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Owing to its availability, low cost and strong reducibility capacity, chitosan can be widely used for Cr(VI) recovery, in this study the removal of Cr(VI) from aqueous solution was investigated using composite adsorbents derived from chitosan (obtained from shrimp peels) and Cu(OH)2 or CuO (prepared by alkaline precipitation of Cu(II) ions) to manufacture ChiCu(OH)2 and ChiCuO, respectively. The adsorbents were characterized by using SEM, BET surface area and zeta potential measurements. Adsorption uptake was highly dependent on pH, temperature, Cr(VI) concentration and sorbent mass: The optimum pH for Cr(VI) removal being close to 4. The adsorption isotherm can be described by Langmuir adsorption isotherm while the uptake kinetics was highly fitted with the pseudo-second order rate equation. The effect of temperature was also evaluated, verifying the endothermic nature of the adsorption process. Chromium desorption was performed using alkaline saline solution (20 g L−1 NaCl with the pH set to 12 with NaOH). The recycling of the sorbent was tested, maintaining a removal efficiency and a metal recovery over 90% for three successive adsorption/desorption cycles. The results showed that, the fabricated nanocomposites are promising adsorbents for Cr(VI) from aqueous solution.

The micellization phenomena in the mixed system of the amphiphilic antidepressant drug imipramine hydrochloride (IPH) and cationic hydrotropes - aniline hydrochloride (AnH), ortho-toluidine hydrochloride (o-ToH), as well as para-toluidine hydrochloride (p-ToH)- in a water solution at a range of temperatures (288.15, 293.15, 298.15, and 303.15 K) was investigated using the conductometry method. In accordance with the regular solution theory (RST), along with other models, such as Rubingh's model, Rodenas's model, and so forth, various parameters were determined to attain a complete picture of the association behaviours of IPH and the hydrotrope mixtures. For every IPH-hydrotrope mixture, the critical micelle concentration (cmc) of the mixture along with the composition of the hydrotropes in the mixed micelle diverged from what they would have been in an ideal system, demonstrating non-ideal behaviour. The divergence amongst evaluated cmc and ideal cmc (cmcid) values viewing interaction amid studied constituents. The effects of the hydrotropes on the cmc of IPH (drug) were found to occur in the following order: p-ToH > AnH > o-ToH. The interaction parameters (β) were also evaluated to obtain detailed insights into the interactions amongst the studied constituents by applying a theoretical model introduced by Rubingh. The β values were negative, showing the presence of interactions between the binary mixtures of IPH and the hydrotropes. Micellar mole fraction (X1) data estimated via the applied models in present system showed the attractive interactions between the IPH and hydrotropes as well as the intercalation of hydrotrope monomers between the drug IPH monomers constituting the micelle. Through the achieved thermodynamic parameters of the micellization of IPH under different conditions, the effects of temperature and the cationic hydrotropes, along with the impact of their concentrations on their association behaviours, were deduced.

Paracetamol (PC) is one of the most common non-steroidal anti-inflammatories, pain-killer, and antipyretic drugs. Thus, the development of a cheap, access, and accurate analytical technique is necessary for monitoring the purity of the PC in their pharmaceutical formulations. Herein, a layer of polypyrrole (PPy) was used to modify gold nanoflowers/gold electrodes and then applied to determine PC in the presence of 4-aminophenol. The relationship between the PC concentrations (within a range from 100 nmol L − 1 to 25 µmol L − 1) and their corresponding current peaks demonstrated a linear curve with a limit of detection (LOD) as low as 133 nmol L − 1. The synthesized PPy/Au nanoflowers nanocomposite modified Au electrode was successfully used to monitor the purity of the Novadol tablets. Then the electrochemical results were validated by the gas chromatography technique. Hence, the developed electrode displays a significant PC-sensing capability even at trace concentrations, maintaining functionality for reuse without substantial deterioration in its original performance.

The synthesis of cheap and efficient materials for developing fuel cells is challenging for researchers. In this study, nickel sulfide nanoparticles (NiS NPs) and nickel sulfide/molybdenum disulfide (NiS/MoS2) nanocomposite modified ITO electrodes were synthesized based on a simple and facile hydrothermal method. Raman spectroscopy, X-ray diffraction, SEM, FTIR, and energy dispersive X-ray spectroscopy analysis were used to study the morphologies, structures, and phase identification of the electrocatalysts. The electrocatalytic activities of the modified electrodes towards the methanol oxidation reaction were also evaluated based on the cyclic voltammetry technique. The results indicated that NiS/MoS2 exhibited higher electrocatalytic activity towards the methanol electrooxidation in alkaline media that could be attributed to the uses of MoS2 with high surface area, which facilitates the diffusion of methanol molecules. Thus, the NiS/MoS2 is a good candidate for application in the direct methanol fuel cell.

