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Sample records for aot reverse micelles

  1. Ultrafast energy transfer in water-AOT reverse micelles

    NARCIS (Netherlands)

    Cringus, Dan; Bakulin, Artem; Lindner, Joerg; Voehringer, Peter; Pshenichnikov, Maxim S.; Wiersma, Douwe A.

    2007-01-01

    A spectroscopic investigation of the vibrational dynamics of water in a geometrically confined environment is presented. Reverse micelles of the ternary microemulsion H2O/AOT/n-octane (AOT = bis-2-ethylhexyl sulfosuccinate or aerosol-OT) with diameters ranging from 1 to 10 nm are used as a model sys

  2. Photophysical properties of pyronin dyes in reverse micelles of AOT

    International Nuclear Information System (INIS)

    The photophysical properties of pyronin B (PyB) and pyronin Y (PyY) in reverse micelles formed with water/sodium bis (2-ethyl-1-hexyl) sulfosuccinate (AOT)/n-heptane were investigated by UV–vis absorption, steady-state and time-resolved fluorescence spectroscopy techniques. This study was carried out a wide range of reverse micelle sizes, with hydrodynamic radii ranging from 1.85 to 9.38 nm. Significant photophysical parameters as band shifts, fluorescence quantum yields and fluorescence lifetimes were determined to understand how photophysical and spectroscopic features of the dye compounds were affected by the variation of reverse micelle sizes. In this regard, control of reverse micelle size by changing W0, the molar ratio of water to surfactant, allowed tuning the photophysical properties of the dyes in organic solvent via reverse micelle. Non-fluorescent H-aggregates of pyronin dyes were observed for the smaller reverse micelles whereas an increase in the reverse micelle size induced an increment in the amount of dye monomers instead of dye aggregates. Thus, the fluorescence intensities of the dyes were improved by increasing W0 due to the predomination of the fluorescent dye monomers. As a result, the fluorescence quantum yields also increased. The fluorescence lifetimes of the dyes in the reverse micelles were determined by the time-resolved fluorescence decay studies. Evaluation of the fluorescence lifetimes calculated for pyronin dyes in the reverse micelles showed that the size of reverse micelle affected the fluorescence lifetimes of pyronin dyes. -- Highlights: • The photophysical properties of pyronin dyes were examined by spectroscopic techniques. • Optical properties of the dyes were tuned by changing of W0 values. • The fluorescence lifetime and quantum yield values of the dyes in reverse micelles were discussed

  3. Integral physicochemical properties of reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT)

    Science.gov (United States)

    Fedyaeva, O. A.; Shubenkova, E. G.; Poshelyuzhnaya, E. G.; Lutaeva, I. A.

    2016-08-01

    The effect the degree of hydration has on optical and electrophysical properties of water/AOT/ n-hexane system is studied. It is found that AOT reverse micelles form aggregates whose dimensions grow along with the degree of hydration and temperature. Aggregation enhances their electrical conductivity and shifts the UV spectrum of AOT reverse emulsions to the red region. Four states of water are found in the structure of AOT reverse micelles.

  4. Ultrafast energy transfer in water-AOT reverse micelles.

    Science.gov (United States)

    Cringus, Dan; Bakulin, Artem; Lindner, Jörg; Vöhringer, Peter; Pshenichnikov, Maxim S; Wiersma, Douwe A

    2007-12-27

    A spectroscopic investigation of the vibrational dynamics of water in a geometrically confined environment is presented. Reverse micelles of the ternary microemulsion H2O/AOT/n-octane (AOT = bis-2-ethylhexyl sulfosuccinate or aerosol-OT) with diameters ranging from 1 to 10 nm are used as a model system for nanoscopic water droplets surrounded by a soft-matter boundary. Femtosecond nonlinear infrared spectroscopy in the OH-stretching region of H2O fully confirms the core/shell model, in which the entrapped water molecules partition onto two molecular subensembles: a bulk-like water core and a hydration layer near the ionic surfactant headgroups. These two distinct water species display different relaxation kinetics, as they do not exchange vibrational energy. The observed spectrotemporal ultrafast response exhibits a local character, indicating that the spatial confinement influences approximately one molecular layer located near the water-amphiphile boundary. The core of the encapsulated water droplet is similar in its spectroscopic properties to the bulk phase of liquid water, i.e., it does not display any true confinement effects such as droplet-size-dependent vibrational lifetimes or rotational correlation times. Unlike in bulk water, no intermolecular transfer of OH-stretching quanta occurs among the interfacial water molecules or from the hydration shell to the bulk-like core, indicating that the hydrogen bond network near the H2O/AOT interface is strongly disrupted. PMID:18047308

  5. "Snap-shooting" the interface of AOT reverse micelles: use of chemical trapping

    Science.gov (United States)

    Srilakshmi; Chaudhuri

    2000-08-01

    The first use of the phenyl cation trapping technique in "snap-shooting" the local molar concentrations of water and sulfosuccinate head-groups in the interfacial region of AOT-2,2,4-trimethylpentane-water reverse micelles has been accomplished. Our results demonstrate that the interfacial concentrations of the sulfosuccinate head-groups in AOT (0.1 M)-2,2,4-trimethylpentane-water reverse micelles are remarkably high (2.75-2.34 M) across the W0 (the molar ratio of water to surfactant) range 12 to 44. However, the interfacial concentrations of water in AOT- 2,2,4-trimethylpentane-water reverse micelles across the same range of solution compositions are significantly lower (27.9-32.0 M) than the molar concentration of bulk water (55.5 M). The present results provide new insight on the microenvironments of interfacially located enzymes such as lipases entrapped in AOT-2,2,4-trimethylpentane-water reverse micelles, the most extensively exploited reverse-micellar system in micellar biotechnology. PMID:10985732

  6. Dynamics of electron attachment to AOT/H2O reversed micelles

    International Nuclear Information System (INIS)

    Values of the observed rate constant, κobs, of excess electrons attaching to aerosol OT (AOT) reversed micelles encapsulating varying quantities of water were measured in isooctane and tetramethylsilane (TMS) at 21 degrees C using a picosecond-pulse conductivity technique. Dynamic light scattering was used to determine the micellar radii in TMS from which aggregation numbers of the micelles were determined. In the lower-mobility isooctane (μe = 5.3 cm2/(V s)), values of the κobs approach the diffusion-controlled attachment rate, κobs in TMS (μ3 = 100 cm2/(V s)) are 8-fold less than κd at the maximum ratio of H2O/AOT = 27 that was studied. Several factors that could contribute to κobs appearing to exceed κd in isooctane are discussed, and the less efficient attachment of electrons to the same reversed micelles in TMS compared to attachment in isooctane is interpreted in terms of the relative attachment time, τr. With this model, the τa of electrons attaching to micelles at a diffusion-controlled rate is <1 ps and may be identified with the solvation time of electrons in water. 54 refs., 5 figs., 2 tabs

  7. Molecular Dynamics Simulations of Cytochrome c un-folding in AOT Reverse Micelles: the first steps

    CERN Document Server

    Abel, Stéphane; Marchi, Massimo

    2009-01-01

    This paper explores the reduced form of horse cytochrome c confined in reverse micelles (RM) of so-dium bis-(2-ethylhexyl) sulfosuccinate (AOT) in isooctane by molecular dynamics simulation. RMs of two sizes were constructed at a water content of Wo = [H2O]/[AOT] = 5.5 and 9.1. Our results show that the protein secondary structure and the heme conformation both depend on micellar hydration. At low hydration, the protein structure and the heme moiety remain stable, whereas at high water content the protein becomes unstable and starts to unfold. At Wo = 9.1, according to the X-ray structure, conforma-tional changes are mainly localized on protein loops and around the heme moiety, where we observe a partial opening of the heme crevice. These findings suggest that within our time window (10 ns), the structural changes observed at the heme level are the first steps of the protein denaturation process, pre-viously described experimentally in micellar solutions. In addition, a specific binding of AOT molecules to a ...

  8. Lipophilic porphyrin microparticles induced by AOT reverse micelles: a fluorescence lifetime imaging study.

    Science.gov (United States)

    Togashi, Denisio M; Costa, Sílvia M B; Sobral, Abílio J F N

    2006-01-20

    Fluorescence Lifetime Imaging Microscopy (FLIM) technique was applied to investigate the fluorescence dynamics and structural features of large colloidal aggregates of meso-tetra(N-dodecyl-4-amino sulfonyl-phenyl)porphyrin (PC12) induced by Sodium 1,4-bis(2-ethyl hexyl)sulfosuccinate (AOT) reverse micelles. The aggregate's particle sizes (down to 1 microm) obtained from the confocal fluorescence images matched with the particle sizes measured in the images obtained from Scanning Electron Microscopy (SEM). The fluorescence decays for those aggregates in the micro spatial domain show triexponential fluorescence lifetimes (tau1 approximately 12 ns, tau2 approximately 3 ns and tau3 approximately 1 ns) which are independent of the aggregate's size. PMID:16154681

  9. Effect of the constrained environment on the interactions between the surfactant and different polar solvents encapsulated within AOT reverse micelles.

    Science.gov (United States)

    Durantini, Andrés M; Falcone, R Dario; Silber, Juana J; Correa, N Mariano

    2009-08-24

    Herein, we report a study of the interactions between different nonaqueous polar solvents, namely, ethylene glycol (EG), propylene glycol (PG), glycerol (GY), dimethylformamide (DMF), and dimethylacetamide (DMA), and the polar heads of sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) in nonaqueous AOT/n-heptane reverse micelles. The goal of our study is to gain insights into the unique reverse-micelle microenvironment created upon encapsulation of these polar solvents. For the first time, the study is focused on determining which regions of the AOT molecular structure are involved in the interactions with the polar solvents. We use FTIR spectroscopy--a noninvasive technique--to follow the changes in the AOT C=O band and the symmetric and asymmetric SO(3)(-) vibration modes upon increasing the content of polar solvents in the micelles. The results show that GY interacts through H bonds with the SO(3)(-) group, thereby removing the Na(+) counterions from the interface remaining in the polar core of the micelles. PG and EG interact through H bonds, mainly with the C=O group of AOT, penetrating into the oil side of the interface. Thus, they interact weakly with the Na(+) counterion, which seems to be close to the AOT sulfonate group. Finally, DMF and DMA, encapsulated inside the reverse micelles, interact neither with the C=O nor with the SO(3)(-) groups, but their weakly bulk-associated structure is broken because of the interactions with Na(+). We suggest that DMF and DMA can complex the Na(+) ions through their carbonyl and nitrogen groups. Hence, our results do not only give insights into how the constrained environment affects the bulk properties of polar solvents encapsulated within reverse micelles but--more importantly--they also help us to answer the tricky question about which regions of the AOT moiety are involved in the interactions with the polar solvents. We believe that our results show a clear picture of the interactions present at the nonaqueous reverse-micelle

  10. More evidence on the control of reverse micelles sizes. Combination of different techniques as a powerful tool to monitor AOT reversed micelles properties.

    Science.gov (United States)

    Durantini, Andrés M; Falcone, R Darío; Silber, Juana J; Correa, N Mariano

    2013-04-11

    In this work, we have investigated the behavior of 4-aminophthalimide (4-AP) in solvent mixtures of ethyl lactate (EL)- water and EL-n-heptane and in reversed micelles (RMs) media made of EL-water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane. We have used dynamics light scattering (DLS) and absorption, steady-state and time-resolved emission (TRES) techniques. 4-AP is a very interesting and unique molecule used to study preferential solvation in water mixtures since its emission profile changes dramatically when its sphere shell is solvated by water molecules. Thus, in homogeneous media 4-AP is strongly solvated by water in the EL-water mixture and by EL in the EL-n-heptane mixture, results that show the importance of the hydrogen bonding in the 4-AP solvation. We were motivated by this feature of 4-AP and have used it to monitor properties in AOT RMs. Thus, we use 4-AP spectroscopic behavior in conjunction with DLS technique to reveal the location of each polar solvent of the mixture encapsulated within the RMs media. We found that in the EL-water/AOT/n-heptane RMs the results strongly depend on the amount of water dissolved. Below W0 = [water]/[AOT] = 5, there are no reversed micelles and EL, water, AOT and n-heptane forms a nonstructured mixture. For W0 values between 5 and 10, the droplet sizes are independent of the EL content because of its strong intermolecular interactions forms an EL polar core and only water is found at the interface. For W0 values higher than 10, the droplets size increase with the EL content and EL molecules are detected at the AOT RMs interface. We inferred that the RMs sizes will change only if the polar solvent encapsulated interacts with the interface changing the surfactant packing parameter. Then, we can assume that it is possible to create RMs with solvents that do not interact with the interface but can be encapsulated in the polar core. These results, give evidence that expand the knowledge about which are the

  11. Extraction of cobalt ion using reverse-micelle of F-AOT in liquid/supercritical CO2

    International Nuclear Information System (INIS)

    A green decontamination method using CO2 as an environmentally benign solvent has been studied for removal of contaminant in the nuclear power plant. We developed a decontamination technique using CO2 for removal of contamination in working dresses. Owing to the low solubilizing, A reverse micelle system was developed. Fluorinated AOT was synthesized and used as surfactants forming reverse-micelle with water. Cobalt was extracted by dissolution into reverse-micelle in liquid CO2. If this decontamination technique is applied to nuclear industry, the secondary waste during decontamination will be reverentially reduced. Negligibly small amount of water is a net waste, while the surfactants and solvent CO2 are recovered and reused in the system

  12. Real structure of formamide entrapped by AOT nonaqueous reverse micelles: FT-IR and 1H NMR studies.

    Science.gov (United States)

    Correa, N Mariano; Pires, Paulo Augusto R; Silber, Juana J; El Seoud, Omar A

    2005-11-10

    Noninvasive techniques such as FT-IR and (1)H NMR spectroscopy have been employed to investigate the solubilization of formamide, FA, and its aqueous solution, FA-water, by sodium 1,4-bis(2-ethylhexyl)sulfosuccinate, AOT, in heptane or isooctane reverse micelles, respectively. Partially deuterated FA (FADH) was used in the FT-IR experiments and nu(OD), n(ND) were analyzed. Also, the nu(C=O) band of FA was investigated. For AOT, the changes of the SO(3)(-) group's symmetric, nu(s), and asymmetric, nu(a), bands were also studied. The results are showing that FA is interacting strongly with the Na+ counterions of the surfactant through electrostatic interactions maintaining their hydrogen bond network present in the FA bulk. Accordingly, partially deuterated FA is "frozen" inside the aggregates and it is possible to detect, by FT-IR technique, the cis and trans isomers. Curve fitting of the nu(OD) (in the FA-water mixture) band requires use of two peaks because the band is asymmetric, not because the solubilizate molecules are present in layers of different structure. The chemical shifts of the (1)H bound to N and C of FA were studied by (1)H NMR. The comparison of the chemical shift of AOT in reverse micelles with FA and the FA-water mixture in the polar core of the aggregate shows that there is a strong preferential solvation of Na+ by FA (through electrostatic interaction) and the AOT's sulfonate group by water (through hydrogen bond interaction). PMID:16853748

  13. Kinetic Studies on the Lignin Peroxidase Catalyzed Oxidation of Veratryl Alcohol by H2O2 in AOT/Isooctane/Toluene/Water Reverse Micelles

    Institute of Scientific and Technical Information of China (English)

    LIU Jin-Ting; HUANG Xi-Rong; GAO Pei-ji

    2007-01-01

    The steady state kinetics of the lignin peroxidase (LIP) catalyzed oxidation of veratryl alcohol (VA) by H2O2 in a sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane/toluene/water reverse micellar medium was studied and a comparison with the corresponding aqueous medium was made to understand the effect of the reverse micellar medium on the catalytic mechanism and kinetic parameters. Results indicated that the model reaction in the AOT medium were the same as those in bulk aqueous medium, but the kinetic parameters except Km,H2O2 were greatly different in the two media. The kcat and Ki values in the reverse micelle were approximately 2 and 20 times smaller than the corresponding values in the aqueous solution, but the Michaelis constant of VA was approximately 100times greater than that in the aqueous solution. The above mentioned differences in the kinetic parameters were caused by the microheterogeneity and the interface of the AOT reverse micelle, which resulted in the partitioning of VA and H2O2, and by the changes of the conformation of LiP and the reactivity of the substrates.

  14. Activity, stability and kinetic parameters for -chymotrypsin catalysed reactions in AOT/isooctane reverse micelles with nonionic and zwitterionic mixed surfactants

    Indian Academy of Sciences (India)

    Santosh Kumar Verma; Kallol K Ghosh

    2013-07-01

    Reverse micelles (RMs) of sodium 1,4-bis(2-ethylhexyl)sulphosuccinate (AOT) in nonpolar organic solvents are widely known to have very high solubilization power for water. The method is applied to the hydrolysis of -nitrophenyl acetate (PNPA) catalysed by -chymotrypsin (-CT) in AOT/isooctane/buffer RMs. The increase in -CT activity and stability was an optimum at wo ([H2O]/[AOT]) = 10, z [Isooctane]/[AOT]) = 5. Three typical surfactants were selected based on their head group charges: a non-ionic surfactant Triton-X 100 and two zwitterionic sulphobetaine surfactants of the type CH2+1N+Me2 (CH2)3 SO$^{−}_{3}$ (n = 10; SB3-10, n = 16; SB3-16). The kinetic parameters (such as cat and M) of the -CT at 27°C were determined and compared in the absence and presence of three surfactants. The effect of chain length of zwitterionic surfactant (SB3-10 and SB3-16) on the enzymatic efficacy of -CT as a function of mixed surfactant addition has been investigated in AOT/isooctane RMs at pH 7.75.

  15. Correlation of insulin-enhancing properties of vanadium-dipicolinate complexes in model membrane systems: phospholipid langmuir monolayers and AOT reverse micelles.

    Science.gov (United States)

    Sostarecz, Audra G; Gaidamauskas, Ernestas; Distin, Steve; Bonetti, Sandra J; Levinger, Nancy E; Crans, Debbie C

    2014-04-22

    We explore the interactions of V(III) -, V(IV) -, and V(V) -2,6-pyridinedicarboxylic acid (dipic) complexes with model membrane systems and whether these interactions correlate with the blood-glucose-lowering effects of these compounds on STZ-induced diabetic rats. Two model systems, dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers and AOT (sodium bis(2-ethylhexyl)sulfosuccinate) reverse micelles present controlled environments for the systematic study of these vanadium complexes interacting with self-assembled lipids. Results from the Langmuir monolayer studies show that vanadium complexes in all three oxidation states interact with the DPPC monolayer; the V(III) -phospholipid interactions result in a slight decrease in DPPC molecular area, whereas V(IV) and V(V) -phospholipid interactions appear to increase the DPPC molecular area, an observation consistent with penetration into the interface of this complex. Investigations also examined the interactions of V(III) - and V(IV) -dipic complexes with polar interfaces in AOT reverse micelles. Electron paramagnetic resonance spectroscopic studies of V(IV) complexes in reverse micelles indicate that the neutral and smaller 1:1 V(IV) -dipic complex penetrates the interface, whereas the larger 1:2 V(IV) complex does not. UV/Vis spectroscopy studies of the anionic V(III) -dipic complex show only minor interactions. These results are in contrast to behavior of the V(V) -dipic complex, [VO2 (dipic)](-) , which penetrates the AOT/isooctane reverse micellar interface. These model membrane studies indicate that V(III) -, V(IV) -, and V(V) -dipic complexes interact with and penetrate the lipid interfaces differently, an effect that agrees with the compounds' efficacy at lowering elevated blood glucose levels in diabetic rats. PMID:24615733

  16. Electron-transfer reactions between viologen radical cations and quinones in AOT reverse micelles studied by electron pulse radiolysis

    International Nuclear Information System (INIS)

    Electron-transfer reactions between viologen radical cations (CnVsm-bullet+, n = 1-18) and various quinones have been studied in aqueous and reverse micellar (AOT/isooctane/H2O) solution by use of the electron pulse radiolysis technique. By use of dynamic light scattering measurements, the concentration of water pools was determined and the number of electron-transfer reactants per water pool could be calculated. Rate constants measured for the reaction between CnVsm-bullet+ radicals and anthraquinonesulfonate ions (AQS-) decreased with increasing length of the aliphatic chain of the viologens, caused by association of the viologen with the surfactant interface

  17. Photoluminescence and chemical properties of ZnS:Mn2+ nanocrystal powder synthesized in the AOT reverse micelles modified with lauryl phosphate

    International Nuclear Information System (INIS)

    A transparent colloidal solution of the ZnS:Mn2+ nanocrystal was prepared in hybrid reverse micelles comprising two kinds of surfactants: sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and lauryl phosphate (HLP). Then, the powdered sample was obtained from the colloidal solution by coagulation of these micelles. Modification of HLP surfactant increases the photoluminescence (PL) intensity due to the d-d transition of Mn2+ ions for both of the colloidal solution and the powder. FT-IR spectra and energy dispersive X-ray analysis (EDX) data reveal that HLP modifies ZnS:Mn2+ nanocrystals more preferentially than AOT. The detailed investigation on chemical interaction between HLP molecules and ZnS nanocrystals with and without Mn2+ is performed by solid-state nuclear magnetic resonance (NMR) techniques of 31P inversion recovery and 1H →31P cross-polarization (CP) in a magnetic field of 11.7 T using magic angle spinning (MAS) at a high spinning rate of 19 and 28 kHz, respectively. These NMR results suggest that most of HLP molecules strongly interact with nanocrystals through coordination bonds and/or hydrogen bonds

  18. Exploring the role of hydration and confinement in the aggregation of amyloidogenic peptides Aβ(16-22) and Sup35(7-13) in AOT reverse micelles.

    Science.gov (United States)

    Martinez, Anna Victoria; Małolepsza, Edyta; Rivera, Eva; Lu, Qing; Straub, John E

    2014-12-14

    Knowledge of how intermolecular interactions of amyloid-forming proteins cause protein aggregation and how those interactions are affected by sequence and solution conditions is essential to our understanding of the onset of many degenerative diseases. Of particular interest is the aggregation of the amyloid-β (Aβ) peptide, linked to Alzheimer's disease, and the aggregation of the Sup35 yeast prion peptide, which resembles the mammalian prion protein linked to spongiform encephalopathies. To facilitate the study of these important peptides, experimentalists have identified small peptide congeners of the full-length proteins that exhibit amyloidogenic behavior, including the KLVFFAE sub-sequence, Aβ16-22, and the GNNQQNY subsequence, Sup357-13. In this study, molecular dynamics simulations were used to examine these peptide fragments encapsulated in reverse micelles (RMs) in order to identify the fundamental principles that govern how sequence and solution environment influence peptide aggregation. Aβ16-22 and Sup357-13 are observed to organize into anti-parallel and parallel β-sheet arrangements. Confinement in the sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles is shown to stabilize extended peptide conformations and enhance peptide aggregation. Substantial fluctuations in the reverse micelle shape are observed, in agreement with earlier studies. Shape fluctuations are found to facilitate peptide solvation through interactions between the peptide and AOT surfactant, including direct interaction between non-polar peptide residues and the aliphatic surfactant tails. Computed amide I IR spectra are compared with experimental spectra and found to reflect changes in the peptide structures induced by confinement in the RM environment. Furthermore, examination of the rotational anisotropy decay of water in the RM demonstrates that the water dynamics are sensitive to the presence of peptide as well as the peptide sequence. Overall, our results

  19. USPIO assisting degradation of MXC by host/guest-type immobilized laccase in AOT reverse micelle system.

    Science.gov (United States)

    Yang, Yu-Xiang; Pi, Na; Zhang, Jian-Bo; Huang, Yan; Yao, Ping-Ping; Xi, Yan-Jie; Yuan, Hong-Ming

    2016-07-01

    The laccase and ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) have been assembled inside the tubular mesoporous silica via co-adsorption technology to prepare host/guest-type immobilized laccase, which is applied to degrade methoxychlor (MXC) in aqueous and reverse micelle environments. The effects of various parameters on degradation of MXC were studied. Under the optimum conditions, the degradation rate could reach maximum value of 45.6 % and remain at 20.8 % after seven cycles. Moreover, the addition of small molecular compound 2, 2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) to the system could greatly improve the degradation efficiency. The MXC degradation process is a first-order reaction, and the activation energy of MXC degradation catalyzed by immobilized laccase (41.46 kJ mol(-1)) is relatively lower than that catalyzed by free laccase (44.91 kJ mol(-1)). Based on the degradation products measured by gas chromatograph-mass spectrometer (GC-MS) and nuclear magnetic resonance (NMR), the degradation mechanism of MXC has also been proposed. PMID:27023821

  20. Factors Affecting Trypsin Extraction by AOT Reversed Micelles and Observation by STM%AOT反胶束萃取胰蛋白酶的STM及主要影响因素

    Institute of Scientific and Technical Information of China (English)

    周小华; 翁亚军

    2006-01-01

    In this article, the influence factors of trypsin extracted from crude pancreatin was investigated, and scanning tunneling microscope(STM) was used to observe the image of trypsin in butane-diacid-2-ethyl-hexyl-ester-sulfonic sodium (AOT)/iso-octane reversed micelles. The STM image showed that trypsins bounded in reversed micelles was rigid, which weakened its conjugative effect and caused maximum ultraviolet absorption and fluorescence emissive absorption moving toward blue waves. AOT concentration, pH and cations were the main influence factors of extraction. Specifically, extraction percentage of trypsin decreased with the increase of AOT concentration from 0.01 to 0.1mol·L-1. When pH value is from 5.30 to 10.0, i.e. less than pI of trypsin, the extraction percentage is raised with the different increase of pI-pH, but when the pH value is less than 5.20, the extraction percentage is decreased with the acidity added. Besides, the extraction efficiency is negative, related with the concentrations of Ca2+, Na+,K+ which were in the range of 0.2-1.0mol· L-1, and influence of concentration of Ca2+ is greater than that of Na+, and K+ which has the minimum impact with the same concentration. Finally, optimum conditions to extract trypsin were: AOT reversed micelles 0.05mol·L-1, trypsin concentration in crude pancreatin solution 3mg·ml-1, pH 5.2- 5.3, ratio (by volume) of extraction phase to strip-extraction phase 1:1, and time of 5min. The corresponding percentage of extraction was 22.7% and specific activity was 78.9 N-benzoyl-L-arginine ethyl ester (BAEE) U·mg-1 protein, three times than that in crude pancreatin. There was no lipase and amylopsin activity was decreased to 1/5 of crude pancreatin. Partly purifying solution was treated by condition mentioned above with 0.05mol·L-1 ceryl-trimethyl-ammonium bromide (CTAB), total extraction percentage of trypsin was 74.18% and specific activity was 3148.3 BAEE U·mg-1, i.e. 48.16 times purer than that in crude

  1. Absorption Complex between Porphyrin and Phenothiazine in Reverse Micelles

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The interaction between amphiphilic porphyrin and phenothiazine in AOT/isooctane/ water reverse micelle was investigated by UV-Vis spectra. A new absorption complex between the two species is formed in such circumstances, which is ascribed to the enrichment of the components by the reverse micelle. The fluorescence quenching of CHTTP by PTH becomes more efficient after the formation of the absorption complex.

  2. Electron capture in water pools of reversed micelles

    International Nuclear Information System (INIS)

    The rate constants of excess electron attachment to reversed H2O-AOT micelles in liquid isooctane were measured by a picosecond pulse-conductivity technique at 220C. Electron attachment rates were less than the diffusion-controlled rate at molar ratios ω0 =[H2O]/[AOT] less than 12 but increased to the diffusion-controlled rate of approx. 1015M-1s-1 at ω0 = 37 where the micelle radius was approx. 100A. The transition from nondiffusion-controlled to diffusion-controlled electron attachment implies that free or non-AOT bound water in the micellar water pools is required for efficient electron attachment, which is consistent with earlier NMR, fluorescence, and polarization studies of electron capture by reversed H2O-AOT micelles

  3. Biosensors with reversed micelle-enzyme sensitive membrane

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The effect of reversed micelle on the conformation of enzyme was studied by sensor techniques. By means of measurement of the response current of GOD enzyme membrane electrode, the effects of enzyme embedded in AOT reversed micellar on GOD conformation and catalytic activity are discussed. The results show that the response current increased greatly with decreasing ratio of GOD/AOT, meaning that the catalytic activity and the conformation stability of enzyme were enhanced.

  4. Use of reverse micelles in membrane protein structural biology

    International Nuclear Information System (INIS)

    Membrane protein structural biology is a rapidly developing field with fundamental importance for elucidating key biological and biophysical processes including signal transduction, intercellular communication, and cellular transport. In addition to the intrinsic interest in this area of research, structural studies of membrane proteins have direct significance on the development of therapeutics that impact human health in diverse and important ways. In this article we demonstrate the potential of investigating the structure of membrane proteins using the reverse micelle forming surfactant dioctyl sulfosuccinate (AOT) in application to the prototypical model ion channel gramicidin A. Reverse micelles are surfactant based nanoparticles which have been employed to investigate fundamental physical properties of biomolecules. The results of this solution NMR based study indicate that the AOT reverse micelle system is capable of refolding and stabilizing relatively high concentrations of the native conformation of gramicidin A. Importantly, pulsed-field-gradient NMR diffusion and NOESY experiments reveal stable gramicidin A homodimer interactions that bridge reverse micelle particles. The spectroscopic benefit of reverse micelle-membrane protein solubilization is also explored, and significant enhancement over commonly used micelle based mimetic systems is demonstrated. These results establish the effectiveness of reverse micelle based studies of membrane proteins, and illustrate that membrane proteins solubilized by reverse micelles are compatible with high resolution solution NMR techniques

  5. Use of reverse micelles in membrane protein structural biology

    Energy Technology Data Exchange (ETDEWEB)

    Van Horn, Wade D. [Vanderbilt University School of Medicine, Department of Biochemistry and Center for Structural Biology (United States); Ogilvie, Mark E.; Flynn, Peter F. [University of Utah, Department of Chemistry (United States)], E-mail: peter.flynn@utah.edu

    2008-03-15

    Membrane protein structural biology is a rapidly developing field with fundamental importance for elucidating key biological and biophysical processes including signal transduction, intercellular communication, and cellular transport. In addition to the intrinsic interest in this area of research, structural studies of membrane proteins have direct significance on the development of therapeutics that impact human health in diverse and important ways. In this article we demonstrate the potential of investigating the structure of membrane proteins using the reverse micelle forming surfactant dioctyl sulfosuccinate (AOT) in application to the prototypical model ion channel gramicidin A. Reverse micelles are surfactant based nanoparticles which have been employed to investigate fundamental physical properties of biomolecules. The results of this solution NMR based study indicate that the AOT reverse micelle system is capable of refolding and stabilizing relatively high concentrations of the native conformation of gramicidin A. Importantly, pulsed-field-gradient NMR diffusion and NOESY experiments reveal stable gramicidin A homodimer interactions that bridge reverse micelle particles. The spectroscopic benefit of reverse micelle-membrane protein solubilization is also explored, and significant enhancement over commonly used micelle based mimetic systems is demonstrated. These results establish the effectiveness of reverse micelle based studies of membrane proteins, and illustrate that membrane proteins solubilized by reverse micelles are compatible with high resolution solution NMR techniques.

  6. Enzyme recovery using reversed micelles.

    OpenAIRE

    Dekker, M.

    1990-01-01

    The objective of this study was to develop a liquid-liquid extraction process for the recovery of extracellular enzymes. The potentials of reaching this goal by using reversed micelles in an organic solvent have been investigated.Reversed micelles are aggregates of surfactant molecules containing an inner core of water molecules, dispersed in a continuous organic solvent medium. The considerable biotechnological potential of these systems is derived principally from the ability of the water d...

  7. Extraction of lysozyme, alpha-chymotrypsin, and pepsin into reverse micelles formed using an anionic surfactant, isooctane, and water.

    Science.gov (United States)

    Chang, Q; Liu, H; Chen, J

    1994-11-01

    The extraction of lysozyme, alpha-chymotrypsin, and pepsin from buffered salt solutions into reverse micelles was examined at different pH values and surfactant concentrations. The reverse micelles was formed by mixing aqueous buffer supplemented with KCl and an organic phase of isooctane(2,2,4-trimethylpentane), containing the anionic surfactant, Aerosol O. T. (dioctyl ester of sodium sulfosuccinic acid). The technique of dynamic laser scattering was used to measure the size of reverse micelles which were in equilibrium with the aqueous phase. It was found that the size of the reverse micelles decreased with increasing ionic strength but increased with increasing AOT concentration. In the process of extraction, the reverse micelles might have rearranged themselves to host the protein. The sizes of protein-filled and -unfilled reverse micelles were different, and an open equilibrium could be reached between them. Under the extraction conditions, only a small number of micelles were found to contain protein. PMID:7522474

  8. Reverse micelles extraction of nattokinase: From model system to real system

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nattokinase is a novel fibrinolytic enzyme, which is homologous to Subtilisin Carlsberg. In this paper, Subtilisin Carlsberg was taken as a model protein of nattokinase. Effects of pH, ionic strength, concentration of isopropanol on the extraction of Subtilisin Carlsberg with AOT/isooctane reverse micelles system were investigated. Further, the process of reverse micelles extraction of nattokinase from fermentation broth was studied. By taking the reverse micelles of AOT/isooctane as extractant to perform a full extraction cycle, it was found that about eighty percent of the total activity of nattokinase in the fermentation broth could be recovered and the purification factor was about 2.5. Homologous protein could be reasonably used as model protein of a target protein.

  9. Formation of reverse micelles in supercritical carbon dioxide and its thermodynamics

    Institute of Scientific and Technical Information of China (English)

    WEN Zhen; DANG Zhi; ZONG Minhua; ZHU Zhixin

    2007-01-01

    The solubilization behavior of methyl orange as a solvation probe in multiple systems composed of supercritical carbon dioxide,surfactants and co-solvents,is studied.It is coneluded that some surfactants,such as sodium bis-(2-ethylhexyl)sulfosuccinate(AOT)and isooctyl phenol polyethoxylate (TX-10),could form reverse micelles in supercritical carbon dioxide under the action of butanol.The formation of reverse micelles is a spontaneous process thermodynamically.Specifically for the nonionic surfactant TX-10,the formation of reverse micelles is dependent on the entropy increase in the system,while for the anionic surfactant AOT,the micellization is mainly dominated by the increase in enthalpy at higher temperatures,but by the increase in entropy at lower temperatures.

  10. Proton transfer in ionic and neutral reverse micelles.

    Science.gov (United States)

    Lawler, Christian; Fayer, Michael D

    2015-05-14

    Proton-transfer kinetics in both ionic and neutral reverse micelles were studied by time-correlated single-photon counting investigations of the fluorescent photoacid 8-hydroxypyrene-1,3,6-trisulfonate (HPTS). Orientational dynamics of dissolved probe molecules in the water pools of the reverse micelles were also investigated by time-dependent fluorescence anisotropy measurements of MPTS, the methoxy derivative of HPTS. These experiments were compared to the same experiments in bulk water. It was found that in ionic reverse micelles (surfactant Aerosol OT, AOT), orientational motion (fluorescence anisotropy decay) of MPTS was relatively unhindered, consistent with MPTS being located in the water core of the reverse micelle away from the water-surfactant interface. In nonionic reverse micelles (surfactant Igepal CO-520, Igepal), however, orientational anisotropy displayed a slow multiexponential decay consistent with wobbling-in-a-cone behavior, indicating MPTS is located at the water-surfactant interface. HPTS proton transfer in ionic reverse micelles followed kinetics qualitatively like those in bulk water, albeit slower, with the long-time power law time dependence associated with recombination of the proton with the dissociated photoacid, suggesting a modified diffusion-controlled process. However, the power law exponents in the ionic reverse micelles are smaller (∼ -0.55) than that in bulk water (-1.1). In neutral reverse micelles, proton-transfer kinetics did not show discernible power law behavior and were best represented by a two-component model with one relatively waterlike population and a population with a faster fluorescence lifetime and negligible proton transfer. We explain the Igepal results on the basis of close association between the probe and the neutral water-surfactant interface, with the probe experiencing a distribution of more and less waterlike environments. In addition, the observation in bulk water of a power law t(-1.1) for diffusion

  11. Nitrile group as infrared probe for the characterization of the conformation of bovine serum albumin solubilized in reverse micelles

    Science.gov (United States)

    Xue, Luyan; Zou, Feixue; Zhao, Yin; Huang, Xirong; Qu, Yinbo

    2012-11-01

    Infrared spectroscopy is a powerful technique for structure characterization. For a protein hosted in a reversed micellar medium, the spectral features of the protein are always interfered by the IR absorption bands of the medium in addition to the congestion in their IR spectra. Fortunately, there is a transparent window in the 2500-2200 cm-1 region. Incorporation of a vibrational probe with IR absorption frequencies in this region into proteins represents a promising strategy for the study of the conformation of a protein in a reverse micelle. In the present work, we incorporated 4-cyanobenzyl group (CN) into bovine serum albumin (BSA) via cysteine alkylation reactions under mild conditions. Circular dichroism spectroscopy showed that the Ctbnd N modified BSA (CNBSA) could retain its conformation. When CNBSA was hosted in AOT reverse micelle, it was found that the nitrile group on BSA was sensitive to the conformational change of BSA induced by urea as an additive in the reverse micelle. The peak splitting of nitrile group was also observed when the size of AOT reverse micelle and the concentration of an electrolyte were varied. Obviously, the shift of the IR absorption peak and/or peak splitting of nitrile group on BSA are correlated with the change of BSA conformation in AOT reverse micelle. So we conclude that the nitrile infrared probe can be used to study protein conformation in a reverse micelle.

  12. Chemical reactions in reverse micelle systems

    Science.gov (United States)

    Matson, Dean W.; Fulton, John L.; Smith, Richard D.; Consani, Keith A.

    1993-08-24

    This invention is directed to conducting chemical reactions in reverse micelle or microemulsion systems comprising a substantially discontinuous phase including a polar fluid, typically an aqueous fluid, and a microemulsion promoter, typically a surfactant, for facilitating the formation of reverse micelles in the system. The system further includes a substantially continuous phase including a non-polar or low-polarity fluid material which is a gas under standard temperature and pressure and has a critical density, and which is generally a water-insoluble fluid in a near critical or supercritical state. Thus, the microemulsion system is maintained at a pressure and temperature such that the density of the non-polar or low-polarity fluid exceeds the critical density thereof. The method of carrying out chemical reactions generally comprises forming a first reverse micelle system including an aqueous fluid including reverse micelles in a water-insoluble fluid in the supercritical state. Then, a first reactant is introduced into the first reverse micelle system, and a chemical reaction is carried out with the first reactant to form a reaction product. In general, the first reactant can be incorporated into, and the product formed in, the reverse micelles. A second reactant can also be incorporated in the first reverse micelle system which is capable of reacting with the first reactant to form a product.

  13. Ramping of pH Across the Water-Pool of a Reverse Micelle.

    Science.gov (United States)

    Mukherjee, Puspal; Gupta, Shradhey; Rafiq, Shahnawaz; Yadav, Rajeev; Jain, Vipin Kumar; Raval, Jayraj; Sen, Pratik

    2016-02-23

    In this work, we have addressed the problem of "acidity" of the water-pool of a reverse micelle (RM) through the well-known inversion of sucrose reaction as a tool of investigation. This reaction has been performed inside positively and negatively charged RM and the rates are compared with that in bulk water. We propose that the buffer-like action in a water-pool is much stronger than expected earlier. The rate of sucrose hydrolysis slowed down in the negatively charged AOT reverse micelle while it sped up for the positively charged CTAB reverse micelle. However, temperature-dependent measurements showed that the activation energy remained the same for all the cases. It has been concluded that a proton gradient exists inside the water-pool of the reverse micelle and it determines the buffer-like action of the water-pool that persists until about 2 N of HCl in AOT RM of w0 = 10.5. PMID:26854978

  14. Polymerization of o-Phenylenediamine Catalyzed by Hemeproteins Encapsulated in Reversed Micelle

    Institute of Scientific and Technical Information of China (English)

    YANG Yong; MAO Lu-yuan; LI Liu-zhu; LIU Xiao-guang; SHI Jun; CAO Shao-kui

    2004-01-01

    Hemeproteins encapsulated in reversed micelle formulated with di-2-ethylhexyl sulfosuccinate (AOT)was found to catalyze the polymerization of o-phenylenediamine (o-PDA) with hydrogen peroxide, whereas o-PDA catalyzed by hemeproteins dissolved in water could only form its trimers. As the nanostructural environment in reversed micelle acts as a certain orientation surrounding medium, it offers a strong electrostatic field that alters the reductive potential of Fe3+/Fe2+ (Em7) in the heme of hemeproteins and thus increases the catalytic activity of peroxidase accordingly. According to the results of UV-Vis, 1H NMR and FTIR, the polymer catalyzed by hemoglobin(Hb) in reversed micelle was presumed to be constructed of lines and trapeziforms alternatively.

  15. Vibrational dynamics of ice in reverse micelles.

    Science.gov (United States)

    Dokter, Adriaan M; Petersen, Christian; Woutersen, Sander; Bakker, Huib J

    2008-01-28

    The ultrafast vibrational dynamics of HDO:D(2)O ice at 180 K in anionic reverse micelles is studied by midinfrared femtosecond pump-probe spectroscopy. Solutions containing reverse micelles are cooled to low temperatures by a fast-freezing procedure. The heating dynamics of the micellar solutions is studied to characterize the micellar structure. Small reverse micelles with a water content up to approximately 150 water molecules contain an amorphous form of ice that shows remarkably different vibrational dynamics compared to bulk hexagonal ice. The micellar amorphous ice has a much longer vibrational lifetime than bulk hexagonal ice and micellar liquid water. The vibrational lifetime is observed to increase linearly from 0.7 to 4 ps with the resonance frequency ranging from 3100 to 3500 cm(-1). From the pump dependence of the vibrational relaxation the homogeneous linewidth of the amorphous ice is determined (55+/-5 cm(-1)). PMID:18247971

  16. Vibrational dynamics of ice in reverse micelles

    Science.gov (United States)

    Dokter, Adriaan M.; Petersen, Christian; Woutersen, Sander; Bakker, Huib J.

    2008-01-01

    The ultrafast vibrational dynamics of HDO :D2O ice at 180K in anionic reverse micelles is studied by midinfrared femtosecond pump-probe spectroscopy. Solutions containing reverse micelles are cooled to low temperatures by a fast-freezing procedure. The heating dynamics of the micellar solutions is studied to characterize the micellar structure. Small reverse micelles with a water content up to approximately 150 water molecules contain an amorphous form of ice that shows remarkably different vibrational dynamics compared to bulk hexagonal ice. The micellar amorphous ice has a much longer vibrational lifetime than bulk hexagonal ice and micellar liquid water. The vibrational lifetime is observed to increase linearly from 0.7to4ps with the resonance frequency ranging from 3100to3500cm-1. From the pump dependence of the vibrational relaxation the homogeneous linewidth of the amorphous ice is determined (55±5cm-1).

  17. Synthesis of nanocrystalline iron oxide by reverse micelle technique and its characterization

    International Nuclear Information System (INIS)

    Full text: Nanoparticles of Iron Oxide (Fe3O4) were synthesized in reverse micellar solutions. We used water-in-oil microemulsions consisting of water, twin tailed anionic bis (2-ethylhexyl) sodium sulfosuccinate (AOT) as a surfactant in isooctane (oil). Aqueous reactant FeSO4 and appropriate amount of Ammonium hydroxide were poured in the two microemulsions. All the steps of procedure carried out under the Argon atmosphere. The final precipitate was dried under vacuum condition. Reverse micelle route provides excellent control over particle size and particle shape. We studied the effect of Water/AOT ratio (w parameter) on controlling the particle size. The pure phase of magnetite (Fe3O4) was confirmed by X-Ray diffraction. The size of the prepared particles were determined by X-Ray and finally by SEM resulting in about 10 nm. Magnetic measurements carried out using VSM magnetometer. (authors)

  18. Extraction of monoclonal antibodies (IgG1) using anionic and anionic/nonionic reverse micelles.

    Science.gov (United States)

    George, Daliya A; Stuckey, David C

    2010-01-01

    Purification schemes for antibody production based on affinity chromatography are trying to keep pace with increases in cell culture expression levels and many current research initiatives are focused on finding alternatives to chromatography for the purification of Monoclonal antibodies (MAbs). In this article, we have investigated an alternative separation technique based on liquid-liquid extraction called the reverse micellar extraction. We extracted MAb (IgG1) using reverse micelles of an anionic surfactant, sodium bis 2-ethyl-hexyl sulfosuccinate (AOT) and a combination of anionic (AOT) and nonionic surfactants (Brij-30, Tween-85, Span-85) using isooctane as the solvent system. The extraction efficiency of IgG1 was studied by varying parameters, such as pH of the aqueous phase, cation concentration, and type and surfactant concentration. Using the AOT/Isooctane reverse micellar system, we could achieve good overall extraction of IgG1 (between 80 and 90%), but only 30% of the bioactivity of IgG1 could be recovered at the end of the extraction by using its binding to affinity chromatography columns as a surrogate measure of activity. As anionic surfactants were suspected as being one of the reasons for the reduced activity, we decided to combine a nonionic surfactant with an anionic surfactant and then study its effect on the extraction efficiency and bioactivity. The best results were obtained using an AOT/Brij-30/Isooctane reverse micellar system, which gave an overall extraction above 90 and 59% overall activity recovery. An AOT/Tween-85/Isooctane reverse micellar system gave an overall extraction of between 75 and 80% and overall activity recovery of around 40-45%. The results showed that the activity recovery of IgG1 can be significantly enhanced using different surfactant combination systems, and if the recovery of IgG1 can be further enhanced, the technique shows considerable promise for the downstream purification of MAbs. PMID:20665658

  19. Sizing of reverse micelles in microemulsions using NMR measurements of diffusion.

    Science.gov (United States)

    Law, Susan J; Britton, Melanie M

    2012-08-14

    This paper reports the size of reverse micelles (RMs) in AOT/octane/H(2)O and CTAB/hexanol/H(2)O microemulsions using magnetic resonance (MR) pulsed field gradient (PFG) measurements of diffusion. Diffusion data were measured using the pulsed gradient stimulated echo (PGSTE) experiment for surfactant molecules residing in the RM interface. Inverse Laplace transformation of these data generated diffusion coefficients for the RMs, which were converted into hydrodynamic radii using the Stokes-Einstein relation. This technique is complementary to those previously used to size RMs, such as dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS), but also offers several advantages, which are discussed. RM sizes, determined using the PGSTE method, in the AOT (sodium bis(2-ethylhexyl) sulfosuccinate) and CTAB (cetyltrimethylammonium bromide) microemulsions were compared with previous DLS and SAXS data, showing good agreement. Methods for determining number distributions from the PGSTE data, through the use of scaling factors, were investigated. PMID:22794150

  20. Synthesis and characterization of nanodispersed molecular aggregates of Prussian blue in aerosol OT reverse micelle.

    Science.gov (United States)

    Pramanik, Smritimoy; Das, Debasmita; Das, Kaushik; Bhattacharya, Subhash Ch

    2007-02-01

    Prussian Blue (PB) nanomolecular aggregates were prepared in a well-characterized, monodispersed biomimicking nanocavities formed by Aerosol OT (AOT) reverse micelle in H2O/AOT/heptane at different omega ([H2O]/[Surfactant]) employing coprecipitation technique. The formed nanomolecular aggregates of PB have been characterized by the UV-visible, Fourier Transformed Infrared (FTIR) spectroscopy as well as by Transmission Electron Microscopy (TEM) and Cyclic Voltammetric methods. Visible and FTIR spectroscopic measurements confirm the formation of PB nano aggregates. Experimental results reveal that the molar extinction coefficient of PB nanomolecular aggregates is different for two different regimes of omega of reverse micelles. TEM measurements show that the size of these reverse micellar entrapped nano aggregrates varied with hydration (omega). Studies on these nano sized particles indicate that Fe is present in a single mixed valence state along the Fe-C-N-Fe skeleton in PB and the half wave potential (E1/2) becomes more positive with increase in the size of the nano aggregates. PMID:17450811

  1. Ultrafast dynamics of water in cationic micelles.

    Science.gov (United States)

    Dokter, Adriaan M; Woutersen, Sander; Bakker, Huib J

    2007-03-28

    The effect of confinement on the dynamical properties of liquid water is investigated for water enclosed in cationic reverse micelles. The authors performed mid-infrared ultrafast pump-probe spectroscopy on the OH-stretch vibration of isotopically diluted HDO in D(2)O in cetyltrimethylammonium bromide (CTAB) reverse micelles of various sizes. The authors observe that the surfactant counterions are inhomogeneously distributed throughout the reverse micelle, and that regions of extreme salinity occur near the interfacial Stern layer. The authors find that the water molecules in the core of the micelles show similar orientational dynamics as bulk water, and that water molecules in the counterion-rich interfacial region are much less mobile. An explicit comparison is made with the dynamics of water confined in anionic sodium bis(2-ethythexyl) sulfosuccinate (AOT) reverse micelles. The authors find that interfacial water in cationic CTAB reverse micelles has a higher orientational mobility than water in anionic AOT reverse micelles. PMID:17411144

  2. Ultrafast dynamics of water in cationic micelles

    Science.gov (United States)

    Dokter, Adriaan M.; Woutersen, Sander; Bakker, Huib J.

    2007-03-01

    The effect of confinement on the dynamical properties of liquid water is investigated for water enclosed in cationic reverse micelles. The authors performed mid-infrared ultrafast pump-probe spectroscopy on the OH-stretch vibration of isotopically diluted HDO in D2O in cetyltrimethylammonium bromide (CTAB) reverse micelles of various sizes. The authors observe that the surfactant counterions are inhomogeneously distributed throughout the reverse micelle, and that regions of extreme salinity occur near the interfacial Stern layer. The authors find that the water molecules in the core of the micelles show similar orientational dynamics as bulk water, and that water molecules in the counterion-rich interfacial region are much less mobile. An explicit comparison is made with the dynamics of water confined in anionic sodium bis(2-ethythexyl) sulfosuccinate (AOT) reverse micelles. The authors find that interfacial water in cationic CTAB reverse micelles has a higher orientational mobility than water in anionic AOT reverse micelles.

  3. Validation and divergence of the activation energy barrier crossing transition at the AOT/lecithin reverse micellar interface.

    Science.gov (United States)

    Narayanan, S Shankara; Sinha, Sudarson Sekhar; Sarkar, Rupa; Pal, Samir Kumar

    2008-03-13

    In this report, the validity and divergence of the activation energy barrier crossing model for the bound to free type water transition at the interface of the AOT/lecithin mixed reverse micelle (RM) has been investigated for the first time in a wide range of temperatures by time-resolved solvation of fluorophores. Here, picosecond-resolved solvation dynamics of two fluorescent probes, ANS (1-anilino-8-naphthalenesulfonic acid, ammonium salt) and Coumarin 500 (C-500), in the mixed RM have been carefully examined at 293, 313, 328, and 343 K. Using the dynamic light scattering (DLS) technique, the size of the mixed RMs at different temperatures was found to have an insignificant change. The solvation process at the reverse micellar interface has been found to be the activation energy barrier crossing type, in which interface-bound type water molecules get converted into free type water molecules. The activation energies, Ea, calculated for ANS and C-500 are 7.4 and 3.9 kcal mol(-1), respectively, which are in good agreement with that obtained by molecular dynamics simulation studies. However, deviation from the regular Arrhenius type behavior was observed for ANS around 343 K, which has been attributed to the spatial heterogeneity of the probe environments. Time-resolved fluorescence anisotropy decay of the probes has indicated the existence of the dyes in a range of locations in RM. With the increase in temperature, the overall anisotropy decay becomes faster revealing the lability of the microenvironment at elevated temperatures. PMID:18281975

  4. Startling temperature effect on proteins when confined: single molecular level behaviour of human serum albumin in a reverse micelle.

    Science.gov (United States)

    Sengupta, Bhaswati; Yadav, Rajeev; Sen, Pratik

    2016-06-01

    The present work reports the effect of confinement, and temperature therein, on the conformational fluctuation dynamics of domain-I of human serum albumin (HSA) by fluorescence correlation spectroscopy (FCS). The water-pool of a sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelle has been used as the confined environment. It was observed that the conformational fluctuation time is about 6 times smaller compared to bulk medium when confined in a water-pool of 3.5 nm radius. On increasing the size of the water-pool the conformational fluctuation time was found to increase monotonically and approaches the bulk value. The effect of confinement is on par with the general belief about the restricted motion of a macromolecule upon confinement. However, the effect of temperature was found to be surprising. An increase in the temperature from 298 K to 313 K induces a larger change in the conformational fluctuation time in HSA, when confined. In the bulk medium, apparently there is no change in the conformational fluctuation time in the aforementioned temperature range, whereas, when HSA is present in an AOT water-pool of radius 3.5 nm, about an 88% increase in the fluctuation time was observed. The observed prominent thermal effect on the conformational dynamics of domain-I of HSA in the water-pool of an AOT reverse micelle as compared to in the bulk medium was concluded to arise from the confined solvent effect. PMID:27166785

  5. Mechanisms of Cytochrome C Extraction by Reverse Micelles

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The extraction of cytochrome C was carried out by means of phase transfer technique with three different reverse micellar systems, i.e., a CTAB micellar solution in n-butyl alcohol-chloroform(volume ratio 4∶1), an AOT micellar solution in isooctane and a SDSS-D2EHPA micellar solution in isooctane. The extraction mechanisms were studied. The results show that the extraction mechanisms for the same proteins with different types of reverse micellar systems can be distinct. The extraction of cytochrome C with CTAB and SDSS-D2EHPA reverse micellar systems are carried out according to the mechanism of electrostatic interaction. However, in the extraction of cytochrome C with the AOT reverse micellar system, the electrostatic interaction between the protein and the surfactant is not important.

  6. Process of forming compounds using reverse micelle or reverse microemulsion systems

    Science.gov (United States)

    Linehan, John C.; Fulton, John L.; Bean, Roger M.

    1998-01-01

    The present invention is directed to a process for producing a nanometer-sized metal compound. The process comprises forming a reverse micelle or reverse microemulsion system comprising a polar fluid in a non-polar or low-polarity fluid. A first reactant comprising a multi-component, water-soluble metal compound is introduced into the polar fluid in a non-polar or low-polarity fluid. This first reactant can be introduced into the reverse micelle or reverse microemulsion system during formation thereof or subsequent to the formation of the reverse micelle or microemulsion system. The water-soluble metal compound is then reacted in the reverse micelle or reverse microemulsion system to form the nanometer-sized metal compound. The nanometer-sized metal compound is then precipitated from the reverse micelle or reverse microemulsion system.

  7. Preparation of ZrO2 nano-particles by the hydrolysis of ZrOCl2 solution in the reverse micelles

    Institute of Scientific and Technical Information of China (English)

    Chensha Li; Tongxiang Liang; Tianyong Luo

    2006-01-01

    Zirconia nano-particles have been produced by the hydrolysis of ZrOGl2 solution in the reverse micelles of a liquid-liquid two-phase system, in which sodium bis(2-ethylhexyl) sulfosuccinite (AOT) and toluene were chosen as the surfactant and organic phase, respectively. The reverse micelles prevented the aggregation of primary particles and reduced the diameters of zirconia nanoparticles. Superfine zirconia powders soft-aggregated by the zirconia nano-particles were obtained. The diameters of zirconia nanoparticles were influenced by the quantity of the surfactant.

  8. Size-controlled synthesis of ZrO2-TiO2 nanoparticles prepared via reverse micelle method

    International Nuclear Information System (INIS)

    Zirconium-titanium mixed oxide nanoparticles have been synthesized using microreactors made of bis-(2-ethylhexyl) sulfosuccinate (AOT)/water/n-hexane microemulsions. The control of particle size was achieved by varying the process variables, such as water-to-surfactant molar ratio and reagent concentration. Their sizes, appearances, crystal structures, pore diameter and surface area were characterized by TEM, XRD, N2 adsorption/desorption methods. The results revealed that samples prepared in reverse micelles had no crystalline phase. The Beckmann rearrangement of cyclohexanone oxime on ZrO2-TiO2 nanoparticles was carried out in a fixed-bed down flow reactor to investigate the effect of particle size on catalytic activity and selectivity. Samples synthesized in reverse micelles had better reaction performance than samples prepared via sol-gel method. A parallel relationship could be drawn between the catalytic activity and the particle size as well as the selectivity of the catalyst

  9. Electron solvation in aqueous reverse micelles: Equilibrium properties

    Science.gov (United States)

    Laria, Daniel; Kapral, Raymond

    2002-10-01

    Microscopic aspects of electron solvation in aqueous reverse micelles are investigated using molecular dynamics simulation techniques. Two micelle sizes, with water/surfactant ratios of 3 and 7.5, are examined. The electron is treated quantum mechanically using Feynman path integral methods while the water, surfactant head groups, and counter ions are treated classically. Through computations of the free energy as a function of the radial distance, the electron is found to be preferentially solvated in the interior of the micelle in the "bulk" water pool. For small micelles, the presence of the electron leads to a depletion of water in the central region of the micelle and thus strongly disrupts the water equilibrium structure. Contact and solvent-separated ion pairs between the electron and Na+ counter ions are found to play an important role in the equilibrium structure. For the two micelle sizes investigated, the most stable solvation structures correspond to contact ion pairs. The localization of the electronic charge distribution is found to increase with micelle size, signaling more efficient solvation in larger micelles.

  10. Acid Hydrolysis of Bromazepam Catalyzed by Micelles, Reverse Micelles, and Microemulsions

    Directory of Open Access Journals (Sweden)

    Ferdousi Begum

    2015-01-01

    Full Text Available Kinetics of the acid hydrolysis of bromazepam (Bz has been investigated in micelles, reverse micelles, and microemulcions of cetyltrimethylammonium bromide (CTAB by spectrophotometric method. The rate of the acid hydrolysis of Bz was found to be enhanced both below and above the critical micelle concentration (CMC of CTAB in aqueous solution. The pseudo-first-order rate constant (k′ shows an initial decrease for both low and high H+ concentrations. With further increase in [CTAB], at low [H+], the k′ attains an almost constant value, while, at high [H+], the k′ passes through a maximum and then decreases. The kinetic data for catalysis by micelles of CTAB was interpreted with the pseudophase ion exchange (PIE model. In CTAB/cyclohexane/1-butanol/water microemulsions, as the water to surfactant ratio (wo increases, the physicochemical properties and droplet sizes of microemulsions significantly change and distinct changes in reaction environment can be marked. The rate of the hydrolysis reaction exhibits excellent correlation with the physicochemical properties and droplet sizes of the microemulsions and reverse micelles of CTAB. At [H+] = 0.001 M, in reverse micelles and microemulsions of CTAB, the k′ of the acid hydrolysis of Bz decreases sharply followed by a slight increase with increasing wo.

  11. Liquid-liquid extraction by reversed micelles in biotechnological processes

    Directory of Open Access Journals (Sweden)

    Kilikian B. V.

    2000-01-01

    Full Text Available In biotechnology there is a need for new purification and concentration processes for biologically active compounds such as proteins, enzymes, nucleic acids, or cells that combine a high selectivity and biocompatibility with an easy scale-up. A liquid-liquid extraction with a reversed micellar phase might serve these purposes owing to its capacity to solubilize specific biomolecules from dilute aqueous solutions such as fermentation and cell culture media. Reversed micelles are aggregates of surfactant molecules containing an inner core of water molecules, dispersed in a continuous organic solvent medium. These reversed micelles are capable of selectively solubilizing polar compounds in an apolar solvent. This review gives an overview of liquid-liquid extraction by reversed micelles for a better understanding of this process.

  12. Synthesis of nanosilver particles by reverse micelle method and study of their bactericidal properties

    Energy Technology Data Exchange (ETDEWEB)

    Tran Thi Ngoc Dung; Ngo Quoc Buu; Dang Viet Quang; Le Anh Bang; Nguyen Hoai Chau; Nguyen Thi Ly [Institute of Environmental Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay Distr., Hanoi (Viet Nam); Huynh Thi Ha [Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay Distr., Hanoi (Viet Nam); Nguyen Vu Trung [National Institute for Infectious and Tropical Diseases, 1 Ton That Tung, Dong Da Distr., Hanoi (Viet Nam)], E-mail: ttndzung@yahoo.com, E-mail: buu_nq@yahoo.com

    2009-09-01

    Nanosilver particles have been synthesized by the reverse micelle method, where AgNO{sub 3} was used as a silver ions source, NaBH{sub 4} and quercetin - as reducing agents, CTAB, SDOSS and AOT- as surfactants, while the stabilizer was Vietnamese chitosan. Studying the factors influencing the process of nanosilver particle formation, it was shown that the particle size of the nanosilver products depends on the concentration of the reaction components and their stoichiometric ratio. It was also shown that the reaction system using AOT surfactant is capable of producing nanosilver particles with smallest nanoparticles ({phi}{sub av} {approx} 5 nm) and good particle-size distribution. The study on bactericidal activity of the nanosilver products indicated that the disinfecting solution with a nanosilver concentration of 3 ppm was able to inhibit all E.coli and Coliforms, TPC and fungi at 15 ppm, while Vibrio cholerae cells were inactivated completely with 0.5 ppm of nanosilver after 30 minutes exposition.

  13. Artificial Self-Sufficient P450 in Reversed Micelles

    Directory of Open Access Journals (Sweden)

    Teruyuki Nagamune

    2010-04-01

    Full Text Available Cytochrome P450s are heme-containing monooxygenases that require electron transfer proteins for their catalytic activities. They prefer hydrophobic compounds as substrates and it is, therefore, desirable to perform their reactions in non-aqueous media. Reversed micelles can stably encapsulate proteins in nano-scaled water pools in organic solvents. However, in the reversed micellar system, when multiple proteins are involved in a reaction they can be separated into different micelles and it is then difficult to transfer electrons between proteins. We show here that an artificial self-sufficient cytochrome P450, which is an enzymatically crosslinked fusion protein composed of P450 and electron transfer proteins, showed micelle-size dependent catalytic activity in a reversed micellar system. Furthermore, the presence of thermostable alcohol dehydrogenase promoted the P450-catalyzed reaction due to cofactor regeneration.

  14. TR-ESR Investigation on Reaction of Vitamin C with Excited Triplet of 9,10-phenanthrenequinone in Reversed Micelle Solutions

    Science.gov (United States)

    Xu, Xin-sheng; Shi, Lei; Liu, Yi; Ji, Xue-han; Cui, Zhi-feng

    2011-04-01

    Time-resolved electron spin resonance has been used to study quenching reactions between the antioxidant Vitamin C (VC) and the triplet excited states of 9,10-phenanthrenequinone (PAQ) in ethylene glycol-water (EG-H2O) homogeneous and inhomogeneous reversed micelle solutions. Reversed micelle solutions were used to be the models of physiological environment of biological cell and tissue. In PAQ/EG-H2O homogeneous solution, the excited triplet of PAQ (3PAQ*) abstracts hydrogen atom from solvent EG. In PAQ/VC/EG-H2O solution, 3PAQ* abstracts hydrogen atom not only from solvent EG but also from VC. The quenching rate constant of 3PAQ* by VC is close to the diffusion-controlled value of 1.41 × 108 L/(mol ·s). In hexadecyltrimethylammonium bromide (CTAB)/EG-H2O and aerosol OT (AOT)/EG-H2O reversed micelle solutions, 3PAQ* and VC react around the water-oil interface of the reversed micelle. Exit of 3PAQ* from the lipid phase slows down the quenching reaction. For Triton X-100 (TX-100)/EG-H2O reversed micelle solution, PAQ and VC coexist inside the hydrophilic polyethylene glycol core, and the quenching rate constant of 3PAQ* by VC is larger than those in AOT/EG-H2O and CTAB/EG-H2O reversed micelle solutions, even a little larger than that in EG-H2O homogeneous solution. The strong emissive chemically induced dynamic electron polarization of As.- resulted from the effective TM spin polarization transfer in hydrogen abstraction of 3PAQ* from VC.

  15. Structural investigation of diglycerol polyisostearate reverse micelles in organic solvents.

    Science.gov (United States)

    Shrestha, Lok Kumar; Shrestha, Rekha Goswami; Oyama, Keiichi; Matsuzawa, Makoto; Aramaki, Kenji

    2009-09-24

    The structure of glycerol-based reverse micelles in the surfactant/oil binary system without external water addition has been investigated using a small-angle X-ray scattering technique, and different tunable parameters for the structure control of reverse micelles are determined. The scattering data were evaluated by the generalized indirect Fourier transformation (GIFT) method and complemented by model fitting. It was found that diglycerol polyisostearates (abbreviated as (iso-C18)nG2, n=2-4, where n represents the number of isosterate chains per surfactant molecule) form reverse micelles in a variety of organic solvents such as cyclohexane, n-decane, and n-hexadecane without the addition of water from outside, and their structure (shape and size) depends on solvent properties (alkyl chain length), tail architecture of the surfactant, temperature, and added water. Small globular types of micelles were observed in the (iso-C18)2G2/cyclohexane system at 25 degrees C. The micellar size and the aggregation number were increased with increasing the alkyl chain length of the oils resulting in elongated ellipsoidal prolate or rodlike type micelles in the (iso-C18)2G2/hexadecane system. This structural evolution is caused by the different penetration tendency depending on the chain length of oils to the lipophilic chain of the surfactant. At fixed oil, composition, and temperature, the tail architecture of the surfactant played a crucial role in the micellar structure. The micellar size and, hence, the aggregation number decreased monotonically with increasing number of isostearate chain per surfactant molecule due to the voluminous lipophilic part of the surfactant. Composition could not modulate the structure of micelles but led to strong repulsive interactions among the micelles due to reduced osmotic compressibility of the system at higher concentrations. Increasing temperature decreased the micellar size, while the cross-section structure remains essentially the

  16. Vibrational energy relaxation of water in Aerosol OT reverse micelle

    Science.gov (United States)

    Pang, Yoonsoo; Deak, John; Dlott, Dana

    2005-03-01

    An IR-Raman technique with mid-IR pump and anti-Stokes Raman probe is used to investigate reverse micelle mixture of Aerosol OT, water, and carbon tetrachloride, where polar water phase and nonpolar oil phase is separated by a monolayer of surfactant molecules. Anti-Stokes Raman scattering is only dependent on the population of vibrationally excited states, thus time-dependent population changes of parent/daughter vibrations can be monitored with this technique. Vibrational energy from nanodroplet of water is transferred to the surfactant head group in 1.8 ps and then out to solvent in 10 ps. Vibrational energy directly pumped into the surfactant tail group results in a slower 20-40 ps energy transfer to solvent. This energy transfer cannot be explained by ordinary heat transfer, but the specific vibrational energy relaxation pathway such as sulfonate stretch of surfactant molecules should be used. We can change the water-to-solvent energy transfer rate by adopting different size of reverse micelles or changing pump frequency over the broad OH stretch mode of water due to hydrogen bond network. Water molecules confined in nanometer scale reverse micelles have very different properties from bulk water and we have found many differences between the vibrational dynamics of water in these reverse micelles and those of bulk water.

  17. What can be expected from NMR in reversed micelles?

    International Nuclear Information System (INIS)

    A review is given of NMR studies on reversed micellar systems since 1970. General principles are emphasized through examples which have led to relevant physico-chemical results in the area. NMR techniques or theories are not detailed in order to focus primarily on the information obtained on the micelles. (author). 50 refs.; 9 figs

  18. Neural modeling of bromelain extraction by reversed micelles

    OpenAIRE

    Ana Maria Frattini Fileti; Gilvan Anderson Fischer; Elias Basile Tambourgi

    2010-01-01

    A pulsed-cap microcolumn was used for bromelain extraction from pineapple juice by reversed micelles. The cationic micellar solution used BDBAC as the surfactant, isooctane as the solvent and hexanol as the co-solvent. In order to capture the dynamic behavior and the nonlinearities of the column, the operating conditions were modified in accordance with the central composite design for the experiment, using the ratio between the light phase flow rate and the total flow rate, and the time inte...

  19. Ultrafast vibrational dynamics of water confined in phospholipid reverse micelles

    Directory of Open Access Journals (Sweden)

    Elsaesser T.

    2013-03-01

    Full Text Available We study the ultrafast dynamics of OH stretching and bending vibrations of water inside dioleoylphosphatidylcholine (DOPC reverse micelles in a wide range of hydration. A strong hydration level dependence for the spectral diffusion rates is found and explained by the distinctly different environment for single water molecules bound to the anionic phosphate group. We show that the energy relaxation pathway of the OH stretching vibration at low hydration level involves the OH bending.

  20. SANS from reverse micelles in various oil phases

    International Nuclear Information System (INIS)

    Full text: Small angle neutron scattering (SANS) has been used to investigate the effect of solvency on the structure of water-in-oil microemulsions at 25 deg C and 55 deg C. The microemulsions contain reverse micelles which are composed of a non-ionic surfactant with a polyisobutylene oligomer tail and acid-amide headgroup, and an aqueous solution of an electrolyte as the core. The composition of the continuous phase is varied systematically from neat hexadecane, toluene and cyclohexane to a 1:1 combination by volume of each type of oil. The micellar radius, R, and volume fraction of the micelles in the oil phase are found to vary as a function of temperature and the composition of the continuous phase. For a one component oil phase, the size of the micelles changes according to the polarity of the phase viz. R{toluene > cyclohexane > hexadecane}. For the two component continuous phase, the size of the micelles is greatest for the most polar toluene/cyclohexane mixture, whilst for the other combinations it follows the order hexadecane/cyclohexane > hexadecane/toluene. The volume fraction yields the trend hexadecane .cyclohexane >> toluene for the one component oil phase and hexadecane/cyclohexane > hexadecane/toluene > cyclohexane/toluene for the mixed oil system, indicating the greater solubility of the surfactant in toluene. The radius and volume fraction decrease with temperature

  1. Complex permittivity of FeCl3/AOT/CCl4 microemulsions probed by AC impedance spectroscopy.

    Science.gov (United States)

    Calandra, Pietro; Ruggirello, Angela; Turco Liveri, Vincenzo

    2009-09-01

    The complex permittivity of FeCl(3)/AOT/CCl(4) microemulsions in the 1-10(5) Hz frequency range has been measured by the conventional AC complex impedance technique. Measurements as a function of the volume fraction of the dispersed phase (FeCl(3)+AOT) and temperature at fixed salt-to-AOT molar ratio (R, R = 0.5) show that the entrapment of FeCl(3) clusters significantly enhances the local permittivity of the AOT reverse micelles and the number density of charge carriers resulting from the peculiar state of the confined inorganic salt. An estimate of the apparent static permittivity of the FeCl(3) ionic clusters entrapped in the core of AOT reverse micelles gives the very high and quite surprisingly value of about 237. Moreover, a thorough analysis of conductivity data and of their temperature dependence strongly supports the hypothesis that the charge transport in these systems is mainly sustained by a mechanism of hopping consisting in the continuous jumping of charged species within supra-micellar aggregates of AOT reverse micelles whose aggregation is driven by fluctuating opposite charges on contacting micelles. PMID:19481764

  2. Controlled Synthesis of Nanomaterials using Reverse Micelles

    Directory of Open Access Journals (Sweden)

    Sonalika Vaidya

    2008-07-01

    Full Text Available Monophasic nanosized oxides were synthesised mainly from metal oxalate nanorods obtainedusing the reverse micellar method. This paper focuses on the methodology to obtain importantmetal oxides like tin dioxide, cerium oxide (CeO2 , zirconia, and zinc oxide. The effect of oxidationstate of the metal ion on the morphology of the oxalates was studied. Nanorods of zinc (IIoxalate (120 nm in dia and 600 nm in length were obtained while spherical particles of size 4Œ6 nm were obtained for cerium (III oxalate. The decomposition of these precursors at highertemperature led to the formation of their respective oxides. Mixture of nanorods and nanoparticles of CeO2 was obtained while 3Œ4 nm sized ZrO2 nanoparticles were obtained by thermaldecomposition of zirconium oxalate precursor. The dielectric constant and loss were highly stablewith frequency (at room temperature for both ceria and zirconia nanoparticles.  ZnO nanoparticles(55 nm sized were obtained by the decomposition of zinc oxalate nanorods. Three peaks corresponding to free excitonic emission, free-to-bound, and donor-acceptor transitions were observed in the photolumine scence studies at 20 K for ZnO nanoparticles.Defence Science Journal, 2008, 58(4, pp.531-544, DOI:http://dx.doi.org/10.14429/dsj.58.1674

  3. The influence of charge on the structure and dynamics of water encapsulated in reverse micelles.

    Science.gov (United States)

    Patra, Animesh; Luong, Trung Quan; Mitra, Rajib Kumar; Havenith, Martina

    2014-07-01

    Hydrogen-bonded structure and relaxation dynamics of water entrapped inside reverse micelles (RMs) composed of surfactants with different charged head groups: sodium bis(2-ethylhexyl) sulfosuccinate (AOT) (anionic), didodecyldimethylammonium bromide (DDAB) (cationic) and Igepal CO-520 (Igepal) (nonionic) in cyclohexane (Cy) have been studied as a function of hydration (defined by ). Sub-diffusive slow (sub-ns) relaxation dynamics of water has been measured by the time resolved fluorescence spectroscopy (TRFS) technique using two fluorophores, namely 8-anilino-1-naphthalenesulfonic acid (ANS) and coumarin-343 (C-343). The hydrogen bonded connectivity network of water confined in these RMs has been investigated by monitoring the hydrogen bond stretching and libration bands of water using far-infrared FTIR spectroscopy. In addition, the ultrafast collective relaxation dynamics of water inside these RMs has been determined by dielectric relaxation in the THz region (0.2-2.0 THz) using THz time domain spectroscopy (THz-TDS). While TRFS measurements establish the retardation of water dynamics for all the RM systems, FTIR and THz-TDS measurements provide with signature of charge specificity. PMID:24848870

  4. Excited state intramolecular charge transfer reaction in non-aqueous reverse micelles: Effects of solvent confinement and electrolyte concentration

    Indian Academy of Sciences (India)

    Tuhin Pradhan; Harun Al Rasid Gazi; Biswajit Guchhait; Ranjit Biswas

    2012-03-01

    Steady state and time resolved fluorescence emission spectroscopy have been employed to investigate the effects of solvent confinement and electrolyte concentration on excited state intramolecular charge transfer (ICT) reaction in 4-(1-pyrrolidinyl) benzonitrile (P5C), 4-(1-piperidinyl) benzonitrile (P6C), and 4-(1-morpholenyl) benzonitrile (M6C) in AOT/n-heptane/acetonitrile and AOT/n-heptane/methanol reverse micelles. Dramatic confinement effects have been revealed via a huge reduction (factor ranging between 100 and 20) over bulk values of both equilibrium and reaction rate constants. A strong dependence on the size of the confinement () of these quantities has also been observed. dependent average static dielectric constant, viscosity and solvation time-scale have been determined. Estimated dielectric constants for confined methanol and acetonitrile show a decrease from the respective bulk values by a factor of 3-5 and viscosities increased by a factor of 2 at the highest considered. Addition of electrolyte at = 5 for acetonitrile is found to produce a linear increase of confined solvent viscosity but leads to a non-monotonic electrolyte concentration dependence of average solvation time. Reaction rate constant is found to decrease linearly with electrolyte concentration for P5C and P6C but non-monotonically for M6C, the highest decrease for all the molecules being ∼ 20% over the value in the absence of added electrolyte in the solvent pool. The observed huge reduction in reaction rate constant is attributed to the effects of decreased solution polarity, enhanced viscosity and slowed-down solvent reorganization of the solvent under confinement in these non-aqueous reverse micelles.

