Absorption spectrum of Yb3+(4f13) IN[(C6H5)3PH]3 YbCl6

Optical absorption spectra taken at 300 and 77 K are reported for six-fold octahedrally coordinated Yb³⁺(4f¹³) in [(C₆H₅)₃PH]₃ YbCl₆. In addition to vibronic spectra we observe electronic transitions which suggest that inversion symmetry is lifted by a small distortion similar to that reported for the Nd³⁺(4f³) spectrum of the corresponding salt. The vibronic as well as the electronic transition have been analyzed on the basis of six-fold octahedral symmetry. The analysis appears reasonable and consistent in comparison with other rare-earth ions that have been studied in similar cubic and octahedral environments.     

Spectroscopic properties of Nd ions in nano-perovskite CaTiO3

In this work, we present for the first time the spectroscopic properties of perovskite nanocrystals CaTiO₃: Nd³⁺, measured at room and liquid nitrogen temperature. Samples were prepared by the sol–gel method and annealed at 700 and 1000 °C. The concentration of Nd³⁺ ranged from 0.5% to 5%. Average nanocrystallite size primarily depends on the annealed temperature and is about 25 and 50 nm for 700 and 1000 °C, respectively. The absorption, emission and excitation spectra (monitored at 1078 nm) as well as the decay time profile of the emission from the ⁴F_3/2 energy level of Nd³⁺ are obtained. The increasing amount of Nd³⁺ ions decreases the lifetime of the ⁴F_3/2 level and that changes from 146 μs for 0.5% to 50 μs for 5% of Nd³⁺ concentration. The strongest emission was observed at two regions: 1050–1120 nm and 865–930 nm and was assigned to the ⁴F_3/2→⁴I_11/2 and ⁴F_3/2→⁴I_9/2 transitions, respectively. The spectroscopic quality parameter of neodymium in the CaTiO₃ lattice has been calculated from the emission spectra. The influence of luminescent properties depending on the annealing temperature and concentration of neodymium ions is discussed.     

Photophysical and Complexation Behavior of (4-Dimethylamino-benzylidene)-(4,6-dimethyl-pyrimidin-2-yl)-amine

The absorption and fluorescence characteristics of (4‐dimethylamino‐benzylidene)‐(4,6‐dimethyl‐pyrimidin‐2‐yl)‐amine (SB) have been investigated in different solvents. Both the absorption and emission spectra of SB exhibit red shifts as the solvent polarity increases. This indicats a change in dipole moment of molecules upon excitation as a result of intramolecular charge transfer interaction. The fluorescence quantum yield depends strongly on the properties of the solvents, which was discussed on the bases of positive and negative solvatokinetic effects. The effect of some divalent transition metal ions such as Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Hg²⁺on the absorption and fluorescence spectra of SB is also investigated. The results were consistent with formation of highly colored metal‐ SB complex which is responsible for the extreme quenching of the fluorescence of SB. The variations of both the formation constant of the complex and Stern‐Volmer constant were correlated with the electronic structure of the used metal ion.     

Sol-Gel Synthesis of Nd3+-Doped GeO2 Glasses and Their Optical Properties

Transparent Nd³⁺-doped GeO₂ bulk gels and glasses were prepared by the sol-gel method, and their thermal and spectroscopic properties including electron spin resonance (ESR), absorption, fluorescence and upconversion fluorescence spectra were investigated. Absorption spectra characteristic of Nd³⁺ ions were clearly observed. Under 805 nm laser excitation, the glass showed upconversion fluorescence at 362, 389, 421, 430, 470, 534, 600, and 662 nm at room temperature.     

