CTAB Micellar Media Research Articles

Catalysis in SDS and CTAB micellar media: Kinetics of base hydrolysis of Bis(2,4,6-tripyridyl-s-triazine) iron (II)

Kinetics of the hydrolysis of [Fe(tptz)2]2+ in the presence of NaOH has been studied in two different types of micellar media: SDS anionic and CTAB cationic. The reaction was found to be much faster in both the micellar media compared to aqueous medium (kSDS = 102.2 X10-4 mol-1dm3s-1, kCTAB = 43.92 X 10-4 mol-1dm3s-1, kaq = 0.115 X10-4 mol-1dm3s-1). The reaction obeys first order kinetics with respect to both the reactants in both the media. The rate constant versus surfactant profile shows a maximum in both cases which is characteristic of a bimolecular micelle catalyzed reaction. The kinetic behaviour has been accounted for by using the Berezin model.

Kinetic and Mechanistic Investigation of Os(VIII)-Catalyzed L-Tryptophan Oxidation by Hexacyanoferrate(III) in CTAB Micellar Medium

Kinetic and Mechanistic Investigation of Os(VIII)-Catalyzed L-Tryptophan Oxidation by Hexacyanoferrate(III) in CTAB Micellar Medium

Rate enhancement of Os(VIII) catalyzed L-phenylalanine oxidation by hexacyanoferrate(III) by CTAB micellar medium: a kinetic study

Rate enhancement of Os(VIII) catalyzed L-phenylalanine oxidation by hexacyanoferrate(III) by CTAB micellar medium: a kinetic study

Cu(II) promoted oxidation of L-valine by hexacyanoferrate(III) in cationic micellar medium

The kinetics of Cu(II) accelerated L-valine (Val) oxidation by hexacyanoferrate(III) in CTAB micellar medium were investigated by measuring the decline in absorbance at 420 nm. By adjusting one variable at a time, the progression of the reaction has been inspected as a function of [OH−], ionic strength, [CTAB], [Cu(II)], [Val], [Fe(CN)63−], and temperature using the pseudo-first-order condition. The results show that [CTAB] is the critical parameter with a discernible influence on reaction rate. [Fe(CN)6]3- interacts with Val in a 2:1 ratio, and this reaction exhibits first-order dependency with regard to [Fe(CN)63−]. In the investigated concentration ranges of Cu(II), [OH−], and [Val], the reaction demonstrates fractional-first-order kinetics. The linear increase in reaction rate with added electrolyte is indicative of a positive salt effect. CTAB significantly catalyzes the process, and once at a maximum, the rate remains almost constant as [CTAB] increases. Reduced repulsion between surfactant molecules' positive charge heads brought on by the negatively charged [Fe(CN)6]3-, OH−, and [Cu(OH)4]2- molecules may be responsible for the observed drop in CMC of CTAB.

Effect of cationic surfactant on Ru(III) catalyzed L‐glutamic acid oxidation by hexacyanoferrate(III)

AbstractIn CTAB micellar medium, the kinetic investigation of Ru(III) promoted oxidation of L‐glutamic acid (Glu) by [Fe(CN)6]3− was carried out by recording the decline in absorbance at 420 nm, which corresponds to [Fe(CN)6]3−. By adjusting one variable at a time, the progression of the reaction has been inspected as a function of [OH−], ionic strength, [CTAB], [Ru3+], [Glu], [Fe(CN)63−], and temperature using the pseudo‐first‐order condition. The findings demonstrate that [OH−], [CTAB], and [Glu] are the key parameters that have a discernible impact on reaction rate. In the studied concentration range of Ru(III), [Fe(CN)6]3−, and at lower [Glu] and [OH−], the reaction displays first‐order kinetics. The incremental trend in reaction rate with electrolyte concentration demonstrates a positive salt effect. CTAB substantially catalyzes the process, and after reaching a maximum, the rate remains nearly constant at increased [CTAB]. The observed decline in the CMC of CTAB may be caused by the reduced repulsion between the positively charged heads of the surfactant molecules caused by the negatively charged OH−, and [Fe(CN)6]3−. The activation parameters also support the outer‐sphere electron transfer mechanism as recommended by us.