  5. Study on technologies of forward extraction of protein from tomato by reverse micelles%反胶束溶液萃取番茄凝集素的前萃工艺探讨

    Institute of Scientific and Technical Information of China (English)

    朱澄云; 王岩; 赵琨; 韩国华; 徐璐; 黄小丽

    2011-01-01

    Objective To explore the possibility of extraction of tomato lectin by aerosol OT (AOT)isooctane reverse micelles system. Methods The effects of pH, AOT concentration, KC1 concentration on the forward extraction rate were investigated and analyzed. Results At the condition of KC1 concentration 50 mmol·L-1 ,AOT concentration 110 mmol·L-1 and pH 9.0 ,the forward protein extraction rate achieved 46. 51%. Conclusions It is possible to extract tomato lectin using reversed micelles of AOT-isooctane.%目的 探讨用丁二酸二异辛酯磺酸钠(aerosl OT,AOT)-异辛烷反胶束体系萃取番茄凝集素的可能性.方法 考察并分析了反胶束溶液萃取番茄凝集素时的几种因素如pH值、表面活性剂AOT的浓度、KC1的浓度等对蛋白前萃率的影响.结果 在KC1浓度为50 mmol·L-1、AOT浓度为110 mmol·L-1及pH值9.0条件下前萃取率为46.51%.结论 以AOT-异辛烷反胶束溶液萃取番茄凝集素是可行的.

  6. Graphite-teflon composite bienzyme electrodes for the determination of cholesterol in reversed micelles. Application to food samples.

    Science.gov (United States)

    Peña, N; Ruiz, G; Reviejo, A J; Pingarrón, J M

    2001-03-15

    A bienzyme amperometric composite biosensor for the determination of free and total cholesterol in food samples is reported. Cholesterol oxidase and horseradish peroxidase, together with potassium ferrocyanide as a mediator, are incorporated into a graphite-70% Teflon matrix. The compatibility of this biosensor design with predominantly nonaqueous media allows the use of reversed micelles as working medium. The reversed micelles are formed with ethyl acetate as continuous phase (in which cholesterol is soluble), a 4% final concentration of 0.05 mol L(-1) phosphate buffer solution, pH 7.4, as dispersed phase, and 0.1 mol L(-1) AOT as emulsifying agent. Studies on the repeatability of the amperometric response obtained at +0.10 V, with and without regeneration of the electrode surface by polishing, on the useful lifetime of one single biosensor and on the reproducibility in the fabrication of different pellets illustrate the robustness of the biosensor design. Determination of free and total cholesterol in food samples such as butter, lard, and egg yoke was carried out, and the obtained results were advantageously compared with those provided by using a commercial Boehringer test kit. PMID:11305650

  7. DNA polymerase beta reveals enhanced activity and processivity in reverse micelles.

    Science.gov (United States)

    Anarbaev, Rashid O; Rogozina, Anastasia L; Lavrik, Olga I

    2009-04-01

    Water is essential for the stability and functions of proteins and DNA. Reverse micelles are simple model systems where the structure and dynamics of water are controlled. We have estimated the size of complex reverse micelles by light scattering technique and examined the local microenvironment using fluorescein as molecular probe. The micelle size and water polarity inside reverse micelles depend on water volume fraction. We have investigated the different hydration and confinement effects on activity, processivity, and stability of mammalian DNA polymerase beta in reverse micelles. The enzyme displays high processivity on primed single-stranded M13mp19 DNA with maximal activity at 10% of water content. The processivity and activity of DNA polymerase strongly depend on the protein concentration. The enzyme reveals also the enhanced stability in the presence of template-primer and at high protein concentration. The data provide direct evidence for strong influence of microenvironment on DNA polymerase activity. PMID:19138815

  8. pH-responsive release of proteins from biocompatible and biodegradable reverse polymer micelles.

    Science.gov (United States)

    Koyamatsu, Yuichi; Hirano, Taisuke; Kakizawa, Yoshinori; Okano, Fumiyoshi; Takarada, Tohru; Maeda, Mizuo

    2014-01-10

    A reverse polymer micelle with a diameter of 100nm was prepared for a protein carrier releasing payloads in a pH-dependent manner. The reverse polymer micelle was made from an amphiphilic diblock copolymer of biodegradable poly(d,l-lactic-co-glycolic acid) (PLGA) and biocompatible poly(ethylene glycol) (PEG). PLGA having a terminal carboxyl group was additionally embedded in the micelle's PLGA layer via hydrophobic interaction. The micelles encapsulating bovine serum albumin and streptavidin released the proteins under neutral and basic conditions, whereas the proteins remained in the interior at acidic pH. Using erythropoietin as a protein drug, it was also exemplified that the released protein retained its cell proliferation activity even after rigorous formulation processes, including water-in-oil emulsion. The present reverse polymer micelle could potentially find application as an oral protein drug delivery carrier. PMID:24200745

  9. Characterization of Cetyltrimethylammonium Bromide/Hexanol Reverse Micelles by Experimentally Benchmarked Molecular Dynamics Simulations.

    Science.gov (United States)

    Fuglestad, Brian; Gupta, Kushol; Wand, A Joshua; Sharp, Kim A

    2016-02-23

    Encapsulation of small molecules, proteins, and other macromolecules within the protective water core of reverse micelles is emerging as a powerful strategy for a variety of applications. The cationic surfactant cetyltrimethylammonium bromide (CTAB) in combination with hexanol as a cosurfactant is particularly useful in the context of solution NMR spectroscopy of encapsulated proteins. Small-angle X-ray and neutron scattering is employed to investigate the internal structure of the CTAB/hexanol reverse micelle particle under conditions appropriate for high-resolution NMR spectroscopy. The scattering profiles are used to benchmark extensive molecular dynamics simulations of this reverse micelle system and indicate that the parameters used in these simulations recapitulate experimental results. Scattering profiles and simulations indicate formation of homogeneous solutions of small approximately spherical reverse micelle particles at a water loading of 20 composed of ∼150 CTAB and 240 hexanol molecules. The 3000 waters comprising the reverse micelle core show a gradient of translational diffusion that reaches that of bulk water at the center. Rotational diffusion is slowed relative to bulk throughout the water core, with the greatest slowing near the CTAB headgroups. The 5 Å thick interfacial region of the micelle consists of overlapping layers of Br(-) enriched water, CTAB headgroups, and hexanol hydroxyl groups, containing about one-third of the total water. This study employs well-parametrized MD simulations, X-ray and neutron scattering, and electrostatic theory to illuminate fundamental properties of CTAB/hexanol reverse micelle size, shape, partitioning, and water behavior. PMID:26840651

  10. Environmental applications of lanthanide counterions bound to reverse micelles

    International Nuclear Information System (INIS)

    The lanthanide surfactants of the formula [Ln(EHS)3] [where EHS - bis(2-ethylhexyl) sulfosuccinate and Ln = Tb(III)or Eu(III)] have been synthesized from aerosol OT, and used to detect select organic analytes. This technique is based on the ability of the lanthanide ions to transform the energy absorbed by the organic compounds into a visible lanthanide ion emission via intermolecular energy transfer. When dissolved in an organic solvent, the surfactants form reverse micelles which provide molecular organization of the donor and acceptor species to come into close contact for energy transfer. An enhancement of the sensitized luminescence of the lanthanide counterions have been demonstrated in the presence of many organic analytes. The results show that a significant enhancement can be achieved by using an organic analyte containing a polar substituent. The observed efficient sensitization of the lanthanide ions is used for the determination of select organic analytes. Many of the organic analytes used are potential pollutants and carcinogens. Therefore, this procedure is more likely to provide a detection scheme to selectively analyze water for environmentally important pollutants such as polychlorobiphenyls. 1H NMR spectroscopy has been used to establish the interaction between the organic analyte donor and lanthanide ion acceptor and then examine the relative locations of various photosensitive species present in the reverse micellar solution. This information was derived from changes in the chemical shift and resolution of both the analyte and the surfactant protons upon solubilization of the donor in the micellar solution. These data are used to estimate the average distance between the donor and the acceptor in this analytical scheme. The ability and the effectiveness of these surfactants to act as NME shift reagents is discussed

  11. Possible role of laccase from Fusarium incarnatum UC-14 in bioremediation of Bisphenol A using reverse micelles system.

    Science.gov (United States)

    Chhaya, Urvish; Gupte, Akshaya

    2013-06-15

    Bisphenol A [2,2 bis (4 hydroxyphenyl) propane] is widely used in the variety of industrial and residential applications such as the synthesis of polymers including polycarbonates, epoxy resins, phenol resins, polyesters and polyacrylates. BPA has been recognized as an Endocrine Disrupting Chemicals (EDC), thus it is necessary to assess its biodegradability or fate in the natural environment. In general, environmental pollutant such as BPA does not dissolve in aqueous media, owing to their high hydrophobicity, and hence non-aqueous catalysis can be employed to enhance biodegradability of phenolic environmental pollutant. Purified laccase hosted in reverse micelles using ternary system of isooctane: AOT [Bis (2-ethylhexyl) sulphosuccinate sodium salt)]:water having hydration ratio (Wo) of 30 with protein concentration of 43.5 μg/ml was found to eliminate 91.43% of 200 ppm of Bisphenol A at 50 °C, pH-6.0 when incubated with laccase/Reverse Micelles system for 75 min. GC-MS analysis of isooctane soluble fractions detected the presence of 4,4'-(2 hydroxy propane 1,2 diyl) diphenol, bis (4-hydroxylphenyl) butenal and 2-(1-(4-hydroxyphenyl) vinyl) pent-2-enal indicated degradation of BPA by two oxidation steps and one ring opening step (C-C bond cleavage). Laccase/RM system exhibited several advantages for the oxidative degradation of hydrophobic phenols mainly because of the solubility of either enzyme or substrate was improved in organic media and the stable activity of laccase in organic media was achieved. PMID:23611799

  12. Glyco-Nanoparticles Made from Self-Assembly of Maltoheptaose-block-Poly(methyl methacrylate): Micelle, Reverse Micelle, and Encapsulation.

    Science.gov (United States)

    Zepon, Karine M; Otsuka, Issei; Bouilhac, Cécile; Muniz, Edvani C; Soldi, Valdir; Borsali, Redouane

    2015-07-13

    The synthesis and the solution-state self-assembly of the "hybrid" diblock copolymers, maltoheptaose-block-poly(methyl methacrylate) (MH-b-PMMA), into large compound micelles (LCMs) and reverve micelle-type nanoparticles, are reported in this paper. The copolymers were self-assembled in water and acetone by direct dissolution method, and the morphologies of the nanoparticles were investigated by dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), atomic force microscopy (AFM), proton nuclear magnetic resonance ((1)H NMR), and fluorescence spectroscopy as a function of the volume fraction of the copolymer hydrophobic block, copolymer concentration, stirring speed, and solvent polarity. The DLS measurements and TEM images showed that the hydrodynamic radius (Rh) of the LCMs obtained in water increases with the copolymer concentration. Apart from that, increasing the stirring speed leads to polydispersed aggregations of the LCMs. On the other hand, in acetone, the copolymers self-assembled into reverse micelle-type nanoparticles having Rh values of about 6 nm and micellar aggregates, as revealed the results obtained from DLS, AFM, and (1)H NMR analyses. The variation in micellar structure, that is, conformational inversion from LCMs to reverse micelle-type structures in response to polarity of the solvent, was investigated by apparent water contact angle (WCA) and (1)H NMR analyses. This conformational inversion of the nanoparticles was further confirmed by encapsulation and release of hydrophobic guest molecule, Nile red, characterized by fluorescence spectroscopy. PMID:25974198

  13. Photoisomerization and reorientational mobility of symmetric carbocyanines in AOT/alkane/polar solvent microemulsions

    Science.gov (United States)

    Dandapat, Manika; Basu, Saswati; Ghosh, Deborin; Mandal, Debabrata

    2014-07-01

    Molecular motion of carbocyanine fluorophores DOCI, DODCI and DTDCI were studied in AOT/n-heptane microemulsions containing added polar solvents: water, methanol or acetonitrile. The response varied remarkably depending on the nature of the fluorophore and polar solvent. When the amount of added polar solvent was low, molecular mobility was invariably retarded, due to a combination of electrostatic and hydrophobic forces that induce the guest fluorophore to cling to the AOT molecules of the host reverse micelle. However, at high amounts of added methanol or water, these interactions diminished considerably, causing increase in the mobility of the guest fluorophores up to different extents.

  14. Neural modeling of bromelain extraction by reversed micelles

    Directory of Open Access Journals (Sweden)

    Ana Maria Frattini Fileti

    2010-04-01

    Full Text Available A pulsed-cap microcolumn was used for bromelain extraction from pineapple juice by reversed micelles. The cationic micellar solution used BDBAC as the surfactant, isooctane as the solvent and hexanol as the co-solvent. In order to capture the dynamic behavior and the nonlinearities of the column, the operating conditions were modified in accordance with the central composite design for the experiment, using the ratio between the light phase flow rate and the total flow rate, and the time interval between pulses. The effects on the purification factor and on total protein yield were modeled via neural networks. The best topology was defined as 16-9-2, and the input layer was a moving window of the independent variables. The neural model successfully predicted both the purification factor and the total protein yield from historical data. At the optimal operating point, a purification factor of 4.96 and a productivity of 1.29 mL/min were obtained.Uma micro-coluna com campânulas pulsantes foi utilizada para a extração de bromelina a partir de suco de abacaxi, usando micelas reversas. A solução catiônica micelar foi composta do surfactante BDBAC, do solvente iso-octano e do co-solvente hexanol. Seguindo um planejamento experimental, perturbações foram impostas à coluna de extração com o objetivo de capturar seu comportamento dinâmico e suas não-linearidades, usando a razão entre a vazão da fase leve e vazão total, e o intervalo de tempo entre os pulsos. Os efeitos das variáveis independentes sobre o fator de purificação e sobre o rendimento em proteínas totais foram modelados via redes neurais artificiais. A melhor topologia de rede obtida foi definida como 16-9-2, usando um esquema de janela móvel no tempo das variáveis independentes. O modelo neural obtido do histórico do processo se mostrou adequado para predizer simultaneamente o fator de purificação e o rendimento do processo em proteínas totais. No ponto ótimo de

  15. Batch and continuous extraction of bromelain enzyme by reversed micelles

    Directory of Open Access Journals (Sweden)

    Ana Maria Frattini Fileti

    2009-10-01

    Full Text Available The main aim of this study was to optimize the conditions for bromelain extraction by reversed micelles from pineapple juice (Ananas comosus. The purification was carried out in batch extraction and a micro-column with pulsed caps for continuous extraction. The cationic micellar solution was made of BDBAC as a surfactant, isooctane as a solvent and hexanol as a co-solvent. For the batch process, a purification factor of 3 times at the best values of surfactant agent, co-solvent and salt concentrations, pH of the back and forward extractions were, 100 mM, 10% v/v, 1 M, 3.5 and 8, respectively. For the continuous operation, independent variables optimal point was determined: ratio between light phase flow rate and total flow rate equal to 0.67 and 1 second for the time interval between the pulses. This optimal point led to a productivity of 1.29 mL/min and a purification factor of 4.96.Este trabalho teve como objetivo principal otimizar as condições para extração da bromelina do suco do abacaxi (Ananas comosus por micelas reversas. A purificação foi feita usando o processo de extração em batelada e contínuo, este último em uma micro-coluna de campânulas pulsantes. A solução micelar catiônica foi preparada com o surfactante BDBAC, i-octano como solvente e hexanol como co-solvente. Na extração em batelada encontrou-se um fator de purificação de 3 vezes, e seus melhores valores de concentração do agente surfactante, co-solvente e sal, de pH da re-extração e extração, foram respectivamente iguais a: 100 mM, 10% v/v, 1 M, 3,5 e 8. Para a operação contínua, as variáveis independentes ótimas foram: 0,67 para a razão entre as taxas de fluxos da fase leve e a total e 1 s para o intervalo de tempo entre pulsos das campânulas. Este ponto ótimo leva a uma produtividade de 1,29 mL/min e a um fator de purificação igual a 4,96.

  16. CTAB/water/chloroform reverse micelles: a closed or open association model?

    Science.gov (United States)

    Klíčová, L'ubica; Sebej, Peter; Štacko, Peter; Filippov, Sergey K; Bogomolova, Anna; Padilla, Marc; Klán, Petr

    2012-10-30

    The micellization of cetyltrimethylammonium bromide (CTAB) in chloroform in the presence of water was examined. Three scenarios of the reverse micelle formation, the closed, open and Eicke's association models, were considered in the interpretation of the experimental data. The growth of the aggregates was observed through the changes of NMR signals of associated water, probing the microenvironment of the premicellar aggregates and the interior of reverse micelles. This technique if combined with isothermal titration calorimetry (ITC) revealed that hydrated surfactant premicellar aggregates are already present at ∼6 mM CTAB. NMR, ITC and conductometry were used to determine the critical micelle concentration (cmc) to be ∼40 mM CTAB. It is suggested that the variation of the cmc values reflects the fact that the NMR analysis indicated the beginning of the reverse micelle formation, whereas conductometry and ITC measurements provided the upper limit and an average value of a so-called apparent cmc, respectively. The cmc values were found to be unaffected by the water content. The presence of reverse micelles, the existence of multiple equilibria, and high polydispersity of the samples were evidenced by DOSY NMR spectroscopy. As a result, we validated Eicke's association model, according to which cyclic inverse micelles are formed by a structural reorganization of linear associates within a narrow concentration range, called the apparent cmc. New experimental results have also been gained for micellization of cetyltrimethylammonium chloride (CTAC) in chloroform in the presence of water; a similar mechanism of reverse micelle formation has been suggested. PMID:23072317

  17. Effect of Confinement on the Properties of Sequestered Mixed Polar Solvents: Enzymatic Catalysis in Nonaqueous 1,4-Bis-2-ethylhexylsulfosuccinate Reverse Micelles.

    Science.gov (United States)

    Durantini, Andres M; Falcone, R Dario; Silber, Juana J; Correa, N Mariano

    2016-06-01

    The influence of different glycerol, N,N-dimethylformamide (DMF) and water mixtures encapsulated in 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/n-heptane reverse micelles (RMs) on the enzymatic hydrolysis of 2-naphthyl acetate by α-chymotrypsin is demonstrated. In the case of the mixtures with DMF and protic solvents it has been previously shown, using absorption, emission and dynamic light-scattering techniques, that solvents are segregated inside the polar core of the RMs. Protic solvents anchor to the AOT, whereas DMF locates to the polar core of the aggregate. Thus, DMF not only helps to solubilize the hydrophobic substrate, increasing its effective concentrations but surprisingly, it does not affect the enzyme activity. The importance of ensuring the presence of RMs, encapsulation of the polar solvents and the corrections by substrate partitioning in order to obtain reliable conclusions is highlighted. Moreover, the effect of a constrained environment on solvent-solvent interactions in homogenous media and its impact on the use of RMs as nanoreactors is stressed. PMID:26891863

  18. pH-Triggered Charge-Reversal Polyurethane Micelles for Controlled Release of Doxorubicin.

    Science.gov (United States)

    He, Wanying; Zheng, Xu; Zhao, Qi; Duan, Lijie; Lv, Qiang; Gao, Guang Hui; Yu, Shuangjiang

    2016-06-01

    A series of pH-triggered charge-reversal polyurethane copolymers (PS-PUs) containing methoxyl-poly(ethylene glycol) (mPEG), carboxylic acid groups, and piperazine groups is presented in this work. The obtained PS-PUs copolymers can form into stable micelles at pH 7.4, which response to a narrow pH change (5.5-7.5) and show a tunable pH-triggered charge-reversal property. Doxorubicin (DOX) is encapsulated into the PS-PU micelles as a model drug. The drug release of DOX-loaded PS-PU micelles shows an obviously stepped-up with reducing the pH. Meanwhile, it is found that the charge-reversal property can improve the cellular uptake behavior and intracellular drug release in both HeLa cells and MCF-7 cells. Additionally, the time-dependent cytotoxicity of the DOX-loaded PS-PU micelles is confirmed by MTT assay. Attributed to the tunable charge-reversal property through changing the molar ratio of piperazine/carboxyl, the PS-PU micelles will be a potential candidate as an intelligent drug delivery system in future studies. PMID:26841363

  19. Hydrogen-bond effects induced by alcohol on the structure and dynamics of ionic reverse micelles

    Science.gov (United States)

    Bardez, E.; Giordano, R.; Jannelli, M. P.; Migliardo, P.; Wanderlingh, U.

    1996-09-01

    In this work we report how the structure of Zn(AOT) 2/H 2O/d-cyclohexane microemulsions is affected by the presence of alcohol (normal pentanol) molecules as cosurfactant. The systems are investigated by small-angle neutron scattering (SANS) and by Fourier transform IR (FTIR) spectroscopy. The SANS technique allows the study of the evolution of the size, the shape and the possible correlation length of concentration fluctuations as a function of water and alcohol content. Moreover FTIR spectra, in the OH stretching region, is quite sensitive to the structural changes of the water, induced by the polarization effects of the polar heads of the micelle surface and the positive counterions and by the presence of the alcohol.

  20. Intrinsic parameters for the structure control of nonionic reverse micelles in styrene: SAXS and rheometry studies.

    Science.gov (United States)

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

    2011-05-17

    Shape, size, and internal structure of nonionic reverse micelle in styrene depending on surfactant chain length, concentration, temperature, and water addition have been investigated using a small-angle X-ray scattering (SAXS) technique. The generalized indirect Fourier transformation (GIFT) method has been employed to deduce real-space structural information. The consistency of the GIFT method has been tested by the geometrical model fittings, and the micellar aggregation number (N(agg)) has been determined. It was found that diglycerol monocaprate (C(10)G(2)), diglycerol monolaurate (C(12)G(2)), and diglycerol monomyristate (C(14)G(2)), spontaneously self-assemble into reverse micelles in organic solvent styrene under ambient conditions. The micellar size and the N(agg) decrease with an increase in surfactant chain length, a scenario that could be understood from the modification of the critical packing parameter (cpp). A clear picture of one-dimensional (1-D) micellar growth was observed with an increase in surfactant weight fraction (W(s)) in the C(10)G(2) system, which eventually formed rodlike micelles at W(s) ≥ 15%. On the other hand, micelles shrunk favoring a rod-to-sphere type transition upon heating. Reverse micelles swelled with water, forming a water pool at the micellar core; the size of water-incorporated reverse micelles was much bigger than that of the empty micelles. Model fittings showed that water addition not only increase the micellar size but also increase the N(agg). Zero-shear viscosity was found to decrease with surfactant chain but increase with W(s), supporting the results derived from SAXS. PMID:21488609

  1. Influence of surfactant structure on reverse micelle size and charge for nonpolar electrophoretic inks.

    Science.gov (United States)

    Parent, Mary E; Yang, Jun; Jeon, Yoocharn; Toney, Michael F; Zhou, Zhang-Lin; Henze, Dick

    2011-10-01

    Electrophoretic inks, which are suspensions of colorant particles that are controllably concentrated and dispersed by applied electric fields, are the leading commercial technology for high-quality reflective displays. Extending the state of the art for high-fidelity color in these displays requires improved understanding and control of the colloidal systems. In these inks, reverse micelles in nonpolar media play key roles in media and particle charging. Here we investigate the effect of surfactant structure on reverse micelle size and charging properties by synthesizing different surfactants with variations in polyamine polar head groups. Small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) were used to determine the micelle core plus shell size and micelle hydrodynamic radius, respectively. The results from SAXS agreed with DLS and showed that increasing polyamines in the surfactant head increased the micelle size. The hydrodynamic radius was also calculated on the basis of transient current measurements and agreed well with the DLS results. The transient current technique further determined that increasing polyamines increased the charge stabilization capability of the micelles and that an analogous commercial surfactant OLOA 11000 made for a lower concentration of charge-generating ions in solution. Formulating magenta inks with the various surfactants showed that the absence of amine in the surfactant head was detrimental to particle stabilization and device performance. PMID:21863832

  2. Rheological measurements in titania gels synthesized from reverse micelles

    Science.gov (United States)

    Romano, S. D.; Kurlat, D. H.

    2000-06-01

    TiO 2 sol and gel systems have been synthesized by hydrolysis of titanium butoxide in microemulsions W/O. Different systems compositions were prepared at constant Wo=[H 2O]/[AOT] and changing R=[H 2O]/[Ti(BuO) 4]. Experimental measurements show a progressive increase of the viscosity with time, characteristic of a sol-gel transition. The rheology of the transition was studied by following the behavior of viscoelastic parameters ( G', G″ and η*) as a function of time at different frequencies. The possibility to apply standard percolation theory was discussed. The application of two alternative growth models — either `fractal growth model' or `nearly linear growth model' — has been analysed.

  3. Static structure factor of polymerlike micelles: Overall dimension, flexibility, and local properties of lecithin reverse micelles in deuterated isooctane

    DEFF Research Database (Denmark)

    Jerke, G.; Pedersen, J.S.; Egelhaaf, S.U.; Schurtenberger, P.

    1997-01-01

    We report a systematic investigation of the static structure factor S(q,c) of polymerlike reverse micelles formed by soybean lecithin and trace amounts of water in deuterated isooctane using small-angle neutron scattering and static light scattering. The experimental data for different...... transformation and square-root deconvolution techniques. We demonstrate that we can determine structural properties such as the micellar cross-section profile and flexibility as well as quantitatively incorporate the influence of micellar growth and excluded-volume effects on S(q,c)....

  4. Selective Affinity Separation of Yeast Alcohol Dehydrogenase by Reverse Micelles with Unbound Triazine Dye*

    Institute of Scientific and Technical Information of China (English)

    张天喜; 刘会洲; 陈家镛

    2001-01-01

    The reversed micelles were formed with cationic cetyltrimethylammonium bromide (CTAB) as surfactant and n-hexanol as cosolvent in the CTAB (50 mmol·L- 1)/hexanol (15% by volume)/hexane system. Cibacron Blue 3GA (CB) as an affinity ligand in the aqueous phase was directly introduced to the reversed micelles with electrostatic interaction between anionic CB and cationic surfactant. High molecular weight (Mr) protein, yeast alcohol dehydrogenase (YADH, Mr = 141000) from baker's yeast, has been purified using the affinity reversed micelles by the phase transfer method. Various parameters, such as CB concentration, pH and ionic strength, on YADH forward and backward transfer were studied. YADH can be transferred into and out from the reversed micelles under mild conditions (only by regulation of solution pH and salt concentration) with the successful recoveryof most YADH activity. Both forward and backward extractions occurred when the aqueous phase pH>pI with electrostatic attraction between YADH and CTAB. The recovery of YADH activity and purification factor have been improved with addition of a small amount of affinity CB. The recovery of YADH activity obtained was 99% and the purification factor was about 4.0-fold after one cycle of full forward and backward extraction. The low ionic strength in the initial aqueous phase might be responsible for the YADH transfer into the reversed micellar phase.

  5. CTAB/water/chloroform reverse micelles: a closed or open association model?

    Czech Academy of Sciences Publication Activity Database

    Klíčová, L.; Šebej, P.; Štacko, P.; Filippov, Sergey K.; Bogomolova, Anna; Padilla, M.; Klán, P.

    2012-01-01

    Roč. 28, č. 43 (2012), s. 15185-15192. ISSN 0743-7463 R&D Projects: GA ČR GAP108/12/0640 Institutional support: RVO:61389013 Keywords : CTAB * reverse micelles * AFM Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.187, year: 2012

  6. Photophysics of three delocalized lipophilic cations in reverse micelles: A fluorescence spectroscopy study

    International Nuclear Information System (INIS)

    In this paper, aiming at the trans-membrane transport properties of the different DLCs related with the cytotoxicities, we have studied photophysics of DLCs in RMs. MTT assays indicated that DLC 1 were more cytotoxic than DLC 2 and 3. Steady-state absorption and fluorescence method have been used to characterize the binding model of three DLCs (1, 2, and 3) in RMs and bovine serum albumin (BSA). The progressive red-shift of compound 1 indicated that it can experience the hydrophilic and hydrophobic environment owing to the rigid structure, thus it can more easily cross the double membrane of cell than compounds 2 and 3. In conclusion, we simulated a model of compound 1 in RMs. The present study of F16 derivatives in microenvironment would provide some useful information to the cell membrane simulation and design of DLCs. - Graphical abstract: Aiming at the trans-membrane transport properties of the different DLCs related with the antitumor properties, MTT assay, steady-state absorption and fluorescence method have been used to characterize the binding model of three DLCs (1, 2, and 3) in reverse micelles (RMs) and bovine serum albumin (BSA). Highlights: ► The drugs penetrating into the reverse micelles core were used to mimic the feature of drug trans-membrane transport. ► Compound 1 was incorporated into the Stern Layer of reverse micelles, while compound 3 was not. ► Reverse micelles would be used as a biomimic for drug designing and screening.

  7. Hierarchical assembly of block copolymer micelles into reversible networks: MC simulations

    Science.gov (United States)

    Wang, Zilu; Dormidontova, Elena

    2015-03-01

    The rapid development of nanoscience has considerably expanded the range of building blocks for complex self-assembled nanostructure formation, which show great potential for numerous advanced applications. We apply Monte Carlo simulations to gain understanding of molecular mechanism of self-assembly of nanostructures formed by diblock copolymer micelles interconnected by means of metal-ligand complexation. These systems exhibit interesting chemical and mechanical stimuli-responsive behavior and possess two levels of self-assembly: 1) self-assembly of diblock copolymers into micelles and 2) reversible inter-micelle bridging by coordination bonding between metal ions and ligands attached to the corona of nanoparticles, which is responsible for the network viscoelastic properties. Using MC simulations we investigate the effect of metal-ligand complexation on diblock-copolymer micelle formation and vice versa. We analyze the extent of intra- and inter-micelle loops and bridges formed by metal-ligand complexation in relation to the degree of crosslinking and elastic properties of the network. The effect of polymer concentration, hydrophilic block length, metal to oligomer ratio and type of complexation (2:1 or 3:1) on equilibrium properties of reversible networks will be discussed.

  8. Selective Affinity Separation of Yeast Alcohol Dehydrogenase by Reverse Micelles with Unbound Triazine Dye

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The reversed micelles were formed with cationic cetyltrimethylammonium bromide (CTAB) as surfac tant and n-hexanol as cosolvent in the CTAB (50mmol.L-1)/hexanol (15% by volume)/hexane system. Cibacron Blue 3GA (CB) as an affinity ligand in the aqueous phase was directly introduced to the reversed micelles with electrostatic interaction between anionic CB and cationic surfactant. High molecular weight (Mr) protein, yeast alcohol dehydrogenase (YADH, Mr = 141000) from baker's yeast, has been purified using the affinity reversed micelles by the phase transfer method. Various parameters, such as CB concentration, pH and ionic strength, on YADH forward and backward transfer were studied. YADH can be transferred into and out from the reversed mi celles under mild conditions (only by regulation of solution pH and salt concentration) with the successful recovery of most YADH activity. Both forward and backward extractions occurred when the aqueous phase pH>pI with electrostatic attraction between YADH and CTAB. The recovery of YADH activity and purification factor have been improved with addition of a small amount of affinity CB. The recovery of YADH activity obtained was ~99% and the purification factor was about 4.0-fold after one cycle of full forward and backward extraction. The low ionic strength in the initial aqueous phase might be responsible for the YADH transfer into the reversed micellar phase.

  9. Formation of reversed micelles and W/O microemulsions of butyldodecyldimethylammonium bromide in chlorobenzene

    International Nuclear Information System (INIS)

    The limiting amounts of water solubilized by butyldodecyldimethylammonium bromide (BDDAB) in chlorobenzene increased rapidly at 0.01 molkg-1 surfactant concentration at 30degC. Using 1H NMR, fluorescence, and near infrared spectroscopic techniques, the solubilized states of water in the region obtained above 0.01 molkg-1 were examined as a function of Rw (=[H2O]/[BDDAB]) at various concentrations of surfactant. It was found from these spectral features that three types of water exist in varying proportions in the interior of reversed micelles, i.e., below Rw = 4 water is bound directly to the ionic head groups of the surfactant, in the range of Rw = 4-10 the succeeded water is held together with the hydrated ionic groups by hydrogen bonds, and above Rw = 10 bulk-like water is built up. These types of water could be discussed in connection with the formation of reversed and swollen micelles or W/O microemulsions. Further, the minimum Rw required for the formation of swollen micelles and W/O microemulsion and the critical swollen micelles or W/O microemulsion concentration could be estimated. (author)

  10. Small angle X-ray scattering studies to access the influence of bovine serum albumin (BSA) and carbonic anhydrase (Boca) on the size and interaction among Aerosol-O T reversed micelles as a function of the micellar hydration degree

    International Nuclear Information System (INIS)

    Full text: Reversed micelles (RMs) of AOT (sodium bis-2-ethylhexyl sulfosuccinate) has constitute an efficient system to investigate membrane interaction and physical chemical behavior of short biologically active peptides, proteins and enzymes in water controlled environment and apolar medium. Information may be obtained from protein-membrane interaction, including solubilization, binding location, conformational changes, activity size droplet-dependent, and changes in the properties of RM environment, useful in studies in biocatalysis and bioseparation systems [1]. In this work, changes in the structural features and interactive forces among AOT RMs in hexane were monitored in several stages of micellar hydration W (= [buffer]/[0.1M AOT]), and in the presence of BSA (66.5 kDa) and BCA (30 Kda), by SAXS. The interactive forces between the RMs with proteins were analyzed within the framework of repulsion and attractive interaction potentials through the pairing stick hardsphere (PSHS) model [2]. In this way, the spherical core radius to the system of pure AOT RMs at W = 4, 10, 20 and 30 were respectively 15, 22, 33 and 43 A (20% of polydispersity), evaluated from the particle form factor P(q) modeling [1]. The PSHS analysis from SAXS curves of AOT RMs with BSA and BCA at smaller droplets size of 4 and 10, showed, respectively, an interplay between attractive and repulsive interactions between the micelles (attractive component in S(q) was predominant) with the preservation of the discrete RM radius in the presence of protein. On the other hand, for protein confined in the bigger RM droplet size with W=30, the attractive inter micellar forces were of minor importance for BSA and the appearing of a predominant repulsive hard sphere component in SAXS curves accompanied by a decreasing of the micellar radius to 36 A were detected. For BCA, however, at higher W (30), a phase separation was observed probably associated to the formation of unstable large BCA aggregates

  11. Mutation detection in the drug-resistant hepatitis B virus polymerase gene using nanostructured reverse micelles.

    Science.gov (United States)

    Park, Lian-Chun; Maruyama, Tatsuo; Kamiya, Noriho; Goto, Masahiro; Kuma, Hiroyuki; Hamasaki, Naotaka

    2004-11-01

    The emergence of drug-resistant hepatitis B virus (HBV) has been reported in patients with prolonged administration of lamivudine, which is a potent drug for the prevention of HBV infection. Lamivudine-resistant HBV has several types of mutations at the YMDD motif of its DNA polymerase. We successfully demonstrated that monitoring the hybridization behavior in nanostructured reverse micelles enables us to detect single nucleotide polymorphisms (SNPs). With the aid of reverse micelles, a model 40-mer oligonucleotide containing a single-base substitution was clearly distinguished from the normal, complementary oligonucleotide. In addition, we extended this technique to a high-throughput analysis. The results obtained with a 96-well micro-plate reader indicated the possibility of SNPs detection toward multiple samples of patients. PMID:15566158

  12. Protein separation and enrichment by counter-current chromatography using reverse micelle solvent systems.

    Science.gov (United States)

    Shen, Ching-Wei; Yu, Tiing

    2007-06-01

    A protein mixture consisting of myoglobin, cytochrome c, and lysozyme was separated by high-speed counter-current chromatography using a two-phase aqueous/reverse micelle-containing organic solvent system. About 50% stationary phase retention ratio was obtained in most chromatographic experiments. Separations were manipulated mainly by pH gradients that controlled the electrostatic interactions between the protein molecules and reverse micelles. Separations were further improved by incorporating an ionic strength gradient along with the pH gradient. Control of ionic strength in the aqueous solution helped fine-tune protein partitioning between the stationary and mobile phases. Although non-specific protein interactions affected baseline resolution, recovery of cytochrome c and lysozyme reached 90% and 82%. Furthermore, concentration or enrichment of these two proteins was achieved from a large-volume sample load. This technique can potentially be employed in the recovery and enrichment of proteins from large-volume aqueous solutions. PMID:17289061

  13. Improvement in electric and dielectric properties of nanoferrite synthesized via reverse micelle technique

    Science.gov (United States)

    Thakur, Sangeeta; Katyal, S. C.; Singh, M.

    2007-12-01

    Nano nickel zinc ferrite (Ni0.58Zn0.42Fe2O4) with fascinating dielectric properties which reveal a direction for application was synthesized by reverse micelle technique. Dielectric constant and dielectric losses are controlled up to a measurement temperature of around 473K at higher frequency range of 9-19MHz. The dielectric loss of the sample investigated at room temperature is only 0.003 at 19MHz. The presently studied nanoferrite also exhibits a high value of dc resistivity, 108Ωcm. High resistivity and low dielectric constant and loss can be corelated to small grain size and better compositional stoichiometry obtained as a result of processing via reverse micelle technique at low sintering temperature (773K).

  14. Photorheologically reversible micelle composed of polymerizable cationic surfactant and 4-phenylazo benzoic acid☆

    Institute of Scientific and Technical Information of China (English)

    Jie Chen; Bo Fang; Hao Jin; Licheng Yu; Meng Tian; Kejing Li; Leiping Jin; Mo Yang

    2016-01-01

    A photorheologically reversible micelle composed of polymerizable cationic surfactant n-cetyl dimethylallyl am-monium chloride (CDAAC) and trans-4-phenylazo benzoic acid (trans-ACA) was prepared. The effects of molar ratio of CDAAC/trans-ACA, time of UV and visible light irradiation and temperature on the rheological properties of micellar system were investigated. The results show that before UV irradiation the system with an optimum CDAAC/trans-ACA molar ratio of 1.4 forms viscoelastic micelles at 45 °C. After 365 nm UV irradiation, the viscos-ities of micel e systems with different concentrations at fixed molar ratio of 1.4 are decreased by 85%–95%. The CDAAC/trans-ACA (14 mmol·L−1/10 mmol·L−1) micel e system exhibits shear thinning property and its viscos-ity is decreased obviously with the increases of UV irradiation time less than 1 h. The rheological process during UV irradiation for CDAAC/trans-ACA (14 mmol·L−1/10 mmol·L−1) micelle proves that viscosity, elastic modulus G′and viscous modulus G″will reduce quickly with the UV light. Furthermore, the micelle system after 1 h UV-irradiation is able to revert to its initial high viscosity with 460 nm visible light irradiation for 4 h, and the micelle can be cycled between low and high viscosity states by repetitive UV and visible light irradiations. The UV–Vis spectra of CDAAC/trans-ACA micelle indicate that its photosensitive rheological properties are related closely to photoisomerization of trans-ACA to cis-ACA.

  15. Synthesis of single-walled carbon nanotube networks using monodisperse metallic nanocatalysts encapsulated in reverse micelles

    OpenAIRE

    Gayduchenko Igor A.; Fedorov Georgy E.; Ibragimov Ramil A.; Stepanova Tatiana S.; Gazaliev Arsen S.; Vysochanskiy Nikolay A.; Bobrov Yuri A.; Malovichko Anton M.; Sosnin Ilya M.; Bobrinetskiy Ivan I.

    2016-01-01

    We report on a method of synthesis of single-walled carbon nanotubes percolated networks on silicon dioxide substrates using monodisperse Co and Ni catalyst. The catalytic nanoparticles were obtained by modified method of reverse micelles of bis-(2-ethylhexyl) sulfosuccinate sodium in isooctane solution that provides the nanoparticle size control in range of 1 to 5 nm. The metallic nanoparticles of Ni and Co were characterized using transmission electron mi...

  16. The epilatory effects of trypsin on human skin, applied via lecithin reverse micelles

    OpenAIRE

    Protopapa, E. E.; Xenakis, Aristotelis; Avramiotis, S.; Prodromou, E.V.; Koukaki, S.M.

    2008-01-01

    A method of epilation using reverse micelles containing the proteolytic enzyme, trypsin, is described based on previous experimental findings on degenerative effects of proteolytic enzymes on hair follicles and follicle stem cells of guinea pigs and mice. The method involves rubbing of the preparation on wax epilated skin and leads to removal of hair from various skin regions, such as face, shoulders, arms and legs. The many advantages of this method renders it the method of choice for hai...

  17. Modulation of dynamics and reactivity of water in reverse micelles of mixed surfactants.

    Science.gov (United States)

    Mitra, Rajib Kumar; Sinha, Sudarson Sekhar; Verma, Pramod Kumar; Pal, Samir Kumar

    2008-10-16

    In this contribution, we attempt to correlate the change in water dynamics in a reverse micellar (RM) core caused by the modification of the interface by mixing an anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), and a nonionic surfactant, tetraethylene glycol monododecyl ether (Brij-30), at different proportions, and its consequent effect on the reactivity of water, measured by monitoring the solvolysis reaction of benzoyl chloride (BzCl). The dimension of the RM droplets at different mixing ratios of AOT and Brij-30 (X(Brij-30)) has been measured using dynamic light scattering (DLS) technique. The physical properties of the RM water have been determined using Fourier transform infrared spectroscopy (FTIR) and compressibility studies, which show that with increasing X(Brij-30), the water properties tend toward that of bulk-like water. The solvation dynamics, probed by coumarin 500 dye, gets faster with X(Brij-30). The rotational anisotropy studies along with a wobbling-in-cone analysis show that the probe experiences less restriction at higher X(Brij-30). The kinetics of the water-mediated solvolysis also gets faster with X(Brij-30). The increased rate of solvolysis has been correlated with the accelerated solvation dynamics, which is another consequence of surfactant headgroup-water interaction. PMID:18808089

  18. Shape evolution of Cu2S nanostructures in Triton X-100/cyclohexane/water reverse micelles

    International Nuclear Information System (INIS)

    The shape evolution of Cu2S nanostructures, which were produced in Triton X-100/cyclohexane/water reverse micelles, was investigated by the transmission electron microscopy technique as a function of aging time, and the effect of the molar ratio of water to surfactant on the size and shape of Cu2S nanostructures was also discussed. The results suggest that at the initial stage the nucleation process was dominant and the shape of Cu2S nanostructures was preferably confined by the reverse micelle droplets and took spherical forms. With the extension of the aging time, the growth gradually governed the process and the shape of Cu2S nanostructures evolved first to nanorods, and then to nanowires gradually. The formation of one-dimensional Cu2S nanostructures is attributed to a directed aggregation growth process mediated by reverse micelle droplets, which was confirmed by high-resolution transmission electron microscopy. Furthermore, the size and shape of Cu2S nanostructures can be controlled by changing the molar ratio of water to surfactant

  19. Structural Properties of Water Nano-pockets Encapsulated in Polymerized Reverse Micelles

    Science.gov (United States)

    Urquidi, Jacob; Banuelos, Jose L.; Levinger, Nancy

    2009-03-01

    Reverse micelles, that is, small surfactant coated droplets of polar solvent, can form in a range of systems of varying surfactant and polar solvent. SANS has been used to characterize the shape, size and polydispersity of these reverse micelle systems which are macroscopically clear but nanoscopically heterogeneous. Particular sensor applications have been developed using a reverse micellar starting material to create a sample that is macroscopically a robust solid with encapsulated nanoscopic pockets of fluid. This poster will discuss the nanopockets of the fluid phase (water in this case) within the matrix as investigated by small angle X-ray scattering (SAXS) and neutron scattering techniques. The SAXS technique was used to investigate the polydispersity, shape, and distribution of the nanopockets of fluid. Neutron scattering was used to lend insight into the nature of the water encapsulated within these micelles by looking at the position, width, and height of the First Sharp Diffraction Peak (FSDP) to probe the physical perturbations that the water is subject to.

  20. Tunable parameters for the structural control of reverse micelles in glycerol monoisostearate/oil systems: a SAXS study.

    Science.gov (United States)

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

    2009-04-21

    Formation of reverse micelles in surfactant/oil binary systems without water addition and the tunable parameters for the structure control of such micelles are presented. The small-angle X-ray scattering (SAXS) technique has been used for the structural characterization of micelles. It has been found that the nonionic surfactant glycerol monoisostearate (abbreviated as iso-C18G1) forms reverse micelles in different organic solvents such as cyclohexane, n-decane, and n-hexadecane without the addition of water. The structure (shape and size) of the reverse micelles has been found to depend on the solvent nature (alkyl chain length of oil), composition, temperature, and added water. Phase behavior study has shown that iso-C18G1 forms isotropic single-phase solutions in the aforementioned oils at 25 degrees C. At lower temperatures (reverse micellar aggregates. Small globular types of micelles are found in the iso-C18G1/cyclohexane system. On the other hand, elongated ellipsoidal prolatelike or rodlike micelles are found in iso-C18G1/decane or iso-C18G1/hexadecane systems. The underlying mechanism of this structural evolution may be explained in terms of the transfer free energy of hydrophilic glycerol moiety from hydrophilic to hydrophobic environment of oils with different chain lengths. Besides, the penetration of oils to the lipophilic chain of the surfactant in reverse micellar systems differs depending on the chain length of oils. Lowering temperature and increasing surfactant concentration similarly lead to micellar growth while the cross-section structure remains essentially unchanged. Addition of trace water induced micellar growth, which is accompanied by the rapid swelling of the micellar core. The results obtained by this study demonstrate that the solvent nature, temperature, composition, and water addition can be the tunable parameters for the size, shape, and internal structure control of the iso-C18G1-based reverse micelles. PMID:19243155

  1. Preparation and characterization of MnZn-ferrite nanoparticles using reverse micelles

    Science.gov (United States)

    Morrison, S. A.; Cahill, C. L.; Carpenter, E. E.; Calvin, S.; Harris, V. G.

    2003-05-01

    Research on manganese zinc ferrites (MZFO) has undergone a renewal in recent years as advances in synthetic techniques promise smaller grain sizes and corresponding changes in material properties. Current techniques for nanoscale synthesis of ferrites, however, produce a broad distribution of particle sizes, thus limiting the density of compacted materials, and consequently altering coercivity [C. Rath et al., J. Appl. Phys. 91, 2211 (2002)]. To minimize porosity, bulk materials need to be pressed from uniform particles. Wet chemical synthesis performed in reverse micelles, in which pools of water are encased by surfactant molecules in an excess volume of oil, provides the greatest control over size and morphology. During synthesis, surfactant molecules keep particles separated and restrict particle growth. This affords greater control over the size and shape of the particles grown in the micelles and commonly results in highly uniform morphologies [J. P. Chen et al., J. Appl. Phys. 76, 6316 (1994); C. Liu et al., J. Phys. Chem. B. 104, 1141 (2000)]. As a first step, it is necessary to produce pure phase, nanosized ferrite particles, therefore in this study, analysis of the powder of a sample prepared by a reverse micelle technique is compared to a sample prepared by a traditional ceramic method. Future studies will focus on the porosity and subsequent material properties of compacted forms of the pure phase samples.

  2. Effect of urea on bovine serum albumin in aqueous and reverse micelle environments investigated by small angle X-ray scattering, fluorescence and circular dichroism

    International Nuclear Information System (INIS)

    The influence that urea has on the conformation of water-soluble globular protein, bovine serum albumin (BSA), exposed directly to the aqueous solution as compared to the condition where the macromolecule is confined in the Aerosol-OT (AOT - sodium bis-2-ethylhexyl sulfosuccinate)/n-hexane/water reverse micelle (RM) is addressed. Small angle X-ray scattering (SAXS), tryptophan (Trp) fluorescence emission and circular dichroism (CD) spectra of aqueous BSA solution in the absence and in the presence of urea (3M and 5M) confirm the known denaturing effect of urea in proteins. The loss of the globular native structure is observed by the increase in the protein maximum dimension and gyration radius, through the Trp emission increase and maximum red-shift as well as the decrease in helix content. In RMs, the Trp fluorescence and CD spectra show that BSA is mainly located in its interfacial region independently of the micellar size. Addition of urea in this BSA/RM system also causes changes in the Trp fluorescence (emission decrease and maximum red-shift) and in the BSA CD spectra (decrease in helix content), which are compatible with the denaturation of the protein and Trp exposition to a more apolar environment in the RM. The fact that urea causes changes in the protein structure when it is located in the interfacial region (evidenced by CD) is interpreted as an indication that the direct interaction of urea with the protein is the major factor to explain its denaturing effect. (author)

  3. Effect of surfactants on the properties of hydrotalcites prepared by the reverse micelle method

    Energy Technology Data Exchange (ETDEWEB)

    Holgado, Patricia H., E-mail: h.holgado@usal.es; Holgado, María J., E-mail: holgado@usal.es; San Román, María S., E-mail: sanroman@usal.es; Rives, Vicente, E-mail: vrives@usal.es

    2015-02-01

    Layered double hydroxides with the hydrotalcite-type structure have been prepared by the reverse micelles method. The layer cations were Ni{sup 2+} and Fe{sup 3+} in all cases and the interlayer anion was carbonate. We have studied the effect of the surfactant used (with linear chains of different lengths, or cyclic) and the effect of the pH on the properties of the solids formed. These have been characterized by element chemical analysis, powder X-ray diffraction, thermogravimetric analysis, temperature-programmed reduction, FT-IR and Vis–UV spectroscopies and scanning electron microscopy. It has been found that the samples prepared at pH 9 are more crystalline than those prepared at pH 11 and their crystallite sizes are always larger than for samples prepared by the conventional precipitation method. Surfactants with cyclic organic chains lead to a larger crystallite size, probably because the water pool vesicle where the crystallite grows is larger due to sterical hindrance of the organic chains. - Graphical abstract: Layered double hydroxides with the hydrotalcite-type structure with Ni{sup 2+} and Fe{sup 3+} cations in the layers have been prepared by the reverse micelles method. Different surfactants were used at different pH synthesis. Samples prepared at pH 9 are higher crystalline than those prepared at pH 11. Surfactants with cyclic organic chains lead to a larger crystallite size. - Highlights: • Hydrotalcites were prepared by the micelles reverse method. • Straight alkyl or cyclic chain surfactants were used. • All hydrotalcites are well crystallized at pH = 9 and 11. • The crystallite size depends on the linear/cyclic nature of the surfactant chain.

  4. Molecular Thermodynamic Modeling of Reverse Micelles and Water-in-Oil Microemulsions.

    Science.gov (United States)

    Lukanov, Boris; Firoozabadi, Abbas

    2016-04-01

    Surfactant aggregation plays an important role in a variety of chemical and biological nanoscale processes. On a larger scale, using small amounts of amphiphiles compared to large volumes of bulk-phase modifiers can improve the efficiency and reduce the environmental impact of many chemical and industrial processes. To model ternary mixtures of polar, nonpolar, and amphiphilic molecules, we develop a molecular thermodynamic theory for polydisperse water-in-oil (W/O) droplet-type microemulsions and reverse micelles based on global minimization of the Gibbs free energy of the system. The incorporation of size polydispersity into the theoretical formulation has a significant effect on the Gibbs free energy landscape and allows us to accurately predict micelle size distributions and micelle size variation with composition. Results are presented for two sample ionic surfactant/water/oil systems and compared with experimental data. By predicting the structural and compositional characteristics of w/o microemulsions, the molecular thermodynamic approach provides an important bridge between the modeling of ternary systems at the molecular and the macroscopic level. PMID:26919199

  5. Magnetic properties of isolated Co nanoparticles in SiO 2 capsule prepared with reversed micelle

    Science.gov (United States)

    Haeiwa, Tetsuji; Segawa, Kazuhiro; Konishi, Kenji

    Magnetic properties and thermal stability of cobalt nanoparticles encapsulated in SiO 2 prepared with the reversed micelle technique with various w were investigated. The average diameters of the Co nanoparticles and SiO 2 capsules were about 2.9 and about 5.2 nm. The magnetization curves of Co nanoparticles exhibit superparamagnetic nature. After annealing up to 673 K in vacuum, the magnetization increases by a factor of 2.4 and the average diameter of the Co particles increases by a factor of 1.3, although shape and size of the SiO 2 capsules were kept.

  6. Superparamagnetic properties nano Ni-Zn ferrite synthesized via reverse micelle technique

    International Nuclear Information System (INIS)

    Nanocrystalline nickel-zinc ferrite (Ni0.58Zn0.42Fe2O4) with average grain size of 9 nm was synthesized by reverse micelle technique. The size of particles was confirmed by XRD, TEM. Synthesized, as dried and subsequently calcined powders were characterized in terms of their magnetic properties with the use of SQUID suseptometer. Ferrite nanoparticles revealed the superparamagnetism at room temperature and shows negligible hysteresis at low temperature (5 K). Saturation magnetization of the as synthesized powders is low as compared to its bulk counterpart. (author)

  7. Magnetic properties of isolated Co nanoparticles in SiO2 capsule prepared with reversed micelle

    International Nuclear Information System (INIS)

    Magnetic properties and thermal stability of cobalt nanoparticles encapsulated in SiO2 prepared with the reversed micelle technique with various w were investigated. The average diameters of the Co nanoparticles and SiO2 capsules were about 2.9 and about 5.2 nm. The magnetization curves of Co nanoparticles exhibit superparamagnetic nature. After annealing up to 673 K in vacuum, the magnetization increases by a factor of 2.4 and the average diameter of the Co particles increases by a factor of 1.3, although shape and size of the SiO2 capsules were kept

  8. Controlling the Microstructure of Reverse Micelles and Their Templating Effect on Shaping Nanostructures.

    Science.gov (United States)

    Sharma, Soma; Yadav, Nitin; Chowdhury, Pramit K; Ganguli, Ashok K

    2015-08-27

    Reverse micelles as nanoreactors have been most successful in designing nanostructures of different sizes and shapes. Nevertheless, important questions regarding the explicit roles of intrinsic parameters in modifying soft colloid templates which eventually give rise to variety of nanostructures are still unresolved. In this paper, we have focused on this challenging aspect of microemulsion based synthesis of nanostructures, i.e., how the tunable parameters like water to surfactant molar ratio, solvent properties, and surfactant structure modify the microstructure (size/shape) of reverse micelles (surfactant/cosurfactant/oil/water). Further, we have elucidated the correlation between these nanoreactors with the size and morphology of the evolving nanostructures within the aqueous core (using in situ studies) as well as the finally obtained nanostructures. We have employed fluorescence correlation spectroscopy (FCS), small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and transmission electron microscopy (TEM) to obtain details on the microstructural transformation of reverse micelles and their templating behavior on designing nanostructures, at (near) single droplet level and in an ensemble. The structure (size/shape) of nanoreactors, i.e., reverse micelles, finally guides the size and shape of nanostructures. As the water content increases, it induces the micellar growth and subsequently the growth of nanostructures develops linearly up to a critical value beyond which the finite bending modulus of surfactant film triggers the structural rearrangement of microemulsion droplets (MEDs) and the linear plot shows deviation. Bulkiness of the solvent molecules modulates the ME droplets, and MEDs encapsulates nanostructures by influencing the curvature and rigidity of the surfactant film and results in smaller dimensions of the micellar core, which leads to nanostructures with large aspect ratio. The origin of this structural evolution may be explained

  9. Fabrication and Characterization of Cobalt Iron Oxide Nanoparticles by a Reverse Micelle Process

    International Nuclear Information System (INIS)

    The preparation of CoFe2O4 nanoparticles in Igepal CO-520-cyclohexane-water reverse micelle solutions has been studied. Transmission electron microscopy and X-ray diffraction pattern analyses revealed the resultant particles to be CoFe2O4. The average size and distribution of synthesized particles calcined at 6000C for 2 hrs were in the range of 30 to 70 nm and broaden, respectively. The phase of synthesized particles was crystalline. The magnetic behavior of the synthesized particles was ferromagnetism. The effects of synthesis parameters, such as the molar ratio of water to surfactant and calcination temperature, are discussed

  10. Microstructure determination of AOT + phenol organogels utilizing small-angle X-ray scattering and atomic force microscopy.

    Science.gov (United States)

    Simmons, B A; Taylor, C E; Landis, F A; John, V T; McPherson, G L; Schwartz, D K; Moore, R

    2001-03-14

    Dry reverse micelles of the anionic twin-tailed surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) dissolved in nonpolar solvents spontaneously form an organogel when p-chlorophenol is added in a 1:1 AOT:phenol molar ratio. The solvents used were benzene, toluene, m-xylene, 2,2,4-trimethylpentane (isooctane), decane, dodecane, tetradecane, hexadecane, and 2,6,10,14-tetramethylpentadecane (TMPD). The proposed microstructure of the gel is based on strands of stacked phenols linked to AOT through hydrogen bonding. Small-angle X-ray scattering (SAXS) spectra of the organogels suggest a characteristic length scale for these phenol-AOT strands that is independent of concentration but dependent on the chemical nature of the nonpolar solvent used. Correlation lengths determined from the SAXS spectra indicate that the strands self-assemble into fibers. Direct visualization of the gel in its native state is accomplished by using tapping mode atomic force microscopy (AFM). It is shown that these organogels consist of fiber bundle assemblies. The SAXS and AFM data reinforce the theory of a molecular architecture consisting of three length scales-AOT/phenolic strands (ca. 2 nm in diameter) that self-assemble into fibers (ca. 10 nm in diameter), which then aggregate into fiber bundles (ca. 20-100 nm in diameter) and form the organogel. PMID:11456891

  11. Molecular simulation and experimental study of CO2 absorption in ionic liquid reverse micelle.

    Science.gov (United States)

    Shi, Wei; Hong, Lei; Damodaran, Krishnan; Nulwala, Hunaid B; Luebke, David R

    2014-12-01

    The structure and dynamics for CO2 absorption in ionic liquid reverse micelle (ILRM) were studied using molecular simulations. The ILRM consisted of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) ionic liquid (IL) as the micelle core, the benzylhexadecyldimethylammonium ([BHD](+)) chloride ([Cl](-)) was the cationic surfactant, and benzene was used as the continuous solvent phase in this study. The diffusivity values of this ILRM system were also experimentally determined. Simulations indicate that there is ion exchange between the IL anion ([BF4](-)) and the surfactant anion ([Cl](-)). It was also found that the [bmim][BF4] IL exhibits small local density at the interface region between the IL core and the [BHD](+) surfactant cation layer, which leads to a smaller density for the [bmim][BF4] IL inside the reverse micelle (RM) compared with the neat IL. These simulation findings are consistent with experimental results. Both our simulations and experimental results show that [bmim][BF4] inside the RM diffuses 5-26 times faster than the neat IL, which is partly due to the fast particle diffusion for the ILRM nanodroplet (IL and surfactant) as a whole in benzene solvent compared with neat [bmim][BF4] diffusion. Additionally, it was found that [bmim][BF4] IL solved in benzene diffuses 2 orders of magnitude faster than the neat IL. Lastly, simulations show that CO2 molecules are absorbed in four different regions of the ILRM system, that is, (I) in the IL inner core, (II) in the [BHD](+) surfactant cation layer, (III) at the interface between the [BHD](+) surfactant cation layer and benzene solvent, and (IV) in the benzene solvent. The CO2 solubility was found to decrease in the order II > III ∼ IV > I, while the CO2 diffusivity and permeability decrease in the following order: IV > III > II > I. PMID:25382316

  12. Mixed reverse micelles facilitated downstream processing of lipase involving water-oil-water liquid emulsion membrane.

    Science.gov (United States)

    Bhowal, Saibal; Priyanka, B S; Rastogi, Navin K

    2014-01-01

    Our earlier work for the first time demonstrated that liquid emulsion membrane (LEM) containing reverse micelles could be successfully used for the downstream processing of lipase from Aspergillus niger. In the present work, we have attempted to increase the extraction and purification fold of lipase by using mixed reverse micelles (MRM) consisting of cationic and nonionic surfactants in LEM. It was basically prepared by addition of the internal aqueous phase solution to the organic phase followed by the redispersion of the emulsion in the feed phase containing enzyme, which resulted in globules of water-oil-water (WOW) emulsion for the extraction of lipase. The optimum conditions for maximum lipase recovery (100%) and purification fold (17.0-fold) were CTAB concentration 0.075 M, Tween 80 concentration 0.012 M, at stirring speed of 500 rpm, contact time 15 min, internal aqueous phase pH 7, feed pH 9, KCl concentration 1 M, NaCl concentration 0.1 M, and ratio of membrane emulsion to feed volume 1:1. Incorporation of the nonionic surfactant (e.g., Tween 80) resulted in remarkable improvement in the purification fold (3.1-17.0) of the lipase. LEM containing a mixture of nonionic and cationic surfactants can be successfully used for the enhancement in the activity recovery and purification fold during downstream processing of enzymes/proteins. PMID:24930827

  13. Structural and magnetic properties of nano nickel-zinc-indium ferrite synthesized via reverse micelle technique

    International Nuclear Information System (INIS)

    Full text: Nano nickel-zinc-indium ferrites (Ni0.58Zn0.42InxFe2-xO4) with varied quantities of indium (x = 0, 0.1, 0.2) have been chemically synthesized through a reverse micelle reaction and investigated by x-ray diffraction, Transmission electron microscopy and by magnetic and Moessbauer spectral studies. Here a comparison between low-temperature and room temperature Moessbauer spectra is presented. Bulk samples were prepared by annealing reverse micelle synthesized NZIFO nanoparticles at 1473 K. Here a comparison between nano and bulk samples is presented. The dependence of Moessbauer parameters, viz, isomer shift, quadrupole splitting, linewidth and hyperfine magnetic field on In3+ concentration have been discussed. Moessbauer results are also supported by magnetization data. With these interesting ferromagnetic properties indium substituted nano nickel-zinc ferrites have potential applications in magnetic storage data. The dependence of Moessbauer parameters on bulk and nano NZIFO particles at 5 K and 300 K has been studied. Detailed Moessbauer and magnetic measurements, as well as the interest of these materials both for applied science perspectives are presented

  14. The characteristic properties of PEDOT nano-particle based on reversed micelle method

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Based on the study of a new type of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT),this paper focuses on the preparation and the materials properties of PEDOT nanoparticles made by reversed micelle method.Investigations on optical,electrical and the thermal stability of PEDOT nanoparticles were carried out.The main results were as follows: The small-sized PEDOT nanoparticles were prepared by different methods,such as ultraviolet/visible (UV-Vis) spectroscopy,fourier-transform infrared (FT-IR) spectrum,scanning electron microscopy (SEM) and so on.The Bragg peaks of nanoparticles at 6.7°,12.7°,25° were observed by XRD and the good orientation of molecular chain was attributed to the effective doping of toluene-p-sulfonic acid,which also resulted in an enhancement of thermal stability of nanoparticles compared with the conventional PEDOT.Furthermore,the gas sensitivity of nanoparticles deposited on quartz crystal microbalance (QCM) was studied and the nanopartices deposited device exhibited excellent sensitivity to HCl gas at low concentration.Gas sensitivity of the nanoparticles by the reverse micelle was better than that of the common PEDOT particles.

  15. Synthesis of TiO2 nanoparticles utilizing hydrated reverse micelles in CO2.

    Science.gov (United States)

    Lim, Kwon Taek; Hwang, Ha Soo; Ryoo, Won; Johnston, Keith P

    2004-03-16

    Titanium dioxide nanoparticles were produced by the controlled hydrolysis of titanium tetraisopropoxide (TTIP) in the presence of reverse micelles formed in CO2 with the surfactants ammonium carboxylate perfluoropolyether (PFPECOO-+NH4) (Mw = 587) and poly(dimethyl amino ethyl methacrylate-block-1H,1H,2H,2H-perfluorooctyl methacrylate) (PDMAEMA-b-PFOMA). Based on dynamic light scattering measurements, the amorphous TiO2 particles formed by injection of TTIP are larger than the reverse micelles, indicating surfactant reorganization. The size of the particles and the stability of dispersions in CO2 were affected by the molar ratio of water to surfactant headgroup (w(o)), precursor concentration, and injection rate. The amorphous particle size did not change upon depressurization and redispersion in CO2. PDMAEMA-b-PFOMA provided greater stability against particle aggregation at higher reactant concentration compared with PFPECOO-+NH4. The crystallite size after calcination, which was examined by X-ray diffraction and transmission electron microscopy, increased with w(o). PMID:15835711

  16. Structure of diglycerol monomyristate reverse micelles in styrene: a small-angle X-ray scattering (SAXS) study.

    Science.gov (United States)

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

    2011-08-01

    Structure of diglycerol monomyristate (designated as C14G2) nonionic surfactant reverse micelles in aromatic solvent styrene has been investigated as a function of surfactant concentration, temperature, and water addition by using small-angle X-ray scattering (SAXS) technique. Structure of micelles in real-space so called pair-distance distribution function, p(r), was obtained by the generalized indirect fourier transformation (GIFT) evaluation of SAXS data. It was found that C14G2 spontaneously self-assembles into spheroid reverse micelles with maximum diameter approximately 3.0 nm when added into styrene under ambient condition. The micellar shape and size remained essentially the same despite a wide variation in surfactant concentration (5 to 30%) but an opposite trend was observed with the rise of temperature; size decreased by approximately 25% with increase in temperature from 25 to 75 degrees C. Addition of traces water favored micellar growth and eventually ellipsoid prolate type micelles were formed, whose scenario is understood in terms of decrease in the critical packing parameter (cpp); water hydrates the surfactant's headgroup and decreases cpp. At a particular concentration of water, increasing temperature decreased the micellar size due to dehydration of headgroup. It is interesting to note that size of 1.57% water incorporated micelle is approximately 2.5 times bigger than the empty micelles. PMID:22103110

  17. Structure of a Unimolecular Dendritic Reverse Micelle in Dense CO2 Via Small Angle Scattering

    Science.gov (United States)

    Lin, J. S.

    1997-03-01

    Dilute solutions in dense CO2 (5Kpsi and 25 degC) of a unimolecular reverse micelle were studied via small angle x ray scattering (SAXS). The unimolecular micelle was based on a fourth generation poly(propylene imine) dendrimer, functionalized with perfluoropolyether acid fluoride chains. A value of 26 added chains per dendrimer was obtained from other characterization techniques, and this number of chains was fixed in the fitting of the SAXS data to an f-arm star model. The molecular weight ( 33.5K g mol-1) agreed well with estimates from other techniques. The observed negative second virial coefficient, A2 = -1.2 x 10-4 cm^3 g-2 mol, correlates with prior observations, as does the observed radius of gyration, Rg = 32ÅSponsors: Div. of Mat. Sci., Basic Energy Sc., USDOE, contract DE-AC05-96OR22464, Oak Ridge Nat. Lab., managed by Lockheed Martin Energy Research Corp.; The Royal Commission for the Exhibition of 1851; National Science Foundation; Consortium for the Sythesis and Processing of Polymeric Materials in Carbon Dioxide.

  18. Formation of the reverse micelles of cetyl trimethylammonium bromide in chloroform and their behavior at subzero temperatures

    Czech Academy of Sciences Publication Activity Database

    Klíčová, L.; Šebej, P.; Štacko, P.; Filippov, Sergey K.; Klán, P.

    Philadelphia : American Chemical Society, 2012. s.103-COLL 217. [American Chemical Society National Meeting /244./ & Exposition - Materials for Health & Medicine. 19.08.2012-23.08.2012, Philadelphia] R&D Projects: GA ČR GAP108/12/0640 Institutional support: RVO:61389013 Keywords : aggregation * reverse micelles Subject RIV: CD - Macromolecular Chemistry

  19. The synthesis of iron-nickel alloy nanoparticles using a reverse micelle technique

    International Nuclear Information System (INIS)

    Nanosized Fe0.2Ni0.8 particles were prepared by reducing their salts with sodium borohydride (NaBH4) in cationic water-in-oil (w/o) microemulsions of water/cetyl-trimethyl-amonium bromide (CTAB) and n-butanol/isooctane at 25 oC. According to the TEM and X-ray diffraction analyses, the synthesized particles were around 4-12 nm in size. Due to their nanodimensions, the particles had a primitive cubic (pc) structure rather than the body-centered cubic (BCC) structure of the bulk material. An examination of the synthesis from the reverse micelle reveals that the morphology of the iron-nickel alloy nanoparticles depends mainly on the microemulsion's composition. The magnetization of the nanoparticles was much lower than that of the bulk material, reflecting the influence of the nanodimensions on the particles' magnetizations

  20. Magnetic behavior of nanocrystalline nickel ferrite synthesized by the reverse micelle technique

    Science.gov (United States)

    Kale, A.; Gubbala, S.; Misra, R. D. K.

    2004-06-01

    Nanocrystalline nickel ferrite of crystallite size 5-8 nm, synthesized by the reverse micelle technique were characterized by high-resolution transmission electron microscopy and X-ray diffraction techniques, and the magnetic behavior studied by superconducting quantum interference device. Nanocrystalline nickel ferrite exhibit a blocking temperature of 16 K. They do not attain saturation magnetization even at a high field of 50 kOe. The lack of saturation in high field occurs in association with high field irreversibility and open loop at 50 kOe. The saturation magnetization at 300 K is 25.4 emu/g and at 2 K is 35.5 emu/g, which is significantly lower than that reported for the multidomain bulk nickel ferrite (55 emu/g). This is discussed in terms of a two-component nanoparticle system consisting of a spin glass-like surface layer of a few atomic layers thick and ferrimagnetically aligned core spins.

  1. Magnetic behavior of nanocrystalline nickel ferrite synthesized by the reverse micelle technique

    International Nuclear Information System (INIS)

    Nanocrystalline nickel ferrite of crystallite size 5-8 nm, synthesized by the reverse micelle technique were characterized by high-resolution transmission electron microscopy and X-ray diffraction techniques, and the magnetic behavior studied by superconducting quantum interference device. Nanocrystalline nickel ferrite exhibit a blocking temperature of 16 K. They do not attain saturation magnetization even at a high field of 50 kOe. The lack of saturation in high field occurs in association with high field irreversibility and open loop at 50 kOe. The saturation magnetization at 300 K is 25.4 emu/g and at 2 K is 35.5 emu/g, which is significantly lower than that reported for the multidomain bulk nickel ferrite (55 emu/g). This is discussed in terms of a two-component nanoparticle system consisting of a spin glass-like surface layer of a few atomic layers thick and ferrimagnetically aligned core spins

  2. The synthesis of iron nickel alloy nanoparticles using a reverse micelle technique

    Science.gov (United States)

    Ban, Irena; Drofenik, Miha; Makovec, Darko

    2006-12-01

    Nanosized Fe 0.2Ni 0.8 particles were prepared by reducing their salts with sodium borohydride (NaBH 4) in cationic water-in-oil (w/o) microemulsions of water/cetyl-trimethyl-amonium bromide (CTAB) and n-butanol/isooctane at 25 °C. According to the TEM and X-ray diffraction analyses, the synthesized particles were around 4-12 nm in size. Due to their nanodimensions, the particles had a primitive cubic (pc) structure rather than the body-centered cubic (BCC) structure of the bulk material. An examination of the synthesis from the reverse micelle reveals that the morphology of the iron-nickel alloy nanoparticles depends mainly on the microemulsion's composition. The magnetization of the nanoparticles was much lower than that of the bulk material, reflecting the influence of the nanodimensions on the particles' magnetizations.