Nd3NCl6 und Nd4NS3Cl3: Zwei Neodymnitrid‐Derivate mit diskreten Einheiten kantenverknüpfter ([N2Nd6]12+) bzw. isolierter [NNd4]9+‐Tetraeder

Nd₃NCl₆ and Nd₄NS₃Cl₃: Two Derivatives of Neodymium Nitride with Discrete Units of Edge‐Shared ([N₂Nd₆]¹²⁺) and Isolated [NNd₄]⁹⁺ Tetrahedra, respectively For the preparation of Nd₃NCl₆ (orthorhombic, Pbca; a = 1049.71(8), b = 1106.83(8), c = 1621.1(1) pm; Z = 8) and Nd₄NS₃Cl₃ (hexagonal, P6₃mc; a = 922.78(6), c = 683.06(4) pm; Z = 2) elemental neodymium is reacted with sodium azide (NaN₃), neodymium trichloride (NdCl₃) and in the case of Nd₄NS₃Cl₃ additionally with sulfur in evacuated silica tubes at 750 °C (Nd₃NCl₆) and 850 °C (Nd₄NS₃Cl₃), respectively. Thereby the hydrolysis‐sensitive nitride chloride forms coarse, brick‐shaped single crystals, while those of the insensitive nitride sulfide chloride emerge hexagonally and pillar‐shaped. The pale violet compounds each exhibit [NNd₄] tetrahedra as characteristic structural features, which are connected via a common edge to form discrete pairs of tetrahedra ([N₂Nd₆]¹²⁺) in Nd₃NCl₆ and are present in Nd₄NS₃Cl₃ even as isolated [NNd₄]⁹⁺ units. Their three‐dimensional cross‐linkage as well as the charge‐balance regulation proceed solely through Cl^– anions in the nitride chloride, but through equimolar amounts of S^2– and Cl^– anions in the nitride sulfide chloride. The crystal structure of Nd₃NCl₆ shows three crystallographically independent Nd³⁺ cations, each of which is eightfold coordinated by anions (Nd1: 2 N^3– + 6 Cl^–; Nd2 and Nd3: 1 N^3– + 7 Cl^–). Only two different kinds of Nd³⁺ underlie the structure of Nd₄NS₃Cl₃: Nd1 is surrounded by one N^3–, six S^2– and three Cl^– with CN = 10, whereas one N^3–, four S^2– and three Cl^– only are coordinating Nd2 with CN = 8.     

Preparation and Optical Properties of Submicron SiO2 Spheres Doped with YAG:Nd3+ Nanocrystallites

The sol-gel technology has been applied to obtain SiO₂ spheres of submicron size. The spheres have been doped with YAG:Nd³⁺ nanocrystallites. The nanocrystallites have been obtained from aqueous solutions of citric acid, yttrium, aluminum and neodymium chlorides. The obtained gels have been heated up to 800°C. Emission spectra as well as the excited state lifetimes have been measured at room and liquid nitrogen temperatures. The structural characterization has been performed by means of transmission and scanning electron microscopies (TEM, SEM) and powder diffraction (XRD) measurements. We have observed that the YAG:Nd³⁺ nanocrystallites demonstrate pronounced dependence of the emission intensities on the excitation power as compared to the YAG:Nd³⁺ crystallites embedded into the submicron SiO₂ spheres. The results suggest that silica spheres/YAG:Nd³⁺ composites are expected to be good hosts for microlaser systems.     

Optical absorption spectra of an aqueous frozen solution of neodymium chloride at various temperatures and pressures

A dilute aqueous solution of neodymium chloride NdCl₃ has been taken through two thermodynamic cycles along transformations with varying pressure (between 1 bar and 3.3 kbar) and temperature (between 300 K and 77 K). The characteristic optical line absorption spectrum which shows a Stark splitting of the Nd³⁺ electronic levels due to a quasi-crystalline surrounding of the ions appears only in that part of the cycles where pure ice I_h phase would be present. In any other part of the cycles where pure ice phases II, III, IX and I_C would be present such a phenomenon does not exist. It is shown that ice I_h may constitute a frame for neodymium aquo-ions.     

Synthesis,Structure and Photoluminescent Properties of [C6N2H14][Nd2(C2O4)2(SO4)2(H2O)4]·H2O,a New Organically Templated Neodymium(III) Oxalate‐sulfate

An organically templated neodymium oxalate–sulfate [C₆N₂H₁₄][Nd₂(C₂O₄)₂(SO₄)₂(H₂O)₄]·H₂O ( 1 ) has been synthesized under hydrothermal conditions and structurally characterized by single‐crystal X‐ray diffraction analysis. In 1 , the neodymium(III) ions are interconnected through oxalate and sulfate groups to form a neodymium oxalate–sulfate hybrid structure. A luminescence spectrum of 1 was recorded, and the luminescence decay time was also measured.     