Determination of Protonation Constants of Viral Inhibitor, Aurintricarboxylic Acid in SDS and CTAB Micellar Media: A Potentiometric Study

Protonation constants of a viral inhibitor, aurintricarboxylic acid were determined using potentiometric method of data acquisition followed by chemometric modelling methods of analysis in the presence of two different kinds of micellar media, CTAB, a cationic micelle and SDS, an anionic micelle. MINIQUAD75 program was used for the determination of the plausible species and their corresponding formation constants at 303 ± 0.1 K and 0.01 M ionic strength. Five formation constants were identified corresponding to five ionizable hydrogens. Species concentration distribution diagrams were generated using Origin software. Best-fit chemical models were selected on the basis of statistical parameters like standard deviation (SD), U (sum of the squares of the residuals in mass balance equations) and chi-square test. It was found that the formation constants are lower in CTAB micellar medium while there is no significant change in the presence of SDS compared to aqueous medium.

Water based surfactant-assisted synthesis of thienylpyridines and thienylbipyridine intermediates

The connection between heterocyclic systems by forming new CC bond is a relevant topic for the easy preparation of intermediates and functional dyes for technological applications. Several methods were developed in the last decades and the urge for sustainable synthetic chemical methods pushed us to prepare thienylpyridines and two thienylbipyridine ligands by the Suzuki reaction in aqueous CTAB micellar medium and in presence of a Pd catalyst. These intermediates can be found as component of dyes and functional thiophene monomers. Reaction conditions were optimized under both thermal and microwave (MW) activation obtaining good yields (70–93%) using Pd(PPh3)4 as catalyst. Two thienylbipyridine ligands were prepared and the transformation of one of them into a terthiophene-based bipyridine ligand was easily obtained by almost green methods and with very good yield. This clean and sustainable method can be proposed as a green step to obtain intermediates and final dyes for technological applications, such as CO2 reduction, in gram-multigram scale.

Shape-selective synthesis of Sn(MoO4)2 nanomaterials for catalysis and supercapacitor applications.

Size and shape-selective Sn(MoO4)2 nanomaterials have been synthesized for the first time using a simple hydrothermal route by the reaction of Sn(ii) chloride salt with sodium molybdate in CTAB micellar media under stirring at 60 °C temperature for about three hours. Needle-like and flake-like Sn(MoO4)2 nanomaterials were synthesized by optimizing the CTAB to metal salt molar ratio and by controlling other reaction parameters. The eventual diameter and length of the nanoneedles are ∼100 ± 10 nm and ∼850 ± 100 nm respectively. The average diameter of the flakes is ∼250 ± 50 nm. The synthesized Sn(MoO4)2 nanomaterials can be used in two potential applications, namely, catalytic reduction of nitroarenes and as an anodic material in electrochemical supercapacitors. From the catalysis study, it was observed that the Sn(MoO4)2 nanomaterials could act as a potential catalyst for the successful photochemical reduction of nitroarenes into their respective aminoarenes within a short reaction time. From the supercapacitor study, it was observed that the Sn(MoO4)2 nanomaterials of different shapes show different specific capacitance (Cs) values and the highest Cs value was observed for Sn(MoO4)2 nanomaterials having a flake-like morphology. The highest Cs value observed was 109 F g(-1) at a scan rate of 5 mV s(-1) for the flake-like Sn(MoO4)2 nanomaterials. The capacitor shows an excellent long cycle life along with 70% retention of the Cs value, even after 4000 consecutive cycles at a current density of 8 mA cm(-2). Other than the applications in catalysis and supercapacitors, the synthesized nanomaterials can find further applications in photoluminescence, sensor and other energy-related devices.

Exploring the interaction of a micelle entrapped biologically important proton transfer probe with the model transport protein bovine serum albumin.

