increase the AG and those that leave the AG unchanged. Delta gap is the comparison between change (delta) in the AG and the change (delta) in bicarbonate (HCO(3)(-)). Delta ratio, defined as delta AG:delta HCO(3)(-) is usually 1:1 in patients with an uncomplicated high AG acidosis. A value below 1:1 suggests a combined high and normal AG acidosis. A value above 2:1 suggests a combined metabolic alkalosis and a high AG acidosis. Urine AG (unmeasured anions-unmeasured cations) is an indirect estimate of the urine NH(4)(+) excretion. It is typically negative in patients with normal AG metabolic acidosis secondary to diarrhoea. Utilisation of AG calculations helps clinicians in identifying and treating acid-base disorders.

  14. A Prebiotic Chemistry Experiment on the Adsorption of Nucleic Acids Bases onto a Natural Zeolite

    NASA Astrophysics Data System (ADS)

    Anizelli, Pedro R.; Baú, João Paulo T.; Gomes, Frederico P.; da Costa, Antonio Carlos S.; Carneiro, Cristine E. A.; Zaia, Cássia Thaïs B. V.; Zaia, Dimas A. M.

    2015-09-01

    There are currently few mechanisms that can explain how nucleic acid bases were synthesized, concentrated from dilute solutions, and/or protected against degradation by UV radiation or hydrolysis on the prebiotic Earth. A natural zeolite exhibited the potential to adsorb adenine, cytosine, thymine, and uracil over a range of pH, with greater adsorption of adenine and cytosine at acidic pH. Adsorption of all nucleic acid bases was decreased in artificial seawater compared to water, likely due to cation complexation. Furthermore, adsorption of adenine appeared to protect natural zeolite from thermal degradation. The C=O groups from thymine, cytosine and uracil appeared to assist the dissolution of the mineral while the NH2 group from adenine had no effect. As shown by FT-IR spectroscopy, adenine interacted with a natural zeolite through the NH2 group, and cytosine through the C=O group. A pseudo-second-order model best described the kinetics of adenine adsorption, which occurred faster in artificial seawaters.

  15. A Prebiotic Chemistry Experiment on the Adsorption of Nucleic Acids Bases onto a Natural Zeolite.

    PubMed

    Anizelli, Pedro R; Baú, João Paulo T; Gomes, Frederico P; da Costa, Antonio Carlos S; Carneiro, Cristine E A; Zaia, Cássia Thaïs B V; Zaia, Dimas A M

    2015-09-01

    There are currently few mechanisms that can explain how nucleic acid bases were synthesized, concentrated from dilute solutions, and/or protected against degradation by UV radiation or hydrolysis on the prebiotic Earth. A natural zeolite exhibited the potential to adsorb adenine, cytosine, thymine, and uracil over a range of pH, with greater adsorption of adenine and cytosine at acidic pH. Adsorption of all nucleic acid bases was decreased in artificial seawater compared to water, likely due to cation complexation. Furthermore, adsorption of adenine appeared to protect natural zeolite from thermal degradation. The C=O groups from thymine, cytosine and uracil appeared to assist the dissolution of the mineral while the NH2 group from adenine had no effect. As shown by FT-IR spectroscopy, adenine interacted with a natural zeolite through the NH2 group, and cytosine through the C=O group. A pseudo-second-order model best described the kinetics of adenine adsorption, which occurred faster in artificial seawaters. PMID:25754589

  16. A Prebiotic Chemistry Experiment on the Adsorption of Nucleic Acids Bases onto a Natural Zeolite.

    PubMed

    Anizelli, Pedro R; Baú, João Paulo T; Gomes, Frederico P; da Costa, Antonio Carlos S; Carneiro, Cristine E A; Zaia, Cássia Thaïs B V; Zaia, Dimas A M

    2015-09-01

    There are currently few mechanisms that can explain how nucleic acid bases were synthesized, concentrated from dilute solutions, and/or protected against degradation by UV radiation or hydrolysis on the prebiotic Earth. A natural zeolite exhibited the potential to adsorb adenine, cytosine, thymine, and uracil over a range of pH, with greater adsorption of adenine and cytosine at acidic pH. Adsorption of all nucleic acid bases was decreased in artificial seawater compared to water, likely due to cation complexation. Furthermore, adsorption of adenine appeared to protect natural zeolite from thermal degradation. The C=O groups from thymine, cytosine and uracil appeared to assist the dissolution of the mineral while the NH2 group from adenine had no effect. As shown by FT-IR spectroscopy, adenine interacted with a natural zeolite through the NH2 group, and cytosine through the C=O group. A pseudo-second-order model best described the kinetics of adenine adsorption, which occurred faster in artificial seawaters.

  17. The interaction of photo-responsive surfactants with biological macromolecules

    NASA Astrophysics Data System (ADS)

    Mazwi, Khiza L.

    The interaction of photo-responsive surfactants with proteins has been considered as a means to exert reversible control over a number of aspects of protein structure and function. The azobenzene trimethylammonium bromide (azoTAB) family of cationic surfactants undergo a photo-reversible cis to trans isomerization upon exposure to light of the appropriate wavelength. The trans form of the molecule has a lower dipole moment across its azo linkage, and is more hydrophobic than the cis isomer. This results in a higher binding affinity with proteins for the trans isomer, inducing a greater degree of unfolding of tertiary and secondary structures. The surfactant has been applied to the study of the amyloid fibrillation pathway in insulin, in which the protein self-associates into long, insoluble, rod-like structures. The fibrillation rate in insulin is enhanced in the presence of the trans- isomer while the formation of fibrils is largely inhibited in the presence of the cis- isomer, where amorphous aggregates are observed instead. Additionally early fibrillar species formed in the trans-azoTAB assays exhibit a greater tendency to lateral aggregation than do structures in the pure protein, resulting in a more truncated, bundled final aggregate morphology. Use of the surfactants as a means to control protein quaternary solution structure has also been explored in the subunit dissociation of tetrameric catalase. In the presence of azoTAB surfactants, catalase dissociates first into a super-active dimer, then at higher concentrations into an aggregation prone monomer. Finally, the structural changes associated with azoTAB-induced unfolding of the two domain protein papain are tracked. The denaturation pathway involves a progressive loss in secondary structure with increasing azoTAB concentration, along with a relaxation of the compact tertiary structure, and a spatial separation of the two domains. A number of complementary experimental techniques are combined to determine

  18. Effect of surfactants on the performance of tubular and spherical micromotors – a comparative study†

    PubMed Central

    Sanchez, Samuel; Chokmaviroj, Sarocha; Ruiz-Molina, Daniel; Baeza, Alejandro; Schmidt, Oliver G.

    2014-01-01

    The development of artificial micromotors is one of the greatest challenges of modern nanotechnology. Even though many kinds of motors have been published in recent times, systematic studies on the influence of components of the fuel solution are widely missing. Therefore, the autonomous movement of Pt-microtubes and Pt-covered silica particles is comparatively observed in the presence and absence of surfactants in the medium. One representative of each of the three main surfactant classes – anionic (sodium dodecyl sulfate, SDS), cationic (benzalkonium chloride, BACl) and non-ionic (Triton X) – has been chosen and studied. PMID:25364501

  19. Demulsification of emulsions produced from surfactant recovery operations and recovery of surfactants therefrom

    SciTech Connect

    Allison, J.B.; Kudchadker, M.V.; Whittington, L.E.

    1981-07-07

    Treatment of emulsions of oil and water produced from surfactant recovery operations whereby the produced emulsions containing surfactants are demulsified and the surfactants are recovered in the water phase.

  20. Surfactants as Microbicides and Contraceptive Agents: A Systematic In Vitro Study

    PubMed Central

    Vieira, Otilia V.; Oberdoerfer, Daniel; Baptista, Marta; Santos, Manuel A. S.; Almeida, Luis; Ramalho-Santos, João; Vaz, Winchil L. C.

    2008-01-01

    Background The urgent need for cheap and easy-to-use protection against both unwanted pregnancies and sexually transmitted diseases has stimulated considerable interest in the use of surfactants as microbicides, anti-viral, and contraceptive agents in recent years. In the present study we report a systematic in vitro evaluation of the microbicidal, anti-viral and contraceptive potential of cationic, anionic, zwitterionic, and non-ionic surfactants. Methodology/Principal Findings Toxicity was evaluated in mammalian columnar epithelial (MDCK) cells, human sperm cells, Candida albicans, Escherichia coli, Pseudomonas aeruginosa, Neisseria gonorrhoeae, Streptococcus agalactiae and Enterococcus faecalis. The inhibition of adenovirus and lentivirus infection of MDCK cells was also tested. A homologous series of cationic surfactants, alkyl-N,N,N-trimethylammonium bromides (CnTAB), with varying alkyl chains were shown to be bactericidal and fungicidal at doses that were related to the surfactant critical micelle concentrations (CMC), all of them at concentrations significantly below the CMC. In general, bacteria were more susceptible to this surfactant group than C. albicans and this organism, in turn, was more susceptible than MDCK cells. This suggests that the CnTAB may be useful as vaginal disinfectants only in so far as bacterial and fungal infections are concerned. None of the surfactants examined, including those that have been used in pre-clinical studies, showed inhibition of adenovirus or lentivirus infection of MDCK cells or spermicidal activity at doses that were sub-toxic to MDCK cells. Conclusions/Significance The results of this study lead us to propose that systematic analysis of surfactant toxicity, such as we report in the present work, be made a mandatory pre-condition for the use of these substances in pre-clinical animal and/or human studies. PMID:18682796

  1. Interactions between polymers and surfactants

    SciTech Connect

    de Gennes, P.G. )

    1990-11-01

    A surfactant film (at the water/air interface, or in a bilayer) is exposed to a solution of a neutral, flexible, polymer. Depending on the interactions, and on the Langmuir pressure II of the pure surfactant film, the authors expected to find three types of behavior: (I) the polymer does not absorb; (II) the polymer absorbs and mixes with the surfactant; (III) the polymer absorbs but segregates from the surfactant. Their interest here is in case II. They predict that (a) bilayers become rigid; (b) bilayers, exposed to polymer on one side only, tend to bend strongly; (c) the surface viscosity of monolayers or bilayers is considerably increased; soap films or foams, which usually drain by turbulent (two-dimensional) flows, may be stabilized in case II.

  2. Stabilization of diketo tautomer of curcumin by premicellar anionic surfactants: UV-Visible, fluorescence, tensiometric and TD-DFT evidences

    NASA Astrophysics Data System (ADS)

    Dutta, Anisha; Boruah, Bornali; Manna, Arun K.; Gohain, Biren; Saikia, Palash M.; Dutta, Robin K.