Zirconium (Zr) decorated with manganese dioxide (MnO2) nanoparticles-functionalized reduced graphene oxide (RGO); (Zr-MnO2@RGO) tertiary nanocomposite was fabricated by a facile chemical route. The bi-functionality of the novel nanocomposite by Zr and MnO2 nanoparticles has greatly enhanced the efficiency and kinetics of its adsorptivity towards arsenic As(V). The physicochemical properties of the fabricated nanocomposite were characterized extensively by using XRD, Raman spectroscopy, TGA, HR-TEM, FT-IR, SEM, and EDX techniques. The effects of medium pH, mass dosage, kinetics, initial arsenate concentration were investigated via batch-adsorption experiments. Contact time study revealed that pseudo-second-order equation fitted well the kinetic data indicated a fast and feasible sorption process. The reusability and stability performance of the nanocomposite was evaluated and confirmed after five adsorption-desorption cycles. The efficacy of the potential novel nanocomposite towards the simultaneous removal of As(V) from industrial and groundwater samples has been examined.

Fundamental investigations of the removal of methylene blue (MB) from aqueous solutions by synthesized orthophosphoric acid-doped pyrazole-g-poly glycidyl methacrylate (OPA-Py-g-PGMA) and poly (glycidyl methacrylate) (PGMA) particles of average size 71 and 40 μm, respectively, conducted under batch conditions. The kinetic and equilibrium results obtained for MB sorption with different initial MB concentrations onto synthesized OPA-Py-g-PGMA, and PGMA were analyzed. Kinetic modeling analysis with three different types of kinetic sorption models (pseudo-first-order, pseudo-second-order, simple Elovich, and intraparticle diffusion rate models) was applied to simulate the MB sorption data. The analysis of the kinetic data indicated that the sorption was a second-order process. An ion-exchange mechanism may have existed in the MB-sorption process with the synthesized OPA-Py-g-PGMA. The MB uptake by OPA-Py-g-PGMA and PGMA quantitatively evaluated with equilibrium sorption isotherms. To describe the isot...

International audience; Thiourea-formaldehyde (TF) resin is prepared by polycondensation of its two precursors; the incorporation of pre-formed magnetite particles allows synthesizing a magnetic derivative of TF (MTF). These materials are applied to the sorption of two dyes (titan yellow, TY, and rose bengal, RB). Ultrasonic treatment (UT) is tested as an alternative to mechanical agitation (MA). The two sorbents are characterized by scanning electron microscopy, vibrating-sample magnetometry, BET surface area analysis, thermogravimetric analysis, Fourier-transform infrared and NMR spectroscopy, zetametry. Sorption properties are compared for TF and MTF under both MA and UT; considering pH effect, uptake kinetics (modeled using the pseudo-second order rate equation, and resistance to intraparticle diffusion), sorption isotherms (fitted by the Langmuir and Sips equations), the effect of competitor ions, and the desorption efficiency. Optimum sorption occurs at pH 3 (balance between (a) the electrostatic interactions between protonated groups (sorbent) and anionic forms of the dyes, and (b) the competitor effects of counter anions). UT strongly decreases the contact time required for reaching equilibrium (from 240 min to 30 min). UT increases the sorption capacities: in the range 0.3–0.6 mmol dye g−1 (MA) up to 0.9–1 mmol dye g−1. The magnetic core does not change kinetics, while it increases TF sorption capacities for both TY and RB. Under UT, the maximum sorption capacities are comparable for TF and MTF; however, the affinity of MTF remains higher than TF for the two dyes. Alkaline NaCl solutions completely desorb the dyes; UT decreases both the contact time and the NaCl concentration required for achieving the complete desorption of loaded dyes. The sorbents are recycled with high stability in sorption performance for at least five cycles.

