Cetyltrimethylammonium Bromide Concentration Research Articles

Pyrene Associates As a New Highly Sensitive Sensor for Monitoring the Content of Silver Nanoparticles in Aqueous Media

A study is performed of the luminescence of pyrene molecules solubilized in a supramolecular ordered structure formed as a result of the self-organization of molecules of cationic surfactant cetyltrimethylammonium bromide (CTAB) in the presence of trace amounts of aggregated silver nanoparticles (NPs). The study is performed using dilute aqueous solutions of CTAB and at CTAB concentrations that exceed the critical micelle concentration. The formation of a number of pyrene associates (high-energy excimers) that glow in the short-wavelength region of the optical spectrum is observed, relative to the glow of a low-energy dimer (470 nm), and the intensity of the glow of the resulting associates depends on the concentration of silver aquasol introduced into the considered solution. The phenomenon is explained by the location of pyrene molecules near the surfaces of aggregated silver nanoparticles, which have high-density electromagnetic fields caused by surface plasmon resonance. It is found that pyrene associates can be used as sensors for determining trace amounts of silver NPs in aqueous media.

Role of mixed micellar media to enhance solubilization of Allura Red: differential spectroscopic and conductometric study

The reported work is an attempt to explore the most appropriate micellar media for the solubilization of organic dye, Allura Red (AR). The micellar solution of anionic surfactant i.e. sodium dodecyl sulphate, SDS and mixed micellar solutions of SDS and cetyltrimethylammonium bromide, CTAB (cationic surfactant) have been employed for said purpose. The values of partition coefficient, K x and Gibbs free energy change of partition, ΔG p decide the suitable composition of surfactant solution with the highest solubilizing power. The said parameters have been determined from data of UV/Visible spectroscopy while thermodynamic parameters (ΔG m, ΔH m and ΔS m) have been calculated from specific conductivity data. The effect of the presence of various concentrations of CTAB i.e. 0.1, 0.2 and 0.4 mM has been observed to find the most suitable concentration of CTAB that produces a maximum increase in the solubilizing capacity of SDS solution.

Eco-friendly approach for preparation of water-based superhydrophobic silica aerogels via ambient pressure drying

In this work, superhydrophobic methyltrimethoxysilane (MTMS)-based silica aerogels were fabricated via water-based sol–gel reaction by ambient pressure drying (APD) method in the presence of surfactant. The structure, morphology, and hydrophobic properties of the obtained silica aerogel were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) methods, X-ray diffractometer (XRD), and water contact angle measurement. The effects of the concentration of MTMS, the pH value of the solution, and the amount of surfactant cetyltrimethylammonium bromide (CTAB) on properties of silica aerogels were investigated, respectively. Increasing the concentration of MTMS to a great extent resulted in higher density and lower porosity of silica aerogel. Alkali catalyst was an extremely crucial factor for preparing silica aerogels. With the increase of the pH value from 7.5 to 10 the gelation time of the prepared aerogels was observed to decrease from 40 min to 2 min, and the shrinkage of aerogel sample decreased from 15.5% to 3.5%. The skeleton structure of the prepared silica aerogel gradually transformed from coarsened spherical to continuous irregularity finer structures with the increased concentration of CTAB. In addition, the prepared silica aerogel showed outstanding anti-adhesion property and superhydrophobic ability with a water contact angle (WCA) of 160.6 ± 1.3°.