  3. Removal of ionic dyes from water by solvent extraction using reverse micelles.

    Science.gov (United States)

    Pandit, P; Basu, S

    2004-04-15

    Several methods (e.g., UV/H2O2 oxidation, adsorption, flocculation-precipitation) are normally employed to remove dye from water. A new technique based on liquid/liquid extraction using reverse micelles is proposed whereby recovery of solvent and reuse of dye is possible. Experiments were conducted by mixing a known quantity of dye in aqueous phase and solvent-containing surfactants in a simple mixer. The separation of solvent phase, containing encapsulated dye in reverse micelles, from aqueous phase due to gravity results in separation of dye from water. The removal of different ionic dyes (e.g., eosin yellow, methylene blue, malachite green, methyl orange, orange G) from aqueous phase in the presence of different cationic and anionic surfactants [e.g., sodium dodecylbenzene sulfonate, sodium bis(2-ethylhexyl) sulfosuccinate, hexadecyltrimethylammonium bromide, and cetyl pyridinium chloride] in different solvents (e.g., amyl alcohol, benzyl alcohol, methyl benzoate, and isooctane) were studied by conducting experiments. The percentage removal of dye from aqueous phase increases with the decrease in dye concentration or with the increase in surfactants concentration. Furthermore, the percentage COD removal of dye is increased with the increase in surfactant concentration. The nature of solvent has minimal effect on percentage removal of dye. The ratio of solventto aqueous phase volume required for the removal of dye decreases with the increase in surfactant concentration. It is possible to back-extract dye into aqueous phase and recover solvent by using counterionic surfactants. The separation of aqueous phase from the aqueous-phase solvent dispersion is faster for amyl alcohol as compared to benzyl alcohol and methyl benzoate. A theoretical model based on ion-exchange reaction between surfactants and dye is used to analyze the experimental data. PMID:15116851

  4. Reverse micelle-based microencapsulation of oxytetracycline hydrochloride into poly-d,l-lactide-co-glycolide microspheres.

    Science.gov (United States)

    Kim, Hyunjoo; Lee, Beom-Jin; Sah, Hongkee

    2007-02-01

    The objectives of this study were to solubilize oxytetracycline hydrochloride (HCl) in reverse micelles to prepare poly-d,l-lactide-co-glycolide (PLGA) microspheres and to explore parameters affecting its encapsulation efficiency. Oxytetracycline HCl was dissolved in the reverse micelles consisting of cetyltrimethylammonium bromide, water, and ethyl formate. A PLGA polymer was then dissolved in the reverse micellar solution, and a modified solvent quenching procedure was carried out to prepare PLGA microspheres. Encapsulation efficiencies of oxytetracycline HCl ranged from 2.3 +/- 0.2 to 24.9 +/- 4.6%, depending on experimental conditions. Important parameters affecting its encapsulation efficiency included the amounts of water used to prepare the reverse micelles and PLGA polymer. With regard to microsphere morphology, the reverse micellar process produced the microspheres with smooth and pore-free surfaces. In particular, their internal matrices did not possess hollow cavities that were frequently observed when a typical double emulsion technique was used to make microspheres. In summary, it was possible to encapsulate oxytetracycline HCl into PLGA microspheres via the ethyl formate-based reverse micellar technique. We also anticipate that the use of ethyl formate could avoid environmental and human toxicity issues associated with methylene chloride. PMID:17364873

  5. Magnetoresistance of a (γ-Fe2O3)80Ag20 nanocomposite prepared in reverse micelles

    Science.gov (United States)

    Wiemann, Joan A.; Carpenter, Everett E.; Wiggins, Jason; Zhou, Weilie; Tang, Jinke; Li, Sichu; John, Vijay T.; Long, Gary J.; Mohan, Amitabh

    2000-05-01

    The magnetic and transport properties of a (γ-Fe2O3)80Ag20 nanocomposite, prepared by a reverse micelle technique, have been studied. γ-Fe2O3 nanoparticles and Ag particles were individually synthesized in reverse micelles. The nanocomposite material was then prepared by mixing the two different particles in a γ-Fe2O3/Ag molar ratio 80/20. The morphology of the nanoparticles was examined with transmission electron microscopy. Mössbauer spectra revealed no obvious presence of any divalent iron. Zero field cooled and field cooled magnetic susceptibilities indicated a blocking temperature of about 40 K. Negative magnetoresistance was observed resembling that in ball milled γ-Fe2O3/Ag nanocomposites. However, the magnitude of the negative magnetoresistance is smaller and is ˜2.2% at 220 K and 9 T. Two possible mechanisms, spin-dependent hopping and tunneling across magnetic barriers, are discussed.

  6. Control of the morphology and optical properties of ZnO nanostructures via hot mixing of reverse micelles.

    Science.gov (United States)

    Mao, Jing; Li, Xiao-Lei; Qin, Wen-Jing; Niu, Kai-Yang; Yang, Jing; Ling, Tao; Du, Xi-Wen

    2010-09-01

    ZnO nanostructures with controllable morphology were obtained by hot mixing reverse micelles containing Zn(NO(3))(2) or monoethanol amine aqueous solution. The ratio of water to surfactant concentration (omega(0)) was found to play a decisive role in determining the final morphology, namely, nanotetrahedrons formed at a lower omega(0) value and nanorods formed at a higher value. However, the hot mixing technique is propitious for obtaining nanostructures with uniform size. The ZnO nanotetrahedrons obtained gave a strong blue emission arising from interface state, and the ZnO nanorods emitted green light related to donor defects. Our results indicate that the hot mixing of reverse micelles is a unique way to tune the morphology and properties of nanostructures. PMID:20666465

  7. Investigation of laundering and dispersion approaches for silica and calcium phosphosilicate composite nanoparticles synthesized in reverse micelles

    Science.gov (United States)

    Tabakovic, Amra

    Nanotechnology, the science and engineering of materials at the nanoscale, is a booming research area with numerous applications in electronic, cosmetic, automotive and sporting goods industries, as well as in biomedicine. Composite nanoparticles (NPs) are of special interest since the use of two or more materials in NP design imparts multifunctionality on the final NP constructs. This is especially relevant for applications in areas of human healthcare, where the use of dye or drug doped composite NPs is expected to improve the diagnosis and treatment of cancer and other serious illnesses. Since the physicochemical properties of NP suspensions dictate the success of these systems in biomedical applications, especially drug delivery of chemotherapeutics, synthetic routes which offer precise control of NP properties, especially particle diameter and colloidal stability, are utilized to form a variety of composite NPs. Formation of NPs in reverse, or water-in-oil, micelles is one such synthetic approach. However, while the use of reverse micelles to form composite NPs offers precise control over NP size and shape, the post-synthesis laundering and dispersion of synthesized NP suspensions can still be a challenge. Reverse micelle synthetic approaches require the use of surfactants and low dielectric constant solvents, like hexane and cyclohexane, as the oil phase, which can compromise the biocompatibility and colloidal stability of the final composite NP suspensions. Therefore, appropriate dispersants and solvents must be used during laundering and dispersion to remove surfactant and ensure stability of synthesized NPs. In the work presented in this dissertation, two laundering and dispersion approaches, including packed column high performance liquid chromatography (HPLC) and centrifugation (sedimentation and redispersion), are investigated for silver core silica (Ag-SiO2) and calcium phosphosilicate (Caw(HxPO4)y(Si(OH)zOa) b · cH2O, CPS) composite NP suspensions

  8. Reverse-Micelle Synthesis of Electrochemically Encoded Quantum Dot Barcodes: Application to Electronic Coding of a Cancer Marker

    OpenAIRE

    Xiang, Yun; Zhang, Yuyong; Chang, Yue; Chai, Yaqin; Wang, Joseph; Yuan, Ruo

    2010-01-01

    Reproducible electrochemically encoded quantum dot (QD) barcodes were prepared by using the reverse-micelle synthetic approach. The encoding elements, Zn2+, Cd2+, Pb2+ were confined within a single QD, which eliminates the cumbersome encapsulation process used by other common nanoparticle-based barcode preparation schemes. The distinct voltammetric stripping patterns of Zn2+, Cd2+, Pb2+ at distinguishable potentials with controllable current intensities offer excellent encoding capability for...

  9. Effect of different reversed micelles on autooxidation and photooxidation of stripped corn oil

    Directory of Open Access Journals (Sweden)

    Schwarz, K.

    2003-03-01

    Full Text Available The effect of reversed micelles (RMs in combination with α -tocopherol and Trolox was evaluated on the autooxidation and photooxidation of stripped corn oil. Oxidation was followed by measuring hydroperoxide and hexanal formation. RMs affected the oil oxidation stability to a degree depending on the surfactant used. Lecithin RMs caused a stronger decrease in oxidation than polyglyceryl-3-oleate RMs and methylglucose dioleate RMs. All RMs reduced the inhibition of oxidation when added in combination with external antioxidant.El efecto de miscelas inversas (RMs en combinación con α-tocoferol y Trolox fue evaluado en la autooxidación y fotooxidación de aceite de maíz libre de antioxidantes. La oxidación fue seguida por la medida de la formación de hexanal e hidroperóxido. Las RMs influyeron en la estabilidad de la oxidación del aceite dependiendo del tensioactivo usado. Las RMs de lecitina causaron una mayor disminución en la oxidación que las RMs de poligliceril-3-oleato y las RMs de metilglucosa dioleato. Todas las RMs redujeron la inhibición de la oxidación cuando se añadieron en combinación con antioxidantes externos.

  10. A predictive model of reverse micelles solubilizing water for solvent extraction.

    Science.gov (United States)

    Bley, Michael; Siboulet, Bertrand; Karmakar, Anwesa; Zemb, Thomas; Dufrêche, Jean-François

    2016-10-01

    Herein, a minimal model for the common case of W/O solubilization of badly soluble compounds present in an excess phase by reverse micellar aggregates in chemical equilibrium with its single compounds is introduced. A simple model of such liquid-liquid extractions is crucial for obtaining predictive parameter for the modelling of nuclear waste management and hydrometallurgic recycling strategies. The standard Gibbs free energy of aggregation and the concentration of the corresponding aggregate is calculated within a multiple-equilibria approach for a set of aggregate compositions of solute and amphiphilic extractant molecules. This minimal model provides potential surfaces estimating the stability of different aggregate compositions with 6.2kJmol(-1) as a generalized bending constant. The complete concentrations of free and aggregated extractant species as well as the favored aggregation numbers, the polydispersity, the activity of the organic solvent, and the critical concentrations are captured by this thermodynamic model. An increase of the apparent critical micelle concentration for an increasing solute content in the aqueous phase is detected by this method. PMID:27376975

  11. Structural and magnetic properties of nano nickel zinc ferrite synthesized by reverse micelle technique

    Science.gov (United States)

    Thakur, Sangeeta; Katyal, S. C.; Singh, M.

    2009-01-01

    Nanocrystalline nickel-zinc ferrites (Ni 0.58Zn 0.42Fe 2O 4) at different pH values (less than 9.6, 9.6, 10.96, and 11.40) for the alkali-precipitating reaction were synthesized by reverse micelle technique. X-ray diffraction reveals a well-defined nickel-zinc ferrite crystal phase at pH=9.6. Increase in pH value obstructs pure-phase formation and results in partial formation of α-Fe 2O 3. The magnetic behaviour of the samples was studied by superconducting quantum interference device. All the samples show superparamagnetic behaviour at room temperature (300 K) and negligible hysteresis at low temperature (5 K). The low value of saturation magnetization is explained on the basis of spin canting. The high-field irreversibility and shifting of the hysteresis loop detected in single-phase sample has been assigned to a spin-disordered phase, which has a spin-freezing temperature of approximately 42 K and other two samples have an antiferromagnetic phase (α-Fe 2O 3) coupled to the ferromagnetic phase.

  12. SAXS and SANS studies of surfactants and reverse micelles in supercritical CO2

    International Nuclear Information System (INIS)

    Surfactants promise to extend the applicability of supercritical CO2 (SC-CO2) to processing of insoluble materials such as polymers and aqueous systems. In this short paper the authors summarize the techniques for studying surfactants and reverse micelles in SC-CO2 using SAXS and SANS; they will describe the scattering instruments and the pressure cells for conducting these studies; they will describe the types of measurement that yield the desired characterizations; they will describe the methods of data analysis and interpretation; and they will provide illustrative results from this laboratory. Industry seeks to replace common organic solvents now used in many reaction and separation processes; SC-CO2 is a potential solvent substitute widely favored by both government and industry. The currently available surfactants are limited in number and performance. In ongoing work the authors are coupling their SAXS and SANS scattering studies with complementary molecular simulations in efforts to understand, at a molecular level, what surfactant characteristics lead to improved performance. They hope that superior surfactants for use in SC-CO2 can be designed and synthesized based on this new level of understanding

  13. Structural and magnetic properties of nano nickel-zinc ferrite synthesized by reverse micelle technique

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Sangeeta [Jaypee University of Information Technology, Waknaghat, District Solan 173215 (India)], E-mail: megha2k5@rediffmail.com; Katyal, S.C. [Jaypee University of Information Technology, Waknaghat, District Solan 173215 (India); Singh, M. [Department of Physics, Himachal Pradesh University, Shimla 171005 (India)

    2009-01-15

    Nanocrystalline nickel-zinc ferrites (Ni{sub 0.58}Zn{sub 0.42}Fe{sub 2}O{sub 4}) at different pH values (less than 9.6, 9.6, 10.96, and 11.40) for the alkali-precipitating reaction were synthesized by reverse micelle technique. X-ray diffraction reveals a well-defined nickel-zinc ferrite crystal phase at pH=9.6. Increase in pH value obstructs pure-phase formation and results in partial formation of {alpha}-Fe{sub 2}O{sub 3}. The magnetic behaviour of the samples was studied by superconducting quantum interference device. All the samples show superparamagnetic behaviour at room temperature (300 K) and negligible hysteresis at low temperature (5 K). The low value of saturation magnetization is explained on the basis of spin canting. The high-field irreversibility and shifting of the hysteresis loop detected in single-phase sample has been assigned to a spin-disordered phase, which has a spin-freezing temperature of approximately 42 K and other two samples have an antiferromagnetic phase ({alpha}-Fe{sub 2}O{sub 3}) coupled to the ferromagnetic phase.

  14. Structural and magnetic properties of nano nickel-zinc ferrite synthesized by reverse micelle technique

    International Nuclear Information System (INIS)

    Nanocrystalline nickel-zinc ferrites (Ni0.58Zn0.42Fe2O4) at different pH values (less than 9.6, 9.6, 10.96, and 11.40) for the alkali-precipitating reaction were synthesized by reverse micelle technique. X-ray diffraction reveals a well-defined nickel-zinc ferrite crystal phase at pH=9.6. Increase in pH value obstructs pure-phase formation and results in partial formation of α-Fe2O3. The magnetic behaviour of the samples was studied by superconducting quantum interference device. All the samples show superparamagnetic behaviour at room temperature (300 K) and negligible hysteresis at low temperature (5 K). The low value of saturation magnetization is explained on the basis of spin canting. The high-field irreversibility and shifting of the hysteresis loop detected in single-phase sample has been assigned to a spin-disordered phase, which has a spin-freezing temperature of approximately 42 K and other two samples have an antiferromagnetic phase (α-Fe2O3) coupled to the ferromagnetic phase

  15. Luminescence decay kinetics of Mn2+-doped ZnS nanoclusters grown in reverse micelles

    International Nuclear Information System (INIS)

    We report the synthesis and luminescence decay kinetics of 1.2-nm Mn2+-doped ZnS nanoclusters grown in reverse micelles. The preparation method produces small particles with narrow-size distribution and fluorescence bands near 400-450 nm and 585 nm. Time-dependent fluorescence decay measurements using picosecond, nanosecond, and millisecond techniques reveal relaxation processes on all three time scales. In the doped sample, the red emission detected at 600 nm exhibits a 1-2 ms decay in addition to faster decays with time constants on the order of hundreds of ps, a few ns and tens of μs. While the slow decay is the same as that of bulk Mn2+-doped ZnS, the fast decays are present for both doped and undoped samples and are unique to nanocluster ZnS, which are attributed to deep trap-state emission. The blue luminescence near 400-450 nm is attributed to shallow trap-state emission of ZnS. These results help to resolve the controversy in the literature regarding the lifetime of the Mn2+ emission in Mn-doped ZnS nanoparticles. (c) 2000 The American Physical Society

  16. Use of perturbed angular correlation technique for studies of equilibrium systems: Cd-ions in water-pools of reversed micelles

    International Nuclear Information System (INIS)

    Possibilities and limitations of the perturbed angular correlation technique were investigated in a study of water-pools of reversed micelles of sodium-diethylhexylsulphosuccinate in iso-octane. Probe nuclide for the measurements was reactor produced 111mCd in the form of Cd2+-ions. The results indicate that Cd2+-ions are present inside the water-pool and predominantly experience the movements of the surrounding H2O molecules. An increase in the average number of Cd2+-ions per micelle seemed to have consequences for the size of the pools and, consequently, of the reversed micelles. (author)

  17. Reverse Micelle Synthesis and Characterization of Supported Pt/Ni Bimetallic Catalysts on gamma-Al2O3

    Energy Technology Data Exchange (ETDEWEB)

    B Cheney; J Lauterbach; J Chen

    2011-12-31

    Reverse micelle synthesis was used to improve the nanoparticle size uniformity of bimetallic Pt/Ni nanoparticles supported on {gamma}-Al{sub 2}O{sub 3}. Two impregnation methods were investigated to optimize the use of the micelle method: (1) step-impregnation, where Ni nanoparticles were chemically reduced in microemulsion and then supported, followed by Pt deposition using incipient wetness impregnation, and (2) co-impregnation, where Ni and Pt were chemically reduced simultaneously in microemulsion and then supported. Transmission electron microscopy (TEM) was used to characterize the particle size distribution. Atomic absorption spectroscopy (AAS) was used to perform elemental analysis of bimetallic catalysts. Extended X-ray absorption fine structure (EXAFS) measurements were utilized to confirm the formation of the Pt-Ni bimetallic bond in the step-impregnated catalyst. CO pulse chemisorption and Fourier transform infrared spectroscopy (FTIR) studies of 1,3-butadiene hydrogenation in a batch reactor were performed to determine the catalytic activity. Step-impregnated Pt/Ni catalyst demonstrated enhanced hydrogenation activity over the parent monometallic Pt and Ni catalysts due to bimetallic bond formation. The catalyst synthesized using co-impregnation showed no enhanced activity, behaving similarly to monometallic Ni. Overall, our results indicate that reverse micelle synthesis combined with incipient wetness impregnation produced small, uniform nanoparticles with bimetallic bonds that enhanced hydrogenation activity.

  18. Preparation and characterization of supported magnetic nanoparticles prepared by reverse micelles

    Directory of Open Access Journals (Sweden)

    Ulf Wiedwald

    2010-11-01

    Full Text Available Monatomic (Fe, Co and bimetallic (FePt and CoPt nanoparticles were prepared by exploiting the self-organization of precursor loaded reverse micelles. Achievements and limitations of the preparation approach are critically discussed. We show that self-assembled metallic nanoparticles can be prepared with diameters d = 2–12 nm and interparticle distances D = 20–140 nm on various substrates. Structural, electronic and magnetic properties of the particle arrays were characterized by several techniques to give a comprehensive view of the high quality of the method. For Co nanoparticles, it is demonstrated that magnetostatic interactions can be neglected for distances which are at least 6 times larger than the particle diameter. Focus is placed on FePt alloy nanoparticles which show a huge magnetic anisotropy in the L10 phase, however, this is still less by a factor of 3–4 when compared to the anisotropy of the bulk counterpart. A similar observation was also found for CoPt nanoparticles (NPs. These results are related to imperfect crystal structures as revealed by HRTEM as well as to compositional distributions of the prepared particles. Interestingly, the results demonstrate that the averaged effective magnetic anisotropy of FePt nanoparticles does not strongly depend on size. Consequently, magnetization stability should scale linearly with the volume of the NPs and give rise to a critical value for stability at ambient temperature. Indeed, for diameters above 6 nm such stability is observed for the current FePt and CoPt NPs. Finally, the long-term conservation of nanoparticles by Au photoseeding is presented.

  19. Study of the micelle formation and the effect of additives on this process in reversed micellar systems by positron annihilation techniques

    International Nuclear Information System (INIS)

    The positron annihilation technique was applied to the study of the micelle formation process in reversed micellar systems, Aerosol OT and dodecylammonium propionate in apolar solvents, such as benzene, isooctane, and cyclohexane. The results indicate that the positronium formation probability responds very sensitively to microphase changes in reversed micellar solutions. The abrupt changes in positronium formation probability observed at certain surfactant concentrations appear to coincide with variations in the aggregation state of the surfactant molecules in solutions, as postulated by the modified pseudophase model which considers the possibility of conformational changes between premicellar aggregates, and the surfactant concentrations at which they occur may be interpreted as operational critical micelle concentrations. Additives or probe molecules can affect these changes and shift them to lower surfactant concentrations. The additions of H2O and its solubilization in form of clusters inside the reverse micelle leads to microphase changes also detectable by the positron annihilation technique. From a comparison of the rate constants between positronium and probe molecules observed in the neat solvents and in the corresponding micellar solutions, it was concluded that the probe molecules are attracted to various degrees by the reverse micelles, the nature of the surfactant and solvent determining the relative distribution of the probe molecule in the outer hydrocarbon layer and in the bulk apolar solvent of the reversed micelles

  20. Reverse micelle mediated synthesis, processing, mechanical and biological characterization of hydroxyapatite nanopowders for bone graft application

    Science.gov (United States)

    Banerjee, Ashis

    Hydroxyapatite (HA) is the most widely used bioceramic material in bone graft applications because of its compositional similarity with natural bone. However, synthetic HA does not show similar mechanical and biological properties to the inorganic component of bone. Properties of ceramic material depend on starting materials, processing techniques, densification and microstructure of the final product. The objective of this research was to process HA whisker reinforced HA composite using HA nanopowders and whiskers. HA nanopowders with different length scale and morphology were synthesized by reverse micelle system using NP5 and NP12 as surfactants and cyclohexane as organic solvent. The lowest average aspect ratio was 1.357+/-0.39 with average particle size of 66 nm and the highest average aspect ratio was 7.277+/-3.227 with average length of 150 nm and width of 20 nm, were synthesized. Micron sized HA whiskers with aspect ratio between 20 and 50, average particle length of 15 mum and width of 400 nm was synthesized using urea as a precipitating agent. Desired microstructure was obtained after sintering with spherical HA nanopowder and whiskers along with dopants. Addition of whiskers decreased density of the sintered compacts. However, at 10 wt% whisker content sample showed microhardness and fracture toughness of 3.6 GPa and 1.5 MPa.m1/2, respectively, and a compressive strength of 80 MPa was obtained. Mineralization study in simulated body fluid (SBF) showed formation of apatite layer on the dense HA compacts indicating a good tendency of bond formation with natural bone. Cytotoxicity results showed excellent cell attachment on the HA surface. In the Appendices, 3 journal articles have been attached which describe synthesis, processing and characterization of undoped and doped PZT nanopowders. Free standing and agglomerated PZT nanopowders were synthesized by the sucrose templated method and the citrate nitrate autocombustion method. Particle size in the range

  1. Evolution, dissolution and reversible generation of gold and silver nanoclusters in micelle by UV-activation

    Indian Academy of Sciences (India)

    Sujit Kumar Ghosh; Subrata Kundu; Tarasankar Pal

    2002-11-01

    Gold and silver nanoparticles were produced separately by UV photoactivation (with variable flux density) in the presence of nonionic micelle, TX-100. Even their cyano complexes break down in TX-100 under UV and hence dissolution and reevolution of almost monodispersed nanoparticles (∼ 3 nm) are possible.

  2. Supramolecular-based dispersive liquid-liquid microextraction: a novel sample preparation technique utilizes coacervates and reverse micelles.

    Science.gov (United States)

    Jafarvand, Sanaz; Shemirani, Farzaneh

    2011-02-01

    The present study reports a novel sample enrichment method termed supramolecular-based dispersive liquid-liquid microextraction (SM-DLLME). The SM solvent selected was made up of reversed micelles of decanoic acid dispersed in tetrahydrofuran (THF)-water. THF plays double role, not only acts as a disperser solvent but also causes self-assembly of decanoic acid. The contaminant used as a model was Malachite Green (MG). It was a cationic dye and was preconcentrated without any derivatization or ion-pair formation reaction. In SM-DLLME, the most important advantages of DLLME technique and preconcentration strategy based on the coacervation and reverse micelles have come together. Moreover, in this method, disadvantages of DLLME such as extraction capability of only hydrophobic analytes and hiring toxic and hazardous organic solvents as the extraction solvent and disadvantages of coacervation-based extraction method such as tedious, labor-intensive and time-consuming stirring procedure have been avoided. Several variables affecting the microextraction efficiency were investigated and optimized. Under the optimized conditions and preconcentration of only 5.00 mL of sample, the enhancement factor was 52, limit of detection (LOD) was 4 μg/L and relative standard deviations (RSDs) for 145 and 36 μg/L of MG in textile industry wastewater were 1.8 and 3.2%, respectively (n = 6). PMID:21254398

  3. New development of reverse micelles and applications in protein separation and refolding%反胶团系统及其在蛋白质分离复性中的应用研究进展

    Institute of Scientific and Technical Information of China (English)

    刘杨; 董晓燕; 孙彦

    2008-01-01

    Reverse micelles bring mild and effective microenvironments in organic solvent that contain bio-molecules, which have attracted immense attention for application in the isolation of proteins, protein refolding, and enzymatic reaction. In this review, the application of reverse micelles for protein separation and refolding has been briefly summarized and various reverse micellar systems composed of different surfactants, including ionic, non-ionic, mixed, and affinity-based reverse micelles, have been highlighted. It illustrates especially the potential application of the novel affinity-based reverse micelles consisting of biocompatible surfactant coupled with affinity ligands. Moreover, the importance to develop universal affinity-based reverse micelles for protein separation and refolding in the downstream processing of biotechnology has been pointed out.

  4. A kinetic model for the competitive reactions of ozone with amino acid residues in proteins in reverse micelles

    Energy Technology Data Exchange (ETDEWEB)

    Pryor, W.A.; Uppu, R.M. (Louisiana State Univ., Baton Rouge (United States))

    1993-02-15

    Lysozyme and 10 other proteins are solubilized in reverse micelles formed by 0.1 M sodium di-2-ethyl-hexylsulfosuccinate and 2.0-2.5 M water (pH 7.4) in isooctane solvent. Exposure of the protein-containing reverse micellar solutions to ozone causes oxidative damage to the proteins, as assessed by the oxidation of tryptophan residues. The oxidation product of the protein-bound tryptophan has a molar absorption coefficient of 3275 +/- 81 M-1 cm-1 (mean +/- S.D., n = 6) at 320 nm. The product is suggested to be a Criegee ozonide or a tautomer of the Criegee ozonide and not N-formylkynurenine. Ozonation of lysozyme in reverse micelles results in the formation of hydrogen peroxide in yields of only approximately 0.07 mol/mol of tryptophan residues oxidized. The recovery of hydrogen peroxide added as an internal standard to the lysozyme-containing reverse micellar solutions ranges from 84 to 88%, whether or not the samples are subjected to ozonation. This suggests that hydrogen peroxide is neither destroyed during the process of ozonation nor consumed by the protein to a significant extent in an adventitious reaction. A kinetic model for the overall reaction of ozone with the proteins is developed, taking into account the concentrations and the reactivities of individual amino acid residues toward ozone. The model predicts the fractional reaction of ozone with tryptophan residues in the proteins, despite differences in amino acid composition, molecular weight, and tertiary structures. The lack of influence of protein structure is confirmed further by the observation that the native lysozyme (with and without external S-carboxymethylcysteine) and S-carboxymethylated lysozyme give identical values of the fractional reaction of ozone with tryptophan residues. The kinetic equations for the competitive reactions of ozone with amino acid residues in proteins, with some minor modification, are applicable to ozonations on complex mixtures of lipids, proteins, and antioxidants.

  5. Nanoparticles synthesis of tungsten disulfide via AOT-based microemulsions

    Energy Technology Data Exchange (ETDEWEB)

    Ghoreishi, S.M., E-mail: ghoreshi@cc.iut.ac.ir [Department of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Meshkat, S.S. [Department of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Department of Chemical Engineering, Urmia University of Technology, Urmia 57155-419 (Iran, Islamic Republic of); Ghiaci, M. [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Dadkhah, A.A. [Department of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2012-06-15

    Graphical abstract: A controlled synthesis of WS2 nanoparticles (most probably inorganic fullerene (IF)) via microemulsion was applied for the first time to prepare WS2 (7–12 nm) by acidification of the water cores of the AOT reverse microemulsion. Highlights: ► An innovative reverse microemulsion technique was developed for WS{sub 2} synthesis. ► WS{sub 2} nanoparticles were obtained with narrow size distribution in range of 7–12 nm. ► Operating cost of microemulsion was lower in contrast to quartz reactor method. ► WS{sub 2} morphology could be controlled to obtain highly active and selective catalysts. ► Lower size of WS{sub 2} in this study overcomes the shortcoming of quartz reactor method. -- Abstract: The tungsten disulfide (WS{sub 2}) nanoparticles (most probably inorganic fullerene (IF)) with a narrow size distribution were synthesized by a reverse micelle technique for the first time. The particle size was controlled by varying water-to-surfactant molar ratio (W{sub 0}), aging time and reagent concentration. The synthesized WS{sub 2} nanoparticles were characterized by zetasizer, UV–visible spectrophotometers and transmission electron microscopy (TEM). The WS{sub 2} nanoparticles with particle diameter size of 7–12 nm were obtained via 24 h aging time. The particle size was controlled by changing the aging time and molar ratio of water/surfactant. Doubling W{sub 0} increased the amount and particle size of WS{sub 2} by 22 and 26%, respectively. The effect of aging time in the range of 6–24 h was investigated and the complete disappearance of yellowish color at 24 h resulted in an optically clear solution, which was the indication of WS{sub 2} formation with 100% conversion of reactant ((NH{sub 4}){sub 2}WS{sub 4}) in the batch reactor.

  6. Nanoparticles synthesis of tungsten disulfide via AOT-based microemulsions

    International Nuclear Information System (INIS)

    Graphical abstract: A controlled synthesis of WS2 nanoparticles (most probably inorganic fullerene (IF)) via microemulsion was applied for the first time to prepare WS2 (7–12 nm) by acidification of the water cores of the AOT reverse microemulsion. Highlights: ► An innovative reverse microemulsion technique was developed for WS2 synthesis. ► WS2 nanoparticles were obtained with narrow size distribution in range of 7–12 nm. ► Operating cost of microemulsion was lower in contrast to quartz reactor method. ► WS2 morphology could be controlled to obtain highly active and selective catalysts. ► Lower size of WS2 in this study overcomes the shortcoming of quartz reactor method. -- Abstract: The tungsten disulfide (WS2) nanoparticles (most probably inorganic fullerene (IF)) with a narrow size distribution were synthesized by a reverse micelle technique for the first time. The particle size was controlled by varying water-to-surfactant molar ratio (W0), aging time and reagent concentration. The synthesized WS2 nanoparticles were characterized by zetasizer, UV–visible spectrophotometers and transmission electron microscopy (TEM). The WS2 nanoparticles with particle diameter size of 7–12 nm were obtained via 24 h aging time. The particle size was controlled by changing the aging time and molar ratio of water/surfactant. Doubling W0 increased the amount and particle size of WS2 by 22 and 26%, respectively. The effect of aging time in the range of 6–24 h was investigated and the complete disappearance of yellowish color at 24 h resulted in an optically clear solution, which was the indication of WS2 formation with 100% conversion of reactant ((NH4)2WS4) in the batch reactor.

  7. Determination of critical micelle concentrations in micellar and reversed micellar systems by positron annihilation techniques

    International Nuclear Information System (INIS)

    The applicability of the positron annihilation technique is discussed as a simple method for the accurate determination of the critical micelle concentration (cmc). The results of a preliminary study of positron interactions in solutions with various amounts of surfactants present are reported. The six different micellar systems studied were dodecylammonium propionate in benzene, cyclohexane, and n-hexane; sodium di(2-ethylhexyl)sulfosuccinate in benzene; sodium decylsulfate and decyltrimethylammonium bromide in water. The tabulated results indicated that this technique was applicable to the determination of cmc's in both aqueous and nonaqueous solutions

  8. Synthesis and characterization of polyaniline nanorods/Ce(OH)3-Pr2O3/montmorillonite composites through reverse micelle template

    International Nuclear Information System (INIS)

    Polyaniline (PANI) nanorods/Ce(OH)3-Pr2O3/montmorillonite (MMT) nanocomposites were synthesized via in situ polymerization of aniline monomer through reverse micelle template (RMT) in the presence of montmorillonite and Ce(OH)3, Pr2O3. In the experiment, sulphosalicylic acid was used as dopant, aniline was designated as oil phase and the aqueous solution comprising Ce3+ and Pr3+ as water phase. The nanocomposites were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopy and thermogravimetry-differential thermal analysis (TG-DTA). The results showed that PANI nanorods were synthesized in the interlayer spaces of MMT with uniform spherical rare earth nanoparticles. The thermal stability of the nanocomposites prepared was enhanced drastically compared with pure polyaniline

  9. Generation of fluorescent silver nanoclusters in reverse micelles using gamma irradiation: low vs. high dosages and spectral evolution with time

    Science.gov (United States)

    Martin, Brett D.; Fontana, Jake; Wang, Zheng; Trammell, Scott A.

    2015-04-01

    Reverse micelles (RMs) containing aqueous solutions of Ag+ ions in their core produce fluorescent Ag nanoclusters (NCs), upon exposure to gamma irradiation. The fluorescence spectra of the NCs evolve over days to weeks after the exposure, and usually show large increases in intensity. Responses of as high as 2.8 × 104 CPS/Gy were reached. A dosage as low as 0.5 Gy (10 % of the lethal dosage for humans) produces NCs having fluorescence intensities higher than background. The RMs can be employed in novel gamma radiation detectors with appearance of fluorescence indicating that radiation was once present. In applications involving detection and tracking of fissile materials, the evolution of the fluorescence spectra over time may provide additional information about the radiation source. A two-phase liquid system is used for RM formation in a simple procedure. It is likely that this synthesis method may be adapted to produce NCs from other metal ions.

  10. A route for producing nano-CaRuO3 perovskite by combusting precursors prepared using reverse micelle synthesis

    International Nuclear Information System (INIS)

    Nanoparticles of Ca-Ru-O precursors have been prepared using a reverse micelle. Transmission electron microscopy and x-ray diffraction techniques showed that the precursors had an amorphous structure. The average diameter of the amorphous Ca-Ru-O particles was shown to be approximately 10 nm (within a range of ± 2 nm). An interesting result was that a rod-like nano-CaRuO3 perovskite was observed when the precursor was sintered at a temperature of 950 deg. C. Furthermore, the conversion of the powders to crystalline CaRuO3 perovskite occurred upon heat treatment at 450 deg. C in air. This is much lower than that for a standard solid-state reaction for CaCO3 and RuO2.

  11. A route for producing nano-CaRuO3 perovskite by combusting precursors prepared using reverse micelle synthesis

    Science.gov (United States)

    Jiao, Shuqiang; Tripuraneni Kilby, Kamal; Zhang, Lijuan; Fray, Derek J.

    2009-02-01

    Nanoparticles of Ca-Ru-O precursors have been prepared using a reverse micelle. Transmission electron microscopy and x-ray diffraction techniques showed that the precursors had an amorphous structure. The average diameter of the amorphous Ca-Ru-O particles was shown to be approximately 10 nm (within a range of ± 2 nm). An interesting result was that a rod-like nano-CaRuO3 perovskite was observed when the precursor was sintered at a temperature of 950 °C. Furthermore, the conversion of the powders to crystalline CaRuO3 perovskite occurred upon heat treatment at 450 °C in air. This is much lower than that for a standard solid-state reaction for CaCO3 and RuO2.

  12. A comparison of the magnetic characteristics of nanocrystalline nickel, zinc, and manganese ferrites synthesized by reverse micelle technique

    International Nuclear Information System (INIS)

    Nanocrystalline nickel, zinc and manganese ferrites synthesized by reverse micelle synthesis technique were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction techniques, and the magnetic behavior studied by Superconducting Quantum Interference Device (SQUID). The three ferrites exhibit blocking temperatures of 16, 20, and 35 K, respectively. The difference in the blocking temperatures was attributed to the magnetocrystalline anisotropy and L-S coupling. The saturation magnetization of the three ferrites at 300 K was 25, 8, and 6 emu/g, respectively and at 2 K was 35, 17, and 15 K, respectively. The lower saturation magnetization in the case of nickel and manganese ferrite compared to their bulk counterparts is attributed to a core-shell like particle morphology. The increase in the saturation magnetization in the case of zinc ferrite nanoparticles is attributed to the change in the cation distribution from a normal spinel to a mixed spinel structure in the nanocrystalline form

  13. Synthesis and characterization of metallic Pd embedded TiO2 nanoparticles by reverse micelle and sol-gel processing

    Institute of Scientific and Technical Information of China (English)

    Jeoung-Ho JIN; Min-Cheol CHU; Seong-Jai CHO; Dong-Sik BAE

    2009-01-01

    Metallic Pd clusters were embedded into TiO2 nanoparticles that were synthesized within reverse micelle via a solution reduction of Pd(NO3)2 by hydrazine hydrate. The size of the particles can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of titanium tetra-isopropoxide within the micro-emulsion. The spherical equivalent size for the Pd clusters formed in TiO2 matrix was estimated to be around (3±1) nm. The presence of Pd in the matrix was demonstrated by EDS spectroscopy. The effects of synthesis parameters, such as the concentration of Pd solution, the molar ratio of water to TIP, and the molar ratio of water to surfactant, were discussed.%This research was financially supported by the Ministry of Education, Science Technology(MEST) and Korea Industrial Technology Foundation(KOTEF) through the Human Resource Training Project for Regional Innovation.

  14. Core-Shell Nanocatalysts Obtained in Reverse Micelles: Structural and Kinetic Aspects

    Directory of Open Access Journals (Sweden)

    Concha Tojo

    2015-01-01

    Full Text Available Ability to control the metal arrangement in bimetallic nanocatalysts is the key to improving their catalytic activity. To investigate how metal distribution in nanostructures can be modified, we developed a computer simulation model on the synthesis of bimetallic nanoparticles obtained in microemulsions by a one-pot method. The calculations allow predicting the metal arrangement in nanoparticle under different experimental conditions. We present results for two couples of metals, Au/Pt (Δε=0.26 V and Au/Ag (Δε=0.19 V, but conclusions can be generalized to other bimetallic pairs with similar difference in standard reduction potentials. It was proved that both surface and interior compositions can be controlled at nanometer resolution easily by changing the initial reactant concentration inside micelles. Kinetic analysis demonstrates that the confinement of reactants inside micelles has a strong effect on the reaction rates of the metal precursors. As a result, the final nanocatalyst shows a more mixed core and a better defined shell as concentration is higher.

  15. Influence of dispersive forces on the final shape of a reverse micelle.

    Science.gov (United States)

    León, I; Montero, R; Longarte, A; Fernández, José A

    2015-01-21

    Micelles are interesting self-organized structures with multiple applications in chemistry and related with the formation of biological structures. Their final shape depends on a subtle equilibrium between several weak forces: namely, van der Waals and hydrogen bond interactions. In order to address the influence of each type of interaction, the aggregation of cyclohexanol molecules was studied in the gas phase. The geometry of the clusters formed with sizes from 2 to 6 cyclohexanol molecules was elucidated by an IR double resonance technique that combines fs and ns lasers. Comparison of the structures obtained with those from previous studies demonstrates that hydrogen bond plays a central role in defining the general shape, but that its contribution to the overall stabilization energy may be lower than expected in systems with multiple C-H···π interactions. PMID:25486453

  16. Spraying enzymes in microemulsions of AOT in nonpolar organic solvents for fabrication of enzyme electrodes.

    Science.gov (United States)

    Shipovskov, Stepan; Trofimova, Daria; Saprykin, Eduard; Christenson, Andreas; Ruzgas, Tautgirdas; Levashov, Andrey V; Ferapontova, Elena E

    2005-11-01

    A new technique suitable for automated, large-scale fabrication of enzyme electrodes by air-spraying enzymes in organic inks is presented. Model oxidoreductases, tyrosinase (Tyr) and glucose oxidase (GOx), were adapted to octane-based ink by entrapment in a system of reverse micelles (RM) of surfactant AOT in octane to separate and stabilize the catalytically active forms of the enzymes in nonpolar organic media. Nonpolar caoutchouk polymer was also used to create a kind of "dry micelles" at the electrode/solution interface. Enzyme/RM/polymer-containing organic inks were air-brushed onto conductive supports and were subsequently covered by sprayed Nafion membranes. The air-brushed enzyme electrodes exhibited relevant bioelectrocatalytic activity toward catechol and glucose, with a linear detection range of 0.1-100 microM catechol and 0.5-7 mM glucose; the sensitivities were 2.41 A M(-1) cm(-2) and 2.98 mA M(-1) cm(-2) for Tyr and GOx electrodes, respectively. The proposed technique of air-brushing enzymes in organic inks enables automated construction of disposable enzyme electrodes of various designs on a mass-production scale. PMID:16255612

  17. Structure and dynamics of water in nonionic reverse micelles: a combined time-resolved infrared and small angle x-ray scattering study.

    Science.gov (United States)

    van der Loop, Tibert H; Panman, Matthijs R; Lotze, Stephan; Zhang, Jing; Vad, Thomas; Bakker, Huib J; Sager, Wiebke F C; Woutersen, Sander

    2012-07-28

    We study the structure and reorientation dynamics of nanometer-sized water droplets inside nonionic reverse micelles (water/Igepal-CO-520/cyclohexane) with time-resolved mid-infrared pump-probe spectroscopy and small angle x-ray scattering. In the time-resolved experiments, we probe the vibrational and orientational dynamics of the O-D bonds of dilute HDO:H(2)O mixtures in Igepal reverse micelles as a function of temperature and micelle size. We find that even small micelles contain a large fraction of water that reorients at the same rate as water in the bulk, which indicates that the polyethylene oxide chains of the surfactant do not penetrate into the water volume. We also observe that the confinement affects the reorientation dynamics of only the first hydration layer. From the temperature dependent surface-water dynamics, we estimate an activation enthalpy for reorientation of 45 ± 9 kJ mol(-1) (11 ± 2 kcal mol(-1)), which is close to the activation energy of the reorientation of water molecules in ice. PMID:22852627

  18. Structure and dynamics of water in nonionic reverse micelles: A combined time-resolved infrared and small angle x-ray scattering study

    Science.gov (United States)

    van der Loop, Tibert H.; Panman, Matthijs R.; Lotze, Stephan; Zhang, Jing; Vad, Thomas; Bakker, Huib J.; Sager, Wiebke F. C.; Woutersen, Sander

    2012-07-01

    We study the structure and reorientation dynamics of nanometer-sized water droplets inside nonionic reverse micelles (water/Igepal-CO-520/cyclohexane) with time-resolved mid-infrared pump-probe spectroscopy and small angle x-ray scattering. In the time-resolved experiments, we probe the vibrational and orientational dynamics of the O-D bonds of dilute HDO:H2O mixtures in Igepal reverse micelles as a function of temperature and micelle size. We find that even small micelles contain a large fraction of water that reorients at the same rate as water in the bulk, which indicates that the polyethylene oxide chains of the surfactant do not penetrate into the water volume. We also observe that the confinement affects the reorientation dynamics of only the first hydration layer. From the temperature dependent surface-water dynamics, we estimate an activation enthalpy for reorientation of 45 ± 9 kJ mol-1 (11 ± 2 kcal mol-1), which is close to the activation energy of the reorientation of water molecules in ice.

  19. UV-Vis spectral investigation of photophysical properties of a solvatochromic electron donor/acceptor dye within a reverse micelle domain

    Science.gov (United States)

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

    2014-01-01

    The optical response of a solvatochromic dye, [(E)-3-(1-methyl-1H-indol-3-yl)-1-phenylprop-2-en-1-one], N1, has been studied in the AOT/n-heptane/water reverse micellar media using steady-state and time-resolved techniques. To this end variation in the photophysical properties of N1 have been systematically studied as a function of water pool size (w0). Micropolarity, microviscosity, and relative permittivity of the immediate microenvironment surrounding the probe has been estimated from the limiting values of the photophysical parameters of N1 at high w0. Information about the location of the dye in the reverse micellar media has been obtained using the observed results.

  20. Wire-like nano-polyaniline deposited electrochemically in a reverse micelle electrolyte as a pH sensor

    Science.gov (United States)

    Zhao, Fei; Jiao, Han-dong; Zhao, Shi-qiang

    2015-10-01

    Wire-like polyaniline (PANI) films were successfully electrodeposited onto an indium tin oxide (ITO) substrate using a pulse galvanostatic method (PGM) in a reverse micelle electrolyte. The as-prepared PANI films were electrochemically analyzed by cyclic voltammetry and electrochemical impedance spectroscopy in 1 mol·L-1 HClO4 solution. It is found that the as-prepared PANI films are highly porous, exhibit the diameters of approximately 100 nm and the lengths exceeding 3 μm, and have favorable electrochemical activities. Furthermore, the as-prepared wire-like PANI films show a good linear relationship of the potentiometric response curve over the pH value range of 3-10 with a slope of 74.13 mV·pH-1 in 0.5 mol·L-1 K2HPO4 basal solutions. The results demonstrate that the prepared wire-like PANI films are promising pH sensors.

  1. Wire-like nano-polyaniline deposited electrochemically in a reverse micelle electrolyte as a pH sensor

    Institute of Scientific and Technical Information of China (English)

    Fei Zhao; Han-dong Jiao; Shi-qiang Zhao

    2015-01-01

    Wire-like polyaniline (PANI) films were successfully electrodeposited onto an indium tin oxide (ITO) substrate using a pulse gal-vanostatic method (PGM) in a reverse micelle electrolyte. The as-prepared PANI films were electrochemically analyzed by cyclic voltam-metry and electrochemical impedance spectroscopy in 1 mol·L?1 HClO4 solution. It is found that the as-prepared PANI films are highly po-rous, exhibit the diameters of approximately 100 nm and the lengths exceeding 3μm, and have favorable electrochemical activities. Fur-thermore, the as-prepared wire-like PANI films show a good linear relationship of the potentiometric response curve over the pH value range of 3–10 with a slope of 74.13 mV·pH?1 in 0.5 mol·L?1 K2HPO4 basal solutions. The results demonstrate that the prepared wire-like PANI films are promising pH sensors.

  2. Assembly and electroanalytical performance of Prussian blue/polypyrrole composite nanoparticles synthesized by the reverse micelle method

    Energy Technology Data Exchange (ETDEWEB)

    Miao Yuqing; Liu Jiwei, E-mail: biosensors@zjnu.c [Laboratory of Biocatalysis and Biosensor, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004 (China)

    2009-04-15

    We report on the characterization, assembly and electroanalytical performance of Prussian blue/polypyrrole (PBPPy) composite nanoparticles synthesized by the reverse micelle method. Scanning electron microscopy suggests the formation of nanosized PBPPy particles with diameters between 40 and 50 nm. Optical absorption confirms that the particles are composed of Prussian blue (PB) and polypyrrole. PB and PBPPy nanoparticles were anchored onto the surface of cysteine-modified Au electrodes. Cyclic voltammetry experiments show that PB- or PBPPy-modified electrodes exhibit intrinsic electrochemical properties and a high electrocatalytic activity towards H{sub 2}O{sub 2}. PBPPy-modified electrodes exhibit a higher sensitivity to H{sub 2}O{sub 2} than PB-modified electrodes. A linear calibration curve in the concentration range 0.99 {mu}M-8.26 mM H{sub 2}O{sub 2} is constructed with a detection limit of 0.23 {mu}M at a signal-to-noise ratio of 3. Excellent stability is observed for PBPPy-composite-nanoparticle-modified electrodes even in a pH 6 phosphate buffer solution with a high H{sub 2}O{sub 2} concentration (0.99 mM). Glutaraldehyde and Nafion were also employed to immobilize glucose oxidase for the development of PBPPy-based biosensors. The results show that PBPPy composite nanoparticles can be used to develop oxidase-based biosensors.

  3. Influence of Capping Ligands on the Self-organization of Gold Nanoparticles into Superlattices from CTAB Reverse Micelles

    Institute of Scientific and Technical Information of China (English)

    LIN,Jun(林君); ZHOU,Wei-Lie(周维烈); CARPENTER, Everett; O' CONNOR, Charles

    2002-01-01

    Gold nanoparticles with size 3-10 nm (diameter) were prepared by the reduction of HAuCl4 in a CTAB/octane + 1-butanol/H2O reverse micelle system using NaBH4 as the reducing agent. The as-formed gold nanoparticle colloid was characterized by UV/vis absorption spectrum and transmission electron microscopy(TEM). Various capping ligands, such as alkylthiols with different chain length and shape,trioctylphosphine (TOP), and pyridine are used to passivate the gold nanoparticles for the purpose of self-organization into superstructrues.It is shown that the ligands have a great influence on the selforganization of gold nanoparticles into superlattices, and dodecanethiol C12H25SH is confirmed to be the best ligand for the self-organization. Self-organization of C12H25SH-capped gold nanoparticles into 1D, 2D and 3D superlattices has been observed on the carbon-coated copper grid by TEM without using any selective precipitation processs.

  4. Preparation and characterization of bi-metallic nanoparticle catalyst having better anti-coking properties using reverse micelle technique

    Science.gov (United States)

    Zacharia, Thomas

    Energy needs are rising on an exponential basis. The mammoth energy sources like coal, natural gas and petroleum are the cause of pollution. The large outcry for an alternate energy source which is environmentally friendly and energy efficient is heard during the past few years. This is where “Clean-Fuel” like hydrogen gained its ground. Hydrogen is mainly produced by steam methane reforming (SMR). An alternate sustainable process which can reduce the cost as well as eliminate the waste products is Tri-reforming. In both these reforming processes nickel is used as catalyst. However as the process goes on the catalyst gets deactivated due to coking on the catalytic surface. This goal of this thesis work was to develop a bi-metallic catalyst which has better anti-coking properties compared to the conventional nickel catalyst. Tin was used to dope nickel. It was found that Ni3Sn complex around a core of Ni is coking resistant compared to pure nickel catalyst. Reverse micelle synthesis of catalyst preparation was used to control the size and shape of catalytic particles. These studies will benefit researches on hydrogen production and catalyst manufactures who work on different bi-metallic combinations.

  5. Magnetic properties of nanocrystalline Ni-Zn, Zn-Mn, and Ni-Mn ferrites synthesized by reverse micelle technique

    Science.gov (United States)

    Gubbala, S.; Nathani, H.; Koizol, K.; Misra, R. D. K.

    2004-05-01

    Nanocrystalline nickel-zinc, zinc-manganese, and nickel-manganese ferrites synthesized by reverse micelle synthesis technique were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction, and the magnetic behavior studied by Superconducting Quantum Interference Device. The mixed (Ni-Zn, Zn-Mn, and Ni-Mn) ferrites exhibit blocking temperatures of 11, 20, and 15 K, respectively. The small differences in the blocking temperatures are attributed to the magnetocrystalline anisotropy and L-S coupling. The saturation magnetization of nanocrystalline Ni-Zn, Zn-Mn, and Ni-Mn at 300 K was 4.5, 9, and 7 emu/g, respectively, and at 2 K was 15, 19, and 14 emu/g, respectively. The lower saturation magnetization of the nanocrystalline ferrites compared to their bulk counterparts is attributed to the core-shell morphology of the particles consisting of ferromagnetically aligned core spins and a spin-glass-like surface layer.

  6. Magnetic properties of nanocrystalline Ni-Zn, Zn-Mn, and Ni-Mn ferrites synthesized by reverse micelle technique

    International Nuclear Information System (INIS)

    Nanocrystalline nickel-zinc, zinc-manganese, and nickel-manganese ferrites synthesized by reverse micelle synthesis technique were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction, and the magnetic behavior studied by Superconducting Quantum Interference Device. The mixed (Ni-Zn, Zn-Mn, and Ni-Mn) ferrites exhibit blocking temperatures of 11, 20, and 15 K, respectively. The small differences in the blocking temperatures are attributed to the magnetocrystalline anisotropy and L-S coupling. The saturation magnetization of nanocrystalline Ni-Zn, Zn-Mn, and Ni-Mn at 300 K was 4.5, 9, and 7 emu/g, respectively, and at 2 K was 15, 19, and 14 emu/g, respectively. The lower saturation magnetization of the nanocrystalline ferrites compared to their bulk counterparts is attributed to the core-shell morphology of the particles consisting of ferromagnetically aligned core spins and a spin-glass-like surface layer

  7. Optical Properties of Titania Coatings Prepared by Inkjet Direct Patterning of a Reverse Micelles Sol-Gel Composition

    Directory of Open Access Journals (Sweden)

    Veronika Schmiedova

    2015-08-01

    Full Text Available Thin layers of titanium dioxide were fabricated by direct inkjet patterning of a reverse micelles sol-gel composition onto soda-lime glass plates. Several series of variable thickness samples were produced by repeated overprinting and these were further calcined at different temperatures. The resulting layers were inspected by optical and scanning electronic microscopy and their optical properties were investigated by spectroscopic ellipsometry in the range of 200–1000 nm. Thus the influence of the calcination temperature on material as well as optical properties of the patterned micellar titania was studied. The additive nature of the deposition process was demonstrated by a linear dependence of total thickness on the number of printed layers without being significantly affected by the calcination temperature. The micellar imprints structure of the titania layer resulted into significant deviation of measured optical constants from the values reported for bulk titania. The introduction of a void layer into the ellipsometric model was found necessary for this particular type of titania and enabled correct ellipsometric determination of layer thickness, well matching the thickness values from mechanical profilometry.

  8. Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method.

    Science.gov (United States)

    Gavrilović, Tamara V; Jovanović, Dragana J; Lojpur, Vesna; Dramićanin, Miroslav D

    2014-01-01

    Synthesis of Eu(3+)- and Er(3+)/Yb(3+)-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu(3+)-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er(3+)/Yb(3+)-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from (2)H11/2 → (2)I15/2 and (4)S3/2 → (4)I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K(-1), which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers. PMID:24572638

  9. Characterization of lipase in reversed micelles formulated by Cibacron Blue F-3GA modified Span 85

    DEFF Research Database (Denmark)

    Zhang, Dong Hao; Guo, Zheng; Sun, Yan

    2007-01-01

    reversed micellar technology could increase the apparent activity of enzymes and even yield superactivity for specific enzymes (6). Lipases are ubiquitous enzymes that could find many important applications (7, 8). The natural substrate of lipases is triglyceride, and the majority of lipases are......Sorbitan trioleate (Span 85) modified by Cibacron Blue F-3GA (CB) was prepared and used as an affinity surfactant to formulate a reversed micellar system for Candida rugosa lipase (CRL) solubilization. The system was characterized and evaluated by employing CRL-catalyzed hydrolysis of olive oil as...... a model reaction. The micellar hydrodynamic radius results reflected, to some extent, the redistribution of surfactant and water after enzyme addition, and the correlation between surfactant formulation, water content (W0), micellar size, and enzyme activity. An adequate modification density of CB...

  10. Synthesis of Crystalline Nanosized Titanium Dioxide via a Reverse Micelle Method at Room Temperature

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Crystalline TiO2 nanoparticles were synthesized by hydrolysis of titanium tetrabutoxidein the presence of hydrochloric aeid in NP-5 (lgepal CO-520)/ cyclohcxane reverse micellesolution at room temperature. Pure rutilc nanoparticles were obtained at an appropriate acidconcentration. The influcnces of various reaction conditions such as the concentration of acids,water content value (w=[H2O]/[NP-5]) on the formation, crystal phase, morphology, and size of theTiO2 particles were investigated.

  11. Synthesis of sol–gel silica particles in reverse micelles with mixed-solvent polar cores: tailoring nanoreactor structure and properties

    Energy Technology Data Exchange (ETDEWEB)

    Bürglová, Kristýna; Hlaváč, Jan [Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry (Czech Republic); Bartlett, John R., E-mail: jbartlett@usc.edu.au [University of the Sunshine Coast, Faculty of Science, Health, Education and Engineering (Australia)

    2015-07-15

    In this paper, we describe a new approach for producing metal oxide nano- and microparticles via sol–gel processing in confined media (sodium bis(2-ethylhexyl)sulfosuccinate reverse micelles), in which the chemical and physical properties of the polar aqueous core of the reverse micelles are modulated by the inclusion of a second polar co-solvent. The co-solvents were selected for their capacity to solubilise compounds with low water solubility and included dimethylsulfoxide, dimethylformamide, ethylene glycol, n-propanol, dimethylacetamide and N-methylpyrrolidone. A broad range of processing conditions across the sodium bis(2-ethylhexyl)sulfosuccinate/cyclohexane/water phase diagram were identified that are suitable for preparing particles with dimensions <50 to >500 nm. In contrast, only a relatively narrow range of processing conditions were suitable for preparing such particles in the absence of the co-solvents, highlighting the role of the co-solvent in modulating the properties of the polar core of the reverse micelles. A mechanism is proposed that links the interactions between the various reactive sites on the polar head group of the surfactant and the co-solvent to the nucleation and growth of the particles.

  12. Synthesis of sol–gel silica particles in reverse micelles with mixed-solvent polar cores: tailoring nanoreactor structure and properties

    International Nuclear Information System (INIS)

    In this paper, we describe a new approach for producing metal oxide nano- and microparticles via sol–gel processing in confined media (sodium bis(2-ethylhexyl)sulfosuccinate reverse micelles), in which the chemical and physical properties of the polar aqueous core of the reverse micelles are modulated by the inclusion of a second polar co-solvent. The co-solvents were selected for their capacity to solubilise compounds with low water solubility and included dimethylsulfoxide, dimethylformamide, ethylene glycol, n-propanol, dimethylacetamide and N-methylpyrrolidone. A broad range of processing conditions across the sodium bis(2-ethylhexyl)sulfosuccinate/cyclohexane/water phase diagram were identified that are suitable for preparing particles with dimensions <50 to >500 nm. In contrast, only a relatively narrow range of processing conditions were suitable for preparing such particles in the absence of the co-solvents, highlighting the role of the co-solvent in modulating the properties of the polar core of the reverse micelles. A mechanism is proposed that links the interactions between the various reactive sites on the polar head group of the surfactant and the co-solvent to the nucleation and growth of the particles

  13. Research Progress on Reversed Micelles Extraction of Proteins%反胶束萃取蛋白质的研究进展

    Institute of Scientific and Technical Information of China (English)

    杨铃

    2015-01-01

    介绍了反胶束萃取体系的定义和特点及其溶解和蛋白质的萃取原理,并较为详细地叙述了表面活性剂种类与浓度、离子种类与强度、蛋白质分子量与浓度以及水相的pH值等因素对反胶束萃取的影响,综述了近年来国内外有关反胶束萃取蛋白质的应用研究,并对其前景进行了展望。%This paper is introduced the concept and characteristics of reverse micelles system and the extraction mechanism of protein, and is described type and concentration of surfactant, species and strength of ionic, molecular weight and concentration of protein and pH value of the aqueous phase and other factors on the extraction in reverse micelles, and is reviewed the domestic and foreign related protein extraction in reverse micelles, and its foreground is prospected.

  14. Synthesis of nanocrystalline materials through reverse micelles: A versatile methodology for synthesis of complex metal oxides

    Indian Academy of Sciences (India)

    Ashok K Ganguli; Sonalika Vaidya; Tokeer Ahmad

    2008-06-01

    We have been successful in obtaining monophasic nanosized oxides with varying chemical compositions using the reverse micellar method. Here we describe our methodology to obtain important metal oxides like ceria, zirconia and zinc oxide. The oxalate of cerium, zirconium and zinc were synthesized using the reverse micellar route. While nanorods of zinc oxalate with dimension, 120 nm in diameter and 600 nm in length, could be obtained, whereas spherical particles of size, 4–6 nm, were obtained for cerium oxalate. These precursors were heated to form their respective oxides. Mixture of nanorods and nanoparticles of cerium oxide was obtained. ZrO2 nanoparticles of 3–4 nm size were obtained by the thermal decomposition of zirconium oxalate precursor. ZnO nanoparticles (55 nm) were obtained by the decomposition of zinc oxalate nanorods. Photoluminescence (PL) studies at 20 K shows the presence of three peaks corresponding to free excitonic emission, free to bound and donor–acceptor transitions. We also synthesized nanoparticles corresponding to Ba1–PbZrO3 using the reverse micellar route. The dielectric constant and loss were stable with frequency and temperature for the solid solution.

  15. Metal Carboxylate Nanorods and Metal Oxide Nanoparticles Synthesized Using Reverse Micelles

    Institute of Scientific and Technical Information of China (English)

    Ashok.K.Ganguli(Department; of; Chemistry; Indian; Institute; of; Technology

    2007-01-01

    1 Results Nanorods of transition metal (Cu,Ni,Mn,Zn,Co and Fe) carboxylates (oxalates and succinates) have been synthesized using a reverse-micellar technique[1-3].These oxalate nanorods have been shown to be an ideal source for obtaining monophasic and homogeneous nanoparticles of transition metal oxides at low temperatures of 450 ℃.Grain size of oxide nanoparticles could be controlled by optimizing the nature of non-polar solvent and surfactant.The metal oxalate precursor could be decomposed in suitab...

  16. Manganese ferrite prepared using reverse micelle process: Structural and magnetic properties characterization

    Energy Technology Data Exchange (ETDEWEB)

    Hashim, Mohd, E-mail: md.hashim09@gmail.com [Department of Physics, Aligarh Muslim University, Aligarh 202002 (India); Shirsath, Sagar E. [Spin Device Technology Centre, Department of Engineering, Shinshu University, Nagano 380-8553 (Japan); Meena, S.S. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Mane, M.L. [Department of Physics, S.G.R.G. Shinde Mahavidyalaya, Paranda 413502, MS (India); Kumar, Shalendra [School of Materials Science and Engineering, Changwon National University, Changwon, Gyeongnam 641-773 (Korea, Republic of); Bhatt, Pramod [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Kumar, Ravi [Centre for Material Science Engineering, National Institute of Technology, Hamirpur, HP (India); Prasad, N.K.; Alla, S.K. [Deptartment of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Shah, Jyoti; Kotnala, R.K. [National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Mohammed, K.A. [Department of Mathematics & Physics Sciences, College of Arts and Sciences, University of Nizwa, Nizwa (Oman); Şentürk, Erdoğan [Department of Physics, Sakarya University, Esentepe, 54187 Sakarya (Turkey); Alimuddin [Department of Physics, Aligarh Muslim University, Aligarh 202002 (India)

    2015-09-05

    Highlights: • Preparation of Mn{sup 3+} substituted MnFe{sub 2}O{sub 4} ferrite by Reverse microemulsion process. • Characterization by XRD, SEM, VSM, Mössbauer spectroscopy and dielectric measurements techniques. • Magnetic properties of MnFe{sub 2}O{sub 4} enhanced after Mn{sup 3+} substitution. • The dielectric constant and ac conductivity increased with Mn{sup 3+} substitution. - Abstract: Reverse microemulsion process was employed to prepare of nanocrystalline Mn{sup 3+} substituted MnFe{sub 2−x}Mn{sub x}O{sub 4} ferrites. The structural, magnetic and dielectric properties were studied for different concentrations of Mn{sup 3+}. The structural and microstructural properties were analyzed using X-ray diffraction technique (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy techniques. The phase identification of the materials was studied by Rietveld refined XRD patterns which reveals single phase with cubic symmetry for the samples. The lattice parameters were ranged in between 8.369 and 8.379 Å and do not show any significant change with the substitution of Mn{sup 3+}. The average particles size was found to be around 11 ± 3 nm. Magnetization results obtained from the vibrating sample magnetometer (VSM) confirm that the substitution of Mn{sup 3+} in MnFe{sub 2}O{sub 4} ferrite caused an increase in the saturation magnetization and coercivity. The dependence of Mössbauer parameters on Mn{sup 3+} substitution has been analyzed. Magnetic behavior of the samples were also studied at field cooled (FC) and zero field cooled (ZFC) mode. The dependence of Mössbauer parameters on Mn{sup 3+} substitution was also analyzed. All the magnetic characterization shows that Mn{sup 3+} substitution enhance the magnetic behavior of MnFe{sub 2}O{sub 4} ferrite nanoparticles.

  17. Manganese ferrite prepared using reverse micelle process: Structural and magnetic properties characterization

    International Nuclear Information System (INIS)

    Highlights: • Preparation of Mn3+ substituted MnFe2O4 ferrite by Reverse microemulsion process. • Characterization by XRD, SEM, VSM, Mössbauer spectroscopy and dielectric measurements techniques. • Magnetic properties of MnFe2O4 enhanced after Mn3+ substitution. • The dielectric constant and ac conductivity increased with Mn3+ substitution. - Abstract: Reverse microemulsion process was employed to prepare of nanocrystalline Mn3+ substituted MnFe2−xMnxO4 ferrites. The structural, magnetic and dielectric properties were studied for different concentrations of Mn3+. The structural and microstructural properties were analyzed using X-ray diffraction technique (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy techniques. The phase identification of the materials was studied by Rietveld refined XRD patterns which reveals single phase with cubic symmetry for the samples. The lattice parameters were ranged in between 8.369 and 8.379 Å and do not show any significant change with the substitution of Mn3+. The average particles size was found to be around 11 ± 3 nm. Magnetization results obtained from the vibrating sample magnetometer (VSM) confirm that the substitution of Mn3+ in MnFe2O4 ferrite caused an increase in the saturation magnetization and coercivity. The dependence of Mössbauer parameters on Mn3+ substitution has been analyzed. Magnetic behavior of the samples were also studied at field cooled (FC) and zero field cooled (ZFC) mode. The dependence of Mössbauer parameters on Mn3+ substitution was also analyzed. All the magnetic characterization shows that Mn3+ substitution enhance the magnetic behavior of MnFe2O4 ferrite nanoparticles

  18. PEG-b-PCL copolymer micelles with the ability of pH-controlled negative-to-positive charge reversal for intracellular delivery of doxorubicin.

    Science.gov (United States)

    Deng, Hongzhang; Liu, Jinjian; Zhao, Xuefei; Zhang, Yuming; Liu, Jianfeng; Xu, Shuxin; Deng, Liandong; Dong, Anjie; Zhang, Jianhua

    2014-11-10

    The application of PEG-b-PCL micelles was dampened by their inherent low drug-loading capability and relatively poor cell uptake efficiency. In this study, a series of novel PEG-b-PCL copolymers methoxy poly(ethylene glycol)-b-poly(ε-caprolactone-co-γ-dimethyl maleamidic acid -ε-caprolactone) (mPEG-b-P(CL-co-DCL)) bearing different amounts of acid-labile β-carboxylic amides on the polyester moiety were synthesized. The chain structure and chemical composition of copolymers were characterized by (1)H NMR, Fourier transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC). mPEG-b-P(CL-co-DCL) with critical micellar concentrations (CMCs) of 3.2-6.3 μg/mL could self-assemble into stable micelles in water with diameters of 100 to 150 nm. Doxorubicin (DOX), a cationic hydrophobic drug, was successfully encapsulated into the polymer micelles, achieving a very high loading content due to electrostatic interaction. Then the stability, charge-conversional behavior, loading and release profiles, cellular uptake and in vitro cytotoxicity of free drug and drug-loaded micelles were evaluated. The β-carboxylic amides functionalized polymer micelles are negatively charged and stable in neutral solution but quickly become positively charged at pH 6.0, due to the hydrolysis of β-carboxylic amides in acidic conditions. The pH-triggered negative-to-positive charge reversal not only resulted in a very fast drug release in acidic conditions, but also effectively enhanced the cellular uptake by electrostatic absorptive endocytosis. The MTT assay demonstrated that mPEG-b-P(CL-co-DCL) micelles were biocompatible to HepG2 cells while DOX-loaded micelles showed significant cytotoxicity. In sum, the introduction of acid-labile β-carboxylic amides on the polyester block in mPEG-b-P(CL-co-DCL) exhibited great potentials for the modifications in the stability in blood circulation, drug solubilization, and release properties, as well as cell internalization and

  19. On-line concentration of neutral analytes for micellar electrokinetic chromatography. 5. Field-enhanced sample injection with reverse migrating micelles.

    Science.gov (United States)

    Quirino, J P; Terabe, S

    1998-05-01

    Elementary conditions for the on-line concentration of neutral analytes by field-enhanced sample injection with reverse migrating micelles for micellar electrokinetic chromatography is presented. Acidic phosphate buffers containing micelles of sodium dodecyl sulfate are utilized as both sample solvent and separation solution. After the capillary is conditioned with a separation solution, a water plug is hydrodynamically injected to achieve field enhancement at the injection end of the capillary during injection by application of voltage. A model is provided to give insight into the stacking scheme. Significant detector response improvements are confirmed experimentally. Moreover, utility of the technique for the analysis of a real sample is tested using urine spiked with testosterone and progesterone. PMID:21651282

  20. Layerwise decomposition of water dynamics in reverse micelles: A simulation study of two-dimensional infrared spectrum

    Science.gov (United States)

    Biswas, Rajib; Furtado, Jonathan; Bagchi, Biman

    2013-10-01

    We present computer simulation study of two-dimensional infrared spectroscopy (2D-IR) of water confined in reverse micelles (RMs) of various sizes. The present study is motivated by the need to understand the altered dynamics of confined water by performing layerwise decomposition of water, with an aim to quantify the relative contributions of different layers water molecules to the calculated 2D-IR spectrum. The 0-1 transition spectra clearly show substantial elongation, due to inhomogeneous broadening and incomplete spectral diffusion, along the diagonal in the surface water layer of different sized RMs. Fitting of the frequency fluctuation correlation functions reveal that the motion of the surface water molecules is sub-diffusive and indicate the constrained nature of their dynamics. This is further supported by two peak nature of the angular analogue of van Hove correlation function. With increasing system size, the water molecules become more diffusive in nature and spectral diffusion almost completes in the central layer of the larger size RMs. Comparisons between experiments and simulations establish the correspondence between the spectral decomposition available in experiments with the spatial decomposition available in simulations. Simulations also allow a quantitative exploration of the relative role of water, sodium ions, and sulfonate head groups in vibrational dephasing. Interestingly, the negative cross correlation between force on oxygen and hydrogen of O-H bond in bulk water significantly decreases in the surface layer of each RM. This negative cross correlation gradually increases in the central water pool with increasing RMs size and this is found to be partly responsible for the faster relaxation rate of water in the central pool.

  1. Nuclear relaxation induced by diffusion in confined media; the case of inverted micelles

    International Nuclear Information System (INIS)

    This work emphasizes the specificities of molecular motions in restricted media observed by NMR. The observation of proton nuclear relaxation of small water pools in AOT reversed micelles has led to separation of dipolar contributions using substitution by deuterium. The water-water contributions to relaxation are easily explained by well-known models and show that water rotational movements are, at most, five times slower than in pure water. The other contributions display a strong frequency dependence with spectrometer frequency and, in order to explain them, a specific dipolar relaxation model was developed between two particles whose movements are restricted to the surface of a sphere and in a concentric sphere respectively. This model was generalized to all cases of diffusion movements of particles in a spherical symmetry environment. In the case of AOT micelles, this model can not explain the experimental results. An elementary discussion taking into account the polar heads specificities and their interactions with water lead to a qualitative interpretation of the experimental data. (author)

  2. Reverse Micelles Directed Synthesis of TiO2-CeO2 Mixed Oxides and Investigation of Their Crystal Structure and Morphology

    Czech Academy of Sciences Publication Activity Database

    Matějová, Lenka; Valeš, V.; Fajgar, Radek; Matěj, Z.; Holý, V.; Šolcová, Olga

    2013-01-01

    Roč. 198, FEB (2013), s. 485-495. ISSN 0022-4596 R&D Projects: GA ČR GA203/09/1117; GA TA ČR TA01020804 Grant ostatní: GA ČR(CZ) GAP204/11/0785 Institutional support: RVO:67985858 Keywords : titania–ceria * cerium titanate * sol-gel preparation * reverse micelle * X-ray diffraction * Raman spectroscopy Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.200, year: 2013

  3. A small angle neutron scattering study on the mixtures of pluronic L121 and anionic surfactant AOT

    Indian Academy of Sciences (India)

    G Ghosh; V K Aswal; D Varade

    2008-11-01

    Small angle neutron scattering (SANS) experiments have been carried out on the micellar solutions containing mixtures of a hydrophobic triblock copolymer (L121, EO5PO68EO5) and a hydrophobic anionic surfactant (AOT, sodium bis(2-ethylhexyl)sulphosuccinate) in water with varying ratio () of AOT to L121 for = 0.15, 0.2, 0.3, 0.5 and 0.6. It is known that either L121 or AOT alone forms vesicles in water, but in the mixture with appropriate ratio of the two components a thermodynamically stable, isotropic solution of apparently small micelle-like aggregates is formed. We find that these micelles are prolate ellipsoidal.

