Increase Of CTAB Concentration Research Articles

Effect of ionic surfactants on the settling behavior of silt

Ionic surfactants are easily adsorbed by silt and clay particles, thus affecting the flocculation characteristics and settling behavior. The settling velocity, typical size, Zeta potential and surface tension of silt flocs were measured in the presence of two different kinds of ionic surfactants. The results indicated that the cetyltrimethylammonium bromide (CTAB, a typical cationic surfactant) can dramatically accelerate the settling of slit particles, while the linear alkylbenzene sulfonate (LAS, a typical anionic surfactant) slightly retarded silt sedimentation to some extent. In still water, the representative settling velocity dramatically increased from 0.36 cm s−1 to 0.43 cm s−1 with the increase of CTAB concentration, which increased by more than 20%. Oppositely, the sedimentation rate decreased from 0.36 cm s−1 to 0.33 cm s−1 with the increase of LAS concentration. In flowing water, as the flow rate increased from 0 to 20 cm s−1 and the ionic surfactant concentration increased from 0 to 10 mg L−1, the sedimentation rate decreased to 57% and 89% in the presence of CTAB and LAS respectively, which was due to an enhanced dispersion of silt particles and a breaking of flocs. The SEM image test shows that the floc particle size increased 1.5 times of the primary particle size under the high CTAB concentration. The flocculation induced by ionic surfactants greatly influences the sediment size as well as the law of settling velocity. The intrinsic influence mechanism was also discussed based on the variations of silt particle properties. This systematic study can be used for further development of flocculation models and particle size distribution of fine-grained soil.

Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties.

Hierarchical MOR-type zeolites were synthesized in the presence of hexadecyltrimethylammonium bromide (CTAB) as a porogen agent. XRD proved that the concentration of CTAB in the synthesis medium plays an essential role in forming pure hierarchical MOR-type material. Above a CTAB concentration of 0.04 mol·L−1, amorphous materials are observed. These hierarchical mordenite possess a higher porous volume compared to its counterpart conventional micrometer crystals. Nitrogen sorption showed the presence of mesoporosity for all mordenite samples synthesized in the presence of CTAB. The creation of mesopores due to the presence of CTAB in the synthesis medium does not occur at the expense of zeolite micropores. In addition, mesoporous volume and BET surface seem to increase upon the increase of CTAB concentration in the synthesis medium. The Si/Al ratio of the zeolite framework can be increased from 5.5 to 9.1 by halving the aluminum content present in the synthesis gel. These synthesized hierarchical MOR-type zeolites possess an improved catalytic activity for n-hexane cracking compared to large zeolite crystals obtained in the absence of CTAB.

Anionic Surfactant Sensing by Optical Properties of Erythrosin B

The nonlinear optical properties, absorbance and fluorescence spectra of Erythrosin B (ErB) aqueous solution in different CTAB concentration was studied. Z-scan technique under laser light excitation at 532 nm, was used for study reverse saturable absorption (RSA) of ErB. it was observed that the RSA of solution depend on CTAB concentration. A enhancing of absorbance and quenching of fluorescence is observed with increase of CTAB concentration in solution and the RSA can reduce the fluorescence intensity. It was proposed that the micelle can reduce the dye aggregation is solutions and it can affect on linear and nonlinear optical properties of ErB.

Gold Nanoparticles of Multiple Shapes Synthesized in l-Tryptophan Aqueous Solution

In this paper, we describe a simple and efficient synthesis of gold nanoparticles (GNPs) of various shapes (spherical, rod-like, hexagonal, truncated triangular, and triangular) using Au(III) reduction in aqueous solutions by l-tryptophan. We evaluated the influences of reaction temperature, foreign metal ions Ag (I), and surfactants of nonionic (polyethylene glycol, PEG), anionic (sodium dodecyl sulfate, SDS), and cationic (cetyltrimethyl ammonium bromide, CTAB) on GNPs synthesis. We characterized the resultant GNPs using UV–visible adsorption spectroscopy, transmission electron microscopy/high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, selected-area electron diffraction, and Fourier-transform infrared spectroscopy. We fabricated the variously sized GNPs by controlling the rate of the reduction of gold ions in aqueous solution by varying the reaction temperature: the higher the temperature, the smaller the gold nanospheres. We found the existence of Ag(I) to reinforce the reduction of Au(III) and to correspond with the appearance of some amorphous bimetallic Au/Ag nanoparticles. Additionally, we found the presence of surfactants to greatly influence the shape of the formed GNPs, especially the presence of CTAB, which results in the anisotropic growth of gold nanocrystals into hexagonal, truncated triangular, and triangular nanoplates. In addition, with the increase in CTAB concentration, we found the amount of gold nanoplates to first increase and then decrease. Finally, we performed preliminary explorations of the reduction process and morphological evolution to propose possible corresponding reduction and morphological evolution pathways.