The effect of CTAB, a cationic surfactant, on the adsorption ability of the boron-doped diamond electrode: Application for voltammetric sensing of Bisphenol A and Hydroquinone in water samples

The present study introduces for the first time the effect of the cationic surfactant, cetyltrimethylammonium bromide (CTAB) on the adsorption capability of the boron-doped diamond (BDD) electrode for the sensing of environmental pollutants bisphenol A (BPA) and hydroquinone (HQ). Cathodic pretreatment of the electrode surface after an anodic pretreatment exhibited a best electrochemical response for these two phenolic compounds. The electrochemical characteristics of BPA and HQ were first sufficiently documented by cyclic voltammetry in aqueous solutions without the addition of surfactant over a shorter and longer potential range. Square-wave voltammetry was employed for a detailed study depending on the operational conditions (e.g., pH and nature of supporting electrolyte, concentration of CTAB, accumulation variables, instrumental parameters, etc.). The sensitivity of the voltammetric measurements for BPA and HQ was increased when CTAB was present in strong acidic media (more effective for BPA) due to its interaction with the neutral forms of the selected compounds on the hydrophobic surface of BDD electrode. Besides, a significant increase in the detecting sensitivity of BPA in CTAB-containing solutions could be obtained after applying an accumulation process. Using square-wave stripping mode (after 30 s accumulation at open-circuit condition) in 0.1 M H2SO4 containing 1 × 10−4 M CTAB, the limits of detection were found to be 0.05 μg/mL (2.19 × 10-7 M), and 0.23 μg/mL (2.09 × 10-6 M) for the simultaneous determination of BPA and HQ, respectively. In this way, modification-free BDD electrode could introduce an alternative to chemically modified electrodes for the analysis of environmental samples.

Morphology-controlled synthesis of one-dimensional zinc molybdate nanorods for high-performance pseudocapacitor electrode application

Nanorod-shaped Zinc molybdate (ZnMoO4) materials have been prepared using a cetyl-trimethylammonium bromide (CTAB) template-assisted hydrothermal synthesis, followed by subsequent calcination process. The morphology and size of the ZnMoO4 can be altered by adjusting the concentration of CTAB. The optimal concentration of CTAB provides nanorod-shaped ZnMoO4, which accordingly determines the electrochemical features of prepared supercapacitor electrodes. The electrochemical properties were examined using cyclic voltammetric (CV) and chronopotentiometric (CP) techniques. The cyclic voltammetric studies confirm the pseudocapacitor mechanism with the specific capacitance of 779 Fg−1 at a scan rate of 5 mVs−1. Furthermore, the chronopotentiometric studies deliver the specific capacitance of 540 Fg−1 at a current density of 1 Ag−1. Besides, the ZnMoO4 demonstrated outstanding cyclic stability and the capacitance retention of about 90% was observed even after continuous 3000 cycles at a scan rate of 100 mVs−1. This endeavor demonstrated an important promising approach to synthesize ZnMoO4 nanorods with high specific capacitance, rate capability and superior cycle stability, which have attractive interest to be the candidate for electrode materials towards high-performance supercapacitor applications.

Cyclodextrins as mobile phase additives in open-tubular admicellar electrochromatography for achiral and chiral separations

Native cyclodextrins (α-, β- and γ-CD) which are traditional chiral selectors in capillary electrophoresis were studied in open-tubular admicellar electrochromatography (OT-AMEC) using cetyltrimethylammonium bromide (CTAB) as dynamic stationary pseudophase. The initial mobile phase was 0.2 mM CTAB in 25 mM sodium tetraborate (pH 9.2), which forms admicelles (bilayer) at the solid surface/liquid interface inside the capillary. Different molar ratios of [CD]:[CTAB], i.e., 0:1 to 2:1 for [α-CD]:[CTAB] and [β-CD]:[CTAB] and 0:1 to 20:1 for [γ-CD]:[CTAB] in the mobile phase were investigated. An increase in the CD concentration decreased the magnitude of the electroosmotic flow (EOF). This suggests that CDs increase the critical surface aggregation concentration of CTAB, reducing the amount of free CTAB available to aggregate at the solid surface/liquid interface. At a molar ratio of 1.5:1 for α-CD, 2:1 for β-CD and 20:1 for γ-CD, the EOF changed from anodic to cathodic in direction. This suggests that no admicelles were formed under these conditions. Consequently, the retention factors (k) of the tested analytes (dichlorprop, fenoprop, ibuprofen, ketoprofen, propranolol, verapamil, hexanophenone, verapamil and valerophenone) decreased until k = 0 (no admicelles or stationary pseudophase). We observed a change in the migration orders of the analytes because of the resulting change in the effective electrophoretic mobility. Finally, we achieved chiral separation of mecoprop and dichlorprop in OT-AMEC with α- or β-CD in the mobile phase, which was not possible in electrokinetic chromatography using the same α- or β-CD concentration in the background solution. The chiral separation was aided by the retention caused by the dynamic stationary pseudophase.

