Luminescence Of Nd3 Research Articles

Visible and Near-Infrared Luminescence of Lanthanide-Containing Dimetallic Triple-Stranded Helicates: Energy Transfer Mechanisms in the SmIII and YbIII Molecular Edifices

Dy, Yb) are determined in water and D2O solutions, and energy transfer processes are modeled for Sm III . The luminescence of Nd III ,S m III , and Yb III is sensitized by (L C -2H) 2- , but the energy transfer from the ligand to the Ln III ions is not complete, resulting in residual ligand emission. The luminescence of the Nd III helicate is very weak due to nonradiative de-excitation processes. On the other hand, the Yb III and Sm III helicates exhibit fair quantum yields, 1.8% and 1.1% in deuterated water, respectively. The energy transfer rates between (L C -2H) 2- and Sm III levels are calculated by direct and exchange Coulomb interaction models. This theoretical modeling coupled to numerical solutions of the rate equations leads to an estimate of the emission quantum yields in H2O and D2O, which compares favorably with experimental data. The main component of the ligandto-metal energy transfer (97.5%) goes through a 3 ﷿﷿* f 5 G5/2 (1) path, and the operative mechanism is of the exchange type. For the Yb III helicate, minor effects of oxygen on the sensitization of Yb III and nanosecond time-resolved spectroscopy point to the energy transfer mechanism being consistent with a recently proposed pathway involving fast electron transfer and Yb II . No up-conversion process could be identified. Ligand-field splitting of the 2 F5/2 (3E1/2 + E3/2) and 2 F7/2 (2E1/2 + E3/2) levels of Yb III is consistent with D3 symmetry.

Concentration effect on the up-conversion luminescence of neodymium activated calcium gallium germanium garnet crystal

In this work, we report on the infrared (pump) to visible luminescence of Nd 3+ ion in Ca 3Ga 2Ge 3O 12 for different Neodymium concentrations. Three visible structured emission bands centred at 541, 601 and 677 nm are observed, which are related to emissions mainly from the excited state 4G 7/2. The relative intensity between the red band (677 nm) and the other bands changes with both concentration and excitation intensity for Nd 3+ contents >2 at.%. In addition, a new up-conversion emission band in the blue region (centred about 460 nm) was detected in these samples. These results can be explained because of a pump induced thermalisation of the 4G 11/2 excited state from which additional emissions appear.

Upconversion processes in Nd 3+-doped fluoroarsenate glasses

In this work we have studied the infrared to visible upconversion luminescence of Nd 3+-doped fluoroarsenate glasses with different neodymium concentrations (0.1, 0.5, 2, 3, 4, and 5 mol%) under continuous wave and pulsed laser excitation. Green, orange, and red emissions are observed with excitation at 802 and 874 nm within the 4F 5/2 and 4F 3/2 levels. In addition, a weak blue emission appears under continuous wave (cw) laser excitation which under pulsed laser excitation only occurs for the most concentrated sample at 77 K. The green, orange, and red emissions can be attributed to transitions from the 4G 7/2 excited state. The pump power dependencies of these upconverted emissions together with the shape of the upconverted excitation spectra which are similar to the one-photon absorption spectrum and the temporal behavior of the decays, indicate that an ETU process seems to be responsible for the observed visible luminescence, though other possible mechanisms cannot be disregarded.

Remarkable luminescence of novel Nd(III) complexes with low-vibrational hexafluoroacetylacetone and DMSO-d 6 molecules

The structure of the Nd(III) complex with deuterated hexafluoroacetylacetone, Nd(HFA-D) 3(D 2O) 2, in DMSO-d 6 was investigated since the system gave a remarkable luminescence. The emission rate, Judd–Ofelt analysis, EXAFS, NMR and electrospray mass spectra suggested that the system should have the symmetrical bulky shell of six inner coordinating DMSO and three outer coordinating HFA molecules. This conjectured 12-coordinate structure with low-vibration C–D and C–F bondings and bulky shell well rationalized the enhanced emission of the Nd(HFA-D) 3(D 2O) 2 in DMSO-d 6. The incorporation of the Nd(HFA-D) 3/DMSO-d 6 system into the methacrylate polymers was successfully attempted. Use of the polymethacrylate with low percentage of C–H bonds, i.e., P-FiPMA (polyhexafluoroisopropylmethacrylate) gave remarkable luminescence of Nd(III) in the organic polymer matrix.