    2013-03-01

    A newly observed UV band of aqueous curcumin, a biologically important molecule, in presence of anionic surfactants, viz., sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and sodium dodecylsulfonate (SDSN) in buffered aqueous solutions has been studied experimentally and theoretically. The 425 nm absorption band of curcumin disappears and a new UV-band is observed at 355 nm on addition of the surfactants in the submicellar concentration range which is reversed as the surfactant concentration approaches the critical micelle concentration (CMC). The observed spectral absorption, fluorescence intensity and surface tension behavior, under optimal experimental conditions of submicellar concentration ranges of the surfactants in the pH range of 2.00-7.00, indicate that the new band is due to the β-diketo tautomer of curcumin stabilized by interactions between curcumin and the anionic surfactants. The stabilization of the diketo tautomer by submicellar anionic surfactants described here as well as by submicellar cationic surfactant, reported recently, is unique as this is the only such behavior observed in presence of submicellar surfactants of both charge types. The experimental results are in good agreement with the theoretical calculations using ab initio density functional theory combined with time dependent density functional theory (TD-DFT) calculations.

  3. Effects of surfactants and electrolytes on chemical oscillation at a water/nitrobenzene interface investigated by quasi-elastic laser scattering method.

    PubMed

    Toyota, Taro; Uchiyama, Koyo; Kimura, Takahiro; Nomoto, Tomonori; Fujinami, Masanori

    2013-01-01

    We used a time-resolved interfacial tension measurement method with quasi-elastic laser scattering to investigate the effects of electrolytes and various surfactants on the nonlinear dynamics of the chemical oscillation that occurred at a water/nitrobenzene interface when a surfactant was added to the interface through a capillary. For both cationic and anionic surfactants, an electrolyte in the water phase was required for slow desorption of the surfactant from the interface. In the absence of an electrolyte, repulsion between the polar head groups of the ionic surfactants hindered adsorption of the surfactant molecules at the interface, resulting in their rapid desorption. In contrast, the presence of an electrolyte induced adsorption of the surfactant ions by screening their charged polar heads. Zwitterionic and nonionic surfactants were also examined and we deduced that the salting out effect of the surfactant produced by the presence of an electrolyte results in strongly attractive interactions between the surfactant molecules and the water/nitrobenzene interface.

  4. Gemini Surfactants Based on Bis-Imidazolium Alkoxy Derivatives as Effective Agents for Delivery of Nucleic Acids: A Structural and Spectroscopic Study

    PubMed Central

    Pietralik, Zuzanna; Kołodziejska, Żaneta; Weiss, Marek; Kozak, Maciej

    2015-01-01

    The success rate of gene therapy depends on the efficient transfection of genetic material into cells. The golden mean between harmlessness and high effectiveness can be provided by synthetic lipid-like molecules that are similar to the components of biological membranes. Cationic gemini surfactants are one such moiety and because of their favourable physicochemical properties (double positive electric charge, reduced toxicity, low values of critical micelle concentration), they show great potential as delivery system components for genetic material in gene therapy. The aim of this study was to investigate the process of the complexation of cationic gemini surfactants with nucleic acids: double-stranded DNA of different sizes (21 bp, ~185 bp, ~20 kbp) and siRNA (21 bp). The tested series of dicationic surfactants consists of bis-imidazolium quaternary salts with varying lengths of hydrophobic side chains (m = 5, 6, 7, 8, 9, 11, 12, 14, 16). On the basis of the data obtained by circular dichroism spectroscopy and electrophoresis, we concluded that the studied gemini surfactants with long side chains effectively bind nucleic acids at low concentrations, which leads to the formation of stable lipoplexes. Images obtained by atomic force microscopy also confirmed the formation of vesicular structures, i.e., complexes between DNA and surfactants. The cytotoxicity of selected surfactants was also tested on HeLa cells. The surfactant toxicity significantly depends on surfactant geometry (the length of hydrophobic chain). PMID:26641889

  5. Gemini Surfactants Based on Bis-Imidazolium Alkoxy Derivatives as Effective Agents for Delivery of Nucleic Acids: A Structural and Spectroscopic Study.

    PubMed

    Pietralik, Zuzanna; Kołodziejska, Żaneta; Weiss, Marek; Kozak, Maciej

    2015-01-01

    The success rate of gene therapy depends on the efficient transfection of genetic material into cells. The golden mean between harmlessness and high effectiveness can be provided by synthetic lipid-like molecules that are similar to the components of biological membranes. Cationic gemini surfactants are one such moiety and because of their favourable physicochemical properties (double positive electric charge, reduced toxicity, low values of critical micelle concentration), they show great potential as delivery system components for genetic material in gene therapy. The aim of this study was to investigate the process of the complexation of cationic gemini surfactants with nucleic acids: double-stranded DNA of different sizes (21 bp, ~185 bp, ~20 kbp) and siRNA (21 bp). The tested series of dicationic surfactants consists of bis-imidazolium quaternary salts with varying lengths of hydrophobic side chains (m = 5, 6, 7, 8, 9, 11, 12, 14, 16). On the basis of the data obtained by circular dichroism spectroscopy and electrophoresis, we concluded that the studied gemini surfactants with long side chains effectively bind nucleic acids at low concentrations, which leads to the formation of stable lipoplexes. Images obtained by atomic force microscopy also confirmed the formation of vesicular structures, i.e., complexes between DNA and surfactants. The cytotoxicity of selected surfactants was also tested on HeLa cells. The surfactant toxicity significantly depends on surfactant geometry (the length of hydrophobic chain).

  6. Gemini Surfactants Based on Bis-Imidazolium Alkoxy Derivatives as Effective Agents for Delivery of Nucleic Acids: A Structural and Spectroscopic Study.

    PubMed

    Pietralik, Zuzanna; Kołodziejska, Żaneta; Weiss, Marek; Kozak, Maciej

    2015-01-01

    The success rate of gene therapy depends on the efficient transfection of genetic material into cells. The golden mean between harmlessness and high effectiveness can be provided by synthetic lipid-like molecules that are similar to the components of biological membranes. Cationic gemini surfactants are one such moiety and because of their favourable physicochemical properties (double positive electric charge, reduced toxicity, low values of critical micelle concentration), they show great potential as delivery system components for genetic material in gene therapy. The aim of this study was to investigate the process of the complexation of cationic gemini surfactants with nucleic acids: double-stranded DNA of different sizes (21 bp, ~185 bp, ~20 kbp) and siRNA (21 bp). The tested series of dicationic surfactants consists of bis-imidazolium quaternary salts with varying lengths of hydrophobic side chains (m = 5, 6, 7, 8, 9, 11, 12, 14, 16). On the basis of the data obtained by circular dichroism spectroscopy and electrophoresis, we concluded that the studied gemini surfactants with long side chains effectively bind nucleic acids at low concentrations, which leads to the formation of stable lipoplexes. Images obtained by atomic force microscopy also confirmed the formation of vesicular structures, i.e., complexes between DNA and surfactants. The cytotoxicity of selected surfactants was also tested on HeLa cells. The surfactant toxicity significantly depends on surfactant geometry (the length of hydrophobic chain). PMID:26641889

  7. Predicting cellulose solvating capabilities of acid-base conjugate ionic liquids.

    PubMed

    Parviainen, Arno; King, Alistair W T; Mutikainen, Ilpo; Hummel, Michael; Selg, Christoph; Hauru, Lauri K J; Sixta, Herbert; Kilpeläinen, Ilkka

    2013-11-01

    Different acid-base conjugates were made by combining a range of bases and superbases with acetic and propionic acid. Only the combinations that contained superbases were capable of dissolving cellulose. Proton affinities were calculated for the bases. A range, within which cellulose dissolution occurred, when combined with acetic or propionic acid, was defined for further use. This was above a proton affinity value of about 240 kcal mol(-1) at the MP2/6-311+G(d,p)//MP2/ 6-311+G(d,p) ab initio level. Understanding dissolution allowed us to determine that cation acidity contributed considerably to the ability of ionic liquids to dissolve cellulose and not just the basicity of the anion. By XRD analyses of suitable crystals, hydrogen bonding interactions between anion and cation were found to be the dominant interactions in the crystalline state. From determination of viscosities of these conjugates over a temperature range, certain structures were found to have as low a viscosity as 1-ethyl-3-methylimidazolium acetate, which was reflected in their high rate of cellulose dissolution but not necessarily the quantitative solubility of cellulose in those ionic liquids. 1,5-Diazabicyclo[4.3.0]non-5-enium propionate, which is one of the best structures for cellulose dissolution, was then distilled using laboratory equipment to demonstrate its recyclability.

  8. Predicting cellulose solvating capabilities of acid-base conjugate ionic liquids.

    PubMed

    Parviainen, Arno; King, Alistair W T; Mutikainen, Ilpo; Hummel, Michael; Selg, Christoph; Hauru, Lauri K J; Sixta, Herbert; Kilpeläinen, Ilkka

    2013-11-01

    Different acid-base conjugates were made by combining a range of bases and superbases with acetic and propionic acid. Only the combinations that contained superbases were capable of dissolving cellulose. Proton affinities were calculated for the bases. A range, within which cellulose dissolution occurred, when combined with acetic or propionic acid, was defined for further use. This was above a proton affinity value of about 240 kcal mol(-1) at the MP2/6-311+G(d,p)//MP2/ 6-311+G(d,p) ab initio level. Understanding dissolution allowed us to determine that cation acidity contributed considerably to the ability of ionic liquids to dissolve cellulose and not just the basicity of the anion. By XRD analyses of suitable crystals, hydrogen bonding interactions between anion and cation were found to be the dominant interactions in the crystalline state. From determination of viscosities of these conjugates over a temperature range, certain structures were found to have as low a viscosity as 1-ethyl-3-methylimidazolium acetate, which was reflected in their high rate of cellulose dissolution but not necessarily the quantitative solubility of cellulose in those ionic liquids. 1,5-Diazabicyclo[4.3.0]non-5-enium propionate, which is one of the best structures for cellulose dissolution, was then distilled using laboratory equipment to demonstrate its recyclability. PMID:24106149

  9. Role of adsorbed surfactant in the reaction of aryl diazonium salts with single-walled carbon nanotubes.

    PubMed

    Hilmer, Andrew J; McNicholas, Thomas P; Lin, Shangchao; Zhang, Jingqing; Wang, Qing Hua; Mendenhall, Jonathan D; Song, Changsik; Heller, Daniel A; Barone, Paul W; Blankschtein, Daniel; Strano, Michael S