  4. Effect of gamma-ray irradiation on the size and properties of CdS quantum dots in reverse micelles

    International Nuclear Information System (INIS)

    Cadmium sulfide quantum dots 1.3–5.6 nm in size have been synthesized in sodium bis(2-ethylhexy1)sulfosuccinate (AOT)–water–isooctane micellar solutions with various [H2O]/[AOT] molar ratios (w=2.5, 5.0 or 10). Gamma irradiation method has been used to change the size and optical properties of quantum dots. It has been found that γ-irradiation reduces the size polydispersity of quantum dots in the micellar system and alters their fluorescent properties. Fluorescence intensity is enhanced after γ-irradiation. The average fluorescence lifetime of single quantum dots sized 5.2±0.4 nm increases from 5.14 to 6.39 ns after γ-irradiation at a dose of 7.9 kGy. To the best of our knowledge, this is the first report on fluorescence lifetime of single CdS quantum dots in micellar solution. - Highlights: • Gamma irradiation method has been used successfully to change the size and optical properties of CdS quantum dots synthesized in micellar solutions. • γ-Irradiation reduces the size polydispersity of quantum dots in the micellar system. • Fluorescence intensity of CdS quantum dots is enhanced after γ-irradiation. • Fluorescence lifetime of single CdS quantum dots increases after γ-irradiation

  5. Reverse micelle-mediated dispersive liquid-liquid microextraction of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid.

    Science.gov (United States)

    Tayyebi, Moslem; Yamini, Yadollah; Moradi, Morteza

    2012-09-01

    A supramolecular solvent consisting of reverse micelles of decanoic acid, dispersed in a continuous phase of tetrahydrofuran:water, was proposed as an efficient microextraction technique for extraction of selected chlorophenoxy acid herbicides from water samples prior to high-performance liquid chromatography UV determination. The disperser solvent (1.0 mL tetrahydrofuran) containing 20 mg decanoic acid was rapidly injected into 10.0 mL of water sample. After centrifugation, the reverse micelle-rich phase (25 ± 0.5 μL) was floated at top of the home-designed centrifuge tube. The solvent was collected and 20 μL of it was injected into high-performance liquid chromatography for analysis. The results showed that the in situ solvent formation and extraction process can be completed in a few seconds. Under the optimal conditions, limits of detection of the method for 4-chloro-2-methylphenoxyacetic acid and 2,4-dichlorophenoxyacetic acid were in the range of 0.5-0.8 μg L(-1) and the repeatability of the proposed method, expressed as relative standard deviation, varied in the range of 2.5-3.2%. Linearity was found to be in the range of 1-200 μg L(-1) and the preconcentration factors were between 148 and 157. The mean percentage recoveries exceeded 92.0% for all the spiking levels in real water samples. PMID:22753042

  6. The kinetics of synthesis and mechanism of coagulation of gold nanoparticles in Triton N-42 reverse micelles

    Science.gov (United States)

    Bulavchenko, A. I.; Arymbaeva, A. T.; Tatarchuk, V. V.

    2008-05-01

    The reduction of Au(III) with hydrazine monohydrate in micellar Triton N-42 solutions was shown to be an autocatalytic reaction. Its rate constants were calculated. The growth of a gold nucleus proceeded as a result of surface reduction until the polar micelle nanocavity was completely filled. Calculations according to the Derjaguin-Landau-Verway-Overbeck theory showed that the fate of nanoparticles formed depended on interparticle interaction energy. At a small radius of particles, high surface potential, and fairly thick surfactant surface layer, stable systems were formed. The coagulation zones were calculated depending on the structural parameters of nanoparticles and micelles. If a nanoparticle grew larger than 6.1 nm at a surface potential lower than 10 mV and surface layer thickness ˜1.6 nm, the potential well depth exceeded 3/2 kT in magnitude, and coagulation occurred in the system.

  7. Lenghty reverse poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) polymeric micelles and gels for sustained release of antifungal drugs.

    Science.gov (United States)

    Figueroa-Ochoa, Edgar B; Villar-Alvarez, Eva M; Cambón, Adriana; Mistry, Dharmista; Llovo, José; Attwood, David; Barbosa, Silvia; Soltero, J F Armando; Taboada, Pablo

    2016-08-20

    In this work, we present a detailed study of the potential application of polymeric micelles and gels of four different reverse triblock poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) copolymers (BOnEOmBOn, where n denotes the respective block lengths), specifically BO8EO90BO8, BO14EO378BO14, BO20EO411BO20 and BO21EO385BO21, as effective drug transport nanocarriers. In particular, we tested the use of this kind of polymeric nanostructures as reservoirs for the sustained delivery of the antifungals griseofulvin and fluconazole for oral and topical administration. Polymeric micelles and gels formed by these copolymers were shown to solubilize important amounts of these two drugs and to have a good stability in physiologically relevant conditions for oral or topical administration. These polymeric micellar nanocarriers were able to release drugs in a sustained manner, being the release rate slower as the copolymer chain hydrophobicity increased. Different sustained drug release profiles were observed depending on the medium conditions. Gel nanocarriers were shown to display longer sustained release rates than micellar formulations, with the existence of a pulsatile-like release mode under certain solution conditions as a result of their inner network structure. Certain bioadhesive properties were observed for the polymeric physical gels, being moderately tuned by the length and hydrophobicity of the polymeric chains. Furthermore, polymeric gels and micelles showed activity against the yeast Candida albicans and the mould demartophytes (Trichophyton rubrum and Microsporum canis) and, thus, may be useful for the treatment of different cutaneous fungal infections. PMID:27289012

  8. pH-Regulated surface property and pH-reversible micelle transition of a tertiary amine-based gemini surfactant in aqueous solution.

    Science.gov (United States)

    Lu, Hongsheng; Xue, Miao; Wang, Baogang; Huang, Zhiyu

    2015-12-21

    A series of tertiary amide-based gemini surfactants, 2,2'-(1,4-phenylenebis(oxy))bis(N-(3-(dimethylamino)propyl)alkylamide), abbreviated as Cm-A-Cm (m = 8; 10; 12; 14), were synthesized. The surface property and aggregation behaviors of the Cm-A-Cm aqueous solutions were studied in detail. The Cm-A-Cm exhibited high and pH-regulated surface activity at the air/water interface; i.e., the critical micelle concentration was 5.6 × 10(-6) mol L(-1) at pH = 2.50 when m = 14 and was further regulated to 1.8 × 10(-6) mol L(-1) by altering the pH to 6.50. When the pH was tuned from 2.0 to 12.0, the appearance of the C12-A-C12 aqueous solution (35 mM) underwent 5 states: transparent water-like solution, viscous fluid, gel-like fluid, turbid liquid and dispersion system with white precipitate. The results of rheology, cryogenic transmission electron microscopy, and dynamic light scattering characterization revealed that the transition from water-like to viscous or gel-like liquid was actually due to aggregate microstructure transition from spherical to worm-like micelles. This transition was completely reversible between pH = 2.50 and 6.81, tuned by adding HCl and NaOH solutions for at least 4 cycles. Similar micellar transitions regulated by pH were also found for m = 8 and 10, whereas only worm-like micelles were formed for m = 14 at both acidic and nearly neutral conditions. Finally, a reasonable mechanism of aggregate behavior transition was proposed from the viewpoint of the molecular states, molecular structures, and the intra- and inter-molecular interactions. PMID:26411356

  9. Trend estimates of AERONET-observed and model-simulated AOTs between 1993 and 2013

    Science.gov (United States)

    Yoon, J.; Pozzer, A.; Chang, D. Y.; Lelieveld, J.; Kim, J.; Kim, M.; Lee, Y. G.; Koo, J.-H.; Lee, J.; Moon, K. J.

    2016-01-01

    Recently, temporal changes in Aerosol Optical Thickness (AOT) have been investigated based on model simulations, satellite and ground-based observations. Most AOT trend studies used monthly or annual arithmetic means that discard details of the generally right-skewed AOT distributions. Potentially, such results can be biased by extreme values (including outliers). This study additionally uses percentiles (i.e., the lowest 5%, 25%, 50%, 75% and 95% of the monthly cumulative distributions fitted to Aerosol Robotic Network (AERONET)-observed and ECHAM/MESSy Atmospheric Chemistry (EMAC)-model simulated AOTs) that are less affected by outliers caused by measurement error, cloud contamination and occasional extreme aerosol events. Since the limited statistical representativeness of monthly percentiles and means can lead to bias, this study adopts the number of observations as a weighting factor, which improves the statistical robustness of trend estimates. By analyzing the aerosol composition of AERONET-observed and EMAC-simulated AOTs in selected regions of interest, we distinguish the dominant aerosol types and investigate the causes of regional AOT trends. The simulated and observed trends are generally consistent with a high correlation coefficient (R = 0.89) and small bias (slope±2σ = 0.75 ± 0.19). A significant decrease in EMAC-decomposed AOTs by water-soluble compounds and black carbon is found over the USA and the EU due to environmental regulation. In particular, a clear reversal in the AERONET AOT trend percentiles is found over the USA, probably related to the AOT diurnal cycle and the frequency of wildfires. In most of the selected regions of interest, EMAC-simulated trends are mainly attributed to the significant changes of the dominant aerosols; e.g., significant decrease in sea salt and water soluble compounds over Central America, increase in dust over Northern Africa and Middle East, and decrease in black carbon and organic carbon over Australia.

  10. Paracetamol biodegradation by activated sludge and photocatalysis and its removal by a micelle-clay complex, activated charcoal, and reverse osmosis membranes.

    Science.gov (United States)

    Karaman, Rafik; Khamis, Mustafa; Abbadi, Jehad; Amro, Ahmad; Qurie, Mohannad; Ayyad, Ibrahim; Ayyash, Fatima; Hamarsheh, Omar; Yaqmour, Reem; Nir, Shlomo; Bufo, Sabino A; Scrano, Laura; Lerman, Sofia; Gur-Reznik, Shirra; Dosoretz, Carlos G

    2016-10-01

    Kinetic studies on the stability of the pain killer paracetamol in Al-Quds activated sludge demonstrated that paracetamol underwent biodegradation within less than one month to furnish p-aminophenol in high yields. Characterizations of bacteria contained in Al-Quds sludge were accomplished. It was found that Pseudomonas aeruginosa is the bacterium most responsible for the biodegradation of paracetamol to p-aminophenol and hydroquinone. Batch adsorptions of paracetamol and its biodegradation product (p-aminophenol) by activated charcoal and a composite micelle (octadecyltrimethylammonium)-clay (montmorillonite) were determined at 25°C. Adsorption was adequately described by a Langmuir isotherm, and indicated better efficiency of removal by the micelle-clay complex. The ability of bench top reverse osmosis (RO) plant as well as advanced membrane pilot plant to remove paracetamol was also studied at different water matrixes to test the effect of organic matter composition. The results showed that at least 90% rejection was obtained by both plants. In addition, removal of paracetamol from RO brine was investigated by using photocatalytic processes; optimal conditions were found to be acidic or basic pH, in which paracetamol degraded in less than 5 min. Toxicity studies indicated that the effluent and brine were not toxic except for using extra low energy membrane which displayed a half maximal inhibitory concentration (IC-50) value of 80%. PMID:26852629

  11. Silica-coated iron-oxide nanoparticles synthesized as a T2 contrast agent for magnetic resonance imaging by using the reverse micelle method

    International Nuclear Information System (INIS)

    We synthesized iron-oxide (Fe3O4) nanoparticles by using the reverse micelle method and coated them with biocompatible silica. The coated nanoparticles were found to be spherical in the TEM images and showed a uniform size distribution with an average diameter of 10 nm. The T1 and the T2 relaxation times of hydrogen protons in aqueous solutions with various concentrations of silica-coated nanoparticles were determined by using a magnetic resonance (MR) scanner. We found that the T2 relaxivity was much larger than the T1 relaxivity for the nanoparticle contrast agent, which reflected the fact that the T2 relaxation was mainly influenced by outer sphere processes. The T2 relaxivity was found to be 15 times larger than that for the commercial Gd-DTPA-BMA contrast agent. This result demonstrates that silica-coated iron oxide nanoparticles are applicable as a T2 agent in magnetic resonance imaging.

  12. Synthesis and characterization of erbium-doped SiO2 nanoparticles fabricated by using reverse micelle and sol-gel processing

    International Nuclear Information System (INIS)

    Erbium-doped SiO2 nanoparticles have been synthesized using a reverse micelle technique combined with metal-alkoxide hydrolysis and condensation. The sizes and the morphologies of the erbium-doped SiO2 nanoparticles could be changed by varying the molar ratio of water to surfactant. The sizes and the morphologies of the erbium-doped SiO2 nanoparticles were examined by using a transmission electron microscope. The average size of synthesized erbium-doped SiO2 nanoparticles was approximately 20 - 25 nm and that of the erbium particles was 3 - 5 nm. The effects of the synthesis parameters, such as the molar ratio of water to surfactant, are discussed.

  13. Functional BaTiO3 nanostructures immobilized onto si-based substrates using sol–gel and reverse micelle techniques

    International Nuclear Information System (INIS)

    The current tendency toward miniaturization of electronic devices has driven the interest in developing ferroelectric materials in low dimensions. In this work, for the preparation of lead-free BaTiO3 nanoparticles, we used a combination of the sol–gel method with the reverse micelles techniques. Moreover, previously to the thermal treatment, it was necessary to remove the surfactant. For this stage, oleic acid was used to stabilize the nanoparticles in the solution. Then, nanometer-sized particles were deposited on different substrates (Si, Pt/TiO2/SiO2/Si). The influence of different modes of deposition on particle size, degree of agglomeration, was analyzed. The mean particle size was 10 nm. Finally, the deposition of BaTiO3 particles on a conductive substrate such as the wafer of platinum (Pt/TiO2/SiO2/Si) was confirmed by several AFM techniques

  14. Synthesis and characterization of erbium-doped SiO{sub 2} nanoparticles fabricated by using reverse micelle and sol-gel processing

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hoyyul [Korea Electrotechnology Research Institute, Changwon (Korea, Republic of); Bae, Dongsik [Changwon National University, Changwon (Korea, Republic of)

    2012-11-15

    Erbium-doped SiO{sub 2} nanoparticles have been synthesized using a reverse micelle technique combined with metal-alkoxide hydrolysis and condensation. The sizes and the morphologies of the erbium-doped SiO{sub 2} nanoparticles could be changed by varying the molar ratio of water to surfactant. The sizes and the morphologies of the erbium-doped SiO{sub 2} nanoparticles were examined by using a transmission electron microscope. The average size of synthesized erbium-doped SiO{sub 2} nanoparticles was approximately 20 - 25 nm and that of the erbium particles was 3 - 5 nm. The effects of the synthesis parameters, such as the molar ratio of water to surfactant, are discussed.

  15. Preparation of AgCl-polyacrylamide composite microspheres via combination of a polymer microgel template method and a reverse micelle technique.

    Science.gov (United States)

    Zhang, Ying; Fang, Yu; Xia, Huiyun; Xie, Yuxia; Wang, Ruifang; Li, Xuejun

    2006-08-01

    A new route was created for the preparation of AgCl-polyacrylamide (AgCl-PAM) composite microspheres with patterned surface structures. The route is a combination of a polymer microgel template method and a reverse micelle technique. The size of the AgCl nanoparticles existing on the surfaces of the composite microspheres and the clearness of the surface patterns of the composite microspheres can be altered by simply adjusting the amount of precipitated AgCl and the rate of the deposition reaction. The route can be also used for the preparation of other water-insoluble salt-polymer composite microspheres, such as BaSO(4)-PAM. It is expected that the composite microspheres with patterned surface structures may not only combine the advantages of polymers and those of inorganic compounds, but also combine the advantages of microspheres in the micrometer size range and those in the nanometer size range. PMID:16678839

  16. Synthesis and characterization of erbium-doped SiO2 nanoparticles fabricated by using reverse micelle and sol-gel processing

    Science.gov (United States)

    Park, Hoyyul; Bae, Dong-Sik

    2012-11-01

    Erbium-doped SiO2 nanoparticles have been synthesized using a reverse micelle technique combined with metal-alkoxide hydrolysis and condensation. The sizes and the morphologies of the erbium-doped SiO2 nanoparticles could be changed by varying the molar ratio of water to surfactant. The sizes and the morphologies of the erbium-doped SiO2 nanoparticles were examined by using a transmission electron microscope. The average size of synthesized erbium-doped SiO2 nanoparticles was approximately 20-25 nm and that of the erbium particles was 3-5 nm. The effects of the synthesis parameters, such as the molar ratio of water to surfactant, are discussed.

  17. Synthesis of visible light driven cobalt tailored Ag{sub 2}O/TiON nanophotocatalyst by reverse micelle processing for degradation of Eriochrome Black T

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Syed Tajammul, E-mail: dr_tajammul@yahoo.ca [Nano Science and Catalysis Div. National Centre For Physics, Quaid-i-Azam University Complex, Islamabad 4400 (Pakistan); Rashid [Nano Science and Catalysis Div. National Centre For Physics, Quaid-i-Azam University Complex, Islamabad 4400 (Pakistan); Department of Chemistry, Quaid-i-Azam University, Islamabad (Pakistan); Anjum, Dalaver [Imaging and Characterization Lab, Blg 3 L0/room 232, 4700, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia); Siddiqa, Asima [Nano Science and Catalysis Div. National Centre For Physics, Quaid-i-Azam University Complex, Islamabad 4400 (Pakistan); Badshah, Amin [Department of Chemistry, Quaid-i-Azam University, Islamabad (Pakistan)

    2013-02-15

    Graphical abstract: Cobalt tailored Ag{sub 2}O/TiON nanophotocatalyst is synthesized using reverse micelle technique and it showed extraordinary photocatalytic activity. Display Omitted Highlights: ► TiON/Ag{sub 2}O/Co nanophotocatalyst is synthesized using microemulsion technique. ► Low temperature anatase phase and outstanding photocatlytic activity is observed. ► Effect of temperature and inert atmosphere on materials phase is investigated. ► Homogeneous dopants distribution and oxygen vacancies are examined. ► Enhancement in surface area, quantum efficiency and optical properties is observed. -- Abstract: An ultra efficient cobalt tailored silver and nitrogen co-doped titania (TiON/Ag{sub 2}O/Co) visible nanophotocatalyst is successfully synthesized using modified reverse micelle processing. Composition, phase, distribution of dopants, functional group analysis, optical properties and morphology of synthesized materials are investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) based techniques and others. Charge states of titanium (Ti) and silver are explored through core-loss electron energy loss spectroscopy (EELS) analysis and X ray photoelectron spectroscopy (XPS). Our characterization results showed that the synthesized nanophotocatalyst consisted of anatase phased qausispherical nanoparticles that exhibited homogeneous distribution of dopants, large surface area, high quantum efficiency and enhanced optical properties. At lower content of doped Co ions, the TiON/Ag{sub 2}O responded with extraordinary photocatalytic properties. The cobalt tailored nanophotocatalyst showed remarkable activity against Eriochrome Black T (EBT). Moreover, comparative degradation behavior of EBT with TiON, Ag{sub 2}O/TiON and Co/Ag{sub 2}O/TiON is also investigated.

  18. Synthesis of visible light driven cobalt tailored Ag2O/TiON nanophotocatalyst by reverse micelle processing for degradation of Eriochrome Black T

    International Nuclear Information System (INIS)

    Graphical abstract: Cobalt tailored Ag2O/TiON nanophotocatalyst is synthesized using reverse micelle technique and it showed extraordinary photocatalytic activity. Display Omitted Highlights: ► TiON/Ag2O/Co nanophotocatalyst is synthesized using microemulsion technique. ► Low temperature anatase phase and outstanding photocatlytic activity is observed. ► Effect of temperature and inert atmosphere on materials phase is investigated. ► Homogeneous dopants distribution and oxygen vacancies are examined. ► Enhancement in surface area, quantum efficiency and optical properties is observed. -- Abstract: An ultra efficient cobalt tailored silver and nitrogen co-doped titania (TiON/Ag2O/Co) visible nanophotocatalyst is successfully synthesized using modified reverse micelle processing. Composition, phase, distribution of dopants, functional group analysis, optical properties and morphology of synthesized materials are investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) based techniques and others. Charge states of titanium (Ti) and silver are explored through core-loss electron energy loss spectroscopy (EELS) analysis and X ray photoelectron spectroscopy (XPS). Our characterization results showed that the synthesized nanophotocatalyst consisted of anatase phased qausispherical nanoparticles that exhibited homogeneous distribution of dopants, large surface area, high quantum efficiency and enhanced optical properties. At lower content of doped Co ions, the TiON/Ag2O responded with extraordinary photocatalytic properties. The cobalt tailored nanophotocatalyst showed remarkable activity against Eriochrome Black T (EBT). Moreover, comparative degradation behavior of EBT with TiON, Ag2O/TiON and Co/Ag2O/TiON is also investigated.

  19. The impact of the confinement of reactants on the metal distribution in bimetallic nanoparticles synthesized in reverse micelles

    Directory of Open Access Journals (Sweden)

    Concha Tojo

    2014-11-01

    Full Text Available A kinetic study on the formation of bimetallic nanoparticles in microemulsions was carried out by computer simulation. A comprehensive analysis of the resulting nanostructures was performed regarding the influence of intermicellar exchange on reactivity. The objects of this study were metals having a difference in standard reduction potential of about 0.2–0.3 V. Relatively flexible microemulsions were employed and the concentration of the reactants was kept constant, while the reaction rate of each metal was monitored as a function of time using different reactant proportions. It was demonstrated that the reaction rates depend not only on the chemical reduction rate, but also on the intermicellar exchange rate. Furthermore, intermicellar exchange causes the accumulation of slower precursors inside the micelles, which favors chemical reduction. As a consequence, slower reduction rates strongly correlate with the number of reactants in this confined media. On the contrary, faster reduction rates are limited by the intermicellar exchange rate and not the number of reactants inside the micelles. As a result, different precursor proportions lead to different sequences of metal reduction, and thus the arrangement of the two metals in the nanostructure can be manipulated.

  20. Micelles Hydrodynamics

    CERN Document Server

    Svintradze, David V

    2016-01-01

    A micelle consists of monolayer of lipid molecules containing hydrophilic head and hydrophobic tail. These amphiphilic molecules in aqueous environment aggregate spontaneously into monomolecular layer held together due to hydrophobic effect by weak non-covalent forces. Micelles are flexible surfaces that show variety of shapes of different topology, but remarkably in mechanical equilibrium conditions they are spherical in shape. The shape and size of a micelle are functions of many variables such as lipid concentration, temperature, ionic strength, etc. Addressing the question, why the shape of micelles is sphere in mechanical equilibrium conditions, analytically proved to be a difficult problem. In the following paper we offer the shortest and elegant analytical proof of micelles spheroidal nature when they are thermodynamically equilibrated with solvent. The formalism presented in this paper can be readily extended to any homogenous surfaces, such are vesicles and membranes.

  1. Fine-tuning of catalytic tin nanoparticles by the reverse micelle method for direct deposition of silicon nanowires by a plasma-enhanced chemical vapour technique.

    Science.gov (United States)

    Poinern, Gérrard E J; Ng, Yan-Jing; Fawcett, Derek

    2010-12-15

    The reverse micelle method was used for the reduction of a tin (Sn) salt solution to produce metallic Sn nanoparticles ranging from 85 nm to 140 nm in diameter. The reverse micellar system used in this process was hexane-butanol-cetyl trimethylammonium bromide (CTAB). The diameters of the Sn nanoparticles were proportional to the concentration of the aqueous Sn salt solution. Thus, the size of the Sn nanoparticles can easily be controlled, enabling a simple, reproducible mechanism for the growth of silicon nanowires (SiNWs) using plasma-enhanced chemical vapour deposition (PECVD). Both the Sn nanoparticles and silicon nanowires were characterised using field-emission scanning electron microscopy (FE-SEM). Further characterisations of the SiNW's were made using transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman spectroscopy. In addition, dynamic light scattering (DLS) was used to investigate particle size distributions. This procedure demonstrates an economical route for manufacturing reproducible silicon nanowires using fine-tuned Sn nanoparticles for possible solar cell applications. PMID:20887996

  2. Structural, optical and crystal field analyses of undoped and Mn{sup 2+}-doped ZnS nanoparticles synthesized via reverse micelle route

    Energy Technology Data Exchange (ETDEWEB)

    Krsmanović Whiffen, R.M., E-mail: radenka@vinca.rs [Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, Belgrade 11001 (Serbia); Jovanović, D.J.; Antić, Ž. [Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, Belgrade 11001 (Serbia); Bártová, B. [LSME and CIME, École Polytechnique Fédérale de Lausanne, Station 12, Lausanne CH-101 (Switzerland); Milivojević, D.; Dramićanin, M.D. [Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, Belgrade 11001 (Serbia); Brik, M.G. [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia)

    2014-02-15

    Zinc sulfide, both as a bulk material and in nanocrystalline form, is a valuable luminescent material with important applications. Doped ZnS nanoparticles of around 5 nm are the material of choice for optoelectronic applications running in the UV region owing to their significant quantum size effect. This paper concerns detailed structural, spectroscopic and crystal field studies of ZnS nanoparticles, both pure and doped with Mn{sup 2+} ions, successfully synthesized at room temperature using a simple reverse micelle technique in the Triton X-100/cyclohexane medium. The resulting ZnS sphalerite phase small-size nanoparticles (3–5 nm) have a much larger energy band gap (∼4.7 eV) than that reported for the bulk ZnS (3.6 eV), thus confirming a pronounced quantum confinement effect. The electron paramagnetic resonance data provided evidence for the existence of two distinct environments for Mn{sup 2+} ions: the interior (core) and near the surface of the nanoparticles. The presence of an Mn{sup 2+}-characteristic orange emission centered at 600 nm confirmed that our samples were properly doped with Mn{sup 2+} ions, as the {sup 4}T{sub 1}→{sup 6}A{sub 1} radiation transition could arise only on the basis of Mn{sup 2+} ions incorporated into the ZnS nanoparticles. To the best of our knowledge, our finding include the longest decay time component for the orange emission ever observed, timed at about 3.3 ms. The experimental excitation spectra were analyzed and the transitions assigned using the exchange charge model of theory of crystal field, which allowed to calculate the energy level scheme of the Mn{sup 2+} ions. The results presented in this paper provide us with detailed information about the ZnS sphalerite nanocrystals studied and can be readily applied to other similar systems. -- Highlights: • 3–5 nm ZnS and ZnS:Mn{sup 2+} NPs synthesized at RT via reverse micelle synthesis. • Pronounced Quantum Confinement effect: E{sub g} (NPs)=4.7 eV>E{sub g} (bulk

  3. Structural, optical and crystal field analyses of undoped and Mn2+-doped ZnS nanoparticles synthesized via reverse micelle route

    International Nuclear Information System (INIS)

    Zinc sulfide, both as a bulk material and in nanocrystalline form, is a valuable luminescent material with important applications. Doped ZnS nanoparticles of around 5 nm are the material of choice for optoelectronic applications running in the UV region owing to their significant quantum size effect. This paper concerns detailed structural, spectroscopic and crystal field studies of ZnS nanoparticles, both pure and doped with Mn2+ ions, successfully synthesized at room temperature using a simple reverse micelle technique in the Triton X-100/cyclohexane medium. The resulting ZnS sphalerite phase small-size nanoparticles (3–5 nm) have a much larger energy band gap (∼4.7 eV) than that reported for the bulk ZnS (3.6 eV), thus confirming a pronounced quantum confinement effect. The electron paramagnetic resonance data provided evidence for the existence of two distinct environments for Mn2+ ions: the interior (core) and near the surface of the nanoparticles. The presence of an Mn2+-characteristic orange emission centered at 600 nm confirmed that our samples were properly doped with Mn2+ ions, as the 4T1→6A1 radiation transition could arise only on the basis of Mn2+ ions incorporated into the ZnS nanoparticles. To the best of our knowledge, our finding include the longest decay time component for the orange emission ever observed, timed at about 3.3 ms. The experimental excitation spectra were analyzed and the transitions assigned using the exchange charge model of theory of crystal field, which allowed to calculate the energy level scheme of the Mn2+ ions. The results presented in this paper provide us with detailed information about the ZnS sphalerite nanocrystals studied and can be readily applied to other similar systems. -- Highlights: • 3–5 nm ZnS and ZnS:Mn2+ NPs synthesized at RT via reverse micelle synthesis. • Pronounced Quantum Confinement effect: Eg (NPs)=4.7 eV>Eg (bulk)=3.6 eV. • Estimated distribution of the Mn2+ ions throughout the Zn

  4. Interactions between crystal violet and AOT in aqueous solutions and in AOT/isooctane/water microemulsions

    Institute of Scientific and Technical Information of China (English)

    HAO Xiaojuan; AN Xueqin; CHEN Zhiyun; SHEN Weiguo

    2004-01-01

    The absorbance of crystal violet (CV) in a series of aqueous solutions and a series of sodium bis(2-ethyl- hexyl) sulfosuccinate (AOT)/isooctane/water microemulsions has been determined. Association models have been used to analyse the experimental data to obtain the association constants of CV and AOT in the above two media. It was found that about up to 57% CV was associated by AOT in AOT/ isooctane/water microemulsions, which reduced the reaction rate of alkaline fading of crystal violet in the microemulsions.

  5. Synthesis of visible light driven cobalt tailored Ag2O/TiON nanophotocatalyst by reverse micelle processing for degradation of Eriochrome Black T

    KAUST Repository

    Hussain, Syed Tajammul

    2013-02-01

    An ultra efficient cobalt tailored silver and nitrogen co-doped titania (TiON/Ag2O/Co) visible nanophotocatalyst is successfully synthesized using modified reverse micelle processing. Composition, phase, distribution of dopants, functional group analysis, optical properties and morphology of synthesized materials are investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) based techniques and others. Charge states of titanium (Ti) and silver are explored through core-loss electron energy loss spectroscopy (EELS) analysis and X ray photoelectron spectroscopy (XPS). Our characterization results showed that the synthesized nanophotocatalyst consisted of anatase phased qausispherical nanoparticles that exhibited homogeneous distribution of dopants, large surface area, high quantum efficiency and enhanced optical properties. At lower content of doped Co ions, the TiON/Ag2O responded with extraordinary photocatalytic properties. The cobalt tailored nanophotocatalyst showed remarkable activity against Eriochrome Black T (EBT). Moreover, comparative degradation behavior of EBT with TiON, Ag2O/TiON and Co/Ag2O/TiON is also investigated. © 2012 Elsevier Ltd.

  6. Mechanism study of PEGylated polyester and β-cyclodextrin integrated micelles on drug resistance reversal in MRP1-overexpressed HL60/ADR cells.

    Science.gov (United States)

    Ji, Qian; Qiu, Liyan

    2016-08-01

    Chemotherapy is one of the main strategies for cancer treatment, but its effective application is seriously limited by the development of drug resistance. In this study, we designed micellar vectors for doxorubicin based on amphiphilic copolymers sequentially linking β-cyclodextrin (β-CD), polylacticacid (PLA) or polycaprolactone (PCL) block, and polyethylene glycol (PEG) block to overcome drug resistance in human acute myeloid leukemia cells (HL60/ADR) overexpressing multidrug resistance protein 1 (MRP1). The significant enhancement in cytotoxicity and inhibited HL60/ADR tumor growth in mouse was achieved. More importantly, several analyses were performed to understand the interactions between various polymers and MRP1 at the cellular level. The results showed that the polymers did not show remarkable correlation of MRP1 gene and protein expression, but could decrease intracellular ATP, mitochondrial membrane potential and glutathione levels, which was greatly dependent on the molecular structure of polymers. In conclusion, these novel micelles can be considered as a kind of promising drug delivery system for tumor therapy to reverse drug resistance related to MRP1 overexpression. PMID:27088190

  7. Synthesis of zinc substituted cobalt ferrites via reverse micelle technique involving in situ template formation: A study on their structural, magnetic, optical and catalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Charanjit; Jauhar, Sheenu [Department of Chemistry, Panjab University, Chandigarh 160014 (India); Kumar, Vinod [ICON Analytical Equipment (P) Ltd., Mumbai 400018 (India); Singh, Jagdish [Institute Instrumentation Centre, Indian Institute of Technology–Roorkee (India); Singhal, Sonal, E-mail: sonal1174@gmail.com [Department of Chemistry, Panjab University, Chandigarh 160014 (India)

    2015-04-15

    Nano-crystalline particles of visible light responsive Zn–Co ferrites having formula Zn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were successfully synthesized via reverse micelle technique. Sodium dodecyl sulfate was used as a surfactant/templating agent. The ferrite formation was confirmed using powder X-Ray Diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy. The spherical shape of the ferrite particles was established by High Resolution Transmission Electron Microscope (HR-TEM) analysis. From the magnetic studies, the ferromagnetic nature of CoFe{sub 2}O{sub 4} was known. However, the nano-particles exhibited a transition from ferromagnetic to super-paramagnetic upon increasing the zinc concentration. In addition, the photo-Fenton activity of ferrites was also studied by carrying out degradation of Rhodamine B (RhB) dye under visible light irradiation. The catalytic activity increased with increase in zinc ion concentration. - Highlights: • Controlled dimensions of Zn–Co ferrite nanoparticles by microemulsion technique. • Spherical shape with uniform size distribution of ∼5 nm was achieved. • Significant shift from ferromagnetic to superparamagnetic with Zn{sup 2+} ion doping. • Improved photocatalytic activity with Zn{sup 2+} ion doping.

  8. Nanoscale Control Over Interfacial Properties in Mixed Reverse Micelles Formulated by Using Sodium 1,4-bis-2-ethylhexylsulfosuccinate and Tri-n-octyl Phosphine Oxide Surfactants.

    Science.gov (United States)

    Odella, Emmanuel; Falcone, R Darío; Silber, Juana J; Correa, N Mariano

    2016-08-01

    The interfacial properties of pure reverse micelles (RMs) are a consequence of the magnitude and nature of noncovalent interactions between confined water and the surfactant polar head. Addition of a second surfactant to form mixed RMs is expected to influence these interactions and thus affect these properties at the nanoscale level. Herein, pure and mixed RMs stabilized by sodium 1,4-bis-2-ethylhexylsulfosuccinate and tri-n-octyl phosphine oxide (TOPO) surfactants in n-heptane were formulated and studied by varying both the water content and the TOPO mole fraction. The microenvironment generated was sensed by following the solvatochromic behavior of the 1-methyl-8-oxyquinolinium betaine probe and (31) P NMR spectroscopy. The results reveal unique properties of mixed RMs and we give experimental evidence that free water can be detected in the polar core of the mixed RMs at very low water content. We anticipate that these findings will have an impact on the use of such media as nanoreactors for many types of chemical reactions, such as enzymatic reactions and nanoparticle synthesis. PMID:27128745

  9. Synthesis and characterization of aspartic acid-capped CdS/ZnS quantum dots in reverse micelles and its application to Hg(II) determination

    International Nuclear Information System (INIS)

    In this work, CdS/ZnS quantum dots (QDs) coated with aspartic acid (AsA) were synthesized in reverse micelles. The synthesized QDs were characterized by XRD, TEM, IR and photoluminescence (PL) spectroscopy. It was found that the intensity of CdS/ZnS QDs coated with AsA is much greater than CdS, and CdS/ZnS QDs. The interaction of some heavy metal ions with CdS/ZnS/AsA QDs was investigated at different buffering pH media. Based on the PL quenching of the QDs in the presence of each one of the metal ions, the feasibility of their determinations was examined according to the Stern–Volmer equation. The investigations showed that Hg(II) ions can be easily determined in contaminated atmospheric environments with the detection limit of 0.05 mg m−3. The results were satisfactorily confirmed by cold vapor atomic absorption spectrometric method. - Highlights: • A new CdS/ZnS quantum dot capped with aspartic acid (DDBA) was prepared. • The prepared QDs benefit from a favorable fluorescence. • Interaction of some metal ions with the QDs was examined according to the Stern–Volmer equation. • The determination of Hg(II) is feasible in the present of many co-existence metal ions. • The method benefits from a high-speed and considerable simplicity for Hg(II) determination

  10. Use of a partial filling technique and reverse migrating micelles in the study of N-methylcarbamate pesticides by micellar electrokinetic chromatography-electrospray ionization mass spectrometry.

    Science.gov (United States)

    Molina, M; Wiedmer, S K; Jussila, M; Silva, M; Riekkola, M L

    2001-08-24

    This study describes three ways to couple micellar electrokinetic chromatography (MEKC) on-line with electrospray ionization mass spectrometry (ESI-MS) for the analysis of N-methylcarbamate pesticides. The methods involved the use of a partial filling (PF) technique under basic conditions and the use of reverse migrating micelles (RMMs) under acidic and basic conditions. The use of RMMs in basic electrolyte solutions required coated capillaries with low electroosmotic flows, and capillaries coated with anionic poly(sodium 2-acrylamide-2-methylpropanesulfonate) were selected for the purpose. Before the on-line MEKC-ESI-MS coupling, the MEKC and MS conditions were separately optimized under off-line conditions. The methods were compared in terms of detection limits and the stability of the electrospray process. The PF method offered good separation but poorer stability of the electrospray relative to the other methods. A more stable electrospray performance was obtained with use of RMMs in acidic electrolyte solutions, but some of the analytes were protonated and could not be detected due to the increase in their retention factors. However, with the use of anionic polymer-coated capillaries and RMMs at pH 8.5, all analytes were successfully separated. The high-salt stacking method was applied to improve the sensitivity of MEKC-ESI-MS and the detection limits were in the range of 0.04-2.0 microg/ml. PMID:11572389

  11. Characterization of oxidation resistant Fe@M (M=Cr, Ni) core@shell nanoparticles prepared by a modified reverse micelle reaction

    Science.gov (United States)

    Naik, Sweta H.; Carroll, Kyler J.; Carpenter, Everett E.

    2011-04-01

    Iron-based nanoparticles are the forerunners in the field of nanotechnology due to their high magnetization saturation and biocompability which affords them use in a variety of applications. However, iron-based nanoparticles, due to a high surface-to-volume ratio, suffer from oxidation and limit its practicality by lowering the magnetic moment significantly. To avoid this oxidation, the surfaces of the particles have to be passivated. One such way to accomplish this passivation is to synthesize core@shell nanoparticles that have a surface treatment of chromium or nickel. These core@shell nanoparticles have been synthesized using a reverse micelle technique. The Cr and Ni passivated iron nanoparticles were characterized by x-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and x-ray photoelectron spectroscopy to determine their phase, morphology, surface properties, and magnetization saturation. A high magnetization saturation of 160 and 165 emu/g for Cr and Ni passivated iron core@shell nanoparticles was achieved.

  12. Synthesis and characterization of surface-enhanced Raman scattering tags with Ag/SiO2 core-shell nanostructures using reverse micelle technology.

    Science.gov (United States)

    Gong, Ji-Lai; Jiang, Jian-Hui; Liang, Yi; Shen, Guo-Li; Yu, Ru-Qin

    2006-06-15

    A novel simplified method for synthesis of surface-enhanced Raman scattering tags has been reported. This synthesis method is based on reverse micelle technique using Igepal CO-520 as a surfactant and the mixed solution of silver nitrate and rhodamine dyes with isothiocyanate group as water pool followed by hydrazine hydrate reduction and TEOS polymerization leading to the formation of silica layer surrounding the silver core. Compared to the method reported in literature, the proposed methodology eliminates the necessity of vitrophilic pretreatment and makes it possible to complete all different processes including the preparation of silver nanoparticles, the conjugation of dye molecules and the formation of silica shell in the microreactor. The nanoparticle-based surface-enhanced Raman tags obtained are composed of silver core conjugated with rhodamine dyes and an encasing silica shell. Both the dyes themselves and the Ag/SiO2 core-shell nanoparticles without the encapsulation of dyes exhibit no Raman signals. However, the Ag/SiO2 core-shell nanoparticles exhibit strong Raman signals when encapsulated with these dyes. This is due to the appearance of fluorescence quenching and surface-enhanced Raman scattering effect resulting from the conjugation of dyes and silver core. The Raman tags were characterized using transmission electron microscopy (TEM), UV-visible absorption spectrometry, and Raman spectrometry. PMID:16457836

  13. Reverse Micelle Formation of Triton X-100 in Butanol and n-Heptane Mixed Solvents Studied by the Positron Annihilation Technique

    Science.gov (United States)

    Das; Ganguly

    1997-08-01

    The positron annihilation technique (PAT) has been applied to study the molecular association phenomenon of Triton X-100 (TX-100) and formation of reversed micelles in the mixed solvent of butanol and n-heptane. The results indicate the sensitivity of positronium (Ps) parameters to the phase transition region due to the self-aggregation phenomenon of TX-100 within the system. The intensity of the long-lived ortho-Ps component, I3, and its lifetime, tau3, show a remarkable change at a critical concentration of the surfactant at approximately 1.5 mM coined as the operational CMC of TX-100 in both (1:1) and (1:2) butanol-n-heptane (BuHp) systems. The narrow component/para-Ps intensity as computed from Doppler broadening of annihilation radiation indicates discernable changes at the same concentration region ( approximately 1.5 mM) of TX-100 in the system. Further, microphase changes due to the association of water molecules within the nonaqueous phase has been studied by Ps parameters, which reveals a clear demarcation of the polar and nonpolar zones. PMID:9268557

  14. On the formation of new reverse micelles: a comparative study of benzene/surfactants/ionic liquids systems using UV-visible absorption spectroscopy and dynamic light scattering.

    Science.gov (United States)

    Falcone, R Darío; Correa, N Mariano; Silber, Juana J

    2009-09-15

    The microenvironment of the polar core generated in different ionic liquid reverse micelle (IL RM) systems were investigated using the solvatochromic behavior of 1-methyl-8-oxyquinolinium betaine (QB) as an absorption probe and dynamic light scattering (DLS) technique. The novel RM systems consist of two different ILs--1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (bmimTf2N)--sequestrated by two different surfactants--Triton X-100 (TX-100) and benzyl-n-hexadecyldimethylammonium chloride (BHDC)--in order to make IL/surfactant/benzene RMs. The effect of the variation of Ws (Ws=[IL]/[surfactant]) on the QB spectroscopy was used to characterize these nonaqueous RMs. DLS results confirm the formation of these IL RM systems because increasing Ws increases the droplet sizes. Moreover it is demonstrated that the structure of the sequestrated ILs depends strongly on the type of surfactant use to create the RMs. PMID:19678620

  15. Synthesis of zinc substituted cobalt ferrites via reverse micelle technique involving in situ template formation: A study on their structural, magnetic, optical and catalytic properties

    International Nuclear Information System (INIS)

    Nano-crystalline particles of visible light responsive Zn–Co ferrites having formula ZnxCo1-xFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were successfully synthesized via reverse micelle technique. Sodium dodecyl sulfate was used as a surfactant/templating agent. The ferrite formation was confirmed using powder X-Ray Diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy. The spherical shape of the ferrite particles was established by High Resolution Transmission Electron Microscope (HR-TEM) analysis. From the magnetic studies, the ferromagnetic nature of CoFe2O4 was known. However, the nano-particles exhibited a transition from ferromagnetic to super-paramagnetic upon increasing the zinc concentration. In addition, the photo-Fenton activity of ferrites was also studied by carrying out degradation of Rhodamine B (RhB) dye under visible light irradiation. The catalytic activity increased with increase in zinc ion concentration. - Highlights: • Controlled dimensions of Zn–Co ferrite nanoparticles by microemulsion technique. • Spherical shape with uniform size distribution of ∼5 nm was achieved. • Significant shift from ferromagnetic to superparamagnetic with Zn2+ ion doping. • Improved photocatalytic activity with Zn2+ ion doping

  16. Synthesis and characterization of aspartic acid-capped CdS/ZnS quantum dots in reverse micelles and its application to Hg(II) determination

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Mohammad Saeid, E-mail: mshosseini1336@yahoo.com; Kamali, Mohsen

    2015-11-15

    In this work, CdS/ZnS quantum dots (QDs) coated with aspartic acid (AsA) were synthesized in reverse micelles. The synthesized QDs were characterized by XRD, TEM, IR and photoluminescence (PL) spectroscopy. It was found that the intensity of CdS/ZnS QDs coated with AsA is much greater than CdS, and CdS/ZnS QDs. The interaction of some heavy metal ions with CdS/ZnS/AsA QDs was investigated at different buffering pH media. Based on the PL quenching of the QDs in the presence of each one of the metal ions, the feasibility of their determinations was examined according to the Stern–Volmer equation. The investigations showed that Hg(II) ions can be easily determined in contaminated atmospheric environments with the detection limit of 0.05 mg m{sup −3}. The results were satisfactorily confirmed by cold vapor atomic absorption spectrometric method. - Highlights: • A new CdS/ZnS quantum dot capped with aspartic acid (DDBA) was prepared. • The prepared QDs benefit from a favorable fluorescence. • Interaction of some metal ions with the QDs was examined according to the Stern–Volmer equation. • The determination of Hg(II) is feasible in the present of many co-existence metal ions. • The method benefits from a high-speed and considerable simplicity for Hg(II) determination.

  17. Functional BaTiO{sub 3} nanostructures immobilized onto si-based substrates using sol–gel and reverse micelle techniques

    Energy Technology Data Exchange (ETDEWEB)

    Mamana, Nadia, E-mail: nadia@fceia.unr.edu.ar; Pellegri, Nora [CONICET, FCEIyA, UNR, Laboratorio de Materiales Cerámicos IFIR (Argentina)

    2015-03-15

    The current tendency toward miniaturization of electronic devices has driven the interest in developing ferroelectric materials in low dimensions. In this work, for the preparation of lead-free BaTiO{sub 3} nanoparticles, we used a combination of the sol–gel method with the reverse micelles techniques. Moreover, previously to the thermal treatment, it was necessary to remove the surfactant. For this stage, oleic acid was used to stabilize the nanoparticles in the solution. Then, nanometer-sized particles were deposited on different substrates (Si, Pt/TiO{sub 2}/SiO{sub 2}/Si). The influence of different modes of deposition on particle size, degree of agglomeration, was analyzed. The mean particle size was 10 nm. Finally, the deposition of BaTiO{sub 3} particles on a conductive substrate such as the wafer of platinum (Pt/TiO{sub 2}/SiO{sub 2}/Si) was confirmed by several AFM techniques.

  18. Synthesis of MSnO{sub 3} (M = Ba, Sr) nanoparticles by reverse micelle method and particle size distribution analysis by whole powder pattern modeling

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Jahangeer; Blakely, Colin K.; Bruno, Shaun R. [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Poltavets, Viktor V., E-mail: poltavets@chemistry.msu.edu [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States)

    2012-09-15

    Highlights: ► BaSnO{sub 3} and SrSnO{sub 3} nanoparticles synthesized using the reverse micelle method. ► Particle size and size distribution studied by whole powder pattern modeling. ► Nanoparticles are of optimal size for investigation in dye-sensitized solar cells. -- Abstract: Light-to-electricity conversion efficiency in dye-sensitized solar cells critically depends not only on the dye molecule, semiconducting material and redox shuttle selection but also on the particle size and particle size distribution of the semiconducting photoanode. In this study, nanocrystalline BaSnO{sub 3} and SrSnO{sub 3} particles have been synthesized using the microemulsion method. Particle size distribution was studied by whole powder pattern modeling which confirmed narrow particle size distribution with an average size of 18.4 ± 8.3 nm for SrSnO{sub 3} and 15.8 ± 4.2 nm for BaSnO{sub 3}. These values are in close agreement with results of transmission electron microscopy. The prepared materials have optimal microstructure for successive investigation in dye-sensitized solar cells.

  19. On-line concentration of neutral analytes for micellar electrokinetic chromatography. 3. Stacking with reverse migrating micelles.

    Science.gov (United States)

    Quirino, J P; Terabe, S

    1998-01-01

    On-line concentration of neutral analytes by sample stacking in reversed migration micellar electrokinetic chromatography is presented. Micellar separation solutions of sodium dodecyl sulfate are prepared with acidic buffers to reverse the direction of the migration velocity of neutral analytes owing to a reduced electroosmotic flow. Samples are prepared in nonmicellar matrixes of low conductivity (i.e., water, diluted buffer, or dilute organic/aqueous solvent) to achieve field enhancement in the sample zone. Without polarity switching inherent in large-volume sample stacking, narrowing of analyte bands, removal of sample matrix, and separation of focused analyte bands are achieved. A model is proposed to describe the stacking technique and is supported by experimental results. In addition, equations are derived to describe band broadening associated with the technique. Detector response improvements reaching a 100-fold are confirmed experimentally. Concentration detection limits on the order of low-ppb levels (S/N = 3) are realized with model steroidal compounds. PMID:21644608

  20. Sugar-based gemini surfactant with a vesicle-to-micelle transition at acidic pH and a reversible vesicle flocculation near neutral pH

    NARCIS (Netherlands)

    Johnsson, M; Wagenaar, A; Engberts, JBFN

    2003-01-01

    A sugar-based (reduced glucose) gemini surfactant forms vesicles in dilute aqueous solution near neutral pH. At lower pH, there is a vesicle-to-micelle transition within a narrow pH region (pH 6.0-5.6). The vesicles are transformed into large cylindrical micelles that in turn are transformed into sm

  1. Physicochemical investigation of biocompatible mixed surfactant reverse micelles: II. Dynamics of conductance percolation, energetics of droplet clustering, effect of additives and dynamic light scattering studies

    International Nuclear Information System (INIS)

    Graphical abstract: Tp/°C: Threshold temperature of percolation; ω: molar ratio of water to surfactant; IPM: isopropyl myristate; EO: ethyl oleate; IPP: isopropyl palmitate. Highlights: • Percolation temperature depends on contents of water, nonionic surfactant and [NaCl]. • Acetyl modified amino acids retard the temperature-induced percolation process. • The clustering process is spontaneous, endothermic and entropically driven. • Enthalpy and entropy of clustering process increase with increasing nonionic content. • Chemical structures of oils influence thermodynamic parameters of droplet clustering. -- Abstract: Temperature-induced percolation behavior in mixed reverse micellar systems (RMs) comprising sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and polyoxyethylene(20) sorbitan trioleate (Tween-85) in polar lipophilic oils e.g., ethyl oleate (EO), isopropyl myristate (IPM) and isopropyl palmitate (IPP) was studied at a total surfactant concentration (ST) of 0.25 ⋅ 103 mol ⋅ m−3 in absence and presence of the additives (acetyl modified amino acids (MAA) of different chemical structures). The threshold temperature of percolation (Tp) of these systems was found to be dependent on water content (ω), content of nonionic surfactant (XTween-85), and concentration of NaCl. The standard free energy change (ΔGcl0), enthalpy change (ΔHcl0) and entropy change (ΔScl0) of cluster formation were evaluated based on an association model at different physicochemical environments. The clustering process was spontaneous and found to be endothermic and entropically driven. Scaling laws for the temperature-induced percolation demonstrated dynamic nature of the percolation process. The activation energy, Ep of these systems was estimated both in absence and presence of additives. Droplet sizes of these systems were measured using dynamic light scattering (DLS) technique at different physicochemical environments (comparable to conductivity measurements) to

  2. Membrane lipid regulation in Acholeplasma laidlawii grown with saturated fatty acids. Biosynthesis of a triacylglucolipid forming reversed micelles.

    Science.gov (United States)

    Lindblom, G; Hauksson, J B; Rilfors, L; Bergenståhl, B; Wieslander, A; Eriksson, P O

    1993-08-01

    The membrane lipid composition in several strains of Acholeplasma laidlawii is regulated upon a change in the growth conditions. Monoglucosyldiacylglycerol (MGlcDAG) and diglucosyldiacylglycerol (DGlcDAG) are the most abundant lipids in the A. laidlawii membrane. A third glucolipid, 3-O-acyl-monoglucosyldiacylglycerol (MAMGlcDAG) is synthesized by strain A-EF22 when the membrane lipids contain large amounts of saturated acyl chains. The lipid regulation can be understood from a simple theoretical model, in which the cells strive to maintain a balance between the lipids constituting a bilayer and those forming reversed non-lamellar liquid crystalline phases. Thus, the physical chemistry of membrane lipids, in particular their ability to form different aggregate structures, constitutes the basis for the lipid regulation, and therefore an understanding of the phase equilibria of membrane lipids is crucial. MGlcDAG and MAMGlcDAG isolated from A. laidlawii strain A-EF22 membranes were studied mainly by 2H NMR, 1H NMR, and 1H NMR diffusion measurements. MAMGlcDAG, containing 96 mol % saturated acyl chains formed a gel/crystalline phase up to about 80 degrees C, where a transition occurred to a reversed micellar (L2) phase. This is an unexpected finding for a membrane lipid. However, this lipid homogeneously mixes with the other membrane lipids at physiological temperatures. Previous and new data on MGlcDAG show that the lamellar phase is stabilized when the length and the degree of unsaturation of the acyl chains are decreased. The physicochemical properties of MAMGlcDAG and MGlcDAG were compared and found to be of great significance for the physiological regulation of the lipids in the membrane. MAMGlcDAG is synthesized under conditions when the phase equilibria of MGlcDAG are shifted from a non-lamellar toward a lamellar phase. Apart from MAMGlcDAG, MGlcDAG is the major lipid in A. laidlawii strain A-EF22 which is able to form reversed aggregate structures. MAMGlc

  3. Correlation between AERONET AOT and VIIRS EDR AOT: A new EDR cell

    Science.gov (United States)

    Molinie, J.; Henry, J. L.; Clement, J.; Euphrasie-Clotilde, L.; Brute, F. N.

    2015-12-01

    Every year, a huge mass of desert dusts lifted from Saharan and sub Saharan regions is injected over the Atlantic Ocean and bring to the Caribbean and the American continent. Guadeloupe a West Indies island, is affected by the presence of dusts particles which impact the air quality and acts on human health. The effect produced by the particles in the atmosphere can be observed by satellite. VIIRS is one the latest tools provided by NASA, to help scientific community to have a better understanding of aerosol behavior. In this job we try to found a link between ground measurement AOT and VIIRS data.In Guadeloupe, AOT measurements have been performed with sun photometer of AERONET network. We calculated AOT at 500 nm mean daily sun photometer data in order to compare them with AOT EDR 550 data computed by NOAA Aerosol calibration and validation team. Three AOT EDR cells, located over the ocean and close to the East coast of the island of have been chosen to evaluate the correlation between ground and satellite data. We obtained using data performed from May to December 2012, correlation coefficient range between 0.8 and 0.87. We observed numerous AOT EDR 550 have been computed with a number of IP pixel, nAOT very low. We proposed to used only cases with nAOT equal or higher than 10. The correlation coefficients improved and reached 0.9. However, those good results have been obtained with a day number reduced by almost 50 per cent.In order to keep a good correlation and a higher number of day we rebuilt a cell by merging two cells. We obtained a new cell with an AOT EDR value equal to the mean AOT EDR of the two parents' value and a nAOT the sum of the previous nAOTs. The results with the new nAOT equal of higher than 10 is, r =0.91 and we keep 75 per cent of the cases.

  4. FT-IR studies on the conformation and effective head-group area of AOT molecules in W/O microemulsions

    Institute of Scientific and Technical Information of China (English)

    周国伟; 鲍猛; 李干佐; 陈文君

    2002-01-01

    Using Fourier transform infrared(FT-IR) spectroscopy technique, the carbonyl stretching vibration bands of AOT in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water reverse (W/O) microemulsions system have been investigated by least square curve fitting. The results indicate that an asymmetric adsorbed peak of carbonyl stretching vibration of AOT molecule is situated in (1739 ± 1) and (1725 ± 2) cm-1. The two peaks correspond to different carbonyls in gauche conformation and trans conformation of AOT molecules, respectively. With different water contents (W0), the variations of peak intensity ratio (/= l1739/l1725) reflect the change of the ratio for the two conformation populations and the variations of the effective head-group area of AOT molecule have relations to the ratio of two conformation populations.

  5. Encapsulation of biomolecules for bioanalytical purposes: Preparation of diclofenac antibody-doped nanometer-sized silica particles by reverse micelle and sol-gel processing

    International Nuclear Information System (INIS)

    In recent years, the sol-gel technique has attracted increasing interest as a unique approach to immobilize biomolecules for bioanalytical applications as well as biochemical and biophysical studies. For this purpose, crushed biomolecule-doped sol-gel glass monoliths have been widely used. In the present work, for the first time, the encapsulation of anti-diclofenac antibodies in silica nanoparticles was carried out by a combination of reverse micelle and sol-gel technique. Cyclohexane was used for the preparation of the microemulsion as organic solvent, while surfactant Igepal CO-520 was found to be the optimal stabilizer. The antibody source was a purified IgG fraction originating from a polyclonal rabbit antiserum. Tetramethyl orthosilicate (TMOS) was used as precursor. Rather uniform, monodispersed and spherical silica particles of about 70 nm diameter size were fabricated, as was demonstrated by transmission electron microscopy (TEM) and scanning electron microscopy/energy dispersive X-ray fluorescence analysis (SEM/EDX). The biological activity of the encapsulated antibodies was evaluated by incubation of the nanoparticles with a diclofenac standard solution and analysis of the filtrate and followed washing solutions by a highly sensitive enzyme-linked immunosorbent assay (ELISA), using non-doped particles as blanks. While only about 6% of the added diclofenac was nonspecifically retained by the blank, the corresponding amount of about 66% was much higher with the antibody-doped particles. An obvious advantage of this approach is the general applicability of the developed technique for a mild immobilization of different antibody species

  6. Encapsulation of biomolecules for bioanalytical purposes: preparation of diclofenac antibody-doped nanometer-sized silica particles by reverse micelle and sol-gel processing.

    Science.gov (United States)

    Tsagkogeorgas, Fotios; Ochsenkühn-Petropoulou, Maria; Niessner, Reinhard; Knopp, Dietmar

    2006-07-28

    In recent years, the sol-gel technique has attracted increasing interest as a unique approach to immobilize biomolecules for bioanalytical applications as well as biochemical and biophysical studies. For this purpose, crushed biomolecule-doped sol-gel glass monoliths have been widely used. In the present work, for the first time, the encapsulation of anti-diclofenac antibodies in silica nanoparticles was carried out by a combination of reverse micelle and sol-gel technique. Cyclohexane was used for the preparation of the microemulsion as organic solvent, while surfactant Igepal CO-520 was found to be the optimal stabilizer. The antibody source was a purified IgG fraction originating from a polyclonal rabbit antiserum. Tetramethyl orthosilicate (TMOS) was used as precursor. Rather uniform, monodispersed and spherical silica particles of about 70nm diameter size were fabricated, as was demonstrated by transmission electron microscopy (TEM) and scanning electron microscopy/energy dispersive X-ray fluorescence analysis (SEM/EDX). The biological activity of the encapsulated antibodies was evaluated by incubation of the nanoparticles with a diclofenac standard solution and analysis of the filtrate and followed washing solutions by a highly sensitive enzyme-linked immunosorbent assay (ELISA), using non-doped particles as blanks. While only about 6% of the added diclofenac was nonspecifically retained by the blank, the corresponding amount of about 66% was much higher with the antibody-doped particles. An obvious advantage of this approach is the general applicability of the developed technique for a mild immobilization of different antibody species. PMID:17723516

  7. Investigation of the micropolarity in reverse micelles of nonionic poly(ethylene oxide) surfactants using 4-nitropyridine-N-oxide as absorption probe.

    Science.gov (United States)

    Bandula, Rodica; Vasilescu, Marilena; Lemmetyinen, Helge

    2005-07-15

    The micropolarities of the reverse micelle (RM) interior of nonionic poly(ethylene oxide) surfactants of the alkyl ether type (poly(ethylene oxide)[4] lauryl ether (C12E4, Brij 30)), alkyl-aryl ethers (poly(ethylene oxide)[4] nonylphenyl ether (C9PhiE4), poly(ethylene oxide)[5] nonylphenyl ether (C9PhiE5), and poly(ethylene oxide)[5] octylphenyl ether (C8PhiE5)), and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers (Pluronics P123, F127) were investigated as a function of the water content by applying the absorption probe technique, using 4-nitropyridine-N-oxide (NP) as a probe. The change in the micellar aggregate micropolarity in different solvents (cyclohexane, decane, n-butanol, and n-butyl acetate) at various water contents has been investigated. The research was focused on the determination of the effects of surfactant structure and solvent type on the hydration degrees of the PEO chains in the region at the core limit, where the NP probe was located. All results regarding the polarities in RM and PEO/water calibration mixtures have been expressed in terms of Kosower's Z values, using the linear dependence of E(NP) on Kosower's Z. The PPO/butanol mixtures have also been used for RM in butanol as a reference system. The data revealed that local polarity in RM is dependent on the surfactant type, block copolymer composition, solvent nature, and water content. At the same water content, the results clearly indicate a lower hydration degree of triblock copolymers, as compared to the surfactants of the alkyl ether and alkyl-aryl ether type, but for P123 and F127 Pluronics in n-butanol the hydration is higher owing to the behavior of butanol as cosurfactant and to its hydration. PMID:15925636

  8. Synthesis of an optically clear, flexible and stable hybrid ureasilicate matrix doped with CdSe nanoparticles produced by reverse micelles

    International Nuclear Information System (INIS)

    Optically clear and flexible organic–inorganic hybrid materials doped with CdSe nanoparticles (NPs) were synthesized by a sol–gel method based on the hydrolysis and condensation reactions of ureasilicate precursors. The CdSe NPs were produced by a colloidal method using reverse micelles and were then transferred to the ureasilicate precursor solution followed by gelation of the mixture using ammonia/water vapours as catalyst for the sol–gel process. The influence of the NPs surface in the dispersion of the NPs within the matrix was investigated by the addition of a capping agent with both thiol and siloxane groups (3-mercaptopropyltrimethoxysilane, MPTMS). This capping agent was used in order to improve compatibility and avoid aggregation of the NPs within the matrix and to increase the preservation of the original optical properties of the NPs. The nanocomposites obtained were characterized by absorption spectroscopy, steady-state photoluminescence, time resolved photoluminescence, HRTEM and FTIR spectroscopy. The results obtained showed the influence of the use of MPTMS in the preservation of the original optical properties of the CdSe NPs after their transfer into the ureasilicate matrix. The HRTEM analysis showed the presence of well-dispersed spherical NPs with well-defined lattice fringes. The obtained nanocomposites exhibit high transparency in the visible range as a result of the good dispersion of the NPs within the matrix, showing the potentials of the developed method in the production of composite materials in which the optical properties of the NPs incorporated are crucial to the desired application. - Highlights: • Synthesis of a hybrid ureasilicate matrix doped with CdSe nanoparticles. • Absorption and PL spectra of doped xerogels show features of quantum size effect. • Using MPTMS plays an important role in the optical properties of the nanocomposites. • HRTEM analysis showed well-dispersed spherical NPs with well-defined lattice

  9. OP-7/氯仿反胶束体系的制备及其增溶水量的研究%Study on preparation of OP-7/chloroform reverse micelle systems and their water solubilization performance

    Institute of Scientific and Technical Information of China (English)

    赵群; 陈怡秀; 朱青; 沈炎冰; 邓龙根; 马超; 阎克路

    2013-01-01

    The novel OP-7/chloroform reverse micelle system have been prepared by substituting chloroform for the alkanes of traditional reverse micelle systems,and the water solubilization behaviors of the systems have been investigated.The impact of OP-7' s concentration and the type of cosurfactant on the water solubilization amount of reverse micelle systems and the relationship between the water solubilization amount and the size and the conductivity of the systems were studied.The results showed that both the dosage of OP-7,the type and the concentration of the alcohol as cosufactant affect the water solubilization amount ; at the same time,the size and conductivity of the systems increased with increasing water solubilization amount,the OP-7/n-octanol/chloroform has the maximum water solubilization amount.%以氯仿代替传统的烃类溶剂,制备新型OP-7(非离子表面活性剂)/氯仿反胶束体系,并对该体系的增溶行为进行研究.考察了OP-7的浓度和不同的助表面活性剂对该体系增溶水量的影响及增溶水量与体系的粒径、电导率的关系.结果表明,OP-7的浓度、助表面活性剂醇的种类和用量都影响着体系的增溶水量;同时增溶水量增加,体系的粒径和电导率随之增加,OP-7/正辛醇/氯仿反胶束体系增溶水量最大.

  10. A light-responsive organofluid based on reverse worm-like micelles formed from an equi-charged, mixed, anionic gemini surfactant with an azobenzene spacer and a cationic conventional surfactant.

    Science.gov (United States)

    Yang, Duoping; Zhao, Jianxi

    2016-05-01

    An equally-charged mixture of an anionic gemini surfactant, O,O'-bis(sodium 2-tetradecylcarboxylate)-p-azodiphendiol (G14-azo), and a cationic surfactant, cetyltrimethylammonium bromide (CTAB), was dissolved in cyclohexane to form reverse worm-like micelles. Samples with different surfactant concentrations and amounts of added water were studied using rheological measurements. The amount of water, represented as the molar ratio of water to total surfactants W0, was c. 13 (at its minimum) in these equally charged systems of G14-azo (200 mmol L(-1))/CTAB. The low shear viscosity ηL of this system reached 4370 Pa s at W0 = 13 and the dynamic rheological result showed typical surfactant gel behaviour. Under UV-light irradiation, the transparent sample (G14-azo (300 mmol L(-1))/CTAB (600 mmol L(-1))) at W0 = 40 became turbid, during which ηL was rapidly reduced from the original 285 Pa s to 0.3 Pa s, indicating a transition of aggregate morphology from reverse worms into simple reverse micelles. Then the sample was returned to its original homogeneous state with c. 290 Pa s viscosity under visible light irradiation. However, this transition cannot be well achieved at low W0 due to the interior cores being too small. This limit has been attributed to both the Gemini type of surfactant molecule and to the inverted structure of aggregates. PMID:27021435

  11. Janus Micelles

    OpenAIRE

    Erhardt, R.; Böker, A.; Zettl, H; H. KAYA; PYCKHOUT-HINTZEN, W.; Krausch, G.; Abetz, V.; A. Müller

    2001-01-01

    A novel strategy to synthesize amphiphilic surface-compartmentalized nanoparticles based on linear ABC triblock copolymers is presented. These so-called Janus micelles consist of a cross-linked core and a corona with a "northern" and a "southern" hemisphere. Selectively cross-linking spherical domains of the polybutadiene middle block in a well-ordered bulk morphology of a polystyrene-block-polybutadiene-block-poly( methyl methacrylate) triblock copolymer (SBM) leads to the conservation of th...

  12. Immobilization of RuS2 Nanoparticles Prepared in Reverse Micellar System onto Thiol-Modified Polystyrene Particles and their Photocatalytic Properties

    International Nuclear Information System (INIS)

    RuS2 nanoparticles, smaller than 3 nm in diameter, were prepared by H2S gas injection into the AOT/isooctane reverse micellar solution containing RuCl3 aqueous solution. The nanoparticle size was found to be independent of the Wo (water content) value of the reverse micellar system, as shown by TEM observation. The recovery and immobilization of the RuS2 nanoparticles from reverse micelles onto thiol-modified polystyrene particles (PSt-SH) were successfully carried out, by the addition of PSt-SH into the reverse micellar solution under conditions of mild stirring. The resulting composites, PSt-RuS2, showed photocatalytic activity for H2 generation form aqueous solution containing 2-propanol and Na2SO3 as sacrificial electron donors

  13. Study on enzymatic characterizations of the immobilized enzymes in reversed micelle%两种反胶束固定化酶的催化性质研究

    Institute of Scientific and Technical Information of China (English)

    朱苗苗; 柳畅先

    2015-01-01

    探讨十六烷基三甲基氯化铵( CATC )-戊醇-辛烷反胶束体系固定化乳酸脱氢酶( LDH )和醇脱氢酶( ADH)的催化作用。试验了含水量、表面活性剂以及助溶剂浓度对于酶固载量的影响。对游离酶和固定化酶催化性质研究表明:LDH酶促反应的适宜 pH值分别为9.2和9.0,适宜温度为51℃和29℃,米氏常数15mmol·L-1和2mmol·L-1;ADH 酶促反应的适宜 pH 值为8.8和8.2,适宜温度为33℃和39℃,米氏常数4mmol·L-1和17mmol·L-1。应用反胶束固定化酶测定了试样中微量组分。%The enzymatic kinetics of immobilized lactate dehydrogenase( LDH) and alcohol dehydrogenase( ADH) with cetyl trimthyl ammonium chloride( CTAC)-pentanol-octane reversed micelle system were investigated. The effect of the level of water,the concen-tration of surfactant and cosolvent on the immobilization of LDH and ADH were assayed. The enzymatic characterizations of free and immobilized enzymes were also studied. In the case of LDH,the optimum pH of enzymatic reaction were 9. 2 and 9. 0 for the free and immobilized ones,respectively the optimum temperature were 51℃ and 29℃,respectively the michaelis constant were 15mmol ·L-1 and 2mmol·L-1 ,respectively. With regard to ADH,the optimum pH of enzymatic reaction were 8. 8 and 8. 2 for the free and immobilized ones,respectively the optimum temperature were 33℃ and 39℃,respectively the michaelis constant were 4mmol·L-1 and 17mmol·L-1 ,respectively. The immobilized enzymes could be used to determine trace component in samples.

  14. Study on enzymatic characterizations of the immobilized enzymes in reversed micelle%两种反胶束固定化酶的催化性质研究

    Institute of Scientific and Technical Information of China (English)

    朱苗苗; 柳畅先

    2015-01-01

    The enzymatic kinetics of immobilized lactate dehydrogenase( LDH) and alcohol dehydrogenase( ADH) with cetyl trimthyl ammonium chloride( CTAC)-pentanol-octane reversed micelle system were investigated. The effect of the level of water,the concen-tration of surfactant and cosolvent on the immobilization of LDH and ADH were assayed. The enzymatic characterizations of free and immobilized enzymes were also studied. In the case of LDH,the optimum pH of enzymatic reaction were 9. 2 and 9. 0 for the free and immobilized ones,respectively the optimum temperature were 51℃ and 29℃,respectively the michaelis constant were 15mmol ·L-1 and 2mmol·L-1 ,respectively. With regard to ADH,the optimum pH of enzymatic reaction were 8. 8 and 8. 2 for the free and immobilized ones,respectively the optimum temperature were 33℃ and 39℃,respectively the michaelis constant were 4mmol·L-1 and 17mmol·L-1 ,respectively. The immobilized enzymes could be used to determine trace component in samples.%探讨十六烷基三甲基氯化铵( CATC )-戊醇-辛烷反胶束体系固定化乳酸脱氢酶( LDH )和醇脱氢酶( ADH)的催化作用。试验了含水量、表面活性剂以及助溶剂浓度对于酶固载量的影响。对游离酶和固定化酶催化性质研究表明:LDH酶促反应的适宜 pH值分别为9.2和9.0,适宜温度为51℃和29℃,米氏常数15mmol·L-1和2mmol·L-1;ADH 酶促反应的适宜 pH 值为8.8和8.2,适宜温度为33℃和39℃,米氏常数4mmol·L-1和17mmol·L-1。应用反胶束固定化酶测定了试样中微量组分。

  15. Structural and magnetic susceptibility characteristics of Mn{sub 1-x}Cu{sub x}Fe{sub 2}O{sub 4} (x = 0-0.4) nanoparticles synthesized by self-assembling confined media of reverse micelle

    Energy Technology Data Exchange (ETDEWEB)

    Ghasemi, Ali, E-mail: ali13912001@yahoo.co [Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr (Iran, Islamic Republic of); Ghasemi, Ebrahim [Department of Materials Science and Engineering, Islamic Azad University-Majlesi Branch, Majlesi Town (Iran, Islamic Republic of)

    2010-10-22

    Research highlights: {yields} There are several techniques including sol-gel and co-precipitation which could be employed in order to fabricate fine ferrite particles. However the drawback of the mentioned process is relatively high sintering temperature. {yields} To the best of our knowledge no studies on the preparation of Mn{sub 1-x}Cu{sub x}Fe{sub 2}O{sub 4} ferrite at a low temperature have been reported. With this view in mind, current interest is to make Mn{sub 1-x}Cu{sub x}Fe{sub 2}O{sub 4} ferrite nanoparticles using reverse micelle technique at a low temperature. {yields} Magnetic properties were evaluated and it is found that there is strong interaction between nanoparticles. - Abstract: Mn{sub 1-x}Cu{sub x}Fe{sub 2}O{sub 4} (x = 0-0.4) ferrite nanoparticles were prepared by reverse micelle process. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) were employed to probe structural and magnetic properties of samples. The temperature dependence of blocking temperature was measured using Superconducting Quantum Interference Device (SQUID) and AC magnetic susceptibility. The phenomenological Neel-Brown and Vogel-Fulcher models were employed to distinguish between the interacting or non-interacting system. Results exhibited that there is strong interaction between fine particles.