Spectral migration of excitation energy among Nd3+ ions in fluoroarsenate glasses

In this work, we have investigated the existence of energy transfer among Nd³⁺ ions in fluoroarsenate glasses of the Na₄As₂O₇, BaF₂, YF₃ system with different Nd³⁺ concentrations (0.5, 2, 3, 4, and 5 mol%) by using time-resolved fluorescence line narrowing spectroscopy. The spectral features of the time resolved fluorescence line narrowing ⁴F_3/2→⁴I_9/2 emission spectra obtained under resonant excitation reveal the existence of spectral migration of excitation among the Nd³⁺ ions. The analysis of the time evolution of the ⁴F_3/2→⁴I_9/2 narrowed emission shows that the electronic mechanism responsible for the ion–ion interaction can be identified as a dipole–dipole energy transfer process.     

Near-infrared cell-permeable Hg2+-selective ratiometric fluorescent chemodosimeters and fast indicator paper for MeHg+ based on tricarbocyanines

Three tricarbocyanine dyes (IR‐897, IR‐877, and IR‐925) with different thiourea substituents that function as dosimeter units through specific Hg²⁺‐induced desulfurization have been demonstrated in a fast indicator paper for Hg²⁺ and MeHg⁺ ions. In comparison with available Hg²⁺‐selective chemodosimeters, IR‐897 and IR‐877 show several advantages, such as convenient synthesis, very long wavelengths falling in the near‐infrared (NIR) region (650–900 nm) with high molar extinction coefficients, a ratiometric response, and quite low disturbance with Ag⁺ and Cu²⁺ ions. They exhibit large redshifts, which result in a clear color change from deep blue to pea green that can be easily monitored by the naked eye for a convenient indicator paper. In emission spectra, they display a characteristic turn‐off mode at 780 nm and turn‐on mode at 830 nm with titration of Hg²⁺ ions. Remarkably, the signal/noise (S/N) ratio with other thiophilic metal ions (Ag⁺ and Cu²⁺) is greatly enhanced with ratiometric measurement of two channels: excitation spectra mode (I_{810 nm}/I_{670 nm}, monitored at 830 nm) and emission spectra mode (I_{830 nm}/I_{780 nm}, isosbestic absorption point at 730 nm as excitation). The distinct response is dependent upon the electron‐donating effect of the thiourea substituents; that is, the stronger the electron‐donating capability of the thiourea substituents, the faster the Hg²⁺‐promoted cyclization. Additionally, experiments with living SW1116 cells show that these three tricarbocyanine dyes with low toxicity can exhibit special characteristics that are favorable for visualizing intracellular Hg²⁺ and MeHg⁺ ions in biological systems, including excellent membrane permeability, minimal interfering absorption and fluorescence from biological samples, low scattering, and deep penetration into tissues.     

Absorption and emission spectra in chalcogenide glass of the composition 0.7Ga2S3·0.27La2S3·0.03Nd2S3

Chalcogenide glasses of the composition 0.7Ga₂S₃·0.27La₂S₃·0.03Nd₂S₃ doped by 3 mol% of Nd³⁺ were prepared. The absorption and emission spectra of these glasses were compared to those of commercial ED-2 3.1 wt.% Nd-doped silicate glass. The absorption intensities of Nd³⁺ in chalcogenide glass are higher than in silicate glass due to the increasing covalency of Nd³⁺ in these glasses. Because of the low phonon frequency of the chalcogenide glasses nonradiative relaxations from the ⁴F_{$\text{5}\text{2}$}, ²H_{$\text{9}\text{2}$} to the ⁴F_{$\text{3}\text{2}$} are lower than in other oxide glasses and so fluorescence from this state is observed.     

