Nonionic Micellar Media Research Articles

Speciation study involving mononuclear binary transition metal (CoII, NiII and CuII) complexes of L-methionine in non-ionic micellar medium

The present work aims to evaluate the binding capacities of binary complexes of L-Methionine with transition metal ions CoII, NiII and CuII in Triton X 100-water mixtures, a non-ionic micellar media of different compositions (0.0–2.5% (v/v)), investigated under the experimental conditions of 0.16 mol/dm3 ionic strength using NaNO3 at a temperature of 303.0 ± 0.1 K Potentiometrically. The potentiometric data was assessed by Irving-Rossotti pH metric technique with the least-squares method of MINIQUAD75, a computer program. The selectivity of the best fit model obtained by continuous exhaustive chemical modelling studies and the accuracy of the results is assessed based on statistical parameters. MLH, ML and ML2 are the identified species for the three M(CoII, NiII and CuII) - Met systems. The shift in the equilibrium of binary metal-methionine complexes with variation in composition (0.0–2.5%) of the solvent can be explained by electrostatic together with non-electrostatic forces contributed by the interaction of solute with solvent.

Biomimetic systems trigger a benzothiazole based molecular switch to 'turn on' fluorescence.

Molecular switches are valuable tools for the detection of many chemical and biological processes. On the other hand, Schiff bases are known for their simplicity in synthesis and their enormous biochemical applications. In this scenario, when a strategically designed Schiff base acts as a molecular switch in biomimetic environments drags inevitable attention. In this article, we hereby demonstrate an interesting behavior of a strategically designed bioactive benzothiazole based Schiff base (E)-2-(((6-chlorobenzo[d]thiazol-2-ylimino)methyl)-5-diethylamino) phenol (CBMDP) whose fluorescence characteristics dramatically modulate as consequence of its structural modification in aqueous and biomimetic environments individually. Electronic absorption, steady state and time resolved fluorescence spectroscopic techniques along with DFT based quantum chemical calculation evidence that in pure organic solvents CBMDP exists in highly fluorescent enol-imine (N) form which transform into feebly fluorescent hydrated species (H) in bulk aqueous media. Contrariwise, on interaction with the ionic and non-ionic micellar media or with liposome, a structural restoration occurs from less fluorescent hydrated (H) species into a highly fluorescent normal (N) one. This molecular flipping of the title compound upon micellar compartmentalization is possibly caused by the micropolarity of the local environment and further supported by its spectral behavior in different polarity gradient solvent mixture of water-dioxane (protic-aprotic) and water-methanol (protic -protic). Usually, Schiff bases are prone to hydrolysis in aqueous media, interestingly, the structural framework of this strategically designed molecule only allow the first step of hydrolysis, which is hydration of azomethine linkage whereas it withstand the second step, and that possibly helps the structural restoration process. Hence the article described herein may emphasize how a systematically designed Schiff base framework can be used as 'turn off- turn on' fluorescent molecular switch which may be extremely useful for its applications in the area of biochemical sensors.

Activity of α‐Chymotrypsin in Cationic and Nonionic Micellar Media: Ultraviolet and Fluorescence Spectroscopic Approach

ABSTRACTα‐Chymotrypsin (α‐CT) activity was measured in aqueous buffer with the following alkyltriphenylphosphonium bromide surfactants in the series cetyl, tetradecyl, and dodecyl as a tail length. For the sake of comparison with mixed micellar investigation on activity of α‐CT, cationic cetyltriphenylphosphonium bromide (CTPB) and nonionic surfactant Triton X‐100, Brij‐56, Brij‐35, Tween 20, and Igepal Co‐210 have been used. The p‐nitrophenyl acetate (PNPA) hydrolysis rate was determined at the surfactant concentration of both cationic and mixed micellar systems by a UV–vis spectrophotometer. The catalytic reaction follows the Michaelis–Menten mechanism, and the catalytic efficiency (kcat/KM) was evaluated for both homogeneous and mixed‐micellar media. The maximum catalytic efficiency was observed at 5 mM concentration of CTPB, but the highest catalytic efficiency, 572 M−1 s−1, was measured in the presence of mixed micellar (7.5 mM CTPB + 2.5 mM Tween‐20). The fluorescence (FL) spectra showed the differences of α‐CT conformations in the presence of cationic surfactants. The FL results suggest that the influence of cationic surfactant on proteolysis arises from the interaction with the α‐CT. The binding constant, ksv, of α‐CT with cationic aggregates was determined in the buffer using the Stern–Volmer equation by the fluorescence spectroscopic approach.

