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Structural, energetic and spectroscopic studies of new luminescent complexes based on 2-(2′-hydroxyphenyl)imidazo[1,2- <i>a</i> ]pyridines and 1,2-phenylenediboronic acid
摘要： Three new blue-luminescent complexes of selected imidazo[1,2-a]pyridine derivatives and 1,2-phenylenediboronic acid have been synthesized and structurally characterized using single-crystal X-ray diffraction. Additionally, the crystal structures of two of the (N,O)-donor compounds have been evaluated for the first time. The crystal packing and molecular motifs observed in the studied crystals have been thoroughly analysed, including computational studies, and are also discussed within the context of analogous systems reported in the literature. It appears that the new compounds form different crystal networks with regard to the asymmetric unit content and packing, although some similarities can be found. In all cases a typical centrosymmetric dimer bound via boronic acid groups is formed, characterized by an interaction energy of about -80 kJ mol-1, while the 2-(2'-hydroxyphenyl)imidazo[1,2-a]pyridine complex and its methoxy derivative form solvate structures, somewhat resembling the previously studied 8-oxyquinolinate analogues. As far as the spectroscopic properties are concerned, the lowest energy excitation observed in the studied complexes is based on the highest occupied molecular orbital–lowest unoccupied molecular orbital transition, and both these molecular orbitals are centred predominantly on the (N,O)-donor species according to the results of time-dependent density functional theory. Thus, the charge transfer observed for the 8-oxyquinolinate equivalents does not occur in these cases. Consequently, the spectroscopic behaviour of the series is very much comparable with that of the parent imidazo[1,2-a]pyridine derivatives, if the excited-state intramolecular proton-transfer process does not take place, as shown by the absorption and emission spectra collected in toluene and acetone solutions. Complexation causes a reduction in the Stokes shift compared with the respective (N,O)-donor molecules.
关键词： periodic calculations,TDDFT,UV–Vis spectroscopy,X-ray diffraction,time-dependent density functional theory,spectroscopic properties,luminescent boron complexes,transferred aspherical atom model (TAAM) refinement
更新于2025-09-23 15:22:29
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Effect of Eu3+ ions on optical and fluorescence studies of Nd3+ ions doped zinc-lithium fluoroborate glasses
摘要： Nd3+ single and Nd3+/Eu3+ co-doped ZnF2-LiF-Na2CO3-Bi2O3-H3BO3, zinc lithium fluoroborate (ZLFNBiB) glasses with good optical properties have been prepared by high temperature melt-quenching method. The single and co-doped samples exhibiting emission bands centered at 874, 1058 and 1330 nm under the excitation of 808 nm laser diode (LD). The photoluminescence spectra for co-doped glasses were recorded under the 394 and 464 nm of xenon lamp as excitation sources. The Judd-Ofelt intensity parameters were calculated from optical absorption spectrum and radiative parameters from the emission spectrum of 0.5 mol% of Nd3+ doped glass. The large stimulated emission cross-section and branching ratio values are evaluated and compared with the other Nd3+ doped systems, the energy transfer from Eu3+ to Nd3+ ions is observed and thoroughly discussed from NIR emission spectra (λexc = 394 nm) of co-doped glasses. The decay profiles are recorded for all the concentrations of co-doped samples and the experimental lifetimes (τexp) were obtained from the decay profiles. The binding energy and Urbach energy values of prepared glass samples were calculated and discussed.