A simple, precise and sensitive method in which, a nano optical sensor binuclear Pt-2-aminobenzimidazole-bipyridine, Pt(abi)(bpy) complex doped in sol gel is used for the early diagnosis of liver cancer. The idea depends on the assessment of the concentration of alpha fetoprotein (AFP) in the serum samples of different liver patients. The nano binuclear Pt(abi)(bpy) has strong emission spectrum upon excitation at 380 nm in distilled water. The assessment of alpha fetoprotein (AFP) depends on the quenching of the emission spectrum of the optical sensor at 610 nm in water by the alpha fetoprotein (AFP). The calibration plot was achieved over the concentration 5.0 – 350 U L−1 with a correlation coefficient of 0.997 and a detection limit of 3.0 U L−1. The method was used satisfactorily for the diagnosis of liver cancer in a number of serum samples collected from various patients and health state; healthy (≤ 30 U L−1), Virus B (42.2–69.5 U L−1), Virus C (75.7–98.4 U L−1), Cirrhosis (112–147 U L−1) and HCC (185.2–349.6 U L−1). Furthermore, the assessment of the alpha-fetoprotein by the proposed method increases its sensitivity (92.88%) and specificity (91.41%) for early diagnosis of HCC.

Novel acid–base ions exchanger for basic dye removal developed through three subsequent steps. First, glycidyl methacrylate (GMA) was polymerized to have poly glycidyl methacrylate particles. Second, pyrazole derivative was grafted onto poly glycidyl methacrylate particles to have pyrazole-g-poly glycidyl methacrylate. Finally, orthophosphoric acid was doped onto the pyrazole-g-poly glycidyl methacrylate matrix. Factors affecting the pyrazole derivative grafting process were studied. Structure verification was conducted using FT-IR and thermogravimetric analyses. A fundamental investigation of the removal of methylene blue (MB) from aqueous solutions by orthophosphoric acid-doped pyrazole-g-poly glycidyl methacrylate (OPA-py-g-PGMA) and PGMA particles was conducted under batch conditions. Operational conditions such as initial MB concentration, contact time and temperature, adsorbent dosage, and finally agitation speed have been investigated and correlated to the MB removal percentage and adsorpti...

The chromatography of four cationic surfactants was performed on silica high performance thin-layer plates with mixed solvent system of methanol and ethylenediaminetetraacetic acid (EDTA). The resolution of a mixture of Benzyltrimethylammonium chloride (BTAC), Dodecyltrimethylammonium chloride (DTAC), Tetrabutylammonium bromide (TBAB), and Methyltrioctylammonium bromide (MTOB) was achieved by using methanol:5% aqueous EDTA (7:3,v/v) as a solvent system. The effect of concentration of EDTA on the mobility of all the four cationic surfactants was examined. The limit of detection of BTAC, DTAC, TBAB, and MTOB estimated was 0.65, 0.15, 0.15, and 0.31 µg/zone, respectively. The developed method was utilized to identify these surfactants in different spiked water samples after their preliminary separation.

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

The thermodynamics of clouding in an anionic surfactant, sodium dodecyl sulfate (SDS) and quaternary phosphonium bromides systems in the presence of glycerol are reported. The standard Gibbs energy change of solubilization (ΔsG°) for all of the additives was found to be negative. The standard enthalpy change (ΔsH°) and the standard entropy change (TΔsS°) values were found to be negative as well as positive depending upon the type and nature of the additive. The results were explained on the basis of their nature, effect on the water structure, and solubilization of these additives either in the micellar or aqueous phase.

We report a simple chemical reduction method for the synthesis of different colored silver nanoparticles, AgNP, using tyrosine as a reducing agent. Effects of cetyltrimethylammonium bromide, CTAB, and tyrosine concentrations are analyzed by UV–visible measurements and scanning electron microscopy (SEM) to evaluate the mode of AgNP aggregation. The position and shape of the surface resonance plasmon absorption bands strongly depend on the reaction conditions, i.e., [CTAB], [tyrosine], and reaction time. Sub-, post-, and dilution-micellar effects are accountable for the fast and slow nucleation and growth processes. Spectrophotometric measurement also shows that the average size and the polydispersity of AgNP increase with [CTAB] in the solution. CTAB acted as a shape-directing agent.

The energetics of clouding in anionic surfactant (SDBS) and tetrabutylammonium bromide system in the presence of additives, such as ureas, amino acids and sugars is reported. The change of standard Gibbs energy of solubilization (ΔG o ) for all of the additives was found to be negative. The values of change of standard enthalpy (ΔH o ) and that of standard entropy (TΔS o ) values were found to depend on the type and chemistry of the additive. The results were explained on the basis including chemistry of additives, their effect on water structure, and solubilization of additives either in the micellar or in aqueous phases.