Effects of CTAB on the structural and dielectric properties of nanostructured polypyrrole-ZrO2 composites

In this paper, the in situ synthesis of ZrO2/PPy nanocomposites using CTAB assisted ZrO2 nanoparticles have been reported. The structural and dielectric properties of these nanocomposites have been studied to understand the interaction of counterparts. Moreover, the influence of CTAB is also studied on the growth and morphology of nanocomposites. The prepared nanocomposites were subjected to x-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and dielectric study. The XRD shows the phase retention of ZrO2 nanoparticles in nanocomposites. The dielectric properties include the measurements of dielectric constant, dielectric loss and ac conductivity in the range 10 Hz–1 MHz. It has been observed that CTAB significantly influence the dielectric properties of these nanocomposites. It has also been observed that the increase in CTAB concentration influence the dielectric behaviour of these nanocomposites. This has been attributed to the CTAB induced phase transition in ZrO2 nanoparticles.

Influence of Alkyl Trimethyl Ammonium Bromides on Hydrothermal Formation of α-CaSO4·0.5H2O Whiskers with High Aspect Ratios

In this paper, the influence of alkyl trimethyl ammonium bromides (CnH2n+1(CH3)3NBr, n = 10, 12, 14, 16, 18, abbreviated as ATAB) on the formation of alpha calcium sulfate hemihydrate (α-CaSO4·0.5H2O) whiskers under a hydrothermal condition (135 °C, 3.0 h) was analyzed. Specifically, it focuses on cetyl trimethyl ammonium bromide (C16H33(CH3)3NBr, abbreviated as CTAB). The rising CTAB concentration from 0 to 9.2 × 10−4 mol·L−1 led to the increase of the average aspect ratio of α-CaSO4·0.5H2O whiskers from 80 to 430, since the selective adsorption of CTAB on the negatively-charged side facets of the whiskers inhibited the growth of the whiskers along the direction normal to the lateral facets. The further increase of CTAB concentration above the critical micelle concentration (abbreviated as CMC) showed little effect on the morphology of α-CaSO4·0.5H2O whiskers, considering that CTAB tended to form micelles instead of being adsorbed on the whisker surfaces. Similar phenomena were observed in other ATABs (n = 10, 12, 14, 18).

Surfactant-mediated amyloidogenesis behavior of stem bromelain; a biophysical insight

Neurodegenerative disorders are mainly associated with amyloid fibril formation of different proteins. Stem bromelain (SB), a cysteine protease, is known to exist as a molten globule state at pH 10.0. It passes through the identical surrounding (pH 10.0) in the gut epithelium of intestine upon oral administration. Protein–surfactant complexes are widely employed as drug carriers, so the nature of surfactant toward protein is of great interest. The present work describes the effect of cationic surfactants (CTAB & DTAB) and their hydrophobic behavior toward amyloidogenesis behavior of SB at pH 10.0. Multiple approaches including light scattering, far UV-CD, turbidity measurements, and dye binding assay (ThT, Congo red and ANS) were performed to measure the aggregation propensity of SB. Further, we monitored the hydrodynamic radii of aggregates formed using dynamic light scattering technique. Structure of fibrils was also visualized through fluorescence microscopy as well as TEM. At pH 10.0, low concentration of CTAB (0–200 μM) induced amyloid formation in SB as evident from a prominent increase in turbidity and light scattering, gain in β-sheet content, and enhanced ThT fluorescence intensity. However, further increase in CTAB concentration suppressed the fibrillation phenomenon. In contrast, DTAB did not induce fibril formation at any concentration used (0–500 μM) due to lower hydrophobicity. Net negative charge developed on protein at high pH (10.0) might have facilitated amyloid formation at low concentration of cationic surfactant (CTAB) due to electrostatic and hydrophobic interactions.