Zur Dimorphie von Nd3Cl[SiO4]2

On the Dimorphism of Nd₃Cl[SiO₄]₂ On reacting NdCl₃, Nd₂O₃, and SiO₂ (molar ratio: 1 : 4 : 6) at 850 °C in evacuated silica tubes, pale violet, hydrolysis resistant neodymium(III) chloride ortho‐silicate Nd₃Cl[SiO₄]₂ can be obtained within seven days. If equimolar amounts of NaCl are added as flux, rod‐ or platelet‐shaped, transparent single crystals of two modifications accumulate simultaneously. The one with the higher density (A‐Nd₃Cl[SiO₄]₂) crystallizes monoclinically (C2/c, no. 15; a = 1416.6(1), b = 638.79(6), c = 872.21(9) pm, β = 98.403(7)°; V_m = 117.55 cm³/mol, Z = 4), whereas the one with the lower density (B‐Nd₃Cl[SiO₄]₂) exhibits orthorhombic symmetry (Pnma, no. 62; a = 709.36(7), b = 1815.7(2), c = 631.48(6) pm; V_m = 122.45 cm³/mol, Z = 4). Two crystallographically independent Nd³⁺ cations exist in each of both crystal structures, which in the A type are surrounded by nine (1 Cl^– + 8 O^2–) and ten (2 Cl^– + 8 O^2–), whilst those in the B type by only two times eight (1 Cl^– + 7 O^2– and 2 Cl^– + 6 O^2–) anions, respectively. Thereby all oxygen atoms of both forms represent members of discrete ortho‐silicate tetrahedra ([SiO₄]^4–). Although both crystal structures are built of alternating anionic double layers {(Nd1)₂[SiO₄]₂}^2– and cationic single layers {(Nd2)Cl}²⁺, there is a higher cross‐linkage of the building units in the A‐type lattice, where the cations are coordinated by three and four tetrahedra edges of ortho‐silicate anions, compared to only two times two of them in the B type. From this an about 4% higher density of Nd₃Cl[SiO₄]₂ results for the A‐type structure (D_x = 5.55 g/cm³) in comparison with B‐type Nd₃Cl[SiO₄]₂ (D_x = 5.33 g/cm³).     

Synthesis and Infrared Multi‐band Absorption Properties of Core‐shell NaYF4:Yb3+, Er3+@SiO2 Nanoparticles

Due to the unique size effects, nanomaterials in infrared absorption have attracted much attention for their strong absorption in the infrared region. To achieve the infrared multi‐band absorption, we propose to synthesize a core‐shell structure nanomaterial consisting of NaYF₄:Yb³⁺, Er³⁺ core and a layer of SiO₂ as shell. A series of NaYF₄:Yb³⁺, Er³⁺ nanocrystals were synthesized through hydrothermal method by adjusting the ratio of citric acid(CA)‐to‐NaOH, and the effects of CA concentration, and NaOH concentration were studied in detail. NaYF₄:Yb³⁺, Er³⁺@SiO₂ nanoparticles were synthesized by sol‐gel method using TEOS as silica source. The results show that the core‐shell NaYF₄:Yb³⁺, Er³⁺@SiO₂ nanoparticles were successfully synthesized. Up‐conversion spectra of these nanoparticles were recorded with 980 nm laser excitation under room temperature. There are no changes of the emission centers of nanoparticles before or after silica coating, but the emission intensities of nanoparticles after silica coating are weakened. Furthermore, the property of infrared multi‐band absorption was tested through ultraviolet‐visible‐near infrared spectrophotometer and infrared absorption spectra. The results illustrate that the multi‐band infrared absorption nanomaterial was successfully synthesized.     

Correlation between the O 2p Orbital and Redox Reaction in LiMn0.6Fe0.4PO4 Nanowires Studied by Soft X‐ray Absorption

The changes in the electronic structure of LiMn_0.6Fe_0.4PO₄ nanowires during discharge processes were investigated by using ex situ soft X‐ray absorption spectroscopy. The Fe L ‐edge X‐ray absorption spectrum attributes the potential plateau at 3.45 V versus Li/Li⁺ of the discharge curve to a reduction of Fe³⁺ to Fe²⁺. The Mn L ‐edge X‐ray absorption spectra exhibit the Mn²⁺ multiplet structure throughout the discharge process, and the crystal‐field splitting was slightly enhanced upon full discharge. The configuration‐interaction full‐multiplet calculation for the X‐ray absorption spectra reveals that the charge‐transfer effect from O 2p to Mn 3d orbitals should be considerably small, unlike that from the O 2p to Fe 3d orbitals. Instead, the O K‐edge X‐ray absorption spectrum shows a clear spectral change during the discharge process, suggesting that the hybridization of O 2p orbitals with Fe 3d orbitals contributes essentially to the reduction.     

