Photoluminescence in near ir-region of lithium niobate crystals of different composition and genesis

The dependence of photoluminescent of lithium niobate crystals of different composition and genesis in the near IR- region on stoichiometry, Zn concentration, doping method was observed. It was found that increasing in stoichiometry leaded to decreasing in the photoluminescence. At Zn = 6.5 mol. % in the LiNbO3 crystal an intense emission was observed at 1.45 eV with simultaneous quenching of the NbLi emission. Homogeneous doping method of LiNbO3:Mg,Zn crystal allowed to enhance the luminescence in the region of 1.3–1.5 eV relative to the crystals obtained by direct doping method of the melt.

Investigation of the dispersed composition of dust of inert materials exposed to overload in the manufacture of building materials

At enterprises for the manufacture of building materials, when pouring bulk components, there is an intense emission of dust into the air of the working area of the room. The article presents the results of the dispersed analysis of dust when pouring cement, crushed stone, silicate bricks and chalk, and the integral functions of the distribution of dust particles by diameter are constructed. According to the criteria of Lyashchenko and Reynolds, the results of the sedimentation rate of dust particles were theoretically obtained. Measures are given to reduce the dust content of the air in the working area of the shop.

Mn4+ concentration effect on spectral properties of lithium-germanate glass-ceramics

A series of lithium-germanate glasses with different manganese concentration is synthesized. Li2Ge7O15 nanocrystals nucleate in the glass matrix via standard volume crystallization technique thus obtaining lithium-germanate glass-ceramics. The glass-ceramics possess intense emission near 660-670 nm under two-band excitation at 330 and 450 nm. The luminescence lifetime is 550 μs for 0.05 mol.% MnO2-doped glass-ceramics. The glass-ceramics obtained can be used as a source of deep-red radiation.

Intriguing Heteroleptic ZnII bis(dipyrrinato) Emitters in the Far-Red Region With Large Pseudo-Stokes Shift for Bioimaging

Novel heteroleptic ZnII bis(dipyrrinato) complexes were prepared as intriguing emitters. With our tailor-made design, we achieved far-red emissive complexes with a photoluminescence quantum yield up to 45% in dimethylsulfoxide and 70% in toluene. This means that heteroleptic ZnII bis(dipyrrinato) complexes retain very intense emission also in polar solvents, in contrast to their homoleptic counterparts, which we prepared for comparing the photophysical properties. It is evident from the absorption and excitation spectra that heteroleptic complexes present the characteristic features of both ligands: the plain dipyrrin (Lp) and the π-extended dipyrrin (Lπ). On the contrary, the emission comes exclusively from the π-extended dipyrrin Lπ, suggesting an interligand nonradiative transition that causes a large pseudo-Stokes shift (up to 4,600 cm−1). The large pseudo-Stokes shifts and the emissive spectral region of these novel heteroleptic ZnII bis(dipyrrinato) complexes are of great interest for bioimaging applications. Thus, their high biocompatibiliy with four different cell lines make them appealing as new fluorophores for cell imaging.

4,6-Bis((E)-2-(4′-N,N-diphenylamino-[1,1′-biphenyl]-4-yl)vinyl)-2-phenylpyrimidine

In this contribution, we designed a 4,6-distyrylpyrimidine chromophore with diphenylamino electron-donating groups and biphenylenevinylene extended π-conjugated linkers. This compound has been synthesized in two steps from 4,6-dimethyl-2-phenylpyrimidine by a double Knoevenagel reaction with 4-bromobenzaldehyde followed by a double Suzuki–Miyaura cross coupling reaction with 4-(N,N-diphenylamino)phenylboronic acid. This compound exhibits intense emission in moderately polar solvents as well as in solid state. This compound is characterized by an intense emission solvatochromism with emission ranging from blue in non polar n-heptane to orange in dichloromethane. This chromophore is also sensible to the presence of acid with a bathochromic shift of the charge transfer absorption band and emission quenching.

Photoluminescence of Homoleptic Lanthanide Complexes With Tris(benzotriazol-1-yl)borate

Bright photoluminescent neutral complexes having general formula [Ln(tbtz)3] (Ln = Eu, Tb; tbtz = tris(benzotriazol-1-yl)borate) were obtained by reacting K[tbtz] with EuCl3 and TbCl3. The emissions in the visible range, related to the f-f transitions of the trivalent lanthanide ions, are observable upon excitation with wavelengths shorter than 350 nm. The most intense emission bands correspond to the 5D0 → 7F4 transition at 699 nm for the europium complex and to the 5D4 → 7F5 transition at 542 nm for the terbium derivative. The luminescence is in all the cases mostly associated with the antenna-effect from the coordinated tbtz ligands. The synthetic approach was successfully extended to the preparation of the analogous yttrium and gadolinium derivatives. Tricapped trigonal prismatic geometry was attributed to the complexes on the basis of luminescence data and DFT calculations. Highly photoluminescent plastic materials were obtained by embedding small amounts of [Eu(tbtz)3] or [Tb(tbtz)3] in poly(methyl methacrylate).