Surfactants In Aqueous Media Research Articles

Low-temperature ordering of FePt nanoparticles by alternate reduction of metal salts in aqueous medium

FePt nanoparticles have been successfully synthesized by the alternate reduction of chloroplatinic acid and ferric chloride, in the presence of acetyl trimethyl ammonium bromide as a surfactant in aqueous medium. Detailed investigations on the structural and magnetic properties of these nanoparticles were presented as a function of annealing temperature. Selected area electron diffraction shows the initiation of phase transition from the as-synthsized phase to ordered face center tetragonal (FCT) at 400°C. The x-ray diffraction and magnetic measurements confirm the transformation to FCT phase at 400°C. The magnetic measurements at room temperature show a double phase hysteresis loop at 400°C and a nearly single phase hysteresis loop at 600°C, with the coercivity of about 3.4kOe and 16.2kOe, respectively. We report for the first time this alternate reduction method in synthesizing FePt nanoparticles, obtained a decrease of about 100°C in the ordering temperature.

Removal of Cd (II) by using polypyrrole and its nanocomposites

Polypyrrole was successfully synthesized by using ferric chloride as an oxidant in the presence of sodium dodecylhydrogensulfonate, poly(vinyl pyrrolidone) and poly(vinyl alcohol) as surfactants in aqueous media. The effect of polypyrrole and its nanocomposites for the removal of Cd (II) was investigated. The products were characterized in terms of, morphology and chemical structure. The FTIR spectra show that the intensity of peaks was related to the type of surfactant. The crystalline nature of nanocomposites was determined from XRD analysis. The extra peaks in the XRD pattern of nanocomposites indicate the presence of Al2O3 nanoparticles in the polypyrrole matrix. The aim of this research was to investigate the sorption characteristic of polypyrrole nanocomposites for the removal of Cd (II) from aqueous solution. The removal percentage of Cd (II) was carried out by using batch method. The optimum conditions of sorption were found to be: contact time of 45min and pH 5. The Langmuir and Freundlich model are subjected to sorption data to estimate the sorption capacity and intensity. The data was better fitted by using Langmuir model.

Mixed micellization of gemini surfactant with nonionic surfactant in aqueous media: a fluorometric study

Herein we report on the study of the interactions between alkanediyl-α,ω-type cationic dimeric (gemini) surfactant and the nonionic Triton X-100 in aqueous medium. The critical micelle concentrations of binary mixtures were determined by fluorometric study. Using the regular solution theory for the analysis of the experimental data, the attractive nature of interactions and synergistic behavior of gemini surfactant and Triton X-100 mixture were demonstrated. The micelle aggregation number was measured using steady state fluorescence quenching method. The micropolarity, binding constant and dielectric constant of mixed systems were determined from the ratio of peak’s intensity (I 1/I 3) in the pyrene fluorescence emission spectrum.

Polymer-Surfactant Interactions and the Effect of Tail Size Variation on Micellization Process of Cationic ATAB Surfactants in Aqueous Medium

The interactions between oppositely charged surfactant-polymer systems have been studied using surface tension and conductivity measurements and the dependence of aggregation phenomenon over the polyelectrolyte concentration and chain length of cationic ATAB surfactants, cetyltrimethyl ammonium bromide (CTAB), tetradecyltrimethyl ammonium bromide (TTAB), and dodecyltrimethyl ammonium bromide (DTAB) have been investigated. It was observed that cationic surfactants induce cooperative binding with anionic polyelectrolyte at critical aggregation concentration (cac). The cac values of ATAB surfactants in the presence of anionic polyelectrolyte, sodium carboxy methyl cellulose (NaCMC), are considerably lower than their critical micelle concentration (cmc). After the complete complexation, free micelles are formed at the apparent critical micelle concentration (acmc), which is slightly higher in polyelectrolyte aqueous solution than in pure water. Among the cationic surfactants (i.e., CTAB, TTAB, and DTAB), DTAB was found to have least interaction with NaCMC. Surfactants with longer tail size strongly favor the interaction, indicating the dependence of aggregation phenomenon on the structure, morphology, and tail length of the surfactant.

