Search

The application of ultraviolet-C light in the field of surface treatment or photodynamic therapy is highly prospective. In this regard, the stable fluorescent silicate SrO-CaO-MgO-SiO2-Pr2O3 glasses able to effectively convert visible excitation on the ultraviolet praseodymium emission were fabricated and examined. An unusual wide-range visible-to-UVC up-conversion within 240–410 nm has been achieved in Pr3+-doped glasses, revealing their potential advantage in different sophisticated disinfection technologies. The integrated emission intensity was studied as a function of light excitation power to assess a mechanism attributed to UVC luminescence. Especially, it was revealed that the multicomponent silicate glass qualities and praseodymium 3PJ excited state peculiarities are favorable to obtaining useful broadband ultraviolet up-converted luminescence. The glass dispersion qualities were determined between 450–2300 nm. The impact of praseodymium concentration on Vis-NIR spectroscopic glass qualities was evaluated employing absorption spectra, emission spectra, and decay curves of luminescence associated with two involved praseodymium excited states. Especially, efficient interionic interactions can be inferred by investigating the decrease in 1D2 state experimental lifetime in the heavily doped samples. Examination of absorption spectra as a function of temperature implied that excitation at 445 nm should be quite effective up to T = 625 K. Contrary to this, temperature elevation gives rise to a moderate lowering of the visible praseodymium luminescence. [ABSTRACT FROM AUTHOR]

Membranes produced by crosslinking chitosan with magnesium phytate were prepared using highly deacetylated chitosan and its N-carboxymethyl, O-carboxymethyl and N,O-carboxymethyl derivatives. The conditions of the membrane production were described. IR, Raman, electron absorption and emission spectra were measured and analyzed for all the substrates. It was found that O-carboxymethyl chitosan derivative is the most effectively crosslinked by magnesium phytate, and the films formed on this substrate exhibit good mechanical parameters of strength, resistance and stability. Strong O–H···O hydrogen bonds proved to be responsible for an effective crosslinking process. Newly discovered membrane types produced from chitosan and magnesium phytate were characterized as morphologically homogenous and uniform by scanning electron microscopy (SEM) and IR measurements. Due to their good covering properties, they do not have pores or channels and are proposed as packaging materials. [ABSTRACT FROM AUTHOR]

Novel ternary fluoro-germano-tellurite (GTS) glasses doped with Er3+ ions with 0.5 mol% and 1.0 mol% were fabricated by a conventional melt and quenching method and investigated using methods of optical spectroscopy. The room-temperature absorption spectrum was recorded and analyzed to determine radiative transition rates, radiative lifetimes, and branching ratios of Er3+ luminescence. Decay curves of Er3+ luminesccence were recorded and analyzed. Temperature dependences of emission spectra and absorption spectra in the region from RT (room-temperature) up to 675 K were studied in detail. The contribution of competing radiative and nonradiative processes to the relaxation of luminescent levels of Er3+ was assessed. Absolute and relative sensitivity were established utilizing the comprehensive model based on thermally coupled 2H11/2/4S3/2 excited states of erbium. The high quantum efficiency of the first erbium-excited state and value of gain coefficient indicate that GTS:Er glass system can be considered as conceivable NIR (near infrared) laser material as well. [ABSTRACT FROM AUTHOR]

We have investigated the spectroscopic properties of Er3+-doped fluorotellurite glasses with the basic molar composition 75%TeO2-10%P2O5-10%ZnO-5%PbF2, modified by replacing 5% TeO2 by a metal oxide, namely WO3 or Nb2O5. The absorption edge of the glasses studied has been described within the Urbach approach, while the absorption and photoluminescence spectra have been analyzed in terms of the standard Judd-Ofelt theory, along with the photoluminescence decay of the 4I13/2 and 4S3/2 levels of the Er3+ ion. The absorption and emission spectra of the 4I15/2 ↔ 4I13/2 infrared transition have been analyzed within the McCumber theory to yield the peak emission cross-section and figure of merit for the amplifier gain. It appears that the fluorotellurite glass containing WO3 as a modifier is characterized by the largest figure of merit, indicating this matrix as a promising new host for doping with Er3+ ions. [ABSTRACT FROM AUTHOR]