This article describes the interaction of a micelle entrapped pharmaceutically important isoindole fused imidazole derivative, namely, 1-(2-hydroxy-5-methyl-phenyl)-3,5-dioxo-1H-imidazo-[3,4-b] isoindole (ADII), with the model transport protein bovine serum albumin (BSA). Different spectroscopic techniques such as steady state absorption, emission, circular dichroism, dynamic light scattering, etc., have been employed to explore preferential interaction of this drug template with micelles and protein BSA. Binding of ADII with BSA is found to be enormously modified when it is released from the micellar environment. The binding constant of the ADII-BSA complex is reduced when the probe is released from anionic SDS micelle, whereas the binding is observed to be strengthened in cationic CTAB micellar medium due to the formation of a 1:2 complex (ADII-BSA). Time-resolved studies also support our steady state findings that the released drug from the micellar environment is found to be strongly bound with the protein BSA. Circular dichroism (CD) and dynamic light scattering (DLS) study reveals that the secondary structure of BSA gets some stabilization in SDS medium after binding of drug template to protein. The probable binding location of the probe within the protein cavity (hydrophilic subdomain IA) has been explored from an AutoDock-based blind docking simulation study.

Biomimetic iron(iii) complexes of facially and meridionally coordinating tridentate 3N ligands: tuning of regioselective extradiol dioxygenase activity in organized assemblies

Four mononuclear iron(III) complexes of the type [Fe(L)Cl3] 1-4, where L is a tridentate 3N ligand such as (2-pyridin-2-ylethyl)(pyridin-2-ylmethyl)amine (L1), (methyl)(2-pyridin-2-ylethyl)(pyridin-2-ylmethyl)amine (L2), bis(pyridin-2-ylethyl)amine (L3), and (1-methyl-1H-imidazol-2-ylmethyl)(pyridin-2-ylethyl)amine (L4), have been isolated and studied as functional models for catechol dioxygenase enzymes. In [Fe(L2)Cl3] 2, the ligand L2 is coordinated facially to iron(III) whereas in [Fe(L1)Cl3] 1 and [Fe(L4)Cl3] 4 the ligands L1 and L4 are coordinated meridionally. In DCM, CH3CN and aqueous SDS, CTAB and TX-100 micellar media, the positions of both the low and high energy catecholate-to-iron(III) LMCT bands (465-530, 690-860 nm) observed for the 3,4-di-tert-butylcatecholate (DBC(2-)) adducts of the iron(III) complexes vary in the order 2 > 1 > 3 > 4, which reflects the influence of the stereoelectronic factors, mode of coordination and the chelate ring size formed by the tridentate ligands. Spectral and electrochemical studies disclose the formation and location of the cationic adducts as solvated [Fe(L)(DBC)(H2O)](+) species mostly in the aqueous micellar pseudophases of SDS and TX-100 and in the aqueous phase of CTAB micellar solution. The [Fe(L)(DBC)Cl] adducts of 1, 3 and 4, generated in situ, afford major amounts of intradiol cleavage products (17.0-70.0%) and smaller amounts of extradiol (1.2-4.2%) products with varying extradiol to intradiol cleavage product selectivity (E/I: 1, 0.08 : 1; 3, 0.02 : 1; 4, 0.3 : 1). On the other hand, interestingly, the adduct [Fe(L2)(DBC)Cl] of 2 generated in DCM yields a major amount of extradiol (54.0%) and a lower amount (18.3%) of the intradiol cleavage products (E/I, 3 : 1). Remarkably, in aqueous SDS micellar media, it shows exclusive extradiol cleavage products (79.4%) while all the other complexes show very low selectivity (E/I: 1, 0.03 : 1; 2, 79.4 : 0, 3, 0.06 : 1, 4, 0.06 : 1), suggesting the suitability of SDS medium for 2 to elicit exclusive extradiol cleavage. The TX-100 micellar medium also provides a suitable hydrophobic environment for 2 to elicit extradiol cleavage. However, in CTAB micellar medium, 2 shows cleavage selectivity lower than others. Also, the rate of dioxygenation is higher in SDS micellar medium than in DCM, and is dependent upon the chelate ring size.