Interaction of antihypertensive drug amiloride with metal ions in micellar medium using fluorescence spectroscopy

Steady state and life time fluorescence spectroscopy have been employed to study the interaction of antihypertensive drug amiloride with biologically important metal ions i.e. Cu2+, Fe2+, Ni2+ and Zn2+ in various micellar media (anionic SDS (sodium dodecyl sulfate), nonionic TX-100 (triton X-100) and cationic CTAB (cetyl trimethyl ammonium bromide)). It was observed that fluorescence properties of drug remain unaltered in the absence of micellar media with increasing concentration of metal ions. However, addition of Cu2+, Fe2+ and Ni2+ caused fluorescence quenching of amiloride in the presence of anionic micelle, SDS. Binding of drug with metal ions at the charged micellar interface could be the possible reason for this pH-dependent metal-mediated fluorescence quenching. There were no remarkable changes observed due to metal ions addition when drug was present in cationic and nonionic micellar medium. The binding constant and bimolecular quenching constant were evaluated and compared for the drug–metal complexes using Stern–Volmer equation and fluorescence lifetime values.

Photoinduced electron transfer reactions of ruthenium(II) phenanthroline complexes with dimethylaniline in aqueous and micellar media.

Four [Ru(NN)(3)](2+) complexes (NN = polypyridine) with ligands of varying hydrophobicity with different charges +2, 0 and -4 were synthesized. The photophysics and photoinduced electron transfer reactions of these Ru(II)-complexes with dimethylaniline (DMA) as the quencher have been studied in aqueous medium and ionic and non-ionic micellar medium. The extent of binding of the complexes with the surfactant interface is evident from the calculated binding constant values (K). Dimethylaniline (DMA) being a neutral quencher, the hydrophobic and electrostatic interactions competing with one another and their combined effect with the surfactants were reported by observing the quenching rate constant (k(q)) values. The formation of anilinium cation radical in transient absorption spectrum confirms the excited state electron transfer reactions of ruthenium(II) complexes with dimethylaniline. The calculated rate constant values (k(q)) are in good agreement with the experimental k(q) values giving quantitative evidence for the bimolecular reductive quenching rate constant for the complexes with DMA. Pseudophase ion exchange model is successfully applied to analyse the quenching data.

Fluorophotometric Determination of Histone with 3,4,5,6-Tetrafluoro-2-carboxyphenylfluorone–Manganese(II) Complex and Its Characterization

A simple fluorophotometric method for the determination of histone has been developed. This method involves a fluorescence quenching reaction that results in the formation of a complex of manganese(II), 3,4,5,6-tetrafluoro-2-carboxyphenylfluorone (TFCPF), and histone in a non-ionic surfactant micellar medium. The calibration curve was found to be linear in the range of 0.5 to 2.0 µg/mL. The binding parameters (n, number of binding sites; K, binding constant) and thermodynamic parameters (ΔG(0), change in Gibbs free energy; ΔH(0), change in enthalpy; ΔS(0), change in entropy) were investigated spectrophotometrically for the elucidation of the reaction mechanism. The resulting binding parameters (n=4.08 and K=3.16×10(4) m(-1) at 25°C) and thermodynamic parameters (ΔG=-25.83 kJ/mol, ΔH=-9.83 kJ/mol, and ΔS=53.68 J/(mol K)) suggest that the colored complex in this reaction system is an ion-association complex between manganese(II)-TFCPF and histone.

Protonation and Complexation Equilibria of l-Glutamine in Non-ionic Micellar Medium

Protonation equilibria of l-glutamine and speciation of its complexes with Co(II), Ni(II) and Cu(II) have been studied pH-metrically in 0–2.5 % v/v triton X-100 solution maintaining an ionic strength of 0.16 mol l−1 at 303 K. The protonation constants and binary stability constants have been calculated with the computer program MINIQUAD75. Best fit chemical models have been selected based on standard deviation in stability constants and residual analysis using crystallographic R-factor and sum of squares of residuals in all mass-balance equations. The trend in the variation of stability constants of the complexes with mole fraction of the medium is attributed to the compartmentalization of complexation equilibria. Distribution of species and effect of influential parameters on chemical speciation have also been presented.

