Spectral properties of an indotricarbocyanine dye upon complex formation with nanodiamonds in aqueous medium were studied. Complex formation is accompanied by the disappearance of the H*-aggregated band at 514 nm as well as by a bathochromic shift of the electronic absorption peak from 706 to 718 nm. At the same time, the emission spectrum of the dye is almost unchanged, and the fluorescence excitation peak is shifted from 706 to 710 nm. Based on the analysis of IR absorption spectra, it was found that carboxyl groups in the dye molecules play an important role in the complex formation of the dye with nanodiamonds. In the presence of human blood serum, complexes break down and dye molecules bind to serum proteins, which is confirmed by a significant increase in the lifetime and fluorescence anisotropy. The complexes obtained can be used as a basis of fluorescent biosensors.

The effect of the vacuum annealing temperature on the structure and functional composition of the surface of ultradispersed diamond (UDD) produced by detonation synthesis was studied using Raman scattering, IR absorption, X-ray diffraction analysis and electron paramagnetic resonance. It was established that vacuum annealing at T ≤750°C does not affect the structure of diamond nanoparticles; at higher annealing temperatures, the formation of amorphous sp 2 -hybridized carbon begins on the surface of the particles. Annealing at a temperature of 1050°С leads to complete graphitization of the UDD surface with preservation of the diamond structure of the nucleus of the particles. During annealing in the temperature range of 650-750°C, the minimum of functional groups is observed on the UDD surface, while the surface retains high activity.

Absorption, fluorescence excitation, and fluorescence spectra and the fluorescence polarization as a function of emission wavelength were measured at 77 K for glassy EtOH solutions of 2,3-diazabicyclo[2.2.2]oct-2-ene and 1,4-dimethyl-(2,3-diazabicyclo[2.2.2]oct-2-ene). It was concluded from an analysis of the results that two excited electronic states were responsible for the emission of these compounds. The transition dipole moment vectors from the ground state into the excited ones were mutually perpendicular so that the corresponding spectra were shifted.

The fluorescence and fluorescence excitation spectra of azocompound, 2,3-diazabicyclo[2.2.2]oct-2-ene, have been studied using jet cooling. The violation of the mirror symmetry between the fluorescence and fluorescence excitation spectra due to an intense long-wavelength emission that manifests itself in solutions and in the gas phase cannot be eliminated even by jet cooling. It has been revealed that the bands of pure electronic and vibronic transitions are split by 0.55 cm−1, which is caused by tunneling with accompanying emission from an intermediate short-lived state and which may be the reason for the violation of the mirror symmetry of the spectra upon tunnel inversion.

A new method was developed for the synthesis of 2-aryl-6-methyl-4H-pyrones by the condensation of arylmethylketones with the acetoacetic ester ethylene ketal in the presence of sodium alkoxylate. New laser merocyanine dyes, the analogues of 4-dicyanomethylene-2-methyl-6-[(4-dimethylamino)styryl]-4H-pyran (DCM), were obtained based on the synthesized 2-aryl-4-pyrones. The dyes are characterized by high generation efficiency in the red spectral range.

Conformations of He-jet-cooled trimethyl[(3-indole)ethoxy]silane (TIES) have been studied using a laser spectroscopy technique in combination with quantum-chemical computations. Six probable conformers of the molecule were computed, of which only two conformations were observed. Based on an analysis of fluorescence excitation spectra, fluorescence spectra, shapes of rotational band contours at the electronic S0–S1 transition of TIES, and theoretical computations, the above conformers were assigned to steric structures. Twisted structures have the lowest energy due to intramolecular hydrogen bonds \( C - H \cdots O <_C^{Si} \) between hydrogen atoms of methyl groups and an oxygen atom and C–H···π between H and the π-electron cloud of the indole ring.

ColloIDal dispersions and thin films containing poly-N-(epoxypropyl)carbazole (PEPK) and Ag—Au nanoparticles (2–3 nm in diameter) were prepared and investigated by TEM, optical and IR spectro-scopy, and electrophysical tools. The introduction of nanoparticles results in cooperative phenomena between the polymer and the Ag—Au particles; as a consequence these particles increase the electrical conductivity of the nanocomposite films by at least one order of magnitude, even in very low concentrations.

New thiol terminated biphenyloxazole molecules are synthesized. A self assembled monolayer has been prepared on gold surface and spectral and luminescent properties of free molecules and ordered films have been studied experimentally and theoretically (DFT). The luminescence polarization degree is about 40%. New absorption and luminescence bands have been found experimentally and confirmed theoretically. The highest occupied and the lowest unoccupied molecular orbitals of adsorbed molecules strongly differ from not adsorbed thiol molecules.

We present results of experimental and theoretical studies of the optical characteristics of a new indotricarbocyanine dye that is capable of effectively limiting the power of laser radiation in the visible spectral range. The spectral-luminescent and energy characteristics of the dye molecules and their absorption spectra from the excited state with nanosecond resolution are investigated experimentally. Quantum-chemical methods are used to calculate electronic absorption spectra from the ground (S0 → Sn) and excited (S1 → Sn) states and to determine the nature of electronic states of the molecule and the rate constants of intramolecular photophysical processes. The results of the theoretical research agree with experimental data. It is shown that the investigated dye has singlet-singlet absorption at 400–600 nm. Nonlinear absorption of the dye upon excitation by radiation of the second harmonic of a Nd:YAG laser is studied by z-scanning with an open diaphragm. The ratio of dye absorption cross sections from the excited and ground states at 532 nm is determined in the framework of a three-level model. The results are compared with those for previously studied compounds.

The nonlinear optical properties of a number of polymethine dyes (PD 7005, 7006, 7031, and 7098) with a fixed polymethine chain are studied upon their excitation by the focused second-harmonic radiation from a nanosecond Nd:YAG laser. It is found that PD 7098 has the minimum linear absorption over a greater part of the visible spectrum and the strongest nonlinear reverse saturable absorption. The attenuation coefficient of the 100-MW cm-2 laser radiation in the ethanol solution of this dye is K=14. The characteristics of a single-stage high-power-laser-radiation limiter consisting of two confocal lenses with a focal distance of 5.5 cm are optimised. The maximum values of attenuation coefficients measured in experiments are 420 (for the initial transmission T0≈50%) and 170 (T0≈70%). The singlet—singlet absorption cross sections of the dyes are estimated from experiments. The efficient laser radiation limiter considered in the paper features a broad spectral range in the visible region and a high service time.