Aqueous Cetyltrimethylammonium Chloride Research Articles

PH-Dependent growth of atomic Pd layers on trisoctahedral gold nanoparticles to realize enhanced performance in electrocatalysis and chemical catalysis.

In this work, the controlled epitaxial growth of ultrathin Pd shells of a few atomic layers (denoted as nL) on the surfaces of gold nanoparticle (Au NP) cores of different morphologies (trisoctahedral, cubic, and spherical shapes) in the presence of cetyltrimethylammonium chloride (CTAC) was achieved by regulating the pH value of the aqueous CTAC solution and finely tuning the amount of the Pd precursor. It was found that the critical shell thickness for epitaxial Pd growth at the optimal pH value was 4 atomic layers, taking {331}-faceted trisoctahedral (TOH) Au@PdnL NPs as an example, on the basis of the results of atomic-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images. Moreover, the resulting TOH Au@Pd1L NPs (100.9 m2 g-1, 13.2 A mgPd-1 and 13.1 mA cm-2) exhibited excellent electrocatalytic performance and long-term electrocatalytic activity for ethanol oxidation, around 4.8-fold, 66-fold, and 21.8-fold better than commercial Pd/C catalysts (31 m2 g-1, 0.2 A mgPd-1, and 0.6 mA cm-2). Furthermore, the resulting TOH Au@Pd1L NPs not only markedly enhance the chemical catalytic activity for the reduction of 4-nitrophenol (4-NP), but also allow the in situ surface-enhanced Raman spectroscopy (SERS) monitoring of the reaction process of the Pd-catalyzed reduction of 4-NTP. Thus, our work may provide a new way to fabricate core-shell (CS) bimetallic NPs with the merits of both metal outer shells (excellent catalytic performance in electrocatalysis and chemical catalysis) and Au NP cores (reaction process by in situ SERS monitoring).

On the mechanism of boiling heat transfer enhancement by surfactant addition

In our previous study, bubble jet and bubble explosion around a heated wire were discovered in aqueous cetyltrimethyl ammonium chloride (CTAC) solutions (Wang et al., 2016), in which the bubble explosion process was explained. The bubble explosion phenomenon was proven to be a failed coalescence of unstable bubbles which caused local disturbance and enhanced boiling heat transfer. In this paper, comparative experiments of boiling around a heated wire for different types of surfactant solutions, ethanol and silicone oil were carried out in order to explore the mechanism of surfactant addition enhancing boiling heat transfer. All these fluids had lower surface tensions than that of water. Cationic surfactant of CTAC, anionic surfactant of sodium dodecylbenzenesulfonate (SDBS) and nonionic surfactant of alkyl polyglycoside (APG) were used. Bubble jet and bubble explosion phenomenon were found in all three kinds of surfactant solutions, exhibiting excellent heat transfer effect. For the pool boiling in ethanol, only bubble jet around the heated wire was found, showing better heat transfer efficiency than water. However, weaker boiling heat transfer occurred in silicone oil without bubble jet and bubble explosion. Due to the heat sensitivity characteristics, APG solution had a lower critical heat flux (CHF) than water, while CTAC and SDBS solution had higher CHF. With all phenomena and heat transfer performances, the mechanism of boiling heat transfer enhancement by surfactant addition was confirmed, i.e., the bubble jet and bubble explosion process enhanced the boiling heat transfer in surfactant solution rather than low surface tension.

Flow drag and heat transfer characteristics of drag-reducing nanofluids with CuO nanoparticles

A new kind of aqueous CuO nanofluid with drag-reducing performance was developed. The new working fluid was an aqueous CTAC (cetyltrimethyl ammonium chloride) solution with CuO nanoparticles added and has both special effects of drag-reducing and heat transfer enhancement. An experiment was carried out to investigate the forced convective flow and heat transfer characteristics of conventional drag reducing fluid (aqueous CTAC solution) and the new drag-reducing nanofluid in a test tube with an inner diameter of 25.6 mm. Results indicated that there were no obvious differences of the drag-reducing characteristics between conventional drag reducing fluid and new drag-reducing nanofluid. However, their heat transfer characteristics were obvious different. The heat transfer characteristics of the new drag-reducing nanofluid significantly depend on the liquid temperature, the nanoparticle concentration and the CTAC concentration. The heat transfer enhancement technology of nanofluid could be applied to solve the problem of heat transfer deterioration for conventional drag-reducing fluids.