The effects of micellar media on the photocatalytic H 2 production from water

The photocatalytic H 2 production efficiency of a multi-component system, containing [Ir(ppy) 2(bpy)] + as photosensitizer, [Co(bpy) 3] 2+ as H 2-evolving catalyst, and triethanolamine (TEOA) as sacrificial electron donor, was investigated in water/acetonitrile (8:2, v/v) solution in the presence of different kinds of surfactants, such as cetyl trimethyl ammonium bromide (CTAB), Triton X-100, and sodium lauryl sulfonate (NaLS). The H 2 evolution rate is found to follow the order of cationic micellar media > nonionic micellar media > anionic micellar media > water/acetonitrile solution. The underlying mechanism was discussed.

Integration of vanadium-mixed addenda Dawson heteropolytungstate within poly(3,4-ethylenedioxythiophene) and poly(2,2′-bithiophene) films by electrodeposition from the nonionic micellar aqueous medium

A comparative study describing immobilization of the Dawson type mixed addenda heteropolyanion, [P 2W 17VO 62] 8− into conducting polymer films of poly(3,4-ethylenedioxythiophene), PEDOT, and poly(2,2′-bithiophene), PBT, is reported. Electrosynthesis of these hybrid films was performed using a micellar aqueous solution of the nonionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-100). Deposited composite films were characterised electrochemically and, on the whole, they exhibited fast electron transfer (ET) properties and relatively high stability towards continuous potential cycling in acidic media. In particular, PEDOT composite showed relatively faster ET properties in comparison to PBT composite. Their permeability was investigated in the presence of cationic and anionic redox probes. Our results implied good mediating capabilities of the [P 2W 17V 4+O 62] 8− anion (within the [P 2W 17V 4+O 62] 8−–PEDOT hybrid film) towards the iron (III) reduction. The specific electrocatalytic (reductive) capabilities of hybrid films were also studied by probing the reduction of bromate. The films were further characterised by X-ray photoelectron spectroscopy to establish their interfacial elemental composition. Moreover, their surface morphology was imaged by atomic force microscopy and scanning electron microscopy. Results have shown that physicochemical properties of the investigated hybrid films were affected by polymer hydrophobicity.

Complexation of Cu(II) by Original Tartaric Acid−Based Ligands in Nonionic Micellar Media: Thermodynamic Study and Applications

The complexation of Cu(II) with original alkylamidotartaric acids (C(x)T) is investigated in homogeneous aqueous medium and in the presence of nonionic micelles of Brij 58 (C16EO20), thanks to various analytical techniques such as NMR self-diffusion experiments, CD and UV-vis spectroscopy, ESI mass spectrometry, pHmetry and micellar-enhanced ultrafiltration (MEUF). First, a complete speciation study proves the formation of dimeric complexes in water and provides their formation constants. Second, a similar study is led in the presence of nonionic micelles. It underlines a modification of the apparent equilibrium constants in micellar medium and demonstrates that the structure of the complexes is slightly modified in the presence of micelles. This thermodynamic and structural study is applied to modelize the evolution of the extraction yields of Cu(II) by the micelles as a function of pH and to identify the complexes extracted in the micelles. The effects of the chain length of the ligand (C3T vs C8T) on the solubilization properties are put into relief and discussed. Anionic species are proved to be more incorporated in the nonionic micelles than the cationic species. The extracting system constituted of octylamidotartaric acid (CsT) solubilized in nonionic micelles of Brij 58 is demonstrated to be very efficient for the extraction of Cu(II) by MEUF, this technique being an interesting green alternative to traditional solvent extraction.