Microwave absorption properties of spheres-assembled flake-like FeNi3 particles prepared by electrodeposition

Flake-like FeNi3 particles based on submicrometre spheres self-assembly were prepared by electrodeposition method using cetyltrimethylammonium bromide (CTAB) as the morphology modifier. To explore the formation mechanism of the novel flaky structures, three different concentrations of CTAB were employed to electrodeposit FeNi3 particles in the experiment. Linear sweep voltammetry were conducted to measure cathodic polarization curves of the corresponding three solutions. The crystal structure, morphology and electromagnetic properties of corresponding three samples were characterized by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometry, vector network analysis. The effects of CTAB on the morphologies and structures of the FeNi3 particles were investigated. When the concentration of CTAB is 1.0 g/L, the prepared sample exhibited the best microwave absorption properties as a consequence of better electromagnetic impedance matching. The effective absorption bandwidth (RL < −10 dB) increases with decreasing thickness, reaching 4.32 GHz (13.2–17.52 GHz) when the absorber thickness is only 1.3 mm. The minimum reflection loss (RL) reaches −50.42 dB at 3.44 GHz. The absorbent with thickness of 1.3–2.5 mm obtains RL values exceeding −10 dB over a wide frequency range of 4.40–17.52 GHz, which covers almost the whole C, X and Ku-band (4–18 GHz). The microwave absorption properties of as-prepared FeNi3 particles possess the advantage of broad absorption bandwidth especially at thin thickness.

Cetyl Trimethyl Ammonium Bromide as Anti-Pit Agent for Mild Steel in Sulfuric Acid Medium

Aim: Pitting corrosion is a very serious problem for mild steel when it comes in contact with the dilute sulfuric acid medium. Specialized corrosion inhibitors are essentially required to minimize pitting and uniform types of corrosion in mild steel. Background: Most of the corrosion inhibitors discovered so far protects the mild steel from uniform type of corrosion. But pitting corrosion is more fatal than a uniform type of corrosion because it immediately makes mild steel unfit for use as leakage starts from the pit. Objective: The objective was to protect the mild steel alloys from pitting corrosion when comes in contact with dilute sulfuric acid by the use of organic corrosion inhibitor. Methods: Cetyl Trimethyl Ammonium Bromide (CTAB) is tested as a corrosion inhibitor for mild steel in 0.1 N H2SO4 as corroding medium at 25.0, 30.0 and 35.0°C by weight loss, electrochemical polarization, and Impedance spectroscopy methods. Surface study of corroded and un-corroded specimens of mild steel was carried out by Metallurgical Research Microscopy (MRM) and Scanning Electron Microscopy (SEM) techniques. Results: Surface study confirms that the adsorption of CTAB takes place through nitrogen atom resulting in the formation of uniform, nonporous, passive film confirmed by decrease in Warburg Impedance (Zw), decrease in Faradaic current, increase in Capacitive current, an increase in charge transfer resistance, Rct (41 to 401 Ω cm2) and significant increase in capacitive loop in Nyquist plot with increase in concentration of CTAB which results in significant decrease in corrosion rate of mild steel in 0.1N H2SO4 medium (percentage corrosion inhibition efficiency: 95.0%) especially eradicating pitting type of corrosion. Conclusion: CTAB was proved to be a very good anti-pit agent for mild steel in 0.1N sulfuric acid medium. Pitting and uniform type of corrosion was significantly reduced by the use of CTAB as corrosion inhibitor for mild steel in the dilute sulfuric acid medium at 25.0, 30.0 and 35.0°C.

