Fluorescence excitation spectra of jet-cooled carbazole complexes with monohydric alcohols

We have analyzed the fluorescence excitation spectra of carbazole complexes with a single molecule of methyl, deuterated methyl, ethyl, and propyl (1-propanol and 2-propanol) alcohols, cooled in a supersonic jet. We have determined the shifts in the fluorescence excitation spectra of the complexes relative to the frequency of the purely electronic transition of unbound carbazole. They occur as a result of formation of hydrogen bonds between the N-H group of the carbazole and the OH group of the alcohols. The frequencies of stretching vibrations of the hydrogen bonds with different alcohols vary within the range 150–157 cm⁻¹, while the frequencies of the bending vibrations vary in the range 21–22.9 cm⁻¹. From the shape of the rotational contours of the bands for the purely electronic and vibronic transitions of the complexes, we determined that they belonged to rotational conformers. We calculated the equilibrium configurations of the complexes in the ground state. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 756–760, November–December, 2007.     

Competitive Trapping of Nitric Oxide (NO) Between Fe(III)-dithiocarbamate Complex and Liposome-encapsulated Trimethylammonio-PTIO: Effects of Ligand Structure, Charge on Liposome Surface, and External Pressure on NO-trapping Rates

Using a competitive nitric oxide (NO)-trapping method between Fe–dithiocarbamate (DTC) complexes and liposome-encapsulated 2-[4-trimethylammonio]-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide (TMAPTIO), NO-trapping rates of Fe–DTC complexes in the presence of phosphatidylcholine liposomes were quantified for five kinds of Fe–DTC complexes. We investigated how the DTC ligand structure influences the NO-trapping rates of Fe–DTC complexes. The negatively charged liposomes give a higher NO-trapping rate of Fe–DTC complexes than do the positively charged ones, suggesting that the presence of a charge on the liposome surface affects the NO-trapping rate processes of Fe–DTC complexes. In addition, on the basis of the pressure dependence experiments for the competitive reaction, we evaluated the difference in activation volumes between the NO-trapping reactions by Fe–DTC complexes and TMA-PTIO, which allowed us to consider possible reaction mechanisms for the NO-trapping processes.     

Thermally stimulated transformation of the structure of cobalt complexes in polyvinyl alcohol-cobalt(II) chloride systems

We present the kinetic and temperature dependences of the optical absorption of thermochromic films of polyvinyl alcohol with added CoCl₂. Based on the data obtained, we have analyzed the possibility that tetrahedral cobalt complexes are formed from octahedral complexes. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 826–829, November–December, 2007.     

Influence of the Nature of meso-Substituents and Extra-Ligands on the Luminescence of Ytterbium in Complexes with Porphyrins

Complexes of ytterbium with various meso-tetrasubstituted porphyrins have been obtained and their spectral-luminescent properties have been investigated. It is shown that the quantum yield and the lifetime of 4f-luminescence of the ytterbium ion are higher in complexes with porphyrins that contain aromatic and heteroaromatic meso-substituents (as compared to n-alkyl ones) and also in complexes with the acetylacetonate ion as an extra-ligand.     

Luminescence diagnostics of malignant tumors in the IR spectral range using Yb-porphyrin metallocomplexes

The creation and application of new low-toxic photosensitizers for the luminescence diagnostics of cancer are considered. The new photosensitizers weakly generate singlet oxygen, exhibit developed luminescence, and retain the tumor-tropic properties of the therapeutic photosensitizers. Twenty one ytterbium complexes of porphyrin compounds that differ by the substituents at the periphery of the porphyrin ring are synthesized. The absorption and luminescence spectra and the luminescence decay curves of these substances are studied. The primary toxicological and pharmacokinetic investigations are performed for the most promising compounds in the organisms of experimental animals. The experimental data prove that the Yb-porphyrin complexes are promising as low-toxic markers for the luminescence diagnostics of malignant tumors in the IR spectral range (975–985 nm) that are free of the phototoxicity typical of the conventional porphyrins at a relatively high luminescence contrast and the selective accumulation in tissue.     