Speciation of binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) with L-aspartic acid in anionic, cationic and neutral micellar medium

Chemical speciation of binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) with L-aspartic acid was investigated pH-metrically in (0.5–2.5%) anionic, cationic and neutral micellar media. The stability constants were calculated using the computer program MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The models for the binary species contained MLH, ML2 and ML2H for Co(II), ML, MLH, ML2 for Ni(II) and Cu(II), ML2,ML2H and ML2H2 for Zn(II) in anionic, cationic and nonionic micellar media The trend in variation of stability constants with change in the mole fraction of the medium was explained on the basis of electrostatic and non-electrostatic forces. Distributions of the species with pH at different composition of micellar media were also presented.

Selective Reduction of Isophorone in Micellar Media

Reduction of isophorone with sodium borohydride is studied in anionic, cationic, and nonionic micellar media. Ionic micelles are found to be selective toward 1,4 products. The selectivity ratio of 1,4/1,2 products was found to increase from 0.75 to 1.6 in the presence of anionic micelles of SDS, and in the presence of cationic micelles of CTAB it increased up to 1.5. The two-phase reaction takes place in the kinetically controlled regime. The volumetric rate of the reaction increases with an increase in SDS concentration. The change in selectivity is mainly attributed to the orientation of isophorone in the micellar media, while the increase in reaction rate is attributed to increased solubility in the micellar solution.

Spectrophotometric Determination of Anthracycline Anticancer Agents with Aluminum(III) and Chromazurol S in a Nonionic Surfactant Micellar Medium

A simple and highly sensitive spectrophotometric method for the determination of anthracycline anticancer agents, such as Daunorubicin hydrochloride (DAU), was established by using aluminum(III) and Chromazurol S (CAS) in a nonionic surfactant micellar medium. In the case of determination of DAU, the apparent molar absorptivity was 1.3 x 10(5) dm3 mol(-1) cm(-1) at 615 nm. Beer's law was obeyed in the concentration range of 0.028 - 2.82 microg ml(-1) for DAU. Owing to no need for solvent extraction, this method could be applied to assays of DAU and related drugs in pharmaceutical preparations.

Effect of surfactants on the dissociation constants of ascorbic and maleic acids

The dissociation equilibria of ascorbic and maleic acids have been studied in certain cationic, anionic and non-ionic micellar media and their p K a values have been evaluated by the potentiometric, conductometric and spectrophotometric techniques. These p K a values have been found to shift in micellar media as compared to those in pure water. The differences in the values have been attributed to the solvent properties of the interfacial and bulk phases involving contribution from the micellar surface potential in the case of charged micelles. The values of the limiting molar conductance of the acids have been determined in the various surfactants and were found to be different in different surfactants. In case of the cationic surfactants the limiting molar conductance was found to increase with increase in surfactant concentration.

Effect of the Media on the Quantum Yield of Singlet Oxygen (O2(1Δg)) Production by 9H‐Fluoren‐9‐one: Microheterogeneous Systems

AbstractThe quantum yield (ΦΔ) of singlet oxygen (O2(1Δg) production by 9H‐fluoren‐9‐one (FLU) is very sensitive to the nature of the solvent (0.02 in a highly polar and protic solvent, such as MeOH, to 1.0 in apolar solvents). This high sensitivity has been used for probing the interaction of FLU with micellar media and microemulsions based on anionic (sodium dodecyl sulfate, SDS; bis‐(2‐ethylhexyl)sodium sulfosuccinate, AOT), cationic (cetyltrimethylammonium chloride, CTAC) and nonionic (Triton X‐100, TX) surfactants. Values of ΦΔ of FLU vary in a wide range (0.05–1.0) in both microheterogeneous media and neat solvent, and provide information on the microenvironment of FLU, i.e., on its localization within organized media. In ionic and nonionic micellar media, as well as in four‐component microemulsions, FLU is, to various extents, exposed to solvation by the polar and protic components of the microheterogeneous systems (water and/or butan‐1‐ol) in the micellar interfacial region (ΦΔ=0.05–0.30). In contrast, in AOT reverse micelles (consisting of AOT as surfactant, cyclohexane as hydrophobic component, and water), FLU is located in the hydrophobic continuous pseudophase, and is totally separated from the micellar water pools (ΦΔ≈1.0).