Investigation of NLO Properties of Eriochrome Black T Colloidal Solution: Role of Surfactant and Reverse Micelles

The photophysical and nonlinear optical properties of Eriochrome Black T (EBT) in micelles, with two charge types of surfactant and reverse micelles (RMs) in a wide range of sizes, were investigated via ultraviolet–visible absorption, fluorescence spectroscopy, and a Z-scan technique. Accordingly, a significant redshift in absorbance and fluorescence quenching of the EBT was observed with an increase in cetyltrimethylammonium bromide (CTAB) concentration. Comparably, the nonlinear absorption coefficient (β) of the EBT decreased following an increase in cationic CTAB concentration, due to an increasing trend in the CTAB:EBT complex in the solution, and it decreased following an increase in anionic aerosol OT concentration. The same behavior was further detected for the nonlinear index of refraction (n2). The β value of the EBT also decreased with an increase in the size and concentration of the RMs, while the n2 was enhanced.

Surfactant – Controlled synthesis of polygonal-stacked Cu2O for morphology effect on lithium-ion battery anode performance

Recently, lithium‐ion batteries have reached the limit of low reversible capacity that is deficient for uses in emerging electric devices for mobiles and electric vehicles (EVs). In this work, we have prepared polygonal-stacked Cu2O (PCO) through modified Benedict's reaction by simply controlling concentrations of cetyltrimethylammonium bromide (CTAB). The synthesized PCO materials featuring sharp tip structure showed enhanced capacity than round edge structured PCO. Surface area and structural difference could play critical roles in the electrochemical performances of the PCO materials. Among three different structured Cu2O materials, sharp tip shaped PCO electrode exhibited a high discharge capacity of ca. 402 mAh/g at the 2nd cycle and its discharge capacity appeared to gradually increase to ca. 506 mAh/g up to the 100th cycle. The diffusion coefficient of sharp tip shaped PCO was also larger than PCO with round-structured morphology. The simple synthesis strategy for the resulting unique electrode morphology can allow to understand morphology effects on anode materials for lithium-ion batteries.

Ceria nanorod supported gold nanoparticles as structured catalysts for the oxidative steam reforming of methanol: Effect of CTAB concentration on physiochemical properties and catalyst performance

Ceria (CeO2) supports were synthesized by hydrothermal treatment with different Cetyltrimethylammonium bromide (CTAB) concentrations (CeO2-X: 0.135, 0.270, 0.540 and 1.080, where X is the CTAB concentration in mmol). The micro-structures of bundle-like ceria nanorods (NR) were produced by thermal treatment of the crystalline Ce(OH)CO3 precursor. The exposed crystal planes of (200) and (111), corresponding to the d-spacing of 0.27 and 0.31 nm, were confirmed by high resolution-transmission electron microscopy (HR-TEM). The fundamental characteristics of CeO2-0.135 led to the highest surface area, surface area normalized reducibility and oxidized gold species (Aun+/Au0) on the surface, relatively higher oxygen vacancies and a smaller average gold particle size (7.9 nm). The activity results show that the Au/CeO2-0.135 has the highest methanol conversion and H2 production rate for oxidative steam reforming of methanol (OSRM). The reducibility and gold particle size played a crucial role in determining the H2/CO2 ratio at the temperature of 200 °C.

Key parameters to improve zeolites hierarchization in direct synthesis

In this study, we propose the generation of micro/mesoporous zeolites with ZSM-11 structure by hydrothermal treatment using tetrabutylammonium hydroxide (TBAOH) as micropore structure directing agent and cetyltrimethylammonium bromide (CTAB) as mesotemplate. From many synthesis parameters evaluated (crystallization time, hydrothermal temperature, CTAB content), the type of base employed in the synthesis gel showed notorious influence in the structure, textural properties and morphology of the micro/mesoporous ZSM-11 zeolites. The samples were characterized by different techniques such as X-ray diffraction, nitrogen adsorption and desorption isotherms, Brunauer–Emmett–Teller surface area, scanning electron microscope, ICP-AES and 27Al MAS NMR. The characterization results revealed that the crystallization time, CTAB content and type of base (NaOH, KOH, Ca(OH)2 and NaCO3) played a dominant role in controlling the formation of both microporous and mesoporous structures. The base employed in the synthesis and its concentration showed important effects on the structure and textural properties of the composite materials. It was found that to obtain the best characteristics in terms of crystallinity and textural parameters, NaOH and KOH should be employed.