    2012-01-17

    Because covalent chemistry can diminish the optical and electronic properties of single-walled carbon nanotubes (SWCNTs), there is significant interest in developing methods of controllably functionalizing the nanotube sidewall. To date, most attempts at obtaining such control have focused on reaction stoichiometry or strength of oxidative treatment. Here, we examine the role of surfactants in the chemical modification of single-walled carbon nanotubes with aryl diazonium salts. The adsorbed surfactant layer is shown to affect the diazonium derivatization of carbon nanotubes in several ways, including electrostatic attraction or repulsion, steric exclusion, and direct chemical modification of the diazonium reactant. Electrostatic effects are most pronounced in the cases of anionic sodium dodecyl sulfate and cationic cetyltrimethylammonium bromide, where differences in surfactant charge can significantly affect the ability of the diazonium ion to access the SWCNT surface. For bile salt surfactants, with the exception of sodium cholate, we find that the surfactant wraps tightly enough such that exclusion effects are dominant. Here, sodium taurocholate exhibits almost no reactivity under the explored reaction conditions, while for sodium deoxycholate and sodium taurodeoxycholate, we show that the greatest extent of reaction is observed among a small population of nanotube species, with diameters between 0.88 and 0.92 nm. The anomalous reaction of nanotubes in this diameter range seems to imply that the surfactant is less effective at coating these species, resulting in a reduced surface coverage on the nanotube. Contrary to the other bile salts studied, sodium cholate enables high selectivity toward metallic species and small band gap semiconductors, which is attributed to surfactant-diazonium coupling to form highly reactive diazoesters. Further, it is found that the rigidity of anionic surfactants can significantly influence the ability of the surfactant layer to

  10. Influence of surfactants on the morphology of SnO{sub 2} nanocrystals prepared via a hydrothermal method

    SciTech Connect

    Wang Mi; Gao Yanfeng; Dai Lei; Cao Chuanxiang; Guo Xuhong

    2012-05-15

    Nanoscaled SnO{sub 2} with different morphologies has been synthesized via a simple hydrothermal process at 180 Degree-Sign C using polyvinylpyrrolidone (PVP), sodium dodecyl sulfonate (SDS), cetyl trimethyl ammonium bromide (CTAB) or tetrapropyl ammonium bromide (TPAB) as surfactant. All the prepared SnO{sub 2} are of a tetragonal crystal structure. Nanocubes, nanorods, nanosheets, nanobelts and nanoparticles were prepared when changing the type and dosage of organic surfactants. It is shown that anionic surfactant (SDS) and cationic surfactant (CTAB or TPAB) at their suitable addition amounts can largely influence the morphologies of SnO{sub 2} nanocrystals. The effect is significantly dependent on the solvent types: water or ethanol. The non-ionic surfactant (PVP) can also change the morphologies like SDS but the impacts are less obvious. The effect of surfactants on the shape and size of SnO{sub 2} nanoparticles was discussed in detail. The particle growth mechanism is described based on the electrostatic interactions and Van der Waals' forces. - Graphical abstract: SnO{sub 2} nanocrystals with controllable morphologies were prepared via a hydrothermal method with surfactants. Highlights: Black-Right-Pointing-Pointer SnO{sub 2} nanocrystals were prepared via a hydrothermal method with surfactants. Black-Right-Pointing-Pointer SnO{sub 2} morphologies changed with the type and the dosage of surfactants. Black-Right-Pointing-Pointer The effect of surfactants on the growth of crystal planes was studied. Black-Right-Pointing-Pointer The controlling mechanisms of surfactants on SnO{sub 2} morphologies were discussed.

  11. Role of adsorbed surfactant in the reaction of aryl diazonium salts with single-walled carbon nanotubes.

    PubMed

    Hilmer, Andrew J; McNicholas, Thomas P; Lin, Shangchao; Zhang, Jingqing; Wang, Qing Hua; Mendenhall, Jonathan D; Song, Changsik; Heller, Daniel A; Barone, Paul W; Blankschtein, Daniel; Strano, Michael S

    2012-01-17

    Because covalent chemistry can diminish the optical and electronic properties of single-walled carbon nanotubes (SWCNTs), there is significant interest in developing methods of controllably functionalizing the nanotube sidewall. To date, most attempts at obtaining such control have focused on reaction stoichiometry or strength of oxidative treatment. Here, we examine the role of surfactants in the chemical modification of single-walled carbon nanotubes with aryl diazonium salts. The adsorbed surfactant layer is shown to affect the diazonium derivatization of carbon nanotubes in several ways, including electrostatic attraction or repulsion, steric exclusion, and direct chemical modification of the diazonium reactant. Electrostatic effects are most pronounced in the cases of anionic sodium dodecyl sulfate and cationic cetyltrimethylammonium bromide, where differences in surfactant charge can significantly affect the ability of the diazonium ion to access the SWCNT surface. For bile salt surfactants, with the exception of sodium cholate, we find that the surfactant wraps tightly enough such that exclusion effects are dominant. Here, sodium taurocholate exhibits almost no reactivity under the explored reaction conditions, while for sodium deoxycholate and sodium taurodeoxycholate, we show that the greatest extent of reaction is observed among a small population of nanotube species, with diameters between 0.88 and 0.92 nm. The anomalous reaction of nanotubes in this diameter range seems to imply that the surfactant is less effective at coating these species, resulting in a reduced surface coverage on the nanotube. Contrary to the other bile salts studied, sodium cholate enables high selectivity toward metallic species and small band gap semiconductors, which is attributed to surfactant-diazonium coupling to form highly reactive diazoesters. Further, it is found that the rigidity of anionic surfactants can significantly influence the ability of the surfactant layer to

  12. Soap opera : polymer-surfactant interactions on thin film surfaces /

    SciTech Connect

    Ozer, B. H.; Johal, M. S.; Wang, H. L.; Robinson, J. M.

    2001-01-01

    Surfactants are macromolecules with unique properties. They commonly contain a polar head group with a nonpolar hydrocarbon chain. These properties allow surfactants to solubilize greases and other nonpolar molecules. One particular way that this is accomplished is through the formation of micelles. Micelles are formed at the critical micelle concentration (cmc), which varies depending upon the nature of the surfactant and also the media in which the surfactant resides. These micelles can take a variety of shapes, but are generally characterized by surrounding the grease with the nonpolar hydrocarbon chains, exposing only the polarized head groups to the media, usually water. This property of easy solubilization has made surfactants a very attractive industrial agent, They are used most conventionally as industrial cleaning agents and detergents. However, they also have lesser-known applications in conjunction with polymers and other macromolecular mixtures, often creating a system with novel properties, such as increased solubilization and smoother mixture consistency. A recently developed field has investigated the self-assembly of polymers and polyelectrolytes onto thin film surfaces. There are many reasons for studying this process, such as for second harmonic generation purposes and bioassays. In this study, the interaction between the anionic polyelectrolyte poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) and two surfactants of opposite charge, Sodium Dodecyl Sulfate (SDS) and Dodecyl Trimethyl Ammonium Bromide (DTAB), in their assembly onto thin film surfaces was investigated. The kinetics of adsorbance onto the thin films was examined, followed by construction of 10-bilayer films using an alternating layer of the cationic polyelectrolyte poly(ethylenimine) (PEI) to provide the electrostatic means for the PAZO/surfactant combination to assemble onto the thin film. The kinetics of adsorption is being

  13. Renal acidification responses to respiratory acid-base disorders.

    PubMed

    Madias, Nicolaos E

    2010-01-01

    Respiratory acid-base disorders are those abnormalities in acid-base equilibrium that are expressed as primary changes in the arterial carbon dioxide tension (PaCO2). An increase in PaCO2 (hypercapnia) acidifies body fluids and initiates the acid-base disturbance known as respiratory acidosis. By contrast, a decrease in PaCO2 (hypocapnia) alkalinizes body fluids and initiates the acid-base disturbance known as respiratory alkalosis. The impact on systemic acidity of these primary changes in PaCO2 is ameliorated by secondary, directional changes in plasma [HCO3¯] that occur in 2 stages. Acutely, hypercapnia or hypocapnia yields relatively small changes in plasma [HCO3¯] that originate virtually exclusively from titration of the body's nonbicarbonate buffers. During sustained hypercapnia or hypocapnia, much larger changes in plasma [HCO3¯] occur that reflect adjustments in renal acidification mechanisms. Consequently, the deviation of systemic acidity from normal is smaller in the chronic forms of these disorders. Here we provide an overview of the renal acidification responses to respiratory acid-base disorders. We also identify gaps in knowledge that require further research.

  14. Surfactant induced complex formation and their effects on the interfacial properties of seawater.

    PubMed

    Guzmán, Eduardo; Santini, Eva; Benedetti, Alessandro; Ravera, Francesca; Ferrari, Michele; Liggieri, Libero

    2014-11-01

    The effect of a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB), on the interfacial properties of seawater has been studied by dynamic and equilibrium surface tension and by dilational rheology essays. Important modifications of the surface tension and dilational rheology response have been observed already at the very low CTAB concentrations, where the effects due to the high ionic strength are negligible. The comparison with the effects of CTAB in different seawater models, or in natural seawater fractions, points out the establishment of strong interactions between the surfactant molecules and the lipophilic fraction of organic material dispersed/dissolved in seawater, affecting the interfacial activity of the molecules. Considering the biochemical richness of seawater, these results can be explained assuming interaction mechanisms and adsorption schemes similar to those speculated for protein and other macromolecules in the presence of surfactants, which in fact show similar features. Thus already at the low concentrations the surfactant molecules form highly surface-active complexes with part of the organic fraction of seawater. At the larger surfactant concentrations these complexes compete for adsorption with an excess of free CTAB molecules which, according to the thermodynamic conditions, are most favoured to occupy the liquid interface. The results of this study underline the important role of the sea organic content in enhancing the surface-activity of surfactants, which is relevant for a deeper understand of the direct and indirect effects of these types of pollutants on the physico-chemical environment in the sea coastal areas and develop mitigation strategies.