关键词： Spectroscopic properties,Fluorescence,Energy transfer,Lifetime.,Nd3+/Eu3+-co-doped glasses
更新于2025-09-23 15:21:21
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Thermo-optic and spectroscopic properties of Yb:GAGG, Nd:GAGG and Nd:GGG laser materials at cryogenic temperature
摘要： The solid-state lasers provide an attractive approach to enhance the laser performance benefitting from significant improvements in both thermo-optic and spectroscopic properties of the gain mediums under cryogenic temperature. Here, thermo-optic properties of Yb:Gd3(AlxGa1-x)5O12 (Yb:GAGG) and Nd:Gd3(AlxGa1-x)5O12 (Nd:GAGG) laser crystals, including thermal conductivity (κ), thermal expansion coefficient (α) and specific heat at constant pressure (Cp) were measured from 77 to 298 K. In addition, the thermal shock resistance parameters were also calculated. The spectroscopic properties and the fluorescence lifetimes of laser gain mediums Yb:GAGG, Nd:GAGG and Nd:Gd3Ga5O12 (Nd:GGG) were characterized at 77, 150, 298 K. The stimulated emission cross sections of these laser materials were determined by use of the Füchtbauer-Ladenburg (FL) formula at each temperature.
关键词： GGG,cryogenic cooling,GAGG,spectroscopic properties,thermal properties,Neodymium,Ytterbium
更新于2025-09-19 17:13:59
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Metallic Nanomaterials (Part B) || 5. Size-controlled atomically precise copper nanoclusters: Synthetic protocols, spectroscopic properties and applications
摘要： Noble metal nanoclusters (NCs) are a new class of nanomaterials which are considered being a missing link between isolated metal atoms and metal nanoparticles (NPs). The sizes of the NCs are comparable to the Fermi wavelength of the conduction electrons, and this renders them to be luminescent in nature. They exhibit size-dependent fluorescence properties spanning almost the entire breath of the visible spectrum. Among all the noble metal NCs being explored, copper NCs (CuNCs) are the most rarely investigated primarily because of their propensity of getting oxidised. In this chapter, we have given a comprehensive understanding as to why these NCs are luminescent in nature. We have also given a detailed overview regarding the various templates used for the synthesis of these CuNCs along with the respective protocols being followed. The various instrumental techniques used to characterize these CuNCs are discussed which provides an in-depth understanding as to how these CuNCs can be properly examined. Finally, we have highlighted some of the most recent applications of these CuNCs which make them unique to serve as the next-generation fluorophores.
关键词： nano-thermometry,bio-imaging,sensing,synthetic protocols,instrumentations,spectroscopic properties,templates,luminescent nanoclusters
更新于2025-09-16 10:30:52
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Spectroscopic properties of Er:Lu2O3 crystal in mid-infrared emission
摘要： High optical quality Er3t doped Lu2O3 single crystal with optimum doping concentration was grown by Floating zone (Fz) method. The spectral properties and Judd-Ofelt (JO) analysis were reported. The emission cross-section at 2772 nm was calculated to be 2.47 ? 10?20 cm2 with FWHM of 188 nm. The fluorescence lifetime of 4I11/2 and 4I13/2 energy level was fitted to be 1.62 ms and 4.02 ms. Optimum lifetime ratio (τlow/τup) is beneficial to laser operation. Compared with reported Er3t doped crystal, the larger spectral quality factors Q and low inversion ratio P of 7 at.% Er:Lu2O3 crystal indicate that it has a favorable laser performance for 2.8 μm laser operation.