  16. Structural and magnetic susceptibility characteristics of Mn1-xCuxFe2O4 (x = 0-0.4) nanoparticles synthesized by self-assembling confined media of reverse micelle

    International Nuclear Information System (INIS)

    Research highlights: → There are several techniques including sol-gel and co-precipitation which could be employed in order to fabricate fine ferrite particles. However the drawback of the mentioned process is relatively high sintering temperature. → To the best of our knowledge no studies on the preparation of Mn1-xCuxFe2O4 ferrite at a low temperature have been reported. With this view in mind, current interest is to make Mn1-xCuxFe2O4 ferrite nanoparticles using reverse micelle technique at a low temperature. → Magnetic properties were evaluated and it is found that there is strong interaction between nanoparticles. - Abstract: Mn1-xCuxFe2O4 (x = 0-0.4) ferrite nanoparticles were prepared by reverse micelle process. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) were employed to probe structural and magnetic properties of samples. The temperature dependence of blocking temperature was measured using Superconducting Quantum Interference Device (SQUID) and AC magnetic susceptibility. The phenomenological Neel-Brown and Vogel-Fulcher models were employed to distinguish between the interacting or non-interacting system. Results exhibited that there is strong interaction between fine particles.

  17. Dielectric Properties of Water in Butter and Water-AOT-Heptane Systems Measured using Terahertz Time-Domain Spectroscopy

    DEFF Research Database (Denmark)

    Møller, Uffe; Folkenberg, Jacob Riis; Jepsen, Peter Uhd

    2010-01-01

    We investigate the dielectric properties of water confined in nanometer-sized inverse micelles in mixtures of water, AOT, and heptane. We show that the dielectric properties of the confined water are dependent on the water pool size and different from those of bulk water. We also discuss the...... dielectric properties of different vegetable oils, lard, and butter, and use these properties to deduce the dielectric properties of water in butter, which are shown to deviate significantly from the dielectric properties of bulk water....

  18. Ibuprofen induced drug loaded polymeric micelles

    Institute of Scientific and Technical Information of China (English)

    Song Wei Tan; Hong Jun Wang; Ke Hua Tu; Hong Liang Jiang; Li Qun Wang

    2011-01-01

    Three model drugs with different function groups were chosen to dialyze with dextran-graft-poly (N-isopropylacrylamide). Only ibuprofen could induce the formation of drug loaded micelles, which was confirmed with dynamic light scattering and transmission electron microscope. Hydrogen-bonding between the amide groups of poly (N-isopropylacrylamide) and the carboxyl groups of ibuprofen was driving force for the drug-loaded micelle. It was also found that the diameter of the ibuprofen-loaded micelles changed reversibly against temperature.

  19. Bactericidal block copolymer micelles.

    Science.gov (United States)

    Vyhnalkova, Renata; Eisenberg, Adi; van de Ven, Theo

    2011-05-12

    Block copolymer micelles with bactericidal properties were designed to deactivate pathogens such as E. coli bacteria. The micelles of PS-b-PAA and PS-b-P4VP block copolymers were loaded with biocides TCMTB or TCN up to 20 or 30 wt.-%, depending on the type of antibacterial agent. Bacteria were exposed to loaded micelles and bacterial deactivation was evaluated. The micelles loaded with TCN are bactericidal; bacteria are killed in less than two minutes of exposure. The most likely interpretation of the data is that the biocide is transferred to the bacteria by repeated micelle/bacteria contacts, and not via the solution. PMID:21275041

  20. Phase diagram of soybean phosphatidylcholine-diacylglycerol-water studied by x-ray diffraction and 31P- and pulsed field gradient 1H-NMR: evidence for reversed micelles in the cubic phase.

    Science.gov (United States)

    Orädd, G; Lindblom, G; Fontell, K; Ljusberg-Wahren, H

    1995-05-01

    The phase equilibria of the system soybean phosphatidylcholine, diacylglycerol, and water has been determined using a combination of classical methods together with x-ray diffraction and NMR techniques. In particular, the extent of the phase regions of the lamellar, the reversed hexagonal, and the cubic phases have been determined. By pulsed field gradient 1H-NMR, the diffusion coefficients of all three components in a cubic phase composed of soybean phosphatidylcholine, diacylglycerol, and heavy water have been determined at 25 and 59 degrees C and also for the corresponding cubic phase composed of the chemically more well defined synthetic components 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dioleoylglycerol (DOG), and heavy water. The extension of the phase region of the cubic phase did not seem to change appreciably for the two ternary systems studied. The translational diffusion coefficient of DOPC in this cubic phase is more than an order of magnitude smaller (3 x 10(-13) m2 s-1, 59 degrees C) than the lateral diffusion coefficient of DOPC in an oriented lipid bilayer (5 x 10(-12) m2 s-1, 35 degrees C), whereas the diffusion coefficients of water and DOG were found to be about two orders of magnitude larger than DOPC at 59 degrees C. It is concluded that the cubic phase is built built up of closed reversed micelles in accordance with the suggestion from previous x-ray diffraction studies. PMID:7612827

  1. Synthesis of TiO2 nanoparticles by self-assembling reverse micelle cores of PS-b-PAA for functional textile applications

    International Nuclear Information System (INIS)

    Highlights: • TiO2 nanoparticles were synthesized within poly(styrene)-b-poly(acrylic acid) micelles. • The copolymer solution including nano TiO2 was coated onto textile fabrics. • UV-protective factor of nano TiO2 coated fabrics was estimated as 50+. • Nano TiO2 coated fabrics was found to exhibit a high photocatalytic activity. - Abstract: Titanium dioxide (i.e., titanium(IV) oxide, TiO2) nanoparticles have been fabricated using a copolymer templating technique in micellar solution of poly(styrene)-block-poly(acrylic acid), PS(10912)-b-PAA(4842) synthesized by atom transfer radical polymerization (ATRP). The size and morphology of the synthesized TiO2 nanoparticles have been characterized via TEM and XRD measurements. The average size of TiO2 nanoparticles was determined as 13 ± 3 and 13 ± 4 nm for titanium:copolymer ratios of 20:1 and 33:1, respectively. The copolymer solution including nano TiO2 particles has been coated onto textile fabrics to enhance their UV-blocking and self-cleaning properties. It has been determined that nano TiO2 coated textile fabrics have very good UV-blocking properties with 50+ of the ultraviolet protecting factor (UPF) and high photocatalytic efficiency with 69.2% of the photodegradation of methylene blue

  2. Synthesis of TiO{sub 2} nanoparticles by self-assembling reverse micelle cores of PS-b-PAA for functional textile applications

    Energy Technology Data Exchange (ETDEWEB)

    Akpolat, Leyla Budama; Çakır, Burçin Acar; Topel, Önder, E-mail: ondertopel@akdeniz.edu.tr; Hoda, Numan, E-mail: nhoda@akdeniz.edu.tr

    2015-04-15

    Highlights: • TiO{sub 2} nanoparticles were synthesized within poly(styrene)-b-poly(acrylic acid) micelles. • The copolymer solution including nano TiO{sub 2} was coated onto textile fabrics. • UV-protective factor of nano TiO{sub 2} coated fabrics was estimated as 50+. • Nano TiO{sub 2} coated fabrics was found to exhibit a high photocatalytic activity. - Abstract: Titanium dioxide (i.e., titanium(IV) oxide, TiO{sub 2}) nanoparticles have been fabricated using a copolymer templating technique in micellar solution of poly(styrene)-block-poly(acrylic acid), PS(10912)-b-PAA(4842) synthesized by atom transfer radical polymerization (ATRP). The size and morphology of the synthesized TiO{sub 2} nanoparticles have been characterized via TEM and XRD measurements. The average size of TiO{sub 2} nanoparticles was determined as 13 ± 3 and 13 ± 4 nm for titanium:copolymer ratios of 20:1 and 33:1, respectively. The copolymer solution including nano TiO{sub 2} particles has been coated onto textile fabrics to enhance their UV-blocking and self-cleaning properties. It has been determined that nano TiO{sub 2} coated textile fabrics have very good UV-blocking properties with 50+ of the ultraviolet protecting factor (UPF) and high photocatalytic efficiency with 69.2% of the photodegradation of methylene blue.

  3. Use of a self-assembling organogel as a reverse template in the preparation of imprinted porous polymer films.

    Science.gov (United States)

    Tan, Grace; Singh, Mohit; He, Jibao; John, Vijay T; McPherson, Gary L

    2005-09-27

    The concept of reverse templating of an organogel to form imprinted porous divinylbenzene polymer films with submicrometer channels is demonstrated. The organogel comprising a 1:1 molar ratio of two organogelators, that is, bis(2-ethylhexyl) sodium sulfosuccinate and 4-chlorophenol, was formed in divinylbenzene. The gel was cast as a thin film before UV polymerization of the solvent, and the organogelators were later removed by simple washing with water and isooctane. The integrity of the fiber bundles of the organogel was preserved during polymerization, and an exact hollow replica was obtained after the organogelators were leached away. It is easily possible to imprint gel fiber bundle structures into polymeric films through this technique. The gel can also be formed on macroporous substrates to yield supported thin porous polymeric films. With the incorporation of functional nanoparticles in AOT inverse micelles and hence the organogel, nanoparticle-containing porous polymer films exhibiting luminescence or magnetic properties are envisioned. PMID:16171368

  4. New functions for estimating AOT40 from ozone passive sampling

    Science.gov (United States)

    De Marco, Alessandra; Vitale, Marcello; Kilic, Umit; Serengil, Yusuf; Paoletti, Elena

    2014-10-01

    AOT40 is the present European standard to assess whether ozone (O3) pollution is a risk for vegetation, and is calculated by using hourly O3 concentrations from automatic devices, i.e. by active monitoring. Passive O3 monitoring is widespread in remote environments. The Loibl function estimates the mean daily O3 profile and thus hourly O3 concentrations, and has been proposed to calculate AOT40 from passive samplers. We investigated whether this function performs well in inhomogeneous terrains such as over the Italian country. Data from 75 active monitoring stations (28 rural and 47 suburban) were analysed over two years. AOT40 was calculated from hourly O3 data either measured by active measurements or estimated by the Loibl function applied to biweekly averages of active-measurement hourly data. The latter approach simulated the data obtained from passive monitoring, as two weeks is the usual exposure window of passive samplers. Residuals between AOT40 estimated by applying the Loibl function and AOT40 calculated from active monitoring ranged from +241% to -107%, suggesting that the Loibl function is inadequate to accurately predict AOT40 in Italy. New statistical models were built for both rural and suburban areas by using non-linear models and including predictors that can be easily measured at forest sites. The modelled AOT40 values strongly depended on physical predictors (latitude and longitude), alone or in combination with other predictors, such as seasonal cumulated ozone and elevation. These results suggest that multi-variate, non-linear regression models work better than the Loibl-based approach in estimating AOT40.

  5. 反胶束水合萃取藻蓝蛋白研究%Study of phycocyanin extracted from spirulina using reverse micelles extraction through hydration formation

    Institute of Scientific and Technical Information of China (English)

    丁晧; 裘俊红

    2011-01-01

    反胶束水合萃取技术是将反胶束萃取和水合物生成耦合在一起形成的一项新型、有发展潜力的分离技术,可应用于生物物质的活性控制及提取.实验中构建了CTAB/正辛烷—正戊醇反胶束体系,通过研究此体系中水合物生成对其内的藻蓝蛋白的萃取作用及纯化效果,获得反胶束水合萃取藻蓝蛋白的动力学规律以及温度、压力、CTAB浓度和初始含水量W0等对反胶束水合萃取藻蓝蛋白的影响规律,为进一步开展水合物法生物质活性控制及反胶束水合萃取技术的研究提供依据.%The new and innovative separation technology named as "reverse micellar hydrated extraction technology", which integrated hydrate separation with reverse micellar extraction, is used for the control of biological activity and extraction of bio-product. The kinetic research on the reverse micellar extraction of phycocyanin from the reverse micellar system formed by CTAB, n-octane and n-pentanol was implemented. Correspondingly, the extraction and purification behavior of phycocyanin from the reverse micellar system as well the effect mechanism of temperature, pressure, CTAB concentration, and initial water content Wo on phycocyanin extraction were acquired. The results contribute new information for the further research on the control of biological activity and reverse micellar hydrated extraction of bio-product.

  6. Transport of charged Aerosol OT inverse micelles in nonpolar liquids.

    Science.gov (United States)

    Karvar, Masoumeh; Strubbe, Filip; Beunis, Filip; Kemp, Roger; Smith, Ashley; Goulding, Mark; Neyts, Kristiaan

    2011-09-01

    Surfactants such as Aerosol OT (AOT) are commonly used to stabilize and electrically charge nonpolar colloids in devices such as electronic ink displays. The electrical behavior of such devices is strongly influenced by the presence of charged inverse micelles, formed by excess surfactant that does not cover the particles. The presence of charged inverse micelles results in increased conductivity of the solution, affecting both the energy consumption of the device and its switching characteristics. In this work, we use transient current measurements to investigate the electrical properties of suspensions of the surfactant Aerosol OT in dodecane. No particles are added, to isolate the effect of excess surfactant. The measured currents upon application of a voltage step are found to be exponentially decaying, and can be described by an analytical model based on an equivalent electric circuit. This behavior is physically interpreted, first by the high generation rate of charged inverse micelles giving the suspension resistor like properties, and second by the buildup of layers of charged inverse micelles at both electrodes, acting as capacitors. The model explains the measurements over a large range of surfactant concentrations, applied voltages, and device thicknesses. PMID:21728309

  7. Optimisation of ultrasound-assisted reverse micelles dispersive liquid-liquid micro-extraction by Box-Behnken design for determination of acetoin in butter followed by high performance liquid chromatography.

    Science.gov (United States)

    Roosta, Mostafa; Ghaedi, Mehrorang; Daneshfar, Ali

    2014-10-15

    A novel approach, ultrasound-assisted reverse micelles dispersive liquid-liquid microextraction (USA-RM-DLLME) followed by high performance liquid chromatography (HPLC) was developed for selective determination of acetoin in butter. The melted butter sample was diluted and homogenised by n-hexane and Triton X-100, respectively. Subsequently, 400μL of distilled water was added and the microextraction was accelerated by 4min sonication. After 8.5min of centrifugation, sedimented phase (surfactant-rich phase) was withdrawn by microsyringe and injected into the HPLC system for analysis. The influence of effective variables was optimised using Box-Behnken design (BBD) combined with desirability function (DF). Under optimised experimental conditions, the calibration graph was linear over the range of 0.6-200mgL(-1). The detection limit of method was 0.2mgL(-1) and coefficient of determination was 0.9992. The relative standard deviations (RSDs) were less than 5% (n=5) while the recoveries were in the range of 93.9-107.8%. PMID:24837929

  8. Synthesis of Zn{sub 1−x}Co{sub x}Fe{sub 2}O{sub 4}/MWCNTs nanocomposites using reverse micelle method: Investigation of their structural, magnetic, electrical, optical and photocatalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Charanjit [Department of Chemistry, Panjab University, Chandigarh 160 014 (India); Bansal, Sandeep [DST, New Delhi (India); Singhal, Sonal, E-mail: sonal1174@gmail.com [Department of Chemistry, Panjab University, Chandigarh 160 014 (India)

    2014-07-01

    Zn{sub 1−x}Co{sub x}Fe{sub 2}O{sub 4}/MWCNTs (x=0.0, 0.2, 0.4, 0.6 and 0.8) nanocomposites have been synthesized via reverse micelle method using functionalized carbon nanotubes. Powder X-ray Diffraction (XRD) patterns revealed the cubic spinel structure with Fd-3m space group without interfering the peak of CNTs. The fundamental Raman scattering peaks at 310, 460 and 662 cm{sup −1} have been observed due to different vibrational frequencies of Fe{sup 3+}, Co{sup 2+} and Zn{sup 2+} cations. Transmission Electron Micrographs (TEM) confirmed the attachment of nanoferrite particles on the surface of negatively charged CNTs. The saturation magnetization increased with Co{sup 2+} doping, however, no pronounced value of coercivity has been observed suggesting the superparamagnetic character. An increase in conductivity with increase in cobalt ion doping has been observed due to increase in hopping of electron between Co{sup 2+}–Co{sup 3+} ion pair. ZnFe{sub 2}O{sub 4}/MWCNTs composite has been found the best suitable visible light driven catalyst for the degradation of Rodhamine B (50 µM) with upto 99% in 5 h.

  9. Polymeric micelles containing reversibly phospholipid-modified anti-survivin siRNA: a promising strategy to overcome drug resistance in cancer

    OpenAIRE

    Salzano, G; Riehle, R.; Navarro, Gemma; Perche, Federico; Rosa, G.; Torchilin, VT

    2013-01-01

    The discovery that survivin, a small anti-apoptotic protein, is involved in chemoresistance, opens a new scenario to overcome the drug resistance in cancer. It was shown that siRNA can efficiently inhibit the expression of survivin in cancer cells. However, the clinical use of siRNA is still hampered by an unfavorable pharmacokinetic profile. To address this problem, earlier we developed a novel system to deliver siRNA into cancer cells. Namely, we reversibly modified the survivin siRNA with ...

  10. Temperature control of pattern formation in the Ru(bpy)(3)(2+)-catalyzed BZ-AOT system.

    Science.gov (United States)

    McIlwaine, Rachel; Vanag, Vladimir K; Epstein, Irving R

    2009-03-14

    Using temperature as a control parameter, we observe a transition from stationary Turing patterns at T = 15-20 degrees C to traveling waves at T = 50 degrees C (and above) in the Ru(bpy)(3)(2+)-catalyzed Belousov-Zhabotinsky (BZ) reaction incorporated into the water nanodroplets of a water-in-oil aerosol OT (AOT) microemulsion. At constant chemical composition, molar ratio and droplet fraction, the transition takes place via a series of stable patterns, including oscillatory Turing patterns (at 35-40 degrees C) and reversed oscillatory Turing patterns (at 50 degrees C). We attribute the pattern transitions to a temperature-induced percolation transition of the BZ-AOT microemulsion, implying a change from isolated water nanodroplets to a system-spanning network of water channels. PMID:19240935

  11. 有机溶剂及反胶束中的酶催化性能%Advance in Studies of the Catalytic Performance of Enzyme in Organic Media and Reverse Micelles

    Institute of Scientific and Technical Information of China (English)

    王丹; 黄锡荣; 李越中; 曲音波

    2003-01-01

      酶是生物合成与转化的关键因素,酶催化性能既取决于酶蛋白分子自身结构,又取决于介质微环境。非水酶学和胶束酶学是近二三十年来兴起的酶学研究新领域,主要研究有机溶剂和反胶束中酶的催化性能并探索其潜在应用。表面活性剂既是区分这两个分支领域的标志,又是联系两者的桥梁。本文在对这两个领域的研究概况作一简要介绍的同时,着重介绍了表面活性剂修饰酶、微乳液凝胶固定化酶等研究进展。%  Enzyme plays a key role in biosynthesis and biotransformation. Its catalytic properties depend on the structure of enzymic protein as well as on the microenvironment it experienced. Nonaqueous Enzymology and Micellar Enzymology are new branches of enzymology in recent decades, the research aim is to study the effect of organic solvent and reverse micelles on the catalytic properties of an enzyme. Surfactant, amphile, is viewed as both the mark to distinguish between them and the bridge to connect them. In addition to make a brief introduction of these two research fields, this review article puts emphasis on recent advances in modification of enzyme by surfactant and immobilization of enzyme in water-in-oil microemulsion.

  12. Pressure-induced structural transition of nonionic micelles

    Indian Academy of Sciences (India)

    V K Aswal; R Vavrin; J Kohlbrecher; A G Wagh

    2008-11-01

    We report dynamic light scattering and small angle neutron scattering studies of the pressure-induced structural transition of nonionic micelles of surfactant polyoxyethylene 10 lauryl ether (C12E10) in the pressure range 0 to 2000 bar. Measurements have been performed on 1 wt% C12E10 in aqueous solution with and without the addition of KF. Micelles undergo sphere to lamellar structural transitions as the pressure is increased. On addition of KF, rod-like micelles exist at ambient pressure, which results in rod-like to lamellar structural transition at a much lower pressure in the presence of KF. Micellar structural transitions have been observed to be reversible.

  13. Preconcentration of strontium by micelle modified solid phase extraction

    International Nuclear Information System (INIS)

    The preconcentration of strontium using a solid phase separation technique with selective micelle forming complexant has been studied. Di-2-ethylhexylphosphoric acid and its thio- and dithio derivatives were used as modifiers. The goal of this work was to study the influence of physico-chemical parameters on recovery of strontium after its preconcentration on reverse phase (Si-C-18) using micelle modifiers. (author) 5 refs.; 7 figs

  14. Complex coacervate core micelles.

    Science.gov (United States)

    Voets, Ilja K; de Keizer, Arie; Cohen Stuart, Martien A

    2009-01-01

    In this review we present an overview of the literature on the co-assembly of neutral-ionic block, graft, and random copolymers with oppositely charged species in aqueous solution. Oppositely charged species include synthetic (co)polymers of various architectures, biopolymers - such as proteins, enzymes and DNA - multivalent ions, metallic nanoparticles, low molecular weight surfactants, polyelectrolyte block copolymer micelles, metallo-supramolecular polymers, equilibrium polymers, etcetera. The resultant structures are termed complex coacervate core/polyion complex/block ionomer complex/interpolyelectrolyte complex micelles (or vesicles); i.e., in short C3Ms (or C3Vs) and PIC, BIC or IPEC micelles (and vesicles). Formation, structure, dynamics, properties, and function will be discussed. We focus on experimental work; theory and modelling will not be discussed. Recent developments in applications and micelles with heterogeneous coronas are emphasized. PMID:19038373

  15. Research on Catalytic Property of Immobilized Pepsin in Reverse Micelles%反胶束体系中固定化胃蛋白酶的催化性质研究

    Institute of Scientific and Technical Information of China (English)

    伏振宇; 李志光; 何纯莲

    2011-01-01

    将胃蛋白酶加至CTAB(十六烷基三甲基溴化铵)/环己烷/正辛醇反胶束体系中得到固定化胃蛋白酶,研究了反胶束含水率、乙醇体积分数对固定化胃蛋白酶活力的影响,并对固定化胃蛋白酶和游离胃蛋白酶的催化性质进行了比较研究.结果表明,反胶束含水率为12%、乙醇体积分数为30%时,固定化胃蛋白酶的活力达到最佳;固定化胃蛋白酶和游离胃蛋白酶的酶促反应最适温度分别为50℃和40℃、最适Ca2+浓度分别为0.02 mol·L-1和0.01mol· L-1;对酪蛋白的米氏常数Km分别为1.22×10-4 mol·L-1和1.29×10-4 mol·L-1.固定化胃蛋白酶较游离胃蛋白酶具有更高的酶活力、更好的热稳定性和储存稳定性.%Pepsin was solubilized in reverse micelles of CTAB(cetyltrimethylammonium bromide) in cyclo-hexane with octanol as co-surfactant. The effects of water content and ethanol volume fraction of reverse micells on immobilized pepsin activity were studied. And the catalytic properties of free and immobilized pepsin were investigated. The results indicated that the enzymatic activity of immobilized pepsin was the best when water content was 12%, ethanol volume fraction was 30%; the optimum temperature of immobilized and free pepsin was 50 ℃ and 40 ℃ ,the optimum Ca2+ concentration was 0. 02 mol · L-1 and 0. 01 mol · L-1 ,the Km was 1. 22× 10-4 mol · L-1 and 1. 29 × 10-4 mol · L-1, respectively. The enzymatic activity, thermal stability and storage stability of immobilized pepsin were superior to those of free pepsin.

  16. Process optimization for reverse micellar extraction of stem bromelain with a focus on back extraction.

    Science.gov (United States)

    Dhaneshwar, Amrut D; Chaurasiya, Ram Saran; Hebbar, H Umesh

    2014-01-01

    In the current study, reverse micellar extraction (RME) for the purification of stem bromelain was successfully achieved using the sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane system. A maximum forward extraction efficiency of 58.0% was obtained at 100 mM AOT concentration, aqueous phase pH of 8.0 and 0.2 M NaCl. Back extraction studies on altering stripping phase pH and KCl concentration, addition of counter-ion and iso-propyl alcohol (IPA) and mechanical agitation with glass beads indicated that IPA addition and agitation with glass beads have significant effects on extraction efficiency. The protein extraction was higher (51.9%) in case of the IPA (10% v/v) added system during back extraction as compared to a cetyltrimethylammonium bromide (100 mM) added system (9.42%). The central composite design technique was used to optimize the back extraction conditions further. Concentration of IPA, amount of glass beads, mixing time, and agitation speed (in rpm) were the variables selected. IPA concentration of 8.5% (v/v), glass bead concentration of 0.6 (w/v), and mixing time of 45 min at 400 rpm resulted in higher back extraction efficiency of 45.6% and activity recovery of 88.8% with purification of 3.04-fold. The study indicated that mechanical agitation using glass beads could be used for destabilizing the reverse micelles and release of bromelain back into the fresh aqueous phase. PMID:24616421

  17. Small angle neutron scattering study of doxorubicin–surfactant complexes encapsulated in block copolymer micelles

    Indian Academy of Sciences (India)

    Jayita Bhattacharjee; Gunjan Verma; V K Aswal; P A Hassan

    2008-11-01

    Self-assembling behaviour of block copolymers and their ability to evade the immune system through polyethylene oxide stealth makes it an attractive candidate for drug encapsulation. Micelles formed by polyethylene oxide–polypropylene oxide–polyethylene oxide triblock copolymers (PEO–PPO–PEO), pluronic P123, have been employed for encapsulating the anti-cancer drug doxorubicin hydrochloride. The binding affinity of doxorubicin within the micelle carrier is enhanced through complex formation of drug and anionic surfactant, aerosol OT (AOT). Electrostatic binding of doxorubicin with negatively charged surfactants leads to the formation of hydrophobic drug–surfactant complexes. Surfactant-induced partitioning of the anti-cancer drug into nonpolar solvents such as chloroform is investigated. SANS measurements were performed on pluronic P123 mi-celles in the presence of drug–surfactant complex. No significant changes in the structure of the micelles are observed upon drug encapsulation. This demonstrates that surfactant–drug complexes can be encapsulated in block copolymer micelles without disrupting the structure of aggregates.

  18. Polymeric micelle as the pseudostationary phase in electrokinetic chromatography.

    Science.gov (United States)

    Wang, Boni; Ni, Xinjiong; Yu, Meijuan; Cao, Yuhua

    2012-07-01

    A simple, green, and novel approach to prepare polymeric micelle with amphiphilic random copolymer P (MMA-co-MAA) via neutralization in aqueous medium has been developed, and the polymeric micelle was firstly applied as a pseudostationary phase (PSP) in electrokinetic chromatography (EKC) in the present work. Three structurally similar corticosteroids namely hydrocortisone, prednisolone, and prednisone were separated with EKC using polymeric micelle as PSP to assess the separation performance. The effects of polymeric concentration and pH on micellar microstructure including size, morphology, surface charge density and EKC performances have been investigated. TEM showed that amphiphilic random copolymers were self-assembled via neutralization to form micelles with well-defined size and shape. The size and shape of the micelle depended on the P (MMA-co-MAA) concentration and pH. At the concentration of 0.048 mM and pH 9.2, the polymeric micelles were of monodispersity and perfect spheres. DLS showed the size of micelle was almost equal as polymer concentration in the range of 0.0096-0.048 mM, and then enlarged sharply at the concentration larger than 0.048 mM. However, the zeta potentials of micelle were nearly unchanged. The polymer concentration is also the key parameter for EKC separation. Under the optimum conditions, three analytes could be baseline separated within 7.4 min. Compared with typical MEKC, MEEKC, and MEKC modified with IL ([Bmim]BF₄), the developed method was more rapid, efficient, and higher selective. The separation mechanism using polymeric micelle as PSP was reverse-phase interaction. The actual cosmetic samples were analyzed with recoveries between 97.3% and 113%. PMID:22633065

  19. Separation of Grape Skins Protein from Wine Sediment by Reversed Micelles Extraction%反胶团萃取分离葡萄酒下脚料中葡萄皮蛋白质

    Institute of Scientific and Technical Information of China (English)

    张喜峰; 李彩霞; 崔玮; 杨晶; 张芬琴

    2012-01-01

    采用阳离子表面活性剂十六烷基三甲基澳化铵(CTAB)反胶团萃取葡萄皮中的蛋白质。分别考察水相pH值、表面活性剂浓度、离子强度、蛋白质浓度、有机溶剂与助剂种类和比例、萃取温度对前萃取率的影响,并采用二次正交旋转组合的试验方法,考察前萃取过程中离子强度、表面活性剂浓度、水相pH值对前萃取率的影响。结果表明:32.68mmol/LCTAB/三氯甲烷-正丁醇(体积比4:1)的反胶团体系用于前萃取水相pH为6.4,包含0.4mol/LNaCl的葡萄皮中蛋白质的浸提液,前萃取率可达56.54%。理想的前萃取条件是:pH6.4、NaCl浓度0.4mol/L、CTAB浓度32.68mmol/L、蛋白质浓度1mg/mL、萃取温度30℃。在该条件下,采用pH3.8、后萃取温度20℃、0.8mol/LNaCl水相进行后萃取,后萃取率可达71.29%。%Extraction of protein from grape skins was investigated with reversed micelles extraction by using cationic surfactant CTAB . Effect of some parameters, such as pH value in aqueous phase, the content of surfactant, ionic strength, concentration of grape skins protein, the species and volume of organic solvent and co-solvent in reversed micellar solution as well as temperature, on the extraction ratio of grape skins protein was examined. Quadratic orthogonal rotation combination experiments were conducted to investigate the effects of concentrations of surfactant, ionic strength and pH value on the extraction rate. The forward-extraction yield of protein was found as high as 56.54% by 32.68mmol/L CTAB/Chloroform/n-butane(4: 1, v/v)from the supernatant with pH 6.4,0.4mol/L NaCl. The best extraction condition was pH value 6.4, concentrations of surfactant 32.68mmol/L, protein concentration l mg/mL, NaCI concentration 0.4mol/L, temperature 30℃. Under this condition: the backward extraction yield was 71.29% by 0.8 mol/L NaCI solution, temperature 20℃ with pH3

  20. Adenomatoid Odontogenic Tumor (AOT) Originating in a Unicystic Ameloblastoma: A Case Report

    OpenAIRE

    Jivan, Vibha; Altini, Mario; Meer, Shabnum; Mahomed, Farzana

    2007-01-01

    The follicular variant of the adenomatoid odontogenic tumor (AOT) is thought to originate from the reduced enamel epithelium of the dental follicle. The origin of the extra-follicular variant however, remains less clear. This paper presents a case of an extra-follicular AOT, which we believe originated from the epithelial lining of a unicystic ameloblastoma, and reviews the literature. The available evidence seems to indicate that some extra-follicular AOTs might arise as secondary phenomena ...

  1. REVERSE MICROEMULSION OF IGEPAL Co-720 SYSTEM AS MICROREACTOR FOR CdS SYNTHESIS

    Directory of Open Access Journals (Sweden)

    Fitria Rahmawati

    2016-08-01

    Full Text Available A Research on CdS synthesis in reverse microemulsion of Igepal CO-720 system has been conducted at various weight ratio of water to surfactant. Igepal CO-720 naturally forms oil in water (o/w emulsion type due to its high HLB (Hydrophilic -Lipophilic Balance value. Therefore, in this research the Igepal CO-720 system was inversed into water in oil (w/o system before it was used as microreactor for CdS synthesis. As comparison, a system of AOT (Aerosol OT; sodium bis (2-ethylhexyl sulfosuccinate which is naturally w/o system was also used as microreactor for CdS synthesis. The prepared CdS was analyzed by X-ray diffraction for crystal identification, scanning electron microscope for morphological analysis, UV-Vis for absorption edge determination and photoelectrochemical testing for photoactivity. The results show that the Igepal CO -720 system can be inverted into w/o system and can be used as microreactor for CdS synthesis. The prepared CdS is in nanosize with the average diameter of 2.517 ± 0.014 nm and the average gap energy of 3.805 ± 0.178 eV. The prepared CdS in Igepal CO-720 system has less regular form in comparison with morphology of the prepared CdS in AOT system. As the ω values decreases the particle diameter decreases, the gap energy increases and the % IPCE increases. It indicates that high surfactant concentration allows small size micelles formation and produced smaller CdS particle that has high surface area and therefore provide higher photocatalytic activity which was indicated by high value of its % IPCE.

  2. Structure of diglycerol polyisostearate nonionic surfactant micelles in nonpolar oil hexadecane: a SAXS study.

    Science.gov (United States)

    Shrestha, Lok Kumar; Shrestha, Rekha Goswami; Oyama, Keiichi; Matsuzawa, Makoto; Aramaki, Kenji

    2010-01-01

    Using a small-angle X-ray scattering technique, shape and size, and internal structure of diglycerol polyisostearate nonionic surfactant micelles in nonpolar oil n-hexadecane (HD) were investigated at 25 degrees C. Furthermore, the effect of added water on the structure of host reverse micelles was also investigated. The scattering data were evaluated by the generalized indirect Fourier transformation (GIFT) method and model fittings. It was found that diglycerol polyisostearate (abbreviated as (iso-C18)nG2, where n=2-4 represent the number of isostearate chain per surfactant molecule) spontaneously form reverse micelles in HD at 25 degrees C and their geometry (shape and size, and internal structure) could flexibly be controlled by a small change in the lipophilic tail architecture of the surfactant, temperature, and water addition. Increasing number of isostearate chain per surfactant molecule decreases the micelles size favoring prolate-to-sphere type transition. This phenomenon could be best understood due to voluminous lipophilic part of the surfactant. Increasing temperature decreases the size of the reverse micelles due to enhanced inter-penetration of the surfactant chain and the oil and also due to dominant hydrophobic character of the surfactant at higher temperatures. In the studies of effect of added water on the structure of micelles, it was found that the reverse micelles swell with water causing two dimensional micellar growths. PMID:20513967

  3. Polymerization of anionic wormlike micelles.

    Science.gov (United States)

    Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

    2006-01-31

    Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

  4. From micelle supramolecular assemblies in selective solvents to isoporous membranes

    KAUST Repository

    Nunes, Suzana Pereira

    2011-08-16

    The supramolecular assembly of PS-b-P4VP copolymer micelles induced by selective solvent mixtures was used to manufacture isoporous membranes. Micelle order in solution was confirmed by cryo-scanning electron microscopy in casting solutions, leading to ordered pore morphology. When dioxane, a solvent that interacts poorly with the micelle corona, was added to the solution, polymer-polymer segment contact was preferential, increasing the intermicelle contact. Immersion in water gave rise to asymmetric porous membranes with exceptional pore uniformity and high porosity. The introduction of a small number of carbon nanotubes to the casting solution improved the membrane stability and the reversibility of the gate response in the presence of different pH values. © 2011 American Chemical Society.

  5. Tuning intermicellar potential of Triton X-100– anthranilic acid mixed micelles

    Indian Academy of Sciences (India)

    Gunjan Verma; V K Aswal; S K Kulshreshtha; C Manohar; P A Hassan; Eric W Kaler

    2008-11-01

    Structural parameters of micelles formed by Triton X-100 in the presence of solubilized anthranilic acid at different pH values was investigated using light scattering and small angle neutron scattering. Analysis of the SANS data indicate that micelles are oblate ellipsoidal in nature with little variation in the dimensions, in the investigated pH range (from 0.5 to 6.0). The interaction potential of the micelles shows a minimum closer to the isoelectric point of anthranilic acid. A similar variation is observed in the cloud point of the micelles with pH. The observed variation in the interaction potential with pH of the micellar solution can be explained in terms of the reversal of charge on anthranilic acid due to shift in the acid–base equilibrium. The variation in interaction potential and cloud point with pH is modelled using Coulombic repulsion of charged molecules at the micelle interface.

  6. Macroscopic alignment of nanoparticle arrays in soft crystals of cubic and cylindrical polymer micelles

    Science.gov (United States)

    Pozzo, D. C.; Walker, L. M.

    2008-05-01

    We describe a method to organize nanometer-sized hydrophilic particles into ordered arrays by templating them in the soft, micelle-crystal phases (spherical and cylindrical) of a thermoreversible block copolymer. Small-angle neutron scattering (SANS) with contrast variation is used to show that the dispersed particles (in this case, proteins or silica) form structured arrays by being constrained in the interstitial cavities between the polymer micelles in the ordered micelle crystal. Simple shear is used to macroscopically align both phases of the nanocomposites (micelles and particles) into macro-domains. The temperature-induced order-order transition between templates of spherical and cylindrical micelles is demonstrated as a reversible technique to modify the structure of the templated nanoparticle arrays.

  7. Preparations of nanosized TiO{sub 2} in reverse microemulsion and their photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Man Sig; Lee, Gun-Dae; Ju, Chang-Sik; Hong, Seong-Soo [Division of Chemical Engineering, Pukyong National University, San 100 Yongdang-dong, Nam-Ku, Pusan 608-739 (Korea, Republic of)

    2005-09-15

    Nanosized titania sol has been produced by the controlled hydrolysis of titanium tetraisopropoxide (TTIP) in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles. The physical properties, such as surface area, crystallite size and crystallinity according to R and W{sub 0} ratio, have been investigated by TEM, XRD, BET, FT-IR, TGA and DTA. In addition, the photocatalytic decomposition of p-nitrophenol has been studied by using a batch reactor in the presence of UV light in order to compare the photocatalytic activity of prepared nanosized titania. It is shown that the anatase structure appears in the 300-600{sup o}C calcination temperature range and the transformation of anatase into rutile starts above 700{sup o}C. The crystallite size increases with increasing R and W{sub 0} ratio but W{sub 0} ratio shows a stronger effect on the crystallite size than R ratio. In the photocatalytic decomposition of p-nitrophenol, the photocatalytic activity is mainly determined by the crystallinity of titania. In addition, the titania calcined at 500{sup o}C shows the highest activity on the photocatalytic decomposition of p-nitrophenol(k=5.6x10{sup -3}min{sup -1}) and the pure anatase structure.

  8. Validation and empirical correction of MODIS AOT and AE over ocean

    Directory of Open Access Journals (Sweden)

    N. A. J. Schutgens

    2013-09-01

    Full Text Available We present a validation study of Collection 5 MODIS level 2 Aqua and Terra AOT (aerosol optical thickness and AE (Ångström exponent over ocean by comparison to coastal and island AERONET (AErosol RObotic NETwork sites for the years 2003–2009. We show that MODIS (MODerate-resolution Imaging Spectroradiometer AOT exhibits significant biases due to wind speed and cloudiness of the observed scene, while MODIS AE, although overall unbiased, exhibits less spatial contrast on global scales than the AERONET observations. The same behaviour can be seen when MODIS AOT is compared against Maritime Aerosol Network (MAN data, suggesting that the spatial coverage of our datasets does not preclude global conclusions. Thus, we develop empirical correction formulae for MODIS AOT and AE that significantly improve agreement of MODIS and AERONET observations. We show these correction formulae to be robust. Finally, we study random errors in the corrected MODIS AOT and AE and show that they mainly depend on AOT itself, although small contributions are present due to wind speed and cloud fraction in AOT random errors and due to AE and cloud fraction in AE random errors. Our analysis yields significantly higher random AOT errors than the official MODIS error estimate (0.03 + 0.05 τ, while random AE errors are smaller than might be expected. This new dataset of bias-corrected MODIS AOT and AE over ocean is intended for aerosol model validation and assimilation studies, but also has consequences as a stand-alone observational product. For instance, the corrected dataset suggests that much less fine mode aerosol is transported across the Pacific and Atlantic oceans.

  9. Phase behavior of supercritical CO2 microemulsion with food-grade surfactant AOT

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yongsheng; AN Xueqin; SHEN Weiguo; ZHANG Yinghua

    2006-01-01

    Phase behavior of scCO2 microemulsion formed with food grade surfactant sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) was studied. Critical microemulsion concentration (cμc) was deduced from the dependence of pressure of cloud points on the concentration of surfactant AOT at constant temperature and water concentration. The results show that there are transition points on the cloud point curve in a very narrow range of concentration of surfactant AOT. The transition points were changed with the temperature and water concentration. These phenomena show that lower temperature is suitable to forming microemulsion droplet and the microemulsion with high water concentration is likely to absorb more surfactants to structure the interface.

  10. Preparation and evaluation of reduction-responsive nano-micelles for miriplatin delivery.

    Science.gov (United States)

    Zhang, Ying; Hu, Dejian; Han, Shangcong; Yan, Guowen; Ma, Chao; Wei, Chen; Yu, Miao; Li, Dongmei; Sun, Yong

    2016-06-01

    A reduction-responsive amphiphilic core-shell micelle for miriplatin delivery was prepared and evaluated. A pyrene-terminated poly(2-(dimethylamino) ethyl acrylate) was synthesized through reversible addition-fragmentation chain transfer polymerization with 4-cyano-4-(ethylthiocarbonothioylthio) pentanoic acid as reversible addition-fragmentation chain transfer reagent and further modified by 2,2'-dithiodiethanol and 1-pyrenebutyric acid. Self-assembled blank micelles and drug-loaded micelles were obtained by dialysis method, and the particle size was proved to be about 40 nm with narrow dispersity by dynamic laser light scattering. Morphology results showed that blank micelles and drug-loaded micelles were spherical nanoparticles confirmed by transmission electron microscope, and the critical micelle concentration was as low as 6.09 µg/mL via pyrene fluorescence probe method. The reductive sensitivity of disulfide bond in BMs was further verified by changes in particle size, pyrene fluorescence intensity ratio (I338/I333), and morphology after treatment by dithiothreitol. Moreover, drug release rate in vitro of drug-loaded micelles was evaluated and the results suggested that this amphiphilic pyrene-modified poly(2-(dimethylamino) ethyl acrylate) can be used as reduction-triggered controlled release drug delivery carrier for hydrophobic drug. PMID:26743756

  11. Dye Encapsulation in Polynorbornene Micelles.

    Science.gov (United States)

    Bell, Nia C; Doyle, Samantha J; Battistelli, Giulia; LeGuyader, Clare L M; Thompson, Matthew P; Poe, Ambata M; Rheingold, Arnold; Moore, Curtis; Montalti, Marco; Thayumanavan, S; Tauber, Michael J; Gianneschi, Nathan C

    2015-09-01

    The encapsulation efficiency of high-Tg polynorbornene micelles was probed with a hydrophobic dye 2,6-diiodoboron-dipyrromethene (BODIPY). Changes in the visible absorption spectra of aggregated versus monomeric dye molecules provided a probe for assessing encapsulation. Polynorbornene micelles are found to be capable of loading up to one BODIPY dye per ten polymers. As the hydrophilic block size increased in the polymeric amphiphiles, more of the dye was incorporated within the micelles. This result is consistent with the dye associating with the polymer backbone in the shell of the micelles. The encapsulation rate varied significantly with temperature, and a slight dependence on micellar morphology was also noted. Additionally, we report a 740 μs triplet lifetime for the encapsulated BODIPY dye. The lifetime is the longest ever recorded for a BODIPY triplet excited state at room temperature and is attributed to hindered triplet-triplet annihilation in the high-viscosity micellar shell. PMID:26305151

  12. Glycation Reactions of Casein Micelles.

    Science.gov (United States)

    Moeckel, Ulrike; Duerasch, Anja; Weiz, Alexander; Ruck, Michael; Henle, Thomas

    2016-04-13

    After suspensions of micellar casein or nonmicellar sodium caseinate had been heated, respectively, in the presence and absence of glucose for 0-4 h at 100 °C, glycation compounds were quantitated. The formation of Amadori products as indicators for the "early" Maillard reaction were in the same range for both micellar and nonmicellar caseins, indicating that reactive amino acid side chains within the micelles are accessible for glucose in a comparable way as in nonmicellar casein. Significant differences, however, were observed concerning the formation of the advanced glycation end products (AGEs), namely, N(ε)-carboxymethyllysine (CML), pyrraline, pentosidine, and glyoxal-lysine dimer (GOLD). CML could be observerd in higher amounts in nonmicellar casein, whereas in the micelles the pyrraline formation was increased. Pentosidine and GOLD were formed in comparable amounts. Furthermore, the extent of protein cross-linking was significantly higher in the glycated casein micelles than in the nonmicellar casein samples. Dynamic light scattering and scanning electron microscopy showed that glycation has no influence on the size of the casein micelles, indicating that cross-linking occurs only in the interior of the micelles, but altered the surface morphology. Studies on glycation and nonenzymatic cross-linking can contribute to the understanding of the structure of casein micelles. PMID:27018258

  13. Validation and empirical correction of MODIS AOT and AE over ocean

    OpenAIRE

    N. A. J. Schutgens; Nakata, M; Nakajima, T.

    2013-01-01

    We present a validation study of Collection 5 MODIS level 2 Aqua and Terra AOT (aerosol optical thickness) and AE (Ångström exponent) over ocean by comparison to coastal and island AERONET (AErosol RObotic NETwork) sites for the years 2003–2009. We show that MODIS (MODerate-resolution Imaging Spectroradiometer) AOT exhibits significant biases due to wind speed and cloudiness of the observed scene, while MODIS AE, although overall unbiased, exhibits less spatial contrast on global scales than ...

  14. Casein micelle structure: a concise review

    OpenAIRE

    Chanokphat Phadungath

    2005-01-01

    Milk is a complex biological fluid with high amount of proteins, lipid and minerals. The function of milk is to supply nutrients such as essential amino acids required for the growth of the newborn. In addition, due to the importance of casein and casein micelles for the functional behavior of dairy products, the nature and structure of casein micelles have been studied extensively. However, the exact structure of casein micelles is still under debate. Various models for casein micelle struct...

  15. Nanoparticles of [Fe(NH2-trz)3]Br2.3H2O (NH2-trz=2-amino-1,2,4-triazole) prepared by the reverse micelle technique: influence of particle and coherent domain sizes on spin-crossover properties.

    Science.gov (United States)

    Forestier, Thibaut; Kaiba, Abdellah; Pechev, Stanislav; Denux, Dominique; Guionneau, Philippe; Etrillard, Céline; Daro, Nathalie; Freysz, Eric; Létard, Jean-François

    2009-06-15

    This paper describes the synthesis of iron(II) spin-crossover nanoparticles prepared by the reverse micelle technique by using the non-ionic surfactant Lauropal (Ifralan D0205) from the polyoxyethylenic family. By changing the surfactant/water ratio, the size of the particles of [Fe(NH2-trz)3]Br2.3H2O (with NH2trz=4-amino-1,2,4-triazole) can be controlled. On the macroscopic scale this complex exhibits cooperative thermal spin crossovers at 305 and 320 K. We find that when the size is reduced down to 50 nm, the spin transition becomes gradual and no hysteresis can be detected. For our data it seems that the critical size, for which the existence of a thermal hysteresis can be detected, is around 50 nm. Interestingly, the change of the particle size induces almost no change in the temperature of the thermal spin transition. A systematic determination of coherent domain size carried out on the nanoparticles by powder X-ray diffraction indicates that at approximately 30 nm individual particles consist of one coherent domain. PMID:19504472

  16. Risk-based evaluation of Allowed Outage Times (AOTs) considering risk of shutdown

    International Nuclear Information System (INIS)

    When safety systems fail during power operation, Technical Specifications (TS) usually limit the repair within Allowed Outage Time (AOT). If the repair cannot be completed within the AOT, or no AOT is allowed, the plant is required to be shut down for the repair. However, if the capability to remove decay heat is degraded, shutting down the plant with the need to operate the affected decay-heat removal systems may impose a substantial risk compared to continued power operation over a usual repair time. Thus, defining a proper AOT in such situations can be considered as a risk-comparison between the repair in frill power state with a temporarily increased level of risk, and the altemative of shutting down the plant for the repair in zero power state with a specific associated risk. The methodology of the risk-comparison approach, with a due consideration of the shutdown risk, has been further developed and applied to the AOT considerations of residual heat removal and standby service water systems of a boiling water reactor (BWR) plant. Based on the completed work, several improvements to the TS requirements for the systems studied can be suggested

  17. Micelle Structure and Hydrophobic Hydration.

    Science.gov (United States)

    Long, Joshua A; Rankin, Blake M; Ben-Amotz, Dor

    2015-08-26

    Despite the ubiquity and utility of micelles self-assembled from aqueous surfactants, longstanding questions remain regarding their surface structure and interior hydration. Here we combine Raman spectroscopy with multivariate curve resolution (Raman-MCR) to probe the hydrophobic hydration of surfactants with various aliphatic chain lengths, and either anionic (carboxylate) or cationic (trimethylammonium) head groups, both below and above the critical micelle concentration. Our results reveal significant penetration of water into micelle interiors, well beyond the first few carbons adjacent to the headgroup. Moreover, the vibrational C-D frequency shifts of solubilized deuterated n-hexane confirm that it resides in a dry, oil-like environment (while the localization of solubilized benzene is sensitive to headgroup charge). Our findings imply that the hydrophobic core of a micelle is surrounded by a highly corrugated surface containing hydrated non-polar cavities whose depth increases with increasing surfactant chain length, thus bearing a greater resemblance to soluble proteins than previously recognized. PMID:26222042

  18. Unexpected increasing AOT trends over northwest Bay of Bengal in the early postmonsoon season

    Energy Technology Data Exchange (ETDEWEB)

    Kishcha, P.; Starobinets, B.; Long, Charles N.; Alpert, P.

    2012-12-13

    The main point of our study is that aerosol trends can be created by changes in meteorology without changes in aerosol source strength. Over the 10 year period 2000–2009, in October, Moderate Resolution Imaging Spectroradiometer (MODIS) showed strong increasing aerosol optical thickness (AOT) trends of approximately 14% yr-1 over northwest Bay of Bengal (BoB) in the absence of AOT trends over the east of the Indian subcontinent. This was unexpected because sources of anthropogenic pollution were located over the Indian subcontinent and aerosol transport from the Indian subcontinent to northwest BoB was carried out by prevailing winds. In October, winds over the east of the Indian subcontinent were stronger than winds over northwest BoB, which resulted in wind convergence and accumulation of aerosol particles over northwest BoB. Moreover, there was an increasing trend in wind convergence over northwest BoB. This led to increasing trends in the accumulation of aerosol particles over northwest BoB and, consequently, to strong AOT trends over this area. In contrast to October, November showed no increasing AOT trends over northwest BoB or the nearby Indian subcontinent. The lack of AOT trends over northwest BoB corresponds to a lack of trends in wind convergence in that region. Finally, December domestic heating by the growing population resulted in positive AOT trends of similar magnitude over land and sea. Our findings illustrate that in order to explain and predict trends in regional aerosol loading, meteorological trends should be taken into consideration together with changes in aerosol source strength.

  19. Influence of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) on zinc electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Lehr, I.L. [Instituto de Ingenieria Electroquimica y Corrosion (INIEC), Departamento de Ingenieria Quimica, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina); Saidman, S.B., E-mail: ssaidman@criba.edu.ar [Instituto de Ingenieria Electroquimica y Corrosion (INIEC), Departamento de Ingenieria Quimica, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina)

    2012-03-01

    This work is a study of the electrodeposition of zinc onto SAE 4140 steel electrodes using solutions containing zinc sulfate and bis(2-ethylhexyl) sodium sulfosuccinate (AOT). The influence of different parameters such as electrolyte concentration, electrodeposition time and temperature on the morphology of the electrodeposits was analyzed. The deposits were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction. The variation of open circuit potential over time in chloride solutions was also evaluated. The nucleation-growth process and consequently the morphology of the electrodeposits are modified in the presence of AOT. The surfactant induces the formation of a porous deposit.

  20. Comparison of microstructures of microemulsion and swollen micelle in electrokinetic chromatography.

    Science.gov (United States)

    Cao, Yuhua; Ni, Xinjiong; Sheng, Jianwei

    2011-05-01

    Recently, 1-butanol modified MEKC was proven to be similar to MEEKC in separation performance. In the present work, typical microemulsion containing 0.8% n-octane/3.3% SDS/6.6% 1-butanol/20 mM borax buffer and corresponding swollen micelle without n-octane were used to compare their microdroplet structures including hydrodynamic radius, electrokinetic potential ζ and charge density at the hydrodynamic shear surface, as well as microenvironment polarity in the interior of the microdroplets. Three kinds of corticosteroids were separated with MEEKC and 1-butanol modified MEKC to assess their separation performances. The experiment results showed that both microstructure and separation performance in microemulsion and in swollen micelle systems were alike, no matter whether oil phase n-octane was present. The environment polarity in the core of swollen micelle was slightly higher than in the microemulsions, and both of them were higher than in n-octane medium. Furthermore, the influences of SDS and 1-butanol concentration on microstructures were measured in details. Increasing the amount of SDS, hydrodynamic radius decreased in microemulsion but increased in swollen micelle. On the contrary, ζ and shear surface charge density changed in the reverse trends. With increment of 1-butanol concentration, the hydrodynamic radius increased dramatically in microemulsions, whereas decreased slightly in swollen micelle. Even though using n-octane as oil core was not a key factor, microemulsions and swollen micelle as pseudostationary phase in EKC should not be exactly the same. PMID:21439571

  1. Preparation and Characterization of a pH-Responsive Core Cross-linked Polymer Micelle

    Science.gov (United States)

    Kousaka, Shouta; Sugahara, Makoto; Endo, Tatsuya; Yusa, Shin-ichi

    2011-01-01

    Poly(ethylene glycol)-b-poly(2-(diethylamino) ethyl methacrylate-co-2-cinnamoyl-oxyethyl acrylate) (PEG-b-P(DEA/CEA)) was prepared by reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization. pH-responsive association behaviour of PEG-b-P(DEA/CEA) in 0.1 M NaCl was characterized by dynamic light scattering (DLS). As solution pH is increased from an acidic pH, the hydrodynamic radius (Rh) increases, indicative of the polymer micelle formation. The formation of a micelle was also supported by static light scattering (SLS) data. The cinnamoyl groups in the core of the polymer micelle undergo photodimerization, yielding cross-links between polymer chains. The core of the polymer micelle was fixed, which was confirmed by DLS, SLS, and small angle X-ray scattering (SAXS) techniques. When pH is decreased to 3, Rh of the core cross-linked (CCL) polymer micelle slightly increases due to the protonation of the DEA unit in the cross-linked core. The reversible pH-induced swelling and shrinking behaviour can be observed.

  2. Synergistic effect of pH-responsive wormlike micelles based on a simple amphiphile.

    Science.gov (United States)

    Wu, Xuepeng; Wu, Yining; Yang, Shuai; Zhao, Mingwei; Gao, Mingwei; Li, Hao; Dai, Caili

    2016-05-18

    Imagine a novel solution that can be switched reversibly from low viscosity to high viscosity with only one additive, upon different commands. To this end, we have developed a simple and effective route to form smart, multi-response wormlike micelles based on a synthesized surfactant, N-cetyl-N,N-diisopropanolammonium bromide (CDIAB). Moreover, we provide new insight into the effects of synergy on this smart wormlike micelle. Rheological measurements were used to study the morphology of the wormlike micelles; (1)H NMR spectroscopy and density functional theory (DFT) calculations were employed to investigate the molecular arrangements and mechanism of the synergy involved in the reversible reactions of pH-response and CO2-response of the micelles in solution. Based on the abovementioned results, it is encouraging to discover that binding energy and electrostatic interaction are the basic driving forces in the formation of wormlike micelles. Moreover, stable viscoelastic behavior was observed in the CDIAB system, with strong binding energy and electrostatic interactions. It is highly anticipated that the synergy observed in this surfactant will be of particular interest due to its novel mechanism and unique properties. PMID:27094804

  3. Fast local dynamics in CTAB micelles

    Science.gov (United States)

    Sharma, V. K.; Mitra, S.; Embs, J. Peter; Mukhopadhyay, R.

    2012-06-01

    Molecular dynamics of cetyltrimethylammonium Bromide (CTAB) micelle has been studied in the temperature range 310-340 K using quasielastic neutron scattering technique. Data analysis clearly shows the presence of two distinct motions; i) whole micellar motion or global diffusion and ii) faster internal motion of the CTAB monomer. The global diffusion associated with the whole micelle is found to be Fickian in nature and diffusivity is found to increase with temperature. A localized translational model describes internal motion of the micelles. Addition of an electrolyte, which is known to affect the size/shape of micelles, does not affect the dynamics of the CTAB micelles. This is in contrast with anionic sodium dodecyl sulfate micelles where addition of electrolyte results in slowing down of the dynamics.

  4. Simulation by Aspen Plus on desolventizing of crude oil in soybean protein extracting process with reverse micelles%用 Aspen Plus 模拟反胶束萃取大豆蛋白过程中毛油脱溶操作

    Institute of Scientific and Technical Information of China (English)

    王鑫; 于国萍; 杜成亮; 吴志光

    2013-01-01

    Compared with other traditional methods, the disadvantages of high production costs and pollution prevention were overcome in the soy-protein extraction process by reverse micelles. Soybean crude oil, containing organic solvent, can be extracted together with soybean protein by reverse micelles. It is necessary to control the purity of the organic solvent that is recycled, as well as the purity of the soybean crude oil in the circulating production process. The Aspen Plus 11.1 software is used for simulating the desolventizing of crude oil in the soy-protein extraction process by reverse micelles, which is aimed at recycling the organic solvent. This work aims to study continuous and circulating spirit distillation by computational simulation, presenting some strategies of process control to regulate the purity of the solvent and the soybean oil. With the modular analysis function of Aspen Plus, the purity of the oil and solvent, the stage number of distillation column, and the heat load of the reboiler and the condenser were analyzed. A generalized model (based on the NRTL model) for estimation of activity coefficients is applied to the simulation of the extraction process. The equilibrium stage model based on the RADFRAC module of Aspen Plus is employed for the steady-state simulation of the improved process flowsheet, and therefore rigorous simulations allow the appropriate operating conditions to be established in the separating process. It is shown in the results that the reflux ratio of the vacuum distillation was 0.352, the distillate flow was 10.348 kg/h, and the purity of the oil and solvent can be 98.9% and 99.7% respectively, while the actual heat loads of the reboiler and the condenser were 1398.824 W and -1626.226 W, respectively. According to the sensitivity analysis, the concentration of oil and solvent grew respectively with the number of stages, and the optimal number of stages was seven. The cost was analyzed based on simulation calculations, in

  5. Light-responsive viscoelastic fluids based on anionic wormlike micelles.

    Science.gov (United States)

    Lu, Yechang; Zhou, Tengfei; Fan, Qing; Dong, Jinfeng; Li, Xuefeng

    2013-12-15

    A new class of light-responsive viscoelastic fluids based on anionic wormlike micelles is reported. The key components are sodium oleate (NaOA) and a cationic azobenzene dye, 1-[2-(4-phenylazo-phenoxy)-ethyl]-3-methylimidazolium bromide (C0AZOC2IMB). These binary systems are gel-like fluids at certain concentration ratios of [C0AZOC2IMB]/[NaOA], e.g. 35/100, owing to the formation of long, entangled wormlike micelles. The viscosity of these fluids can be controlled reversibly by light due to photo isomerization between trans-C0AZOC2IMB and cis-C0AZOC2IMB. For example, the zero-shear viscosity (η0) of an originally gel-like sample is high up to ~1300 Pa s when C0AZOC2IMB is in its trans from, whereas the mixture becomes a Newtonian fluid with η0 about 0.01 Pa s after UV light irradiation. For the post-irradiated cis-C0AZOC2IMB, short cylindrical micelles form, hence accounting for the lower viscosity. Evidence for the structural transition is provided by UV-vis spectra, rheology, (1)H NMR and cryo-transmission electronic microscopy measurements. PMID:24144381

  6. Isomerization of Orthogonal Molecular Switches Encapsulated within Micelles Solubilizing Carbon Nanotubes

    DEFF Research Database (Denmark)

    Kreft, Stefanie K.; Petersen, Michael Åxman; Nielsen, Mogens Brøndsted;

    2015-01-01

    We study the effects of the proximity of the orthogonal dipole-switching moiety dihydroazulene/vinylheptafulvene (DHA/VHF) to carbon nanotubes (CNTs). The switches are introduced into a micelle surrounding the CNTs, thereby achieving very close proximity between the molecules and the CNTs for the...... first time. The change of the molecules' configuration is not hindered by its encapsulation: We report the reversible switching of molecules inside CNT surrounding micelles. The orthogonality of the switch also allows us for the first time to observe the effect of the molecule on the emission spectra of...

  7. The Photovoltaic Effect of CdS Quantum Dots Synthesized in Inverse Micelles and R-Phycoerythrin Tunnel Cavities.

    Science.gov (United States)

    Bekasova, Olga D; Revina, Alexandra A; Kornienko, Ekaterina S; Kurganov, Boris I

    2015-06-01

    CdS quantum dots (CdS QDs) 4.3 nm in diameter synthesized in an AOT/isooctane/water microemulsion and in R-phycoerythrin tunnel cavities (3.5 × 6.0 nm) were analyzed for photoelectrochemical properties. The CdS QDs preparations were applied onto a platinum electrode to obtain solid films. Experiments were performed in a two-section vessel, with one section filled with ethanol and the other, with 3 M KCl. The sections were connected through an agar stopper. It was found that illumination of the films resulted in a change of the electrode potential. The magnitude of this change and the kinetics of the appearance and disappearance of the photopotential, i.e., the difference between the electrode potential on the light and in dark, depended on the nature of the QD shell. The photovoltaic effect of CdS QDs in R-phycoerythrin, compared to that of CdS QDs in AOT/isooctane micelles, is three to four times greater due to the photosensitizing action of R-phycoerythrin. The photosensitized effect was markedly higher than the photoelectric sensitivity of R-phycoerythrin and had the opposite polarity. Changes in the potential upon turning the light on and off could be observed repeatedly. PMID:25935221

  8. Mixed micelle structure: charge and alcohol influence

    International Nuclear Information System (INIS)

    After a brief summary of the method used to derive the structure of a micelle from a small-angle scattering experiment, the results of a study on mixed micelles are presented. The extension of the method to ternary solutions is described and the difficulties encountered are outlined

  9. Unimolecular micelles and electrostatic nanoassemblies stemming from hyperbranched polyethyleneimine

    International Nuclear Information System (INIS)

    Full text: Hyperbranched polyethyleneimine (HPEI) was used as a building block to construct different self-assembled soft nanomaterials. This was accomplished via covalent linkage of carboxylic acids (CA) of different chain lengths to terminal amino groups of HPEI, thus leading to the formation of reverse unimolecular micelles constituted of a hydrophilic core and a hydrophobic shell. On the other hand, acid base interactions in organic solvents between CAs and peripheral amino groups of HPEI also facilitated the formation of electrostatic assemblies with reverse micellar properties. In this work we describe the formation of both structures as well as their characterization using diverse techniques including SAXS, NMR, IR, and fluorescence spectroscopy, among others. Unimolecular micelles were synthesized through the reaction of HPEI (Mn= 10 KDa) and acyl chlorides with different chain lengths (C8, C10, C12, C14, C16, C18). Depending on the chain length, the solvent and the temperature, a broad variety of supra macromolecular assemblies can be observed by SAXS measurements, including structured aggregation, and gelation. Hyperbranched electrostatic assemblies were simply produced by mixing HPEI with selected carboxylic acids (C8, C10, C12, C14, C16, C18) in an appropriate solvent, which dissolves the CA, or both reactants, i.e. chloroform, toluene or THF. The formation of the assemblies was corroborated using FT-IR by monitoring the appearance of the carboxylate bands. SAXS experiments of electrostatically assembled micelles showed globular, core-shell structures, whose characteristics are similar, in many cases, to their covalent counterparts prepared using the same chain length CA shells. (author)

  10. Synthesis by reverse microemulsion of nano structured ferrite to be utilized in hydrogen production by water

    International Nuclear Information System (INIS)

    Micelle and reverse micelle microemulsions can be favourably utilized in producing nano sized particles. The paper reports a general description of microemulsions systems, as well as their application in materials synthesis. By using one of the described methods, nano structured manganese ferrite, to be utilized in hydrogen production. was synthesized and the produced material was characterized in terms of morphological, microstructure and thermal properties

  11. Development of STI/AOT optimization methodology and an application to the AFWPs with adverse effects

    International Nuclear Information System (INIS)

    Adverse effects caused by the surveillance test for the components of nuclear power plant involve plant transients, unnecessary wear, burden on licensee's time, and the radiation exposure to personnel along with the characteristics of each component. The optimization methodology of STI and AOT has been developed and applied to AFWPs of a reference plant. The approach proposed in this paper consists of the results in minimal mean unavailability of the two-out-of-four system with adverse effects are analytically calculated for the example system. The surveillance testing strategy are given by the sequential test, the staggered test and the train staggered test, which is a mixed test scheme. In the system level, the sensitivity analyses for the STI and AOT, are performed for the measure of the system unavailability of the top event in the fault tree developed for the example system. This methodology may contribute to establishing the basis for the risk-based regulations. (author)

  12. Sulfonsuccinate (AOT Capped Pure and Mn-Doped CdS Nanoparticles

    Directory of Open Access Journals (Sweden)

    D. Venkatesan

    2012-01-01

    Full Text Available CdS nanoparticles and thin films are well known for their excellent semiconducting properties. When transition metal ions are doped into the CdS, it exhibits magnetic properties in addition to semiconducting properties and they are termed as dilute magnetic semiconductors (DMSs. In this paper, we discuss the preparation of sodium bis(2-ethylhexyl sulfonsuccinate (AOT capped CdS nanoparticles and thin films doped with magnetic impurity Mn. Sodium bis(2-ethulexyl sulfonsuccinate (AOT, capping agent promotes the uniform formation of nanoparticles. Optical characterizations are made using the UV-Vis spectrometer, PL, and FTIR. XRD shows the hexagonal structure of the CdS. SEM images and EDS measurements were made for the thin films. EPR shows the clear hyperfine lines corresponding to Mn2+ ion in the CdS nanoparticles.

  13. Anomalous change in interfacial tension induced by collapses of AOT microemulsions at heptane/water interface

    Science.gov (United States)

    Takahashi, Masahiko; Yui, Hiroharu; Ikezoe, Yasuhiro; Sawada, Tsuguo

    2004-05-01

    Dynamic behavior of water-in-oil microemulsions at the oil/water interface was investigated using the quasi-elastic laser scattering method. We observed an anomalous rebound behavior of interfacial tension γ induced by collapses of microemulsions and adsorptions of AOT molecules at the interface. γ rapidly decreased and reached a minimum value (5.5 mN/m) at about 500 s after the preparation of the interface, and then increased gradually for about 2000 s to the equilibrium value (8.0 mN/m). We considered the mechanism of the rebound behavior in terms of transient change in interfacial thickness induced by the collapses of AOT microemulsions.

  14. AOT-microemulsions-based formation and evolution of PbWO$_{4}$ crystals

    CERN Document Server

    Chen, D; Tang Kai Bin; Liang Zhen Hua; Zheng Hua Gui

    2004-01-01

    Anionic surfactant-AOT-microemulsions-assisted formation and evolution of PbWO//4 nanostructures with bundles rodlike, ellipsoidlike, and spherelike prepared at different media conditions were studied by powder X-ray diffraction pattern, field emission scanning electron microscopy, and transmission electron microscopy. The possible mechanisms for the formation of PbWO//4 samples in series of microemulsion systems were discussed. Various comparison experiments show that several experimental parameters, such as the AOT concentration, the water content, and reaction temperature play important roles in the morphological control of PbWO//4 nanostructures. Room-temperature photoluminescence of PbWO//4 samples with different morphologies has also been investigated and the results reveal that all these samples showed similar features with emissions at 480 similar to 510 nm but different luminescence intensity. 40 Refs.

  15. Spatiotemporal Spectral Variations of AOT in India’s EEZ over Arabian Sea: Validation of OCM-II

    Directory of Open Access Journals (Sweden)

    C. P. Simha

    2012-01-01

    Full Text Available We report the results of sun-photometric measurements of Aerosol Optical Thickness (AOT in India’s Exclusive Economic Zone (EEZ over the Arabian Sea along with synchronous Ocean Color Monitor (OCM-II derived AOT estimates during December 12, 2009–January 10, 2010. Relatively higher values of Angstrom exponent (α around 1.2 near coast and 0.2–0.8 in the India’s EEZ, observed during the cruise period, indicate the presence of smaller particles near the coast due to anthropogenic activities; and larger particles in the India’s EEZ due to advection of pollutants from Indian subcontinent via long-range transport. Results related to α and its derivative reveal four different aerosol types (urban-industrial, desert-dust, clean-marine, and mixed-type with varying fraction during the study period. Surface radiative forcing due to aerosols is found to be 20 W/m2 over India’s EEZ. OCM-derived AOTs showed good corroboration with in situ measurements with a correlation coefficient of about 0.95. A reasonably good correlation was also observed between AOT and wind speed (R = 0.6; AOT and relative humidity (R = 0.58. The concurrent MODIS AOT data also agree well with those observed by the OCEANSAT (OCM-II satellite during the campaign period.

  16. Recent advances in nanoparticle synthesis with reversed micelles

    OpenAIRE

    J. Eastoe; Hollamby, MJ; Hudson, L

    2006-01-01

    Synthesis of nanoparticles in microemulsions is an area of considerable current interest. This subject can be broadly divided into two sections defined by the nature of the host microemulsion reaction medium. Water-in-oil microemulsions have been used to prepare nanoparticles for more than two decades, and a wide variety of materials has been synthesised by these methods. Control parameters have been elucidated for influencing both nanoparticle concentration and morphology, allowing for tailo...

  17. Reverse Micelle Based Synthesis of Microporous Materials in Microgravity

    Science.gov (United States)

    Dutta, Prabir K.

    2001-01-01

    Microporous materials include a large group of solids of varying chemical composition as well as porosity. These materials are characterized by channels and cavities of molecular dimensions. The framework structure is made up of interconnecting T-O-T' bonds, where T and T' can be Si, Al, P, Ga, Fe, Co, Zn, B and a host of other elements. Materials with Si-O-Al bonding in the framework are called zeolites and are extensively used in many applications. Ion-exchange properties of these materials are exploited in the consumer and environmental industries. Chemical and petroleum industries use zeolites as catalysts in hydrocarbon transform ations. Synthesis of new microporous frameworks has led to the development of new technologies, and thus considerable effort worldwide is expended in their discovery. Microporous materials are typically made under hydrothermal conditions. Influence of nature of starting reactants, structure directing agents, pH, temperature, and aging all have profound influence on the synthesis process. This is primarily because the most interesting open frameworks are not necessarily the stable structures in the reaction medium. Thus, the discovery of new frameworks is often tied to finding the right composition and synthesis conditions that allow for kinetic stabilization of the structure. This complexity of the synthesis process and limited understanding of it has made it difficult to develop directed is of microporous materials and most advances in this field have been made by trial and error. The basic issues in crystal growth of these materials include: (1) Nature of the nucleation process; (2) Molecular structure and assembly of nuclei; (3) Growth of nuclei into crystals; (4) Morphology control; and (5) Transformation of frameworks into other structures. The NASA-funded research described in this paper focuses on all the above issues and has been described in several publications. We present the highlights of our program, especially with the focus on possible experiments in microgravity.

  18. Autoregressive spatially varying coefficients model for predicting daily PM2.5 using VIIRS satellite AOT

    Science.gov (United States)

    Schliep, E. M.; Gelfand, A. E.; Holland, D. M.

    2015-12-01

    There is considerable demand for accurate air quality information in human health analyses. The sparsity of ground monitoring stations across the United States motivates the need for advanced statistical models to predict air quality metrics, such as PM2.5, at unobserved sites. Remote sensing technologies have the potential to expand our knowledge of PM2.5 spatial patterns beyond what we can predict from current PM2.5 monitoring networks. Data from satellites have an additional advantage in not requiring extensive emission inventories necessary for most atmospheric models that have been used in earlier data fusion models for air pollution. Statistical models combining monitoring station data with satellite-obtained aerosol optical thickness (AOT), also referred to as aerosol optical depth (AOD), have been proposed in the literature with varying levels of success in predicting PM2.5. The benefit of using AOT is that satellites provide complete gridded spatial coverage. However, the challenges involved with using it in fusion models are (1) the correlation between the two data sources varies both in time and in space, (2) the data sources are temporally and spatially misaligned, and (3) there is extensive missingness in the monitoring data and also in the satellite data due to cloud cover. We propose a hierarchical autoregressive spatially varying coefficients model to jointly model the two data sources, which addresses the foregoing challenges. Additionally, we offer formal model comparison for competing models in terms of model fit and out of sample prediction of PM2.5. The models are applied to daily observations of PM2.5 and AOT in the summer months of 2013 across the conterminous United States. Most notably, during this time period, we find small in-sample improvement incorporating AOT into our autoregressive model but little out-of-sample predictive improvement.