  15. Exploring the Effects of Different Types of Surfactants on Zebrafish Embryos and Larvae

    PubMed Central

    Wang, Yanan; Zhang, Yuan; Li, Xu; Sun, Mingzhu; Wei, Zhuo; Wang, Yu; Gao, Aiai; Chen, Dongyan; Zhao, Xin; Feng, Xizeng

    2015-01-01

    Currently, surfactants are widely distributed in the environment. As organic pollutants, their toxicities have drawn extensive attention. In this study, the effects of anionic [sodium dodecyl sulphate (SDS) ], cationic [dodecyl dimethyl benzyl ammonium chloride (1227)] and non-ionic [fatty alcohol polyoxyethylene ether (AEO) ] surfactants on zebrafish larval behaviour were evaluated. Five behavioural parameters were recorded using a larval rest/wake assay, including rest total, number of rest bouts, rest bouts length, total activity and waking activity. The results revealed that 1227 and AEO at 1 μg/mL were toxic to larval locomotor activity and that SDS had no significant effects. Moreover, we tested the toxicities of the three surfactants in developing zebrafish embryos. AEO exposure resulted in smaller head size, smaller eye size and shorter body length relative to SDS and 1227. All three surfactants incurred concentration-dependent responses. Furthermore, in situ hybridisation indicated that smaller head size may be associated with a decreased expression of krox20. The altered expression of ntl demonstrated that the developmental retardation stemmed from inhibited cell migration and growth. These findings provide references for ecotoxicological assessments of different types of surfactants, and play a warning role in the application of surfactants. PMID:26053337

  16. Exploring the Effects of Different Types of Surfactants on Zebrafish Embryos and Larvae.

    PubMed

    Wang, Yanan; Zhang, Yuan; Li, Xu; Sun, Mingzhu; Wei, Zhuo; Wang, Yu; Gao, Aiai; Chen, Dongyan; Zhao, Xin; Feng, Xizeng

    2015-06-08

    Currently, surfactants are widely distributed in the environment. As organic pollutants, their toxicities have drawn extensive attention. In this study, the effects of anionic [sodium dodecyl sulphate (SDS)], cationic [dodecyl dimethyl benzyl ammonium chloride (1227)] and non-ionic [fatty alcohol polyoxyethylene ether (AEO)] surfactants on zebrafish larval behaviour were evaluated. Five behavioural parameters were recorded using a larval rest/wake assay, including rest total, number of rest bouts, rest bouts length, total activity and waking activity. The results revealed that 1227 and AEO at 1 μg/mL were toxic to larval locomotor activity and that SDS had no significant effects. Moreover, we tested the toxicities of the three surfactants in developing zebrafish embryos. AEO exposure resulted in smaller head size, smaller eye size and shorter body length relative to SDS and 1227. All three surfactants incurred concentration-dependent responses. Furthermore, in situ hybridisation indicated that smaller head size may be associated with a decreased expression of krox20. The altered expression of ntl demonstrated that the developmental retardation stemmed from inhibited cell migration and growth. These findings provide references for ecotoxicological assessments of different types of surfactants, and play a warning role in the application of surfactants.

  17. Emulsion electrospinning of polycaprolactone: influence of surfactant type towards the scaffold properties.

    PubMed

    Hu, Jue; Prabhakaran, Molamma P; Ding, Xin; Ramakrishna, Seeram

    2015-01-01

    Producing uniform nanofibers in high quality by electrospinning remains a huge challenge, especially using low concentrated polymer solutions. However, emulsion electrospinning assists to produce nanofibers from less concentrated polymer solutions compared to the traditional electrospinning process. The influence of individual surfactants towards the morphology of the emulsion electrospun poly (ɛ-caprolactone)/bovine serum albumin (PCL/BSA) nanofibers were investigated by using (i) non-ionic surfactant sorbitane monooleate (Span80); (ii) anionic sodium dodecyl sulfate (SDS); and (iii) cationic benzyltriethylammonium chloride, and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer Pluronic F108 of different concentrations. The morphology, along with the chemical and mechanical properties of the fibers, was evaluated by field emission scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, differential scanning calorimetry, water contact angle, and tensile tester. With the addition of surfactants, the electrospinnability of dilute PCL solution was enhanced, with either branched or uniform fibers were obtained. Electrospinning of an emulsion containing 0.4% (w/v) SDS produced the smallest and the most uniform nanofibers (167 ± 39 nm), which was attributed to the high conductivity of the solution. Analysis revealed that the emulsion electrospun nanofibers containing different surfactants and surfactant concentrations differ in fiber morphology and mechanical properties. Results suggest that surfactants have the ability to modulate the fiber morphology via electrostatic and hydrogen bonding, depending on their chemical structure.

  18. Heterosupramolecular photocatalysis: oxidation of organic compounds in nanospaces between surfactant bilayers formed on TiO2.

    PubMed

    Tada, Hiroaki; Matsui, Hideo; Shiota, Fumitaka; Nomura, Megumi; Ito, Seishiro; Yoshihara, Masakuni; Esumi, Kunio

    2002-08-21

    A heterosupramolecular photocatalyst consisting of TiO2 and a cationic surfactant bilayer formed on the surface has achieved a very high level of activity in the oxidation of 2-naphthol through the cooperation of the inorganic and organic components.

  19. In vitro synergistic activities of essential oils and surfactants in combination with cosmetic preservatives against Pseudomonas aeruginosa and Staphylococcus aureus.

    PubMed

    Patrone, Vania; Campana, Raffaella; Vittoria, Emanuela; Baffone, Wally

    2010-04-01

    The aim of this study is to evaluate possible synergistic antimicrobial interactions between common cosmetic preservatives and selected essential oils or surfactants. The antimicrobial efficacy of six essential oils, three surfactants and five preservatives against Pseudomonas aeruginosa ATCC 9027 and Staphylococcus aureus ATCC 43387 was assessed by a broth micro-dilution assay. MICs for individual and combined antimicrobials were determined and then transformed to fractional inhibitory concentration (FIC) indexes. All essential oils exhibited antibacterial activity; among surfactants, bacteria resulted most susceptible to the cationic agent. Synergy was observed when essential oils of eucalyptus and mint were combined with methylparaben against P. aeruginosa, while essential oils of mint, oregano and sage combined with propylparaben and imidazolidinyl urea acted against S. aureus. Many binary mixtures of preservatives and surfactants produced synergistic activity with the most effective interactions involving the cationic and amphoteric compounds under study. FIC indexes demonstrated synergistic effects when preservatives were combined with either essential oils or surfactants against both bacterial strains. These results highlight the potential usefulness of essential oils and surfactants to enhance the activities of conventional biocides. This kind of study should contribute to the selection and optimization of preservative systems for cosmetic preparations.

  20. Biomimicry of surfactant protein C.

    PubMed

    Brown, Nathan J; Johansson, Jan; Barron, Annelise E

    2008-10-01

    Since the widespread use of exogenous lung surfactant to treat neonatal respiratory distress syndrome, premature infant survival and respiratory morbidity have dramatically improved. Despite the effectiveness of the animal-derived surfactant preparations, there still remain some concerns and difficulties associated with their use. This has prompted investigation into the creation of synthetic surfactant preparations. However, to date, no clinically used synthetic formulation is as effective as the natural material. This is largely because the previous synthetic formulations lacked analogues of the hydrophobic proteins of the lung surfactant system, SP-B and SP-C, which are critical functional constituents. As a result, recent investigation has turned toward the development of a new generation of synthetic, biomimetic surfactants that contain synthetic phospholipids along with a mimic of the hydrophobic protein portion of lung surfactant. In this Account, we detail our efforts in creating accurate mimics of SP-C for use in a synthetic surfactant replacement therapy. Despite SP-C's seemingly simple structure, the predominantly helical protein is extraordinarily challenging to work with given its extreme hydrophobicity and structural instability, which greatly complicates the creation of an effective SP-C analogue. Drawing inspiration from Nature, two promising biomimetic approaches have led to the creation of rationally designed biopolymers that recapitulate many of SP-C's molecular features. The first approach utilizes detailed SP-C structure-activity relationships and amino acid folding propensities to create a peptide-based analogue, SP-C33. In SP-C33, the problematic and metastable polyvaline helix is replaced with a structurally stable polyleucine helix and includes a well-placed positive charge to prevent aggregation. SP-C33 is structurally stable and eliminates the association propensity of the native protein. The second approach follows the same design

  1. Has Stewart approach improved our ability to diagnose acid-base disorders in critically ill patients?

    PubMed

    Masevicius, Fabio D; Dubin, Arnaldo

    2015-02-01

    The Stewart approach-the application of basic physical-chemical principles of aqueous solutions to blood-is an appealing method for analyzing acid-base disorders. These principles mainly dictate that pH is determined by three independent variables, which change primarily and independently of one other. In blood plasma in vivo these variables are: (1) the PCO2; (2) the strong ion difference (SID)-the difference between the sums of all the strong (i.e., fully dissociated, chemically nonreacting) cations and all the strong anions; and (3) the nonvolatile weak acids (Atot). Accordingly, the pH and the bicarbonate levels (dependent variables) are only altered when one or more of the independent variables change. Moreover, the source of H(+) is the dissociation of water to maintain electroneutrality when the independent variables are modified. The basic principles of the Stewart approach in blood, however, have been challenged in different ways. First, the presumed independent variables are actually interdependent as occurs in situations such as: (1) the Hamburger effect (a chloride shift when CO2 is added to venous blood from the tissues); (2) the loss of Donnan equilibrium (a chloride shift from the interstitium to the intravascular compartment to balance the decrease of Atot secondary to capillary leak; and (3) the compensatory response to a primary disturbance in either independent variable. Second, the concept of water dissociation in response to changes in SID is controversial and lacks experimental evidence. In addition, the Stewart approach is not better than the conventional method for understanding acid-base disorders such as hyperchloremic metabolic acidosis secondary to a chloride-rich-fluid load. Finally, several attempts were performed to demonstrate the clinical superiority of the Stewart approach. These studies, however, have severe methodological drawbacks. In contrast, the largest study on this issue indicated the interchangeability of the Stewart and

  2. Impact of model perfumes on surfactant and mixed surfactant self-assembly.

    PubMed

    Penfold, J; Tucker, I; Green, A; Grainger, D; Jones, C; Ford, G; Roberts, C; Hubbard, J; Petkov, J; Thomas, R K; Grillo, I

    2008-11-01

    The impact of some model perfumes on surfactant self-assembly has been investigated, using small-angle neutron scattering. A range of different model perfumes, with differing degrees of hydrophilicity/hydrophobicity, have been explored, and in order of increasing hydrophobicity include phenyl ethanol (PE), rose oxide (RO), limonene (LM), linalool (LL), and dihydrogen mercenol (DHM). The effect of their solubilization on the nonionic surfactant micelles of dodecaethylene monododecyl ether (C12EO12) and on the mixed surfactant aggregates of C12EO12 and the cationic dialkyl chain surfactant dihexadecyl dimethyl ammonium bromide (DHDAB) has been quantified. For PE and LL the effect of their solubilization on the micelle, mixed micelle/lamellar and lamellar regimes of the C12EO12/DHDAB mixtures, has also been determined. For the C12EO12 and mixed DHDAB/C12EO12 micelles PE is solubilized predominantly at the hydrophilic/hydrophobic interface, whereas the more hydrophobic perfumes, from RO to DHM, are solubilized predominantly in the hydrophobic core of the micelles. For the C12EO12 micelles, with increasing perfume concentration, the more hydrophobic perfumes (RO to DHM) promote micellar growth. Relatively modest growth is observed for RO and LM, whereas substantial growth is observed for LL and DHM. In contrast, for the addition of PE the C12EO12 micelles remain as relatively small globular micelles, with no significant growth. For the C12EO12/DHDAB mixed micelles, the pattern of behavior with the addition of perfume is broadly similar, except that the micellar growth with increasing perfume concentration for the more hydrophobic perfumes is less pronounced. In the Lbeta (Lv) region of the DHDAB-rich C12EO12/DHDAB phase diagram, the addition of PE results in a less structured (less rigid) lamellar phase, and ultimately a shift toward a structure more consistent with a sponge or bicontinuous phase. In the mixed L1/Lbeta region of the phase diagram PE induces a slight

  3. Cesium cation affinities and basicities

    NASA Astrophysics Data System (ADS)

    Gal, Jean-François; Maria, Pierre-Charles; Massi, Lionel; Mayeux, Charly; Burk, Peeter; Tammiku-Taul, Jaana

    2007-11-01

    This review focuses on the quantitative data related to cesium cation interaction with neutral or negatively charged ligands. The techniques used for measuring the cesium cation affinity (enthalpies, CCA), and cesium cation basicities (Gibbs free energies, CCB) are briefly described. The quantum chemical calculations methods that were specifically designed for the determination of cesium cation adduct structures and the energetic aspects of the interaction are discussed. The experimental results, obtained essentially from mass spectrometry techniques, and complemented by thermochemical data, are tabulated and commented. In particular, the correlations between cesium cation affinities and lithium cation affinities for the various kinds of ligands (rare gases, polyatomic neutral molecules, among them aromatic compounds and negative ions) serve as a basis for the interpretation of the diverse electrostatic modes of interaction. A brief account of some recent analytical applications of ion/molecule reactions with Cs+, as well as other cationization approaches by Cs+, is given.