A new route for the formation of Au nanowires and application of shape-selective Au nanoparticles in SERS studies

A new route for the formation of shape-selective Au nanoparticles (NPs) has been demonstrated. The reduction of Au(III) ions was done with alkaline 2,7-DHN in CTAB micellar media under 30 min of continuous UV-irradiation. The reaction results in uniform Au nanospheres and Au nanowires. With the change in Au(III) ion to CTAB molar ratio, the particles’ size and shape can be tuned. Au nanorods and nanoprisms are synthesized via seed mediated growth and microwave heating methods and the particles are characterized by several spectroscopic tools. The shape effects of the four different types of Au NPs were investigated using surface enhanced Raman scattering (SERS) studies. The results showed that the SERS intensity increases with the change in NPs’ shape from nanospheres to nanorods to nanowires to nanoprisms. The highest enhancement observed for the nanoprisms is due to the presence of a maximum number of sharp edges or surface active rough surfaces compared to the smooth surfaces of the nanospheres. This high enhancement factor (EF) of these multiple shaped Au NPs might find potential application in detection of single molecules or in many other fields like detection of bio-molecules, bioassays, bio-diagnosis or even clinical diagnostics and in medical therapy.

Shape-selective formation and characterization of catalytically active iridium nanoparticles

Iridium (Ir) nanoparticles (NPs) of variable shapes have been synthesized via the reduction of Ir(III) ions in CTAB micellar media containing alkaline 2,7-DHN under 4 h of UV-irradiation. The one-step process generates different shapes, such as nano-spheres, nano-chains, nano-flakes, and nano-needles. The synthesized Ir NPs are stable for more than a month in ambient conditions. The particles’ morphology can be tuned by simply changing the surfactant-to-metal ion molar ratios and altering other reaction parameters. The mechanisms of the Ir particle formation and effects of different reaction parameters were studied in detail. The Ir nano-needles serve as a good catalyst for the reduction of organic dye molecules in presence of NaBH 4. The catalysis rate was compared by considering the electron transfer process during the reduction of the dye molecules. The present method would lead to a quick process for the synthesis of other mono-metallic, composite, and semiconductor particles with variable shapes. The Ir NPs will find promising applications in different types of organic and inorganic catalysis reactions, nanoelectronics, and biomedical applications.

Formation and Catalytic Application of Electrically Conductive Pt Nanowires

Pt nanowires with variable lengths have been synthesized by the reduction of Pt(IV) ions using alkaline 2,7-DHN in CTAB micellar media under 3 h of UV photoirradiation. The synthesized Pt nanowires are stable for more than 3 months in ambient conditions. The particles’ morphology can be tuned by simply changing the surfactant-to-metal ion molar ratios and other reaction parameters. The mechanisms of the nanowire formation and effects of different reaction parameters are studied in detail. The resulting nanowires are found to be electrically conductive and maintain Ohm’s law with the electrodes. Moreover, they serve as a good catalyst for the reduction of organic dye molecules in the presence of NaBH4. The catalysis rate was compared by considering the electron-transfer process during reduction. The present method would lead to a quick process for the synthesis of other monometallic and composite nanowires with variable lengths. The Pt nanowires offer promising applications in different types of organic an...

Photoinduced Formation of Shape-Selective Pt Nanoparticles

A new synthetic route has been utilized for the formation of multiple-shaped Pt nanoparticles (NPs) under UV-photoirradiation. The one-step process exclusively generates different shapes, such as spheres, cubes, short and long wires, and flakelike nanostructures. The reduction of Pt(IV) ions was done using alkaline 2,7-DHN in CTAB micellar media under 3 h UV-photoirradiation. The synthesized Pt NPs are stable for more than 4 months in ambient conditions. By changing the surfactant-to-metal ion molar ratios and the concentration of reducing agent, the particle size and shape can be tuned. The mechanisms of the particles formation with variable shapes and the effects of different reaction parameters are studied in detail. The present approach can be extended to a fast synthetic method for the formation of other metallic and semiconductor particles with variable shapes. The evolved Pt NPs will find promising applications in different types of organic and inorganic catalysis reactions, medicinal applications, and nanoelectronics.