Silica nanofiber with hierarchical pore structure templated by a polymer blend nanofiber and surfactant micelle

Silica nanofibers with a hierarchical pore structure were fabricated via electrospinning, evaporation-induced phase separation and surfactant-templating. Porous polyacrylonitrile (PAN) nanofibers were prepared by electrospinning a blend solution of PAN and polyethylene glycol (PEG), followed by leaching the PEG from the obtained PAN/PEG blended nanofibers using water. The PAN nanofibers possessed continuous internal pores on a 10nanometer scale that were caused by evaporation-induced phase separation during electrospinning. Porous silica nanofibers were prepared by impregnating these PAN nanofibers with tetraethoxy silane (TEOS) and then immersing them in an aqueous cetyltrimethylammonium chloride (CTAC) and HCl solution, which induced silica formation in the pores of the PAN nanofibers. The silica nanofibers were hundreds of nanometers in diameter, which was significantly reduced relative to the PAN nanofiber templates. Silica nanofibers prepared using an adequate CTAC concentration possessed hierarchical pore structures with smaller pores 2–3nm in diameter that were templated by CTAC micellar structures and larger pores 10–20nm in diameter that were transferred from the porous PAN nanofibers. .

Forced convective flow and heat transfer characteristics of aqueous drag-reducing fluid with carbon nanotubes added

A new kind of aqueous drag-reducing fluid with carbon nanotubes (CNTs) was developed. The new working fluid was an aqueous CTAC (cetyltrimethyl ammonium chloride) solution with CNTs added and has both special effects of drag-reducing and heat transfer enhancement. The thermophysical and rheological properties of the new working fluid were measured. An experiment was carried out to investigate the forced convective flow and heat transfer characteristics of conventional drag-reducing fluid (aqueous CTAC solution) and the new drag-reducing nanofluid in a test tube having an inner diameter of 25.6 mm. Results indicated that there were no obvious differences of the drag-reducing characteristics between conventional drag-reducing fluid and new drag-reducing nanofluid. However, there were obvious differences of the heat transfer characteristics between both fluids. The heat transfer characteristics of new drag-reducing nanofluid have strong dependences on the liquid temperature, the nanoparticle concentration and the CTAC concentration. The heat transfer enhancement technology of nanofluid could be used to solve the problem of heat transfer deterioration for conventional drag-reducing fluids.

Kinetics of Cleavage of Thiophosphates and Phosphonothioates by Micellar Iodosocarboxylates and Copper Metallomicelles

o-Iodosobenzoate (1, IBA) and 2,3-iodosonaphthoate (2, INA) in aqueous cetyltrimethylammonium chloride ((CTA)Cl) micelles, as well as copper metallomicelles 14, all at pH 8, cleave phosphonothioates (11 and 12), the thiophosphate parathion (10), phosphonate 13, and phosphate 4 (paraoxon). The factors for the kinetic advantages in the cleavages of 12 and parathion range from 103 to 104. Although catalytic turnover of the iodoso reagents is not observed with the thio substrates and is slow with paraoxon, excess IBA/(CTA)Cl destroys paraoxon and parathion with reaction half-lives of 3.0 and 7.7 min, respectively, at pH 8.0 and 25 °C. The cleavages of 12 and parathion by IBA or INA involve an initial hydrolytic step followed by oxidation of the sulfur-containing fragment. Cleavages of 12 and parathion by o-iodoxybenzoate (1X, IBX) in (CTA)Cl micelles are much slower than the comparable reactions mediated by IBA, INA, and 14.