The electron absorption-, photoluminescence- and electron paramagnetic-resonance spectra of Mn3+ in red beryl from Wah Wah Mountains (Utah USA) and of pink- and purple vesuvianite from Jeffrey Mine (Asbestos, Canada) were measured at room- and low temperatures. The crystal field stabilization energies are equal to 130.9 kJ/mol for the red beryl, and 151.5-158.0 and 168.0 kJ/mol for for the pink- and the purple vesuvianite, respectively. The red photoluminescence of Mn3+ was not intensive either at room- or at low temperatures. The high Mn content in the crystals caused the emergence of an additional emission band and short photoluminescence-decay lifetimes. The latter are only 183 μs for beryl and 17 μs for vesuvianite. [ABSTRACT FROM AUTHOR]

Influence of temperature on spectroscopic and thermal properties of Tm 3+ and Er 3+ -doped GdVO 4 and LuVO 4 crystals was examined. Polarized absorption and emission spectra as well as excited state luminescence lifetimes have been measured and analyzed especially at cryogenic temperatures in the 1.5–1.6 μm and 1.8–1.9 μm spectral ranges to assess laser qualities of these materials. The emission cross sections for 4 I 132 → 4 I 15/2 (Er) and 3 F 4 → 3 H 6 (Tm) transitions at T = 77 K were determined and confronted to the results obtained at room temperature. Effective emission cross sections estimated for aforementioned erbium and thulium transitions indicate that effective laser operation at cryogenic temperatures can be achieved in the gadolinium and lutetium vanadate crystals. Efficiency of laser material depends on its ability to heat distribution upon high-power energy pumping process. Accordingly, it has been found that the anisotropy of thermal conductivity for the undoped crystals is weakly influenced by the temperature albeit conductivity values for the GdVO 4 are higher than those for LuVO 4 at all temperatures. Incorporation of erbium or thulium ions results in a decrease of thermal conductivity in the two vanadate crystals and an anomalous temperature dependence of thermal conductivity in the LuVO 4 was observed. Anisotropy of temperature dependence of thermal conductivity was found for the LuVO 4 :3.2 at%Tm 3+ crystal. In this case the thermal conductivity along c-axis is inferior to that along a-axis of the crystal. [ABSTRACT FROM AUTHOR]

Abstract: The selected glasses and glass–ceramics pertinent to following chemical composition in mol%:48%SiO2–11%Al2O3–7%Na2O–10%CaO–10%PbO–11%PbF2–3%ErF3 and 48%SiO2–11%Al2O3–7%Na2O–10%CaO–10%PbO–10%PbF2–1%ErF3–3%YbF3 have been manufactured from high purity components (Aldrich) at 1450°C in normal atmosphere. Glass optical fibers were successfully drawn. Subsequently they were subject to the heat-treatment at 700°C in various time periods. The preceding differential thermal analysis (DTA) studies allowed estimating both the fiber drawing temperature and the controlled crystallization temperature of glass fibers. It has been observed that the controlled heat-treatment of oxyfluoride glass fibers results in the creation of Pb5Al3F19, Er4F2O11Si3 and Er3FO10Si3 crystalline phases. The identified phases were characterized by X-ray powder diffraction (XRD) and confirmed by selected area electron diffraction (SAED). The fibers consist of mixed amorphous–crystalline microstructure with nano-crystals of size even below 10nm distributed in the glassy host. Their morphology was investigated applying high-resolution transmission electron microscopy. Optical properties and excited state relaxation dynamics of optically active ions (Er3+, Yb3+) in glass and glass–ceramics have been studied. Based on absorption spectra the Judd–Ofelt analysis was carried out. The main attention was directed to NIR luminescence at. 1.6μm related to 4I13/2 → 4I15/2 Er3+ and less effective emission associated with 4I11/2 → 4I15/2 Er3+ and 2F5/2 → 2F7/2 Yb3+ transitions. The dissimilar spectroscopic properties have been revealed for glasses and glass–ceramic samples, respectively. The reduction of emission linewidth at 1.6 and 1.0μm combined with substantial increase of 4I13/2 lifetimes of erbium in glass–ceramics appear to be evidences that Er3+ ions are accommodated in crystalline phases. The structural and optical characteristics of oxyfluoride glass–ceramic fibers indicate that these optical systems may be considered as promising materials for Er-doped optical amplifiers operating within third telecommunication window. [Copyright &y& Elsevier]

