We studied the absorption and fluorescence spectra of a rhodamine 6G-activated gelatin film of thickness 10 μm, with and without silver nanoparticles. We observed that doping the film with nanoparticles of diameter 5 nm leads to an increase in the intensity of the absorption spectrum by a factor of 1.17 and its short-wavelength shift (~1.5 nm), while the intensity of the fluorescence spectrum increases by a factor of ~2.

We have investigated structural changes of human erythrocyte membranes under the action of interference light fields with different periods of spatial modulation. A local polarity in the surface regions of membranes was detected by means of the fluorescent probe method using stationary and time-resolved fluorescence spectroscopy. The electro-dipolar molecules 4'-diethylamino (FET) and 4'-N-(15-azacrown-5) (FCR) derivatives of 3-hydroxyflavone with coupled intramolecular charge and proton transfers were used as fluorescent probes. The FET molecules locate deeper in the membrane than FCR probes. It was established that the micropolarity of probes binding sites in membranes is changed after irradiation by the interference laser field. The largest effect was observed when erythrocytes were irradiated by the field with 7.2 μm period, which corresponds to maximal energy of interaction of an erythrocyte with a gradient light field.

The effect of interference laser fields on an erythrocyte suspension was investigated both theoretically and experimentally. The optical trapping and orientation of individual erythrocytes in the interference fringes were observed. To describe the effect of erythrocyte orientation in the interference fringes, we used the equation for torque exerted on a disc-like particle in a gradient light field. The experimental results are in agreement with the predictions of a developed theoretical model.

The effect of interference laser fields on red blood cells (RBCs) was investigated both theoretically and experimentally. The optical trapping and orientation of individual RBC in interference fringes were observed. It was found that RBC rouleaux undergo disaggregation under the action of interference laser fields. To describe the effect of RBC orientation in interference fringes, we used the equation for torque exerted on a discoid dielectric particle in a gradient light field. The experimental results are in agreement with the predictions of the developed theoretical model.

To investigate of 4'-diethylamino (FET) and 4'-(15-azacrown-5) (FCR) derivatives of 3-hydroxyflavone in binary solvents and erythrocyte ghosts, we used the red-edge excitation spectroscopy. The results obtained prove the existence of spectral heterogeneity of flavonols in the studied systems. The effect manifests itself in the dependence of the efficiency of excited-state intramolecular proton transfer on the excitation frequency.

To investigate 4′-(diethylamino) (FET) and 4′-N-(15-azacrown-5) (FCR) derivatives of 3-hydroxyflavone in binary solvents and erythrocyte ghosts, we used the red-edge excitation spectroscopy (REES). The results obtained prove the existence of spectral heterogeneity of flavonols in the studied systems. The effect manifests itself in the dependence of the efficiency of excited-state intramolecular proton transfer (ESIPT) on the excitation frequency. The electro-optical absorption method (EOAM) was used to measure the dipole moments of the normal form of FET. The electric dipole moments in the ground (μg) and excited Franck–Condon (μeFC) states have the values 22.7×10−30 and 53.3×10−30Cm, respectively. On optical excitation, the electric dipole moment increases by 34×10−30Cm, and the angle between μg and μeFC is 25°. The results of the electro-optical and spectroscopic measurements enable us to describe more precisely the process of charge and proton transfer in 4′-amino-3-hydroxyflavones. Charge transfer and proton transfer occur alternately. The main stage of forward electron charge transfer takes place after excitation of the normal form (N∗) and partly after ESIPT. In the phototautomer (T), only partial reverse charge transfer happens after photon emission. The second, more efficient stage of reverse electron charge transfer occurs after radiationless conversion of phototautomer into the normal form.

Summary form only given. It is well known that 3-hydroxyflavone exhibits the solvent-controlled excited-state intramolecular proton transfer (ESIPT) reaction and therefore its derivatives can serve as sensitive fluorescent probes for investigating microparameters of biological membranes and macromolecules. We present results of steady-state and time-resolved fluorescence spectroscopy investigations of 4'-diethylamino (FET) and 4'-(15-azacrown-5) (FCR) derivatives of 3-hydroxyflavone in simple and binary aprotic solvents, and human erythrocyte membranes. The presence of the 4'-amino substituent in the 3-hydroxyflavone molecule leads to an increase in its dipole moment, which results in more pronounced solute-solvent effects. Due to the different sizes of substituents in the FET and FCR molecules it is expected that these compounds can be used as fluorescent probes sensing different regions of a biological membrane.