Parametric analysis of the energy levels of Nd3+ in frozen dilute aqueous solutions of neodymium chloride

A parametric analysis of the Stark-split spectra of Nd³⁺ in frozen dilute aqueous solutions of neodymium chloride has been carried out.The similarity of the spectra of Nd³⁺ in frozen dilute solutions and in crystals, where the ion is nine-fold coordinated and of approximate D_3h symmetry (Nd³⁺: LaCl₃, neodymium ethylsulfate and bromate), was used to obtain initial parameter values. Simultaneous diagonalization of the free ion and crystal field hamiltonians resulted in a r.m.s. deviation σ of 11 cm^?1 for 50 levels. The resulting crystal field parameters are B²₀ = 278 ± 19, B⁴₀ = ?201 ± 39, B^b₀ = ?946 ± 55 and B⁶₆ = 663 ± 43 cm^?1. Selection rules for D_3h are approximately obeyed. The small value of σ, the number of levels accounted for and the fact that the final parameters are not very different from those in the crystals indicate a nine-fold coordination of approximate D_3h symmetry for Nd³⁺ in frozen aqueous solutions. The spectra of liquid solutions show by their similarity to the spectra of frozen solutions that the same surroundings exist in the liquid.     

Homogeneity range of neodymium manganite in air

The solubility boundaries for Nd₂O₃ and manganese oxides in NdMnO_{3 ± δ} have been determined by X-ray powder diffraction analysis of homogeneous phases and heterogeneous compositions of the general formula Nd_{2 ? x} Mn _x O_{3 ± δ} (0.90 ≤ x ≤ 1.20; Δx = 0.02) prepared by ceramic technology from constituent oxides in air in the temperature range 900–1400°C. The results are presented in the form of a fragment of the Nd-Mn-O phase diagram in air. It is suggested that the Nd₂O₃ solubility in NdMnO_{3 ± δ} is due to crystal defects and the solubility of manganese oxides is in addition due to the disproportionation reaction 2Mn³⁺ = Mn²⁺ + Mn⁴⁺ and the subsequent partial substitution of divalent for tervalent manganese ions in the cuboctahedral positions of the perovskite-like crystal lattice. To verify this suggestion, it is necessary to systematically study the oxygen nonstoichiometry δ in Nd_{2 ? x} Mn _x O_{3 ± δ} as a function of x and synthesis temperature and structurally study this oxide with these parameters being varied.     

Radiation-chemical yield of excited neodymium(III) ions in phosphorus oxychloride-based aprotic binary solvents

Results of measurements of the yield of radioluminescence photons from Nd³⁺ ions in POCl₃-SnCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ and POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions upon homogeneous excitation by uranium α-particles are presented. It was found that the radioluminescence intensity corresponding to the³ F _3/2 →⁴ I _11/2 transition of neodymium ions depends on the solvent composition. The radiation-chemical yield of excited Nd³⁺ ions is proportional to the neodymium concentration, being (1.50 ±0.05) and (0.23 ±0.02) excited ions per 100 eV in POCl₃-SnCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ and POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ systems, respectively, at [Nd³⁺] = 0.4 mol/l.     

Water-soluble heteroligand complexes of 2-methyl-4-oxo-4H-pyran-3-olatoneodymium(III) with amino acids

New water-soluble heteroligand complexes of 2-methyl-4-oxo-4H-pyran-3-olatoneodymium(III) with aliphatic amino acids (glycine, N-methylglycine, and alanine) have been prepared. Within the biological “transparency window” (700–900 nm) of their electronic absorption spectra, narrow bands of Nd³⁺ are found: ⁴F_7/2 ← ⁴I_9/2; ⁴F_5/2 ← ⁴I_9/2; ⁴F_3/2 ← ⁴I_9/2 (750, 810, and 880 nm). Such complexes can be used as markers for biological tissues visualization.