Luminophores based on doped Li2B4O7 have been studied by a variety of methods (photoluminescence, pulsed cathodoluminescence and kinetics thereof, thermoluminescence, and electron paramagnetic resonance). Different impurities exhibit both interplay and competition. The interplay of impurities is expressed in the luminescence sensitization due to effective excitation energy transfer which occurs in composite impurity centers. Such centers consist of two differently incorporated impurities, one at a cationic site, another imbedded in the anionic structure. The impurities can compete for a particular position in the crystal lattice, and the priority of doping affects the result. The luminescence and thermoluminescence properties observed in the samples are connected with the structure of impurity centers. It is shown that the loss of trapped charge carriers due to instant recombination on the luminescence centers and low-temperature thermoluminescence (below 400 K) diminishes the luminescence yield for the high-temperature (above 400 K) thermoluminescence peak used in dosimetry.

Compounds of the general composition A2BIBIIIX6 with a double perovskite (elpasolite) structure are currently considered as an alternative to lead halide perovskites APbX3 in electronics and photovoltaics due to their greater compositional flexibility and low toxicity. One such alternative is the recently synthesized double perovskite Cs2AgNaBiBr6 and a number of various substituted compounds. The close values of the radii of silver and sodium cations make tuning the optoelectronic properties of the double perovskite via the substitution of Ag+ by Na+ promising if the formation of the substitution solid solution Cs2Ag1−xNaxBiBr6 takes place. We explored different possible routes for the synthesis of this class of materials, including solid-phase or melt crystallization ampoule syntheses. Varying heating temperature and duration and using standard cooling processing or a quenching-like process, we demonstrate the instability of Cs2NaBiBr6 and Na-substituted compounds Cs2−xNaxAgBiBr6 in the temperature range of 300–650 °C. It is worth noting that the formation of Cs2Ag1−xNaxBiBr6 solid solutions by a solid-phase method is more favorable.

Organic light-emitting diodes (OLEDs) with dual emission in the red and near-infrared regions offer a breakthrough opportunity for simplifying pulse oximetry technology. Here, a new class of bimetallic complexes Eu0.1Yb0.9(L)3Q (L = β-diketonates; Q = neutral ligands) with simultaneous emission at 612 and 978 nm has been reported, optimized for solution-processed OLEDs. A device based on Eu0.1Yb0.9(dbm)3thiadiazolophenanthroline (TDZP) exhibits the highest electroluminescence intensity in both spectral ranges and is employed as a single-pixel light source in a custom-built pulse oximeter prototype. The prototype demonstrates real-time measurement of heart rate and blood oxygen saturation in full agreement with commercial devices. This is the first demonstration of a fully functional OLED-based oximeter relying on dual-emissive lanthanide complexes. This results pave the way for next-generation wearable biomedical sensors using advanced emissive materials and simplified device architectures.

Heterobimetallic lanthanide conjugates were obtained by click-reaction between two monometallic lanthanide complexes with Schiff bases for the first time. For that, novel azido- and ethynyl-substituted ligands, as well as their lanthanide complexes, were obtained and characterised; two new crystal structures were obtained. Click-reaction between ligands and complexes was performed, and the latter was demonstrated to result in the conjugates {Ln1-Ln2} formation. Among the obtained conjugates, {Yb-Nd} and {Yb-Er} demonstrated intense NIR emission with temperature sensitivity in the physiological range of up to 3%/K.

Simple bromides of copper and antimony are still in a focus of interest as compounds or products of decomposition of new complex halides for optoelectronics and photovoltaics. Here the interaction of copper(I) bromide and antimony(III) bromide are investigated on heating up to 650°C. No texturing effects are found for both simple bromides, the grains are shapeless and fused together. It has been demonstrated that SbBr3 releases from the melt resulting in porous ceramic products with lack of antimony to copper. No new additional double bromides are observed in the binary system CuBr - SbBr3.

Simple bromides of copper and antimony are still in a focus of interest as compounds or products of decomposition of new complex halides for optoelectronics and photovoltaics. Here the interaction of copper(I) bromide and antimony(III) bromide are investigated on heating up to 650degree celsius. No texturing effects are found for both simple bromides, the grains are shapeless and fused together. It has been demonstrated that SbBr3 releases from the melt resulting in porous ceramic products with lack of antimony to copper. No new additional double bromides are observed in the binary system CuBr - SbBr3.