  4. Spectral studies of safranin-O in different surfactant solutions

    NASA Astrophysics Data System (ADS)

    Göktürk, Sinem; Tunçay, Melda

    2003-06-01

    The interaction of Safranin-O (SO), a cationic dye, with various surfactants viz., anionics; Sodiumdodecylsulfate (SDS) and Sodiumdodecylsulfonate (SDSo), nonionics; polyoxyethylenesorbitanmonolaurate (Tween 20) and polyoxyethylenedodecylether (Brij 35), cationic; Dodecyltrimethylammoniumbromide (DTAB) and zwitterionic; Laurylsulfobetaine (LSB) was studied spectrophotometrically as a function of surfactant concentration ranging from premicellar to postmicellar region in aqueous media in the absence and presence of cosolvents. The binding constants (Kb) and fraction of bound SO to micelles (f), were calculated by means of Benesi-Hildebrand Equation. The binding tendency of SO to micelles followed the order as; Tween 20>Brij 35>SDS>SDSo>LSB. The presence of cosolvents, such as Methanol, Dimethylformamide (DMFA) and 1,4 Dioxan (DX) at various volume percentages, increased the CMC of both SDS and Tween 20 and at a certain concentration totally inhibited the micellization. The binding of SO to micelles decreased as the concentration of the cosolvents increased. This inhibitory effect of cosolvents on binding of SO to micelles followed the order as; Methanol>DMFA>DX.

  5. Surfactant for pediatric acute lung injury.

    PubMed

    Willson, Douglas F; Chess, Patricia R; Notter, Robert H

    2008-06-01

    This article reviews exogenous surfactant therapy and its use in mitigating acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) in infants, children, and adults. Biophysical and animal research documenting surfactant dysfunction in ALI/ARDS is described, and the scientific rationale for treatment with exogenous surfactant is discussed. Major emphasis is placed on reviewing clinical studies of surfactant therapy in pediatric and adult patients who have ALI/ARDS. Particular advantages from surfactant therapy in direct pulmonary forms of these syndromes are described. Also discussed are additional factors affecting the efficacy of exogenous surfactants in ALI/ARDS.

  6. Controlled synthesis of gold nanostars by using a zwitterionic surfactant.

    PubMed

    Casu, Alberto; Cabrini, Elisa; Donà, Alice; Falqui, Andrea; Diaz-Fernandez, Yuri; Milanese, Chiara; Taglietti, Angelo; Pallavicini, Piersandro

    2012-07-23

    By replacing cetyltrimethylammonium bromide (CTAB) with the zwitterionic lauryl sulfobetaine (LSB) surfactant in the classical seed-growth synthesis, monocrystalline gold nanostars (m-NS) and pentatwinned gold asymmetric nanostars (a-NS) were obtained instead of nanorods. The main product under all synthetic conditions was a-NS, which have branches with high aspect ratios (AR), thus leading to LSPR absorptions in the 750-1150 nm range. The percentage of m-NS versus a-NS, the aspect ratio of the a-NS branches, and consequently the position of their LSPR absorption can be finely tuned simply by regulating the concentration of reductant, the concentration of surfactant, or the concentration of the "catalytic" Ag(+) cation. The m-NS have instead shorter and larger branches, the AR of which is poorly influenced by synthetic conditions and displays an LSPR positioned around 700 nm. A growth mechanism that involves the direct contact of the sulfate moiety of LSB on the surface of the nano-object is proposed, thereby implying preferential coating of the {111} Au faces with weak interactions. Consistent with this, we also observed the straightforward complete displacement of the LSB surfactant from the surface of the nanostars. This was obtained by the simple addition of thiols in aqueous solution to yield extremely stable coated a-NS and m-NS that are resistant to highly acidic, basic, and in similar to in vivo conditions.

  7. Micellization Behavior of Long-Chain Substituted Alkylguanidinium Surfactants

    PubMed Central

    Bouchal, Roza; Hamel, Abdellah; Hesemann, Peter; In, Martin; Prelot, Bénédicte; Zajac, Jerzy

    2016-01-01

    Surface activity and micelle formation of alkylguanidinium chlorides containing 10, 12, 14 and 16 carbon atoms in the hydrophobic tail were studied by combining conductivity and surface tension measurements with isothermal titration calorimetry. The purity of the resulting surfactants, their temperatures of Cr→LC and LC→I transitions, as well as their propensity of forming birefringent phases, were assessed based on the results of 1H and 13C NMR, differential scanning calorimetry (DSC), and polarizing microscopy studies. Whenever possible, the resulting values of Krafft temperature (TK), critical micelle concentration (CMC), minimum surface tension above the CMC, chloride counter-ion binding to the micelle, and the standard enthalpy of micelle formation per mole of surfactant (ΔmicH°) were compared to those characterizing alkyltrimethylammonium chlorides or bromides with the same tail lengths. The value of TK ranged between 292 and 314 K and increased strongly with the increase in the chain length of the hydrophobic tail. Micellization was described as both entropy and enthalpy-driven. Based on the direct calorimetry measurements, the general trends in the CMC with the temperature, hydrophobic tail length, and NaCl addition were found to be similar to those of other types of cationic surfactants. The particularly exothermic character of micellization was ascribed to the hydrogen-binding capacity of the guanidinium head-group. PMID:26861309

  8. Controlled synthesis of gold nanostars by using a zwitterionic surfactant.

    PubMed

    Casu, Alberto; Cabrini, Elisa; Donà, Alice; Falqui, Andrea; Diaz-Fernandez, Yuri; Milanese, Chiara; Taglietti, Angelo; Pallavicini, Piersandro

    2012-07-23

    By replacing cetyltrimethylammonium bromide (CTAB) with the zwitterionic lauryl sulfobetaine (LSB) surfactant in the classical seed-growth synthesis, monocrystalline gold nanostars (m-NS) and pentatwinned gold asymmetric nanostars (a-NS) were obtained instead of nanorods. The main product under all synthetic conditions was a-NS, which have branches with high aspect ratios (AR), thus leading to LSPR absorptions in the 750-1150 nm range. The percentage of m-NS versus a-NS, the aspect ratio of the a-NS branches, and consequently the position of their LSPR absorption can be finely tuned simply by regulating the concentration of reductant, the concentration of surfactant, or the concentration of the "catalytic" Ag(+) cation. The m-NS have instead shorter and larger branches, the AR of which is poorly influenced by synthetic conditions and displays an LSPR positioned around 700 nm. A growth mechanism that involves the direct contact of the sulfate moiety of LSB on the surface of the nano-object is proposed, thereby implying preferential coating of the {111} Au faces with weak interactions. Consistent with this, we also observed the straightforward complete displacement of the LSB surfactant from the surface of the nanostars. This was obtained by the simple addition of thiols in aqueous solution to yield extremely stable coated a-NS and m-NS that are resistant to highly acidic, basic, and in similar to in vivo conditions. PMID:22736477

  9. Role of an amide bond for self-assembly of surfactants.

    PubMed

    Bordes, Romain; Tropsch, Juergen; Holmberg, Krister

    2010-03-01

    Self-assembly in solution and adsorption at the air-water interface and at solid surfaces were investigated for two amino-acid-based surfactants with conductimetry, NMR, tensiometry, quartz crystal microbalance with monitoring of the dissipation (QCM-D), and surface plasmon resonance (SPR). The surfactants studied were sodium N-lauroylglycinate and sodium N-lauroylsarcosinate, differing only in a methyl group on the amide nitrogen for the sarcosinate. Thus, the glycinate but not the sarcosinate surfactant is capable of forming intermolecular hydrogen bonds via the amide group. It was found that the amide bond, N-methylated or not, gave a substantial contribution to the hydrophilicity of the amphiphile. The ability to form intermolecular hydrogen bonds led to tighter packing at the air-water interface and at a hydrophobic surface. It also increased the tendency for precipitation as an acid-soap pair on addition of acid. Adsorption of the surfactants at a gold surface was also investigated and gave unexpected results. The sarcosine-based surfactant seemed to give bilayer adsorption, while the glycine derivative adsorbed as a monolayer.

  10. Acid Base Titrations in Nonaqueous Solvents and Solvent Mixtures

    NASA Astrophysics Data System (ADS)

    Barcza, Lajos; Buvári-Barcza, Ágnes

    2003-07-01

    The acid base determination of different substances by nonaqueous titrations is highly preferred in pharmaceutical analyses since the method is quantitative, exact, and reproducible. The modern interpretation of the reactions in nonaqueous solvents started in the last century, but several inconsistencies and unsolved problems can be found in the literature. The acid base theories of Brønsted Lowry and Lewis as well as the so-called solvent theory are outlined first, then the promoting (and leveling) and the differentiating effects are discussed on the basis of the hydrogen-bond concept. Emphasis is put on the properties of formic acid and acetic anhydride since their importance is increasing.

  11. An Acid-Base Chemistry Example: Conversion of Nicotine

    NASA Astrophysics Data System (ADS)

    Summerfield, John H.

    1999-10-01

    The current government interest in nicotine conversion by cigarette companies provides an example of acid-base chemistry that can be explained to students in the second semester of general chemistry. In particular, the conversion by ammonia of the +1 form of nicotine to the easier-to-assimilate free-base form illustrates the effect of pH on acid-base equilibrium. The part played by ammonia in tobacco smoke is analogous to what takes place when cocaine is "free-based".

