Results of studying the influence of the component composition of liquid scintillators on their scintillation properties are presented. The correlation between the energy resolution and the peak-to-valley ratio in β-ray spectra is discussed. Compositions of fire-safe scintillation systems with characteristics above the generally accepted standard are proposed.

Luminescence spectra in liquid crystalline (LC) solvents were measured for stilbene, p-terphenyl, o-POPOP, 2-(1-naphtyl)-5-phenyloxazole and other compounds commonly used as luminophores or scintillators. The choice of substances was prompted by the ability of their molecules to assume different predominant conformations in different phase states (e.g., standard organic solution vs. melt-grown single crystal). For each compound studied, the luminescence spectra were compared within the sequence "standard organic solution - solution in LC matrix - single crystal". Several distinct cases could be singled out, with the luminescence peak lambda(max) shifted to longer wavelengths, to shorter wavelengths, remaining essentially unchanged, or being split into two separate peaks corresponding to two conformations with close distribution probabilities. For each compound, the observed luminescence behavior could be easily associated with the corresponding changes in the effective molecular shape supposedly induced by the LC and crystal ordering. The obtained data could serve as a basis for future search of efficient liquid crystalline scintillators.

Spectral and luminescence properties and association of stilbene and distyrylbenzene derivatives in hydrocarbon solvents have been studied. The bulky triphenyl amine group being a strong electron donor introduced in those molecules has been shown to make it possible to obtain efficient yellow-green organic luminophors not inclined to association.

Mesophase formation is reported in ionic liquid crystal mixtures of lead decanoate with gadolinium alkanoates. The negative effect of Gd salts on mesophase thermal stability increased in the order stearate < undecanoate < 2-ethylhexanoate, with gadolinium-containing mesophase persisting on introduction of the non-mesogenic Gd salts up to 40 %, 12 % and 5 %, respectively. In a ternary system, the mesophase range of similar to 20 degrees C, starting below 80 degrees C, could be obtained at similar to 25 % gadolinium salt concentration.

The H-complex-forming reaction of naphthalimide derivatives with phenol has been investigated by IR spectroscopy. It was shown that for the majority of compounds studied the carbonyl group is the main center of basicity. In the case of amino-substituted imides of naphthalic acid transfer is possible of the reaction center from the carbonyl group to the nitrogen atom of the substituent introduced into the naphthalene ring. However because of steric hindrance this occurs only for amino- and methylamino-substituted naphthalimide.

Vacuum‐deposited and spin‐coated color changing media (CCM) films for use in color microdisplays with blue OLED emitters have been demonstrated with optical density 5.0 and 2.8 per micron at the maximum of absorption, respectively. CCM efficiency has been studied as a function of film thickness, dopant concentration and excitation wavelength.

AbstractVarious approaches to color changing media (CCM) for color microdisplays using blue pixelated OLED display with blue‐to‐green and blue‐to‐red CCM have been studied. Vacuum‐deposited CCM films have been demonstrated with optical density 3.75/micron at the maximum of absorption and absolute quantum efficiency of photoluminescence of 82% and 67% for B/G and B/R CCM, respectively.

The acid-base interactions of 2,5-diphenyl-1,3-oxazole and some model compounds in aqueous-alcoholic media were studied by electronic absorption and fluorescent spectroscopy. The spectral-luminescent characteristics of the prototropic forms were obtained, and the equilibrium constants of the protolytic processes were estimated. It was found that the presence of intramoleculr hydrogen bond only slightly affects the basicity of the ortho-hydroxy derivatives with respect to protonation by the oxazole ring in the ground state. The elimination of the dimethylamino group from conjugation with the major chromophoric fragment of 2-(2-hydroxyphenyl)-5- [4-(dimethylamino)phenyl]-1,3-oxazole by protonation of the former in a weakly acidic solution gives rise to fluorescence of the phototautomeric form, which is incharacteristic of this compound in a neutral medium.

A series of ω, ω′-dihetaryl-substituted 2,5-dimethyl-1,4-divinylbenzenes has been synthesized and these show an increased solubility when compared with analogs not containing methyl groups in the central benzene ring. The dependence of spectral parameters on the chemical structure has been analyzed.

A convenient, one-step method for synthesis of the N-(3-hydroxypropyl)imide of 4-(3′-hydroxypropyl)-aminonaphtalic acid is proposed. It has been found that ethylene glycol monoethyl ether can be successfully used to replace solvents previously used for these reactions.

Luminescence spectra of 1,3,5-triphenyl-2-pyrazoline with acceptor substituents or with substituents in a 5-phenyl ring having an extended conjugated system are studied. These compounds exhibit considerably lower fluorescence quantum yield compared to that of the unsubstituted compound. Experimental and calculation data suggest that the fluorescence quenching of these bichromophore molecules with unconjugated chromophores could be related to a thermal population of ''mixed'' excited slates involving occupied molecular orbitals of one chromophore and unoccupied orbitals of another.

The spectral characteristics of seven 5-aryl(heteroaryl)-2-phenyl-1,3,4-oxadiazole derivatives, containing an expressed electron-accepting grouping such as sulfonyl fluoride or sulfonyldifluoromethane in the para position of the phenyl substituent, have been investigated in solvents of various polarity. The insignificant effect of the nΠ * levels of the SO 2 X grouping on the fluorescence properties of the compounds studied was established, as a result of which they are highly effective organic luminophors in the near ultraviolet and violet spectral ranges. The presence was shown of a significant solvatochromic effect exerted particularly clearly in derivatives with electron-donating groups in the 5-aryl substituent. As a result of this, the compounds indicated may be recommended for use as fluorescent probes in medicine and biology. Adiabatic flattening in the excited state of the sterically hindered methoxy derivative and the formation of a TICT state are considered, leading to quenching of the fluorescence of dimethylamino derivatives in media of high polarity.

Spectral and luminescent properties of some ortho-hydroxy derivatives of 2,5-diaryloxazole were examined in aprotic solvents of different polarity. A reaction of intramolecular photoinduced proton transfer is typical for these compounds in an excited state. The effects of solvent polarity and basicity and molecular structure of the compounds on the efficiency of photoinduced proton transfer were considered. It was found that this efficiency in ortho-hydroxy derivatives of 2,5-diaryloxazole depends mainly on an increase in acidity of the hydroxy group in the transition to the excited state. It was suggested that fluorescence quenching in a reaction product of intramolecular photoinduced proton transfer (in a phototautomeric form) makes the main contribution to a decrease in emission efficiency of the examined ortho-hydroxy derivatives of diaryloxazole, as compared with their analogues without intramolecular hydrogen bonds.