G. V. Mel'nikov

Fluorimetric and conductometric study of water—n-octane—sodium dodecyl sulfate—n-pentanol microemulsions

The influence of the water concentration in the water—n-octane—sodium dodecyl sulfate—n-pentanol microemulsions on the polarity index I1/I3, the efficiency of formation of the fluorescent probe (pyrene) excimers Iex/Im, and the conductivity of the system in a wide interval of water—oil ratios was studied. Analysis of changes in the polarity index shows that in all types of the microemulsions pyrene is solubilized in the hydrophobic part of the water—oil interface between the surfactant hydrocarbon radicals. Depending on the water—oil ratio, the site of its localization changes, and the effective permittivity of the medium εeff varies from 5 to 11. Variations of the conductivity and polarity index allow one to observe three structures in the mucroemulsion, viz., water—oil, bicontinual region, and oil—water. Variation of the Iex/Im ratio reveals only the transition from the water—oil microemulsion to the oil—water microemulsion.

Pyrene sensitized phosphorescence enhanced by the heavey atom effect in the water-heptane-sodium dodecyl sulfate-pentanol microemulsion

The influence of the external TI+ “heavy” ion on the singlet and triplet excited states of the pyrene and Trypaflavine molecules solubilized in the water-heptane-sodium dodecyl sulfate-pentanol microemulsion was studied. The triplet-triplet (T-T) energy transfer in the system Trypaflavine (donor)-pyrene (acceptor) and the sensitized phosphorescence of pyrene were first observed in the microemulsion containg Tl+ ions. The quenching rate constants of the excited states of the luminophores by Tl+ ions were calculated.

Spectral studies of polycyclic aromatic hydrocarbon interaction with human blood plasma

Analysis of fluorescence spectra of polycyclic aromatic hydrocarbons in human blood plasma and human serum albumin solution allowed one to conclude that pyrene and also anthracene are predominantly distributed in the hydrophobic micro-phase of blood plasma proteins. In the solution of human blood plasma containing pyrene the nonmonotonic dependence of both the intensity of pyrene fluorescence and the index of polarity on the concentration of sodium dodecylsulfate added was observed. This should be connected with the reconstruction of the structure of protein globule under the surfactant action and cannot be explained only by the solubilization of pyrene in sodium dodecylsulfate micelles.

Luminescent probe in the study of surfactant-induced structural changes in serum albumin in human blood plasma

The luminescence-kinetic technique of the monitoring of structural changes in albumins of human blood plasma that uses a luminescent probe-eosin is proposed. Phosphorescence of eosin bound to the globular proteins of blood plasma-albumins was recorded at room temperature. It is found that under the action of sodium dodecylsulfate on the albumins the rate constant of eosin phosphorescence decay grows and the intensity of eosin phosphorescence decreases. It is assumed that these changes are connected with the denaturing of blood plasma albumins by sodium dodecylsulfate.

Determination of the Constants of Binding of Acridine Dyes with Micelles of Sodium Dodecyl Sulfate Using the Quenching of Delayed Fluorescence by Heavy Atoms

The constants of binding dye molecules with the micelles of sodium dodecyl sulfate are determined using quenching of delayed fluorescence of acridine dyes by sodium iodide in aqueous–micellar solutions. Kinetic equations have been composed that describe the processes of deactivation of the excited states of dyes. By solving these equations at the concentration of the quencher sodium iodide corresponding to the minimum lifetime of triplet states and at the concentration of micelles corresponding to the least value of the delayed fluorescence quenching rate constants, we obtained the constants of binding dyes with micelles equal to 1.3·107, 2.9·107, and 3.1·107 M−1 for trypaflavine, acridine orange, and acridine yellow, respectively. We calculated the rate constants of quenching of the triplet states of the molecules of dyes by iodide ions (I−) that decreased in transition from trypaflavine to acridine orange and acridine yellow.

PHOSPHORESCENCE OF MOLECULES OF POLYCYCLIC AROMATIC HYDROCARBONS IN AQUEOUS MICELLAR SOLUTIONS OF SODIUM DODECYLSULFATE AT ROOM TEMPERATURE

Deactivation of the excited states of pyrene, benzanthracene, and fluorene molecules in aqueous micellar solutions of sodium dodecylsufate is studied using steady and pulsed fluorimetry. Quenching of the singlet states of polyatomic hydrocarbons by thallium ions is considered. Effective, micellar, and biomolecular constants for the quenching rate are obtained. Phosphorescence constants for the aforementioned compounds are determined. Reasons behind the possibility of observing phosphorescence of polyaromatic compounds in micellar solutions at room temperature are ascertained.

Spectral luminescence studies of eosin solvation in water-alcohol mixtures

The authors investigate the effects of solvation of eosin molecules in binary water-propanol mixtures with the goal of assessing eosin as a candidate dye laser material. The fluorescence was measured with a Hitachi spectrofluorimeter and the absorption spectra were taken on a Specord spectrophotometer. Absorption and fluorescence were measured for different amounts of propanol in the solvent. Data are also given on excitation and de-excitation kinetics between ground and excited states. Values for quantum yields of fluorescence and phosphorescence, average excited state lifetime, and molecular volume of the dye with the solvated shell are tabulated.