A quantitative structure property relationship for prediction of solubilization of hazardous compounds using GA-based MLR in CTAB micellar media

QSPR studies for estimating the incorporation organic hazardous compounds in cationic surfactant (CTAB) were developed by application of the structural descriptors and multiple linear regression (MLR) method. Various structure-related descriptors were studied in order to derive information on hydrophobic, electronic and steric properties of solute molecules. Theoretical molecular descriptors selected by genetic algorithms-procedure were followed to predict log K s values by a stepwise-MLR method. A simple model with low standard errors and high correlation coefficients was selected. It was also found that MLR method could model the relationship between solubility and structural descriptors perfectly. The proposed methodology was validated using full cross validation and external validation using division of the available data set into training and test sets. The squared regression coefficient of prediction for the MLR model was 0.9624. The results illustrated that the linear techniques such as MLR combined with a successful variable selection procedure are capable to generate an efficient QSPR model for predicting the solubility of different compounds. The proposed model can be used adequately for the prediction and description of the solubility of organic compounds in micellar solutions.

Potential application of synchronous fluorescence spectroscopy to determine benzo[ a]pyrene in soil extracts

Benzo[ a]pyrene (BaP) is a significant environmental pollutant and rapid, accurate methods to quantify this compound in soil for both research and environmental investigation purposes are required. In this work, solvent extracts from five contrasting soils spiked with four different polycyclic aromatic hydrocarbons (PAHs) were rapidly analysed by using a synchronous fluorescence spectroscopy (SFS) method. The SFS method was validated using HPLC with ultraviolet detection. A good correlation for the quantification of BaP in soil extracts by the two methods was observed. The detection limit of the SFS method was 1.6 × 10 −9 g/ml in CTAB micellar medium (7.8 mmol/l). The work demonstrates that SFS has potential as a sensitive, accurate, rapid, simple and economic methodology and an efficient alternative to HPLC for fast confirmation and quantification of BaP in complex soil extracts.

Simple luminescence method for estimation of benzo[a]pyrene in a complex mixture of polycyclic aromatic hydrocarbons without a pre‐separation procedure

Benzo[a]pyrene causes cancer at cellular level and is widely present in the environment. Conventional spectroscopic methods for analysis of this compound need a pre-separation procedure due to severe spectral overlap from other polycyclic aromatic hydrocarbons. We report a simple method that avoids spectral overlap of benzo[a]pyrene from other impurities or polycyclic aromatic hydrocarbons (PAHs), thus it can easily identify benzo[a]pyrene in a complex PAH mixture. The method could easily identify benzo[a]pyrene in an 18-component PAH mixture. Calibration plots in methanol solution and in micellar media show a good linearity (R > 0.9997) in the benzo[a]pyrene concentration range generally found in the environment. The method gives a detection limit of 1.52 x 10(-9) mol/L in CTAB micellar medium and 2.55 x 10(-9) mol/L in methanol solution. The proposed method is selective, sensitive and fast. The fluorescence response of benzo[a]pyrene is found to be a potential candidate to sense the critical micellar concentration (CMC) of CTAB micelles.

Micellar effect on the scavenging of singlet molecular oxygen by hydroxybenzenes

The antioxidative effectiveness of three hydroxyaromatic derivatives (OHAD), namely phenol, resorcinol and phloroglucinol, as reflected by their scavenging ability of the photochemically generated species singlet molecular oxygen [O2(1Δg)], was studied in aqueous solution and micellar media. Kinetic results, obtained through time-resolved phosphorescence detection of O2(1Δg) emission and polarographic methods, at pH 7 and 12 in homogeneous and CTAB micellar media, were compared. Calculated photooxidation quantum efficiencies (φr), ranging from very low values (~0.01) to relatively high ones (~0.3), depend on the preferential solubilization sites of the hydroxyaromatic derivatives either in the micellar or homogeneous media. OHAD in water pH 7 and in CTAB 0.02 M pH 12 exhibit their highest antioxidative efficiency as O2(1Δg) scavengers. In these conditions, they present the best degree of self protection against O2(1Δg)-mediated photooxidation with relatively high values for the overall quenching rate constant and, simultaneously, the lowest φr.