A Systematic Study of Mixed Surfactant Solutions of a Cationic Ester‐Bonded Dimeric Surfactant with Cationic, Anionic and Nonionic Monomeric Surfactants in Aqueous Media

AbstractA novel cationic biodegradable dimeric (gemini) surfactant, ethane‐1,2‐diyl bis(N,N‐dimethyl‐N‐hexadecylammoniumacetoxy) dichloride (16‐E2‐16), containing an ester‐linked spacer was synthesized. Its pure and mixed micellization properties with monomeric surfactants cetyl trimethyl ammonium chloride, cetyl pyridinium chloride, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, cetyl alcohol ethoxylate (20EO) and tert‐octylphenol ethoxylate (9.5EO) were investigated by surface tension measurements at 30 °C. The critical micelle concentration (CMC) of 16‐E2‐16 is well below that of cetyl trimethyl ammonium chloride containing the same number of carbon atoms in the hydrophobic tail per polar head. At different mole fractions of the gemini surfactant, the CMCs of the gemini‐conventional binary mixtures were determined and were found to be less than the ideal CMC values in all the cases indicating synergistic interactions. Aggregation number and Stern–Volmer constant, obtained by the fluorescence quenching technique, also support the synergistic behavior of the surfactant systems.

Surfactant-assisted shape control of copper nanostructures

Stable copper nanoparticles and copper nanorods have been successfully prepared in aqueous surfactant medium. The nanomaterials are stable and resistant towards aerial oxidation. The most interesting aspect of this work is that it is possible to tune the shape of the copper nanomaterials by regulating surfactant concentration.

Mixed Micellization of Gemini Surfactant with Nonionic Surfactant in Aqueous Media: A Fluorometric Study

Mixed Micellization of Gemini Surfactant with Nonionic Surfactant in Aqueous Media: A Fluorometric Study

Mixed Micellization Behavior of Gemini (Cationic Ester-Bonded) Surfactants with Conventional (Cationic, Anionic and Nonionic) Surfactants in Aqueous Medium

Abstract Two cationic ester-bonded cleavable gemini surfactants of different hydrophobic chain length ethane-1,2-diyl bis(N,N-dimethyl-N-alkylammoniumacetoxy)dichloride, C n H2n+1(CH3)2N+(CH2COOCH2)2N+(CH3)2C n H2n+1. 2Cl- (n-E2-n, n=12, 16), having ester linkage in the spacer, were synthesized adopting the reported procedure. Physicochemical properties of the single and binary gemini-conventional mixed micelles of different mole fractions were studied by conductivity measurements at 30 ºC. The conventional surfactants used were: DTAC (dodecyltrimethylammonium chloride), CTAC (hexadecyltrimethylammonium chloride), CPC (cetylpyridinium chloride), SDS (sodium dodecyl sulfate), SDBS (sodium dodecylbenzene sulfonate), TX-100 (t-octylphenoxypolyethoxyethanol) and Brij 58 (polyoxyethylene (20) cetyl ether). Whereas the critical micelle concentration (cmc) values for the dicationic geminis (12-E2-12 and 16-E2-16) were found to be very low as compared to the respective monomeric surfactant with the same number of carbon atoms in the hydrophobic chain per hydrophilic head group, those for all the binary systems were found to be less than the ideal cmc values studied at different mole fractions of the geminis. This synergistic interaction between the surfactants has been analyzed in the light of various theoretical models such as Clint, Rubingh, Motomura and Maeda.

Mixed Micellization Behavior of Gemini (Cationic Ester-Bonded) Surfactants with Conventional (Cationic, Anionic and Nonionic) Surfactants in Aqueous Medium

Abstract Two cationic ester-bonded cleavable gemini surfactants of different hydrophobic chain length ethane-1,2-diyl bis(N,N-dimethyl-N-alkylammoniumacetoxy)dichloride, C n H2n+1(CH3)2N+(CH2COOCH2)2N+(CH3)2C n H2n+1. 2Cl- (n-E2-n, n=12, 16), having ester linkage in the spacer, were synthesized adopting the reported procedure. Physicochemical properties of the single and binary gemini-conventional mixed micelles of different mole fractions were studied by conductivity measurements at 30 ºC. The conventional surfactants used were: DTAC (dodecyltrimethylammonium chloride), CTAC (hexadecyltrimethylammonium chloride), CPC (cetylpyridinium chloride), SDS (sodium dodecyl sulfate), SDBS (sodium dodecylbenzene sulfonate), TX-100 (t-octylphenoxypolyethoxyethanol) and Brij 58 (polyoxyethylene (20) cetyl ether). Whereas the critical micelle concentration (cmc) values for the dicationic geminis (12-E2-12 and 16-E2-16) were found to be very low as compared to the respective monomeric surfactant with the same number of carbon atoms in the hydrophobic chain per hydrophilic head group, those for all the binary systems were found to be less than the ideal cmc values studied at different mole fractions of the geminis. This synergistic interaction between the surfactants has been analyzed in the light of various theoretical models such as Clint, Rubingh, Motomura and Maeda.