We report the effects of polar-protic and polar-aprotic solvents on absorption spectra and particle size of surfactant stabilized silver nanoparticles. Cysteine and cetylteimethylammonium bromide, CTAB were used as the reducing and stabilizing agents, respectively. The prepared orange color silver sols possess an unusually narrow Plasmon absorption shoulder at 450 nm. The absorbance and shape of this shoulder are affected by protic (methanol, ethanol) and aprotic (acetonitrile, DMF, DMSO and 1,4-dioxane) solvents. The observed results are interpreted in terms of the dielectric constant, boiling point, hydrogen bonding, solubilization and donation of electron density from the silver particles to the solvents. Absorbance increases with increasing the dielectric constants of reaction mixture. The particle size decreases with decreasing the hydrophobic character of protic solvents: particle size = 70, 58 and 39 nm in presence and absence of solvents (ethanol and methanol), respectively.

Mixing behavior of anionic surfactant sodium dodecyl sulfate (SDS) with cationic hydrotropes aniline hydrochloride (AH), o-toluidine hydrochloride (o-TH), and p-toluidine hydrochloride (p-TH) have been studied using conductivity at different temperatures. Critical micelle concentration for different mixing mole fractions, their ideal values, and different interaction parameters have been estimated. All the parameters show nonideal behavior with synergistic interactions. Thermodynamic parameters are also calculated for these systems.

Effects of three organic solvents, viz. methyl cellosolve, acetonitrile, and formamide, on the micellization process of Gemini surfactant pentamethylene-1,5-bis(tetradecyldimethylammonium bromide) aqueous solutions, with the volume percentages of the organic solvents up to 50%, have been investigated conductometrically. The studies were made at different temperatures and the data were used to find out different micellization parameters. From the study, it was observed that, although an increment in the amount of the organic solvents delays the micellization, the increase in the critical micelle concentration (cmc) is comparatively less below 20%(v/v) showing the predominance of water character in the bulk phase at lower compositions of the organic solvents. Applying equilibrium model for micelle formation, various thermodynamic parameters were also calculated from the temperature dependence of the cmc values and the results show that the micellization process becomes less spontaneous as the volume % of th...

The thermodynamic parameters of an aqueous anionic surfactant, tetrabutylammonium dodecyl sulfate (TBADS), are calculated in the presence of various additives (viz., quaternary bromides, alcohols, and amines) at the cloud point (CP) of the TBADS−additive system. As the clouding components release their solvated water, they separate out from the solution. Therefore, the CP of an amphiphile can be considered the limit of its solubility. The standard Gibbs energy change of solubilization (ΔsG°) for all of the additives is found to be negative. The standard enthalpy change (ΔsH°) and the standard entropy change (TΔsS°) values are found to be negative as well as positive depending upon the type and nature of the additive. The results are explained on the basis of their nature, effect on the water structure, and solubilization of these additives either in the micellar or aqueous phase.

In this article, we report the results of the mixing behavior of alkanediyl-α,ω-bis(dimethylcetylammonium bromide) gemini surfactants with anionic hydrotropes (sodium salicyalte, sodium benzoate, and sodium tosylate) in aqueous solutions using conductivity measurements. The critical micelle concentration (cmc) for different mixing mole fractions at different temperatures, their ideal cmc values, and different interaction parameters have been estimated. The results show that the mixing behavior is nonideal and the interactions among the surfactants and the hydrotropes are synergistic in nature.

In this paper clouding phenomenon in aqueous solutions of an amphiphilic drug amitriptyline hydrochloride is reported. The effect of adding ethylamine, butylamine, hexylamine, heptylamine, octylamine, ethylenediamine, diethylenetriamine, tetraethylenepentramine, aniline, and benzylamine on the cloud point of solutions containing a fixed drug concentration (50 mM) was seen. All the amines decrease the cloud point by intercalating between the head groups with protonated amine groups at the micellar surface. The amino acids used (lysine, arginine, histidine) also behave similarly. The results are discussed in the light of a particular additive’s ability to remove water from the head group region of the drug micelles.

Herein, we report the results of a study of surface and micellar properties of alkanediyl-α,ω-bis(dimethylcetylammonium bromide) gemini surfactants in pure aqueous solutions and also in the presence of alcohols (butanol, hexanol) and amines (butylamine, hexylamine). Parameters studied include cmc (critical micelle concentration), C20 (concentration required to reduce the surface tension of the solvent by 20 mN·m−1), Γmax (maximum surface excess concentration at the air/solution interface), and Amin (minimum area per surfactant molecule). These parameters indicate mixed micellization between the surfactants and alcohols/amines; therefore, surfactant−additive interactions in mixed micelles and mixed monolayers, as well as activity coefficients, are also calculated. All the results show that high additive concentrations destabilize micelles: ΔGex (excess free energy of micellization) becomes more negative at low additive concentrations (i.e., micelles stabilize) and less negative at high concentrations (i.e....