Separation performances of a multi-stage continuous bubble cap foam fractionation column

ABSTRACT A multi-stage continuous bubble cap foam fractionation column was developed to achieve high separation performance using cetyltrimethyl ammonium bromide (CTAB) as a model surfactant. The effect of design and operating parameters on the overall performances was investigated at a steady state. The results illustrated that with increasing the airflow rate, the enrichment ratio of CTAB was decreased and its recovery percentage increased. When the feeding concentration of CTAB was greater than 0.2 g/L, the adsorption of CTAB at the gas-liquid interface was closed to equilibrium. Based on mass balances and equilibrium relationships, a new method of the number of theoretical stages by stage-to-stage calculation and graphics were presented on the foam fractionation column.

Truncated Triangular Silver Nanoparticles using low concentration of CTAB

Triangular silver nanoparticles have special properties which increase their importance in chemistry, biology, physical and medical applications. This work concerns with fabrication of truncated nanotriangles, using a simple chemical method. The seed mediated growth method that is usually used to synthesize nanorods, is modified to create nanotriangles. By using this modified method, we successfully obtained silver truncated nanotriangles by adding low concentration of cetyltrimethylammonium bromide (CTAB) into seed solution. UV-visible spectroscopy (UV-Vis) was used to characterize the surface plasmon resonance of the formed nanoparticles. Also, the geometrical properties of nanoparticles were characterized by transmission electron microscopy (TEM) and scanning tunneling microscopy (STM). The average edge length of truncated nanotriangle is affected by varying the amount of seed added to the growth solution; it varies from 56 nm up to 75 nm according to the amount of seed used. The degree of truncation (T) for the produced nanotriangle edges has been estimated. Furthermore, the effect of CTAB concentration as well as the speed in which NaBH4 is added to the seed solution on the formed nanoparticles was investigated.

Characterization of Nanostructured Mn-Zn Ferrites Synthesized by Coprecipitation Method Using CTAB

In this work it was investigated the influence of CTAB surfactant concentration on the synthesis of the compound Mn0.75Zn0.25Fe2O4 by the coprecipitation method. It was also compared the influence of hydrothermal treatment on the synthesized materials. The magnetic properties were characterized by AC susceptometry for the determination of the magnetic susceptibility and magnetic density energy. The phases, crystal structure and morphology of the nanoferrites were determined by Rietveld analysis of X-ray diffraction data. It was found the presence of two phases: Franklinite and Akaganeite and it was shown that the samples synthesized only by coprecipitation presented the tendency to increasing the crystallite sizes of the akaganeite phase and decreasing of crystallite sizes of the Franklinite phase as a function of CTAB concentration. The samples submitted to subsequent hydrothermal treatment presented a tendency to decreasing the crystallite sizes of both phases and increasing in Franklinite phase fraction, compared to the samples synthesized only by coprecipitation, suggesting that the hydrothermal treatment was effective in obtaining nanostructured materials of smaller particles.