  12. Surfactant-Wrapped Multiwalled Carbon Nanotubes in Aquatic Systems: Surfactant Displacement in the Presence of Humic Acid.

    PubMed

    Chang, Xiaojun; Bouchard, Dermont C

    2016-09-01

    Sodium dodecyl sulfate (SDS) facilitates multiwalled carbon nanotube (MWCNT) debundling and enhances nanotube stability in the aqueous environment by adsorbing on the nanotube surfaces, thereby increasing repulsive electrostatic forces and steric effects. The resulting SDS-wrapped MWCNTs are utilized in industrial applications and have been widely employed in environmental studies. In the present study, MWCNTs adsorbed SDS during ultrasonication to form stable MWCNTs suspensions. Desorption of SDS from MWCNTs surfaces was then investigated as a function of Suwannee River Humic Acid (SRHA) and background electrolyte concentrations. Due to hydrophobic effects and π-π interactions, MWCNTs exhibit higher affinity for SRHA than SDS. In the presence of SRHA, SDS adsorbed on MWCNTs was displaced. Cations (Na(+), Ca(2+)) decreased SDS desorption from MWCNTs due to charge screening effects. Interestingly, the presence of the divalent calcium cation facilitated multilayered SRHA adsorption on MWCNTs through bridging effects, while monovalent sodium reduced SRHA adsorption. Results of the present study suggest that properties of MWCNTs wrapped with commercial surfactants will be altered when these materials are released to surface waters and the surfactant coating will be displaced by natural organic matter (NOM). Changes on their surfaces will significantly affect MWCNTs fate in aquatic environments. PMID:27500910

  13. Lipoamino acid-based micelles as promising delivery vehicles for monomeric amphotericin B.

    PubMed

    Serafim, Cláudia; Ferreira, Inês; Rijo, Patrícia; Pinheiro, Lídia; Faustino, Célia; Calado, António; Garcia-Rio, Luis

    2016-01-30

    Lipoamino acid-based micelles have been developed as delivery vehicles for the hydrophobic drug amphotericin B (AmB). The micellar solubilisation of AmB by a gemini lipoamino acid (LAA) derived from cysteine and its equimolar mixtures with the bile salts sodium cholate (NaC) and sodium deoxycholate (NaDC), as well as the aggregation sate of the drug in the micellar systems, was studied under biomimetic conditions (phosphate buffered-saline, pH 7.4) using UV-vis spectroscopy. Pure surfactant systems and equimolar mixtures were characterized by tensiometry and important parameters were determined, such as critical micelle concentration (CMC), surface tension at the CMC (γCMC), maximum surface excess concentration (Γmax), and minimum area occupied per molecule at the water/air interface (Amin). Rheological behaviour from viscosity measurements at different shear rates was also addressed. Solubilisation capacity was quantified in terms of molar solubilisation ratio (χ), micelle-water partition coefficient (KM) and Gibbs energy of solubilisation (ΔGs°). Formulations of AmB in micellar media were compared in terms of drug loading, encapsulation efficiency, aggregation state of AmB and in vitro antifungal activity against Candida albicans. The LAA-containing micellar systems solubilise AmB in its monomeric and less toxic form and exhibit in vitro antifungal activity comparable to that of the commercial formulation Fungizone.

  14. Surfactant-modified zeolites as permeable barriers to organic and inorganic groundwater contaminants

    SciTech Connect

    Bowman, R.S.; Sullivan, E.J.

    1995-10-01

    We have shown in laboratory experiments that natural zeolites treated with hexadecyltrimethylammonium (HDTMA) are effective sorbents for nonpolar organics, inorganic cations, and inorganic anions. Due to their low cost ({approximately}$0.75/kg) and granular nature, HDTMA-zeolites appear ideal candidates for reactive, permeable subsurface barriers. The HDTMA-zeolites are stable over a wide range of pH (3-13), ionic strength (1 M Cs{sup +} or Ca{sup 2+}), and in organic solvents. Surfactant-modified zeolites sorb nonpolar organics (benzene, toluene, xylene, chlorinated aliphatics) via a partitioning mechanism, inorganic cations (Pb{sup 2+}) via ion exchange and surface complexation, and inorganic anions (CrO{sub 4}{sup 2-}, SeO{sub 4}{sup 2-}, SO{sub 4}{sup 2-}) via surface precipitation.The goal of this work is to demonstrate the use of surfactant-modified zeolite as a permeable barrier to ground water contaminants.

  15. Decisive interactions between the heterocyclic moiety and the cluster observed in polyoxometalate-surfactant hybrid crystals.

    PubMed

    Otobe, Saki; Fujioka, Natsumi; Hirano, Takuro; Ishikawa, Eri; Naruke, Haruo; Fujio, Katsuhiko; Ito, Takeru

    2015-04-16

    Inorganic-organic hybrid crystals were successfully obtained as single crystals by using polyoxotungstate anion and cationic dodecylpyridazinium (C12pda) and dodecylpyridinium (C12py) surfactants. The decatungstate (W10) anion was used as the inorganic component, and the crystal structures were compared. In the crystal comprising C12pda (C12pda-W10), the heterocyclic moiety directly interacted with W10, which contributed to a build-up of the crystal structure. On the other hand, the crystal consisting of C12py (C12py-W10) had similar crystal packing and molecular arrangement to those in the W10 crystal hybridized with other pyridinium surfactants. These results indicate the significance of the heterocyclic moiety of the surfactant to construct hybrid crystals with polyoxometalate anions.

  16. Conductive Hybrid Crystal Composed from Polyoxomolybdate and Deprotonatable Ionic-Liquid Surfactant

    PubMed Central

    Kobayashi, Jun; Kawahara, Ryosuke; Uchida, Sayaka; Koguchi, Shinichi; Ito, Takeru

    2016-01-01

    A polyoxomolybdate inorganic-organic hybrid crystal was synthesized with deprotonatable ionic-liquid surfactant. 1-dodecylimidazolium cation was employed for its synthesis. The hybrid crystal contained δ-type octamolybdate (Mo8) isomer, and possessed alternate stacking of Mo8 monolayers and interdigitated surfactant bilayers. The crystal structure was compared with polyoxomolybdate hybrid crystals comprising 1-dodecyl-3-methylimidazolium surfactant, which preferred β-type Mo8 isomer. The less bulky hydrophilic moiety of the 1-dodecylimidazolium interacted with the δ-Mo8 anion by N–H···O hydrogen bonds, which presumably induced the formation of the δ-Mo8 anion. Anhydrous conductivity of the hybrid crystal was estimated to be 5.5 × 10−6 S·cm−1 at 443 K by alternating current (AC) impedance spectroscopy. PMID:27347926

  17. Structural diversity, physicochemical properties and application of imidazolium surfactants: Recent advances.

    PubMed

    Bhadani, Avinash; Misono, Takeshi; Singh, Sukhprit; Sakai, Kenichi; Sakai, Hideki; Abe, Masahiko

    2016-05-01

    The current review covers recent advances on development and investigation of cationic surfactants containing imidazolium headgroup, which are being extensively investigated for their self-aggregation properties and are currently being utilized in various conventional and non-conventional application areas. These surfactants are being used as: soft template for synthesis of mesoporous/microporous materials, drug and gene delivery agent, stabilizing agent for nanoparticles, dispersants for single/multi walled carbon nanotubes, antimicrobial and antifungal agent, viscosity modifiers, preparing nanocomposite materials, stabilizing microemulsions, corrosion inhibitors and catalyst for organic reactions. Recently several structural derivatives of these surfactants have been developed having many interesting physicochemical properties and they have demonstrated enormous potential in the area of nanotechnology, material science and biomedical science. PMID:27063924

  18. Automated flow system for sildenafil enrichment using surfactant coated solid-phase with fluorescence detection.

    PubMed

    Wang, Chien Chun; Sombra, Lorena; Fernández, Liliana

    2012-08-30

    In this work, Amberlite XAD-1180 resin is used for on-line surfactant-mediated pre-concentration of sildenafil as a prior step for its fluorescent detection. In order to activate the column for sildenafil pre-concentration, the cationic surfactant (hexadecyltrimethylammoniunm bromide, HTAB) is adsorbed onto the resin. In these conditions, sildenafil is retained by HTAB-resin and then it is eluted with ethanol and analyzed by spectrofluorimetry. Drug-surfactant association produces a considerable fluorescence enhancement, increasing considerably the sensitivity of detection. Therefore, sildenafil can be pre-concentrated and quantitatively determined, with a detection limit of 0.2 ng mL(-1). The proposed method was successfully applied to the analysis of bulk drug, human urine, tablets, and local herbal medicine. Validation processes were performed by recovering studies and statistical analysis with satisfactory results.

  19. Size dependent fractal aggregation mediated through surfactant in silica nanoparticle solution

    NASA Astrophysics Data System (ADS)

    Kumar, Sugam; Aswal, V. K.; Kohlbrecher, J.

    2012-06-01

    Small-angle neutron scattering (SANS) has been used to study aggregation of anionic silica nanoparticles in presence of cationic surfactant (DTAB) in aqueous solution. The measurements were carried out for different sizes of nanoparticles (8.2, 16.4 and 26.4 nm) at fixed (1 wt%) nanoparticles and surfactant concentration. It is found that the adsorption of surfactant micelles on the silica nanoparticles leads to the aggregation of nanoparticles, which is characterized by a fractal structure. The number of adsorbed micelles on nanoparticle increases from 7 to 152 with the increase in the size of the nanoparticle from 8.2 to 26.4 nm, whereas interestingly the fractal dimension remains same. The aggregate morphology in these systems is expected to be governed by the diffusion limited aggregation.

  20. [Influence of Different Type of Surfactant on Bacteriolytic Activity of Lysozyme].

    PubMed

    Ivanov, R A; Soboleva, O A; Smirnov, S A; Levashov, P A

    2015-01-01

    The influence ofvarious surfactants (anionic sodium dodecyl sulfate, SDS, cationic dodecyltrimethylarnmonium bromide, DTAB, and zwitterionic cocoamidopropylbetaine, CAPB) on the activity of the chicken egg lysozyme is investigated. Lysis of Gram-positive bacteria by the enzyme was carried out at pH 7.2 and ionic strength of 0.15 M. It was found that at low SDS and DTAB concentrations (less than 1 x 10(-5) M) the bacteriolytic activity increases by 30-140%. At higher concentrations (1 x 10(-5) - 1 x 10(4) M) the activity returns to the level observed in the absence of the surfactants. The elevated activity correlated with the formation of hydrophobic lysozyme-surfactant complexes. Introduction of CAPB at concentrations above 1 x 10(-5) M sig, nificantly diminished the bacteriolytic activity due to CAPB induced aggregation of lysozyme.

