Solutions Of Cetyltrimethylammonium Bromide Research Articles

Volumetric, viscometric and 1H NMR spectroscopic studies in (polyhydroxy solute + CTAB + H2O) ternary solutions

To investigate the molecular interactions of polyhydroxy solutes with cetyltrimethylammonium bromide (CTAB) surfactant, we have measured the densities and viscosities of (+)-d-xylose, xylitol, (−)-l-sorbose, d-sorbitol, (+)-d-glucose, and (+)-d-maltose in (4.0, 8.0, and 12.0)·10−4mol·kg−1 CTAB(aq) solutions at (298.15, 308.15 and 318.15) K. The density data have been utilized to evaluate apparent molar volumes (V2,ϕ), partial molar volumes (V2°) and their transfer (ΔtV2°) values at infinite-dilution. The viscosity data were analyzed using the Jones-Dole equation and further used to calculate the viscosity B-coefficients and transfer B-coefficients, ΔtB. The structure-making/-breaking behavior of the polyhydroxy solutes were analyzed using the signs and magnitude of (∂2V2°/∂T2)P and dB/dT coefficients. It has been observed that the positive ΔtV2° and ΔtB values increase with increasing CTAB concentration. 1H NMR spectroscopic study of polyhydroxy solutes was also carried out in mB=(4.0, 8.0, and 12.0)·10−4mol·kg−1 CTAB solutions which were made in 9:1 (w/w) H2O+D2O solvent. NMR results showed higher downfield shift in ternary (polyhydroxy solute+CTAB+9:1 (w/w) H2O+D2O) solutions as compared to pure CTAB solution, hence suggested the predominance of hydrophilic-ionic interactions over hydrophobic-ionic interactions.

Surface activities and aggregation behaviors of cationic - anionic fluorocarbon - hydrocarbon surfactants in dilute solutions

In mixtures of sodium perfluoropolyether carboxylate (PFPE-Na) and cetyltrimethylammonium bromide (CTAB) in dilute solutions, the surface activities and aggregation behaviors have been investigated by the surface tension, dynamic surface tension, contact angle methodologies, dynamic light scattering (DLS), transmission electron microscopy (TEM) and dye encapsulation experiments. The surface tension measurements provided the critical micelle concentration (CMC) and the surface tension at the CMC (γCMC) at different molar ratios. In addition, surface activity parameters of the maximum surface excess concentration (Γmax) and the minimum surface area/molecule (Amin) at the air/water interface were evaluated. The adsorption and wetting abilities of FC-poor mixed systems were studied. Mixed systems of fluorocarbon - hydrocarbon surfactants show better ability to reduce the surface tension and more efficiency to reduce the surface tension. Adding tiny amount of PFPE-Na to CTAB solution (1:20–1:50) has little effect to adsorption, but it enhances the surface activity and wetting ability of mixed system distinctly. Meanwhile, the mixed system can form stable vesicle spontaneously near the PFPE-Na/CTAB ratio of 2:1 in aqueous solution, it may be used as drug delivery vehicles and cold be used as micro/nanotemplates for material synthesis [1–4].

Preparation, characterization and antibacterial effects of eco-friendly gold nanorods

Purpose : To synthesize and characterize eco-friendly gold nanorods (Au-NRs) and to assess their effects against two bacterial strains. Methods : Synthesis of eco-friendly gold nanorods was done from an aqueous solution of chloroauric acid and cetyltrimethylammonium bromide by mixing Olea europaea fruit and Acacia nilotica husk extracts with the latter as a reducing agent. The synthesis was monitored by ultraviolet–visible (UV) spectrophotmetry and a zetasizer, while the morphology of the resulting nanorods was assessed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) coupled with an energy-dispersive spectrophotometer (EDS). The effect of the prepared eco-nanorods on growth of Escherichia coli and Staphylococcus aureus bacteria were investigated by agar diffusion method. Results : The synthesized Au-NRs were mostly rod-shaped, with mean size of 96 nm. They exhibited a potent antibacterial activity against Gram-positive and Gram-negative microorganisms ( Escherichia coli and Staphylococcus aureus ). Conclusion : The findings suggest that the nanoformulation of the biomaterial mix of Olea europaea fruit and Acacia nilotica husk extracts is a cost-effective, eco-friendly, and non-toxic synthesis of Au- NRs which has therpeautic potential. Keywords : Olea europaea, Acacia nilotica, Gold nanorods , Eco-friendly synthesis, Gram-positive and Gram-negative microorganisms

Constructing Post-Permeation Method to Fabricate Polymer/Nanocrystals Hybrid Solar Cells with PCE Exceeding 6.

