Subhash C. Bhattacharya

Quenching of fluorescence of 2-anthracene sulphonate by cetylpyridinium chloride in micellar solutions of Tweens, Triton X-100, sodium dodecylsulphate (SDS) and cetyltrimethylammonium bromide (CTAB)

Abstract The results of the fluorescence quenching of 2-anthracene sulphonate by cetylpyridinium chloride in ionic and non-ionic micellar environments are presented. The static quenching process (lifetime, 4.5 ns) was exploited to estimate the bimolecular quenching rate constants and binding constants between the probe and the quencher from the Stern—Volmer equation, the aggregation number of the surfactant micelles, and the occupancy number of the quencher in the micelle and the binding constant of the quencher with the micelle from the Encinas—Lissi equation. Both ionic and non-ionic micelles, i.e. cetyltrimethylammonium bromide, sodium dodecylsulphate, Triton X-100, Tween-20, Tween-40, Tween-60 and Tween-80, were employed. In the Tween series (Tween-20 to Tween- 80), the micellar aggregation numbers systematically varied. The average occupancy number of the quencher in the micelle and the binding constant of the quencher with the micelle showed a linear correlation with the aggregation number of the micelles.

Visible and fluorescence spectral studies on the interaction of safranine T with surfactant micelles

Abstract The visible spectra of safranine T in micellar solutions indicate 1:1 (dye to micelle) charge transfer complex formation with the non-ionic surfactants Triton X 100 (TX 100), Tween 20, Tween 40, Tween 60 and Tween 80 as well as with the anionic surfactant sodium dodecyl sulphate (SDS). The non-ionic surfactant micelles show stronger interaction than the ionic micelle SDS, the complexing strengths of the non-ionic micelles following the order Tween 80>Tween 60>TX 100>Tween 40>Tween 20. The fluorescence spectrum of the dye is also affected (intensified) by the surfactant micelles. The results confirm a 1:1 complex and comparable complexing strengths (except the position of TX 100) as revealed by the ground state spectra. Thermodynamic analysis shows that the increased stability of the dye—micelle complex is associated with a systematic increase in exothermic enthalpy and decrease in entropy which compensate each other. The equilibrium constants of the dye—micelle complex are directly proportional to the carbon numbers of the Tweens and inversely proportional to the critical micelle concentration (CMC) of the surfactants.

Effect of Ethylene Glycol on the Thermodynamic and Micellar Properties of Tween 40, 60, and 80

The self‐aggregation of Tween 40, Tween 60, and Tween 80 in ethylene glycol‐water mixture was investigated using surface tension, density, and fluorescence measurements. The mixtures were observed to appreciably affect the critical micelle concentration (cmc) of the surfactants and their aggregation numbers. In order to evaluate the influence of the solvent mixture, the difference in the Gibbs energy of micellization of Tween 40, Tween 60, and Tween 80 between water and binary mixtures were determined. The ability of ethylene glycol acting as a structure breaker and its interaction with the surfactant hydrophilic group are the controlling factors for the micellization of the surfactants in the mixture. The surface activity of the surfactants decreases with increasing concentration of ethylene glycol in the mixture. Micellar micropolarity was determined using the fluorescence method. The results indicate the participation by ethylene glycol in the micellar solvation layer.

Spectroscopic studies of the interaction of the dye safranine T with Brij micelles in aqueous medium

Abstract The visible spectra of safranine T (ST) in micellar solutions of Brij 52, Brij 56 and Brij 58 indicate 1 : 1 charge transfer complex formation of ST with non-ionic Brij micelles. The complexing strength follows the order Brij 52 > Brij 56 > Brij 58. The fluorescence spectra of ST in micellar solutions of Brij also support 1 : 1 ST-micelle complex formation as in the ground state. The equilibrium constant of the dye—micelle complex is directly proportional to the micellar aggregation number and inversely proportional to the surfactant critical micellar concentration (CMC). The solvent parameters, i.e. the Kosower Z value, intramolecular charge transfer energy E T 30 and dielectric constant of the micellar medium, were evaluated. The binding constant, micellar aggregation number and solvent parameters remain constant over a certain range of Brij concentration, but vary beyond this range.

Effects of solvent and micellar enviroment on the spectroscopic behavior of the dye safranine T

Abstract The photophysical (visible and fluorescence) behavior of the dye safranine T has been studied in several polar and non-polar solvents and in micellar solution (non-ionic and ionic surfactants). The change in the dipole moment of the dye between the ground and excited states has been estimated using approximate sovent-induced spectral shift (Stokes shift) theories based on non-specific interactions. The dependence of the dye behaviour on the nature of the micellar interface is shown by the Strokes shift which exhibits an inverse dependence on the average aggregation number of the surfactant micelles. A reasonables estimation of the dielectric constant of the micellar interface has been attempted.