Role of deoxy group on the high concentration of graphene in surfactant/water media

Graphene nanosheets have been successfully dispersed via surfactant-assisted exfoliation of graphite using sodium cholate (SC) and sodium deoxycholate (SDC) surfactants in aqueous media. The concentration of SC and SDC surfactants and saturated graphite concentration have been well optimized to highly disperse graphene in water. The concentration of dispersed graphene in water has been estimated to be 0.52 and 2.58 mg mL−1 for SC and SDC respectively. The absence of an oxygen molecule at the centre aromatic ring of SDC offers a flat and hydrophobic surface that helps to form uniform bilayer micelles on graphitic surfaces and facilitates efficient exfoliation of graphene in a short duration of sonication. The discrepancy in the electrostatic interaction of SC-G over SDC-G dispersions and its re-aggregation stability were compared by zeta potential measurements. The thermal analysis of surfactant covered graphene powders exhibit weak bonding of surfactants with graphitic surfaces through electrostatic interactions. FESEM and AFM images demonstrate the successful exfoliation of few layer graphene with uniform dispersion. Crystalline quality and the stacking of graphene sheets in SC-G and SDC-G dispersions were analyzed using micro-Raman scattering and photoluminescence spectra.

Micellization and Adsorption Behaviors of New Reactive Polymerizable Surfactants Based on Modified Nonyl Phenol Ethoxylates

AbstractThe synthesis and characterization of a series of polymerizable surfactants based on alkyl phenol ethoxylate backbone and carboxylic or anhydride chain ends were investigated. Surface activities of these polymerizable surfactants were investigated to correlate their structure and their performances. The new bifunctional surfmers were prepared by reacting polyoxyethylene 4‐nonyl‐2‐propylene‐phenol nonionic reactive surfactants with maleic anhydride. The chemical structure of the prepared surfactants was characterized by 13C and 1H NMR analyses. The surface activities of the modified polymerizable surfactants were measured from the adsorption isotherm measurements which were determined from the relationship between the concentrations and surface tension of surfactants in aqueous medium at different temperatures. Critical micelle concentration (CMC) values were determined for water soluble surfactants. It was found that CMC decreases with the incorporation of the anhydride and acid groups in the chemical structure of polyoxyethylene 4‐nonyl −2‐propylene‐phenol nonionic surfactant. surface‐active parameters such as area per molecule at the interface (Amin), surface excess concentration (Γmax) and the effectiveness of surface tension reduction (πCMC) were measured from the adsorption isotherms of the modified surfactants. Some thermodynamic data for the adsorption process were calculated and discussed. The data indicated that the new surfmers are more reactive than the simple polyoxyethylene 4‐nonyl‐2‐propylene‐phenol and more adsorbed at interfaces. We have performed a preliminary experiment to explore the emulsification efficiency of the newly synthesized reactive surfactants in equal volume oil–water emulsions. Different emulsion types and stabilities were obtained.

Synthesis and optical properties of monodispersed Ni2+-doped ZnS nanoparticles

Nickel-doped zinc sulfide nanoparticles were successfully synthesized in air atmosphere through chemical precipitation method using surfactants in aqueous medium. The product was characterized by different techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared spectrometer (FT-IR), UV–visible absorption and photoluminescence (PL). Crystal structure, size and morphology of the ZnS:Ni2+ nanoparticles were investigated by XRD and TEM. In the PL emission, a couple of new peaks were observed instead of a single peak by changing the precursor solution. In addition, an enhanced PL emission was observed using surfactants. Phase changes were also observed at different temperatures.