A post-permeation method is constructed for fabricating bulk-heterojunction hybrid solar cells. Porous CdTe film is prepared by annealing the mixture solution of aqueous CdTe nanocrystals and cetyltrimethyl ammonium bromide, after which the post-permeation of polymer is employed. By this method, kinds of polymers can be applied regardless of the intermiscibility with the nanoparticles. The inorganic nanocrystals and the polymer can be treated under respective optimized annealing temperatures, which can facilitate the growth of nanocrystals without damaging the polymers. A high power conversion efficiency of 6.36% in the polymer/nanocrystals hybrid solar cells is obtained via systematical optimization.

Smart worm-like micelles responsive to CO2/N2 and light dual stimuli.

CO2/N2 and light dual stimuli-responsive worm-like micelles (WLMs) were obtained by addition of a relatively small amount of a switchable surfactant, 4-butyl-4'-(4-N,N-dimethylhexyloxy-amine) azobenzene bicarbonate (AZO-B6-CO2), sensitive to the same triggers to a binary aqueous solution of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal).

Ultrasound-assisted synthesis of nanostructured transition metal oxides

Ultrasound pretreatment of aqueous solutions of cetyltrimethylammonium bromide as a structure- directing agent has been applied to prepare nanostructured mesoporous Mn, Fe, and Ni oxides. After removal of the template by triple extraction with a water–ethanol solution of sodium acetate or ammonium chloride, air-calcined samples of oxide materials prepared in such a way possess surface areas of about 300–450 m2/g and are thermally stable up to 300°C.

Reporter-Embedded SERS Tags from Gold Nanorod Seeds: Selective Immobilization of Reporter Molecules at the Tip of Nanorods.

Reporter-embedded (RE) tags are a new generation of sensitive, stable surface enhanced Raman scattering (SERS) tags with Raman reporters embedded between gold nanoparticle (NP) cores and gold (or silver) shells. Most of the reported RE tags have been designed using Au nanospheres as a seed material. Herein, we investigated the synthesis and SERS properties of AuNR/reporter/Ag tags by using gold nanorod (AuNR) seeds with anisotropic physical and optical features. Several highlighted points were discovered, including the following: (1) The cetyltrimethylammonium bromide (CTAB) layer induced the coexistence of chemically and physically adsorbed Raman reporters on AuNR. Conventional washing of the AuNR-reporter complex with water results in the formation of an "internal-external" mixed tag. To obtain a "pure" RE structure, an additional extraction step involving a CTAB solution was essential. (2) The anisotropic distribution of CTAB on AuNR resulted in the preference of the Raman reporters to adsorb to the hotspot at the AuNR tip, which made it a perfect match for improving the SERS signal of the tag. (3) An anisotropic silver coating occurred with the shell thickness on the AuNR side growing much faster than the shell thickness at the tip. This feature ensured that the tag grew to a suitable size with enough silver for SERS enhancement without shadowing the effective Raman reporters at the tip too much. (4) RE tags showed better in vitro and in vivo signal stabilities compared with their external labeling counterparts. Moreover, a novel pH-sensitive SERS peak test was proposed by using 4-mercaptobenzoic acid as the Raman reporter to verify thin coverage by a silver layer. We believe this tag can be broadly applied for molecular detection and bioimaging, and the proposed preparation and structure verification methods can provide universal guidance in the design of novel RE tags.

Dynamic surface properties of DNA/surfactant solutions: Impact of DNA structure

The dynamic surface properties of mixed solutions of a cationic surfactant - cetyltrimethylammonium bromide (CTAB) - and different types of deoxyribonucleic acid in both linear (ctDNA) and plasmid (pDNA) forms were studied by surface tensiometry and dilational surface rheology. The dynamic surface elasticity and the dynamic surface tension depended strongly on the DNA type. The adsorption layers of ctDNA/CTAB solutions exhibited strong elastic behavior in a wide range of surfactant concentrations. Contrariwise, the addition of plasmid DNA altered the dynamic surface elasticity of CTAB solutions only slightly. The significant difference in the size of macromolecules, their conformation, and, thereby, their effective charge leads to the formation of DNA/CTAB complexes of different surface activity and causes drastic changes in the rheology of the adsorption layer.