LiNbO<Subscript>3</Subscript>:Yb<Superscript>3+</Superscript> crystals for optical temperature sensors

Possibilities of using lithium niobate crystals, doped with ytterbium (LN:Yb³⁺) as materials for optical temperature sensor (OTS), are discussed. We consider both the radiative and absorptive characteristics of the crystals, assuming that their temperature dependences are caused by the Boltzmann factor of the initial population of Stark sublevels of the ion. It is shown that the crystals can be used as materials for OTS in the temperature range 150–400 K.     

Enhancement of Europium Luminescence in Tetracycline–Europium Complexes in the Presence of Urea Hydrogen Peroxide

An increase in the europium emission band was observed, for the first time, with addition of urea hydrogen peroxide to the tetracycline–europium (Tc–Eu)solution. We have observed that the wavelength, the band width and the area of ⁵D₀→⁷F₂ europium transition change with the urea hydrogen peroxide concentration. We claim that the tetracycline–europium complexes can be used as probes of urea hydrogen peroxide concentration.     

Some features of formation of an inclusion complex ofβ-cyclodextrin with rhodamine 6G

Results of an investigation of the influence of the process of complex formation on the spectral and luminescence characteristics of aqueous solutions of inclusion complexes of β-cyclodextrin with rhodamine 6G are reported. It is shown that complex formation of rhodamine 6G proceeds mainly in the outer sphere of β-cyclodextrin. To whom correspondence should be addressed. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 619–621, September–October, 1999.     

Generating a Warm Glow: Lanthanide Complexes Which Luminesce in the Near-IR

This article reviews and expands upon our observations of neodymium and ytterbium-centered luminescence in the near-IR. A variety of neodymium (III) and ytterbium (III) complexes with aminocarboxylate ligands was synthesized and their photophysical properties were investigated in aqueous solutions. Metal-centered emission was observed in the near-IR for complexes of both ions and time-resolved studies were used to show how quenching of the excited states is dependent on both inner and outer sphere coordinated water molecules.     

Transfection using hydroxyapatite nanoparticles in the inner ear via an intact round window membrane in chinchilla

Hydroxyapatite nanoparticles (nHAT) are known to have excellent biocompatibility, and have attracted increasing attention as new candidates of non-viral vectors for gene therapy. In our previous studies, nHAT carrying a therapeutic gene and a reporter gene were successfully transfected into the spiral ganglion neurons in the inner ear of guinea pigs in vivo as well as in the cultured cell lines, although the transfection efficiencies were never higher than 30%. In this study, the surface modification of nHAT with polyethylenimine (PEI) was made (PEI–nHAT, diameter = 73.09 ± 27.32 nm) and a recombinant plasmid carrying enhanced green fluorescent protein (EGFP) gene and neurotrophin-3 (NT-3) gene was constructed as pEGFPC2–NT3. The PEI modified nHAT and the recombinant plasmid was then connected to form the nHAT-based vector–gene complex (PEI–nHAT–pEGFPC2–NT3). This complex was then placed onto the intact round window membranes of the chinchillas for inner ear transfection. Auditory brainstem response (ABR) was tested to evaluate auditory function. Green fluorescence of EGFP was observed using confocal microscopy 48 h after administering vector–gene complexes. There was no significant threshold shift in tone burst-evoked ABR at any tested frequency. Abundant, condensed green fluorescence was found in dark cells on both sides of the crista and around the macula of the utricle. Scattered EGFP signals were also detected in vestibular hair cells, some Schwann cells in the cochlear spiral ganglion region, some outer pillar cells in the organ of Corti, and a few cells in the stria vascularis. The density of green fluorescence-marked cells was obviously higher in the vestibular dark cell area than in other areas of the inner ear, suggesting that vestibular dark cells may have the ability to actively engulf the nHAT-based vector–gene complexes. Considering the high transfection efficiency in the vestibular system, PEI–nHAT may be a potential vector for gene therapy of inner ear diseases, especially vestibular disorders, and deserves further study.     