Abstract: Er3+-doped KCaY(VO4)2 microcrystalline samples were synthesized using a high temperature solid-state reaction technique. Spectroscopic properties of Er3+: KCaY(VO4)2 are studied and the nature of emissions is discussed. A strong green and infrared luminescence were observed under excitation at 314nm in the O2−→V5+ charge-transfer transitions and direct excitation of Er3+ ions at 435nm. A strong emission lines in the blue region are due to the transitions of VO4 3− ions have been observed at 77K. The Judd–Ofelt parametrization scheme has been applied to the analysis of the room temperature absorption spectra in order to evaluate the intensity parameters, the branching ratios and the radiative lifetimes of the 4I13/2, 4I11/2, 4F9/2 and 4S3/2 emitting levels. The effective cross-section has been calculated for the 4I13/2→4I15/2 transition, indicating that the title compounds is a promising active medium for application in the three-level laser system. The up-conversion emission in Er3+: KCaY(VO4)2 was investigated at 300K. The decay profiles of the Stokes and anti-Stokes emissions were measured and the mechanism of up-conversion luminescence is discussed. [Copyright &y& Elsevier]

Abstract: LaPO4 single crystals lightly doped with Er3+, and codoped with Er3+ and Yb3+ have been grown by spontaneous nucleation in a lead phosphate flux. Absorption and luminescence spectra have been measured in the visible and near-IR regions and the excited state dynamics has been studied upon pulsed laser excitation. The obtained results have allowed the evaluation of the effective emission cross-sections around 1.5μm, that have been found to be similar to important oxide laser crystals doped with Er3+. Efficient visible upconversion has been observed upon excitation at 980nm in the codoped crystals. This behaviour is attributed to Yb3+–Er3+ energy transfer processes. [Copyright &y& Elsevier]

Sc2SiO5:4 at. %Tm crystal was obtained by the Czochralski method and the crystal cell parameters were calculated. Sixfold coordinated Sc-ions occupied two different crystallographic sites but the low temperature optical spectra only represented energy transitions originating from Tm ions residing in one site. Room temperature absorption spectrum was analyzed in the framework of Judd–Ofelt theory and the calculated absorption coefficient and cross section were 10.47 cm-1 and 5.55×10-21 cm2 at 791 nm respectively. Stimulated emission cross sections for the 3F4–3H6 transition near 1900 nm were evaluated using the reciprocity method while the luminescence 3F4 lifetime was measured to be 1.14 ms. We conclude that Tm:Sc2SiO5 is promising for diode-pumped infrared lasers. [ABSTRACT FROM AUTHOR]

Abstract: Non hygroscopic U3+:KPb2Cl5 single crystals with a 0.1mol% U3+ nominal concentration and good optical quality have been obtained by the Bridgman–Stockbarger method. High-resolution absorption and emission spectra of the crystals were recorded at room temperature in the 4000–25000cm−1 and 4000–14000cm−1 spectral ranges, respectively. Excitation in the spectral region of 5f3 →5f26d1 transitions produced a strong near infrared emission from the 4F3/2 and 4I11/2 energy levels. A Judd–Ofelt intensity analysis has been performed in order to describe the electric dipole strengths of the observed transitions. The obtained phenomenological parameters were used to predict luminescence properties of U3+ ions doped in the KPb2Cl5 single crystal. [Copyright &y& Elsevier]

[Display omitted] • New compound 2-methyl-3,5-dinitro-6-(2-phenylhydrazinyl)pyridine was synthesized. • Its structure was studied using XRD, NMR, IR and Raman methods. • Electron absorption and emission spectra with femtosecond excitation were measured. • The experimental results were analysed in terms of DFT and NBO calculations. • The depopulation mechanism of electron excited states was proposed. A new methyl-dinitro-phenylhydrazinyl-pyridine derivative [2-methyl-3,5-dinitro-6-(2-phenylhydrazinyl)pyridine] was synthesised and characterised by means of structural and spectroscopic measurements. The X-ray diffraction studies revealed that the compound crystallises in the centrosymmetric monoclinic space group P 2 1 / n , with two symmetry-independent molecules in the asymmetric unit with Z = 8. Hydrazo bridge C-NH-NH-C links two fragments composed of phenyl ring and pyridine unit substituted with methyl and nitro groups. Such a structure was confirmed by 1H and 13C NMR studies as well as IR, Raman, UV–Vis, and emission spectra. The results were analysed using the quantum-chemical DFT calculations. The paper reports the vibrational characteristics and discusses dynamical properties of this moiety. The full set of the normal modes typical of the hydrazo bridge was identified and assigned to respective IR and Raman bands. The results of structural and spectroscopic studies were used to find the dependence between the conformation of the θ–NH-NH-ϕ system and its optic properties. The experimental UV–Vis and emission spectra were discussed in terms of the calculated singlet and triplet states that allowed assigning the unique spectral pattern originating from the electrons of the hydrazo-bridge system. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new compound 2-[(4-nitropyridine-3-yl)amino]ethan-1-ol N-oxide was synthesized. • Its structure was studied using XRD, IR and Raman methods. • Electron absorption and emission spectra with femtosecond excitation were measured. • The experimental results were analyzed in terms of DFT and NBO calculations. • The depopulation mechanism of electron excited states was proposed. A new nitropyridine amino N-oxide derivative 2-[(4-nitropyridine-3-yl)amino]ethan-1-ol N-oxide was synthesized and its structural and optical properties were described. Its structure obtained from the X-ray diffraction (XRD) studies was related to the Infrared spectroscopy (IR), Raman spectroscopy (RS), electron Ultraviolet–Visible spectroscopy (UV–VIS) and emission spectra measurements. The experimental results were analyzed in terms of theoretical data obtained from quantum chemical Density Functional Theory (DFT) and Natural Bond Orbital (NBO) calculations. The 6-311G(2d,2p) basis set with the B3LYP functional was used to discuss its optimized structure and vibrational properties. Femtosecond excitation was used to recognize the depopulation mechanism of the electron excited states in the studied compound. It was found that the intermolecular interactions strongly influence the physicochemical properties and application of the new nitropyridine amino N -oxide derivative. [ABSTRACT FROM AUTHOR]