Cryo-TEM Imaging the Flow-Induced Transition from Vesicles to Threadlike Micelles

Transition of vesicles to micelles induced by flow of dilute aqueous cetyltrimethylammonium chloride (CTAC)/sodium 3-methylsalicylate (CH3Sal-) dispersion was directly imaged by rapidly vitrifying small ultrathin specimens after varying periods of postflow on-the-grid relaxation, and then examining them by cryogenic-temperature transmission electron microscopy (cryo-TEM). Vesicles prevail in quiescent equimolar 5 mM dispersions of CTAC and NaCH3Sal at equilibrium. When the dispersions are deformed and strained by rapid drainage of the excess from the specimens, the vesicles transform into an entangled network of threadlike micelles. The micelles revert to vesicles with time after drainage flow ceases. Intermediate structures during the transition were also captured by cryo-TEM. We hypothesize that the straining actions of flow disrupt vesicles, distort the distribution of, or strip, the counterions around vesicle fragments, shift the binding and dissociation equilibrium of counterions, alter the local pre...

Effects of Association Colloids on Elimination from 1,2-Dihalo-1,2-diphenylethanes. The Role of Surfactant Structure

Rates of E2 elimination of D,L-1,2dichloro-1,2-diphenylethane (1) and the analogous dibromide (2) were measured in aqueous cetyltrimethylammonium chloride and hydroxide (CTACI and CTAOH), cetyltripropylammonium hydroxide (CTPAOH), didodecyldimethylammonium chloride and hydroxide (DDDACI and DDDAOH), and N,N-dimethyl-N-(2-hydroxyethyl)-n-hexadecylammonium hydroxide (DOH,OH). Micelles or other association colloids of these surfactants increase rates in solutions that contain OH-, and DOH,-OH is much more effective than the nonfunctional surfactants. Variations of first-order rate constants, k obs , with [surfactant] or [OH-] are fitted by a pseudophase model with water and micelles as distinct reaction media, to give second-order rate constants in the latter. These rate constants are in the sequence DOH,OH > CTPAOH DDDACl > DDDAOH CTAOH > CTACl. Micelles favor reactions of 2 over 1, relative to reactivities in water, due to differences in amphiphilic interactions with the leaving halide ions.

Dipyridamole Interacts with the Polar Part of Cationic Reversed Micelles in Chloroform:1H NMR and ESR Evidence

The interaction of dipyridamole (DIP) with reversed micelles (RM) of cetyltrimethylammonium chloride (CTAC) in CDCl3at different water contents was studied. The position andT1relaxation of the water peak upon addition of extra water revealed three concentration ranges of CTAC: <10 mM(impurity water is mainly dispersed in CDCl3), >50–100 mM(water mainly inside the RM), and intermediate range. The resonances of CTAC protons in the polar layer broadened and displaced by up to 0.07 ppm as a function of CTAC concentration and extra water. At 10 mMCTAC, the addition of 40 mMDIP shifted the head group signals to high field by about 0.1 ppm. At high and intermediate CTAC concentrations, four nitroxide spin probes, hydrophobic 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), hydrophilic 4-amine-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPAMINE), and lipophilic 5- and 16-doxyl stearic acids (5- and 16-DSA), underwent partial immobilization. The rotational correlation time of TEMPAMINE (rather than TEMPO, 5-, and 16-DSA) in RM moderately increased upon addition of 1.5–2.0 mMDIP. At an excess of CTAC, only one DIP peak at 3.88 ppm remained measurable, and its selectiveT1fell from 0.34 to 0.12 s. The association constant for DIP and CTAC was between 10 and 35M−1. Thus, DIP incorporates into the polar region of RM influencing packing and dynamics of surfactant head groups. In contrast, in aqueous CTAC micelles, the preferential localization of DIP substituents is inside the nonpolar micelle core, and the binding constant is two orders of magnitude above that for RM.