Two new VIS-excited NIR-emitting ytterbium complexes Yb(HPTC)(H2O)2 (Yb1) and Yb(HPTC)(Phen) (Yb2) were obtained. Both compounds demonstrated low toxicity for healthy and cancer cells, moreover Yb1 demonstrated selective accumulation in cancer cells.

Two novel chlorin e6 derivatives containing chelating groups on the periphery of the macrocycle were obtained, and two novel complexes of ytterbium with these chlorins were synthesized and characterized. It was found that NIR-II emission of Yb ion was sensitized by chlorins, the sensitization efficiency depended on the distance from Yb to chlorin core. The detailed study of ytterbium complexes luminescence and in vitro experiments were carried out, during which the kinetics of accumulation in tumor cells have been studied. Due to their properties, the obtained metal complexes could find potential application in fluorescent imaging in the NIR-II range.

For oximetry applications, the first dual red–near-infrared (NIR) emissive organic light-emitting diode (OLED) based on mixed-ligand complexes EuxYb1–x(dbm)3BPhen (x = 0; 0.01; 0.02; 0.05; 0.1; 1) is obtained. The photoluminescence quantum yields of the ytterbium and europium in the obtained complexes reach 0.9 and 31%, respectively, which are rather high values for the complexes of these ions. Dual visible–NIR emissive compounds EuxYb1–x(dbm)3BPhen are tested in OLEDs, and Eu0.05Yb0.95(dbm)3BPhen demonstrates the most intense electroluminescence both in visible (270 cd/m2) and NIR range (19 μW/cm2). The Eu0.05Yb0.95(dbm)3BPhen-based OLED is successfully used to produce the first lanthanide OLED-based pulsimeter prototype.

Metal gallium as a low-melting solid was applied in a mixture with elemental iodine to substitute tin(IV) in a promising light-harvesting phase of Cs2SnI6 by a reactive sintering method. The reducing power of gallium was applied to influence the optoelectronic properties of the Cs2SnI6 phase via partial reduction of tin(IV) and, very likely, substitute partially Sn4+ by Ga3+. The reduction of Sn4+ to Sn2+ in the Cs2SnI6 phase contributes to the switching from p-type conductivity to n-type, thereby improving the total concentration and mobility of negative-charge carriers. The phase composition of the samples obtained was studied by X-ray diffraction (XRD) and 119Sn Mössbauer spectroscopy (MS). It is shown that the excess of metal gallium in a reaction melt leads to the two-phase product containing Cs2SnI6 with Sn4+ and β-CsSnI3 with Sn2+. UV–visible absorption spectroscopy shows a high absorption coefficient of the composite material.

Four new NIR-emitting ytterbium complexes Ln(L)(HL) and K[Ln(L)2](H2O)n (Ln = Yb, Lu; L = 2-tosylaminobenzaldehyde-4-azidomethylbenzoylhydrazone (L1) and 2-tosylamino-5-bromobenzaldehyde-4-azidomethylbenzoylhydrazone (L2)) were obtained and characterized, and 6 crystal structures of Yb(L1)(HL1), Lu(L2)(HL2), Lu (L2)(HL2)(n-Hex) (n-Hex =n-Hexane), K[Lu(L1)2](H2O), {KYb(L1)2(H2O)2(THF)}2 and K[Yb(L2)2](THF) were determined. Rational design yielded complexes with intense NIR emission, a Stokes shift of 500 nm (16 100 cm-1), and sensitivity towards the S2-anion. The complexes could penetrate cells, and showed low toxicity.

Lanthanide coordination compounds contining multiple lanthanides are the most promising candidate materials for luminescent thermometry. Sensing elevated temperatures requires highly stable complexes and matrices, such as those of thermally stable polymers. However, most high-temperature polymers are not optically inert, and this can affect their thermometric properties, including decreasing their intensity and sensitivity. In the present paper, the proper selection of the combination of a matrix and two emitters allowed us to obtain a highly sensitive and highly emissive luminescent thermometry material, 1{5[Tb(Bz)3Phen]2+1[Eu(Bz)3Phen]2}:4PI4050, based on terbium and europium complexes in poly(ethylene glycol) diacrylate (PI4050), which is suitable for the detection of temperatures up to 200 °C.

