Vol 122, No 2 (2017)

The photosensitizing ability of an agent based on chlorin e6 (Photoditazin), which is used for photodynamic diagnosis and therapy, is compared with that of a new preparation on the basis of coproporphyrin III in the environment of a phosphate buffer and a simulated biological environment (albumin solution). The efficiency of singlet-oxygen production was estimated by EPR spectroscopy and spectroscopy in the UV and visible ranges with the use of “chemical traps” of singlet oxygen. By irradiating drugs with LED emission centered at λ_max = 520 nm, we determined the quantum yield of singlet-oxygen production in a buffer solution; the obtained values are 0.60 and 0.37 for chlorine and coproporphyrin, respectively. The steady-state concentration of singlet oxygen upon irradiation of solutions of the studied photosensitizers with concentrations of 12–43 μМ and the density of radiation power within the 6–96 W/cm² region was found to be in the region of 10¹⁰–10¹¹ molecules/cm³. It is shown that the introduction into the solution of egg albumin (0.1%) reduces the sensitizing properties of the two drugs by two to three times, while the efficiencies of the preparations with respect to singlet-oxygen production become almost identical (0.19 and 0.17).

The IR and UV spectra of the [CuIL(PPh₃)] complex (PPh₃ = triphenylphosphine, L = 3-pyridine- 2-yl-5-phenyl-1Н-1,2,4-triazole) have been analyzed in detail within the density functional theory (DFT) and its time-dependent version TD DFT. The standard functional B3LYP and sets of basis orbitals 6-311G(d,p) and Lanl2DZ are used for the atoms of the elements of periods I and II and for the iodine atom, respectively. The calculated IR spectra of the complex and free ligands coincide with the observed IR bands, due to which one can completely interpret all normal modes and confirm X-ray diffraction (XRD) data. Particular attention is paid to the structure of excited triplet (Т₁) state in order to explain the role of copper and iodine ions in the formation of photo- and electroluminescence spectra. It is shown that the equilibrium Т₁ state undergoes structural relaxation after the vertical excitation and significantly changes its electronic nature and the charge transfer structure.

We propose a version of the theory describing the circular dichroism spectra of cholesteric liquidcrystal dispersion particles of double-stranded DNA. The basis of the theory is the concept of absorption of electromagnetic waves by large molecular systems. The effect of physical parameters of dispersion particles on their circular dichroism is theoretically determined. It is experimentally demonstrated that circular dichroism can be used as a convenient tool for creating an optical analytical system for the determination of biologically active compounds that interact with DNA molecules.

Singlet–singlet energy transfer between molecules of fluorescein and oxazine dyes in Langmuir–Blodgett films is studied experimentally. The dependence of the energy-transfer efficiency on the distance shows that the quenching of the donor fluorescence is the most efficient when the layers of the donor and acceptor molecules are in a direct contact. An increase in the distance between the donor and acceptor layers leads to a decrease in the energy-transfer efficiency. To establish the mutual orientation of the donor and acceptor molecules, quantum-chemical calculations of the energy transfer process in the donor–acceptor pair are carried out. The calculations show that the best correlation of the experimental and calculated values of the energy-transfer efficiency is observed when the interacting particles are shifted relative to each other by about ~0.12 nm in parallel planes. The presented approach can be used to estimate the relative orientation of interacting particles in multimolecular ensembles.

Nanostructured supramolecular complex of europium(III) with bathophenanthroline (bphen), with detonation synthesis nanodiamonds (NDs) used as a structure-forming element, has been synthesized for the first time. The characteristics of the Eu(bphen)₂(NO₃)₃ complex and the supramolecular complex with NDs, ND–Eu(bphen)₂(NO₃)₂, are studied and compared using scanning electron microscopy (SEM), luminescence spectroscopy, IR spectroscopy, and electron-spin resonance (ESR) spectroscopy. The luminescence quantum yields of the complexes are estimated by the relative method using a β-diketonate complex of europium (III) with tris(thenoyltrifluoroacetone) and 1,10-phenanthroline (Eu(TTA)₃phen) as a reference. It is found that the ND–Eu(bphen)₂(NO₃)₂ supramolecular complex has a higher photoresistance than the complex without NDs and no worse thermal stability (up to a temperature of +150°C).