The micellar morphology in aqueous 0.2 M sodium dodecyl sulfate (SDS) solutions has been studied in the simultaneous presence of organic salts (anilinium hydrochloride, AHC; ortho-toluidine hydrochloride, oTHC; para-toluidine hydrochloride, pTHC) and aliphatic alcohols (n-butanol, C4OH; n-pentanol, C5OH; n-hexanol, C6OH; n-heptanol, C7OH), aliphatic amines (n-butylamine, C4NH2; n-pentylamine, C5NH2; n-hexylamine, C6NH2; n-heptylamine, C7NH2), or hydrocarbons (n-hexane, C6H; n-heptane, C7H) by viscosity measurements under Newtonian flow conditions at 30 °C. Addition of alcohols and amines causes micellar growth which is found to be dependent upon chain length of the additive and nature of organic salt counterion. It is observed that amines are more effective in increasing the viscosity of the system if added in pure 0.2 M SDS solution, while SDS + pTHC system was found versatile when alcohols were added to this system. The increased viscosity or the micellar growth is explained in terms of the site of solubilization of the respective additive and the interaction of the additive with micellar surface and salt counterion present in the head group region. Hydrocarbons are nearly ineffective in inducing micellar growth and can be used as ‘micellar destroyer’ for the grown micelles. The additives used are found effective in tuning the environment of the micelle which is reflected in viscosity behavior. This work may find use in micellar ultrafiltration as well as in mimicking the natural cell, which has several aspects common with the micelle.

In this paper, we are reporting the influence of addition of aromatic acids (anthranilic and benzoic acid) and their sodium salts on the micellar morphological changes in three cationic gemini surfactant solutions, viz. 5 mM tetramethylene-1,4-bis(N-hexadecyl-N,N-dimethylammonium bromide), 10 mM pentamethylene-1,5-bis(N-hexadecyl-N,N-dimethylammonium bromide), and 10 mM hexamethylene-1,6-bis(N,-hexadecyl-N,N-dimethylammonium bromide). The solubilization site of the counterions (obtained from the additives) near the micellar surface are inferred by 1H NMR. The behavior is explained in the light of binding of counterions to the micelle as well as the nature of the functional group attached to the additive.

Here we report observance of clouding phenomenon in aqueous anionic surfactant tetra- n -butylammonium dodecyl sulphate (TBADS) in presence of different inorganic and organic compounds. Inorganic salts increase the CP followed by a decrease with the continuous addition of salt. The addition of aliphatic organic compounds causes both increase and decrease in CP depending upon their solubility (in water) and hydrophilic ranking. The additives of urea family also influence CP both ways depending on whether they are containing >C O or >C S moiety. The former mainly affects water structure while the latter can interact directly with the micelle. In doing so, thio compounds may compete with tetra- n -butylammonium counterion (TBA + ) for the space near the micellar surface. All sugars decrease the CP, which is in cognizance to their effect on the critical micellar concentration of surfactants. Influence of amino acids on the CP is dictated by their acidic/basic nature. The over all effect of the additives is found to depend upon their ability to modify micellar morphology and/or structure of water.

The effect of addition of sodium anthranilate to 5 mM micellar solutions of gemini surfactant 1,4-bis(N-hexadecyl-N,N-dimethylammonium)butane dibromide is investigated by 1H NMR. The solubilization site of anthranilate anion near the micellar surface is inferred. In the micelles, the An− ions intercalate among the surfactant headgroups producing morphological changes.

Analysis of a variety of surfactant aggregation processes (monomer-to-micelle, spherical micelle-to-rod shaped micelle – s → r – transition, micellar growth and clouding phenomenon) in aqueous ureas or thioureas presented here shows a different picture that differs from the earlier literature reports (i.e., urea postpones the surfactant aggregation). Evidence has been collected on the basis of critical micelle concentration (cmc, obtained from conductometry), [1-pentanol] needed for s → r transition (obtained from viscometry), aggregation number (obtained from small angle neutron scattering) and cloud point (CP) measurements. All of these effects are attributed to urea-assisted aggregation up to certain concentration, which depends upon the nature and presence of number of methylene groups in a particular urea. The results are explained on the basis of influence of the additive on solvent water, adsorption on headgroup and hydrocarbon tail and size of the additive. The results may find application in understanding the mechanism of protein denaturation/renaturation by the presence of different additives.