  1. Understanding of ZnO morphologies in the presence of surfactants

    NASA Astrophysics Data System (ADS)

    Singh, Baljinder; Kaura, Aman; Singh, Gurinder; Saini, G. S. S.; Tripathi, S. K.

    2016-05-01

    Zinc oxide (ZnO) nanostructures (dumbbell, flower and tablets) are synthesized using zinc precursor, anionic surfactant Sodium Dodecyl Sulphate (SDS) and cationic surfactant Dodecyl Trimethyl Ammonium bromide (DTAB) by chemical route. Inadequate covering of ZnO with SDS leads to ZnO dumbbells, which are assembled to form flower like geometry. Mixture of SDS and DTAB retards the growth along polar planes i.e. (0001) and (000 1 ¯) respectively, resulting in the formation of tablets. The experimental results are studied by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and UV-Vis spectroscopy (UV-Vis), which indicates that chemical nature of surfactants, is responsible for the variation of ZnO morphologies.

  2. Influence of various surfactants on magnetic property of cobalt ferrite prepared by Co-precipitation technique

    NASA Astrophysics Data System (ADS)

    Solanki, Neha; Khatri, Hemal; Jotania, R. B.

    2016-05-01

    Cobalt Ferrite (CoFe2O4) particles were synthesised using a Co-precipitation method. Influence of three different surfactants i.e. (1) Cationic - CTAB (Cetyl Tri-Methyl Ammonium Bromide), (2) Anionic - SDBS (Sodium Dodecyl Benzene Sulphonate) and (3) Nonionic - Triton X-100, on magnetic property of Cobalt Ferrite were investigated. Magnetic property of Cobalt ferrite powder was studied at room temperature using Vibrating Sample Measurements (VSM) technique under an applied magnetic field of 15kOe. The results show maximum value of saturation magnetization - Ms (81.87 emu/g) for the sample synthesised without surfactant and Coercivity value found maximum (2086 kOe) for the sample synthesized in presence of surfactant SDBS.

  3. Selection and evaluation of adsorbents for the removal of anionic surfactants from laundry rinsing water.

    PubMed

    Schouten, Natasja; van der Ham, Louis G J; Euverink, Gert-Jan W; de Haan, André B

    2007-10-01

    Low-cost adsorbents were tested to remove anionic surfactants from laundry rinsing water to allow re-use of water. Adsorbents were selected corresponding to the different surfactant adsorption mechanisms. Equilibrium adsorption studies of linear alkyl benzene sulfonate (LAS) show that ionic interaction results in a high maximum adsorption capacity on positively charged adsorbents of 0.6-1.7 gLAS/g. Non-ionic interactions, such as hydrophobic interactions of LAS with non-ionic resins or activated carbons, result in a lower adsorption capacity of 0.02-0.6 gLAS/g. Negatively charged materials, such as cation exchange resins or bentonite clay, have negligible adsorption capacities for LAS. Similar results are obtained for alpha olefin sulfonate (AOS). Cost comparison of different adsorbents shows that an inorganic anion exchange material (layered double hydroxide) and activated carbons are the most cost-effective materials in terms of the amount of surfactant adsorbed per dollar worth of adsorbent.

  4. Conductive Hybrid Crystal Composed from Polyoxomolybdate and Deprotonatable Ionic-Liquid Surfactant.

    PubMed

    Kobayashi, Jun; Kawahara, Ryosuke; Uchida, Sayaka; Koguchi, Shinichi; Ito, Takeru

    2016-01-01

    A polyoxomolybdate inorganic-organic hybrid crystal was synthesized with deprotonatable ionic-liquid surfactant. 1-dodecylimidazolium cation was employed for its synthesis. The hybrid crystal contained δ-type octamolybdate (Mo₈) isomer, and possessed alternate stacking of Mo₈ monolayers and interdigitated surfactant bilayers. The crystal structure was compared with polyoxomolybdate hybrid crystals comprising 1-dodecyl-3-methylimidazolium surfactant, which preferred β-type Mo₈ isomer. The less bulky hydrophilic moiety of the 1-dodecylimidazolium interacted with the δ-Mo₈ anion by N-H···O hydrogen bonds, which presumably induced the formation of the δ-Mo₈ anion. Anhydrous conductivity of the hybrid crystal was estimated to be 5.5 × 10(-6) S·cm(-1) at 443 K by alternating current (AC) impedance spectroscopy. PMID:27347926

  5. Charged nanoparticles as supramolecular surfactants for controlling the growth and stability of microcrystals

    NASA Astrophysics Data System (ADS)

    Kowalczyk, Bartlomiej; Bishop, Kyle J. M.; Lagzi, Istvan; Wang, Dawei; Wei, Yanhu; Han, Shuangbing; Grzybowski, Bartosz A.

    2012-03-01

    Microcrystals of desired sizes are important in a range of processes and materials, including controlled drug release, production of pharmaceutics and food, bio- and photocatalysis, thin-film solar cells and antibacterial fabrics. The growth of microcrystals can be controlled by a variety of agents, such as multivalent ions, charged small molecules, mixed cationic-anionic surfactants, polyelectrolytes and other polymers, micropatterned self-assembled monolayers, proteins and also biological organisms during biomineralization. However, the chief limitation of current approaches is that the growth-modifying agents are typically specific to the crystalizing material. Here, we show that oppositely charged nanoparticles can function as universal surfactants that control the growth and stability of microcrystals of monovalent or multivalent inorganic salts, and of charged organic molecules. We also show that the solubility of the microcrystals can be further tuned by varying the thickness of the nanoparticle surfactant layers and by reinforcing these layers with dithiol crosslinks.

  6. Acid-base status in dietary treatment of phenylketonuria.

    PubMed

    Manz, F; Schmidt, H; Schärer, K; Bickel, H

    1977-10-01

    Blood acid-base status, serum electrolytes, and urine pH were examined in 64 infants and children with phenylketonuria (PKU) treated with three different low phenylalanine protein hydrolyzates (Aponti, Cymogran, AlbumaidXP) and two synthetic amino acid mixtures (Aminogran, PAM). The formulas caused significant differences in acid-base status, serum potassium, and chloride, and in urine pH. In acid-base balance studies in two patients with PKU, Aponti, PAM, and two modifications of PAM (P2 + P3) were given. We observed a change from mild alkalosis to increasing metabolic acidosis from Aponti (serum bicarbonate 25,8 mval/liter) to P3 (24,0Y, P2 (19, 3) and PAM (17,0). Urine pH decreased and renal net acid excretion increased. In the formulas PAM, P2 and P3 differences in renal net acid excretion correlated with differences in chloride and sulfur contents of the diets and of the urines. New modifications of AlbumaidXP and of PAM, prepared according to our recommendations, showed normal renal net acid excretion (1 mEq/kg/24 hr) in a balance study performed in one patient with PKU and normal acid base status in 20 further patients.

  7. Students' Understanding of Acids/Bases in Organic Chemistry Contexts

    ERIC Educational Resources Information Center

    Cartrette, David P.; Mayo, Provi M.

    2011-01-01

    Understanding key foundational principles is vital to learning chemistry across different contexts. One such foundational principle is the acid/base behavior of molecules. In the general chemistry sequence, the Bronsted-Lowry theory is stressed, because it lends itself well to studying equilibrium and kinetics. However, the Lewis theory of…

  8. Potentiometric Acid-Base Titrations with Activated Graphite Electrodes

    NASA Astrophysics Data System (ADS)

    Riyazuddin, P.; Devika, D.

    1997-10-01

    Dry cell graphite (DCG) electrodes activated with potassium permanganate are employed as potentiometric indicator electrodes for acid-base titrations. Special attention is given to an indicator probe comprising activated DCG-non-activiated DCG electrode couple. This combination also proves suitable for the titration of strong or weak acids.

  9. Thymine, adenine and lipoamino acid based gene delivery systems.

    PubMed

    Skwarczynski, Mariusz; Ziora, Zyta M; Coles, Daniel J; Lin, I-Chun; Toth, Istvan

    2010-05-14

    A novel class of thymine, adenine and lipoamino acid based non-viral carriers for gene delivery has been developed. Their ability to bind to DNA by hydrogen bonding was confirmed by NMR diffusion, isothermal titration calorimetry and transmission electron microscopy experiments.

  10. Soil Studies: Applying Acid-Base Chemistry to Environmental Analysis.

    ERIC Educational Resources Information Center

    West, Donna M.; Sterling, Donna R.

    2001-01-01

    Laboratory activities for chemistry students focus attention on the use of acid-base chemistry to examine environmental conditions. After using standard laboratory procedures to analyze soil and rainwater samples, students use web-based resources to interpret their findings. Uses CBL probes and graphing calculators to gather and analyze data and…

  11. Acid-Base Disorders--A Computer Simulation.

    ERIC Educational Resources Information Center

    Maude, David L.

    1985-01-01

    Describes and lists a program for Apple Pascal Version 1.1 which investigates the behavior of the bicarbonate-carbon dioxide buffer system in acid-base disorders. Designed specifically for the preclinical medical student, the program has proven easy to use and enables students to use blood gas parameters to arrive at diagnoses. (DH)

  12. Using Spreadsheets to Produce Acid-Base Titration Curves.

    ERIC Educational Resources Information Center

    Cawley, Martin James; Parkinson, John

    1995-01-01

    Describes two spreadsheets for producing acid-base titration curves, one uses relatively simple cell formulae that can be written into the spreadsheet by inexperienced students and the second uses more complex formulae that are best written by the teacher. (JRH)

  13. Waterflooding employing mixtures of sulfonate surfactants

    SciTech Connect

    Savins, J.G.; Waite, J.M.; Burdyn, R.F.

    1980-11-04

    A new waterflooding process is described in which at least a portion of the injected fluid comprises a viscous aqueous liquid having a monovalent salt salinity within the range of 1.5 to 4.0% by wt and containing first and second sulfonate surfactants. The first surfactant is a petroleum sulfonate having a relatively broad molecular weight distribution and the second surfactant is a synthetic alkyl or alkylaryl sulfonate having a molecular weight distribution narrower than that of the first surfactant. The first and second surfactants are present in the aqueous liquid in relative amounts such that the ratio of the concentration of the first surfactant to the concentration of the second surfactant is within the range of 1:3 to 1:1. The thickened aqueous liquid containing the above described multicomponent surfactant system also contains a water-soluble C3-C6 aliphatic alcohol. 11 claims.

  14. Schiff base structured acid-base cooperative dual sites in an ionic solid catalyst lead to efficient heterogeneous knoevenagel condensations.