Mixed Micellization Behavior of Gemini (Cationic Ester-Bonded) Surfactants with Conventional (Cationic, Anionic and Nonionic) Surfactants in Aqueous Medium

Mixed Micellization Behavior of Gemini (Cationic Ester-Bonded) Surfactants with Conventional (Cationic, Anionic and Nonionic) Surfactants in Aqueous Medium

Interactions of nanocrystalline cellulose with an oppositely charged surfactant in aqueous medium

The interaction between negatively charged nanocrystalline cellulose (NCC) and a cationic surfactant, tetradecyl trimethyl ammonium bromide (TTAB) was examined by isothermal titration calorimetry (ITC), conductometric and potentiometric titrations and surface tensiometry. The interaction is controlled by electrostatic and hydrophobic interactions. ITC and surface tension measurements confirmed the formation of electrostatically driven NCC–TTAB complexes in the bulk and at the interface, which was followed by hydrophobically driven polymer-induced micellization of TTAB on NCC rods. The critical micelle concentration (CMC) of TTAB was shifted from 1.1 to 1.3g/L in the presence of 0.655g/L NCC. The settling and phase separation characteristics were quantified by determining the height of NCC flocs as a function of time, which describe the stability of NCC in the presence of TTAB. Zeta potential results revealed a charge reversal from negative to positive values with increasing TTAB concentration, confirming the formation of NCC–TTAB complexes in aqueous solutions. Based on the results, a physical mechanism on the interaction of NCC and TTAB is proposed.

Mixed Micellization and Interfacial Properties of Nonionic Surfactants with the Phenothiazine Drug Promazine Hydrochloride at 30 °C

In the present work, the micellization and adsorption behaviors of mixed systems containing an amphiphilic phenothiazine drug, promazine hydrochloride (PMZ) and nonionic surfactants in aqueous media at different mole fractions of nonionic surfactants (α1) were investigated at 30 °C by surface tension measurements. The critical micelle concentrations of the mixtures fall between the values of the individual components, which indicates nonideal mixing. With Tritons the interactions are repulsive at low mole fractions. At high α1 the mixing becomes almost ideal. On the basis of regular solution theory, the micellar mole fractions of surfactants (\(X_{1}^{m}\)) and interaction parameter (βm) were evaluated, while their interfacial mole fractions (\(X_{1}^{\sigma} \)) and interaction parameters at the interface (βσ) were calculated using Rosen’s model. The results indicate that the surfactant’s contribution is greater than that of the drug both at the interface and in micelles. The short and rigid hydrophobic structure of the drug resists its participation in micelle formation more than in the monolayer, leading to \(X_{1}^{m}<X_{1}^{\sigma}\). Values of the surface excess (Γmax) and minimum area per head group (Amin) indicate attractive interactions. Γmax increases and Amin decreases as the surfactant mole fraction increases.

Aggregation Properties of Amide Bearing Cleavable Gemini Surfactants by Small Angle Neutron Scattering and Conductivity Studies

The micellar aggregation of different amide bearing cleavable gemini surfactants with varying methylene spacer chain length (m = 2, 4, 6, 8, and 12) along with the corresponding monomeric surfactant in aqueous media has been investigated by conductometric and small angle neutron scattering (SANS) studies. The critical micellar concentration (CMC) values of gemini surfactants were found to be very low (CMC = 0.08-0.19 mM) and were 23-55 times lesser than the corresponding monomeric analogue (CMC = 4.4 mM). With increase in the spacer chain length, CMC was found to decrease whereas the degree of ionization was found to increase. SANS data have been analyzed by considering the screened coulombic interactions between the micelles to compute the interparticle structure factor S(Q). The extent of micellar growth and the variation of shapes of the micelles formed by these new surfactants in aqueous solution have been found to depend strongly on the spacer chain length. It was observed that the extent of micellar growth and variation of micellar shapes are more pronounced for surfactants with short spacer chain length (m ≤ 4), whereas the surfactants with a long spacer chain length (m ≥ 6) showed slight variation of these properties in aqueous solution. The effects of the variation of the concentration and temperature on the SANS spectra (and hence on the microstructure) of the gemini surfactant (m = 4) were also examined. With an increase in concentration the aggregation number (N) and size of the micelles (the ratio of semimajor axis (a) to semiminor axis (b = c)) increased whereas opposite phenomena was observed with an increase in temperature.