Clouding is rarely observed with ionic surfactants. Herein we report the occurrence of clouding in sodium dodecyl sulfate (SDS, an anionic surfactant) solutions on addition of different symmetrical and unsymmetrical quaternary phosphonium bromides (tetra-n-butylphosphonium, tetraphenylphosphonium, and n-propyltriphenylphosphonium). Cloud point (CP) measurements were made with solutions having different SDS/salt combinations. The nature of the counterion had a crucial role in the occurrence of the phenomenon, whereas substitution of an alkyl chain by a phenyl ring made the salt more effective near ambient temperature. A linear relationship between the SDS and salt concentrations was obtained. It is proposed that both the electrostatic charge and the hydration state of the headgroup region are influenced by counterion addition and that the net charge or volume of the counterion has a key role to play in the overall phenomenon. The effect of the addition of some hydroxy compounds on CP variations in these SDS+salt systems was also studied, and the data were interpreted on the basis of incorporation of these compounds in the micellar headgroup region. The nature of the counterions influenced this incorporation.

Viscosity measurements under Newtonian flow conditions had been performed on cetyltrimethylammonium bromide (CTAB) aqueous solutions in the combined presence of sodium salts of aromatic acids (sodium salicylate, NaSal; sodium benzoate, NaBen; sodium anthranilate, NaAn) and organic additives (1-hexanol, C6OH; n-hexylamine, C6NH2) at 30°C. On addition of C6OH or C6NH2, the viscosity of 25 mM CTAB solution remained nearly constant without salt as well as with a lower salt concentration. This is due to low CTAB concentration which is not sufficient to produce structural changes in this concentration range of salts. However, as the salt concentration was increased further, the effect of C6OH/C6NH2 addition was different with different salts: The viscosity first increased; then a decrease was observed with the former while with C6NH2 a decrease followed by constancy appeared in plots of relative viscosities (η r ) vs. organic additive concentrations. At further higher salt concentration, the magnitude of η r was much higher. The viscosity increase is explained in terms of micellar growth and the decrease in terms of swollen micelle formation (due to interior solubilization of organic additive) or micellar disintegration (due to formation of water + additive pseudophase).

Here we report the clouding phenomenon with sodium dodecyl sulfate (SDS) in combination with tetra-n-butylammonium bromide (Bu4NBr). Cloud point (CP) vs [Bu4NBr] curves are constructed for various fixed [SDS], and the minimum Bu4NBr concentrations required to produce CP are determined. A relationship between [SDS] and [Bu4NBr] is established that exists down to fairly low [SDS]. The presence of aromatic hydrocarbons (added up to their solubility limits) decreases the CP of a fixed SDS−Bu4NBr system. Furthermore, an increase in hydrophobicity of the aromatic hydrocarbon decreases the CP. An unusual CP-decreasing effect of thio compounds is observed, which is discussed in terms of direct interaction of these compounds with anionic SDS micelles.

In this paper, we describe a simple method for the synthesis of MnO(2) nanostructures (quantum dots) by permanganate oxidations of methionine and cysteine. Upon addition of permanganate to a solution of reductant (methionine and/or cysteine), yellow-brown color species appears within the time of mixing which was stable for several weeks. The UV-vis spectroscopy and transmission electron microscopy (TEM) techniques were used to characterize the nature of color formed. TEM images show that the MnO(2) sol consists of aggregated spherical nonoparticles (size in the range caor=7 nm) of various forms. In addition, we observed the different morphologies of the MnO(2) nanostructures (MnO(2) nanoparticles, nanosheet, and fiber-like aggregated nanostructures) under different experimental conditions. The effect of various parameters, such as [H(+)], [MnO(4)(-)], and [reductants] was also investigated.

Clouding phenomenon in aqueous micellar solutions of an anionic surfactant tetra-n-butylammonium dodecylsulfate (TBADS) has been observed as a function of surfactant concentration. Small-angle neutron scattering (SANS) experiments in these systems show clustering of micelles as the temperature approaches the cloud point (CP). The individual micelles and the clusters of micelles coexist at CP. The clustering of micelles depends on the surfactant concentration and temperature. It is proposed that clustering is due to depletion of H-bonded water present around the butyl chains at the micellar surface. This is associated with entropy gain which is considered to be the major thermodynamic factor related to micellar aggregation. The structures (clusters) that emerge depend on the relative lengths of the alkyl chains of the counterion and can be tuned by the temperature.