  19. Reversible thermal gelation in soft spheres

    DEFF Research Database (Denmark)

    Kapnistos, M.; Vlassopoulos, D.; Fytas, G.;

    2000-01-01

    Upon heating, concentrated solutions of star polymers and block copolymer micelles in a good solvent, representing soft spheres, undergo a reversible gelation. This phenomenon is attributed to the formation of clusters causing a partial dynamic arrest of the swollen interpenetrating spheres at high...... temperatures. A phase diagram analogous to that of sterically stabilized colloids is proposed....

  20. Dynamic Processes in Diblock Copolymer Micelles

    Science.gov (United States)

    Robertson, Megan; Singh, Avantika

    2013-03-01

    Diblock copolymers, which form micelle structures in selective solvents, offer advantages of robustness and tunability of micelle characteristics as compared to small molecule surfactants. Diblock copolymer micelles in water have been a subject of great interest in drug delivery applications based on their high loading capacity and targeted drug delivery. The aim of this work is to understand the dynamic processes which underlie the self-assembly of diblock copolymer micelle systems which have a semi-crystalline core. Due to the large size of the molecules, the self-assembly of block copolymer micelles occurs on significantly longer time scales than small molecule analogues. The present work focuses on amphiphilic diblock copolymers containing blocks of poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic, semi-crystalline polymer), which spontaneously self-assemble into spherical micelles in water. A variety of experimental techniques are used to probe the kinetic processes relevant to micelle self-assembly, including time-resolved neutron scattering, dynamic light scattering, pulsed field gradient nuclear magnetic resonance, and fluorescence resonance energy transfer experiments.

  1. Casein micelle structure: a concise review

    Directory of Open Access Journals (Sweden)

    Chanokphat Phadungath

    2005-01-01

    Full Text Available Milk is a complex biological fluid with high amount of proteins, lipid and minerals. The function of milk is to supply nutrients such as essential amino acids required for the growth of the newborn. In addition, due to the importance of casein and casein micelles for the functional behavior of dairy products, the nature and structure of casein micelles have been studied extensively. However, the exact structure of casein micelles is still under debate. Various models for casein micelle structure have been proposed. Most of the proposedmodels fall into three general categories, which are: coat-core, subunit (sub-micelles, and internal structure models. The coat-core models, proposed by Waugh and Nobel in 1965, Payens in 1966, Parry and Carroll in 1969, and Paquin and co-workers in 1987, describe the micelle as an aggregate of caseins with outer layer differing in composition form the interior, and the structure of the inner part is not accurately identified. The sub-micelle models, proposed by Morr in 1967, Slattery and Evard in 1973, Schmidt in 1980, Walstra in1984, and Ono and Obata in 1989, is considered to be composed of roughly spherical uniform subunits. The last models, the internal structure models, which were proposed by Rose in 1969, Garnier and Ribadeau- Dumas in 1970, Holt in 1992, and Horne in 1998, specify the mode of aggregation of the different caseins.

  2. Mechano-responsive hydrogels crosslinked by reactive block copolymer micelles

    Science.gov (United States)

    Xiao, Longxi

    Hydrogels are crosslinked polymeric networks that can swell in water without dissolution. Owing to their structural similarity to the native extracelluar matrices, hydrogels have been widely used in biomedical applications. Synthetic hydrogels have been designed to respond to various stimuli, but mechanical signals have not incorporated into hydrogel matrices. Because most tissues in the body are subjected to various types of mechanical forces, and cells within these tissues have sophisticated mechano-transduction machinery, this thesis is focused on developing hydrogel materials with built-in mechano-sensing mechanisms for use as tissue engineering scaffolds or drug release devices. Self-assembled block copolymer micelles (BCMs) with reactive handles were employed as the nanoscopic crosslinkers for the construction of covalently crosslinked networks. BCMs were assembled from amphiphilic diblock copolymers of poly(n-butyl acrylate) and poly(acrylic acid) partially modified with acrylate. Radical polymerization of acrylamide in the presence of micellar crosslinkers gave rise to elastomeric hydrogels whose mechanical properties can be tuned by varying the BCM composition and concentration. TEM imaging revealed that the covalently integrated BCMs underwent strain-dependent reversible deformation. A model hydrophobic drug, pyrene, loaded into the core of BCMs prior to the hydrogel formation, was dynamically released in response to externally applied mechanical forces, through force-induced reversible micelle deformation and the penetration of water molecules into the micelle core. The mechano-responsive hydrogel has been studied for tissue repair and regeneration purposes. Glycidyl methacrylate (GMA)-modified hyaluronic acid (HA) was photochemically crosslinked in the presence of dexamethasone (DEX)-loaded crosslinkable BCMs. The resultant HA gels (HAxBCM) contain covalently integrated micellar compartments with DEX being sequestered in the hydrophobic core. Compared

  3. Polysaccharide-Based Micelles for Drug Delivery

    Directory of Open Access Journals (Sweden)

    Nan Zhang

    2013-05-01

    Full Text Available Delivery of hydrophobic molecules and proteins has been an issue due to poor bioavailability following administration. Thus, micelle carrier systems are being investigated to improve drug solubility and stability. Due to problems with toxicity and immunogenicity, natural polysaccharides are being explored as substitutes for synthetic polymers in the development of new micelle systems. By grafting hydrophobic moieties to the polysaccharide backbone, self-assembled micelles can be readily formed in aqueous solution. Many polysaccharides also possess inherent bioactivity that can facilitate mucoadhesion, enhanced targeting of specific tissues, and a reduction in the inflammatory response. Furthermore, the hydrophilic nature of some polysaccharides can be exploited to enhance circulatory stability. This review will highlight the advantages of polysaccharide use in the development of drug delivery systems and will provide an overview of the polysaccharide-based micelles that have been developed to date.

  4. Structure and dynamics of glycosphingolipid micelles

    International Nuclear Information System (INIS)

    Disialoganglioside (GD1a) is one of the functional lipids involved in various surface events on biological cells. In order to clarify a relation between the structural feature and dynamics of the GD1a micelle depending on temperature elevation, we have carried out neutron spin echo (NSE) and synchrotron radiation small-angle X-ray scattering (SR-SAXS) measurements. We have found that the change of the dynamics of the micelle is coupled with the dehydration of ganglioside headgroups. (author)

  5. Electrosorption of pectin onto casein micelles

    OpenAIRE

    Tuinier, R.; Rolin, C.; de Kruif, C.G.

    2002-01-01

    Pectin, a polysaccharide derived from plant cells of fruit, is commonly used as stabilizer in acidified milk drinks. To gain a better understanding of the way that pectin stabilizes these drinks, we studied the adsorption and layer thickness of pectin on casein micelles in skim milk dispersions. Dynamic light scattering was used to measure the layer thickness of adsorbed pectin onto casein micelles in situ during acidification. The results indicate that the adsorption of pectin onto casein mi...

  6. Casein Micelle Dispersions under Osmotic Stress

    OpenAIRE

    Bouchoux, Antoine; Cayemitte, Pierre-Emerson; Jardin, Julien; Gésan-Guiziou, Geneviève; Cabane, Bernard

    2009-01-01

    Casein micelles dispersions have been concentrated and equilibrated at different osmotic pressures using equilibrium dialysis. This technique measured an equation of state of the dispersions over a wide range of pressures and concentrations and at different ionic strengths. Three regimes were found. i), A dilute regime in which the osmotic pressure is proportional to the casein concentration. In this regime, the casein micelles are well separated and rarely interact, whereas the osmotic press...

  7. Oseltamivir-conjugated polymeric micelles prepared by RAFT living radical polymerization as a new active tumor targeting drug delivery platform.

    Science.gov (United States)

    Kapishon, Vitaliy; Allison, Stephanie; Whitney, Ralph A; Cunningham, Michael F; Szewczuk, Myron R; Neufeld, Ronald J

    2016-02-23

    Targeted drug delivery using polymeric nanostructures has been at the forefront of cancer research, engineered for safer, more efficient and effective use of chemotherapy. Here, we designed a new polymeric micelle delivery system for active tumor targeting followed by micelle-drug internalization via receptor-induced endocytosis. We recently reported that oseltamivir phosphate targets and inhibits Neu1 sialidase activity associated with receptor tyrosine kinases such as epidermal growth factor receptors (EGFRs) which are overexpressed in cancer cells. By decorating micelles with oseltamivir, we investigated whether they actively targeted human pancreatic PANC1 cancer cells. Amphiphilic block copolymers with oseltamivir conjugated at the hydrophilic end, oseltamivir-pPEGMEMA-b-pMMA (oseltamivir-poly(polyethylene glycol methyl ether methacrylate)-block-poly(methyl methacrylate), were synthesized using reversible addition-fragmentation chain transfer (RAFT) living radical polymerization. Oseltamivir-conjugated micelles have self-assembling properties to give worm-like micellar structures with molecular weight of 80 000 g mol(-1). Oseltamivir-conjugated water soluble pPEGMEMA, dose dependently, both inhibited sialidase activity associated with Neu1, and reduced viability of PANC1 cells. In addition, oseltamivir-conjugated micelles, labelled with a hydrophobic fluorescent dye within the micelle core, were subsequently internalized by PANC1 cells. Blocking cell surface Neu1 with anti-Neu1 antibody, reduced internalization of oseltamivir-conjugated micelles, demonstrating that Neu1 binding linked to sialidase inhibition were prerequisite steps for subsequent internalization of the micelles. The mechanism of internalization is likely that of receptor-induced endocytosis demonstrating potential as a new nanocarrier system for not only targeting a tumor cell, but also for directly reducing viability through Neu1 inhibition, followed by intracellular delivery of hydrophobic

  8. A synthesis of AOT40-based response functions and critical levels of ozone for agricultural and horticultural crops

    Science.gov (United States)

    Mills, G.; Buse, A.; Gimeno, B.; Bermejo, V.; Holland, M.; Emberson, L.; Pleijel, H.

    Crop-response data from over 700 published papers and conference proceedings have been analysed with the aim of establishing ozone dose-response functions for a wide range of European agricultural and horticultural crops. Data that met rigorous selection criteria (e.g. field-based, ozone concentrations within European range, full season exposure period) were used to derive AOT40-yield response functions for 19 crops by first converting the published ozone concentration data into AOT40 (AOT40 is the hourly mean ozone concentration accumulated over a threshold ozone concentration of 40 ppb during daylight hours, units ppm h). For any individual crop, there were no significant differences in the linear response functions derived for experiments conducted in the USA or Europe, or for individual cultivars. Three statistically independent groups were identified: ozone sensitive crops (wheat, water melon, pulses, cotton, turnip, tomato, onion, soybean and lettuce); moderately sensitive crops (sugar beet, potato, oilseed rape, tobacco, rice, maize, grape and broccoli) and ozone resistant (barley and fruit represented by plum and strawberry). Critical levels of a 3 month AOT40 of 3 ppm h and a 3.5 month AOT40 of 6 ppm h were derived from the functions for wheat and tomato, respectively.

  9. Molar volumes of mixed micelles as a measure of nonideality of mixing of micelles

    Energy Technology Data Exchange (ETDEWEB)

    Funasaki, N.; Hada, S.

    1982-06-24

    Partial molar volumes of mixed micelles for the pentaoxyethylene glycol dodecyl ether (DE5)-heptaoxyethylene glycol dodecyl ether (DE7) and octaoxyethylene glycol dodecyl ether (DE8)-methyl P-hydroxybenzoate (MP) systems are determined from the densities of solutions of 2 surfactants kept at a fixed molar ratio and at concentrations much higher than the critical micelle concentration. Values for the partial molar volumes of the anionic fluorocarbon surfactant (NF)-sodium tetradecyl sulfate (STS) system are determined in a similar fashion but for a constant micellar composition. When micelles of DE5 and DE7 mix, the volume changes Delta V are zero. The Delta V values of the DE8-MP system are negative, whereas those of the NF-STS system are positive. The Delta V values of the NF-STS system change linearly with the mole fraction of STS in micelles, indicating that 2 kinds of mixed micelles coexist in this region. 40 references.

  10. Fluorescence resonance energy transfer in AOT/4-chlorophenol/m-xylene organogels

    Energy Technology Data Exchange (ETDEWEB)

    Dandapat, Manika; Mandal, Debabrata, E-mail: dmandal.chemistry@gmail.com

    2015-06-15

    Fluorescence Resonance Energy Transfer (FRET) between donor coumarins (C102 and C153) and acceptor Rhodamine 6G were studied in AOT/4-chlorophenol/m-xylene organogels. The gel comprises a three-dimensional network of fiber bundles trapping the m-xylene solvent. Each fiber is an aggregate of several strands, and each strand consists of a central columnar stack of the phenols, surrounded by AOT headgroups. Our acceptor is ionic so that it was concentrated near the polar center of the strand, while the neutral donors were likely distributed over a wider region. With C153 as donor, clear evidence of FRET (time-constant~100 ps) was found, which indicated that the donor and acceptor may reside in neighboring strands within the same fiber. However, with C102 as donor, FRET probably occurred over an ultrashort, sub-picosecond time-scale suggesting that the donor and acceptor in this case resided in close vicinity. Thus, C102 tends to localize near the polar centre of the strands, compared to the more hydrophobic C153, which prefers to occupy the relatively non-polar peripheral regions of the strands and fibers. - Highlights: • FRET between coumarin donors and Rhodamine 6G acceptor studied in AOT organogels. • With Coumarin 153 donor, a ~100 ps FRET component detected in both donor and acceptor fluorescence. • With Coumarin 102 donor, FRET component too short to be detected with a time-resolution of ~70 ps. • The FRET rates reveal crucial differences in donor–acceptor distances for the two coumarin donors.

  11. Preparation and Characterization of Nanosized Hydroxyapatite Particles in AOT Inverse Microemulsion

    Institute of Scientific and Technical Information of China (English)

    REN Wei; LI Shi-pu; WANG You-fa; CAO Xian-ying; CHEN Xiao-ming

    2004-01-01

    Nanosized particles of hydroxyapatite (HAP) were synthesized by reacting Ca(H2PO4)2*H2O solution complex with equimolar Ca(OH)2 saturated solution in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane water-in-oil microemulsion.The formation of microemulsion strongly depended on water content w (w=[H2O]/[AOT] molar ratio) and concentration of surfactant and cosurfactant (1-octanol).By the variety of conductivity with w and the partial ternary phase diagram derived from a series of demarcation points,we set the basic component of microemulsions:[AOT]=0.1M(mol/dm3),[1-octanol]=0.1M and w=3-9.Dynamic light scattering (DLS),UV-visible absorbance,TEM analysis and X-ray diffraction were used to characterize the microemulsion,formation of particles and resulting HAP particles.At low water content(w<9),the water pool radius of the droplet in the Ca(H2PO4)2*H2O microemulsion lineally depended on w.The size of final HAP particles was strongly affected by water content w and reactant concentration.With increasing water content w from 3 to 9,the size of HAP particles increased from 10-20nm to 40-50 nm at reactant concentration [Ca(H2PO4)2*H2O]=12×10-3 mol/dm3.The resulting HAP particles were poorly crystallized and spherical in morphology.

  12. Folding Behaviors of Protein (Lysozyme) Confined in Polyelectrolyte Complex Micelle.

    Science.gov (United States)

    Wu, Fu-Gen; Jiang, Yao-Wen; Chen, Zhan; Yu, Zhi-Wu

    2016-04-19

    The folding/unfolding behavior of proteins (enzymes) in confined space is important for their properties and functions, but such a behavior remains largely unexplored. In this article, we reported our finding that lysozyme and a double hydrophilic block copolymer, methoxypoly(ethylene glycol)5K-block-poly(l-aspartic acid sodium salt)10 (mPEG5K-b-PLD10), can form a polyelectrolyte complex micelle with a particle size of ∼30 nm, as verified by dynamic light scattering and transmission electron microscopy. The unfolding and refolding behaviors of lysozyme molecules in the presence of the copolymer were studied by microcalorimetry and circular dichroism spectroscopy. Upon complex formation with mPEG5K-b-PLD10, lysozyme changed from its initial native state to a new partially unfolded state. Compared with its native state, this copolymer-complexed new folding state of lysozyme has different secondary and tertiary structures, a decreased thermostability, and significantly altered unfolding/refolding behaviors. It was found that the native lysozyme exhibited reversible unfolding and refolding upon heating and subsequent cooling, while lysozyme in the new folding state (complexed with the oppositely charged PLD segments of the polymer) could unfold upon heating but could not refold upon subsequent cooling. By employing the heating-cooling-reheating procedure, the prevention of complex formation between lysozyme and polymer due to the salt screening effect was observed, and the resulting uncomplexed lysozyme regained its proper unfolding and refolding abilities upon heating and subsequent cooling. Besides, we also pointed out the important role the length of the PLD segment played during the formation of micelles and the monodispersity of the formed micelles. Furthermore, the lysozyme-mPEG5K-b-PLD10 mixtures prepared in this work were all transparent, without the formation of large aggregates or precipitates in solution as frequently observed in other protein

  13. High-pressure cloud point data for the system glycerol + olive oil + n-butane + AOT

    OpenAIRE

    J. P. Bender; A. Junges; Franceschi, E.; F. C. Corazza; C. Dariva; J. Vladimir Oliveira; M. L. Corazza

    2008-01-01

    This work reports high-pressure cloud point data for the quaternary system glycerol + olive oil + n-butane + AOT surfactant. The static synthetic method, using a variable-volume view cell, was employed for obtaining the experimental data at pressures up to 27 MPa. The effects of glycerol/olive oil concentration and surfactant addition on the pressure transition values were evaluated in the temperature range from 303 K to 343 K. For the system investigated, vapor-liquid (VLE), liquid-liquid (L...

  14. Synthesis and optical proper ties of nanosized CdS prepared in a quaternary CTAB/ n-hexanol/n-heptane/waterreverse micelle

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Quaternary water-in-oil reverse micelles consisting of cetyltrimethylammonium bromide (CTAB), nhexanol, n-heptane and water were prepared and characterized. The optimized reaction conditions were determined,and monodispersed droplets of the reverse micelles were used as microreactors to synthesize CdS nanoparticles. By using transmission electron microscopy (TEM), UV-Vis spectroscopy and fluorescence spectroscopy, the influences of the reverse micelle components on the size, size distribution,morphology, stability and optical properties of CdS nanoparticles were investigated. CdS nanoparticles with narrow size distribution were obtained and the size range is 6-8 nm when W=24 (W=[water]/[CTAB]), P=5.27 (P=[n-hexanol]/ [CTAB]), [CTAB]=0.2 mol/L, [Cd2+] and [S2] are 8.45×10-4 mol/L.

  15. Structural properties of self-assembled polymeric micelles

    DEFF Research Database (Denmark)

    Mortensen, K.

    1998-01-01

    At present, the thermodynamic understanding of complex copolymer systems is undergoing important developments. Block copolymers aggregate in selective solvents into micelles of various form and size depending on molecular architecture and interaction parameters. The micelles constitute the basis ...

  16. Efficient deacylation of N-acylimidazoles by functionalized surfactant micelles

    OpenAIRE

    Ihara, Yasuji; Nango, Mamoru; Koga, Joichi; ナンゴ, マモル; 南後, 守

    1989-01-01

    Hydroxylated surfactant micelles are powerful catalysts for the deacylation of N-acylimidazoles under neutral conditions; the deacylation rates of hydrophobia acylimidazoles are accelerated remarkably by functionalized micelles containing three hydroxy groups at the polar head.

  17. Risk assessments for forest trees: The performance of the ozone flux versus the AOT concepts

    Energy Technology Data Exchange (ETDEWEB)

    Karlsson, P.E. [Swedish Environmental Research Institute (IVL), PO Box 5302, S-400 14, Goeteborg (Sweden)]. E-mail: pererik.karlsson@ivl.se; Braun, S. [Institute for Applied Plant Biology, Schoenenbuch (Switzerland); Broadmeadow, M. [Environmental Research Branch, Forest Research Station, Alice Holt Lodge, Wrecclesham, Farnham, Surrey, GU10 4LH (United Kingdom); Elvira, S. [Ecotoxicidad de la Contaminacion Atmosferica, CIEMAT (ed 70), Avda. Complutense 22, 28040 Madrid (Spain); Emberson, L. [Stockholm Environment Institute at York, Box 373, University of York, York, YO10 5DD (United Kingdom); Gimeno, B.S. [Ecotoxicidad de la Contaminacion Atmosferica, CIEMAT (ed 70), Avda. Complutense 22, 28040 Madrid (Spain); Le Thiec, D. [I.N.R.A. Centre de Recherches Forestieres, UMR Ecologie et Ecophysiologie Forestieres Equipe Bioclimatologie, 54280 Champenoux (France); Novak, K. [WSL, Swiss Federal Research Institute, Zuercherstrasse 111, 8903 Birmensdorf (Switzerland); Oksanen, E. [Department of Biology, University of Joensuu, POB 111, 80101 Joensuu (Finland); Schaub, M. [WSL, Swiss Federal Research Institute, Zuercherstrasse 111, 8903 Birmensdorf (Switzerland); Uddling, J. [Department of Plant and Environmental Sciences, Goeteborg University, PO Box 461, SE-405 30 Goeteborg (Sweden); Wilkinson, M. [Environmental Research Branch, Forest Research Station, Alice Holt Lodge, Wrecclesham, Farnham, Surrey, GU10 4LH (United Kingdom)

    2007-04-15

    Published ozone exposure-response relationships from experimental studies with young trees performed at different sites across Europe were re-analysed in order to test the performance of ozone exposure indices based on AOTX (Accumulated exposure Over a Threshold of X nmol mol{sup -1}) and AF{sub st}Y (Accumulated Stomatal Flux above a threshold of Y nmol m{sup -2} s{sup -1}). AF{sub st}1.6 was superior, as compared to AOT40, for explaining biomass reductions, when ozone sensitive species with differing leaf morphology were included in the analysis, while this was not the case for less sensitive species. A re-analysis of data with young black cherry trees, subject to different irrigation regimes, indicated that leaf visible injuries were more strongly related to the estimated stomatal ozone uptake, as compared to the ozone concentration in the air. Experimental data with different clones of silver birch indicated that leaf thickness was also an important factor influencing the development of ozone induced leaf visible injury. - Ozone stomatal flux based indices were superior, as compared to AOT40, for explaining biomass reductions and leaf visible injury.

  18. Risk assessments for forest trees: The performance of the ozone flux versus the AOT concepts

    International Nuclear Information System (INIS)

    Published ozone exposure-response relationships from experimental studies with young trees performed at different sites across Europe were re-analysed in order to test the performance of ozone exposure indices based on AOTX (Accumulated exposure Over a Threshold of X nmol mol-1) and AFstY (Accumulated Stomatal Flux above a threshold of Y nmol m-2 s-1). AFst1.6 was superior, as compared to AOT40, for explaining biomass reductions, when ozone sensitive species with differing leaf morphology were included in the analysis, while this was not the case for less sensitive species. A re-analysis of data with young black cherry trees, subject to different irrigation regimes, indicated that leaf visible injuries were more strongly related to the estimated stomatal ozone uptake, as compared to the ozone concentration in the air. Experimental data with different clones of silver birch indicated that leaf thickness was also an important factor influencing the development of ozone induced leaf visible injury. - Ozone stomatal flux based indices were superior, as compared to AOT40, for explaining biomass reductions and leaf visible injury

  19. Ambient ozone phytotoxic potential over the Czech forests as assessed by AOT40

    Directory of Open Access Journals (Sweden)

    Hunova I

    2012-06-01

    Full Text Available Ambient ozone (O3 represents one of the most prominent air pollution pro­blems in Europe. We present an analysis on O3 with respect to its phytotoxic potential over Czech forests between 1994 and 2008. The phytotoxic potential is estimated based on the exposure index AOT40 for forests calculated from real-time monitoring data at 24 rural sites. Our results indicate high phytotoxic potential for most of the Czech Republic (CR with considerable inter-annual and spatial variability. The highest AOT40 values were 38-39 ppm·h. The cri­tical level for forest protection (5 ppm·h was usually exceeded early in the growing season, generally in May. In years with meteorological conditions conducive to ozone formation, the critical level was exceeded by 5-7 folds as compared to years with non-conducive conditions; nevertheless, all sites consi­stently exceeded the critical level since 1994. In the extremely hot and dry year 2003, the critical level for forests was exceeded over 31 % of the Czech forested area. More research is needed to translate these exceedances into forest injury in the CR.

  20. Dynamics of SDS Micelles: Neutron Scattering Study

    Science.gov (United States)

    Sharma, V. K.; Mitra, S.; Verma, G.; Hassan, P. A.; Sakai, V. Garcia; Mukhopadhyay, R.

    2011-07-01

    Here we report dynamics of Sodium Dodecyl Sulphate (SDS) micelles as investigated by high-resolution incoherent quasielastic neutron scattering technique. Data analysis clearly shows the presence of two distinct motions namely global diffusion of the micelles and faster internal motion of the SDS monomer. The global diffusion is found to be Fickian in nature and the corresponding diffusion coefficient is consistent with those obtained from dynamic light scattering measurements. Internal motion of the micelles is described by a localized translational motion in which hydrogen atoms closer to the head group move within smaller spheres with lower diffusion constant compared to the hydrogen atoms away from head group, suggesting more flexibility and faster movement of the chain away from the head group.

  1. Structure and dynamics of glycosphingolipid micelles

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, Mitsuhiro; Iwase, Hiroki; Hayakawa, Tomohiro [Department of Physics, Gunma University, Maebashi, Gunma (Japan)

    2001-03-01

    Disialoganglioside (G{sub D1a}) is one of the functional lipids involved in various surface events on biological cells. In order to clarify a relation between the structural feature and dynamics of the G{sub D1a} micelle depending on temperature elevation, we have carried out neutron spin echo (NSE) and synchrotron radiation small-angle X-ray scattering (SR-SAXS) measurements. We have found that the change of the dynamics of the micelle is coupled with the dehydration of ganglioside headgroups. (author)

  2. Statistical crystallography of surface micelle spacing

    Science.gov (United States)

    Noever, David A.

    1992-01-01

    The aggregation of the recently reported surface micelles of block polyelectrolytes is analyzed using techniques of statistical crystallography. A polygonal lattice (Voronoi mosaic) connects center-to-center points, yielding statistical agreement with crystallographic predictions; Aboav-Weaire's law and Lewis's law are verified. This protocol supplements the standard analysis of surface micelles leading to aggregation number determination and, when compared to numerical simulations, allows further insight into the random partitioning of surface films. In particular, agreement with Lewis's law has been linked to the geometric packing requirements of filling two-dimensional space which compete with (or balance) physical forces such as interfacial tension, electrostatic repulsion, and van der Waals attraction.

  3. Fabrication of multiresponsive shell cross-linked micelles possessing pH-controllable core swellability and thermo-tunable corona permeability.

    Science.gov (United States)

    Jiang, Xiaoze; Ge, Zhishen; Xu, Jian; Liu, Hao; Liu, Shiyong

    2007-10-01

    A double hydrophilic ABC triblock copolymer, poly(2-(diethylamino)ethyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(N-isopropylacrylamide) (PDEA-b-PDMA-b-PNIPAM), containing the well-known pH-responsive PDEA block and thermoresponsive PNIPAM block, was synthesized by atom transfer radical polymerization via sequential monomer addition using ethyl 2-chloropropionate as the initiator. The obtained triblock copolymer exhibits interesting "schizophrenic" micellization behavior in aqueous solution, and supramolecularly self-assembles into three-layer "onion-like" PNIPAM-core micelles at acidic pH's and elevated temperatures and PDEA-core micelles with "inverted" structures at alkaline pH's and room temperature. In both cases, dynamic laser light scattering (LLS) and optical transmittance reveal the presence of near-monodisperse micelles, and the micelle formation/inversion process is fully reversible. Novel shell cross-linked (SCL) micelles with pH-responsive PDEA cores and thermoresponsive PNIPAM coronas were then facilely fabricated from the PDEA-b-PDMA-b-PNIPAM triblock copolymer by cross-linking the PDMA inner shells with 1,2-bis(2-iodoethoxy)ethane. The reversible pH-dependent swelling/shrinking of PDEA cores and thermosensitive collapse/aggregation of PNIPAM coronas of the obtained SCL micelles were investigated in detail by dynamic LLS, optical transmittance, and transmission electron microscopy. As the structurally stable SCL micelles possess pH-controllable core swellability and thermo-tunable corona permeability, the release profile of a model hydrophobic drug, dipyridamole, initially loaded within the hydrophobic PDEA core, can be dually controlled by both the solution pH and the temperature. This represents the first report of SCL micelles with multiresponsive cores and coronas, which may find practical applications in fields such as drug delivery and smart release. PMID:17887794

  4. PEG-PE-based micelles co-loaded with paclitaxel and cyclosporine A or loaded with paclitaxel and targeted by anticancer antibody overcome drug resistance in cancer cells.

    Science.gov (United States)

    Sarisozen, Can; Vural, Imran; Levchenko, Tatyana; Hincal, A Atilla; Torchilin, Vladimir P

    2012-05-01

    The over-expression of the P-glycoprotein (P-gp) in cancer cells is one of the main reasons of the acquired Multidrug Resistance (MDR). Combined treatment of MDR cancer cells with P-gp inhibitors and chemotherapeutic agents could result in reversal of resistance in P-gp-expressing cells. In this study, paclitaxel (PTX) was co-encapsulated in actively targeted (anticancer mAb 2C5-modified) polymeric lipid-core PEG-PE-based micelles with Cyclosporine A (CycA), which is one of the most effective first generation P-gp inhibitors. Cell culture studies performed using MDCKII (parental and MDR1) cell lines to investigate the potential MDR reversal effect of the formulations. The average size of both empty and loaded PEG₂₀₀₀-PE/Vitamin E mixed micelles was found between 10 and 25 nm. Zeta potentials of the formulations were found between -7 and -35 mV. The percentage of PTX in the micelles was found higher than 3% for both formulations and cumulative PTX release of about 70% was demonstrated. P-gp inhibition with CycA caused an increase in the cytotoxicity of PTX. Dual-loaded micelles demonstrated significantly higher cytotoxicity in the resistant MDCKII-MDR1 cells than micelles loaded with PTX alone. Micelle modification with mAb 2C5 results in the highest cytotoxicity against resistant cells, with or without P-gp modulator, probably because of better internalization bypassing the P-gp mechanism. Our results suggest that micelles delivering a combination of P-gp modulator and anticancer drug or micelles loaded with only PTX, but targeted with mAb 2C5 represent a promising approach to overcome drug resistance in cancer cells. PMID:22506922

  5. Micelle depletion-induced vs. micelle-mediated aggregation in nanoparticles

    International Nuclear Information System (INIS)

    The phase behavior anionic silica nanoparticle (Ludox LS30) with non-ionic surfactants decaethylene glycol monododecylether (C12E10) and cationic dodecyltrimethyl ammonium bromide (DTAB) in aqueous electrolyte solution has been studied by small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations of nanoparticle (1 wt%), surfactants (1 wt%) and electrolyte (0.1 M NaCl). Each of these nanoparticle–surfactant systems has been examined for different contrast conditions where individual components (nanoparticle or surfactant) are made visible. It is observed that the nanoparticle-micelle system in both the cases lead to the aggregation of nanoparticles. The aggregation is found to be micelle depletion-induced for C12E10 whereas micelle-mediated aggregation for DTAB. Interestingly, it is also found that phase behavior of mixed surfactant (C12E10 + DTAB) system is similar to that of C12E10 (unlike DTAB) micelles with nanoparticles

  6. AOT-based microemulsions accelerate the 1,3-cycloaddition of benzonitrile oxide to N-ethylmaleimide

    NARCIS (Netherlands)

    Engberts, J. B. F. N.; Fernandez, E.; Garcia-Rio, L.; Leis, J. R.

    2006-01-01

    We studied the 1,3-dipolar cycloaddition of benzonitrile oxide to N-ethylmaleimide in AOT/isooctane/water microemulsions at 25.0 degrees C and found the reaction rate to be roughly 150 and 35 times greater than that in isooctane and pure water, respectively. The accelerating effect of the microemuls

  7. Comparison of Contrast Reduction based MODIS AOT estimates with AERONET measurements

    Science.gov (United States)

    Grosso, Nuno; Paronis, Dimitris

    2010-05-01

    Satellite remote sensing of aerosols offers global and seasonal coverage of aerosol distribution patterns resolving the spatial and temporal heterogeneities introduced by the existence of different sources and thus providing a more accurate and continuous quantification and characterization of the presence of aerosols in the atmosphere. Several retrieval methods have been implemented for various satellite sensors on an operational basis, providing global standard aerosol products such as Aerosol Optical Depth (AOD) and particle size related parameters. Current techniques such as dark pixel reflectance (MODIS, MERIS), multi-angle reflectance analysis (MISR, AATSR) or quantification of light polarisation by aerosols (POLDER) rely on known surface reflectance behaviours (e.g., low surface reflective bands or low sensitivity to polarised light) to separate the surface from the atmospheric signal by first modelling surface contribution. Their accuracy and has a limited application for highly reflective or heterogeneous surfaces such as urban, desert or snow covered areas. Another set of algorithms, the so-called Contrast Reduction based algorithms, might complement information given since their principle is based on the existence of a time invariant heterogeneous surface that allows AOT retrieval by measuring the contrast differences between a pair of images with similar viewing geometry. This paper presents the results of applying a contrast reduction based algorithm to a one year dateaset of MODIS images and comparing it to the AOT measurements of five European urban influenced AERONET stations (Barcelona, Cabo da Roca, Lille, Modena, Paris). Results demonstrate a high correlation (r=0.8, =0.05 and rmse=0.08) between the MODIS contrast reduction derived AOT results and the AERONET measurements, although a systematic overestimation is observed. The error analysis further shows sensitivity to observation geometry, time-lag between reference and polluted images

  8. Influence of succinylation on the conformation of yak casein micelles.

    Science.gov (United States)

    Yang, Min; Cui, Na; Fang, Yan; Shi, Ying; Yang, Jitao; Wang, Jiangyu

    2015-07-15

    Succinylation modifies the physicochemical characteristics and improves the functional properties of proteins. This study assessed the effects of succinylation on the conformation of yak casein micelles with seven degree of modification. The results revealed that succinylation contributed to the dissociation of casein micelles. With the increase of succinylated degree, soluble nitrogen and minerals content increased, while casein micelle size and polydispersity index of micelles decreased. Succinylation affected the spatial conformation of yak casein micelles: turn decreased, ß-sheet and α-helix increased, and irregular structure were non-significantly affected. The intrinsic and ANS fluorescence intensity decreased and the maximum emission wavelength shifted red with increasing succinylation. Based on the results, the structure of yak casein micelles was characteristic of the sub-micelle model. PMID:25722161

  9. A facile surfactant critical micelle concentration determination

    OpenAIRE

    Cai, Lifeng; Gochin, Miriam; Liu, Keliang

    2011-01-01

    Liquid surface curvature variations in microplate wells due to different liquid surface tension cause significant signal change in spectroscopic measurement using a plate reader with a vertical detecting light beam. The signals have been quantitated and used to develop a method for facile surfactant critical micelle concentration determination.

  10. Spontaneous symmetry breaking: formation of Janus micelles

    NARCIS (Netherlands)

    Voets, I.K.; Fokkink, R.G.; Hellweg, T.; King, S.M.; Waard, de P.; Keizer, de A.; Cohen Stuart, M.A.

    2009-01-01

    We describe the preparation and solution properties of Janus micelles, i.e., non-centrosymmetric nanoparticles with compartmentalized shells, via co-assembly of two fully water-soluble block copolymers. They consist of a mixed core of poly(N-methyl-2-vinyl pyridinium iodide) (P2MVP) and poly(acrylic

  11. Antibacterial polyelectrolyte micelles for coating stainless steel.

    Science.gov (United States)

    Falentin-Daudré, Céline; Faure, Emilie; Svaldo-Lanero, Tiziana; Farina, Fabrice; Jérôme, Christine; Van De Weerdt, Cécile; Martial, Joseph; Duwez, Anne-Sophie; Detrembleur, Christophe

    2012-05-01

    In this study, we report on the original synthesis and characterization of novel antimicrobial coatings for stainless steel by alternating the deposition of aqueous solutions of positively charged polyelectrolyte micelles doped with silver-based nanoparticles with a polyanion. The micelles are formed by electrostatic interaction between two oppositely charged polymers: a polycation bearing 3,4-dihydroxyphenylalanine units (DOPA, a major component of natural adhesives) and a polyanion (poly(styrene sulfonate), PSS) without using any block copolymer. DOPA units are exploited for their well-known ability to anchor to stainless steel and to form and stabilize biocidal silver nanoparticles (Ag(0)). The chlorine counteranion of the polycation forms and stabilizes biocidal silver chloride nanoparticles (AgCl). We demonstrate that two layers of micelles (alternated by PSS) doped with silver particles are enough to impart to the surface strong antibacterial activity against gram-negative E. coli. Moreover, micelles that are reservoirs of biocidal Ag(+) can be easily reactivated after depletion. This novel water-based approach is convenient, simple, and attractive for industrial applications. PMID:22506542

  12. Casein micelles and their internal structure

    Energy Technology Data Exchange (ETDEWEB)

    De Kruif, Cornelis G [ORNL; Huppertz, Thom [NIZO Food Research; Urban, Volker S [ORNL; Petukhov, Andrei V [Van ' t Hoff laboratory for Physical and Colloid Chemistry, Utrecht University, The Netherlands

    2012-01-01

    The internal structure of casein micelles was studied by calculating the small-angle neutron and X-ray scattering and static light scattering spectrum (SANS, SAXS, SLS) as a function of the scattering contrast and composition. We predicted experimental SANS, SAXS, SLS spectra self consistently using independently determined parameters for composition size, polydispersity, density and voluminosity. The internal structure of the casein micelles, i.e. how the various components are distributed within the casein micelle, was modeled according to three different models advocated in the literature; i.e. the classical sub-micelle model, the nanocluster model and the dual binding model. In this paper we present the essential features of these models and combine new and old experimental SANS, SAXS, SLS and DLS scattering data with new calculations that predict the spectra. Further evidence on micellar substructure was obtained by internally cross linking the casein micelles using transglutaminase, which led to casein nanogel particles. In contrast to native casein micelles, the nanogel particles were stable in 6 M urea and after sequestering the calcium using trisodium citrate. The changed scattering properties were again predicted self consistently. An important result is that the radius of gyration is independent of contrast, indicating that the mass distribution within a casein micelle is homogeneous. Experimental contrast is predicted quite well leading to a match point at a D{sub 2}O volume fraction of 0.41 ratio in SANS. Using SANS and SAXS model calculations it is concluded that only the nanocluster model is capable of accounting for the experimental scattering contrast variation data. All features and trends are predicted self consistently, among which the 'famous' shoulder at a wave vector value Q = 0.35 nm{sup -1}. In the nanocluster model, the casein micelle is considered as a (homogeneous) matrix of caseins in which the colloidal calcium phosphate (CCP

  13. Smart micelle@polydopamine core-shell nanoparticles for highly effective chemo-photothermal combination therapy

    Science.gov (United States)

    Zhang, Ruirui; Su, Shishuai; Hu, Kelei; Shao, Leihou; Deng, Xiongwei; Sheng, Wang; Wu, Yan

    2015-11-01

    In this investigation, we have designed and synthesized a novel core-shell polymer nanoparticle system for highly effective chemo-photothermal combination therapy. A nanoscale DSPE-PEG micelle encapsulating doxorubicin (Dox-M) was designed as a core, and then modified by a polydopamine (PDA) shell for photothermal therapy and bortezomib (Btz) administration (Dox-M@PDA-Btz). The facile conjugation of Btz to the catechol-containing PDA shell can form a reversible pH-sensitive boronic acid-catechol conjugate to create a stimuli-responsive drug carrier system. As expected, the micelle@PDA core-shell nanoparticles exhibited satisfactory photothermal efficiency, which has potential for thermal ablation of malignant tissues. In addition, on account of the PDA modification, both Dox and Btz release processes were pH-dependent and NIR-dependent. Both in vitro and in vivo studies illustrated that the Dox-M@PDA-Btz nanoparticles coupled with laser irradiation could enhance the cytotoxicity, and thus combinational therapy efficacy was achieved when integrating Dox, Btz, and PDA into a single nanoplatform. Altogether, our current study indicated that the micelle@polydopamine core-shell nanoparticles could be applied for NIR/pH-responsive sustained-release and synergized chemo-photothermal therapy for breast cancer.In this investigation, we have designed and synthesized a novel core-shell polymer nanoparticle system for highly effective chemo-photothermal combination therapy. A nanoscale DSPE-PEG micelle encapsulating doxorubicin (Dox-M) was designed as a core, and then modified by a polydopamine (PDA) shell for photothermal therapy and bortezomib (Btz) administration (Dox-M@PDA-Btz). The facile conjugation of Btz to the catechol-containing PDA shell can form a reversible pH-sensitive boronic acid-catechol conjugate to create a stimuli-responsive drug carrier system. As expected, the micelle@PDA core-shell nanoparticles exhibited satisfactory photothermal efficiency, which has

  14. High-pressure cloud point data for the system glycerol + olive oil + n-butane + AOT

    Directory of Open Access Journals (Sweden)

    J. P. Bender

    2008-09-01

    Full Text Available This work reports high-pressure cloud point data for the quaternary system glycerol + olive oil + n-butane + AOT surfactant. The static synthetic method, using a variable-volume view cell, was employed for obtaining the experimental data at pressures up to 27 MPa. The effects of glycerol/olive oil concentration and surfactant addition on the pressure transition values were evaluated in the temperature range from 303 K to 343 K. For the system investigated, vapor-liquid (VLE, liquid-liquid (LLE and vapor-liquid-liquid (VLLE equilibrium were recorded. It was experimentally observed that, at a given temperature and surfactant content, an increase in the concentration of glycerol/oil ratio led to a pronounced increase in the slope of the liquid-liquid coexistence curve. A comparison with results reported for the same system but using propane as solvent showed that much lower pressure transition values are obtained when using n-butane.

  15. Space charge limited release of charged inverse micelles in non-polar liquids.

    Science.gov (United States)

    Prasad, Manoj; Strubbe, Filip; Beunis, Filip; Neyts, Kristiaan

    2016-07-28

    Charged inverse micelles (CIMs) generated during a continuous polarizing voltage between electrodes in the model system of polyisobutylene succinimide in dodecane do not populate a diffuse double layer like CIMs present in equilibrium (regular CIMs), but instead end up in interface layers. When the applied voltage is reversed abruptly after a continuous polarizing voltage step, two peaks are observed in the transient current. The first peak is due to the release of regular CIMs from the diffuse double layers formed during the polarizing voltage step, which is understood on the basis of the Poisson-Nernst-Planck equations. The second peak is due to the release of a small fraction of generated negative CIMs from the interface layer. A model based on space charge limited release of the generated negative CIMs from the interface layer is presented and the results of the model are compared with several types of measurements. For the situation in which the bulk is deprived of regular CIMs and neutral inverse micelles, the results of the model are in agreement with the experimental results. However, for the situation in which regular CIMs and neutral inverse micelles are present, the model shows discrepancies with the experiment for high voltages and high charge contents. These discrepancies are attributed to electrohydrodynamic flow caused by local variations in the electric field at the vicinity of the electrodes, which occur during the reversal voltage. Also the long term decrease of the amount of released generated CIMs is studied and it is found that the presence of regular CIMs and neutral inverse micelles speeds up the decrease. This study provides a deeper insight in the electrodynamics of CIMs and is relevant for various applications in non-polar liquids. PMID:27374418

  16. Biodegradation of pesticides in nonionic water-in-oil microemulsions of tween 85: Relationship between micelle structure and activity.

    Science.gov (United States)

    Komives, C F; Lilley, E; Russell, A J

    1994-04-25

    Water-in-oil microemulsion systems have been studied in recent years for a number of applications in protein separation and enzymology. Although it is well established that reversed micelle systems provide an excellent medium for nonaqueous biocatalytic studies, there is still much speculation as to the interaction of the enzyme with the surfactant interface. Polyoxyethylene sorbitan trioleate (Tween 85) is a nonionic surfactant which has some interesting properties for microemulsion formation and protein solubilization. In conjunction with a separate article describing the structural features of Tween 85 reversed micelles in hexane with isopropanol as a cosurfactant, this work describes the activity of an enzyme, organophosphorus hydrolase, for degrading organophosphorus pesticides in this microemulsion system. Ternary phase diagrams were constructed to outline the phase boundaries at different temperatures and isopropanol concentrations, which elucidate the role of the cosurfactant alcohol, as well as some features of micelle structure. Kinetic and stability studies with organophosphorus hydrolase show the effect of enzyme partitioning between the micelle surfactant layer and aqueous core. (c) 1994 John Wiley & Sons, Inc. PMID:18615442

  17. Structural changes in block copolymer micelles induced by cosolvent mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, Elizabeth G.; Smart, Thomas P.; Jackson, Andrew J.; Sullivan, Millicent O.; Epps, III, Thomas H. (Delaware)

    2012-11-26

    We investigated the influence of tetrahydrofuran (THF) addition on the structure of poly(1,2-butadiene-b-ethylene oxide) [PB-PEO] micelles in aqueous solution. Our studies showed that while the micelles remained starlike, the micelle core-corona interfacial tension and micelle size decreased upon THF addition. The detailed effects of the reduction in interfacial tension were probed using contrast variations in small angle neutron scattering (SANS) experiments. At low THF contents (high interfacial tensions), the SANS data were fit to a micelle form factor that incorporated a radial density distribution of corona chains to account for the starlike micelle profile. However, at higher THF contents (low interfacial tensions), the presence of free chains in solution affected the scattering at high q and required the implementation of a linear combination of micelle and Gaussian coil form factors. These SANS data fits indicated that the reduction in interfacial tension led to broadening of the core-corona interface, which increased the PB chain solvent accessibility at intermediate THF solvent fractions. We also noted that the micelle cores swelled with increasing THF addition, suggesting that previous assumptions of the micelle core solvent content in cosolvent mixtures may not be accurate. Control over the size, corona thickness, and extent of solvent accessible PB in these micelles can be a powerful tool in the development of targeting delivery vehicles.

  18. Interaction of lactoferrin and lysozyme with casein micelles.

    Science.gov (United States)

    Anema, Skelte G; de Kruif, C G Kees

    2011-11-14

    On addition of lactoferrin (LF) to skim milk, the turbidity decreases. The basic protein binds to the caseins in the casein micelles, which is then followed by a (partial) disintegration of the casein micelles. The amount of LF initially binding to casein micelles follows a Langmuir adsorption isotherm. The kinetics of the binding of LF could be described by first-order kinetics and similarly the disintegration kinetics. The disintegration was, however, about 10 times slower than the initial adsorption, which allowed investigating both phenomena. Kinetic data were also obtained from turbidity measurements, and all data could be described with one equation. The disintegration of the casein micelles was further characterized by an activation energy of 52 kJ/mol. The initial increase in hydrodynamic size of the casein micelles could be accounted for by assuming that it would go as the cube root of the mass using the adsorption and disintegration kinetics as determined from gel electrophoresis. The results show that LF binds to casein micelles and that subsequently the casein micelles partly disintegrate. All micelles behave in a similar manner as average particle size decreases. Lysozyme also bound to the casein micelles, and this binding followed a Langmuir adsorption isotherm. However, lysozyme did not cause the disintegration of the casein micelles. PMID:21932853

  19. Structural changes in block copolymer micelles induced by cosolvent mixtures

    International Nuclear Information System (INIS)

    We investigated the influence of tetrahydrofuran (THF) addition on the structure of poly(1,2-butadiene-b-ethylene oxide) [PB-PEO] micelles in aqueous solution. Our studies showed that while the micelles remained starlike, the micelle core-corona interfacial tension and micelle size decreased upon THF addition. The detailed effects of the reduction in interfacial tension were probed using contrast variations in small angle neutron scattering (SANS) experiments. At low THF contents (high interfacial tensions), the SANS data were fit to a micelle form factor that incorporated a radial density distribution of corona chains to account for the starlike micelle profile. However, at higher THF contents (low interfacial tensions), the presence of free chains in solution affected the scattering at high q and required the implementation of a linear combination of micelle and Gaussian coil form factors. These SANS data fits indicated that the reduction in interfacial tension led to broadening of the core-corona interface, which increased the PB chain solvent accessibility at intermediate THF solvent fractions. We also noted that the micelle cores swelled with increasing THF addition, suggesting that previous assumptions of the micelle core solvent content in cosolvent mixtures may not be accurate. Control over the size, corona thickness, and extent of solvent accessible PB in these micelles can be a powerful tool in the development of targeting delivery vehicles.

  20. Preparation and Evaluation of Inhalable Itraconazole Chitosan Based Polymeric Micelles

    Directory of Open Access Journals (Sweden)

    Esmaeil Moazeni

    2012-12-01

    Full Text Available Background: This study evaluated the potential of chitosan based polymeric micelles as a nanocarrier system for pulmonary delivery of itraconazole (ITRA.Methods: Hydrophobically modified chitosan were synthesized by conjugation of stearic acid to the hydrophilic depolymerized chitosan. FTIR and 1HNMR were used to prove the chemical structure and physical properties of the depolymerized and the stearic acid grafted chitosan. ITRA was entrapped into the micelles and physicochemical properties of the micelles were investigated. Fluorescence spectroscopy, dynamic laser light scattering andtransmission electron microscopy were used to characterize the physicochemical properties of the prepared micelles. The in vitro pulmonary profile of polymeric micelles was studied by an air-jet nebulizer connected to a twin stage impinger.Results: The polymeric micelles prepared in this study could entrap up to 43.2±2.27 μg of ITRA per milliliter. All micelles showed mean diameter between 120–200 nm. The critical micelle concentration of the stearic acid grafted chitosan was found to be 1.58×10-2 mg/ml. The nebulization efficiency was up to 89% and the fine particle fraction (FPF varied from 38% to 47%. The micelles had enough stability to remain encapsulation of the drug during nebulization process.Conclusions: In vitro data showed that stearic acid grafted chitosan based polymeric micelles has a potential to be used as nanocarriers for delivery of itraconazole through inhalation.

  1. Implicit solvent simulations of DPC micelle formation.

    Science.gov (United States)

    Lazaridis, Themis; Mallik, Buddhadeb; Chen, Yong

    2005-08-11

    The formation of micelles by dodecylphosphocholine (DPC) is modeled by treating the surfactants in atomic detail and the solvent implicitly, in the spirit of the EEF1 solvation model for proteins. The solvation parameters of the DPC atoms are carried over from those of similar atoms in proteins. A slight adjustment of the parameters for the headgroup was found necessary for obtaining an aggregation number consistent with experiment. Molecular dynamics simulations of 960 DPC molecules at different concentrations are used to obtain the aggregation number, the micelle size distribution, and the CMC. At 20 mM concentration we obtain an aggregation number of 53-56 and a CMC of 1.25 mM, values close to the experimental ones. At 100 mM the aggregation number increases to 90. Simulations of individual micelles of varying size show that the effective energy per surfactant molecule is initially a decreasing function of aggregation number but stabilizes at about 60 molecules. The van der Waals term and the desolvation of nonpolar groups contribute to micellization, whereas the desolvation of polar groups opposes it. From the difference between the effective energy and the free energy (calculated from the CMC), the translational and rotational entropy contributions to the free energy are estimated at about 7 kcal/mol per monomer. The micelles obtained here are more irregular than those obtained in explicit water simulations. This modeling approach allows the study of larger surfactant aggregates for longer times and the extraction of thermodynamic in addition to structural information. PMID:16852911

  2. Thermoresponsive polymer micelles as potential nanosized cancerostatics

    Czech Academy of Sciences Publication Activity Database

    Laga, Richard; Janoušková, Olga; Ulbrich, Karel; Pola, Robert; Blažková, Jana; Filippov, Sergey K.; Etrych, Tomáš; Pechar, Michal

    2015-01-01

    Roč. 16, č. 8 (2015), s. 2493-2505. ISSN 1525-7797 R&D Projects: GA MŠk(CZ) EE2.3.30.0029; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 Keywords : RAFT polymerization * polymer therapeutics * thermo-responsive micelles Subject RIV: CE - Biochemistry Impact factor: 5.750, year: 2014

  3. Chain exchange in triblock copolymer micelles

    Science.gov (United States)

    Lu, Jie; Lodge, Timothy; Bates, Frank

    2015-03-01

    Block polymer micelles offer a host of technological applications including drug delivery, viscosity modification, toughening of plastics, and colloidal stabilization. Molecular exchange between micelles directly influences the stability, structure and access to an equilibrium state in such systems and this property recently has been shown to be extraordinarily sensitive to the core block molecular weight in diblock copolymers. The dependence of micelle chain exchange dynamics on molecular architecture has not been reported. The present work conclusively addresses this issue using time-resolved small-angle neutron scattering (TR-SANS) applied to complimentary S-EP-S and EP-S-EP triblock copolymers dissolved in squalane, a selective solvent for the EP blocks, where S and EP refer to poly(styrene) and poly(ethylenepropylene), respectively. Following the overall SANS intensity as a function of time from judiciously deuterium labelled polymer and solvent mixtures directly probes the rate of molecular exchange. Remarkably, the two triblocks display exchange rates that differ by approximately ten orders of magnitude, even though the solvophobic S blocks are of comparable size. This discovery is considered in the context of a model that successfully explains S-EP diblock exchange dynamics.

  4. Toward a Standard Protocol for Micelle Simulation.

    Science.gov (United States)

    Johnston, Michael A; Swope, William C; Jordan, Kirk E; Warren, Patrick B; Noro, Massimo G; Bray, David J; Anderson, Richard L

    2016-07-01

    In this paper, we present protocols for simulating micelles using dissipative particle dynamics (and in principle molecular dynamics) that we expect to be appropriate for computing micelle properties for a wide range of surfactant molecules. The protocols address challenges in equilibrating and sampling, specifically when kinetics can be very different with changes in surfactant concentration, and with minor changes in molecular size and structure, even using the same force field parameters. We demonstrate that detection of equilibrium can be automated and is robust, for the molecules in this study and others we have considered. In order to quantify the degree of sampling obtained during simulations, metrics to assess the degree of molecular exchange among micellar material are presented, and the use of correlation times are prescribed to assess sampling and for statistical uncertainty estimates on the relevant simulation observables. We show that the computational challenges facing the measurement of the critical micelle concentration (CMC) are somewhat different for high and low CMC materials. While a specific choice is not recommended here, we demonstrate that various methods give values that are consistent in terms of trends, even if not numerically equivalent. PMID:27096611

  5. The systematic tunability of nanoparticle dimensions through the controlled loading of surface-deposited diblock copolymer micelles.

    Science.gov (United States)

    Krishnamoorthy, S; Pugin, R; Hinderling, C; Brugger, J; Heinzelmann, H

    2008-04-30

    The continuous tunability of iron oxide nanoparticle dimensions is demonstrated using the pH controlled loading of ferric nitrate from aqueous solution into polystyrene-block-polyacrylic acid reverse micelles deposited on a silicon substrate. Quasi-hexagonally ordered two-dimensional arrays of iron oxide nanoparticles with a systematic tunability of particle heights in the sub-10 nm regime and a constant periodicity are obtained and characterized with atomic force microscopy and x-ray photoelectron spectroscopy. PMID:21825665

  6. The systematic tunability of nanoparticle dimensions through the controlled loading of surface-deposited diblock copolymer micelles

    OpenAIRE

    Krishnamoorthy, S; Pugin, R; Hinderling, C; Brugger, J.; Heinzelmann, H

    2008-01-01

    The continuous tunability of iron oxide nanoparticle dimensions is demonstrated using the pH controlled loading of ferric nitrate from aqueous solution into polystyrene–block–polyacrylic acid reverse micelles deposited on a silicon substrate. Quasi-hexagonally ordered two-dimensional arrays of iron oxide nanoparticles with a systematic tunability of particle heights in the sub-10 nm regime and a constant periodicity are obtained and characterized with atomic force microscopy and x-ray photoel...

  7. Temperature Effect on the Nanostructure of SDS Micelles in Water

    OpenAIRE

    Hammouda, Boualem

    2013-01-01

    Sodium dodecyl sulfate (SDS) surfactants form micelles when dissolved in water. These are formed of a hydrocarbon core and hydrophilic ionic surface. The small-angle neutron scattering (SANS) technique was used with deuterated water (D2O) in order to characterize the micelle structure. Micelles were found to be slightly compressed (oblate ellipsoids) and their sizes shrink with increasing temperature. Fits of SANS data to the Mean Spherical Approximation (MSA) model yielded a calculated micel...

  8. The Size Distribution of Bovine Casein Micelles: A Review

    OpenAIRE

    Holt, C.

    1985-01-01

    This review considers the average size and size distribution of bovine casein micelles as measured by electron microscopy, light scattering and controlled pore glass chromatography, and the origin and biological function of the size distribution. Recent work by electron microscopy has given average sizes in reasonable agreement with measurements on the same milk sample by light scattering . It is suggested that natural variations in averaqe micelle size and overestimation of micelle radii ...

  9. Core-cross-linked polymer micelles via living polymerizations

    International Nuclear Information System (INIS)

    This work reports a general synthesis to core-cross-linked polymer micelles directly from monomers by two typical living polymerizations, anionic polymerization and atom transfer radical polymerization. The micelle concentrations are hundred times higher than those by traditional synthetic method using selective solvents. The morphologies of polymer micelles can be controlled to be spheres, fibers, and graft-like aggregates by varying the experimental conditions. Micelles with the same polymer in both the core and the shell have also been synthesized by this approach.

  10. Diclofenac/biodegradable polymer micelles for ocular applications

    Science.gov (United States)

    Li, Xingyi; Zhang, Zhaoliang; Li, Jie; Sun, Shumao; Weng, Yuhua; Chen, Hao

    2012-07-01

    In this paper, methoxypoly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) micelle formulations as promising nano-carriers for poorly water soluble drugs were investigated for the delivery of diclofenac to the eye. Diclofenac loaded MPEG-PCL micelles were prepared by a simple solvent-diffusion method and characterized by dynamic light scattering (DLS), atomic force microscopy (AFM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), differential scanning calorimetery (DSC), etc. With the analysis of XRD and DSC, the diclofenac was present as an amorphous state in the formulation. The in vitro release profile indicated a sustained release manner of diclofenac from the micelles. Meanwhile, in vivo studies on eye irritation were performed with blank MPEG-PCL micelles (200 mg ml-1). The results showed that the developed MPEG-PCL micelles were non-irritants to the eyes of rabbits. In vitro penetration studies across the rabbit cornea demonstrated that the micelle formulations exhibited a 17-fold increase in penetration compared with that of diclofenac phosphate buffered saline (PBS) solution. The in vivo pharmacokinetics profile of the micelle parent drug in the aqueous humor of the rabbit was evaluated and the data showed that the diclofenac loaded MPEG-PCL micelles exhibited a 2-fold increase in AUC0-24 h than that of the diclofenac PBS solution eye drops. These results suggest a great potential of our micelle formulations as a novel ocular drug delivery system to improve the bioavailability of the drugs.

  11. Mesoscale crystallization of calcium phosphate nanostructures in protein (casein) micelles

    Science.gov (United States)

    Thachepan, Surachai; Li, Mei; Mann, Stephen

    2010-11-01

    Aqueous micelles of the multi-protein calcium phosphate complex, casein, were treated at 60 °C and pH 7 over several months. Although partial dissociation of the micelles into 12 nm sized amorphous calcium phosphate (ACP)/protein nanoparticles occurred within a period of 14 days, crystallization of the ACP nanoclusters into bundles of hydroxyapatite (HAP) nanofilaments was not observed until after 12 weeks. The HAP nanofilaments were formed specifically within the partially disrupted protein micelles suggesting a micelle-mediated pathway of mesoscale crystallization. Similar experiments using ACP-containing synthetic micelles prepared from β-casein protein alone indicated that co-aligned bundles of HAP nanofilaments were produced within the protein micelle interior after 24 hours at temperatures as low as 35 °C. The presence of Mg2+ ions in the casein micelles, as well as a possible synergistic effect associated with the multi-protein nature of the native aggregates, could account for the marked inhibition in mesoscale crystallization observed in the casein micelles compared with the single-component β-casein constructs.Aqueous micelles of the multi-protein calcium phosphate complex, casein, were treated at 60 °C and pH 7 over several months. Although partial dissociation of the micelles into 12 nm sized amorphous calcium phosphate (ACP)/protein nanoparticles occurred within a period of 14 days, crystallization of the ACP nanoclusters into bundles of hydroxyapatite (HAP) nanofilaments was not observed until after 12 weeks. The HAP nanofilaments were formed specifically within the partially disrupted protein micelles suggesting a micelle-mediated pathway of mesoscale crystallization. Similar experiments using ACP-containing synthetic micelles prepared from β-casein protein alone indicated that co-aligned bundles of HAP nanofilaments were produced within the protein micelle interior after 24 hours at temperatures as low as 35 °C. The presence of Mg2+ ions in

  12. Comparing concentration-based (AOT40) and stomatal uptake (PODY) metrics for ozone risk assessment to European forests.

    Science.gov (United States)

    Anav, Alessandro; De Marco, Alessandra; Proietti, Chiara; Alessandri, Andrea; Dell'Aquila, Alessandro; Cionni, Irene; Friedlingstein, Pierre; Khvorostyanov, Dmitry; Menut, Laurent; Paoletti, Elena; Sicard, Pierre; Sitch, Stephen; Vitale, Marcello

    2016-04-01

    Tropospheric ozone (O3 ) produces harmful effects to forests and crops, leading to a reduction of land carbon assimilation that, consequently, influences the land sink and the crop yield production. To assess the potential negative O3 impacts to vegetation, the European Union uses the Accumulated Ozone over Threshold of 40 ppb (AOT40). This index has been chosen for its simplicity and flexibility in handling different ecosystems as well as for its linear relationships with yield or biomass loss. However, AOT40 does not give any information on the physiological O3 uptake into the leaves since it does not include any environmental constraints to O3 uptake through stomata. Therefore, an index based on stomatal O3 uptake (i.e. PODY), which describes the amount of O3 entering into the leaves, would be more appropriate. Specifically, the PODY metric considers the effects of multiple climatic factors, vegetation characteristics and local and phenological inputs rather than the only atmospheric O3 concentration. For this reason, the use of PODY in the O3 risk assessment for vegetation is becoming recommended. We compare different potential O3 risk assessments based on two methodologies (i.e. AOT40 and stomatal O3 uptake) using a framework of mesoscale models that produces hourly meteorological and O3 data at high spatial resolution (12 km) over Europe for the time period 2000-2005. Results indicate a remarkable spatial and temporal inconsistency between the two indices, suggesting that a new definition of European legislative standard is needed in the near future. Besides, our risk assessment based on AOT40 shows a good consistency compared to both in-situ data and other model-based datasets. Conversely, risk assessment based on stomatal O3 uptake shows different spatial patterns compared to other model-based datasets. This strong inconsistency can be likely related to a different vegetation cover and its associated parameterizations. PMID:26492093

  13. Removal of diclofenac potassium from wastewater using clay-micelle complex.

    Science.gov (United States)

    Karaman, Rafik; Khamis, Mustafa; Quried, Mohannad; Halabieh, Rawan; Makharzeh, Iman; Manassra, Adnan; Abbadi, Jehad; Qtait, Alaa; Bufo, Sabino Aurelio; Nasser, Ahmed; Nir, Shlomo

    2012-06-01

    The presence of an ionized carboxyl group in the widely used non-steroidal anti-inflammatory (NSAID) drug diclofenac potassium results in a high mobility of diclofenac and in its low sorption under conditions of slow sand filtration or subsoil passage. No diclofenac degradation was detected in pure water or sludge during one month. Tertiary treatments of wastewater indicated that the effective removal of diclofenac was by reverse osmosis, but the removal by activated carbon was less satisfactory. This study presents an efficient method for the removal of diclofenac from water by micelle-clay composites that are positively charged, have a large surface area and include large hydrophobic domains. Adsorption of diclofenac in dispersion by charcoal and a composite micelle (otadecyltrimethylammonium [ODTMA] and clay [montmorillonite]) was investigated. Analysis by the Langmuir isotherm revealed that charcoal had a somewhat larger number of adsorption sites than the composite, but the latter had a significantly larger binding affinity for diclofenac. Filtration experiments on a solution containing 300 ppm diclofenac demonstrated poor removal by activated carbon, in contrast to very efficient removal by micelle-clay filters. In the latter case the weight of removed diclofenac exceeded half that of ODTMA in the filter. Filtration of diclofenac solutions at concentrations of 8 and 80 ppb yielded almost complete removal at flow rates of 30 and 60 mL min(-1). One kilogram of ODTMA in the micelle-clay filter has been estimated to remove more than 99% of diclofenac from a solution of 100 ppb during passage of more than 100 m3. PMID:22856300

  14. Micellar interactions in water-AOT based droplet microemulsions containing hydrophilic and amphiphilic polymers

    Science.gov (United States)

    Appel, Markus; Spehr, Tinka Luise; Wipf, Robert; Moers, Christian; Frey, Holger; Stühn, Bernd

    2013-11-01

    We investigate the influence of addition of hydrophilic and amphiphilic polymer on percolation behavior and micellar interactions in AOT-based water-in-oil droplet microemulsions. We focus on two series of samples having constant molar water to surfactant ratio W = 20 and constant droplet volume fraction Φ = 30%, respectively. From dielectric spectroscopy experiments, we extract the bending rigidity of the surfactant shell by percolation temperature measurements. Depending on droplet size, we find stabilization and destabilization of the surfactant shell upon addition of hydrophilic poly(ethylene glycol) (PEG) (Mn = 3100 g mol-1) and amphiphilic poly(styrene)-b-poly(ethylene glycol) copolymer with comparable length of the hydrophilic block. Complementary small angle X-ray scattering experiments corroborate the finding of stabilization for smaller droplets and destabilization of larger droplets. Subsequent analysis of dielectric spectra enables us to extract detailed information about micellar interactions and clustering by evaluating the dielectric high frequency shell relaxation. We interpret the observed results as a possible modification of the inter-droplet charge transfer efficiency by addition of PEG polymer, while the amphiphilic polymer shows a comparable, but dampened effect.

  15. Reverse micellar extraction of bromelain from pineapple peel--Effect of surfactant structure.

    Science.gov (United States)

    Wan, Jing; Guo, Jingjing; Miao, Zhitong; Guo, Xia

    2016-04-15

    Pineapple peel is generally disposed or used as compost. This study was focused on extracting bromelain from pineapple peel by using reverse micelles. It was found that gemini surfactant C12-8-C12·2Br (octamethylene-α,ω-bis(dimethyldodecylammonium bromide)) showed distinctive advantage over its monomeric counterpart DTAB (dodecyl trimethyl ammonium bromide); under optimized condition, the bromelain extracted with C12-8-C12·2Br reverse micelle had an activity recovery of 163% and a purification fold of 3.3, while when using DTAB reverse micelle, the activity recovery was 95% and the purification fold was 1.7. Therefore, the spacer of gemini surfactant should play a positive role in bromelain extraction and may suggest the potential of gemini surfactant in protein separation since it has been so far rarely used in relative experiments or technologies. PMID:26616974

  16. Different Types of Charged-Inverse Micelles in Nonpolar Media.

    Science.gov (United States)

    Prasad, Manoj; Strubbe, Filip; Beunis, Filip; Neyts, Kristiaan

    2016-06-14

    Over the last few years, the electrodynamics of charged inverse micelles (CIMs) in nonpolar liquids and the generation mechanism and properties of newly generated CIMs have been studied extensively for the model system of polyisobutylene succinimide in dodecane. However, the newly generated CIMs, which accumulate at the electrodes when a continuous voltage is applied, behave differently compared to the regular CIMs present in equilibrium in the absence of a field. In this work, we use transient current measurements to investigate the behavior of the newly generated CIMs when the field is reduced to zero or reversed. We demonstrate that the newly generated CIMs do not participate in the diffuse double layer near the electrode formed by the regular CIMs but form an interface layer at the electrode surface. A fraction of the newly generated negative CIMs can be released from this interface layer when the field there becomes zero. The findings of this study provide a better understanding of fundamental processes in nonpolar liquids and are relevant for applications such as electronic ink displays and liquid toner printing. PMID:27231768

  17. pH dependent polymeric micelle adsorption

    International Nuclear Information System (INIS)

    Full text: Poly(2-vinylpyridine)-poly(ethylene oxide) (P2VP-PEO) shows potential as a possible drug delivery system for anti-tumour drugs since it forms pH dependent polymeric micelles. Hence to better understand the adsorption behaviour of this polymer we have studied the interaction forces between layers of P2VP-PEO adsorbed onto silica as a function of solution pH using an Atomic Force Microscope (AFM). When P2VP-PEO is initially adsorbed above the pKa of the P2VP block, P2VP-PEO adsorbs from solution as micelles that exist as either partially collapsed- or a hemi-micelles at the silica surface. Below the pKa of P2VP, the P2VP-PEO adsorbs as unimers, forming a compact layer with little looping and tailing into solution. When initial adsorption of P2VP-PEO is in the form of unimers, any driving force to self-assembly of the now charge neutral polymer is kinetically hindered. Hence, after initial adsorption at pH 3.6, a subsequent increase in pH to 6.6 results in a slow surface restructuring towards self-assembly and equilibrium. When the pH is increased from pH 6.6 to 9.7 there is a continuation of the evolution of the system to its equilibrium position during which the adsorbed P2VP-PEO unimers continue to 'unravel' from the surface, extending away from it, towards eventual complete surface self-assembly

  18. Magainin II modified polydiacetylene micelles for cancer therapy

    Science.gov (United States)

    Yang, Danling; Zou, Rongfeng; Zhu, Yu; Liu, Ben; Yao, Defan; Jiang, Juanjuan; Wu, Junchen; Tian, He

    2014-11-01

    Polydiacetylene (PDA) micelles have been widely used to deliver anticancer drugs in the treatment of a variety of tumours and for imaging living cells. In this study, we developed an effective strategy to directly conjugate magainin II (MGN-II) to the surface of PDA micelles using a fluorescent dye. These stable and well-defined PDA micelles had high cytotoxicity in cancer cell lines, and were able to reduce the tumour size in mice. The modified PDA micelles improved the anticancer effects of MGN-II in the A549 cell line only at a concentration of 16.0 μg mL-1 (IC50). In addition, following irradiation with UV light at 254 nm, the PDA micelles gave rise to an energy transfer from the fluorescent dye to the backbone of PDA micelles to enhance the imaging of living cells. Our results demonstrate that modified PDA micelles can not only be used in the treatment of tumors in vitro and in vivo in a simple and directed way, but also offer a new platform for designing functional liposomes to act as anticancer agents.Polydiacetylene (PDA) micelles have been widely used to deliver anticancer drugs in the treatment of a variety of tumours and for imaging living cells. In this study, we developed an effective strategy to directly conjugate magainin II (MGN-II) to the surface of PDA micelles using a fluorescent dye. These stable and well-defined PDA micelles had high cytotoxicity in cancer cell lines, and were able to reduce the tumour size in mice. The modified PDA micelles improved the anticancer effects of MGN-II in the A549 cell line only at a concentration of 16.0 μg mL-1 (IC50). In addition, following irradiation with UV light at 254 nm, the PDA micelles gave rise to an energy transfer from the fluorescent dye to the backbone of PDA micelles to enhance the imaging of living cells. Our results demonstrate that modified PDA micelles can not only be used in the treatment of tumors in vitro and in vivo in a simple and directed way, but also offer a new platform for

  19. Influence of race and crossbreeding on casein micelles size.

    Science.gov (United States)

    Freitas, Denise R; Fonseca, Leorges M; Souza, Fernando N; Ladeira, Cristiane V G; Diniz, Soraia A; Haddad, João Paulo A; Ferreira, Diêgo S; Santoro, Marcelo M; Cerqueira, Mônica M O P

    2015-05-01

    Casein (CN) micelles are colloidal aggregates of protein dispersed in milk, the importance of which in the dairy industry is related to functionality and yield in dairy products. The objective of this work was to investigate the correlation of milk CN micelles diameter from Holstein and Zebu crossbreds with milk composition (protein, fat, lactose, total and nonfat solids and milk urea nitrogen), somatic cell count (SCC), age, lactation stage and production. Average casein micelles diameters of milk samples obtained from 200 cows were measured using photon correlation spectroscopy and multiple regression analysis was used to find relationship between variables. CN micelle diameter, SCC and nonfat solids were different between animals with different Holstein crossbreed ratios, which suggests influence of genetic factors, mammary gland health and milk composition. Overall, results indicate the potential use of CN micelle diameter as a tool to select animals to produce milk more suitable to cheese production. PMID:25488503

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

    Science.gov (United States)

    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.