关键词： J-O theory,Er:Lu2O3,Mid-infrared,Spectroscopic properties
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Highly Efficient Laser Emission from a Novel Nd:LGSB Crystal
摘要： Infrared lasers at 1 μm are widely used in numerous industrial or medical applications, optical communication and spectroscopy. The lasers available nowadays are based on different laser active media, among which most common used are Nd:YAG, Yb:YAG, Nd:YVO4, or Nd:GdVO4, to mention few of them [1]. In addition, visible laser sources are obtained by using the infrared laser emission in conjunction with highly efficient nonlinear crystals. Furthermore, if the nonlinear crystal is doped with Nd3+ ions, then a compact, more efficient and lower-cost self-frequency conversion laser system could be realized. Thus, the research for finding new laser crystals or nonlinear crystals with prominent self-frequency doubling properties is of great interest in present, owing mostly to the need for up-scaling the existing laser systems. In this work we present our new findings with respect to Nd lasing at 1 μm, when it is inserted in LaGdSc(BO3)4 (LGSB) nonlinear matrix. The LGSB crystal doped with 5 at.% Nd3+ was grown by Czochralski pulling technique in our laboratory, the growth process being similar with that reported by Gheorghe et al. [2]. Worthy to be mentioned, the lasing in Czochralski-grown LGSB crystals was reported previously only for Yb trivalent ions [3]. First, the spectroscopic properties were determined for this laser medium. Thus, the negative uniaxial Nd:LGSB medium presents polarization selective absorption cross sections. Values of 5×10-20 cm2 (σ polarization) and 1.3×10-20 cm2 (π polarization) where measured for the absorption cross section at 807 nm. The determined emission cross sections were ~1.9×10-19 cm2 (π) and ~2×10-19 cm2 (σ). Laser experiments have been performed for two 5.0 at.% Nd:LGSB uncoated crystals: Nd:LGSB-1, length of 6.1 mm, c-cut and Nd:LGSB-2, 3.0-mm thickness, a-cut. The pump was done with a fiber-coupled diode laser (fiber with 100-μm diameter, NA= 0.22) in quasi-continuous wave (quasi-CW) mode (1-ms pump pulse at 10-Hz repetition rate), as well as in CW regime. A linear, 10-mm long plane-plane resonator was used in the experiments and various sizes of the pump-beam were considered. The laser pulse energy, Ep at 1062 nm yielded by Nd:LGSB-1 is shown in Fig. 1a) at a pump-beam diameter of 230 μm. Operation with high slope efficiency, ηsa= 0.67 was obtained; a maximum pulse energy Ep= 13.5 mJ was recorded for absorbed pump-pulse energy of 20.5 mJ (99% absorption efficiency, ηa). The power outputted from the same crystal, in CW operation, amounted to Pout= 1.3 W for Pabs= 2.1 W absorbed pump power; the slope efficiency was ηsa= 0.67 [Fig. 1b)]. The Nd:LGSB-2 crystal showed also a high ηsa= 0.63 slope; the CW power reached Pout= 0.75 W for Pabs= 1.6 W (absorption ηa= 0.74). Results on the polarization status, the laser beam transverse distribution and the influence of the pump-beam dimensions on the laser performances will be presented. These are the first results obtained from diode-pumped Nd:LGSB, showing very good performances at 1062 nm although uncoated laser crystals were employed in the present experiments.
关键词： Nd:LGSB crystal,spectroscopic properties,diode-pumped,Czochralski pulling technique,laser emission
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Comparative Study of Spectroscopic Properties of Pr <sup>3+</sup> -Doped LiY <sub/>0.3</sub> Lu <sub/>0.7</sub> F <sub/>4</sub> , LiYF <sub/>4</sub> and LiLuF <sub/>4</sub> Crystals
摘要： The most common host materials for visible lasers are the most common host materials for visible lasers due to their large energy bandgap and low phonon energies. Among the rare-earth ions, Pr3+ is very attractive for visible lasers due to its transitions in the blue, green, and red spectral regions. In this contribution, we report on the spectroscopic properties of Pr3+-doped LiY0.3Lu0.7F4, LiYF4 and LiLuF4 crystals. The investigated crystals were grown by the Bridgman-Stockbarger method. The content of the Pr3+ ions in the crystals was determined around 0.5 at.%, 1 at.%, 1.5 at.%, 2 at.% and 5 at.% by ICP-MS. Doped LiYF4 and LiLuF4 crystals possess higher segregation coefficients in contrast to LiY0.3Lu0.7F4, respectively. For more over, in the case of Pr3+ and Nd3+ ions, the mixed LiY0.3Lu0.7F4 crystal has higher segregation coefficient comparing to both LiYF4 and LiLuF4 crystals (1.5, 1.2). The optical absorption spectra were measured using an UV-VIS-NIR spectrophotometer. The Judd-Ofelt theory was applied to determine the intensity parameters Ωλ (λ = 2, 4, 6). It was determined that the intensity parameters of Pr3+ are 1.17.