Electroreduction of Nitrobenzene: Nominal Simulation of Voltammogram

For the electrochemical reduction of nitrobenzene in aqueous cationic micellar solution of cetyltrimethylammonium bromide [CTAB] at platinum electrode using cyclic voltammetry, a reversible/quasi reversible charge transfer reaction pertaining to one electron couple of ArNO2/ArNO2.- was indicated (1). Digital simulation was used to evaluate electrochemical kinetic parameters for the mono-electron transfer step (1). An ECE mechanism, Scheme-1 and Figures 1 and 2 and Table-1, is suggested for the previously reported voltammograms (2) featuring nitrobenzene reduction on a coated platinum electrode partially covered by a thin film of dioctadecyldimethylammonium chloride [DODAC]. Table-1: Diffusion coefficients for nitrobenzene (2) Diffusion coefficient (cm2/s) 6.11×10-5 1.09×10-4 Bare Pt DODAC covered Pt, this work References (1) Tariq, M.; Haque, I. U., Science International (Lahore), 2016, 28, 361 (2) Haque, I. U.; Tariq, M., Journal of the Chemical Society of Pakistan, 2011, 33, 529 Figure 1

The influence of cetyltrimethylammonium bromide on the volumetric properties of ethylene glycol and triethylene glycol at 298.15 k

Density measurements of binary mixtures of ethylene glycol and triethylene glycol as well as solutions of cetyltrimethylammonium bromide (CTAB) in the binary mixtures at various temperatures and concentrations of CTAB have been carried out. The density data have been used to calculate the excess molar volumes V E of the binary mixtures with and without CTAB. The V E values are negative at all compositions of ethylene glycol except at 0.9. The magnitude of the negative V E values was observed to decrease with increasing temperature and concentration of CTAB.These results have been discussed in terms of chemical and physical factors as well as structural changes in the mixed solvents.

Generation of a Chiral Giant Micelle.

Over the past few years, chiral supramolecular assemblies have been successfully used for recognition, sensing and enantioselective transformations. Several approaches are available to control chirality of discrete assemblies (e.g., cages and capsules), but few are efficient in assuring chirality for micellar aggregates. Optically active amino acid-derived surfactants are commonly used to generate chiral spherical micelles. To circumvent this limitation, we benefited from the uniaxial growth of spherical micelles into long cylindrical micelles usually called wormlike or giant micelles, upon the addition of cosolutes. This paper describes the unprecedented formation of chiral giant micelles in aqueous solutions of cetyltrimethylammonium bromide (CTAB) upon increasing addition of enantiopure sodium salt of 1,1'-bi-2-naphthol (Na-binaphtholate) as a cosolute. Depending on the concentrations of CTAB and Na-binaphtholate, chiral gel-like systems are obtained. The transition from spherical to giant micellar structures was probed using rheology, cryo-transmission electron microscopy, polarimetry, and electronic circular dichroism (CD). CD can be effectively used to monitor the incorporation of Na-binaphtholate into the micelle palisade as well as to determine its transition to giant micellar structures. Our approach expands the scope for chirality induction in micellar aggregates bringing the possibility to generate "smart" chiral systems and an alternative asymmetric chiral environment to perform enantioselective transformations.

Antibacterial superabsorbing hydrogels with high saline-swelling properties without gel blockage: Toward ideal superabsorbents for hygienic applications

Superabsorbent polymer hydrogels with antibacterial activity were prepared by an ion exchange reaction as a feasible approach to induce high saline absorption without gel blockage. Hydroethanolic solutions of cetyltrimethylammonium bromide were used to modify surface particles of cross-linked sodium acrylate- co-acrylic acid copolymers which already synthesized under defined conditions. Fourier transform infrared spectroscopy was employed to study the structural characteristic of the finished products. The influence of cetyltrimethylammonium bromide on free (in water) and loaded (in saline) swelling capacity as well as antibacterial activity of superabsorbent polymer hydrogels against Staphylococcus aureus was investigated. Modified samples displayed an improved free and loaded swelling in water and saline, as well as no gel-blocking. These improvements were found to be affected by the reaction time, cetyltrimethylammonium bromide concentration, and water percentage in the solvent mixture. The results from energy dispersive X-ray analysis showed that cetyltrimethylammonium bromide was distributed uniformly in the superabsorbent polymer hydrogel particle surface. Moreover, the modified superabsorbent polymer hydrogels showed high antibacterial activity against S. aureus. Both bacteriostatic and bactericide effects were observed depending on the reaction conditions. Overall, several improvements were concurrently achieved via a single cost-effective post-treatment on the superabsorbent polymer hydrogel particles. Therefore, the results can effectively be used in designing larger scale production of antibacterial superabsorbent polymer hydrogels with desirable swelling properties in hygiene applications.