Spectral luminescence properties of Eu(III) complexes with tetracycline antibiotics and hydrogen peroxide

We have studied the spectral luminescence properties of mixed-ligand complexes of Eu(III) ions with tetracyclines and hydrogen peroxide. We have established that incorporation of hydrogen peroxide into the inner sphere of these complexes leads to a significant increase (by a factor of 10–25) in the intensity of luminescence of the Eu(III) ions, redistribution of the intensities of the ⁵D₀ → ⁷F_j transitions, in particular to an anomalous increase in the intensity of the band for the forbidden transition ⁵D₀ → ⁷F₀. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 3, pp. 310–314, May–June, 2007.     

Hydrogen in amorphous and crystalline ytterbium films

Ytterbium vapor condensation on a liquid-helium cooled substrate in a hydrogen atmosphere is used to obtain Yb-H films containing up to 55 at.% hydrogen. Various thermodynamic and kinetic parameters of the transition of these films from the amorphous to the crystalline state (a→c transition) are investigated along with the electrical conductivity of these states. It is shown that the investigated properties of Yb-H films containing up to 40 at.% hydrogen are essentially indistinguishable from those of pure Yb films in the temperature interval 4.2–293 K. Increasing the hydrogen concentration to 55 at.% leads to an insignificant increase in the electrical resistivity, the kinetic temperature, and the activation energy of the a→c transition, and also to a decrease of the propagation speed of self-maintaining avalanche (explosive) crystallization. Reasons for the observed influence of hydrogen on the properties of Yb-H films are analyzed. The examined low-temperature Yb-H condensates can be characterized as a “frozen” solid solution of hydrogen in ytterbium in the temperature interval 4.2–293 K. Storing such films at room temperature leads to the formation of ionic ytterbium dihydride YbH₂. Fiz. Tverd. Tela (St. Petersburg) 41, 177–182 (February 1999)     

Absorption spectra and the nature of complexes in the polyvinyl Alcohol-Nickel (II) chloride system

We have used electronic spectroscopy in the 160–1100 nm range to study the polyvinyl alcohol-nickel(II) chloride system. Based on the results obtained, we hypothesize formation of mixed-ligand complexes of the type [Ni(H₂O)_6-nCl_n]^2-n (n = 0, 1,..., 5) in the polyvinyl alcohol matrix. Transformation of the coordination sphere as the NiCl₂ concentration changes is apparent both in the region of the d-d transition bands (350–1100 nm) and in the region of the charge transfer bands (160–250 nm). We propose assigning the absorption bands separated by mathematical treatment to complexes of specific compositions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 136–138, January–February, 2006.     

Effect of montmorillonite filler on structural and electrical properties of polymer nanocomposite electrolytes

Polymer–clay nanocomposites consisting of polymer (polyethylene oxide) and NaI as salt with different concentration of organically modified Na⁺-montmorillonite (DMMT) have been fabricated and characterized. X-ray diffraction analysis shows that the polymer–salt complexes have been intercalated into the nanometric silicate layers of DMMT. Fourier transform infrared analysis shows that the polymer structure in the clay interlayer is similar to that of the polymer–salt complexes, and there is a strong interaction between the polymer–salt complexes and clay layers. A study of surface morphology using scanning electron microscopy reveals that microstructure of composites is affected by clay addition. Complex impedance analysis was used to calculate the bulk resistance of the composites. An enhancement in the conductivity of about one order of magnitude has been observed on 5% clay addition compared to that of the polymer–salt complexes, and it decreases monotonically for higher clay concentration. The effect of clay concentration on the structural and physical properties of polymer nanocomposites is well correlated.     

Immobilization and Characterization of 2,3-diaminonaphthalene/cyclodextrin Complexes in a Sol–Gel Matrix: A New Fluorimetric Sensor for Nitrite

The aromatic diamino compound 2,3-diaminonaphthalene (DAN) has been extensively used to detect and quantify nitrite ions in biological and environmental samples. We have immobilized the DAN reagent in a porous silicate glass matrix, via previous incorporation of the dye in HP-β-CD. Changes in fluorescence intensity were used to characterize the inclusion complexes and determine the association constant and stoichiometry of the process. Fluorescence spectrum of these complexes was also used to monitor their immobilization within the sol–gel matrix. Reactivity of the immobilized complexes was evaluated with increasing concentrations of nitrite up to 10 μM (with a detection limit around 20 nM). Results show that sol–gel immobilization does not modify the reactivity of the dye against nitrite and serves to prepare a highly sensitive ready to use fluorescence-based sensor for the specific measurement of nitrite at submicromolar concentrations with no further sample pretreatment.     