Fluorescence lifetime and quantum yield of TMPyPH 2 associated with micelles and DNA

In this work, we have determined the fluorescence lifetime and quantum yield of meso-tetrakis (4- N-methylpyridyl)porphine (TMPyPH 2) in cationic, anionic and non-ionic micellar media and in buffer phosphate solutions of DNA in order to evaluate how their electrostatic domain affects the photophysical properties of TMPyPH 2. The results obtained indicated that each specific electrostatic domain in micellar medium and in DNA solution affect the photophysical properties of the porphyrin. In anionic micellar medium of sodium dodecylsulfate (SDS) the electrostatic interacting of TMPyPH 2 with the medium leads to a Φ f value higher and τ f longer than those obtained in cationic medium of cetyltrimethylammonium bromide (CTAB) micelles. The interaction of TMPyPH 2 with a biological staff as DNA results initially in two different populations of a complex DNA–TMPyPH 2. The τ 1 for the first complex species changes in the function of DNA concentration in the ranges from 5.25 (‘free’ porphyrin species) to 11.3 ns (‘completely bound’ species) and the τ 2 for the second complex remains constant around 3 ns. It also was observed that DNA binding leads to a reduction in the fluorescence quantum yield of TMPyPH 2 to all DNA concentrations. This is an indication that the photodynamic properties of this porphyrin interacting with DNA are susceptible to the environmental properties affecting directly their photodynamic action.

Micelle induced generation of photovoltage using Fluorescein dye

Photovoltage generation using Fluorescein dye in aqueous and aqueous-micellar medium at different pH has been studied in photogalvanic cell. The photopotential and photocurrent generated were maximum in non-ionic micellar medium. The observed solar energy efficiency in non-ionic micellar medium, diethylene glycol hexadecyl ether (Brij-52) was 0.06% and maximum power of the cell was 15.5 μw. The output of the cell was sensitive to surfactant nature. The rate constants of the reactions during photovoltage growth and decay were calculated. The thermodynamic properties of the cell were also discussed. A comparison of the micelle induced photovoltage generation of anionic dye Fluorescein with cationic dye Safranine T in different micellar media and at different pH has been presented.

2-Methyl Naphthalene as Fluorescence Probe in Ionic and Nonionic Micelles: Fluorescence Quenching by Halides

The fluorescence characteristics of 2-methyl naphthalene have been studied in ionic micelles of sodium dodecyl sulphate (SDS) and cetyl trimethyl ammonium bromide (CTAB) and in nonionic micellar medium of p-t-octylphenyl polyethoxyethanol (Triton X-100). The fluorescence quenching of fluorophore by halides and pseudohalide obeys the Stern-Volmer Equation up to a certain concentration of quencher. A quenching sphere of action model has been considered to explain the deviations from Stern-Volmer behaviour. The distribution of quenchers in the micellar phase has been calculated.

Kinetic spectrophotometric determination of traces of sulfide in nonionic micellar medium.

A sensitive kinetic spectrophotometric method for the determination of ng amounts of sulfide has been developed based on the reduction of Azure A by sulfide in the presence of Brij-35 at pH 7. The decrease in absorbance of Azure A at 600 nm is proportional to the concentration of sulfide over the range 25-1,400 ng mL(-1). The variables affecting the rate of the reaction were investigated and the optimum conditions were established. The method is simple, rapid, precise, sensitive, and widely applicable. The limit of detection is 17 ng mL(-1), and the relative standard deviation of seven determinations of 500 ng mL(-1) sulfide was 2.1%. The method was applied to the determination of sulfide in spring water.

Determination of trace amounts of beryllium using derivative spectrophotometry in non-ionic micellar medium

A rapid and sensitive method for the trace level determination of beryllium based on the formation of a 1:2 complex ( λ max 560 nm) with 1,4-dihydroxy-9,10-anthracenedione in an aqueous medium containing Triton X-100 is reported. Beer’s law is followed in the range 3.60–360 ng ml −1 of Be(II). The molar absorptivity and Sandell’s sensitivity are 1.68×10 4 l mol −1cm −1 and 0.54 ng cm −2, respectively; detection limit is 0.23 ng ml −1 of Be(II). Analysis of synthetic mixtures of composition similar to that of alloys and spiked samples of distilled water, gave results that are in agreement with their beryllium content.