Efficient extraction of Rb+ and Cs+ by a precipitation flotation process with ammonium phosphowolframate as precipitant

The properties of a precipitation flotation process for Rb+ and Cs+ extraction from the aqueous solutions are investigated using ammonium phosphowolframate (AWP) as the precipitating agent and cetyltrimethylammonium bromide (CTAB) as the collector and foaming agent in this research. Different parameters including precipitation reaction time, solution pH, ions concentrations, molar ratio of AWP to Rb+/Cs+, and surfactant dosage, were studied. The results show that the extraction efficiency can up to almost 100 % under the optimum experimental conditions as: Contact time at 30 min, mixing speed at 500 rpm, pH at 10, CTAB concentration at 0.15 mmol L−1, Rb+/Cs+ concentration at 1 mmol L−1, the molar ratio of AWP to Rb+/Cs+ at 1:1. The energy analysis of DFT calculation determined that the binding site of Rb+/Cs+ is a four-membered ring of phosphowolframate. IGM reveals the non-covalent interaction between Rb+/Cs+ and phosphowolframate, proving that there are electrostatic attraction and Van der Waals effect between Rb+/Cs+ and the bridge oxygen of the four-membered ring of phosphowolframate ion. The analysis of flotation mechanism reveals that electrostatic attraction is the main force in the flotation process. The results of this research prove that precipitation flotation method has great potential in Rb+ and Cs+ separation as a salt lake brine treatment technology.

Reductive degradation of chlorinated organophosphate esters by nanoscale zerovalent iron/cetyltrimethylammonium bromide composites: Reactivity, mechanism and new pathways

Chlorinated organophosphate esters (Cl-OPEs), e.g., tris(2-chloroethyl) phosphate (TCEP), tris(2-chloro-2-propyl) phosphate (TCPP) and tris(1,3-dichloro-2-propyl) phosphate (TDCPP), are widely used as additive flame retardants in commercial and building products. They have potential persistent organic pollutant properties and are frequently detected in various waters, especially in wastewaters. Nanoscale zerovalent iron (nZVI)-based method is an efficient reductive technology for treating waters polluted by halogenated organic pollutants (HOCs). Cetyltrimethylammonium bromide (CTAB) is a ubiquitous surfactant in wastewaters and can favorably affect the interaction between HOCs and nZVI. However, its effect on the Cl-OPEs removal by nZVI-based materials still remains unknown. Herein, the adsorption and degradation efficiencies of Cl-OPEs by nZVI and sulfidated nZVI (S-nZVI) in the presence or absence of CTAB were quantified based on the decreasing concentrations of Cl-OPEs in reaction systems. Our results showed that TDCPP and TCPP were adsorbed onto the nZVI or S-nZVI surface and subsequently degraded. In contrast, TCEP was just adsorbed onto the particle surface without further degradation. The addition of CTAB significantly enhanced the hydrophobic adsorption between Cl-OPEs and nZVI or S-nZVI, leading to increased degradation of Cl-OPEs (especially TCEP). CTAB adsorption isotherms indicated that S-nZVI had a higher adsorption capacity for CTAB than nZVI. The S-nZVI/CTAB composite exhibited a better performance than nZVI/CTAB composite. When S-nZVI was combined with 100.0 mg L−1 CTAB, 100% of TDCPP, TCPP and TCEP was degraded within 3 hours, 5 and 14 days, respectively. As the concentration of CTAB was increased up to 335.0 mg L−1, TCEP could be completely degraded within 3 days by S-nZVI. Five degradation products of TCEP were identified, of which O,O-di-(2-chloroethyl) O-ethyl phosphate (DCEEP) and ethane were reported for the first time. We propose that TCEP is dechlorinated by nZVI or S-nZVI through the electron attack at the ethyl-chlorine group to form bis(2-chloroethyl) phosphate, DCEEP, chloride, ethene and ethane, representing previously unknown degradation pathways.