Energy barriers at the interfaces in the MIS system Me-Yb2O3-Si

The electrophysical properties of silicon MIS structures with ytterbium oxide as the insulator are investigated. It is established that the electrical conductivity of the MIS structures are described by a Poole-Frenkel mechanism. The capacitance-voltage curves are used to measure the trapped charge in the insulator and the density of surface states. The energy barriers for electrons at the interfaces are determined by the method of internal photoemission of charge carriers into the insulator. The parameters of deep electron traps in ytterbium oxide are investigated. Zh. Tekh. Fiz. 69, 60–64 (April 1999)     

Effect of bengal rose sensitizer on activity of the photosynthetic apparatus of green barley leaves

We have observed disruption of the energy distribution between chlorophyll-protein complexes, their partial degradation, and inactivation of photosystem II in green barley leaves under photooxidative stress conditions induced by the photosensitizer bengal rose. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 266–269, March–April, 2006.     

Luminescence of Nile red as indicator of composition of nanoparticles from diketonate complexes of trivalent metals

We study the sensitization of fluorescence of Nile red in nanoparticles formed in aqueous solutions of complexes of Al, In, Sc, and Lu with DBM, DBM, and phen and of complexes of In with MBTA and phen. We show that, at concentrations of Nile red of 2–50 nM and complexes of 10–30 μM, the fluorescence intensity of Nile red in aqueous solutions increases by 1.5–2 orders of magnitude compared to its fluorescence in H₂O. We find that, at these concentrations of Nile red in solutions of complexes Al, the dye is completely contained in nanoparticles from these complexes. We show that Nile red molecules are inhomogeneously distributed in nanoparticles from complexes and, upon the completion of the formation of nanoparticles, dye molecules tend to be localized in regions of nanoparticles formed from diketonate complexes M(diketone)₃phen (M is Lu or In) and Al(DBM)₃. Upon the localization of Nile red in these regions, the maximum of its fluorescence spectrum shifts toward ∼600 nm and, upon the penetration of Nile red into nanoparticles from Sc complexes, the shift of the maximum of its fluorescence spectrum compared to the spectrum in water does not exceed 10 nm. The shifts of the spectra are collated with the ability of ions to form diketonate and hydroxy diketonate complexes. We demonstrate that the fluorescence of Nile red is efficiently sensitized, not only upon its penetration into nanoparticles formed from complexes, but also upon its adsorption on the nanoparticle surface when Nile red molecules are introduced in solutions of already formed nanoparticles.     

Photoconversion and photocatalytic activity of uranyl in acetone solutions

We have studied the effect of irradiation on the uranyl nitrate — acetone and uranyl perchlorate — acetone systems. We have established that when the uranyl perchlorate — acetone system is irradiated, polymerization of the acetone occurs and the catalyst for the process is excited uranyl complexes. In the polymer, uranium is found in the form of nanoclusters of pentavalent and tetravalent uranium, formed as a result of photochemical reactions. Polymerization does not occur in the uranyl nitrate — acetone system. We consider possible factors responsible for the noted differences. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 565–568, September–October, 2007.     

Comparison of selected optical properties of oxyfluoride glass fibers doped with Er3+ and co-doped with Er3+ Yb3+

The method of manufacturing and spectroscopic evaluation of the Er³⁺ ions doped and Er³⁺–Yb³⁺co-doped SiO₂–Al₂O₃–Na₂CO₃–CaO–PbO–PbF₂ oxyfluoride glass fibers is presented in the paper. Both optically active elements erbium and ytterbium were introduced into the batch in the form of fluorides. The X-ray diffraction (XRD) technique was applied at each stage of fibers manufacturing in order to control an amorphous structure of the preforms and fibers. Optical studies of glass preforms and fibers (reflection/transmission, absorption, emission, and excited state absorption (ESA)) were directed to examine their suitability as fiber amplifiers at 1.55 μm band.