Physicochemistry of Interaction between the Cationic Polymer Poly(diallyldimethylammonium chloride) and the Anionic Surfactants Sodium Dodecyl Sulfate, Sodium Dodecylbenzenesulfonate, and Sodium N-Dodecanoylsarcosinate in Water and Isopropyl Alcohol−Water Media

The physicochemistry of interaction of the cationic polymer poly(diallyldimethylammonium chloride) (PDADMAC) with the anionic surfactants sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and sodium N-dodecanoylsarcosinate was studied in detail using tensiometry, turbidimetry, calorimetry, viscometry, dynamic light scattering (DLS), and scanning electron microscopy (SEM). Fair interaction initially formed induced small micelles of the surfactants and later on produced free normal micelles in solution. The interaction process yielded coacervates that initially grew by aggregation in the aqueous medium and disintegrated into smaller species at higher surfactant concentration. The phenomena observed were affected by the presence of isopropyl alcohol (IP) in the medium. The hydrodynamic sizes of the dispersed polymer and its surfactant-interacted species were determined by DLS measurements. The surface morphologies of the solvent-removed PDADMAC and its surfactant-interacted complexes from water and IP-water media were examined by the SEM technique. The morphologies witnessed different patterns depending on the composition and the solvent environment. The head groups of the dodecyl chain containing surfactants made differences in the interaction process.

The surfactant concentration-dependent behaviour of safranine T in Tween (20, 40, 60, 80) and Triton X-100 micellar media

Abstract The visible and fluorescence spectra of the dye safranine T were studied in micellar solutions of non-ionic surfactants in different concentration ranges. The complexing strengths (1 : 1 dye : micelle charge transfer complex formed between the dye and micelle) of the non-ionic micelles increase with increasing concentration of the surfactant in the micellar solution. The aggregation number and several solvent parameterss, i.e. the Kosower z value, intramolecular charge transfer energy E T 30 , dielectric constant of the micellar medium and viscosity of the micellar solution, were evaluated. These values remain constant over certain concentration ranges, but vary in different concentration regions of a surfactant.

Spectroscopic behaviour of the dye safranine T in aqueous polyethylene glycol medium

The interaction of the dye safranine T (ST) in the ground and excited states with polyethylene glycols (PEGs) of five different molar masses was studied. The binding parameters of the combinations were estimated in terms of Langmuir and Scatchard equations. The spectroscopic study has enabled the solvent parameters of the aqueous PEG media to be estimated by comparison with such parameters for pure solvents.

Quenching fluorescence of Safranine T by inorganic ions in aqueous and non-ionic micellar media

The fluorescence quenching of Safranine T by [Fe(CN)6]3−, [Fe(CN)6]4−, Fe2+, Co2+, Cu2+, Ni2+ and Mn2+ was studied in aqueous solutions as well as in solutions of non-ionic micelles of Triton X-100 and Tweens (20, 40, 60, and 80). The rate constant of quenching were calculated using the Stern-Volmer equation. In a micellar medium, the quenching efficiency is less compared with that in an aqueous medium. It has been established that the quenching phenomenon is not affected by the transfer of electrons from the quencher to the dye molecule, and that collisional plays the main role in this photochemical process.

Physicochemical studies on the micellization behavior of cetylpyridinium chloride and triton X-100 binary mixtures in aqueous medium

Physicochemistry of micellization of binary mixtures of cetylpyridinium chloride (CPC) and Triton X-100 (TX-100) have been investigated and the data collected have been analyzed and correlated. Tensiometric, conductometric, spectrophotometric, calorimetric and polarographic methods have been employed in the study. Parameters like critical micellar concentration (CMC), counter-ion binding, energetics of micellization, interfacial surfactant adsorption and minimum area of amphiphile head groups at CMC have been determined. The diffusion coefficients of pure and mixed micelles in solution have been determined by the polarographic method. The regular solution theory of Rubingh has been considered to get information on the micellar composition and their mutual interaction (synergistic for the studied system) in solution. The packing of the monomer in micelle has been estimated to witness spherical geometry for CPC and its mixtures with TX-100, whereas the later has been found to be spheroidal. Polarographic measurements have evidenced comparable diffusion coefficients of CPC and TX-100 micelles whereas their mixed micelles have shown lower values with a minimum, at equimolar composition.