Effects of Aluminate and Silicate on the Structure of Quaternary Ammonium Surfactant Aggregates

The effect of ionic aluminate and silicate species on the structure of surfactant aggregates used in the preparation of mesoporous aluminosilicates was investigated using dynamic light scattering and rheological techniques. Aqueous cetyltrimethylammonium chloride (CTAC) solutions saturated with sodium aluminate, sodium silicate, or tetramethylammonium silicate were studied over a wide range of CTAC concentrations (1.0−25.0 wt %), which included both spherical and rod-shaped micellar regimes. Sodium aluminate was observed to have no effect on the structure of CTAC micelles and so plays no role in aggregate formation in the prereaction stage of the production of aluminosilicates such as MCM-41. Silicate anions from sodium silicate and tetramethylammonium silicate strongly affected CTAC micelle formation, promoting the formation of flexible wormlike micelles at dilute concentrations in which elongated wormlike micelles are not entangled. The condensation of silicate ion with the tetramethylammonium cation in CTAC/tetramethylammonium silicate solution inhibited the condensation of silicate ion at the surface of the CTAC micelles. Results strongly suggest that, for the two silicate sources studied, flexible CTAC wormlike micelles surrounded by silicate oligomers are formed first in the preparation of aluminosilicate materials; the subsequent intermicellar condensation of silicate oligomers then leads to the gradual arrangement of the micelles into hexagonal liquid crystalline arrays. The effect of a chloride ion (at a constant molar Cl-/CTA+ ratio of 3.98) was also investigated using sodium chloride. Unlike the aluminate and the silicate ions, a transition between the rodlike and flexible wormlike micellar regions was observed. The semidilute regime, defined as the concentration range over which the collective diffusion coefficient is described by the power law model for single-chain polymer in good solvent, was observed at 11.0−21.6 wt %. The transition into the liquid crystalline regime was observed to begin at 21.6−25.0 wt %.

Mechanism of photosensitized oxidation of tyrosine by gallium or zinc phthalocyanine in homogeneous and aqueous micellar media

The mechanism of the photo-oxidation of tyrosine (Tyr) sensitized by sulphonated phthalocyanine at pH 10 in homogeneous aqueous solution or aqueous cetyltrimethylammonium chloride (CTAC) micellar medium was studied by kinetic analysis and laser flash photolysis. Cationic CTAC micelles promote the importance of a type I mechanism in the photo-oxidation of Tyr sensitized by sodium tetrasulphonated chlorogallium phthalocyanine (GaTSPC) whereas they have little effect on the photo-oxidation of Tyr sensitized by sodium disulphonated zinc phthalocyanine (ZnDSPC). In all cases studied, it was shown that the type I mechanism (electron transfer) takes place more easily using GaTSPC as sensitizer, whereas, using ZnDSPC as sensitizer, a type II mechanism (involving 1O 2) predominates. The results are discussed according to the mutual position of the sensitizer and the substrate in the aqueous micellar medium and the ability of the triplet state of the phthalocyanine to abstract an electron from Tyr.

Change in the micellar aggregation number or in the size distribution? A dynamic fluorescence quenching study of aqueous cetyltrimethylammonium chloride

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChange in the micellar aggregation number or in the size distribution? A dynamic fluorescence quenching study of aqueous cetyltrimethylammonium chlorideSteven Reekmans, Delia Bernik, Marcello Gehlen, Jan van Stam, Mark Van der Auweraer, and Frans C. De SchryverCite this: Langmuir 1993, 9, 9, 2289–2296Publication Date (Print):September 1, 1993Publication History Published online1 May 2002Published inissue 1 September 1993https://doi.org/10.1021/la00033a008RIGHTS & PERMISSIONSArticle Views313Altmetric-Citations31LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Toward a broad spectrum decontaminant for reactive toxic phosphates/phosphonates: [formula omitted]-alkyl-3-iodosopyridinium-4-carboxylates

N - n -hexadecyl-3-iodosopyridinium-4-carboxylate has p K a<5.0, and, in comicellar aqueous cetyltrimethylammonium chloride, rapidly cleaves p -nitrophenyldiphenyl phosphate in acidic solution.