Interactions between ethyl(hydroxyethyl) cellulose and lysine-based surfactants in aqueous media

In this work, the interaction between ethyl(hydroxyethyl) cellulose (EHEC) and three dimeric lysine-based surfactants of distinct chain length (C6, C8 and C10) have been assessed and the system was evaluated in terms of its temperature-dependent gelling capacity. The viscosity profile depends on the specific surfactant, its concentration and temperature. The observed profiles reflected polymer–polymer associations at elevated temperatures and polymer-surfactant interactions, implying the formation of micellar-type associations. The systems induce gelation at higher temperatures. Longer chain-length surfactants induce gelation at lower concentrations due to their stronger tendency to self-assemble. The thermo-responsive gels showed gel strength generally lower than 20Pa.sn and a fractal dimension of 2.3–2.4, respectively, indicating the formation of soft gels comprising a tight and homogeneous network. The weakest gel was produced in the presence of the C6 surfactant. 2D Small-Angle Light Scattering patterns showed a pronounced effect of temperature in terms of the evolution of large hydrophobic clusters, an event precluded when high concentrations of the longer chain surfactants were used.

Surfactant-Assisted Synthesis and Characterization of Stable Silver Bromide Nanoparticles in Aqueous Media

Colloidal dispersions of silver bromide (AgBr) in aqueous surfactant medium have been prepared using a surfactant-assisted synthesis approach with hexadecyltrimethylammonium bromide (CTAB). The surfactant acts both as source of bromide ion as well as the stabilizing agent. Upon progressive addition of silver nitrate to aqueous CTAB solution, stable AgBr dispersions were obtained. Formation of surfactant cation (CTA(+)) stabilized AgBr was confirmed by way of XRD, FTIR and NMR studies. Thermal behavior of the isolated nanoparticles was investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), where the occurrence of phase transition in the surfactant-stabilized nanoparticles was observed. Kinetics of the particle growth was investigated by dynamic light scattering measurements, which predicted the formation of surfactant bilayered structures associated with the nanoparticles of AgBr. Band gap of the nanoparticles was determined by suitably analyzing the UV-visible spectral data, which concluded that the particles behaved like insulators. Morphology of the particles, studied by TEM measurements, was found to be spherical. Finally, enthalpy of formation of surfactant-stabilized AgBr, determined calorimetrically, was found to be dependent on the concentration of the precursors.

Micellization and Phase Behavior of Binary Mixtures of Anionic and Nonionic Surfactants in Aqueous Media

The micellization and phase behavior of the binary mixed systems comprising the anionic surfactants sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/sodium alkyl phenol ether sulfate (APES) and nonionic polyoxyethylene alkyl ether surfactants (C10E8/C10E10/C13E10) have been investigated by surface tension, fluorescence spectroscopy, and cloud point measurements. Various micellar characteristics, surface active properties, thermodynamic parameters, aggregation numbers, and Stern–Volmer constants have been evaluated for these systems. Lower cmc values, negative interaction and thermodynamic parameters, higher aggregation numbers, and improved surface active properties for the proposed mixed systems indicate the existence of strong synergistic interactions and the formation of thermodynamically stable mixed micelles. Observed elevation in the cloud point (CP) shift suggests the formation of charged micelles that increases the intermicellar repulsions and poses a hindrance to the coacervation of micelles. It sub...

Surfactant-sensitized spectrophotometric determination of Hg(II) in water samples using 2-(2-thiazolylazo)- p-cresol as ligand and cetylpyridinium chloride as cationic surfactant

A new, reliable, surfactant-sensitized method is described for the spectrophotometric determination of total and dissolved inorganic mercury at trace levels. The method is based on the ternary complex formation of Hg(II) with 2-(2-thiazolylazo)-p-cresol and a cationic surfactant, cetylpyridinium chloride, at pH 9.5. The detection and quantification limits of the method with surfactant were 6 and 19 \mu g L^{-1}, while those of the method without surfactant were 22 and 67 \mu g L^{-1}, respectively. The method obeys Beer's law at up to approximately 10 mg L^{-1} Hg(II) in an aqueous surfactant medium. The relative errors and relative standard deviations of the method were 2.2% and 3.2%, while those of the direct method were 11% and 4.4% (1.0 mg L^{-1}, n = 10), respectively. The accuracy and reliability were examined by the recoveries of spiked solutions at 3 and 5 mg L^{-1} for the determination of mercury in tap water, drinking water, dental unit wastewater, and artificially prepared model water samples. It was found that the results were very good and comparable for both the present method and the modified dithizone method, which was used as an independent reference method. Speciation studies for binary mixtures containing Hg(I) plus Hg(II) ions at known concentration ratios were also conducted.