Critical Behavior and Ensuing Phase Separations in Paraben‐Solubilized Micellar Solutions of Ionic Surfactants

AbstractAqueous solutions of cetyltrimethylammonium bromide (CTAB) show micellar growth in the presence of various organic and inorganic additives. The simultaneous presence of some of these additives exhibit synergistic effects on micellar growth in this system due to their diverse nature of influences on the critical packing parameter of CTAB micelles. In this manuscript, we report dynamic light scattering, small‐angle neutron scattering and rheological studies on influences of the widely used preservative butyl paraben and NaCl on the growth and interaction of CTAB micelles. These additives show synergism in micellar growth and induce micellar attraction‐driven phase separations of both upper consolute temperature and lower consolute temperature regimes in aqueous solutions of CTAB. Quite interestingly, such micellar attraction‐driven phase separations are also induced in aqueous systems of other cationic and anionic surfactants in the simultaneous presence of a hydrophobic substance and NaCl. These systematic observations of micellar attraction‐driven phase separation are the first of this kind in aqueous systems of ionic surfactants. The results also suggest that the use of parabens as preservatives in some ionic surfactantbased formulations can also help in tuning their rheological characteristics.

The physicochemical properties of CTAB solutions in the presence of α-tocopherol

The electrolytic conductivity, electrophoretic mobility and zeta potential (LDV - laser Doppler velocimetry method) as well as the particles size distribution (DLS - dynamic light scattering method) were determined in the cetyltrimethylammonium bromide (CTAB) solutions (0.25–25.00mM) at different concentrations of α-tocopherol (0–11.6mM). The measurements were made at 25°C and 30°C. It was found that α-tocopherol (vitamin E) modifies the physicochemical properties of CTAB micellar solutions – the potential carrier of bioactive substances. The electrolytic conductivity of CTAB solutions was lowered by the addition of α-tocopherol. Particularly, the effect was observed in the concentration range 0.25–2.5mM, i.e. in the vicinity of CMC. The critical micelle concentration (CMC) of CTAB solutions determined from the conductivity data decreased with the increasing vitamin E content due to the mixed aggregates formation. At the same time the electrophoretic mobility and zeta potential increased as a result of higher degree of the mixed aggregates dissociation. This effect was observed for all surfactant concentrations at both temperatures. The hydrodynamic diameter of mixed CTAB/α-tocopherol particles increased from 7–8nm for the CTAB solutions to 50–60nm for those containing vitamin E. The information about the aggregates size and their electrokinetic properties can be useful in predicting the encapsulation of biomolecules in the surfactant micelles and their transport by different membranes.

Vesicle-templating poly (3,4-ethylenedioxythiophene) hollow microspheres with enhanced electrocatalytic activity toward ascorbic acid oxidation

ABSTRACTPoly(3,4-ethylenedioxythiophene) (PEDOT) hollow microspheres ranging from 50 to 950 nm are synthesized by chemically oxidative polymerization of 3,4-ethylenedioxythiophene using ammonium persulfate in the aqueous solution of cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzenesulfate (SDBS). Vesicles formed by CTAB and SDBS serve as templates for the formation of PEDOT hollow microspheres. The obtained PEDOT hollow microspheres were characterized by Fourier transform infrared spectroscopy, elemental analysis, X-ray photoelectron spectroscopy, and conductivity measurement. Compared to PEDOT granular particles, PEDOT hollow microspheres showed a more effective electrocatalytic activity in lowering the ascorbic acid oxidation potential.

Gold nanoparticles dissolution based colorimetric method for highly sensitive detection of organophosphate pesticides

A simple and sensitive colorimetric method is developed for organophosphrous pesticides (OPs) analysis based on the enzymatic hydrolysis reaction of acetylcholinesterase and the dissolution of gold nanoparticles (AuNPs) in Au3+-cetyltrimethylammonium bromide (Au3+-CTAB) solution. In the absence of OPs, the enzymatic hydrolysis product, thiocholine, would reduce Au3+ and protect the AuNPs from dissolution by the Au3+-CTAB. In the presence of OPs, however, the activity of AChE is inhibited, which could not or could only produce a small amount of thiocholine to consume the Au3+. In this case, the large amount of residual Au3+ dissolves the AuNPs and decreases both the concentration and size of the AuNPs, thus leading to an obvious red-to-light pink or red-to-colorless color change. Under optimal conditions, the colorimetric method could indicate the presence of OPs, with the concentration down to 0.7ppb. After loading AuNPs on a cellulose paper, an AuNPs-coated dipstick is developed for the detection of OPs, which is highly sensitive with an observable limit of detection of 35ppb. Practical sample analyses in tap water, apple washing solution, and sea water indicate the colorimetric method has acceptable accuracy and good stability, even in the system containing 5M of NaCl. Regarding these merits, the as-proposed method could be applied for the point-of-care analysis of OPs in complex systems.