Facile Synthesis and Characterization of Cu3(MoO4)2(OH)2 Nanorods for High Performance Supercapacitor Electrode Application

AbstractIn the present study, Cu3(MoO4)2(OH)2 electrode materials were prepared by CTAB assisted hydrothermal method. Thermal, crystalline and bonding properties of freshly prepared samples were confirmed by thermo gravimetric analysis (TGA), x‐ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman analyses. The surface morphological features of Cu3(MoO4)2(OH)2 electrode materials were observed via Scanning electron microscopy (SEM) analysis. The concentration of cetyl trimethyl ammonium bromide (CTAB) template has much influenced in nanomaterial formation and the high concentration (3 mM) of CTAB provides nanorod structures. The electrochemical analysis of Cu3(MoO4)2(OH)2 electrodes were demonstrated via cyclic voltammetry (CV), chronopotentiometry (CP) and cyclic stability analyses. The electrochemical investigations of Cu3(MoO4)2(OH)2 electrode provide remarkable specific capacitance of 532 F g−1 at a scan rate of 5 mV s−1 and good cyclic stability of 98 % retention even after 5000 cycles at a scan rate of 20 mV s−1 with good rate capability. These outcomes prompted to assign a probable application for the synthesized Cu3( MoO4)2(OH)2 to utilize as a capable electrode material for supercapacitor applications.

Polymethylmethacrylate derivatives Eudragit E100 and L100: Interactions and complexation with surfactants

Precipitation or coprecipitation of polyelectrolytes has been largely investigated. However, the precipitation of polyelectrolytes via addition of charged and non‐charged surfactants has not been systematically studied and reported. Consequently, the aim of this work is to investigate the effect of different surfactants (anionic, cationic, non‐charged and zwitterionic) on the precipitation of cationic and anionic polymethylmethacrylate polymers (Eudragit). The surfactants effect has been investigated as a function of their concentration. Special attention has been dedicated to the CMC range and to the colloidal characterization of the formed dispersions. Moreover, the effect of salt (NaCl) and pH was also addressed. It is pointed out that non‐ionic and zwitterionic surfactants do not interact with charged Eudragit E100 and L100. For oppositely charged Eudragit E100/SDS and Eudragit L100/CTAB, precipitation occurs, and the obtained dispersions have been characterized in terms of particle size distribution and zeta potential. It was established that the binding of SDS molecules to Eudragit E100 polymer chains is made through the negative charges of the surfactant heads under the CMC value whereas binding of CTAB to Eudragit L100 chains is made at a CTAB concentration 5 times above its CMC. For Eudragit E100/SDS system, a more acidic medium induces aggregation. A same result was observed for the Eudragit L100/CTAB at a more basic pH. Moreover, it was observed that increasing salt concentration (higher than 100 mM) led to aggregation as generally observed for polycations/anionic surfactant systems.

Extraction of cellulose nanocrystals from microcrystalline cellulose for the stabilization of cetyltrimethylammonium bromide-enhanced Pickering emulsions

The cellulose nanocrystals (CNCs) synthesized by sulfuric acid hydrolysis are highly hydrophilic and prone to form the agglomerations due to the hydrogen bonding, which limit their applications in the formulations of Pickering emulsions. For this reason, we selected microcrystalline cellulose (MCC) as the raw material for the extraction of CNCs through sulfuric acid hydrolysis and hydrogen peroxide oxidation, and then combined the surfactants of cetyltrimethylammonium bromide (CTAB) and CNCs to prepare the (O/W) Pickering emulsions by high-speed shearing method. The physicochemical properties of the resultant CNCs were evaluated by scanning electron microscopy (SEM), atomic force microscope (AFM), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). The formed emulsions were characterized by fluorescent microscope (FM). And the effects of the CTAB concentration, pH and ionic strength on the stability of the formed Pickering emulsions were also investigated. Experimental results showed that the sulfuric acid hydrolysis of MCC induced the removal of the amorphous components and the cleavage of the crystalline microfibrils, making CNCs exhibit the curled and rod-like shape with the average hydrodynamic diameter of 460.5 nm (PDI = 0.585), zeta potential of -34.1 mV and the crystallinity index (CrI) of 77.3 %, which revealed good colloidal properties. In addition, the optimal emulsification conditions for CTAB concentration, pH and ionic strength were respectively 0.5 CMC, 11 and 20∼60 mmol/L. On the basis of the above results, the Pickering emulsions stabilized by CTAB/CNCs complex may have potential for large applications in foods, cosmetics and medicines.