  1. Reverse Engineering

    International Nuclear Information System (INIS)

    This book gives descriptions of reverse engineering with principle and structure of it, including what reverse engineering is, prospect and concerned laws, basic knowledge for reverse engineering like manual and back to user mode, using tool such as IDA installation, dependency walker and dump bin, network monitoring and universal extractor. It indicates analysis of malignant code, giving explanations of file virus, spy ware, an infection way of malignant code, anti debugging like Find window.

  2. Description and validation of an AOT product over land at the 0.6 μm channel of the SEVIRI sensor onboard MSG

    Science.gov (United States)

    Bernard, E.; Moulin, C.; Ramon, D.; Jolivet, D.; Riedi, J.; Nicolas, J.-M.

    2011-11-01

    The Spinning Enhanced Visible and InfraRed Imager (SEVIRI) aboard Meteosat Second Generation (MSG) launched in 2003 by EUMETSAT is dedicated to the Nowcasting applications and Numerical Weather Prediction and to the provision of observations for climate monitoring and research. We use the data in visible and near infrared (NIR) channels to derive the aerosol optical thickness (AOT) over land. The algorithm is based on the assumption that the top of the atmosphere (TOA) reflectance increases with the aerosol load. This is a reasonable assumption except in case of absorbing aerosols above bright surfaces. We assume that the minimum in a 14-days time series of the TOA reflectance is, once corrected from gaseous scattering and absorption, representative of the surface reflectance. The AOT and the aerosol model (a set of 5 models is used), are retrieved by matching the simulated TOA reflectance with the TOA reflectances measured by SEVIRI in its visible and NIR spectral bands. The high temporal resolution of the data acquisition by SEVIRI allows to retrieve the AOT every 15 min with a spatial resolution of 3 km at sub-satellite point, over the entire SEVIRI disk covering Europe, Africa and part of South America. The resulting AOT, a level 2 product at the native temporal and spatial SEVIRI resolutions, is presented and evaluated in this paper. The AOT has been validated using ground based measurements from AErosol RObotic NETwork (AERONET), a sun-photometer network, focusing over Europe for 3 months in 2006. The SEVIRI estimates correlate well with the AERONET measurements, r = 0.64, with a slight overestimate, bias = -0.017. The sources of errors are mainly the cloud contamination and the bad estimation of the surface reflectance. The temporal evolutions exhibited by both datasets show very good agreement which allows to conclude that the AOT Level 2 product from SEVIRI can be used to quantify the aerosol content and to monitor its daily evolution with a high temporal

  3. Therapeutic surfactant-stripped frozen micelles

    Science.gov (United States)

    Zhang, Yumiao; Song, Wentao; Geng, Jumin; Chitgupi, Upendra; Unsal, Hande; Federizon, Jasmin; Rzayev, Javid; Sukumaran, Dinesh K.; Alexandridis, Paschalis; Lovell, Jonathan F.

    2016-05-01

    Injectable hydrophobic drugs are typically dissolved in surfactants and non-aqueous solvents which can induce negative side-effects. Alternatives like `top-down' fine milling of excipient-free injectable drug suspensions are not yet clinically viable and `bottom-up' self-assembled delivery systems usually substitute one solubilizing excipient for another, bringing new issues to consider. Here, we show that Pluronic (Poloxamer) block copolymers are amenable to low-temperature processing to strip away all free and loosely bound surfactant, leaving behind concentrated, kinetically frozen drug micelles containing minimal solubilizing excipient. This approach was validated for phylloquinone, cyclosporine, testosterone undecanoate, cabazitaxel and seven other bioactive molecules, achieving sizes between 45 and 160 nm and drug to solubilizer molar ratios 2-3 orders of magnitude higher than current formulations. Hypertonic saline or co-loaded cargo was found to prevent aggregation in some cases. Use of surfactant-stripped micelles avoided potential risks associated with other injectable formulations. Mechanistic insights are elucidated and therapeutic dose responses are demonstrated.

  4. The effect of photoisomerization on the enzymatic hydrolysis of polymeric micelles bearing photo-responsive azobenzene groups at their cores.

    Science.gov (United States)

    Harnoy, Assaf J; Slor, Gadi; Tirosh, Einat; Amir, Roey J

    2016-06-28

    The design of stable polymeric micelles that can respond to specific stimuli is crucial for the development of smart micellar nanocarriers that can release their active cargo selectively at the target site, thus diminishing the therapeutic limitations due to non-selective damage to healthy tissues. Here we report the design and synthesis of photo- and enzyme-responsive amphiphilic PEG-dendron hybrids bearing one, two or four enzymatically cleavable azobenzene end-groups. These dual-responsive hybrids can respond to light through the reversible isomerization of the azobenzene end-groups from the non-polar trans isomer to the highly polar cis isomer and vice versa, upon UV and visible irradiation, respectively. The high structural precision of these hybrids, which emerges from the dendritic architecture, enabled a detailed study of the photoisomerization of the azobenzene end-groups with high molecular resolution. Remarkably, although the transition from trans-to-cis led to a significant increase in the polarity of the micellar cores, the micelles remained stable. Our kinetic studies show that although the trans isomer is a better substrate for the activating enzyme, the UV induced formation of the cis azobenzene end-groups led to significant acceleration of the enzymatic hydrolysis of the end-groups. These results provide strong indication that the enzyme cannot reach the core of the micelles and instead the end-groups have to leave the hydrophobic core in order to be exposed on the micelle's surface or even leave the micelle in order to allow their cleavage by the activating enzymes. PMID:27093537

  5. In-situ synthesis of nanoparticles via supersolubilizing micelle self-assembly

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In-situ synthesis of nano-particles using the self-assembly of molten salt and super soluble micellae was proposed based on a phenomenon of super solubilization of molten salt in reverse micellae and its self-assembly when the concentration reached up to 95%(w/w).The mechanism of the self-assembly indicates that the self-assembly of molten salt occurs in a reverse micelle where a homogenous phase is established between 5%(w/w)of a surfactant with a VB value of less than 1 and a hydrocarbon spe- cies.This synthesis has some unique features,such as being free of water,highly effective deposition and narrow distribution of particle size.

  6. In-situ synthesis of nanoparticles via supersolubilizing micelle self-assembly

    Institute of Scientific and Technical Information of China (English)

    WANG DingCong

    2007-01-01

    In-situ synthesis of nano-particles using the self-assembly of molten salt and super soluble micellae was proposed based on a phenomenon of super solubilization of molten salt in reverse micellae and its self-assembly when the concentration reached up to 95% (w/w). The mechanism of the self-assembly indicates that the self-assembly of molten salt occurs in a reverse micelle where a homogenous phase is established between 5% (w/w) of a surfactant with a VB value of less than 1 and a hydrocarbon species. This synthesis has some unique features, such as being free of water, highly effective deposition and narrow distribution of particle size.

  7. Redox-Responsive Micelles with Cores Crosslinked via Click Chemistry.

    Science.gov (United States)

    Zhang, Xiaojin; Dong, Hui; Fu, Shuangli; Zhong, Zhenlin; Zhuo, Renxi

    2016-06-01

    Redox-responsive micelles with cores crosslinked via click chemistry are developed to improve the stability of polymer micelles. Amphiphilic block copolymer mPEG-b-P(DTC-ADTC) with pendant azido groups on the hydrophobic chains is synthesized by the ring-opening polymerization of 2,2-bis(azidomethyl)trimethylene carbonate (ADTC) and 2,2-dimethyltrimethylene carbonate (DTC) with monomethoxy poly(ethylene glycol) (mPEG) as an initiator. mPEG-b-P(DTC-ADTC) self-assemble to form the micelles in aqueous solution and the cores of the micelles are crosslinked via click chemistry to afford redox-responsive core-crosslinked micelles. Core-crosslinking enhances the stability of the micelles in aqueous solution and improve the drug-loading property. The redox-responsive core-crosslinked micelles can be reduced by the addition of reducing agents such as dithiothreitol (DTT), and thus release the loaded drug quickly in the presence of DTT. PMID:27150437

  8. Stereocomplex micelle from nonlinear enantiomeric copolymers efficiently transports antineoplastic drug

    Science.gov (United States)

    Wang, Jixue; Shen, Kexin; Xu, Weiguo; Ding, Jianxun; Wang, Xiaoqing; Liu, Tongjun; Wang, Chunxi; Chen, Xuesi

    2015-05-01

    Nanoscale polymeric micelles have attracted more and more attention as a promising nanocarrier for controlled delivery of antineoplastic drugs. Herein, the doxorubicin (DOX)-loaded poly(D-lactide)-based micelle (PDM/DOX), poly(L-lactide)-based micelle (PLM/DOX), and stereocomplex micelle (SCM/DOX) from the equimolar mixture of the enantiomeric four-armed poly(ethylene glycol)-polylactide (PEG-PLA) copolymers were successfully fabricated. In phosphate-buffered saline (PBS) at pH 7.4, SCM/DOX exhibited the smallest hydrodynamic diameter ( D h) of 90 ± 4.2 nm and the slowest DOX release compared with PDM/DOX and PLM/DOX. Moreover, PDM/DOX, PLM/DOX, and SCM/DOX exhibited almost stable D hs of around 115, 105, and 90 nm at above normal physiological condition, respectively, which endowed them with great potential in controlled drug delivery. The intracellular DOX fluorescence intensity after the incubation with the laden micelles was different degrees weaker than that incubated with free DOX · HCl within 12 h, probably due to the slow DOX release from micelles. As the incubation time reached to 24 h, all the cells incubated with the laden micelles, especially SCM/DOX, demonstrated a stronger intracellular DOX fluorescence intensity than free DOX · HCl-cultured ones. More importantly, all the DOX-loaded micelles, especially SCM/DOX, exhibited potent antineoplastic efficacy in vitro, excellent serum albumin-tolerance stability, and satisfactory hemocompatibility. These encouraging data indicated that the loading micelles from nonlinear enantiomeric copolymers, especially SCM/DOX, might be promising in clinical systemic chemotherapy through intravenous injection.

  9. Relative free energy of binding between antimicrobial peptides and SDS or DPC micelles

    OpenAIRE

    Sayyed-Ahmad, Abdallah; Khandelia, Himanshu; Kaznessis, Yiannis N.

    2009-01-01

    We present relative binding free energy calculations for six antimicrobial peptide–micelle systems, three peptides interacting with two types of micelles. The peptides are the scorpion derived antimicrobial peptide (AMP), IsCT and two of its analogues. The micelles are dodecylphosphatidylcholine (DPC) and sodium dodecylsulphate (SDS) micelles. The interfacial electrostatic properties of DPC and SDS micelles are assumed to be similar to those of zwitterionic mammalian and anionic bacterial mem...

  10. Self-assembly of micelles into designed networks

    Directory of Open Access Journals (Sweden)

    Pyatenko Alexander

    2007-01-01

    Full Text Available AbstractThe EO20PO70EO20(molecular weight 5800 amphiphile as a template is to form dispersed micelle structures. Silver nanoparticles, as inorganic precursors synthesized by a laser ablation method in pure water, are able to produce the highly ordered vesicles detected by TEM micrography. The thickness of the outer layer of a micelle, formed by the silver nanoparticles interacting preferentially with the more hydrophilic EO20block, was around 3.5 nm. The vesicular structure ensembled from micelles is due to proceeding to the mixture of cubic and hexagonal phases.

  11. Photophysical study of a charge transfer oxazole dye in micelles: Role of surfactant headgroups

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, Jyotirmay [Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126 (India); Sarkar, Yeasmin; Parui, Partha Pratim [Department of Chemistry, Jadavpur University, Kolkata 700032 (India); Chakraborty, Sandipan [Department of Microbiology, University of Calcutta, Kolkata 700019 (India); Biswas, Suman [Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126 (India); Das, Ranjan, E-mail: ranjan.das68@gmail.com [Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126 (India)

    2015-07-15

    Photophysics of 5-(4′′-dimethylaminophenyl)-2-(4′-sulfophenyl)oxazole, sodium salt (DMO) which undergoes intramolecular charge transfer in the excited state was studied in micelles. In the cationic and the nonionic micelles, significantly higher fluorescence quantum yield is observed in comparison to the anionic micelles, due to much lower accessibility of DMO to the water molecules in the former micelles than the latter. Time-resolved fluorescence decays were characterized by a fast (τ{sub 1}) and a slow (τ{sub 2}) component of decay in all the micelles. The fast decay component (τ{sub 1}) increases significantly in going from the anionic micelles to the cationic micelles, because of the poorly hydrated headgroup region of the latter micelles compared to the former. Furthermore, much higher value of the slow component of decay (τ{sub 2}) is observed for the cationic and the neutral micelles than the anionic micelles. This is attributed to the increased penetration of water molecules into the micellar core of the anionic micelles compared to the cationic and the neutral micelles. - Highlights: • Photophysics of the fluorophore are remarkably different in the cationic and the anionic micelles. • Differential hydration of the surfactant headgroups gives rise to significantly different fluorescence quantum yield and lifetime in oppositely charged micelles. • Electrostatic interactions fine tune location of the fluorophore in the micelle–water interface of ionic micelles.

  12. Iron oxide nanoparticle-micelles (ION-micelles for sensitive (molecular magnetic particle imaging and magnetic resonance imaging.

    Directory of Open Access Journals (Sweden)

    Lucas W E Starmans

    Full Text Available BACKGROUND: Iron oxide nanoparticles (IONs are a promising nanoplatform for contrast-enhanced MRI. Recently, magnetic particle imaging (MPI was introduced as a new imaging modality, which is able to directly visualize magnetic particles and could serve as a more sensitive and quantitative alternative to MRI. However, MPI requires magnetic particles with specific magnetic properties for optimal use. Current commercially available iron oxide formulations perform suboptimal in MPI, which is triggering research into optimized synthesis strategies. Most synthesis procedures aim at size control of iron oxide nanoparticles rather than control over the magnetic properties. In this study, we report on the synthesis, characterization and application of a novel ION platform for sensitive MPI and MRI. METHODS AND RESULTS: IONs were synthesized using a thermal-decomposition method and subsequently phase-transferred by encapsulation into lipidic micelles (ION-Micelles. Next, the material and magnetic properties of the ION-Micelles were analyzed. Most notably, vibrating sample magnetometry measurements showed that the effective magnetic core size of the IONs is 16 nm. In addition, magnetic particle spectrometry (MPS measurements were performed. MPS is essentially zero-dimensional MPI and therefore allows to probe the potential of iron oxide formulations for MPI. ION-Micelles induced up to 200 times higher signal in MPS measurements than commercially available iron oxide formulations (Endorem, Resovist and Sinerem and thus likely allow for significantly more sensitive MPI. In addition, the potential of the ION-Micelle platform for molecular MPI and MRI was showcased by MPS and MRI measurements of fibrin-binding peptide functionalized ION-Micelles (FibPep-ION-Micelles bound to blood clots. CONCLUSIONS: The presented data underlines the potential of the ION-Micelle nanoplatform for sensitive (molecular MPI and warrants further investigation of the FibPep-ION-Micelle

  13. Vasectomy Reversal

    Medline Plus

    Full Text Available ... is a realistic option for many patients. Today we are going to go to the operating room and show you microsurgical vasectomy reversal. We start the procedure by localizing the site of ...

  14. Vasectomy Reversal

    Medline Plus

    Full Text Available ... keep the vas well vascularized because ischemia will cause fibrosis and scarring and prevent the vasectomy reversal ... to make sure that we don't inadvertently cause any vascular to the vas or even to ...

  15. Vasectomy Reversal

    Medline Plus

    Full Text Available ... improving health. Hello, my name is Harris Nagler. I'm the Chairman of the Sol and Margaret ... Israel Medical Center in New York City. Today I'm going to perform a vasectomy reversal using ...

  16. Vasectomy Reversal

    Medline Plus

    Full Text Available ... Today we are going to go to the operating room and show you microsurgical vasectomy reversal. We ... vas and that will be examined under the operating- under the microscope to see if there’s sperm ...

  17. Reversible Sterilization

    Science.gov (United States)

    Largey, Gale

    1977-01-01

    Notes that difficult questions arise concerning the use of sterilization for alleged eugenic and euthenic purposes. Thus, how reversible sterilization will be used with relation to the poor, mentally ill, mentally retarded, criminals, and minors, is questioned. (Author/AM)

  18. Vasectomy Reversal

    Medline Plus

    Full Text Available Vasectomy Reversal Beth Israel Medical Center, New York, NY February 19, 2009 Welcome to this "OR Live" Webcast presentation premiering from Beth Israel Medical Center in New York City. ...

  19. Vasectomy Reversal

    Medline Plus

    Full Text Available Vasectomy Reversal Beth Israel Medical Center, New York, NY February 19, 2009 Welcome to this "OR Live" Webcast presentation premiering from Beth Israel Medical Center in New York City. During the ...

  20. Structure and reactivity in amphiphile-water micelles

    International Nuclear Information System (INIS)

    Following a review of the general properties of micelles, this report contains two parts: - A structural study of octylphosphate micelles. Important structural changes have been evidenced by mean of small angle neutron scattering as the electrical charge of the interface is varied. The NMR relaxation study of the conformation of the hydrocarbon chains has shown that the micellar core is disordered in contrast with the interface which is rather structured. The diffusion motions in the interface and the segmental motions of the chains are fast. - Studies on the reactivity in micelles have been carried out. A large micellar effect on the complexation of transition ions by amphiphilic ligands is evidenced. The problem of solute localization in micelles is developed with few examples. (author)

  1. Interactions of casein micelles with calcium phosphate particles.

    Science.gov (United States)

    Tercinier, Lucile; Ye, Aiqian; Anema, Skelte G; Singh, Anne; Singh, Harjinder

    2014-06-25

    Insoluble calcium phosphate particles, such as hydroxyapatite (HA), are often used in calcium-fortified milks as they are considered to be chemically unreactive. However, this study showed that there was an interaction between the casein micelles in milk and HA particles. The caseins in milk were shown to bind to the HA particles, with the relative proportions of bound β-casein, αS-casein, and κ-casein different from the proportions of the individual caseins present in milk. Transmission electron microscopy showed no evidence of intact casein micelles on the surface of the HA particles, which suggested that the casein micelles dissociated either before or during binding. The HA particles behaved as ion chelators, with the ability to bind the ions contained in the milk serum phase. Consequently, the depletion of the serum minerals disrupted the milk mineral equilibrium, resulting in dissociation of the casein micelles in milk. PMID:24896851

  2. Influence of succinylation on physicochemical property of yak casein micelles.

    Science.gov (United States)

    Yang, Min; Yang, Jitao; Zhang, Yuan; Zhang, Weibing

    2016-01-01

    Succinylation is a chemical-modification method that affects the physicochemical characteristics and functional properties of proteins. This study assessed the influence of succinylation on the physicochemical properties of yak casein micelles. The results revealed that surface hydrophobicity indices decreased with succinylation. Additionally, denaturation temperature and denaturation enthalpy decreased with increasing succinylation level, except at 82%. The buffering properties of yak casein micelles were affected by succinylation. It was found that chemical modification contributed to a slight shift of the buffering peak towards a lower pH value and a markedly increase of the maximum buffering values of yak casein micelles at pH 4.5-6.0 and pH casein micellar hydration and whiteness values. The findings obtained from this study will provide the basic information on the physicochemical properties of native and succinylated yak casein micelles. PMID:26213046

  3. Sulfometuron incorporation in cationic micelles adsorbed on montmorillonite

    OpenAIRE

    Mishael, Y. G.; Undabeytia López, Tomás; Rytwo, Giora; Papahadjopoulos Sternberg, B.; Rubin, Baruch; Nir, Shlomo

    2002-01-01

    The aim of this study was to understand the interactions between alkylammonium cations present as monomers and micelles and a clay mineral, montmorillonite, to develop slow release formulations of anionic herbicides, such as sulfometuron (SFM) whose leaching in soils is an environmental and economic problem. In the proposed formulation the herbicide is incorporated in positively charged micelles of quaternary amine cations, which in turn adsorb on the negatively charged clay. The adsorption o...

  4. A neutron scattering study of triblock copolymer micelles

    Energy Technology Data Exchange (ETDEWEB)

    Gerstenberg, M.C.

    1997-11-01

    The thesis describes the neutron scattering experiments performed on poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) triblock copolymer micelles in aqueous solution. The studies concern the non-ionic triblock copolymer P85 which consists of two outer segments of 25 monomers of ethylene oxide attached to a central part of 40 monomers of propylene oxide. The amphiphilic character of P85 leads to formation of various structures in aqueous solution such as spherical micelles, rod-like structures, and a BCC liquid-crystal mesophase of spherical micelles. The present investigations are centered around the micellar structures. In the first part of this thesis a model for the micelle is developed for which an analytical scattering form factor can be calculated. The micelle is modeled as a solid sphere with tethered Gaussian chains. Good agreement was found between small-angle neutron scattering experiments and the form factor of the spherical P85 micelles. Above 60 deg. C some discrepancies were found between the model and the data which is possibly due to an elongation of the micelles. The second part focuses on the surface-induced ordering of the various micellar aggregates in the P85 concentration-temperature phase diagram. In the spherical micellar phase, neutron reflection measurements indicated a micellar ordering at the hydrophilic surface of quartz. Extensive modeling was performed based on a hard sphere description of the micellar interaction. By convolution of the distribution of hard spheres at a hard wall, obtained from Monte Carlo simulations, and the projected scattering length density of the micelle, a numerical expression was obtained which made it possible to fit the data. The hard-sphere-hard-wall model gave an excellent agreement in the bulk micellar phase. However, for higher concentrations (25 wt % P85) close to the transition from the micellar liquid into a micellar cubic phase, a discrepancy was found between the model and the

  5. New self-assembled nanocrystal micelles for biolabels and biosensors.

    Energy Technology Data Exchange (ETDEWEB)

    Tallant, David Robert; Wilson, Michael C. (University of New Mexico, Albuquerque, NM); Leve, Erik W. (University of New Mexico, Albuquerque, NM); Fan, Hongyou; Brinker, C. Jeffrey; Gabaldon, John (University of New Mexico, Albuquerque, NM); Scullin, Chessa (University of New Mexico, Albuquerque, NM)

    2005-12-01

    The ability of semiconductor nanocrystals (NCs) to display multiple (size-specific) colors simultaneously during a single, long term excitation holds great promise for their use in fluorescent bio-imaging. The main challenges of using nanocrystals as biolabels are achieving biocompatibility, low non-specific adsorption, and no aggregation. In addition, functional groups that can be used to further couple and conjugate with biospecies (proteins, DNAs, antibodies, etc.) are required. In this project, we invented a new route to the synthesis of water-soluble and biocompatible NCs. Our approach is to encapsulate as-synthesized, monosized, hydrophobic NCs within the hydrophobic cores of micelles composed of a mixture of surfactants and phospholipids containing head groups functionalized with polyethylene glycol (-PEG), -COOH, and NH{sub 2} groups. PEG provided biocompatibility and the other groups were used for further biofunctionalization. The resulting water-soluble metal and semiconductor NC-micelles preserve the optical properties of the original hydrophobic NCs. Semiconductor NCs emit the same color; they exhibit equal photoluminescence (PL) intensity under long-time laser irradiation (one week) ; and they exhibit the same PL lifetime (30-ns). The results from transmission electron microscopy and confocal fluorescent imaging indicate that water-soluble semiconductor NC-micelles are biocompatible and exhibit no aggregation in cells. We have extended the surfactant/lipid encapsulation techniques to synthesize water-soluble magnetic NC-micelles. Transmission electron microscopy results suggest that water-soluble magnetic NC-micelles exhibit no aggregation. The resulting NC-micelles preserve the magnetic properties of the original hydrophobic magnetic NCs. Viability studies conducted using yeast cells suggest that the magnetic nanocrystal-micelles are biocompatible. We have demonstrated, for the first time, that using external oscillating magnetic fields to manipulate

  6. Structure of strongly interacting polyelectrolyte diblock copolymer micelles

    OpenAIRE

    Korobko, A.V.; Jesse, W.; Lapp, A.; Egelhaaf, S. U.; van der Maarel, J. R. C.

    2004-01-01

    The structure of spherical micelles of the diblock poly(styrene-block-acrylic acid) [PS-b-PA] copolymer in water was investigated up to concentrations where the polyelectrolyte coronal layers have to shrink and/or interpenetrate in order to accommodate the micelles in the increasingly crowded volume. We obtained the partial structure factors pertaining to the core and corona density correlations with small angle neutron scattering (SANS) and contrast matching in the water. The counterion stru...

  7. The Size Distribution of Casein Micelles in Camel Milk

    OpenAIRE

    Farah, Z.; Ruegg, M. W.

    1989-01-01

    The size distribution of casein micelles in camel milk has been determined by electron microscopy. Individual and pooled samples were cryo-fixed by rapid freezing and freeze-fractured. Electron micrographs of the freeze-fracture replica revealed a relatively broad size distribution, with an average micelle dimeter around 280 nm in the volume distribution curve. The distribution was significantly broader than that of the particles of cow's or human milk and showed a greater number of large ...

  8. A neutron scattering study of triblock copolymer micelles

    International Nuclear Information System (INIS)

    The thesis describes the neutron scattering experiments performed on poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) triblock copolymer micelles in aqueous solution. The studies concern the non-ionic triblock copolymer P85 which consists of two outer segments of 25 monomers of ethylene oxide attached to a central part of 40 monomers of propylene oxide. The amphiphilic character of P85 leads to formation of various structures in aqueous solution such as spherical micelles, rod-like structures, and a BCC liquid-crystal mesophase of spherical micelles. The present investigations are centered around the micellar structures. In the first part of this thesis a model for the micelle is developed for which an analytical scattering form factor can be calculated. The micelle is modeled as a solid sphere with tethered Gaussian chains. Good agreement was found between small-angle neutron scattering experiments and the form factor of the spherical P85 micelles. Above 60 deg. C some discrepancies were found between the model and the data which is possibly due to an elongation of the micelles. The second part focuses on the surface-induced ordering of the various micellar aggregates in the P85 concentration-temperature phase diagram. In the spherical micellar phase, neutron reflection measurements indicated a micellar ordering at the hydrophilic surface of quartz. Extensive modeling was performed based on a hard sphere description of the micellar interaction. By convolution of the distribution of hard spheres at a hard wall, obtained from Monte Carlo simulations, and the projected scattering length density of the micelle, a numerical expression was obtained which made it possible to fit the data. The hard-sphere-hard-wall model gave an excellent agreement in the bulk micellar phase. However, for higher concentrations (25 wt % P85) close to the transition from the micellar liquid into a micellar cubic phase, a discrepancy was found between the model and the

  9. Predicting proton titration in cationic micelle and bilayer environments

    OpenAIRE

    Brian H. Morrow; Eike, David M.; Murch, Bruce P.; Koenig, Peter H.; Shen, Jana K.

    2014-01-01

    Knowledge of the protonation behavior of pH-sensitive molecules in micelles and bilayers has significant implications in consumer product development and biomedical applications. However, the calculation of pKa’s in such environments proves challenging using traditional structure-based calculations. Here we apply all-atom constant pH molecular dynamics with explicit ions and titratable water to calculate the pKa of a fatty acid molecule in a micelle of dodecyl trimethylammonium chloride and l...

  10. Rheology and phase behavior of dense casein micelle dispersions

    Science.gov (United States)

    Bouchoux, A.; Debbou, B.; Gésan-Guiziou, G.; Famelart, M.-H.; Doublier, J.-L.; Cabane, B.

    2009-10-01

    Casein micelle dispersions have been concentrated through osmotic stress and examined through rheological experiments. In conditions where the casein micelles are separated from each other, i.e., below random-close packing, the dispersions have exactly the flow and dynamic properties of the polydisperse hard-sphere fluid, demonstrating that the micelles interact only through excluded volume effects in this regime. These interactions cause the viscosity and the elastic modulus to increase by three orders of magnitude approaching the concentration of random-close packing estimated at Cmax≈178 g/l. Above Cmax, the dispersions progressively turn into "gels" (i.e., soft solids) as C increases, with elastic moduli G' that are nearly frequency independent. In this second regime, the micelles deform and/or deswell as C increases, and the resistance to deformation results from the formation of bonds between micelles combined with the intrinsic mechanical resistance of the micelles. The variation in G' with C is then very similar to that observed with concentrated emulsions where the resistance to deformation originates from a set of membranes that separate the droplets. As in the case of emulsions, the G' values at high frequency are also nearly identical to the osmotic pressures required to compress the casein dispersions. The rheology of sodium caseinate dispersions in which the caseins are not structured into micelles is also reported. Such dispersions have the behavior of associative polymer solutions at all the concentrations investigated, further confirming the importance of structure in determining the rheological properties of casein micelle systems.

  11. Structural changes of casein micelles in a calcium gradient film

    OpenAIRE

    Gebhardt, R.; Burghammer, M.; Riekel, C.; Roth, S. V.; Müller-Buschbaum, P.

    2008-01-01

    Calcium gradients are prepared by sequentially filling a micropipette with casein solutions of varying calcium concentration and spreading them on glass slides. The casein film is formed by a solution casting process, which results in a macroscopically rough surface. Microbeam grazing incidence small-angle X-ray scattering (microGISAXS) is used to investigate the lateral size distribution of three main components in casein films: casein micelles, casein mini-micelles, and micellar calcium pho...

  12. Casein Micelles: Size Distribution in Milks from Individual Cows

    OpenAIRE

    Kruif, C.G. de; Huppertz, T.

    2012-01-01

    The size distribution and protein composition of casein micelles in the milk of Holstein-Friesian cows was determined as a function of stage and number of lactations. Protein composition did not vary significantly between the milks of different cows or as a function of lactation stage. Differences in the size and polydispersity of the casein micelles were observed between the milks of different cows, but not as a function of stage of milking or stage of lactation and not even over successive ...

  13. Atomic Model and Micelle Dynamics of QS-21 Saponin

    OpenAIRE

    Conrado Pedebos; Laércio Pol-Fachin; Ramon Pons; Cilâine V. Teixeira; Hugo Verli

    2014-01-01

    QS-21 is a saponin extracted from Quillaja saponaria, widely investigated as a vaccine immunoadjuvant. However, QS-21 use is mainly limited by its chemical instability, significant variety in molecular composition and low tolerance dose in mammals. Also, this compound tends to form micelles in a concentration-dependent manner. Here, we aimed to characterize its conformation and the process of micelle formation, both experimentally and computationally. Therefore, molecular dynamics (MD) simula...

  14. Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst.

    Science.gov (United States)

    Yeow, Jonathan; Xu, Jiangtao; Boyer, Cyrille

    2016-01-01

    Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (λ = 460 nm, 0.7 mW/cm(2)), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology. PMID:27340940

  15. Sulfometuron incorporation in cationic micelles adsorbed on montmorillonite.

    Science.gov (United States)

    Mishael, Yael Golda; Undabeytia, Tomas; Rytwo, Giora; Papahadjopoulos-Sternberg, Brigitte; Rubin, Baruch; Nir, Shlomo

    2002-05-01

    The aim of this study was to understand the interactions between alkylammonium cations present as monomers and micelles and a clay mineral, montmorillonite, to develop slow release formulations of anionic herbicides, such as sulfometuron (SFM) whose leaching in soils is an environmental and economic problem. In the proposed formulation the herbicide is incorporated in positively charged micelles of quaternary amine cations, which in turn adsorb on the negatively charged clay. The adsorption of hexadecyltrimethylammonium (HDTMA) and octadecyltrimethylammonium (ODTMA) on montmorillonite was studied above and below their critical micelle concentrations (CMC). At concentrations above the CMC, the loading exceeded the clay's cation exchange capacity (CEC) and indicated higher affinity of the cation with the longer alkyl chain. An adsorption model could adequately simulate adsorption at concentrations below the CMC, and yield fair predictions for the effect of ionic strength. The model indicated that above the CMC adsorbed micelles contributed significantly to the amount of ODTMA adsorbed. Evidence for adsorption of ODTMA micelles on montmorillonite was provided by X-ray diffraction, freeze-fracture electron microscopy, and dialysis bag measurements. SFM was not adsorbed directly on the clay mineral, and adsorbed at low levels, when the organic cation was adsorbed as monomers. In contrast, a large fraction of SFM adsorbed on the clay mineral when incorporated in micelles that adsorbed on the clay. PMID:11982411

  16. Atomic Model and Micelle Dynamics of QS-21 Saponin

    Directory of Open Access Journals (Sweden)

    Conrado Pedebos

    2014-03-01

    Full Text Available QS-21 is a saponin extracted from Quillaja saponaria, widely investigated as a vaccine immunoadjuvant. However, QS-21 use is mainly limited by its chemical instability, significant variety in molecular composition and low tolerance dose in mammals. Also, this compound tends to form micelles in a concentration-dependent manner. Here, we aimed to characterize its conformation and the process of micelle formation, both experimentally and computationally. Therefore, molecular dynamics (MD simulations were performed in systems containing different numbers of QS-21 molecules in aqueous solution, in order to evaluate the spontaneous micelle formation. The applied methodology allowed the generation of micelles whose sizes were shown to be in high agreement with small-angle X-ray scattering (SAXS. Furthermore, the ester linkage between fucose and acyl chain was less solvated in the micellar form, suggesting a reduction in hydrolysis. This is the first atomistic interpretation of previous experimental data, the first micellar characterization of saponin micelles by SAXS and first tridimensional model of a micelle constituted of saponins, contributing to the understanding of the molecular basis of these compounds.

  17. Synthesis of CaCO3 nanoparticles by carbonation of lime solutions in reverse micellar systems

    NARCIS (Netherlands)

    Heeres, H.J.; Jain, R.; Mehra, A.; Dagaonkar, M.V.

    2004-01-01

    Application of reverse micelles for the synthesis of nano-sized calcium carbonate particles in different solvents (cyclohexane, decane and heptane) has been investigated. The effect of the mole ratio of water-to-surfactant (R) and type of solvent has been studied on the size and nature of the carbon

  18. Synergistically Improved Anti-tumor Efficacy by Co-delivery Doxorubicin and Curcumin Polymeric Micelles.

    Science.gov (United States)

    Wang, Jinling; Ma, Wenzhuan; Tu, Pengfei

    2015-09-01

    P-gp mediated drug efflux has been recognized as a major obstacle limiting the success of cancer chemotherapy. To overcome this issue, doxorubicin (DOX) and curcumin (Cur; P-gp inhibitor and apoptosis inhibitor) co-encapsulated pegylated polymeric micelles ((DOX+Cur)-PMs) were designed, prepared and characterized to simultaneously deliver chemotherapeutic drug and multidrug resistance (MDR) modulator to tumor sites. The (DOX+Cur)-PMs were spherical nano-size particle, with a loading content of 6.83%, and high colloidal stability. Co-delivery micelles exhibited excellent cytotoxicity by reversing MDR, promoting cellular uptake and enhancing cellular apoptosis in MCF7/Adr cells. The tumor growth inhibitory effect of (DOX+Cur)-PMs in 4T1-bearing mice was more effective compared with the combination solution of DOX and Cur and even DOX-PMs. In conclusion, simultaneous delivery of DOX and Cur by (DOX+Cur)-PMs has been demonstrated to be a promising approach for overcoming MDR and improving antitumor efficacy. PMID:25981672

  19. Morphology of polysorbate 80 (Tween 80) micelles in aqueous dimethyl sulfoxide solutions

    OpenAIRE

    Aizawa, Hideki

    2010-01-01

    The structures of micelles of the surfactant polysorbate 80 (Tween 80) in 0–50% aqueous dimethyl sulfoxide (DMSO) solutions (pH 7.2, ionic strength 2.44 mM) were investigated by means of small-angle X-ray scattering. At DMSO concentrations of 0–20%, core–shell cylinder micelles formed, and at 30–50% DMSO, core–shell discus micelles formed, that is, changing the hydrophobicity of the DMSO solvent mixture changed the micelles from core–shell cylinder micelles to core–shell discus micelles....

  20. Surface induced ordering of micelles at the solid-liquid interface

    DEFF Research Database (Denmark)

    Gerstenberg, M.C.; Pedersen, J.S.; Smith, G.S.

    1998-01-01

    The surface induced ordering of triblock copolymer micelles in aqueous solution was measured with neutron reflectivity far above the critical micelle concentration. The scattering length density profiles showed a clear indication of ordered layers of micelles perpendicular to a quartz surface. The...... structure and interactions of the micelles were modeled in detail. The convolution of the center distribution of the micelles, obtained from Monte Carlo simulations of hard spheres at a hard wall, and the projected density of the micelle showed excellent agreement with the experimental profiles. [S1063-651X...

  1. Self-Assembly of Amphiphilic Anthracene-Functionalized β-Cyclodextrin (CD-AN) through Multi-Micelle Aggregation.

    Science.gov (United States)

    Zhang, Yuannan; Xu, Hongjie; Ma, Xiaodong; Shi, Zixing; Yin, Jie; Jiang, Xuesong

    2016-06-01

    Multi-micelle aggregation (MMA) mechanism is widely acknowledged to explicate large spherical micelles self-assembly, but the process of MMA during self-assembly is hard to observe. Herein, a novel kind of strong, regular microspheres fabricated from self-assembly of amphiphilic anthracene-functionalized β-cyclodextrin (CD-AN) via Cu(I)-catalyzed azide-alkyne click reactions is reported. The obtained CD-AN amphiphiles can self-assemble in water from primary core-shell micelles to secondary aggregates with the diameter changing from several tens nm to around 600-700 nm via MMA process according to the images of scanning electron microscopy, transmission electron microscopy, and atomic force microscopy as well as the dynamic light scattering measurements, followed by further crosslinking through photo-dimerization of anthracene. What merits special attention is that such photo-crosslinked self-assemblies are able to disaggregate reversibly into primary nanoparticles when changing the solution conditions, which is benefited from the designed regular structure of CD-AN and the rigid ranging of anthracene during assembly, thus confirming the process of MMA. PMID:27145434

  2. pH-Responsive Intra- and Inter-Molecularly Micelle Formation of Anionic Diblock Copolymer in Water

    Directory of Open Access Journals (Sweden)

    Masanobu Mizusaki

    2016-02-01

    Full Text Available Poly(sodium2-(acrylamido-2-methylpropanesulfonate-block-poly(sodium11-(acrylamidoundecanoate (PAMPS–PAaU was synthesized via reversible addition-fragmentation chain transfer (RAFT-controlled radical polymerization. The “living” polymerization of PAaU was evidenced by the fact that the molecular weight distribution was narrow (Mw/Mn = 1.23. The pH-induced association behavior of PAMPS–PAaU in 0.1 M NaCl aqueous solutions as a function of solution pH was investigated by 1H NMR spin-spin relaxation time, dynamic light scattering (DLS, static light scattering (SLS, and fluorescence probe techniques. These results indicated that PAMPS–PAaU formed polymer micelles in 0.1 M NaCl aqueous solutions at pH < 9. At pH = 8–9, the polymer formed the micelles intramolecularly due to hydrophobic self-association of the PAaU block within the single polymer chain. On the other hand, at pH < 8, micellization occurred intermolecularly to form polymer micelles comprising hydrophobic PAaU cores and hydrophilic PAMPS shells.

  3. High-resolution modelling of AOT40 and stomatal ozone uptake in wheat and grassland: A comparison between 2000 and the hot summer of 2003 in Switzerland

    International Nuclear Information System (INIS)

    The aim was to compare the ozone risk for agricultural crops in Switzerland during the hot and dry year 2003 with the more 'normal' situation in 2000. An improved version of the Ozone DEposition Model ODEM was used at a 2 x 2 km resolution. The distribution of the index AOT40 was compared with the accumulated stomatal ozone flux, AFst. Averaged AOT40 at 2 m and at canopy height was much higher in 2003 than in 2000, but inter-annual differences in AFst for wheat and grasslands were small due to the limiting effect of low soil water contents in 2003. AOT40 suggested larger potential yield losses in wheat in 2003, while using AFst with a threshold of 6 nmol m-2 s-1 (AFst6) yielded similar estimates for both years. The data show that modelling of AFst can be used to differentiate ozone risks between regions and years at a national scale. - A national-scale assessment based on stomatal ozone flux, but not on AOT40, revealed similar risks for crops in years with different climates and ozone levels

  4. Extension to the charge fluctuation model for the prediction of the conductivity of apolar, reverse micellar systems.

    Science.gov (United States)

    Michor, Edward L; Berg, John C

    2012-11-13

    This paper presents an extension to current theory regarding charging behavior in apolar, micellar systems. Electrical conductivity in such systems accompanying the formation of neutral reverse micelles is commonly explained by the possibility of intermicellar collisions resulting in a pair of oppositely charged micelles. The sequestration of the resulting charges within the micelles prevents their immediate recombination. The current theory underlying the charging process has thus far been applied in only approximate form, and is only used to validate experimental trends and to abstract values for the fraction of charged micelles. The extended theory proposed here uses knowledge of the solvent and surfactant characteristics, together with water content, to predict solution conductivity in absolute terms. It is verified in experiments with the solvent Isopar-L and surfactants Aerosol OT, OLOA 11000, and Span 80, in which significant differences from the approximate theory are observed. PMID:23098157

  5. Dielectric Analysis for the Spherical and Rodlike Micelle Aggregates Formed from a Gemini Surfactant: Driving Forces of Micellization and Stability of Micelles.

    Science.gov (United States)

    Wang, Shanshan; Zhao, Kongshuang

    2016-08-01

    The self-aggregation behavior of Gemini surfactant 12-2-12 (ethanediyl-1,2-bis(dimethyldodecylammonium bromide)) in water was investigated by dielectric relaxation spectroscopy (DRS) over a frequency range from 40 Hz to 110 MHz. Dielectric determination shows that well-defined spherical micelles formed when the concentration of the surfactant was above a critical micelle concentration CMC1 of 3 mM and rodlike micelles formed above CMC2, 16 mM. The formation mechanism of the spherical micelles and their transition mechanism to clubbed micelles were proposed by calculating the degree of counterion binding of the micelles. The interactions between the head groups and the hydrophobic chains of the surfactant led to the formation of the micelles, whereas the transition is mainly attributed to the interaction among the hydrophobic chains. By analyzing the dielectric relaxation observed at about 10(7) Hz based on the interface polarization theory, the permittivity and conductivity of micelle aggregates (spherical and clubbed) and volume fraction of micelles were calculated theoretically as well as the electrical properties of the solution medium. Furthermore, we also calculated the electrokinetic parameters of the micelle particle surface, surface conductivity, surface charge density, and zeta potential, using the relaxation parameters and phase parameters. On the basis of these results, the balance of forces controlling morphological transitions, interfacial electrokinetic properties, and the stability of the micelle aggregates was discussed. PMID:27396495

  6. The Use of Dodecylphosphocholine Micelles in Solution NMR

    Science.gov (United States)

    Kallick, D. A.; Tessmer, M. R.; Watts, C. R.; Li, C. Y.

    Dodecylphosphocholine (DPC) micelles are useful as a model membrane system for solution NMR. Several new observations on dodecylphosphocholine micelles and their interactions with opioid peptides are described. The optimal lipid concentration has been investigated for small peptide NMR studies in DPC micelles for two opioid peptides, a 5-mer and a 17-mer. In contrast to reports in the literature, identical 2D spectra have been observed at low and high lipid concentrations. The chemical shift of resolved peptide proton resonances has been followed as a function of added lipid and indicates that there are changes in the chemical shifts above the critical micelle concentration and up to a ratio of 7:1 (lipid:peptide) for the 17-mer, and 9.6:1 for the 5-mer. These results suggest that conformational changes occur in the peptide significantly above the critical micelle concentration, up to a lipid:peptide ratio which is dependent upon the peptide, here ranging from 7:1 to 9.6:1. To address the stoichiometry more directly, the diffusion coefficients of the lipid alone and the lipid with peptide have been measured using pulsed-field gradient spin-echo NMR experiments. These data have been used to calculate the hydrodynamic radius and the aggregation number of the micelle with and without peptide and show that the aggregation number of the peptide-lipid complex increases at high lipid concentrations without a concomitant change in the peptide conformation. Last, several protonated impurities have been observed in the commercial preparation of DPC which resonate in the amide proton region of the NMR spectrum. These results are significant for researchers using DPC micelles and illustrate that both care in sample preparation and the stoichiometry are important issues with the use of DPC as a model membrane.

  7. Micelles as Soil and Water Decontamination Agents.

    Science.gov (United States)

    Shah, Afzal; Shahzad, Suniya; Munir, Azeema; Nadagouda, Mallikarjuna N; Khan, Gul Shahzada; Shams, Dilawar Farhan; Dionysiou, Dionysios D; Rana, Usman Ali

    2016-05-25

    Contaminated soil and water pose a serious threat to human health and ecosystem. For the treatment of industrial effluents or minimizing their detrimental effects, preventive and remedial approaches must be adopted prior to the occurrence of any severe environmental, health, or safety hazard. Conventional treatment methods of wastewater are insufficient, complicated, and expensive. Therefore, a method that could use environmentally friendly surfactants for the simultaneous removal of both organic and inorganic contaminants from wastewater is deemed a smart approach. Surfactants containing potential donor ligands can coordinate with metal ions, and thus such compounds can be used for the removal of toxic metals and organometallic compounds from aqueous systems. Surfactants form host-guest complexes with the hydrophobic contaminants of water and soil by a mechanism involving the encapsulation of hydrophobes into the self-assembled aggregates (micelles) of surfactants. However, because undefined amounts of surfactants may be released into the aqueous systems, attention must be paid to their own environmental risks as well. Moreover, surfactant remediation methods must be carefully analyzed in the laboratory before field implementation. The use of biosurfactants is the best choice for the removal of water toxins as such surfactants are associated with the characteristics of biodegradability, versatility, recovery, and reuse. This Review is focused on the currently employed surfactant-based soil and wastewater treatment technologies owing to their critical role in the implementation of certain solutions for controlling pollution level, which is necessary to protect human health and ensure the quality standard of the aquatic environment. PMID:27136750

  8. Preparation of Bone-like Hydroxyapatite via a Reverse Microemulsion

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Bone-like hydroxyapatite( HAp ) powders were synthesized using a reverse microemulsion method without further calcine processing. Synthesis conditions had significant effects on the formation of HAp. According to the results of XRD patterns and FTIR spectra, the obtained needle shape HAp powder with poorly crystallized and carbonate substitution was chemically and structurally similar to the human bone powders. The alkaline of emulsion was responsible for the obtained HAp without calcine route, and carbonate came from CO2 in air during preparation. By ultrasonic treatment, the morphology of HAp particles changed from spherical to needle shape for the reverse micelles broke up due to the high energy of ultrasonic.

  9. Changes in the bending modulus of AOT based microemulsions induced by the incorporation of polymers in the water core.

    Science.gov (United States)

    Kuttich, Björn; Grefe, Ann-Kathrin; Stühn, Bernd

    2016-08-14

    The bending modulus κ is known to be a crucial parameter for the stability of the droplet phase in microemulsion systems. For AOT based water in oil microemulsions the bending modulus of the surfactant has values close to kBT but can be influenced by the presence of polymers. In this work we focus on the water soluble polymer polyethylene glycol and how it influences the bending modulus. An increase by a factor of three is found. For the correct evaluation of the bending modulus via percolation temperatures and droplet radii, thus by dielectric spectroscopy and small angle X-ray scattering, the determination of the radii right at the percolation temperature is crucial as we will show, although it is often neglected. In order to precisely determine the droplet radii we will present a global fitting model which provides reliable results with a minimum number of free fitting parameters. PMID:27416768

  10. Director tumbling of nematic wormlike micelles under shear: time-resolved rheo-NMR experiments

    International Nuclear Information System (INIS)

    Nematic liquid crystals show a complex flow behavior due to the coupling between orientation and flow. Some materials show a stable director orientation in steady shear flow (flow aligning), while for others no stable director orientation exists (tumbling). Director tumbling gives rise to oscillations of shear and normal stresses in rheological experiments and can be detected by optical methods, for example by microscopy or birefringence measurements. We have used deuterium NMR spectroscopy to observe shear-induced director orientations. In the lyotropic system cetylpyridinium chloride/hexanol/brine, which forms a nematic phase of wormlike micelles, time-resolved observations of the director orientation by means of deuterium NMR spectroscopy of D2O have been possible for the first time. The time-dependence of the director orientations in both shear start-up and flow-reversal experiments will be presented. (orig.)

  11. Preparation and photochromic properties of layer-by-layer self-assembly films and light-responsive micelles based on amphiphilic naphthopyran derivative.

    Science.gov (United States)

    Zhang, Meiduo; Li, Dehua; He, Yi; Wang, Guang

    2015-12-01

    An amphiphilic naphthopyran derivative (DSNP) with negative-charged di-sulfatoethoxy was first designed and synthesized. DSNP was used to prepare the LBL self-assembly films with cationic quaternized poly(4-vinylpyridine) (P4VPQ). The multilayer assembly process was monitored via UV-Vis spectra and the DSNP displayed a significant slow fading rate in film. In addition, DSNP was also used as the light-responsive group to fabricate light-responsive micelles with polyethylene glycol-triethylamine bromide (PEG-NEt3). The photoisomerization of naphthopyran moieties can rapidly and reversibly tune the disassembly and re-assembly of the micelles. The changes of fluorescent spectra of Nile Red (NR) in water solution of polymeric micelles demonstrated that the polymeric micelle can be used as nanocarriers to encapsulate, release and re-encapsulate guest solutes on demand controlling of light irradiation. The results indicate that the amphiphilic naphthopyran can be used in both optical-switches and biomedical area for drug delivery. PMID:26162340

  12. Reversible dementias

    OpenAIRE

    Tripathi, Manjari; Vibha, Deepti

    2009-01-01

    In recent years, more attention has been given to the early diagnostic evaluation of patients with dementia which is essential to identify patients with cognitive symptoms who may have treatable conditions. Guidelines suggest that all patients presenting with dementia or cognitive symptoms should be evaluated with a range of laboratory tests, and with structural brain imaging with computed tomography (CT) or magnetic resonance imaging (MRI). While many of the disorders reported as ‘reversible...

  13. Role of Synthetic and Dimensional Synthetic Organic Chemistry in Block Copolymer Micelle Nanosensor Engineering

    OpenAIRE

    Ek, Pramod Kumar; Andresen, Thomas Lars; Almdal, Kristoffer

    2012-01-01

    This thesis investigated the role of amphiphilic triblock copolymer micelle nanomaterials in nanosensors, with emphasis on the synthesis of micelle particle sensors. The thesis is focused on the role of synthetic and dimensional synthetic organic chemistry in amphiphilic triblock core-shellcorona micelle based ratiometric fluorescence pH nanosensor fabrications. Two synthetic strategies such as post micelle modification and mixed micellisation (co-micellisation) were employed for pH nanosenso...

  14. Hydrolytic Degradation of Poly (ethylene oxide)-block-Polycaprolactone Worm Micelles

    OpenAIRE

    Geng, Yan; Discher, Dennis E.

    2005-01-01

    Spherical micelles and nanoparticles made with degradable polymers have been of great interest for therapeutic application, but degradation induced changes in a spherical morphology can be subtle and mechanism/kinetics appears poorly understood. Here, we report the first preparation of giant and flexible worm micelles self-assembled from degradable copolymer poly (ethylene oxide)-block-polycaprolactone. Such worm micelles spontaneously shorten to generate spherical micelles, triggered by poly...

  15. Determination of the aggregation number for micelles by isothermal titration calorimetry

    DEFF Research Database (Denmark)

    Olesen, Niels Erik; Holm, Rene; Westh, Peter

    2014-01-01

    Isothermal titration calorimetry (ITC) has previously been applied to estimate the aggregation number (n), Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) of micellization. However, some difficulties of micelle characterization by ITC still remain; most micelles have aggregation numbers...... insight into optimal design of titration protocols for micelle characterization. By applying the new method, the aggregation number of sodium dodecyl sulphate and glycochenodeoxycholate was determined at concentrations around their critical micelle concentration (CMC)...

  16. Thermosensitive hydrogel containing dexamethasone micelles for preventing postsurgical adhesion in a repeated-injury model

    OpenAIRE

    Qinjie Wu; Ning Wang; Tao He; Jinfeng Shang; Ling Li; Linjiang Song; Xi Yang; Xia Li; Na Luo; Wenli Zhang; Changyang Gong

    2015-01-01

    Tissue adhesion is a common complication after surgery. In this work, a dexamethasone loaded polymeric micelles in thermosensitive hydrogel composite (Dex hydrogel) was prepared, which combined the anti-adhesion barrier with controlled release of anti-adhesion drug. Dexamethasone (Dex) was encapsulated in polymeric micelles (Dex micelles), and then the Dex micelles were loaded into biodegradable and thermosensitive hydrogel. The obtained Dex hydrogel showed a temperature-dependent sol-gel-sol...

  17. Curcumin-Loading-Dependent Stability of PEGMEMA-Based Micelles Affects Endocytosis and Exocytosis in Colon Carcinoma Cells.

    Science.gov (United States)

    Chang, Teddy; Trench, David; Putnam, Joshua; Stenzel, Martina H; Lord, Megan S

    2016-03-01

    Polymeric micelles were formed from poly(poly(ethylene glycol) methyl ether methacrylate)-block-poly(styrene) (P(PEGMEMA)-b-PS) block copolymer of two different chain lengths. The micelles formed were approximately 16 and 46 nm in diameter and used to encapsulate curcumin. Upon loading of the curcumin into the micelles, their size increased to approximately 34 and 80 nm in diameter, respectively, with a loading efficiency of 58%. The unloaded micelles were not cytotoxic to human colon carcinoma cells, whereas only the smaller loaded micelles were cytotoxic after 72 h of exposure. The micelles were rapidly internalized by the cells within minutes of exposure, with the loaded micelles internalized to a greater extent owing to their enhanced stability compared to that of the unloaded micelles. The larger micelles were more rapidly internalized and exocytosed than the smaller micelles, demonstrating the effect of micelle size and drug loading on drug delivery and cytotoxicity. PMID:26755445

  18. Biomimetic oral mucin from polymer micelle networks

    Science.gov (United States)

    Authimoolam, Sundar Prasanth

    Mucin networks are formed by the complexation of bottlebrush-like mucin glycoprotein with other small molecule glycoproteins. These glycoproteins create nanoscale strands that then arrange into a nanoporous mesh. These networks play an important role in ensuring surface hydration, lubricity and barrier protection. In order to understand the functional behavior in mucin networks, it is important to decouple their chemical and physical effects responsible for generating the fundamental property-function relationship. To achieve this goal, we propose to develop a synthetic biomimetic mucin using a layer-by-layer (LBL) deposition approach. In this work, a hierarchical 3-dimensional structures resembling natural mucin networks was generated using affinity-based interactions on synthetic and biological surfaces. Unlike conventional polyelectrolyte-based LBL methods, pre-assembled biotin-functionalized filamentous (worm-like) micelles was utilized as the network building block, which from complementary additions of streptavidin generated synthetic networks of desired thickness. The biomimetic nature in those synthetic networks are studied by evaluating its structural and bio-functional properties. Structurally, synthetic networks formed a nanoporous mesh. The networks demonstrated excellent surface hydration property and were able capable of microbial capture. Those functional properties are akin to that of natural mucin networks. Further, the role of synthetic mucin as a drug delivery vehicle, capable of providing localized and tunable release was demonstrated. By incorporating antibacterial curcumin drug loading within synthetic networks, bacterial growth inhibition was also demonstrated. Thus, such bioactive interfaces can serve as a model for independently characterizing mucin network properties and through its role as a drug carrier vehicle it presents exciting future opportunities for localized drug delivery, in regenerative applications and as bio

  19. Enzymatically triggered multifunctional delivery system based on hyaluronic acid micelles

    KAUST Repository

    Deng, Lin

    2012-01-01

    Tumor targetability and stimuli responsivity of drug delivery systems (DDS) are key factors in cancer therapy. Implementation of multifunctional DDS can afford targetability and responsivity at the same time. Herein, cholesterol molecules (Ch) were coupled to hyaluronic acid (HA) backbones to afford amphiphilic conjugates that can self-assemble into stable micelles. Doxorubicin (DOX), an anticancer drug, and superparamagnetic iron oxide (SPIO) nanoparticles (NPs), magnetic resonance imaging (MRI) contrast agents, were encapsulated by Ch-HA micelles and were selectively released in the presence of hyaluronidase (Hyals) enzyme. Cytotoxicity and cell uptake studies were done using three cancer cell lines (HeLa, HepG2 and MCF7) and one normal cell line (WI38). Higher Ch-HA micelles uptake was seen in cancer cells versus normal cells. Consequently, DOX release was elevated in cancer cells causing higher cytotoxicity and enhanced cell death. © 2012 The Royal Society of Chemistry.

  20. Multicompartment Micelles From π-Shaped ABC Block Copolymers

    Institute of Scientific and Technical Information of China (English)

    XIA Jun; ZHONG Chong-Li

    2007-01-01

    Dissipative particle dynamics simulations were performed on the morphology and structure of multicompartment micelles formed from n-shaped ABC block copolymers in water. The influences of chain architectures were studied in a systematic way, and a rich variety of morphologies were observed, such as spherical, wormlike,X-shaped, Y-shaped, ribbon-like, layered rod-like, layered disk-like, as well as network morphologies. The simulations show that the distance between the two grafts plays an important role in control of the morphology. Since π-shaped ABC block copolymers can be reduced to linear ABC and star ABC block copolymers, they are good model copolymers for studying the self-assembly of complex block copolymers into micelles. The knowledge obtained in this work as well as the new morphologies identified provide useful information for future rational design and synthesis of novel multicompartment micelles.

  1. Structural characterization of casein micelles: shape changes during film formation

    International Nuclear Information System (INIS)

    The objective of this study was to determine the effect of size-fractionation by centrifugation on the film structure of casein micelles. Fractionated casein micelles in solution were asymmetrically distributed with a small distribution width as measured by dynamic light scattering. Films prepared from the size-fractionated samples showed a smooth surface in optical microscopy images and a homogeneous microstructure in atomic force micrographs. The nano- and microstructure of casein films was probed by micro-beam grazing incidence small angle x-ray scattering (μGISAXS). Compared to the solution measurements, the sizes determined in the film were larger and broadly distributed. The measured GISAXS patterns clearly deviate from those simulated for a sphere and suggest a deformation of the casein micelles in the film. (paper)

  2. Topology, length scales, and energetics of surfactant micelles.

    Science.gov (United States)

    Dhakal, Subas; Sureshkumar, Radhakrishna

    2015-07-14

    We study the morphology, energetics, and kinetics of a self-associating model cationic surfactant in water using large-scale coarse-grained molecular dynamics simulations over time scales that allow for probing micelle recombination dynamics. We develop an algorithm to track micelle contours and quantify various microstructural features such as contour length distribution, persistence length, and mesh size. We predict reliably the end-cap energy and recombination time of micelles, directly from molecular simulations for the first time. We further consider the variation of solution viscosity as a function of salt concentration and show that branched and multiconnected structures govern the experimentally observed anomalous dependence of zero-shear viscosity on salt concentration. Overall, simulation predictions are in good agreement with experiments. PMID:26178125

  3. Formation and degradation of multicomponent multicore micelles: insights from dissipative particle dynamics simulations.

    Science.gov (United States)

    Chen, Houyang; Ruckenstein, Eli

    2013-05-01

    Dissipative particle dynamics (DPD) simulation is employed to examine (i) the multicomponent multicore micelle (MMM) formation from two kinds of star-shaped copolymers: A2B4B4 and C2B4B4 where A, B, and C are the segments of the copolymers and (ii) the degradation of multicomponent multicore micelles. Regarding the micelle formation, single-core micelles with the core composed of two components (SCII), multicomponent multicore micelles with each core composed of two components (MMII), multicomponent multicore micelles with each of the cores composed of one component (MMI), and multicomponent multicore rod micelles (MMRI) are considered. By changing the ratio between the number of segments of one of the polymers and the total number of segments of the two copolymers, the number of cores generated and their composition can be controlled. Considering that only C2B4B4 is degraded to 2C1 + 2B4, it was found that SCII, MMII, and MMI micelles degraded to a single irregular network core, to multicores with cores formed of loose aggregates, and to multicore micelles, respectively. The dynamics of micelle formation has several stages (small aggregates (nuclei) → growth of aggregates → micellization) whereas the dynamics of degradation involves the diffusion of the degraded components inside and outside micelles and the rearrangement of the cores of the micelles into new cores. PMID:23578256

  4. COMPARISON OF DRUG DELIVERY PROPERTIES OF PEG-b-PDHPC MICELLES WITH DIFFERENT COMPOSITIONS

    Institute of Scientific and Technical Information of China (English)

    Chun-yan Long; Ming-ming Sheng; Bin He; Yao Wu; Gang Wang; Zhong-wei Gu

    2012-01-01

    An anti-tumor drug doxombicin was encapsulated in micelles of poly(ethylene glycol)-b-poly(2,2-dihydroxyl-methyl propylene carbonate) (PEG-b-PDHPC) diblock copolymers.The morphology of both blank micelles and drug loaded micelles was characterized by TEM.The in vitro drug release profiles of micelles were investigated.The cytotoxicity of the micelles was evaluated by incubating with Hela tumor cells and 3T3 fibroblasts.The drug loaded micelles were co-cultured with HepG2 cells to evaluate the in vitro anti-tumor efficacies.The results showed that the mean sizes of both micelles with different copolymer compositions increased after being loaded with drugs.The drug release rate of PEG45-b-PDHPC34 micelles was faster than that of rnPEG114-b-PDHPC26 micelles.Both of the two block copolymers were non-toxic.The confocal laser scanning microscopy and flow cytometry results showed that both the drug loaded micelles could be internalized efficiently in HepG2 cells.The PEG45-b-PDHPC34 micelles exhibited higher anti-tumor activity comparing to mPEG114-b-PDHPC26 micelles.

  5. Novel micelle formulations to increase cutaneous bioavailability of azole antifungals.

    Science.gov (United States)

    Bachhav, Y G; Mondon, K; Kalia, Y N; Gurny, R; Möller, M

    2011-07-30

    Efficient topical drug administration for the treatment of superficial fungal infections would deliver the therapeutic agent to the target compartment and reduce the risk of systemic side effects. However, the physicochemical properties of the commonly used azole antifungals make their formulation a considerable challenge. The objective of the present investigation was to develop aqueous micelle solutions of clotrimazole (CLZ), econazole nitrate (ECZ) and fluconazole (FLZ) using novel amphiphilic methoxy-poly(ethylene glycol)-hexyl substituted polylactide (MPEG-hexPLA) block copolymers. The CLZ, ECZ and FLZ formulations were characterized with respect to drug loading and micelle size. The optimal drug formulation was selected for skin transport studies that were performed using full thickness porcine and human skin. Penetration pathways and micellar distribution in the skin were visualized using fluorescein loaded micelles and confocal laser scanning microscopy. The hydrodynamic diameters of the azole loaded micelles were between 70 and 165nm and the corresponding number weighted diameters (d(n)) were 30 to 40nm. Somewhat surprisingly, the lowest loading efficiency (13-fold higher than that from Pevaryl® cream (22.8±3.8 and 1.7±0.6μg/cm(2), respectively). A significant enhancement was also observed with human skin; the amounts of ECZ deposited were 11.3±1.6 and 1.5±0.4μg/cm(2), respectively (i.e., a 7.5-fold improvement in delivery). Confocal laser scanning microscopy images supported the hypothesis that the higher delivery observed in porcine skin was due to a larger contribution of the follicular penetration pathway. In conclusion, the significant increase in ECZ skin deposition achieved using the MPEG-dihexPLA micelles demonstrates their ability to improve cutaneous drug bioavailability; this may translate into improved clinical efficacy in vivo. Moreover, these micelle systems may also enable targeting of the hair follicle and this will be investigated

  6. Fluorescent supramolecular micelles for imaging-guided cancer therapy

    Science.gov (United States)

    Sun, Mengmeng; Yin, Wenyan; Dong, Xinghua; Yang, Wantai; Zhao, Yuliang; Yin, Meizhen

    2016-02-01

    A novel smart fluorescent drug delivery system composed of a perylene diimide (PDI) core and block copolymer poly(d,l-lactide)-b-poly(ethyl ethylene phosphate) is developed and named as PDI-star-(PLA-b-PEEP)8. The biodegradable PDI-star-(PLA-b-PEEP)8 is a unimolecular micelle and can self-assemble into supramolecular micelles, called as fluorescent supramolecular micelles (FSMs), in aqueous media. An insoluble drug camptothecin (CPT) can be effectively loaded into the FSMs and exhibits pH-responsive release. Moreover, the FSMs with good biocompatibility can also be employed as a remarkable fluorescent probe for cell labelling because the maximum emission of PDI is beneficial for bio-imaging. The flow cytometry and confocal laser scanning microscopy analysis demonstrate that the micelles are easily endocytosed by cancer cells. In vitro and in vivo tumor growth-inhibitory studies reveal a better therapeutic effect of FSMs after CPT encapsulation when compared with the free CPT drug. The multifunctional FSM nanomedicine platform as a nanovehicle has great potential for fluorescence imaging-guided cancer therapy.A novel smart fluorescent drug delivery system composed of a perylene diimide (PDI) core and block copolymer poly(d,l-lactide)-b-poly(ethyl ethylene phosphate) is developed and named as PDI-star-(PLA-b-PEEP)8. The biodegradable PDI-star-(PLA-b-PEEP)8 is a unimolecular micelle and can self-assemble into supramolecular micelles, called as fluorescent supramolecular micelles (FSMs), in aqueous media. An insoluble drug camptothecin (CPT) can be effectively loaded into the FSMs and exhibits pH-responsive release. Moreover, the FSMs with good biocompatibility can also be employed as a remarkable fluorescent probe for cell labelling because the maximum emission of PDI is beneficial for bio-imaging. The flow cytometry and confocal laser scanning microscopy analysis demonstrate that the micelles are easily endocytosed by cancer cells. In vitro and in vivo tumor growth

  7. Optical properties of gold colloids formed in inverse micelles

    International Nuclear Information System (INIS)

    We discuss the formation of gold metal colloids in a variety of surfactant/solvent systems. Static and dynamic light scattering, small angle x-ray and neutron scattering, TEM analysis, and UV-visible absorbance are used to characterize the kinetics of formation and final colloid stability. These gold colloids exhibit a dramatic blueshift and broadening of the plasmon resonance with decreasing colloid size. Several types of reduction method are discussed and differences between micelle (water-free) or microemulsions as reaction media are compared. Use of inverse micelles allows smaller clusters to be formed with greater long-term stability

  8. Binding of chloroquine to ionic micelles: Effect of pH and micellar surface charge

    Energy Technology Data Exchange (ETDEWEB)

    Souza Santos, Marcela de, E-mail: marcelafarmausp77@gmail.com [Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, Ribeirão Preto, São Paulo 14040-903 (Brazil); Perpétua Freire de Morais Del Lama, Maria, E-mail: mpemdel@fcfrp.usp.br [Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, Ribeirão Preto, São Paulo 14040-903 (Brazil); Instituto Nacional de Ciência e Tecnologia de Bioanalítica, Departamento de Química Analítica, Universidade Estadual de Campinas, Cidade Universitária Zeferino Vaz, s/n, Campinas, São Paulo 13083-970 (Brazil); Siuiti Ito, Amando, E-mail: amandosi@ffclrp.usp.br [Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes, 3900, Ribeirão Preto, São Paulo 14040-901 (Brazil); and others

    2014-03-15

    The pharmacological action of chloroquine relies on its ability to cross biological membranes in order to accumulate inside lysosomes. The present work aimed at understanding the basis for the interaction between different chloroquine species and ionic micelles of opposite charges, the latter used as a simple membrane model. The sensitivity of absorbance and fluorescence of chloroquine to changes in its local environment was used to probe its interaction with cetyltrimethylammonium micelles presenting bromide (CTAB) and sulfate (CTAS) as counterions, in addition to dodecyl sulfate micelles bearing sodium (SDS) and tetramethylammonium (TMADS) counterions. Counterion exchange was shown to have little effect on drug–micelle interaction. Chloroquine first dissociation constant (pKa{sub 1}) shifted to opposite directions when anionic and cationic micelles were compared. Chloroquine binding constants (K{sub b}) revealed that electrostatic forces mediate charged drug–micelle association, whereas hydrophobic interactions allowed neutral chloroquine to associate with anionic and cationic micelles. Fluorescence quenching studies indicated that monoprotonated chloroquine is inserted deeper into the micelle surface of anionic micelles than its neutral form, the latter being less exposed to the aqueous phase when associated with cationic over anionic assemblies. The findings provide further evidence that chloroquine–micelle interaction is driven by a tight interplay between the drug form and the micellar surface charge, which can have a major effect on the drug biological activity. -- Highlights: • Chloroquine (CQ) pKa{sub 1} increased for SDS micelles and decreased for CTAB micelles. • CQ is solubilized to the surface of both CTAB and SDS micelles. • Monoprotonated CQ is buried deeper into SDS micelles than neutral CQ. • Neutral CQ is less exposed to aqueous phase in CTAB over SDS micelles. • Local pH and micellar surface charge mediate interaction of CQ with

  9. Efficiency of advanced wastewater treatment plant system and laboratory-scale micelle-clay filtration for the removal of ibuprofen residues.

    Science.gov (United States)

    Khalaf, Samer; Al-Rimawi, Fuad; Khamis, Mustafa; Zimmerman, Dikla; Shuali, Uri; Nir, Shlomo; Scrano, Laura; Bufo, Sabino A; Karaman, Rafik

    2013-01-01

    The efficiency of Al-Quds Waste Water Treatment Plant (WWTP), which includes sequential elements as activated sludge, ultrafiltration, activated carbon column and reverse osmosis, to remove spiked ibuprofen, a non steroid anti inflammatory drug (NSAID), was investigated. Kinetic studies in pure water and in the activated sludge indicated that the drug was stable during one month of observation. Besides, the overall performance of the integrated plant showed complete removal of ibuprofen from wastewater. Activated carbon column, which was the last element in the sequence before the reverse osmosis system, yielded 95.7% removal of ibuprofen. Batch adsorptions of the drug by using either activated charcoal or composite micelle-clay system were determined at 25°C and well described by Langmuir isotherms. Octadecyltrimethylammonium (ODTMA) bromide and montmorillonite were used to prepare the micelle-clay adsorbent, for which the adsorption kinetics are much faster than activated charcoal. Results suggest that integrating clay-micelle complex filters within the existing WWTP may be promising in improving removal efficiency of the NSAID. PMID:23688232

  10. Role of Synthetic and Dimensional Synthetic Organic Chemistry in Block Copolymer Micelle Nanosensor Engineering

    DEFF Research Database (Denmark)

    Ek, Pramod Kumar

    This thesis investigated the role of amphiphilic triblock copolymer micelle nanomaterials in nanosensors, with emphasis on the synthesis of micelle particle sensors. The thesis is focused on the role of synthetic and dimensional synthetic organic chemistry in amphiphilic triblock core...... micelles. Shell cross-linking on PEG-b-PAEMA-b-PS micelles was performed by amidation reactions between the amino groups of PAEMA blocks using a di-carboxylic acid cross-linker. Also a dendritic cross-linker based click chemistry was used to stabilize the PEG-b-PAEMA-b-PES micelle having click readied PES...

  11. Doxorubicin-loaded aromatic imine-contained amphiphilic branched star polymer micelles: synthesis, self-assembly, and drug delivery

    Directory of Open Access Journals (Sweden)

    Qiu L

    2015-05-01

    Full Text Available Liang Qiu, Chun-Yan Hong, Cai-Yuan Pan Chinese Academy of Sciences Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui, People’s Republic of China Abstract: Redox- and pH-sensitive branched star polymers (BSPs, BP(DMAEMA-co-MAEBA-co-DTDMA(PMAIGPns, have been successively prepared by two steps of reversible addition–fragmentation chain transfer (RAFT polymerization. The first step is RAFT polymerization of 2-(N,N-dimethylaminoethylmethacrylate (DMAEMA and p-(methacryloxyethoxybenzaldehyde (MAEBA in the presence of divinyl monomer, 2,2'-dithiodiethoxyl dimethacrylate (DTDMA. The resultant branched polymers were used as a macro-RAFT agent in the subsequent RAFT polymerization. After hydrolysis of the BSPs to form BP(DMAEMA-co-MAEBA-co-DTDMA(PMAGPns (BSP-H, the anticancer drug doxorubicin (DOX was covalently linked to branched polymer chains by reaction of primary amine of DOX and aldehyde groups in the polymer chains. Their compositions, structures, molecular weights, and molecular weight distributions were respectively characterized by nuclear magnetic resonance spectra and gel permeation chromatography measurements. The DOX-loaded micelles were fabricated by self-assembly of DOX-containing BSPs in water, which were characterized by transmission electron microscopy and dynamic light scattering. Aromatic imine linkage is stable in neutral water, but is acid-labile; controlled release of DOX from the BSP-H-DOX micelles was realized at pH values of 5 and 6, and at higher acidic solution, fast release of DOX was observed. In vitro cytotoxicity experiment results revealed low cytotoxicity of the BSPs and release of DOX from micelles in HepG2 and HeLa cells. Confocal laser fluorescence microscopy observations showed that DOX-loaded micelles have specific interaction with HepG2 cells. Thus, this type of BSP micelle is an efficient drug delivery system

  12. Droplet polydispersity and shape fluctuations in AOT [bis(2-ethylhexyl)sulfosuccinate sodium salt] microemulsions studied by contrast variation small-angle neutron scattering

    DEFF Research Database (Denmark)

    Arleth, L.; Pedersen, J.S.