Photosensitized luminescence of novel β-diketonato Nd(III) complexes in solution

Photosensitized luminescence in the near-infrared region of five low vibrational β–diketonato neodymium(III) complexes, tris(1,1,1,5,5,5-hexafluoroacetylacetonato)neodymium(III) (1), tris(4,4,5,5,5-pentafluoro-1-pentafluorophenyl-1,3-pentanedionato)neodymium(III) (2), tris(4,4,5,5,6,6,6-heptafluoro-1-pentafluorophenyl-1,3-hexanedionato)neodymium(III) (3), tris(4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-pentadecafluoro-1-pentafluorophenyl-1,3-decanedionato)neodymium(III) (4), and tris[bis(pentafluorobenzoyl)methanato]neodymium(III) (5), were examined by the selective excitation of the ligand moieties in THF-d8. The intramolecular energy transfer efficiencies from the excited ligands to the central Nd(III) ion were determined and the order of 1<2<3<4<5 was obtained. The order of the overlap area between the phosphorescence due to the ligand moieties and the absorption due to Nd(III) in the 400–650 nm spectral region was also increased in the above order. These results suggest that the energy matching of the donor and the acceptor is decisive for the efficient photosensitized luminescence of Nd(III) complexes.

Luminescence of Nd 3+ complexes with some asymmetric ligands in organic solutions

A novel Nd 3+ complex, Nd(POA-D) 3, with asymmetric ligands (POA: perfluorooctanoylacetic acid), was synthesized in order to enhance the transition probability in its f–f transition by reducing symmetry of the ligand field around Nd 3+. This complex gives the 2.5 times higher oscillator strength of the hypersensitive transition in methanol- d 4 than the corresponding symmetrical complex, Nd(POM-D) 3 (POM: bisperfluorooctanoylmethane). The Stark splitting of the emitting level of Nd(POA-D) 3 was observed and the Judd-Ofelt analysis gave a large Ω 2 value, clearly showing the asymmetric environment around Nd 3+. 13C NMR analysis, molecular orbital and molecular mechanics calculations and EXAFS analysis suggest that the asymmetric environment achieved in Nd(POA-D) 3 is ascribed mainly to the asymmetric distribution of electrons on the coordinating O atoms. The higher absorption coefficient of Nd(POA-D) 3 leads to 1.86 times stronger emission than Nd(POM-D) 3 when measured at the common concentration and conditions. It is stressed that introduction of asymmetric ligands is a promising way for promoting emission of Nd 3+ in solutions when coupled with replacement of C–H bonds with C–D and C–F in the ligands.

Strategies for enhancing photoluminescence of Nd3+ in liquid media

The excited state ( 4 F 3 2 ) of Nd 3+ readily undergoes radiationless energy transfer via vibrational excitation of surrounding medium and dipole-dipole energy transfer via cross relaxation and energy migration, which makes it difficult to observe luminescence of Nd 3+ in a liquid matrix. In order to suppress such de-excitation of the 4 F 3 2 state, two kinds of ß-diketonato ligands which have no CH and OH bonds having high vibrational frequency were successfully designed for observing luminescence of Nd 3+ in a liquid matrix. Luminescence of Nd 3+ was observed for the first time by using deuterated tris-(hexafluoroacetylacetonato) neodymium(III), Nd(HFA-D) 3 , in deuterated organic solvents. The luminescence intensity, lifetime and quantum yield of the complex were measured in methanol-d 4 , acetone-d 6 , THF-d 8 , DMF-d 7 and DMSO-d 6 . Deuterated tris(bis-(perfluorooactanoyl)methanol)neodymium(III), Nd(POM-D) 3 , gave enhanced luminescence in DMSO-d 6 by minimizing energy migration during diffusional collisions in the liquid matrix. The intensity was independent of concentration in the micromolar range from 0.01 to 0.07M. The bulky perfluoroalkyl groups in the ligands effectively prevented de-excitation via vibrational excitation and cross relaxation in liquid media.