关键词： Pr3+-doped,LiLuF4,visible lasers,LiY0.3Lu0.7F4,spectroscopic properties,LiYF4
更新于2025-09-11 14:15:04
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Investigation of modifier effect on the spectroscopic properties of Sm3+ ions in binary boro?bismuth glasses
摘要： Trivalent samarium (Sm3+)-doped boro?bismuth glass systems are prepared using the well-known melt quenching technique and studied their physical and spectroscopic properties. Theoretical optical basicity of the glasses are evaluated using the glass compositions. The optical absorption spectra are used to predict the optical band gap and bonding parameters of glasses. The ultra violet (UV) cutoff wavelength is increasing towards the higher wavelength side with increase in bismuth concentration. Judd-Ofelt parameters are obtained from absorption spectrum and are inturn used to estimate radiative properties for various excited states of the Sm3+ ions in boro?bismuth glasses. Luminescence decay curves of the 4G5/2 level in the Sm3+-doped boro?bismuth glasses are measured under 402 nm excitation. The decay times exhibit single exponential nature for lower concentrations (≤0.1 mol%) and tends towards non-exponential with increase in Sm3+ concentrations (≥0.5 mol %). The non-exponential decay curves of higher Sm3+-doped glasses are fitted to the Inokuti-Hiriyama model to know the nature of interaction for energy transfer between the Sm3+ ions. The chromaticity color coordinates for present glass systems are also evaluated and found that the luminescence color falls in the reddish-orange region.
关键词： Sm3+ ion,Judd-Ofelt theory,Spectroscopic properties,Decay curve analysis,Binary boro?bismuth glasses
更新于2025-09-10 09:29:36
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Spectroscopic characterization of orthorhombic δ-BiB3O6 phase nonlinear single crystal doped with Pr3+ ions
摘要： The spectroscopic properties of 1at % Pr3+ doped δ-BiB3O6 (BIBO) single crystal were investigated. The absorption, emission and excitation spectra were studied at low (10 K) and at room temperature, with the emission and absorption spectra showing clear polarization dependence. The strongest observed luminescence band corresponds to the 1D2 → 3H4 transition at 610 nm. Energy levels of Pr3+ in δ-BIBO host were assigned on the basis of low temperature absorption and emission measurements. The number of crystal field levels derived implies that Pr3+ ions are located in one crystal site in the BIBO host. Decay time of the praseodymium 3P0 emission was unusually short and the 1D2 decay was non-exponential. The modified Judd-Ofelt intensity formalism was used to analyze the experimental data. The ?λ parameters, branching ratios and electric dipole transition probabilities were determined. The stimulated emission cross-sections σ for the 5D0 → 3HJ transitions were also evaluated in this system.
关键词： Pr3+ spectroscopic properties,Pr3+ luminescence,Pr3+ ions in borate hosts,δ-BiB3O6,Judd-Ofelt formalism
更新于2025-09-09 09:28:46
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Synthesis of Fluorescent Core-Shell Metal Nanohybrids: A Versatile Approach
摘要： A ?exible way of fabricating core-shell noble metal-organic nanohybrids with tailored chemical and spectroscopic properties is proposed here. The synthetic protocol consists of a multi-step procedure able to guarantee acceptable reproducibility of core size and shape as well as control of the organic outer layer. The proposed method highlights limitations in obtaining highly controllable products, although the heterogeneity degree of the nanostructures is in line with that expected from bottom-up approaches in solution. Selective functionalization of the nanohybrids with properly-substituted ?uorescent dyes under variable experimental conditions allowed the preparation of composite systems of tunable spectroscopic properties to be employed as nanoprobes in sensing or photonic applications. To this end, preliminary investigation on embedding the nanohybrids in compatible polymeric matrices is also reported.
关键词： polymeric matrix,spectroscopic properties,core-shell architecture,noble metal nanoparticles,self-assembly
更新于2025-09-04 15:30:14