Two new azido-substituted Schiff bases were obtained, and four new ytterbium complexes Ln(L)(HL) and K[Ln(L)2](H2O)n (Ln = Yb, Lu; L = 2-tosylaminobenzaldehyde-4-azidomethylbenzoylhydrazone (L1) and 2-tosylamino-5-bromobenzaldehyde-4-azidomethylbenzoylhydrazone (L2)), well as 6 single crystals of Yb(L1)(HL1), Lu(L2)(HL2), Lu(L2)(HL2)(n-Hex) (n-Hex = n-Hexane), K[Lu(L1)2](H2O), {KYb(L1)2(H2O)2(THF)}2 and K[Yb(L2)2](THF), were synthesized based on them. The introduction of the N3 -group was aimed at the increase of absorption, and as a result, photoluminescence intensity. The composition was thoroughly investigated, and complex crystal structures and photophysical properties were studied, as well as solution behavior was investigated using 1D and 2D NMR spectroscopy and the analysis of the lanthanide-induced shift. High solubility, quantum yields, absorption, and stability against dissociation in DMSO, as well as non-toxicity allowed to propose them as NIR bioimaging materials.

We proposed a novel approach to the creation of a sensor to determine the DMSO impurity in DMSO-d6, based on europium-ytterbium bimetallic complex, which demonstrated the sensitivity up to 31 % per fraction of DMSO in solution. Theoretical model of the sensing system was proposed. It demonstrated that the sensitivity does not depend on the ratio of ytterbium and europium in the bimetallic complexes but depends on the number of molecules of coordinated DMSO upon complex partial dissociation and the rate of quenching by DMSO mole-cules. Based on this theory, mixed-ligand bimetallic complexes of europium and ytterbium (EuxYb1_x(dbm)3B-Phen; Hdbm - dibenzoylmethane, BPhen - bathophenanthroline; ? = 0.01, 0.03, 0.05, 0.07, and 0.1) were proposed for sensing applications, and were synthesized and studied for the first time. The ratio of the lumi-nescence bands of ytterbium and europium ions in a solution of the coordination compound Eu0.1Yb0.9(dbm)3BPhen linearly depends on the ratio of the concentrations of solvents DMSO and DMSO-d6 in the range V(DMSO)/V(DMSO-d6) from 0 to 1, allowing to detect an impurity of DMSO in DMSO-d6. The sensitivity of the observed system increased with the decrease of the DMSO content and equaled to Sr = 0.381 LIR and reached 31 % per fraction of DMSO in solution. The obtained experimental data verified the provided analytical description of the sensing system.

The highest efficiency (430 μW W −1 ) of pure ytterbium luminescence obtained to date for Yb-based OLEDs was reached based on the ytterbium complex with halogenated Schiff base ligands.

Lanthanide complexes Ln(L)(HL) (H2L = 2-tosylamino-benzylidene-(2-benzo[d]thiazole) hydrazone; Ln = Yb, Gd) were obtained and thoroughly characterized. The monomeric structure of Yb(L)(HL)center dot Solv(1) (Solv(1) = 2CH(3)CN + 2EtOH + H2O) and the ligand structure were determined by single crystal X-ray diffraction data. Relatively high solubility (ca. 5 g/l) and quantum yield (0,9%), as well as mobility of electrons (2,33.10(-6) cm(2)/V.s) and holes (4,94.10(-7) cm(2)/V.s) of Yb(L)(HL) allowed its successful use as a host-free near-infrared OLED emission layer. OLED with the heterostructure ITO/PEDOT:PSS/poly-TPD/Yb(L)(HL)/OXD-7/LiF/Al demonstrated pure 1000 nm centred near-infrared luminescence with the external quantum efficiency up to 0.025%, which is one of the highest value for 1000 nm centred electroluminescence.

Multimetallic neodymium-ytterbium-gadolinium compounds with 9-anthracenate and 9-acridinate anions were tested in order to create the first luminescent thermometer for elevated temperatures. High luminescence intensity and high signal resolution were reached thanks to the concentration quenching elimination due to the partial substitution of the emitting ions with Gd3+. As a result, NIR emitting materials for luminescence thermometry in the wide temperature range (83-393 K) based on lanthanide coordination compounds (CCs) were obtained. The best thermometric properties among the studied systems were demonstrated by Yb0.02Nd0.12Gd0.86(ant)3, and its temperature sensitivity reached 1.8% K-1 in the temperature range of 293-393 K.