We have investigated the spectroscopic properties of Er3+-doped fluorotellurite glasses with the basic molar composition 75%TeO2-10%P2O5-10%ZnO-5%PbF2, modified by replacing 5% TeO2 by a metal oxide, namely WO3 or Nb2O5. The absorption edge of the glasses studied has been described within the Urbach approach, while the absorption and photoluminescence spectra have been analyzed in terms of the standard Judd-Ofelt theory, along with the photoluminescence decay of the 4I13/2 and 4S3/2 levels of the Er3+ ion. The absorption and emission spectra of the 4I15/2 ↔ 4I13/2 infrared transition have been analyzed within the McCumber theory to yield the peak emission cross-section and figure of merit for the amplifier gain. It appears that the fluorotellurite glass containing WO3 as a modifier is characterized by the largest figure of merit, indicating this matrix as a promising new host for doping with Er3+ ions. [ABSTRACT FROM AUTHOR]

• New methyl-nitropyridine thione and its thiol tautomer was synthesized. • Crystal structure was determined. • IR and Raman spectra were measured and analyzed using DFT approach. • Electron absorption and emission spectra were studied. • Depopulation mechanism of the electron excited states was proposed. Theoretical and experimental studies of new 4-methyl-3-nitropyridine-2-thione and its thiol tautomer were synthesized and characterized by means of structural and spectroscopic studies. X-ray diffraction, IR, Raman, UV–VIS and emission spectra were measured and analyzed. The quantum chemical DFT calculations were applied in the analysis of the obtained results. The effect of the temperature change on the structural and spectroscopic properties was studied. The vibrational characteristics and dynamical properties of the ϕ-S-H and ϕ= S type compounds are discussed where ϕ is a heterocyclic ring. The results of structural and spectroscopic studies were used to find a diagnostic tool on the structure of thione and tiol forms and their optic properties. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, spectroscopic properties of (Lu 0.25 Gd 0.75) 2(1-x) Tm 2x SiO 5 (x = 0.04 and 0.005) single crystals were investigated. The material was found to be biaxial, exhibiting strong optical anisotropy, as clearly demonstrated in polarized absorption and emission spectra. Data from room temperature polarized absorption spectra were used in calculations within the phenomenological Judd-Ofelt model. The intensity parameters Ω t were established at Ω 2 = 3.24 (±0.58), Ω 4 = 2.96 (±0.24) and Ω 6 = 0.86 (±0.14) [10−20 cm2]. The values of fluorescence lifetimes of the 1D 2 and 1G 4 levels were measured and subsequently compared with those calculated using the Judd-Ofelt theory. The strong absorption bands located at wavelengths around 355, 460 and 790 nm, related to the 3H 6 → 1D 2 , 1G 4 , 3H 4 transitions, were found suitable for optical pumping of the investigated material. The characteristics of emission spectra recorded in the blue (ca. 455 nm) and IR (ca. 1750 nm) regions indicate that further investigations of stimulated emission within those wavelength ranges are well justified and can be considered promising. • Spectroscopic investigations of Tm doped (Lu 0.25 Gd 0.75) 2 SiO 5 single crystals were conducted. • Material shows high potential for lasing in IR region ca. 1900 nm. • Influence of Anisotropy and temperature on spectroscopic properties is reported. [ABSTRACT FROM AUTHOR]