    PubMed

    Zhang, Mingjue; Zhao, Pingping; Leng, Yan; Chen, Guojian; Wang, Jun; Huang, Jun

    2012-10-01

    An acid-base bifunctional ionic solid catalyst [PySaIm](3)PW was synthesized by the anion exchange of the ionic-liquid (IL) precursor 1-(2-salicylaldimine)pyridinium bromide ([PySaIm]Br) with the Keggin-structured sodium phosphotungstate (Na(3) PW). The catalyst was characterized by FTIR, UV/Vis, XRD, SEM, Brunauer-Emmett-Teller (BET) theory, thermogravimetric analysis, (1)H NMR spectroscopy, ESI-MS, elemental analysis, and melting points. Together with various counterparts, [PySaIm](3)PW was evaluated in Knoevenagel condensation under solvent and solvent-free conditions. The Schiff base structure attached to the IL cation of [PySaIm](3)PW involves acidic salicyl hydroxyl and basic imine, and provides a controlled nearby position for the acid-base dual sites. The high melting and insoluble properties of [PySaIm](3)PW are relative to the large volume and high valence of PW anions, as well as the intermolecular hydrogen-bonding networks among inorganic anions and IL cations. The ionic solid catalyst [PySaIm](3)PW leads to heterogeneous Knoevenagel condensations. In solvent-free condensation of benzaldehyde with ethyl cyanoacetate, it exhibits a conversion of 95.8 % and a selectivity of 100 %; the conversion is even much higher than that (78.2 %) with ethanol as a solvent. The solid catalyst has a convenient recoverability with only a slight decrease in conversion following subsequent recyclings. Furthermore, the new catalyst is highly applicable to many substrates of aromatic aldehydes with activated methylene compounds. On the basis of the characterization and reaction results, a unique acid-base cooperative mechanism within a Schiff base structure is proposed and discussed, which thoroughly explains not only the highly efficient catalytic performance of [PySaIm](3)PW, but also the lower activities of various control catalysts.

  15. Adsorption of β-casein-surfactant mixed layers at the air-water interface evaluated by interfacial rheology.

    PubMed

    Maestro, Armando; Kotsmar, Csaba; Javadi, Aliyar; Miller, Reinhard; Ortega, Francisco; Rubio, Ramón G

    2012-04-26

    This work presents a detailed study of the dilational viscoelastic moduli of the adsorption layers of the milk protein β-casein (BCS) and a surfactant at the liquid/air interface, over a broad frequency range. Two complementary techniques have been used: a drop profile tensiometry technique and an excited capillary wave method, ECW. Two different surfactants were studied: the nonionic dodecyldimethylphosphine oxide (C12DMPO) and the cationic dodecyltrimethylammonium bromide (DoTAB). The interfacial dilational elasticity and viscosity are very sensitive to the composition of protein-surfactant mixed adsorption layers at the air/water interface. Two different dynamic processes have been observed for the two systems studied, whose characteristic frequencies are close to 0.01 and 100 Hz. In both systems, the surface elasticity was found to show a maximum when plotted versus the surfactant concentration. However, at frequencies above 50 Hz the surface elasticity of BCS + C12DMPO is higher than the one of the aqueous BCS solution over most of the surfactant concentration range, whereas for the BCS + DoTAB it is smaller for high surfactant concentrations and higher at low concentrations. The BCS-surfactant interaction modifies the BCS random coil structure via electrostatic and/or hydrophobic interactions, leading to a competitive adsorption of the BCS-surfactant complexes with the free, unbound surfactant molecules. Increasing the surfactant concentration decreases the adsorbed proteins. However, the BCS molecules are rather strongly bound to the interface due to their large adsorption energy. The results have been fitted to the model proposed by C. Kotsmar et al. ( J. Phys. Chem. B 2009 , 113 , 103 ). Even though the model describes well the concentration dependence of the limiting elasticity, it does not properly describe its frequency dependence.

  16. Biofoams and natural protein surfactants

    PubMed Central

    Cooper, Alan; Kennedy, Malcolm W.

    2010-01-01

    Naturally occurring foam constituent and surfactant proteins with intriguing structures and functions are now being identified from a variety of biological sources. The ranaspumins from tropical frog foam nests comprise a range of proteins with a mixture of surfactant, carbohydrate binding and antimicrobial activities that together provide a stable, biocompatible, protective foam environment for developing eggs and embryos. Ranasmurfin, a blue protein from a different species of frog, displays a novel structure with a unique chromophoric crosslink. Latherin, primarily from horse sweat, but with similarities to salivary, oral and upper respiratory tract proteins, illustrates several potential roles for surfactant proteins in mammalian systems. These proteins, together with the previously discovered hydrophobins of fungi, throw new light on biomolecular processes at air–water and other interfaces. This review provides a perspective on these recent findings, focussing on structure and biophysical properties. PMID:20615601

  17. Effect of Different Surfactants on the Interfacial Behavior of the n-Hexane-Water System in the Presence of Silica Nanoparticles.

    PubMed

    Biswal, Nihar Ranjan; Rangera, Naveen; Singh, Jayant K

    2016-07-28

    This paper presents the effect of negatively charged silica nanoparticles (NPs) on the interfacial tension of the n-hexane-water system at variable concentrations of four different surfactants, viz., an anionic surfactant, sodium dodecyl sulfate (SDS), a cationic surfactant, cetyltrimethylammonium bromide (CTAB), and two nonionic surfactants, Tween 20 and Triton X-100 (TX-100). The presence of negatively charged silica nanoparticles is found to have a different effect depending on the type of surfactant. In the case of ionic surfactants, SDS and CTAB, silica NPs reduce the interfacial tension of the system. On the contrary, for nonionic surfactants, Tween 20 and TX-100, silica NPs increase the interfacial tension. The increasing/decreasing nature of the interfacial tension in the presence of NPs is well supported by the calculated surface excess concentrations. The diffusion kinetic control (DKC) and statistical rate theory (SRT) models are used to understand the behavior of dynamic interfacial tension of the surfactant-NP-oil-water system. The DKC model is found to describe the studied surfactant-NP-oil-water systems more aptly. PMID:27367433

  18. Size-dependent interaction of silica nanoparticles with different surfactants in aqueous solution.

    PubMed

    Kumar, Sugam; Aswal, Vinod K; Kohlbrecher, Joachim

    2012-06-26

    The size-dependent interaction of anionic silica nanoparticles with ionic (anionic and cationic) and nonionic surfactants has been studied using small-angle neutron scattering (SANS). The surfactants used are anionic sodium dodecyl sulfate (SDS), cationic dodecyltrimethyl ammonium bromide (DTAB), and nonionic decaoxyethylene n-dodecylether (C(12)E(10)). The measurements have been carried out for three different sizes of silica nanoparticles (8, 16, and 26 nm) at fixed concentrations (1 wt % each) of nanoparticles and surfactants. It is found that irrespective of the size of the nanoparticles there is no significant interaction evolved between like-charged nanoparticles and the SDS micelles leading to any structural changes. However, the strong attraction of oppositely charged DTAB micelles with silica nanoparticles results in the aggregation of nanoparticles. The number of micelles mediating the nanoparticle aggregation increases with the size of the nanoparticle. The aggregates are characterized by fractal structure where the fractal dimension is found to be constant (D ≈ 2.3) independent of the size of the nanoparticles and consistent with diffusion-limited-aggregation-type fractal morphology in these systems. In the case of nonionic surfactant C(12)E(10), micelles interact with the individual silica nanoparticles. The number of adsorbed micelles per nanoparticle increases drastically whereas the percentage of adsorbed micelles on nanoparticles decreases with the increase in the size of the nanoparticles. PMID:22655980

  19. Controlling the morphology of membranes by excess surface charge in cat-anionic fluorinated surfactant mixtures.

    PubMed

    Shen, Yuwen; Ou-Yang, Zhong-can; Zhang, Yufeng; Hao, Jingcheng; Liu, Zhaohui

    2014-03-18

    The segregation and phase sequence of semifluorinated cat-anionic surfactant membranes at different excess surface charges was investigated by freeze-fracture transmission electron microscope (FF-TEM), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR). The thermal behavior of the membranes was evaluated by conductivity, rheology, and deuterium nuclear magnetic resonance ((2)H NMR). The experimental results show that the cat-anionic fluorinated surfactant mixtures can form faceted vesicles and punctured lamellar phase when there is excess surface charge. The cationic and anionic fluorinated surfactants are stiff in the membranes, like phospholipids in the frozen "crystalline" or "gel" phase. For the system with excess cationic surface charge, the gel-like faceted vesicles and punctured lamellae can transform into smooth-shaped vesicles at 65 °C. However, for the system with no excess charge or with excess anionic surface charge, no phase transformation occurs even at 90 °C. A model was established to demonstrate the mechanism of the formation and transition of the aggregates with different morphologies. The segregation-crystallization mechanism works well with other cosmotropic counterions from the Hofmeister series. The observations provide a better understanding of how to control the membrane morphology of the aqueous solutions of cat-anionic surfactant mixtures.

  20. Inhibition of lipase-catalyzed hydrolysis of emulsified triglyceride oils by low-molecular weight surfactants under simulated gastrointestinal conditions.

    PubMed

    Li, Yan; McClements, David Julian

    2011-10-01

    The effect of low-molecular weight surfactants on the digestibility of lipids in protein-stabilized corn oil-in-water emulsions was studied using an in vitro digestion model. The impact of non-ionic (Tween 20, Tween 80, Brij35), anionic (SDS), and cationic (DTAB) surfactants on the rate and extent of lipid digestion was studied. All surfactants were found to inhibit lipid digestion at sufficiently high concentrations, with half-maximal inhibitory concentrations (IC50) of 1.2% for Tween 20, 0.7% for Tween 80, 2.8% for Brij35, 1.1% for SDS, and 1.4% for DTAB. The effectiveness of the surfactants at inhibiting lipid digestion was therefore not strongly correlated to the electrical characteristics of the surfactant head group, since the IC50 increased in the following order: Tween 80>SDS>Tween 20>DTAB>Brij35. The ability of these low-molecular weight surfactants to inhibit lipid digestion was attributed to a number of potential mechanisms: (i) prevention of lipase/co-lipase adsorption to the oil-water interface; (ii) formation of interfacial complexes; (iii) direct interaction and inactivation of lipase/co-lipase. Interestingly, DTAB increased the rate and extent of lipid digestion when present at relatively low concentrations. This may have been because this cationic surfactant facilitated the adsorption of lipase to the droplet surfaces through electrostatic attraction, or it bound directly to the lipase molecule thereby changing its structure and activity. A number of the surfactants themselves were found to be susceptible to enzyme digestion by pancreatic enzymes in the absence of lipids: Tween 20, Tween 80, Brij35, and DTAB. This work has important implications for the development of emulsion-based delivery systems for food and pharmaceutical applications.