The change in probability of spontaneous emission for emitter placed in one-dimensional photonic quasicrystal (optical Fibonacci lattice) was examined. When the dipole is placed in Fibonacci lattice two different scenarios can be expected: enhancing (if frequency and direction of the dipole emission correspond to optical eigenmode of structure, and position corresponds to maximum value of modes electric field profile) or suppression (in case of photonic band gap) of spontaneous emission rate. Fact that both effects are expressed in quasicrystals less than in the Bragg reflectors and in the microcavities was demonstrated.

We review recently emerged methods of high-order harmonic enhancement in the extended laserproduced plasmas using ionic resonances and nanoparticles and show the difference of this approach with regard to previously used methods. Particularly, we analyze the harmonic generation in graphene and a few other clustered media using 800-nm-class lasers. We also discuss the application of parametric waves for frequency conversion towards the extreme ultraviolet range and show the resonance enhancement of harmonics in laser-produced zinc plasma using tunable mid-infrared pulses. The reviewed studies demonstrated the attractiveness of the joint application of the methods of harmonic enhancement using ionic resonances and nanoparticles.

We consider degenerate plasma that is located in the field of a transverse electromagnetic wave. An electric current generated in the plasma by the electromagnetic field is sought. During classical description of the interaction of the electromagnetic wave with the plasma, the Vlasov kinetic equation is used, while, in quantum description, the quantum kinetic equation with the Wigner integral is applied. A nonlinear analysis has shown that that the electric current in the plasma has two nonzero components. One component of the electric current is directed along the vector potential of the electromagnetic field. The other nonzero component of the current is directed along the wave vector. In the present work, we analyze this component of the electric current. The case of collisionless plasma is examined.

In the problem of light scattering by small axisymmetric particles, we have constructed the Rayleigh approximation in which the polarizability of particles is determined by the generalized separation of variables method (GSVM). In this case, electric-field strengths are gradients of scalar potentials, which are represented as expansions in term of eigenfunctions of the Laplace operator in the spherical coordinate system. By virtue of the fact that the separation of variables in the boundary conditions is incomplete, the initial problem is reduced to infinite systems of linear algebraic equations (ISLAEs) with respect to unknown expansion coefficients. We have examined the asymptotic behavior of ISLAE elements at large values of indices. It has been shown that the necessary condition of the solvability of the ISLAE coincides with the condition of correct application of the extended boundary conditions method (ЕВСМ). We have performed numerical calculations for Chebyshev particles with one maximum (also known as Pascal’s snails or limaçons of Pascal). The obtained numerical results for the asymptotics of ISLAE elements and for the matrix support theoretical inferences. We have shown that the scattering and absorption cross sections of examined particles can be calculated in a wide range of variation of parameters with an error of about 1–2% using the spheroidal model. This model is also applicable in the case in which the solvability condition of the ISLAE for nonconvex particles is violated; in this case, the SVM should be considered as an approximate method, which frequently ensures obtaining results with an error less than 0.1–0.5%.

The problem of excitation of a totally reflecting planar optical waveguide using a coupling diffraction grating in the form of a periodic relief of the waveguide-layer thickness is solved within the single-scattering approximation. The polariton mode in the presence of a quantum well near the waveguide is considered. Based on the developed concepts, the following experimental features of the dependence of the intensity of radiation conducted in the waveguide layer on the angle of incidence of the excitation beam on the coupling diffraction grating are interpreted: the dependence on the mode number, the interference effects in the presence of two coupling diffraction gratings, and the influence of the lower substrate boundary on the thermal behavior of the waveguide structure.

An algorithm for determining the thermal stress in round cylindrical monocrystals by means of the integral photoelasticity method is analyzed. Transillumination in a cross section of a sample is assumed. The optical problem is solved within the framework of the paraxial approximation assuming weak birefringence. Reconstruction is based on the measurement of characteristic parameters of the polarized light propagated through the sample.

A method for measuring mechanical stresses of photoelastic materials from the difference between the reflection coefficients of orthogonally polarized light waves incident on the surface of the stressed medium is considered. Comparative results of measurements of the stress state of polymethylmethacrylate in the conventional transmission polarization optical scheme and by the proposed refraction method are presented. A case of normal light incidence is considered.

Highly selective volume-diffraction gratings are recorded on a holographic acrylate nanocomposite. The holographic characteristics of the gratings are studied. It is shown that the diffraction efficiency of gratings can reach 50% and a 3D hologram is formed. The refractive index modulation is 0.048–0.065.