    2001-01-01

    Microemulsions consisting of AOT water, and decane or iso-octane are studied in the region of the phase diagram where surfactant covered water droplets are formed. The polydispersity and shape fluctuations of the microemulsion droplets are determined and compared in the two different alkane types....... Conductivity measurements show that there is a pronounced dependence of the temperature behavior of the microemulsion on the type of alkane used. In both cases the microemulsion droplets start to form larger aggregates when the temperature increases. But in the system with decane this aggregation temperature...... occurs at a temperature about 10 degreesC lower than in a similar system with iso-octane. Aggregation phenomena are avoided and the two systems are at approximately the same reduced temperature with respect to the aggregation temperature when the temperature of the AOT/D2O/decane microemulsion is 10...

  13. Biodegradable polymeric micelle-encapsulated doxorubicin suppresses tumor metastasis by killing circulating tumor cells

    Science.gov (United States)

    Deng, Senyi; Wu, Qinjie; Zhao, Yuwei; Zheng, Xin; Wu, Ni; Pang, Jing; Li, Xuejing; Bi, Cheng; Liu, Xinyu; Yang, Li; Liu, Lei; Su, Weijun; Wei, Yuquan; Gong, Changyang

    2015-03-01

    Circulating tumor cells (CTCs) play a crucial role in tumor metastasis, but it is rare for any chemotherapy regimen to focus on killing CTCs. Herein, we describe doxorubicin (Dox) micelles that showed anti-metastatic activity by killing CTCs. Dox micelles with a small particle size and high encapsulation efficiency were obtained using a pH-induced self-assembly method. Compared with free Dox, Dox micelles exhibited improved cytotoxicity, apoptosis induction, and cellular uptake. In addition, Dox micelles showed a sustained release behavior in vitro, and in a transgenic zebrafish model, Dox micelles exhibited a longer circulation time and lower extravasation from blood vessels into surrounding tissues. Anti-tumor and anti-metastatic activities of Dox micelles were investigated in transgenic zebrafish and mouse models. In transgenic zebrafish, Dox micelles inhibited tumor growth and prolonged the survival of tumor-bearing zebrafish. Furthermore, Dox micelles suppressed tumor metastasis by killing CTCs. In addition, improved anti-tumor and anti-metastatic activities were also confirmed in mouse tumor models, where immunofluorescent staining of tumors indicated that Dox micelles induced more apoptosis and showed fewer proliferation-positive cells. There were decreased side effects in transgenic zebrafish and mice after administration of Dox micelles. In conclusion, Dox micelles showed stronger anti-tumor and anti-metastatic activities and decreased side effects both in vitro and in vivo, which may have potential applications in cancer therapy.

  14. Novel technique for generating macrophage foam cells for in vitro reverse cholesterol transport studies.

    Science.gov (United States)

    Sengupta, Bhaswati; Narasimhulu, Chandrakala Aluganti; Parthasarathy, Sampath

    2013-12-01

    Generation of foam cells, an essential step for reverse cholesterol transport studies, uses the technique of receptor-dependent macrophage loading with radiolabeled acetylated LDL. In this study, we used the ability of a biologically relevant detergent molecule, lysophosphatidylcholine (lyso-PtdCho), to form mixed micelles with cholesterol or cholesteryl ester (CE) to generate macrophage foam cells. Fluorescent or radiolabeled cholesterol/lyso-PtdCho mixed micelles were prepared and incubated with RAW 264.7 or mouse peritoneal macrophages. Results showed that such micelles were quite stable at 4°C and retained the solubilized cholesterol during one month of storage. Macrophages incubated with cholesterol or CE (unlabeled, fluorescently labeled, or radiolabeled)/lyso-PtdCho mixed micelles accumulated CE as documented by microscopy, lipid staining, labeled oleate incorporation, and by TLC. Such foam cells unloaded cholesterol when incubated with HDL but not with oxidized HDL. We propose that stable cholesterol or CE/lyso-PtdCho micelles would offer advantages over existing methods. PMID:24115226

  15. Micelle hydrogels for three-dimensional dose verification

    Science.gov (United States)

    Babic, S.; Battista, J.; Jordan, K.

    2009-05-01

    Gelatin hydrogels form a transparent and colourless matrix for polymerization or chromic reactions initiated by absorption of ionizing radiation. Generally, hydrogel chemistries have been limited to water soluble reactants. Work to adapt a water insoluble colourless leuco dye to coloured dye conversion reaction in hydrogels, led to the idea that micelles (i.e. tiny aggregates of surfactant molecules) may provide the necessary polar and nonpolar hybrid environment. Both leucomalachite green and leuco crystal violet radiochromic gels have been developed as three-dimensional (3-D) radiochromic dosimeters for optical computed tomography (CT) scanners. It has been found that the post-irradiation diffusion rates strongly correlate with the solubility of the leuco dyes. Since the crystal violet dye is more soluble in the micelle than in the surrounding water, the dose distribution degrades at the slower rate of micelle diffusion, thus yielding stable images of dose. A dosimetric characterization of leucomalachite green and leuco crystal violet gels, respectively, reveals that tissue equivalent micelle hydrogels are promising dosimeters for radiation therapy 3-D dose verification.

  16. Polymeric micelles in anticancer therapy : targeting, imaging and triggered release

    NARCIS (Netherlands)

    Oerlemans, Chris; Bult, Wouter; Bos, Mariska; Storm, Gert; Nijsen, J Frank W; Hennink, Wim E

    2010-01-01

    Micelles are colloidal particles with a size around 5-100 nm which are currently under investigation as carriers for hydrophobic drugs in anticancer therapy. Currently, five micellar formulations for anticancer therapy are under clinical evaluation, of which Genexol-PM has been FDA approved for use

  17. Radiolabeling of liposomes and polymeric micelles with PET-isotopes

    DEFF Research Database (Denmark)

    Jensen, Andreas Tue Ingemann

    . 64Cu allows longer scans (up to 48 hours), which mirrors the duration of nanoparticle pharmacokinetics. It is a metal and must be attached to polymeric micelles by covalently conjugated chelators. DOTA and CB‐TE2A are two such chelators, but DOTA is widely believed to be unstable in‐vivo. DOTA and CB...... mice. These micelles were 20‐45 nm. They showed good tumor uptake (4‐5 %ID/g, 48h) and limited uptake in liver (5‐7 %ID/g, 48h) and spleen (3‐6 %ID/g, 48h). It was concluded that there did not seem to be a significant difference between DOTA and CB‐TE2A in‐vivo. In addition, crosslinked micelles (with......This thesis is divided into three separate chapters that can be read independently. Chapter 1 is a general introduction, touching upon liposomes and polymeric micelles and radiolabeling with 18F and 64Cu. Chapter 2 and 3 address two separate research projects, each described below. A complete...

  18. SANS study of nanoparticles based on block copolymer micelles

    Czech Academy of Sciences Publication Activity Database

    Pleštil, Josef; Pospíšil, Herman; Kuklin, A. I.

    Dubna: Joint Institute for Nuclear Research, Lomonosov Moscow State University, 2005. s. 22. ISBN 5-9530-0086-3. [Workshop on Investigations at the IBR-2 Pulsed Reactor /4./. 15.6.2005-18.6.2005, Dubna] R&D Projects: GA ČR GA203/03/0600 Keywords : SANS * block copolymer micelles * nanoparticles Subject RIV: CD - Macromolecular Chemistry

  19. CASEIN MICELLE STRUCTURE: THE PAST AND THE PRESENT

    Science.gov (United States)

    At the heart of the milk system are the colloidal casein–calcium–transport complexes termed the casein micelles. The application of physical chemical techniques such as light, neutron, and X-ray scattering, and Electron Microscopy (EM) has yielded a wealth of experimental detail concerning the struc...

  20. In vivo toxicity of cationic micelles and liposomes

    DEFF Research Database (Denmark)

    Knudsen, Kristina Bram; Northeved, Helle; Ek, Pramod Kumar;

    2015-01-01

    This study investigated toxicity of nanocarriers comprised of cationic polymer and lipid components often used in gene and drug delivery, formulated as cationic micelles and liposomes. Rats were injected intravenously with 10, 25 or 100 mg/kg and sacrificed after 24 or 48 h, or 24 h after the las...

  1. Molecular dynamics simulation strategies for protein-micelle complexes.

    Science.gov (United States)

    Cheng, Xi; Kim, Jin-Kyoung; Kim, Yangmee; Bowie, James U; Im, Wonpil

    2016-07-01

    The structure and stability of membrane proteins can vary widely in different detergents and this variability has great practical consequences for working with membrane proteins. Nevertheless, the mechanisms that operate to alter the behavior of proteins in micelles are poorly understood and not predictable. Atomic simulations could provide considerable insight into these mechanisms. Building protein-micelle complexes for simulation is fraught with uncertainty, however, in part because it is often unknown how many detergent molecules are present in the complex. Here, we describe several convenient ways to employ Micelle Builder in CHARMM-GUI to rapidly construct protein-micelle complexes and performed simulations of the isolated voltage-sensor domain of voltage-dependent potassium-selective channel and an antimicrobial peptide papiliocin with varying numbers of detergents. We found that once the detergent number exceeds a threshold, protein-detergent interactions change very little and remain very consistent with experimental observations. Our results provide a platform for future studies of the interplays between protein structure and detergent properties at the atomic level. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov. PMID:26679426

  2. The Critical Micelle Concentration of Asphaltenes as Measured by Calorimetry

    DEFF Research Database (Denmark)

    Andersen, Simon Ivar; Christensen, S. D.

    2000-01-01

    solvent mixture) is titrated with a solution of asphaltene in the same solvent. The asphaltene concentration of the injected solution is at a level above the critical micelle concentration (CMC). In the present paper the procedure is applied in investigation of asphaltenes as well as subfractions...

  3. Reversible Statistics

    DEFF Research Database (Denmark)

    Tryggestad, Kjell

    2004-01-01

    The study aims is to describe how the inclusion and exclusion of materials and calculative devices construct the boundaries and distinctions between statistical facts and artifacts in economics. My methodological approach is inspired by John Graunt's (1667) Political arithmetic and more recent work...... within constructivism and the field of Science and Technology Studies (STS). The result of this approach is here termed reversible statistics, reconstructing the findings of a statistical study within economics in three different ways. It is argued that all three accounts are quite normal, albeit in...... different ways. The presence and absence of diverse materials, both natural and political, is what distinguishes them from each other. Arguments are presented for a more symmetric relation between the scientific statistical text and the reader. I will argue that a more symmetric relation can be achieved by...

  4. Casein polymorphism heterogeneity influences casein micelle size in milk of individual cows.

    Science.gov (United States)

    Day, L; Williams, R P W; Otter, D; Augustin, M A

    2015-06-01

    Milk samples from individual cows producing small (148-155 nm) or large (177-222 nm) casein micelles were selected to investigate the relationship between the individual casein proteins, specifically κ- and β-casein phenotypes, and casein micelle size. Only κ-casein AA and β-casein A1A1, A1A2 and A2A2 phenotypes were found in the large casein micelle group. Among the small micelle group, both κ-casein and β-casein phenotypes were more diverse. κ-Casein AB was the dominant phenotype, and 3 combinations (AA, AB, and BB) were present in the small casein micelle group. A considerable mix of β-casein phenotypes was found, including B and I variants, which were only found in the small casein micelle group. The relative amount of κ-casein to total casein was significantly higher in the small micelle group, and the nonglycosylated and glycosylated κ-casein contents were higher in the milks with small casein micelles (primarily with κ-casein AB and BB variants) compared with the large micelle group. The ratio of glycosylated to nonglycosylated κ-casein was higher in the milks with small casein micelles compared with the milks with large casein micelles. This suggests that although the amount of κ-casein (both glycosylated and nonglycosylated) is associated with micelle size, an increased proportion of glycosylated κ-casein could be a more important and favorable factor for small micelle size. This suggests that the increased spatial requirement due to addition of the glycosyl group with increasing extent of glycosylation of κ-casein is one mechanism that controls casein micelle assembly and growth. In addition, increased electrostatic repulsion due to the sialyl residues on the glycosyl group could be a contributory factor. PMID:25828659

  5. Enantiomeric PLA-PEG block copolymers and their stereocomplex micelles used as rifampin delivery

    International Nuclear Information System (INIS)

    A novelty approach to self-assembling stereocomplex micelles by enantiomeric PLA-PEG block copolymers as a drug delivery carrier was described. The particles were encapsulated by enantiomeric PLA-PEG stereocomplex to form nanoscale micelles different from the microspheres or the single micelles by PLLA or PDLA in the reported literatures. First, the block copolymers of enantiomeric poly(l-lactide)-poly(ethylene-glycol) (PLLA-PEG) and poly(D-lactide)-poly(ethylene-glycol) (PDLA-PEG) were synthesized by the ring-opening polymerization of l-lactide and d-lactide in the presence of monomethoxy PEG, respectively. Second, the stereocomplex block copolymer micelles were obtained by the self-assembly of the equimolar mixtures of enantiomeric PLA-PEG copolymers in water. These micelles possessed partially the crystallized hydrophobic cores with the critical micelle concentrations (cmc) in the range of 0.8-4.8 mg/l and the mean hydrodynamic diameters ranging from 40 to 120 nm. The micelle sizes and cmc values obviously depended on the hydrophobic block PLA content in the copolymer. Compared with the single PLLA-PEG or PDLA-PEG micelles, the cmc values of the stereocomplex micelles became lower and the sizes of the stereocomplex micelles formed smaller. And lastly, the stereocomplex micelles encapsulated with rifampin were tested for the controlled release application. The rifampin loading capacity and encapsulation efficiency by the stereocomplex micelles were higher than those by the single polymer micelles, respectively. The drug release time in vitro was depending on the composites of the block copolymers and also could be controlled by the polymer molecular weight and the morphology of the polymer micelles

  6. Hierarchical Micelles via Polyphilic Interactions: Hydrogen-Bonded Supramolecular Dendrons and Double Immiscible Polymers.

    Science.gov (United States)

    Chen, Senbin; Lechner, Bob-Dan; Meister, Annette; Binder, Wolfgang H

    2016-02-10

    We report a simple strategy to form three-phase segregated hierarchical micelles via a counterbalanced phase segregation/self-assembly process. Our methodology relies on a cooperative polyphilic phase segregation, paralleled by a self-assembly process induced by hydrogen-bonds to afford the generation of supramolecular multicompartment dendrons. The versatile preparation of such hierarchical morphologies is evidenced on the basis of a series of supramolecular dendrons, composed of semifluorinated copolymers, homopolymers, or nonfluorinated polymers. We do have designed and prepared mid- and α,ω-barbiturate (Ba) functionalized poly(n-butyl acrylates), Ba-(PnBuA-Ba)2, together with a series of heterocomplementary α,ω-Hamilton wedge (HW) functionalized polymers via reversible addition-fragmentation chain transfer (co)polymerization. To enable subtle phase segregation processes, the semifluorinated homo- and copolymers HW-P(nBuA-co-PFPA)-HW (prepared via copolymerization of nBuA with 2,2,3,3,3-pentafluoropropyl acrylate (PFPA)) and HW-PPFPA-HW, as well as the nonfluorinated polymer HW-PnBuA-HW and HW-PI-HW (PI, polyisoprene), have been generated. Selective intermolecular complexation between Ba-(PnBuA-Ba)2 and the complementary polymers (such as HW-P(nBuA-co-PFPA)-HW, HW-PPFPA-HW or HW-PI-HW) leads to the successful generation of supramolecular dendrons as evidenced by (1)H NMR and diffusion-ordered NMR spectroscopy, together with the formation of well-defined disc-like nano-objects as demonstrated by microscopy investigations. Transmission electron microscopy demonstrates a unique, uncommon phase behavior showing remarkable three-phase segregated hierarchical micelles, indicative of the desired micellar multicompartments. PMID:26789930

  7. A small-angle neutron scattering study of intermicellar interactions in microemulsions of AOT, water, and near-critical propane

    International Nuclear Information System (INIS)

    Small-angle neutron scattering (SANS) measurements of high-pressure solutions of propane/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/D2O have demonstrated that a water-in-oil microemulsion phase can be formed in propane. The dispersed droplets are, within experimental error, the same size as those formed in conventional microemulsions at the same water-to-surfactant ratio, and the size does not depend on propane density. The interdroplet interaction potential was modeled as a hard-core repulsion augmented by a strong and extremely short range attraction. This model describes droplets whose hydrocarbon tails are strongly attractive to the hydrocarbon tails of adjacent droplets. The SANS fit shows that the magnitude of the tail-tail attractive interactions may be much stronger than the longer range van der Waals type attractive interactions between the water cores of the droplets. These findings confirm results of IR and UV-vis spectroscopic studies of near-critical and supercritical fluid microemulsions

  8. Layers of metal nanoparticles on semiconductors deposited by electrophoresis from solutions with reverse micelles

    Czech Academy of Sciences Publication Activity Database

    Žďánský, Karel; Kacerovský, Pavel; Zavadil, Jiří; Lorinčík, Jan; Fojtík, A.

    Fayetteville : University of Arkansas, 2007. s. t0110063--. [Semiconducting & Insulating Materials Conference - SIMC /14./. 15.05.2007-20.05.2007, Fayetteville] R&D Projects: GA AV ČR KAN400670651 Institutional research plan: CEZ:AV0Z20670512 Keywords : semiconductor junctions * nanostructured materials * semicpnductor devices Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  9. Electrophoresis deposition of metal nanoparticles with reverse micelles onto InP

    Czech Academy of Sciences Publication Activity Database

    Žďánský, Karel; Zavadil, Jiří; Kacerovský, Pavel; Lorinčík, Jan; Vaniš, Jan; Kostka, František; Černohorský, O.; Fojtík, A.; Reboun, J.; Čermák, Jan

    2009-01-01

    Roč. 100, č. 9 (2009), s. 1234-1238. ISSN 1862-5282 Institutional research plan: CEZ:AV0Z20670512; CEZ:AV0Z50200510; CEZ:AV0Z10100521 Keywords : semiconductor junctions * nanostructures * semiconductor devices Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.862, year: 2009

  10. Molecular dynamics study of the aqueous core of a reversed ionic micelle

    Science.gov (United States)

    Linse, Per

    1989-05-01

    The molecular structure and dynamics of a molecular electric double layer have been examined with the molecular dynamics simulation technique. A 50 ps trajectory from a simulation of a model system comprising 50 sodium ions and 1000 water molecules, spherically enclosed by a hydrophobic interface carrying 50 carboxylate groups, has been analyzed. The results show that the water structure is strongly distorted by the strong local fields and that the hydrophobic interface plays only a secondary role. The orientational polarization of the interfacial water molecules has been examined and compared with dielectric continuum theory. The dynamical results of this study show a reduced rate of translational as well as rotational motions of ionic hydrating water by a factor of 2-4 as compared to bulk water.

  11. Synthesis, characterisation and stability of Cu2O nanoparticles produced via reverse micelles microemulsion

    International Nuclear Information System (INIS)

    Cuprite (Cu2O) nanoparticles were synthesized at room temperature via reduction of CuCl2.2H2O by NaBH4 in water/n-heptane microemulsion stabilised by the non-ionic Brij30 surfactant. Whole Powder Pattern Modelling of the X-ray diffraction patterns shows the presence of a bimodal size distribution in the nanopowders, with a fraction of domains in the 10-40 nm range and a smaller one below 10 nm. Linear and planar defects are absent. A relationship between the average size of the larger particles and the quantity of water in the system was obtained. The stability of cuprite under visible light irradiation both during the synthesis and after the preparation was investigated, showing that a self-catalytic conversion of Cu2O into CuO takes place in water.

  12. Synthesis, characterisation and stability of Cu{sub 2}O nanoparticles produced via reverse micelles microemulsion

    Energy Technology Data Exchange (ETDEWEB)

    Dodoo-Arhin, D. [University of Trento, Department of Materials Engineering and Industrial Technologies, via Mesiano 77, 38100 Trento (Italy); Leoni, M., E-mail: Matteo.Leoni@unitn.it [University of Trento, Department of Materials Engineering and Industrial Technologies, via Mesiano 77, 38100 Trento (Italy); Scardi, P. [University of Trento, Department of Materials Engineering and Industrial Technologies, via Mesiano 77, 38100 Trento (Italy); Garnier, E. [Laboratoire de Catalyse en Chimie Organique, UMR CNRS 6503, Universite de Poitiers, 40 Av. du Recteur Pineau, 86022 Poitiers (France); Mittiga, A. [ENEA C.R. Casaccia, via Anguillarese 301, 00123 Roma (Italy)

    2010-08-01

    Cuprite (Cu{sub 2}O) nanoparticles were synthesized at room temperature via reduction of CuCl{sub 2}.2H{sub 2}O by NaBH{sub 4} in water/n-heptane microemulsion stabilised by the non-ionic Brij30 surfactant. Whole Powder Pattern Modelling of the X-ray diffraction patterns shows the presence of a bimodal size distribution in the nanopowders, with a fraction of domains in the 10-40 nm range and a smaller one below 10 nm. Linear and planar defects are absent. A relationship between the average size of the larger particles and the quantity of water in the system was obtained. The stability of cuprite under visible light irradiation both during the synthesis and after the preparation was investigated, showing that a self-catalytic conversion of Cu{sub 2}O into CuO takes place in water.

  13. Synthesis of Barium Lithium Fluoride Nanocrystals Using Reverse Micelles as Microemulsion

    Institute of Scientific and Technical Information of China (English)

    Rui Nian HUA; De Min XIE; Chun Shan SHI

    2004-01-01

    Barium lithium fluoride nanocrystals were synthesized in cetyltrimethylammonium bromide (CTAB)/ 2-octanol/ water microemulsion systems. The impurity peaks in XRD patterns were not determined. The result of SEM confirmed that the average sizes and shape of the BaLiF3 nanocrystals. The formation of BaLiF3 and particles size were strongly affected by water content. With increasing water content and reaction times, the size of the particle increases. Meanwhile, the solvent was also found to play a key role in the synthesis of the BaLiF3 nanocrystals.

  14. Radiolabeling of liposomes and polymeric micelles with PET-isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Ingemann Jensen, A.T.

    2013-06-01

    This thesis is divided into three separate chapters that can be read independently. Chapter 1 is a general introduction, touching upon liposomes and polymeric micelles and radiolabeling with 18F and 64Cu. Chapter 2 and 3 address two separate research projects, each described below. A complete reference list is compiled in the end, immediately after the three chapters. This is followed by the supplementary information, divided into appropriate sections. Finally, the two first-authored manuscripts are attached as appendices. Chapter 1. The field of nanoparticulate drug delivery has been hailed as a revolution in modern therapeutics, especially in chemotherapy. A major reason is the ability of nanoparticles to accumulate in tumor tissue. Liposomes are the classic nanoparticle, consisting of a lipid membrane with an aqueous core. Polymeric micelles are made from amphiphilic detergent-like copolymers, that self-assemble in water. Therapy with nanoparticles is hampered by often poor tumor accumulation, combined with massive uptake by macrophages in the liver and spleen. For this reason, visualizing nanoparticle pharmacokinetics in-vivo is a valuable tool in the on-going research. Such visualization can be done by labeling with radio isotopes. Isotopes that emit positrons (PET-isotopes) can be detected by PET (positron emission tomography) technology, an accurate technique that has gained popularity in recent years. PET-isotopes of interest include 18F and 64Cu. In addition to being a research tool, radiolabeled nanoparticles hold promise as a radiopharmaceutical in themselves, as a means of imaging tumor tissue, aiding in diagnosis and surgery. Chapter 2. A method for labeling liposomes with 18F (97% positron decay, T = 110 min) was investigated. 18F is widely available, but is hampered by a short half-life only allowing up to 8 hours scans. 18F must be covalently attached to components of the liposome. By binding to a lipid, it can be stably lodged in the membrane. A

  15. Mesoscale Simulations and Experimental Studies of pH-Sensitive Micelles for Controlled Drug Delivery.

    Science.gov (United States)

    Wang, Yan; Li, Qiu Yu; Liu, Xu Bo; Zhang, Can Yang; Wu, Zhi Min; Guo, Xin Dong

    2015-11-25

    The microstructures of doxorubicin-loaded micelles prepared from block polymers His(x)Lys10 (x = 0, 5, 10) conjugated with docosahexaenoic acid (DHA) are investigated under different pH conditions, using dissipative particle dynamics (DPD) simulations. The conformation of micelles and the DOX distributions in micelles were obviously influenced by pH values and the length of the histidine segment. At pH >6.0, the micelles self-assembled from the polymers were dense and compact. The drugs were entrapped well within the micellar core. The particle size increases as the histidine length increases. With the decrease of pH value to be lower than 6.0, there was no distinct difference for the micelles self-assembled from the polymer without histidine residues. However, the micelles prepared from the polymers with histidine residues shows a structural transformation from dense to swollen conformation, leading to an increased particle size from 10.3 to 14.5 DPD units for DHD-His10Lys10 micelles. This structural transformation of micelles can accelerate the DOX release from micelles under lower pH conditions. The in vitro drug release from micelles is accelerated by the decrease of pH value from 7.4 (physiological environment) to 5.0 (lysosomal environment). The integration of simulation and experiments might be a valuable method for the optimization and design of biomaterials for drug delivery with desired properties. PMID:26539742

  16. The fine-tuning of thermosensitive and degradable polymer micelles for enhancing intracellular uptake and drug release in tumors.

    Science.gov (United States)

    Li, Wei; Li, Jinfeng; Gao, Jie; Li, Bohua; Xia, Yu; Meng, Yanchun; Yu, Yongsheng; Chen, Huaiwen; Dai, Jianxin; Wang, Hao; Guo, Yajun

    2011-05-01

    Focusing on high temperature and low pH of tumor tissue, we prepared temperature and pH responsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide-b-lacitde) (PID(118)-b-PLA(59)) and poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide-b-ε-caprolactone) (PID(118)-b-PCL(60)) diblock copolymers with symmetric hydrophobic blocks by the reversible addition-fragmentation chain transfer (RAFT). The corresponding dual functional polymeric micelles were fabricated by dialysis methods. Their well-defined core-shell structure was characterized by (1)H NMR in D(2)O and further confirmed by TEM. Their structural and physical chemistry properties such as diameters (D), core corona dimension (R(core), R(shell)), distribution (PDI), M(w), aggregation number (N(agg)), second virial coefficient (A(2)), critical micellization concentration (CMC) and z-potential were firstly systemically investigated by dynamic and static laser light scattering. The volume phase transition temperature (VPTT) was around 40 °C above which the intracellular uptake of adriamycin (ADR) was significantly enhanced. Both flow cytometry and fluorescent microscopy showed that the ADR transported by these micelles was about 4 times higher than that by the commercial ADR formulation Taxotere®. In vitro cytotoxicity assay against N-87 cancer cell and confocal laser scanning microscopy (CLSM) also confirmed such promoting efficiency. In addition, it was interesting to find that cell surviving bounced back as T = 42 °C due to the inter-micellar aggregation. The well clarified mechanism strongly support that our finely tailored dual functional core-shell micelles are potent in enhancing cellular uptake and drug release. PMID:21377724

  17. Silver chloride micelle-induced tuning of pseudocapacitive manganese dioxide

    International Nuclear Information System (INIS)

    Ag-doped pseudocapacitive MnO2 materials are synthesized by reacting MnO4− with Mn2+ solution intentionally tuned with AgCl micelles. AgCl micelles serve as inducing template and play dual role for MnO2 growth: porosity generator and Ag-doping agent. The AgCl micelle–induced MnO2 has higher porosity, higher specific surface area, higher electrical conductivity and better ion diffusion, thus exhibiting dramatically improved pseduocapacitance and charge-discharge performance. Compared with pure MnO2, the prepared MnO2 containing 5 atomic percent of Ag exhibits almost doubled specific capacitance (488F g−1) and the existence of Ag dopant in MnO2 enhances the charge-discharge efficiency

  18. Folding of DsbB in mixed micelles

    DEFF Research Database (Denmark)

    Otzen, Daniel

    2003-01-01

    sensitive to changes in lipid and detergent composition. As an attempt to overcome this problem, I present a kinetic analysis of the folding of a membrane protein, disulfide bond reducing protein B (DsbB), in a mixed micelle system consisting of varying molar ratios of sodium dodecyl sulfate (SDS) and...... dodecyl maltoside (DM). This analysis incorporates both folding and unfolding rates, making it possible to determine both the stability of the native state and the process by which the protein folds. Refolding and unfolding occur on the second to millisecond timescale and involve only one relaxation phase...... data are always open to alternative interpretations, time-resolved studies in mixed micelles provide a useful approach to measure membrane protein stability over a wide range of concentrations of SDS and DM, as well as a framework for the future characterization of the DsbB folding mechanism....

  19. Estimation of interfacial acidity of sodium dodecyl sulfate micelles

    Indian Academy of Sciences (India)

    Arghya Dey; G Naresh Patwari

    2011-11-01

    An enhancement in the excited state proton transfer (ESPT) processes of coumarin-102 (C-102) dye was observed upon addition of salicylic acid and hydrochloric acid in sodium dodecyl sulfate (SDS) micellar solution. The phenomenon was observed only in the micellar medium of anionic surfactant SDS and not in case of cationic (CTAB) or neutral (Trition X -100) surfactants. ESPT of C-102 was also observed in aqueous solutions but on addition of very high concentrations of hydrochloric acid. However, on comparing the ratio of the protonated species from the emission spectra in the presence and absence of SDS micelle, a conclusive estimation of the local proton concentration at the Stern layer of SDS micelles could be evaluated.

  20. Construction of the Active Site of Metalloenzyme on Au NC Micelles

    Institute of Scientific and Technical Information of China (English)

    ZHANG, Zhiming; FU, Qiuan; HUANG, Xin; XU, Jiayun; LIU, Junqiu; SHEN, Jiacong

    2009-01-01

    For developing an efficient nanoenzyme system with self-assembly strategy, gold nanocrystal micelles (Au NC micelles) with inserted catalytic Zn(Ⅱ) centers were constructed by self-assembly of a catalytic ligand [N,N-bis(2-aminoethyl)-N'dodecylethylenediamine] Zn(Ⅱ) complexes (Zn(Ⅱ)L) on the surface of Au NC via hy- drophobic interaction. The functionalized Au NC micelles acted as an excellent nanoenzyme model for imitating ribonuclease. The catalytic capability of the Au NC micelles was evaluated by accelerating the cleavage of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP). These functionalized Au NC micelles exhibited considerable ri- bonuclease-like activities by a factor of 4.9×104 (kcat/kuncat) for the cleavage of HPNP in comparison to the sponta- neous cleavage of HPNP at 37℃. The catalytic capability of the functionalized Au NC micelles can be considera- bly compared to other models reported previously as nanoenzymes under the comparable conditions.

  1. Interactions between tea catechins and casein micelles and their impact on renneting functionality.

    Science.gov (United States)

    Haratifar, Sanaz; Corredig, Milena

    2014-01-15

    Many studies have shown that tea catechins bind to milk proteins. This research focused on the association of tea polyphenols with casein micelles, and the consequences of the interactions on the renneting behaviour of skim milk. It was hypothesized that epigallocatechin-gallate (EGCG), the main catechin present in green tea, forms complexes with the casein micelles and that the association modifies the processing functionality of casein micelles. The binding of EGCG to casein micelles was quantified using HPLC. The formation of catechin-casein micelles complexes affected the rennet induced gelation of milk, and the effect was concentration dependent. Both the primary as well as the secondary stage of gelation were affected. These experiments clearly identify the need for a better understanding of the effect of tea polyphenols on the processing functionality of casein micelles, before milk products can be used as an appropriate platform for delivery of bioactive compounds. PMID:24054208

  2. Stability of Self-Assembled Polymeric Micelles in Serum

    OpenAIRE

    Lu, Jiao; Owen, Shawn C.; Shoichet, Molly S.

    2011-01-01

    The stability of polymeric nanoparticles in serum is critical to their use in drug delivery where dilution after intravenous injection often results in nanoparticle disassembly and drug unloading; however, few investigate this in biologically relevant media. To gain greater insight into nanoparticle stability in blood, the stability of self-assembled polymeric micelles of poly(d,l-lactide-co-2-methyl-2-carboxytrimethylene carbonate)-g-poly(ethylene glycol), P(LA-co-TMCC)-g-PEG, were tested in...

  3. Polymer Micelles with Crystalline Cores for Thermally Triggered Release

    OpenAIRE

    Glover, Amanda L.; Nikles, Sarah M.; Nikles, Jacqueline A.; Brazel, Christopher S.; David E. Nikles

    2012-01-01

    Interest in the use of poly(ethylene glycol)-b-polycaprolactone diblock copolymers in a targeted, magnetically triggered drug delivery system has led to this study of the phase behavior of the polycaprolactone core. Four different diblock copolymers were prepared by the ring opening polymerization of caprolactone from the alcohol terminus of poly(ethylene glycol) monomethylether, Mn ~ 2,000. The critical micelle concentration depended on the degree of polymerization for the polycaprolactone b...

  4. PEGylated Albumin-Based Polyion Complex Micelles for Protein Delivery.

    Science.gov (United States)

    Jiang, Yanyan; Lu, Hongxu; Chen, Fan; Callari, Manuela; Pourgholami, Mohammad; Morris, David L; Stenzel, Martina H

    2016-03-14

    An increasing amount of therapeutic agents are based on proteins. However, proteins as drug have intrinsic problems such as their low hydrolytic stability. Delivery of proteins using nanoparticles has increasingly been the focus of interest with polyion complex micelles, prepared from charged block copolymer and the oppositely charged protein, as an example of an attractive carrier for proteins. Inspired by this approach, a more biocompatible pathway has been developed here, which replaces the charged synthetic polymer with an abundant protein, such as albumin. Although bovine serum albumin (BSA) was observed to form complexes with positively charged proteins directly, the resulting protein nanoparticle were not stable and aggregated to large precipitates over the course of a day. Therefore, maleimide functionalized poly(oligo (ethylene glycol) methyl ether methacrylate) (MI-POEGMEMA) (Mn = 26000 g/mol) was synthesized to generate a polymer-albumin conjugate, which was able to condense positively charged proteins, here lysozyme (Lyz) as a model. The PEGylated albumin polyion complex micelle with lysozyme led to nanoparticles between 15 and 25 nm in size depending on the BSA to Lyz ratio. The activity of the encapsulated protein was tested using Sprouty 1 (C-12; Spry1) proteins, which can act as an endogenous angiogenesis inhibitor. Condensation of Spry1 with the PEGylated albumin could improve the anticancer efficacy of Spry1 against the breast cancer cells lowering the IC50 value of the protein. Furthermore, the high anticancer efficacy of the POEGMEMA-BSA/Spry1 complex micelle was verified by effectively inhibiting the growth of three-dimensional MCF-7 multicellular tumor spheroids. The PEGylated albumin complex micelle has great potential as a drug delivery vehicle for a new generation of cancer pharmaceuticals. PMID:26809948

  5. Design and characterization of multicompartment micelles in aqueous solution

    OpenAIRE

    Kubowicz, Stephan

    2005-01-01

    Self-assembly of polymeric building blocks is a powerful tool for the design of novel materials and structures that combine different properties and may respond to external stimuli. In the past decades, most studies were focused on the self-assembly of amphiphilic diblock copolymers in solution. The dissolution of these block copolymers in a solvent selective for one block results mostly in the formation of micelles. The micellar structure of diblock copolymers is inherently limited to a homo...

  6. Polymeric micelles for solubilization and targeting of hydrophobic drugs

    OpenAIRE

    Miller, Tobias

    2013-01-01

    This thesis focussed on the encapsulation of hydrophobic drugs into polymeric micelles and was intended to show the strengths and limitations of these self-assembling systems in terms of solubilization and drug targeting. Characterization of hydrophobic drug solubilization prior to intravenous injection was one of the key goals of this thesis. For this purpose a novel drug loading procedure was developed based on mechanistic considerations during the loading processes (Chapter 2). The cosolve...

  7. Solving the mystery of the internal structure of casein micelles.

    Science.gov (United States)

    Ingham, B; Erlangga, G D; Smialowska, A; Kirby, N M; Wang, C; Matia-Merino, L; Haverkamp, R G; Carr, A J

    2015-04-14

    The interpretation of milk X-ray and neutron scattering data in relation to the internal structure of the casein micelle is an ongoing debate. We performed resonant X-ray scattering measurements on liquid milk and conclusively identified key scattering features, namely those corresponding to the size of and the distance between colloidal calcium phosphate particles. An X-ray scattering feature commonly assigned to the particle size is instead due to protein inhomogeneities. PMID:25711160

  8. Predicting proton titration in cationic micelle and bilayer environments

    Energy Technology Data Exchange (ETDEWEB)

    Morrow, Brian H.; Shen, Jana K. [Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201 (United States); Eike, David M.; Murch, Bruce P.; Koenig, Peter H. [Computational Chemistry, Modeling and Simulation GCO, Procter and Gamble, Cincinnati, Ohio 45201 (United States)

    2014-08-28

    Knowledge of the protonation behavior of pH-sensitive molecules in micelles and bilayers has significant implications in consumer product development and biomedical applications. However, the calculation of pK{sub a}’s in such environments proves challenging using traditional structure-based calculations. Here we apply all-atom constant pH molecular dynamics with explicit ions and titratable water to calculate the pK{sub a} of a fatty acid molecule in a micelle of dodecyl trimethylammonium chloride and liquid as well as gel-phase bilayers of diethyl ester dimethylammonium chloride. Interestingly, the pK{sub a} of the fatty acid in the gel bilayer is 5.4, 0.4 units lower than that in the analogous liquid bilayer or micelle, despite the fact that the protonated carboxylic group is significantly more desolvated in the gel bilayer. This work illustrates the capability of all-atom constant pH molecular dynamics in capturing the delicate balance in the free energies of desolvation and Coulombic interactions. It also shows the importance of the explicit treatment of ions in sampling the protonation states. The ability to model dynamics of pH-responsive substrates in a bilayer environment is useful for improving fabric care products as well as our understanding of the side effects of anti-inflammatory drugs.

  9. Chain exchange kinetics of block copolymer micelles in ionic liquids

    Science.gov (United States)

    Ma, Yuanchi; Lodge, Timothy

    The chain exchange kinetics of block copolymer micelles has been studied using time-resolved small-angle neutron scattering (TR-SANS), a key tool in determining the average micelle composition in contrast-matched solvents. In this work, PMMA-block-PnBMA was selected as the model block copolymer, which has a LCST behavior in the common ionic liquids, [EMIM][TFSI] and [BMIM][TFSI]. We examined the chain exchange kinetics of three PMMA-block-PnBMA copolymers, with identical PMMA block length (MPMMA = 25000) and different PnBMA block lengths (MPnBMA = 24000, 35000 and 53000); the Flory-Huggins interaction parameter (χ) between the core (PnBMA) and the solvent were varied by mixing [EMIM][TFSI] and [BMIM][TFSI] in different ratios. We found that the relaxation of the initial segregation of h- and d- micelles followed the same form with the time as previously developed by our group. Assuming that single chain expulsion is the rate limiting step, the thermal barrier was found to depend linearly on the core block length (Ncore) . Furthermore, the effect of χ on the chain exchange kinetics will also be discussed.

  10. Multicompartment Core Micelles of Triblock Terpolymers in Organic Media

    Energy Technology Data Exchange (ETDEWEB)

    Schacher, Felix [University of Bayreuth; Walther, Andreas [Helsinki University of Technology, Helsinki, Finland; Ruppel, Markus A [ORNL; Drechsler, Markus [Universitat Bayreuth; Muller, Axel [Universitat Bayreuth

    2009-01-01

    The formation of multicompartment micelles featuring a spheres on sphere core morphology in acetone as a selective solvent is presented. The polymers investigated are ABC triblock terpolymers, polybutadieneb-poly(2-vinyl pyridine)-b-poly(tert-butyl methacrylate) (BVT), which were synthesized via living sequential anionic polymerization in THF. Two polymers with different block lengths of the methacrylate moiety were studied with respect to the formation of multicompartmental aggregates. The micelles were analyzed by static and dynamic light scattering as well as by transmission electron microscopy. Cross-linking of the polybutadiene compartment could be accomplished via two different methods, cold vulcanization and with photopolymerization after the addition of a multifunctional acrylate. In both cases, the multicompartmental character of the micellar core is fully preserved, and the micelles could be transformed into core-stabilized nanoparticles. The successful cross-linking of the polybutadiene core is indicated by 1H NMR and by the transfer of the aggregates into nonselective solvents such as THF or dioxane.

  11. Predicting proton titration in cationic micelle and bilayer environments

    International Nuclear Information System (INIS)

    Knowledge of the protonation behavior of pH-sensitive molecules in micelles and bilayers has significant implications in consumer product development and biomedical applications. However, the calculation of pKa’s in such environments proves challenging using traditional structure-based calculations. Here we apply all-atom constant pH molecular dynamics with explicit ions and titratable water to calculate the pKa of a fatty acid molecule in a micelle of dodecyl trimethylammonium chloride and liquid as well as gel-phase bilayers of diethyl ester dimethylammonium chloride. Interestingly, the pKa of the fatty acid in the gel bilayer is 5.4, 0.4 units lower than that in the analogous liquid bilayer or micelle, despite the fact that the protonated carboxylic group is significantly more desolvated in the gel bilayer. This work illustrates the capability of all-atom constant pH molecular dynamics in capturing the delicate balance in the free energies of desolvation and Coulombic interactions. It also shows the importance of the explicit treatment of ions in sampling the protonation states. The ability to model dynamics of pH-responsive substrates in a bilayer environment is useful for improving fabric care products as well as our understanding of the side effects of anti-inflammatory drugs

  12. Anionic micelles and vesicles induce tau fibrillization in vitro.

    Science.gov (United States)

    Chirita, Carmen N; Necula, Mihaela; Kuret, Jeff

    2003-07-11

    Alzheimer's disease is defined in part by the intraneuronal accumulation of filaments comprised of the microtubule-associated protein tau. In vitro, fibrillization of recombinant tau can be induced by treatment with various agents, including phosphotransferases, polyanionic compounds, and fatty acids. Here we characterize the structural features required for the fatty acid class of tau fibrillization inducer using recombinant full-length tau protein, arachidonic acid, and a series of straight chain anionic, cationic, and nonionic detergents. Induction of measurable tau fibrillization required an alkyl chain length of at least 12 carbons and a negative charge consisting of carboxylate, sulfonate, or sulfate moieties. All detergents and fatty acids were micellar at active concentrations, due to a profound, taudependent depression of their critical micelle concentrations. Anionic surfaces larger than detergent micelles, such as those supplied by phosphatidylserine vesicles, also induced tau fibrillization with resultant filaments originating from their surface. These data suggest that anionic surfaces presented as micelles or vesicles can serve to nucleate tau fibrillization, that this mechanism underlies the activity of fatty acid inducers, and that anionic membranes may serve this function in vivo. PMID:12730214

  13. Polymer Micelles with Cross-Linked Polyanion Core for Delivery of a Cationic Drug Doxorubicin

    OpenAIRE

    Kim, Jong Oh; Kabanov, Alexander V.; Bronich, Tatiana K

    2009-01-01

    Polymer micelles with cross-linked ionic cores were prepared by using block ionomer complexes of poly(ethylene oxide)-b-poly(methacrylic acid) (PEO-b-PMA) copolymer and divalent metal cations as templates. Doxorubicin (DOX), an anthracycline anticancer drug, was successfully incorporated into the ionic cores of such micelles via electrostatic interactions. A substantial drug loading level (up to 50 w/w %) was achieved and it was strongly dependent on the structure of the cross-linked micelles...

  14. Cross-linked pH sensitive polymer micelles for drug delivery systems

    OpenAIRE

    Cajot, Sébastien; Jérôme, Christine

    2009-01-01

    Over the last decade, polymer micelles attracted an increasing interest in drug pharmaceutical research because they could be used as efficient drug delivery systems. Micelles of amphiphilic block copolymers are supramolecular core-shell type assemblies of tens of nanometers in diameter. In principle, the micelles core is usually constructed with biodegradable hydrophobic polymers such as aliphatic polyesters, e.g. poly(ɛ-caprolactone) (PCL), which serves as a reservoir for the incorpora...

  15. Surface tension model for surfactant solutions at the critical micelle concentration

    OpenAIRE

    Burlatsky, S. F.; Atrazhev, V. V.; Dmitriev, D. V.; Sultanov, V. I.; Timokhina, E. N.; Ugolkova, E. A.; Tulyani, S.; Vincitore, A.

    2013-01-01

    A model for the limiting surface tension of surfactant solutions (surface tension at and above the critical micelle concentration, cmc) was developed. This model takes advantage of the equilibrium between the surfactant molecules on the liquid/vacuum surface and in micelles in the bulk at the cmc. An approximate analytical equation for the surface tension at the cmc was obtained. The derived equation contains two parameters, which characterize the intermolecular interactions in the micelles, ...

  16. Polymeric micelles and molecular modeling applied to the development of radiopharmaceuticals

    OpenAIRE

    Sibila Roberta Marques Grallert; Carlota Oliveira Rangel-Yagui; Kerly Fernanda Mesquita Pasqualoto; Leoberto Costa Tavares

    2012-01-01

    Micelles composed of amphiphilic copolymers linked to a radioactive element are used in nuclear medicine predominantly as a diagnostic application. A relevant advantage of polymeric micelles in aqueous solution is their resulting particle size, which can vary from 10 to 100 nm in diameter. In this review, polymeric micelles labeled with radioisotopes including technetium (99mTc) and indium (111In), and their clinical applications for several diagnostic techniques, such as single photon emissi...

  17. How to Squeeze a Sponge: Casein Micelles under Osmotic Stress, a SAXS Study

    OpenAIRE

    Bouchoux, Antoine; Gésan-Guiziou, Geneviève; Pérez, Javier; Cabane, Bernard

    2010-01-01

    By combining the osmotic stress technique with small-angle x-ray scattering measurements, we followed the structural response of the casein micelle to an overall increase in concentration. When the aqueous phase that separates the micelles is extracted, they behave as polydisperse repelling spheres and their internal structure is not affected. When they are compressed, the micelles lose water and shrink to a smaller volume. Our results indicate that this compression is nonaffine, i.e., some p...

  18. Cryo-transmission electron tomography of native casein micelles from bovine milk

    OpenAIRE

    Trejo, R.; Dokland, T; Jurat-Fuentes, J.; Harte, F.

    2011-01-01

    Caseins are the principal protein components in milk and an important ingredient in the food industry. In liquid milk, caseins are found as micelles of casein proteins and colloidal calcium nanoclusters. Casein micelles were isolated from raw skim milk by size exclusion chromatography and suspended in milk protein-free serum produced by ultrafiltration (molecular weight cut-off of 3 kDa) of raw skim milk. The micelles were imaged by cryo-electron microscopy and subjected to tomographic recons...

  19. Effect of Calcium Concentration on the Structure of Casein Micelles in Thin Films

    OpenAIRE

    Müller-Buschbaum, P.; Gebhardt, R.; Roth, S. V.; Metwalli, E.; Doster, W.

    2007-01-01

    The structure of thin casein films prepared with spin-coating is investigated as a function of the calcium concentration. Grazing incidence small-angle x-ray scattering and atomic force microscopy are used to probe the micelle structure. For comparison, the corresponding casein solutions are investigated with dynamic light-scattering experiments. In the thin films with added calcium three types of casein structures, aggregates, micelles, and mini-micelles, are observed in coexistence with ato...

  20. Triclosan-loaded Tooth-binding Micelles for Prevention and Treatment of Dental Biofilm

    OpenAIRE

    Chen, Fu; Rice, Kelly C.; Liu, Xin-Ming; Reinhardt, Richard A.; Bayles, Kenneth W.; Wang, Dong

    2010-01-01

    The purpose of the present study was to develop tooth-binding micelle formulations and evaluate their ability to both inhibit initial biofilm formation as well as decrease the viability of preformed biofilm using an in vitro dental biofilm model. Alendronate (ALN, a bisphosphonate) was covalently attached to the ends of different Pluronic copolymers to confer tooth-binding ability to the micelles, and triclosan was used as a model drug. Based on different micelle preparation methods, Pluronic...

  1. Simultaneous optimization of variables influencing selectivity and elution strength in micellar liquid chromatography. Effect of organic modifier and micelle concentration.

    Science.gov (United States)

    Strasters, J K; Breyer, E D; Rodgers, A H; Khaledi, M G

    1990-07-01

    Previously, the simultaneous enhancement of separation selectivity with elution strength was reported in micellar liquid chromatography (MLC) using the hybrid eluents of water-organic solvent-micelles. The practical implication of this phenomenon is that better separations can be achieved in shorter analysis times by using the hybrid eluents. Since both micelle concentration and volume fraction of organic modifier influence selectivity and solvent strength, only an investigation of the effects of a simultaneous variation of these parameters will disclose the full separation capability of the method, i.e. the commonly used sequential solvent optimization approach of adjusting the solvent strength first and then improving selectivity in reversed-phase liquid chromatography is inefficient for the case of MLC with the hybrid eluents. This is illustrated in this paper with two examples: the optimization of the selectivity in the separation of a mixture of phenols and the optimization of a resolution-based criterion determined for the separation of a number of amino acids and small peptides. The large number of variables involved in the separation process in MLC necessitates a structured approach in the development of practical applications of this technique. A regular change in retention behavior is observed with the variation of the surfactant concentration and the concentration of organic modifier, which enables a successful prediction of retention times. Consequently interpretive optimization strategies such as the interative regression method are applicable. PMID:2211909

  2. Electron transfer reactions of singlet and triplet pyrene in micelles with various radical anions in aqueous solution

    International Nuclear Information System (INIS)

    The radicals CO-2, CH2O-, CH3CHO-, and CH3COCH-3 were pulse radiolytically produced in aqueous solutions of pH 13 containing 5.5 x 10-5 to 1 x 10-3 M pyrene in cationic micelles. The pyrene reacted in either its singlet ground state or its lowest triplet state, the latter being produced by UV pre-irradiation before formation of the radicals. The electron transfer reactions were monitored by measuring either the optical absorption of the pyrene anion at 495 nm or that of triplet pyrene at 414 nm. The triplet state of pyrene was found to be reduced by these radicals, the rate becoming larger with increasing redox potential of the system aldehyde (or ketone)/radical anion, although the reduction power of these radicals increases in the reverse order. These results are explained in terms of elctron tunneling through the electrical double layer separating the lipoidic part of the micelle where the pyrene molecule resides and the aqueous phase where the hydrophilic radical anions exist. The rate of tunneling is dependent on the relative positions of occupied and unoccupied electronic redox levels of the redox systems involved in the two phases. (orig./HK)

  3. Responses of two birch ( Betula pendula Roth) clones to different ozone profiles with similar AOT40 exposure

    Science.gov (United States)

    Oksanen, Elina; Holopainen, Toini

    Saplings of two clones of European white birch ( Betula pendula Roth) were exposed to three different ozone profiles resulting in same AOT40 value of 13-14 ppm h in a chamber experiment. The sensitive clone 5 and the more tolerant clone 2 were growing (1) under filtered air (=control), or (2) were exposed to 70 ppb ozone for 24 h d -1 (=profile 1), (3) to 100 ppb ozone for 12 h d -1 at 8:00-20:00 (=profile 2), or (4) to 200 ppb ozone for 4.5 h d -1 at 9:30-14:00 (=profile 3) for 20 d. The saplings were determined for growth, visible leaf injuries, stomatal conductance, and concentrations of Rubisco, chlorophyll and carotenoids. Growth responses and induction of visible foliar injuries under different ozone profiles were variable, resulting in 4-17% lower dry mass of shoot, 16-46% reduction in stem height increment and 11-43% increase in visible injuries in clone 5, which was accompanied by higher leaf turnover rate under profile 3 indicating compensation growth. In clone 2, ozone-induced responses ranged from slight stimulation in stem height growth to 13% decrease in dry mass of shoot and 2-16% increase in visible injuries. Daytime stomatal conductance rates were lowered by 14-54% in clone 5 and 9-74% in clone 2, depending on profile. The additional power-weighted analyses revealed that high peak concentrations and exposure shape were important for induction of visible injuries in both clones and reduction in stomatal conductance in clone 5, whereas growth reductions were rather related to total cumulative exposure. The results indicate that profile of ozone exposure, night-time stomatal conductance (24 h flux), and recovery time for defence and compensations reactions should not be ignored in plant response and ozone flux modelling.

  4. Coagulation of nanoparticles in reverse micellar systems: a Monte Carlo model.

    Science.gov (United States)

    Jain, Ravi; Shukla, Diwakar; Mehra, Anurag

    2005-11-22

    The process of formation of nanoparticles obtained by mixing two micellized, aqueous solutions has been simulated using the Monte Carlo technique. The model includes the phenomena of finite nucleation, growth via intermicellar exchange, and coagulation of nanoparticles after their formation. Using the model, an exploratory study has been conducted to analyze whether the coagulation of nanoparticles is the reason for the formation of nanoparticles whose sizes are comparable to the size of the reverse micelles. The model explains the possible mechanism of coagulation of semiconductor nanoparticles formed within reverse micelles and its effect on the evolution of their size with time. The model is predictive in nature, and the simulation results compare well with those observed experimentally. PMID:16285836

  5. Micelle swelling agent derived cavities for increasing hydrophobic organic compound removal efficiency by mesoporous micelle@silica hybrid materials

    KAUST Repository

    Shi, Yifeng

    2012-06-01

    Mesoporous micelle@silica hybrid materials with 2D hexagonal mesostructures were synthesized as reusable sorbents for hydrophobic organic compounds (HOCs) removal by a facile one-step aqueous solution synthesis using 3-(trimethoxysily)propyl-octadecyldimethyl-ammonium chloride (TPODAC) as a structure directing agent. The mesopores were generated by adding micelle swelling agent, 1,3,5-trimethyl benzene, during the synthesis and removing it afterward, which was demonstrated to greatly increase the HOC removal efficiency. In this material, TPODAC surfactant is directly anchored on the pore surface of mesoporous silica via SiOSi covalent bond after the synthesis due to its reactive Si(OCH 3) 3 head group, and thus makes the synthesized materials can be easily regenerated for reuse. The obtained materials show great potential in water treatment as pollutants sorbents. © 2011 Elsevier Inc. All rights reserved.

  6. Solution structure of detergent micelles at conditions relevant to membrane protein crystallization.

    Energy Technology Data Exchange (ETDEWEB)

    Littrell, K.; Thiyagarajan, P.; Tiede, D.; Urban, V.

    1999-07-02

    In this study small angle neutron scattering was used to characterize the formation of micelles in aqueous solutions of the detergents DMG and SPC as a function of detergent concentration and ionic strength of the solvent. The effects on the micelle structure of the additives glycerol and PEG, alone as well as in combination typical for actual membrane protein crystallization, were also explored. This research suggests that the micelles are cigar-like in form at the concentrations studied. The size of the micelles was observed to increase with increasing ionic strength but decrease with the addition of glycerol or PEG.

  7. ADVANCES IN MICROEMULSION PHASE ON SELF-ASSEMBLY AND MICELLE EXTRACTION WITH BLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    Chen Guo; Hao Wen; Huizhou Liu

    2005-01-01

    In this paper we review our work on self-assembly of the system, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, which is a kind of macromolecular complex fluids. The control of self-assembly could be obtained by adding inorganic salts or aliphatic alcohols. By self-assembly of amphiphilic block copolymers, a microemulsion phase is formed, which could be applied in micelle extraction, such as hollow-fiber membrane micelle extraction, magnetic micelle extraction and immobilized micelle extraction.

  8. Small angle neutron scattering study of the micelle structure of amphiphilic block copolymers

    International Nuclear Information System (INIS)

    The amphiphilic block copolymers of vinyl ether were prepared by living cationic polymerization. The partially deuterated copolymers for SANS experiments were especially synthesized by introducing deuterated phenyl units in the hydrophobic chain. SANS measurements were performed for aqueous solutions of these copolymers by changing H2O/D2O ratios. The SANS profiles indicate that the micelles in the present system exhibit a core-shell structure and that the size and shape of micelles are largely dependent on the length of hydrophobic chain. The micelle of shorter hydrophobic chain was found to be nearly spherical, whereas the micelle of longer hydrophobic chain was confirmed to have an ellipsoidal shape

  9. Polyelectrolyte complex micelles by self-assembly of polypeptide-based triblock copolymer for doxorubicin delivery

    Directory of Open Access Journals (Sweden)

    Jeong Hwan Kim

    2014-08-01

    Full Text Available Polyelectrolyte complex micelles were prepared by self-assembly of polypeptide-based triblock copolymer as a new drug carrier for cancer chemotherapy. The triblock copolymer, poly(l-aspartic acid-b-poly(ethylene glycol-b-poly(l-aspartic acid (PLD-b-PEG-b-PLD, spontaneously self-assembled with doxorubicin (DOX via electrostatic interactions to form spherical micelles with a particle size of 60–80 nm (triblock ionomer complexes micelles, TBIC micelles. These micelles exhibited a high loading capacity of 70% (w/w at a drug/polymer ratio of 0.5 at pH 7.0. They showed pH-responsive release patterns, with higher release at acidic pH than at physiological pH. Furthermore, DOX-loaded TBIC micelles exerted less cytotoxicity than free DOX in the A-549 human lung cancer cell line. Confocal microscopy in A-549 cells indicated that DOX-loaded TBIC micelles were transported into lysosomes via endocytosis. These micelles possessed favorable pharmacokinetic characteristics and showed sustained DOX release in rats. Overall, these findings indicate that PLD-b-PEG-b-PLD polypeptide micelles are a promising approach for anti-cancer drug delivery.

  10. Solubilization of docetaxel in poly(ethylene oxide)-block-poly(butylene/styrene oxide) micelles.

    Science.gov (United States)

    Elsabahy, Mahmoud; Perron, Marie-Eve; Bertrand, Nicolas; Yu, Ga-Er; Leroux, Jean-Christophe

    2007-07-01

    Poly(ethylene oxide)-block-poly(styrene oxide) (PEO-b-PSO) and PEO-b-poly(butylene oxide) (PEO-b-PBO) of different chain lengths were synthesized and characterized for their self-assembling properties in water by dynamic/static light scattering, spectrofluorimetry, and transmission electron microscopy. The resulting polymeric micelles were evaluated for their ability to solubilize and protect the anticancer drug docetaxel (DCTX) from degradation. The drug release kinetics as well as the cytotoxicity of the loaded micelles were assessed in vitro. All polymers formed micelles with a highly viscous core at low critical association concentrations (<10 mg/L). Micelle morphology depended on the nature of the hydrophobic block, with PBO- and PSO-based micelles yielding monodisperse spherical and cylindrical nanosized aggregates, respectively. The maximum solubilization capacity for DCTX ranged from 0.7 to 4.2% and was the highest for PSO micelles exhibiting the longest hydrophobic segment. Despite their high affinity for DCTX, PEO-b-PSO micelles were not able to efficiently protect DCTX against hydrolysis under accelerated stability testing conditions. Only PEO-b-PBO bearing 24 BO units afforded significant protection against degradation. In vitro, DCTX was released slower from the latter micelles, but all formulations possessed a similar cytotoxic effect against PC-3 prostate cancer cells. These data suggest that PEO-b-P(SO/BO) micelles could be used as alternatives to conventional surfactants for the solubilization of taxanes. PMID:17579476

  11. Cholesterol-Enhanced Polylactide-Based Stereocomplex Micelle for Effective Delivery of Doxorubicin

    OpenAIRE

    Jixue Wang; Weiguo Xu; Jianxun Ding; Shengfan Lu; Xiaoqing Wang; Chunxi Wang; Xuesi Chen

    2015-01-01

    Nanoscale micelles as an effective drug delivery system have attracted increasing interest in malignancy therapy. The present study reported the construction of the cholesterol-enhanced doxorubicin (DOX)-loaded poly(D-lactide)-based micelle (CDM/DOX), poly(L-lactide)-based micelle (CLM/DOX), and stereocomplex micelle (CSCM/DOX) from the equimolar enantiomeric 4-armed poly(ethylene glycol)–polylactide copolymers in aqueous condition. Compared with CDM/DOX and CLM/DOX, CSCM/DOX showed the small...

  12. Thermo-Responsive and Biocompatible Diblock Copolymers Prepared via Reversible Addition-Fragmentation Chain Transfer (RAFT Radical Polymerization

    Directory of Open Access Journals (Sweden)

    Kenichi Fukuda

    2014-03-01

    Full Text Available Poly(2-(methacryloyloxyethyl phosphorylcholine-b-poly(N,N-diethyl acrylamide (PMPCm-PDEAn was synthesized via reversible addition-fragmentation chain transfer (RAFT controlled radical polymerization. Below, the critical aggregation temperature (CAT the diblock copolymer dissolved in water as a unimer with a hydrodynamic radius (Rh of ca. 5 nm. Above the CAT the diblock copolymers formed polymer micelles composed of a PDEA core and biocompatible PMPC shells, due to hydrophobic self-aggregation of the thermo-responsive PDEA block. A fluorescence probe study showed that small hydrophobic small guest molecules could be incorporated into the core of the polymer micelle above the CAT. The incorporated guest molecules were released from the core into the bulk aqueous phase when the temperature decreased to values below the CAT because of micelle dissociation.

  13. Activity Regulation of Lignin Peroxidase from Phanerochaete chrysosporium in Nonionic Reversed Micellar Medium

    Institute of Scientific and Technical Information of China (English)

    Dan WANG; Xi Rong HUANG; Cai Xia LIU; Yue Zhong LI; Yin Bo QU; Pei Ji GAO

    2005-01-01

    The activity of lignin peroxidase (LiP) in reversed micelles of polyoxyethylene lauryl ether (Brij30) changed with the molar ratio of water to the surfactant and the denaturant concentration of guanidinium chloride. At low water contents the activity of LiP could be enhanced by the denaturant at moderate concentration. This phenomenon, together with the spectral characteristics of the intrinsic fluorescence of LiP, suggested that the conformation of the active center of LiP was flexible.

  14. Doxorubicin-Loaded PEG-PCL-PEG Micelle Using Xenograft Model of Nude Mice: Effect of Multiple Administration of Micelle on the Suppression of Human Breast Cancer

    International Nuclear Information System (INIS)

    The triblock copolymer is composed of two identical hydrophilic segments Monomethoxy poly(ethylene glycol) (mPEG) and one hydrophobic segment poly(ε-caprolactone) (PCL); which is synthesized by coupling of mPEG-PCL-OH and mPEG-COOH in a mild condition using dicyclohexylcarbodiimide and 4-dimethylamino pyridine. The amphiphilic block copolymer can self-assemble into nanoscopic micelles to accommodate doxorubixin (DOX) in the hydrophobic core. The physicochemical properties and in vitro tests, including cytotoxicity of the micelles, have been characterized in our previous study. In this study, DOX was encapsulated into micelles with a drug loading content of 8.5%. Confocal microscopy indicated that DOX was internalized into the cytoplasm via endocystosis. A dose-finding scheme of the polymeric micelle (placebo) showed a safe dose of PEG-PCL-PEG micelles was 71.4 mg/kg in mice. Importantly, the circulation time of DOX-loaded micelles in the plasma significantly increased compared to that of free DOX in rats. A biodistribution study displayed that plasma extravasation of DOX in liver and spleen occurred in the first four hours. Lastly, the tumor growth of human breast cancer cells in nude mice was suppressed by multiple injections (5 mg/kg, three times daily on day 0, 7 and 14) of DOX-loaded micelles as compared to multiple administrations of free DOX

  15. Doxorubicin-Loaded PEG-PCL-PEG Micelle Using Xenograft Model of Nude Mice: Effect of Multiple Administration of Micelle on the Suppression of Human Breast Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Cuong, Nguyen-Van [Department of Biomedical Engineering, Chung Yuan Christian University, 200, Chung Pei Rd., Chung Li, Taiwan (China); Department of Chemical Engineering, Ho Chi Minh City University of Industry, 12 Nguyen Van Bao St, Ho Chi Minh (Viet Nam); Jiang, Jian-Lin; Li, Yu-Lun [Department of Biomedical Engineering, Chung Yuan Christian University, 200, Chung Pei Rd., Chung Li, Taiwan (China); Chen, Jim-Ray [Department of Pathology, Chang Gung Memorial Hospital at Keelung, Taiwan and Chang Gung University, College of Medicine, Taoyuan, Taiwan (China); Jwo, Shyh-Chuan [Division of General Surgery, Chang Gung Memorial Hospital at Keelung, Taiwan and Chang Gung University, College of Medicine, Taoyuan, Taiwan (China); Hsieh, Ming-Fa, E-mail: mfhsieh@cycu.edu.tw [Department of Biomedical Engineering, Chung Yuan Christian University, 200, Chung Pei Rd., Chung Li, Taiwan (China)

    2010-12-28

    The triblock copolymer is composed of two identical hydrophilic segments Monomethoxy poly(ethylene glycol) (mPEG) and one hydrophobic segment poly(ε-caprolactone) (PCL); which is synthesized by coupling of mPEG-PCL-OH and mPEG-COOH in a mild condition using dicyclohexylcarbodiimide and 4-dimethylamino pyridine. The amphiphilic block copolymer can self-assemble into nanoscopic micelles to accommodate doxorubixin (DOX) in the hydrophobic core. The physicochemical properties and in vitro tests, including cytotoxicity of the micelles, have been characterized in our previous study. In this study, DOX was encapsulated into micelles with a drug loading content of 8.5%. Confocal microscopy indicated that DOX was internalized into the cytoplasm via endocystosis. A dose-finding scheme of the polymeric micelle (placebo) showed a safe dose of PEG-PCL-PEG micelles was 71.4 mg/kg in mice. Importantly, the circulation time of DOX-loaded micelles in the plasma significantly increased compared to that of free DOX in rats. A biodistribution study displayed that plasma extravasation of DOX in liver and spleen occurred in the first four hours. Lastly, the tumor growth of human breast cancer cells in nude mice was suppressed by multiple injections (5 mg/kg, three times daily on day 0, 7 and 14) of DOX-loaded micelles as compared to multiple administrations of free DOX.

  16. A Comparison of Seasonal and Interannual Variability of Soil Dust Aerosols Over the Atlantic Ocean as Inferred by the Toms AI and AVHRR AOT Retrievals

    Science.gov (United States)

    Cakmur, R. V.; Miller, R. L.; Tegen, Ina; Hansen, James E. (Technical Monitor)

    2001-01-01

    The seasonal cycle and interannual variability of two estimates of soil (or 'mineral') dust aerosols are compared: Advanced Very High Resolution Radiometer (AVHRR) aerosol optical thickness (AOT) and Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI), Both data sets, comprising more than a decade of global, daily images, are commonly used to evaluate aerosol transport models. The present comparison is based upon monthly averages, constructed from daily images of each data set for the period between 1984 and 1990, a period that excludes contamination from volcanic eruptions. The comparison focuses upon the Northern Hemisphere subtropical Atlantic Ocean, where soil dust aerosols make the largest contribution to the aerosol load, and are assumed to dominate the variability of each data set. While each retrieval is sensitive to a different aerosol radiative property - absorption for the TOMS AI versus reflectance for the AVHRR AOT - the seasonal cycles of dust loading implied by each retrieval are consistent, if seasonal variations in the height of the aerosol layer are taken into account when interpreting the TOMS AI. On interannual time scales, the correlation is low at most locations. It is suggested that the poor interannual correlation is at least partly a consequence of data availability. When the monthly averages are constructed using only days common to both data sets, the correlation is substantially increased: this consistency suggests that both TOMS and AVHRR accurately measure the aerosol load in any given scene. However, the two retrievals have only a few days in common per month so that these restricted monthly averages have a large uncertainty. Calculations suggest that at least 7 to 10 daily images are needed to estimate reliably the average dust load during any particular month, a threshold that is rarely satisfied by the AVHRR AOT due to the presence of clouds in the domain. By rebinning each data set onto a coarser grid, the availability of

  17. Reversible Self-Assembly of Backbone-Thermoresponsive Long Chain Hyperbranched Poly(N-Isopropyl Acrylamide

    Directory of Open Access Journals (Sweden)

    Ting-Ting Liu

    2016-01-01

    Full Text Available In this paper, we mainly described the reversible self-assembly of a backbone-thermoresponsive, long-chain, hyperbranched poly(N-isopropyl acrylamide (LCHBPNIPAM in aqueous solution. Here, we revealed a reversible self-assembly behavior of LCHBPNIPAM aqueous solution derived from temperature. By controlling the temperature of LCHBPNIPAM aqueous solution, we tune the morphology of the LCHBPNIPAM self-assemblies. When the solution temperature increased from the room temperature to the lower critical solution temperature of PNIPAM segments, LCHBPNIPAM self-assembled from multi-compartment vesicles into solid micelles. The morphology of LCHBPNIPAM self-assemblies changed from solid micelles to multi-compartment vesicles again when the temperature decreased back to the room temperature. The size presented, at first, an increase, and then a decrease, tendency in the heating-cooling process. The above thermally-triggered self-assembly behavior of LCHBPNIPAM aqueous solution was investigated by dynamic/static light scattering, transmission electron microscopy, atomic force microscopy, fluorescence spectroscopy, 1H nuclear magnetic resonance in D2O, and attenuated total reflectance Fourier transform infrared spectroscopy. These results indicated that LCHBPNIPAM aqueous solution presents a reversible self-assembly process. The controlled release behaviors of doxorubicin from the vesicles and micelles formed by LCHBPNIPAM further proved the feasibility of these self-assemblies as the stimulus-responsive drug delivery system.

  18. Switchable pH-responsive polymeric membranes prepared via block copolymer micelle assembly

    KAUST Repository

    Nunes, Suzana Pereira

    2011-05-24

    A process is described to manufacture monodisperse asymmetric pH-responsive nanochannels with very high densities (pore density >2 × 10 14 pores per m2), reproducible in m2 scale. Cylindric pores with diameters in the sub-10 nm range and lengths in the 400 nm range were formed by self-assembly of metal-block copolymer complexes and nonsolvent-induced phase separation. The film morphology was tailored by taking into account the stability constants for a series of metal-polymer complexes and confirmed by AFM. The distribution of metal-copolymer micelles was imaged by transmission electron microscopy tomography. The pH response of the polymer nanochannels is the strongest reported with synthetic pores in the nm range (reversible flux increase of more than 2 orders of magnitude when switching the pH from 2 to 8) and could be demonstrated by cryo-field emission scanning electron microscopy, SAXS, and ultra/nanofiltration experiments. © 2011 American Chemical Society.

  19. Peptide-conjugated micelles as a targeting nanocarrier for gene delivery

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Wen Jen, E-mail: wjlin@ntu.edu.tw; Chien, Wei Hsuan [National Taiwan University, School of Pharmacy, Graduate Institute of Pharmaceutical Sciences (China)

    2015-09-15

    The aim of this study was to develop peptide-conjugated micelles possessing epidermal growth factor receptor (EGFR) targeting ability for gene delivery. A sequence-modified dodecylpeptide, GE11(2R), with enhancing EGF receptor binding affinity, was applied in this study as a targeting ligand. The active targeting micelles were composed of poly(d,l-lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) copolymer conjugated with GE11(2R)-peptide. The particle sizes of peptide-free and peptide-conjugated micelles were 277.0 ± 5.1 and 308.7 ± 14.5 nm, respectively. The peptide-conjugated micelles demonstrated the cellular uptake significantly higher than peptide-free micelles in EGFR high-expressed MDA-MB-231 and MDA-MB-468 cells due to GE11(2R)-peptide specificity. Furthermore, the peptide-conjugated micelles were able to encapsulate plasmid DNA and expressed cellular transfection higher than peptide-free micelles in EGFR high-expressed cells. The EGFR-targeting delivery micelles enhanced DNA internalized into cells and achieved higher cellular transfection in EGFR high-expressed cells.

  20. Effect of Spacers on CMCs and Micelle-forming Enthalpies of Gemini Surfactants by Titration Microcalorimetry

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The critical micelle concentrations (CMC) and the micelle-forming enthalpies (D Hmic) of gemini surfactants were first measured by the precise titration microcalorimetry. The results showed that D Hmic values are negative, and there is an exothermal minimum between s=4 and s=6. Furthermore, the CMCs of the surfactants are in good agreement with literature values.