Rheological Properties and Crosslinking Rheo-Kinetics of CMHEC/CTAB Synergistic Systems

Aiming at synergistic interaction between carboxymethyl hydroxyethyl cellulose (CMHEC) and cetyltrimethyl ammonium bromide (CTAB), mixtures of CMHEC and CTAB solutions were investigated, employing relative viscosity and rheological measurements. The effects of mass ratio of CMHEC and CTAB solutions, temperature, and polysaccharide concentration on relative viscosities of CMHEC/CTAB systems were studied. Rheological method was used to study rheo-kinetics of the isothermal crosslinking process for CMHEC/CTAB synergistic fracturing fluid, and the novel crosslinking rheo-kinetics equation was established. The results showed the strong synergism between CMHEC and CTAB, resulting in a higher relative viscosity, storage modulus G′, and loss modulus G″ than that of separate ones. CMHEC/CTAB systems behave as pseudoplastic fluids with considerable thixotropy and viscoelasticity, and the flow behavior can be well described by Carreau−Williamson model. The crosslinking rheo-kinetics equation can well describe the isothermal crosslinking process at different shear rates. The model parameters are well-defined and reasonable.

Assessment of swelling inhibitive effect of CTAB adsorption on montmorillonite in aqueous phase

Physicochemical aspect of wellbore stability during drilling shale formations is linked to the interaction between montmorillonite (Mt) and aqueous phase. This study conducts for the first time a comprehensive study to assess swelling inhibitive effect of cetyltrimethylammonium bromide (CTAB), a celebrated cationic surfactant in petroleum industry, adsorption on Mt in the aqueous phase. Initially, the adsorption behavior of CTAB on Mt below and above the critical micelle concentration (CMC) was assessed by batch equilibrium experiments and then the adsorption data were examined using four famous adsorption equilibrium models. It was found that Mt has a great tendency to adsorb CTAB. Furthermore, the equilibrium data for monomeric and micellar adsorptions suited very well to Langmuir and Linear isotherms, respectively. The swelling inhibitive feature of CTAB was explored through extensive experiments comprising mud making, settlement, filtration, zeta potential, particle size, water adsorption, scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). In contrast to deionized water, CTAB aqueous solution exhibited fairly low rheological profile with larger amount of Mt loading (225g/L). The dispersion of pre-hydrated Mt was fully unstable after being exposed to CTAB. Mt lost completely its ability to control fluid loss in aqueous solution of CTAB. The addition of CTAB to Mt dispersion extremely changed the magnitude of zeta potential from negative to positive, specifically before micelles formation. Compared to deionized water, Mt particles gave larger particle sizes in aqueous solution of CTAB, indicating the low degree of particle delamination. The affinity of Mt to water decreased by about 70% after modification via CTAB. Unlike deionized water, modification of Mt in aqueous solution of CTAB led to the larger size of aggregates, according to SEM analysis. TGA demonstrated that modified Mt in aqueous solution of CTAB has 4.68% water content less than that of modified in deionized water. The findings convey the message that CTAB can act as a far superior clay stabilizer at concentration much higher than CMC. Finally, Fourier transform infrared spectroscopy (FT-IR) analysis was carried out to prove the adsorption of CTAB on Mt. It was concluded that the intercalation of CTAB (molecules and CTA+) into the interlayer space of Mt through cation exchange and hydrophobic interaction is probably the main inhibition mechanism.

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

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

The modified nanocrystalline cellulose for hydrophobic drug delivery

In this work, torispherical nanocrystalline cellulose (NCC) was synthesized, and firstly modified with a cationic surfactant cetyltrimethylammonium bromide (CTMAB). It was proved that the kinetics of NCC adsorbing CTMAB followed the pseudo-second-order kinetics equation, and the adsorption isotherm model followed Freundlich which was multi molecular layer adsorption model. The morphology and structure of NCC and CTMAB-coated NCC were characterized by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). Stabilities of NCC and CTMAB-coated NCC were assayed by zeta potential. The results showed that NCC in CTMAB solution was well-dispersed and stable. Moreover, the drug loading and release performance of CTMAB-coated NCC were studied using luteolin (LUT) and luteoloside (LUS) as model drugs.