Catalytic Behavior of a Series of Cationic Gemini (16-s-16 Type, s = 4, 5, 6) and CTAB Surfactants on the Reaction of Ninhydrin with [Ni(II)–Gly-Phe

The influence of cationic CTAB/gemini surfactants on the reaction of ninhydrin with the nickel–glycylphenylalanine ([Ni(II)–Gly-Phe]+) complex was investigated spectrophotometrically, at 70 °C and pH = 5.0. The kinetics were found to follow a pseudo-first- and fractional-order reaction path with respect to concentrations of [Ni(II)–Gly-Phe]+ complex and ninhydrin, respectively. The values of rate constant (k ψ) increase with increase in CTAB concentration and reach a maximum value, and then, with further increase in the CTAB concentration, a slow decreasing effect is observed. In the case of geminis, k ψ increase and leveling-off regions (just like the monocationic CTAB) are obtained with [geminis], in addition to a third region of increasing k ψ at higher concentrations. On the basis of the observed data a probable mechanism has been proposed.

Synthesis of nanostructural ZnO using hydrothermal method for dye-sensitized solar cells

ZnO nanocrystals with different morphologies were successful synthesized by a simple hydrothermal method combined with and without hexadecyl trimethyl ammonium bromide (CTAB). The phases and morphologies of the products were measured using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The results indicated that the ZnO nanocrystals with different morphologies were of hexagonal wurtzite structure. ZnO nanorods were obtained without using CTAB, and then the morphology of ZnO changed to ZnO nanoflower and the density of nanoflower became denser with the increase of CTAB concentration. ZnO nanoflower and ZnO nanorod as photoanode were applied to dye-sensitized solar cells (DSSC), respectively. The nanoflower shows a higher dye loading, so DSSC with the use of the ZnO nanoflower possesses a higher conversion efficiency than ZnO nanorod.

Effect of CTAB and procain hydrochloride on neutral red microstructure in CTAB micelle

The effects of cationic surfactant (CTAB) and procaine hydrochloride on the microstructures of neutral red (NR) are studied by UV-Vis spectroscopy, fluorescence spectroscopy and surface tension and conductivity measurements. The obtained results show that the acidic structure of NR can be gradually transformed to its neutral structure with an increase in CTAB concentration. If procaine hydrochloride concentration increases in CTAB/NR/H2O system, the critical micelle concentration of CTAB and the content of the dye neutral structure decrease, but the content of its acidic structure increases. NR is located in the palisade layers of CTAB micelles.

Enhanced optical and field emission properties of CTAB-assisted hydrothermal grown ZnO nanorods

We have developed a simple N-cetyl- N, N, N-trimethyl ammonium bromide (CTAB)-assisted hydrothermal route for the production of ZnO one-dimensional (1D) nanostructures on zinc foil at reaction temperature of 160 °C. With the increase of CTAB concentration, the one-dimensional structures change from microrod to a mixture of nano- and microrod and finally to nanorods. X-ray diffraction studies confirmed the proper phase formation of the grown nanostructures. The room temperature photoluminescence spectra showed that ZnO nanostructures prepared with increased CTAB concentration exhibited enhanced band edge UV emission and also blue shift of the emission peak. All the samples show no defect related green emission. Field emission property of the 1D structures has been investigated in detail. By tuning the CTAB concentration, the field emission property was optimized. The nanorods synthesized with high CTAB showed turn-on and threshold fields of 3.2 and 5 V/μm, respectively, which are comparable to the values for vapour phase synthesized high field emitting ZnO nanostructures.

Controlled Synthesis of Manganese Oxohydroxide (MnOOH) and Mn3O4 Nanorods Using Novel Reverse Micelles

Novel reverse micelles of high CTAB concentration were successfully developed to synthesize MnOOH (manganese oxyhydroxide) nanorods with uniform diameters of about 10 nm and up to 200 nm in length under mild solution conditions and Mn3O4 nanorods with the same morphology could be obtained by calcining the precursors at 450 degrees C. The morphology and microstructure of the nanorods were investigated by transmission electron microscopy (TEM and HRTEM), XRD and TGA. The results showed that the concentration of CTAB was a key factor for the formation of MnOOH nanorods and only above 0.2 M the nanorods could be obtained. Moreover, the length of nanorods increased with the increase of CTAB concentration, while the diameter of nanorods retained steadily. In this way, the length of nanorods could be easily controlled from tens nanometers to hundreds nanometers by increasing the CTAB concentration from 0.35 M to 1.25 M. In addition, in our experiment the products were almost entirely rod-like shape, which indicated this method should be suitable for mass-producing.