Enhancement of luminescence of Nd 3+ complexes with deuterated hexafluoroacetylacetonato ligands in organic solvent

Tris-(hexafluoroacetylacetonato)neodymium(III), [Nd(HFA-D) 3], was prepared by chelation of Nd 3+ ion with deuterated hexafluoroacetylacetone in CD 3OD. Luminescence of the Nd 3+ complex was observed for the first time in organic solvents and the quantum yield was estimated to be of the order of 10 −2 in deuterated acetone solution. The absorption spectrum of [Nd(HFA-D) 3] dissolved in acetone was comparable with that of Nd 3+ ion in Y 3Al 5O 15 matrix (Nd:YAG). Splitting of the 4 F 3 2 level was determined to be 82.3 cm −1 in this system. These spectral characteristics suggest that the physical nature of Nd 3+ coordination environments should be uniform and well defined by coordination of HFA in solution.

Nd 3+ optical multisites in the Ca 3(Nb,Ga) 2Ga 3O 12 laser garnet crystal

Laser excited site-selective luminescence of Nd 3+ ion in the Ca 3(Nb,Ga) 2Ga 3O 12 garnet crystal has been investigated for the 4 F 3 2 → 4 I 11 2 and 4 F 3 2 → 4 I 9 2 transitions. Six main non-equivalent crystal field sites were detected in the garnet. The crystal splitting scheme of the 4 F 3 2 and 4 I 9 2 manifolds was obtained for each Nd 3+ site. Energy transfer between Nd 3+ sites was observed by using time resolved spectroscopy.

The Luminescence of Nd3+ in the Polymorphic Perovskites Ba6B2W3O18 (B = Gd, Lu, Y). A Case with a Low-Lying Charge Transfer Transiton

By activation of the host Ba6B2W3O18 (B = Gd, Y, Lu) with Nd3+ an intense, unusual low-lying absorption band within the band gap is observed. A correlation to Jolrgensen's refined spin-pairing theory predications allows one to ascribe this band to a charge transfer transition ending onto 4f orbitals. In the case of Yb3+ activation of 18R-Ba6Y2W3O18 an absorption band of similar type is found as well. Bei Aktivierung des Wirtsgitters Ba6B2W3O18 (B = Gd, Y, Lu) mit Nd3+ tritt eine intensive, ungewohnlich energiearme Anregungsbande innerhalb der verbotenen Zone auf. Durch Korrelie-rung mit den Voraussagen der verfeinerten Spin-Paarungs-Theorie von Jolrgensen kann diese Bande einem Charge-transfer-Ubergang zu 4f-Orbitalen zugeordnet werden. Im Falle des Yb3+-aktivierten 18R-Ba6Y2W3O18 wird eine Absorptionsbande des gleichen Typs beobachtet.

Concentration quenching in Nd 3+ stoichiometric materials

Basic experimental facts concerning the luminescence of Nd x La 1− x P 5O 14 are reviewed. Interpretation of the data by a diffusion model leads to the possible presence of ∼ 10 17 cm -3 energy sinks in this material. Consequences and weaknesses of this model are discussed.

Absorption and luminescence of Nd3+:Y3Al5O12

In this paper there are briefly summarized the results of our experimental measurements of the fluorescence spectra, originating in levels of the4F3/2 term and terminating on the first two terms of the4I multipet, and the results of the absorption spectra at room temperature (RT) and at liquid-nitrogen temperature (NT) from which Nd3+: Y3Al5O12 energy-level diagram was determined. Further, using the splitting of the4F3/2,4F5/2 and4F7/2 terms the crystal-field parameters were calculated.

Excitation spectra for 1.06 μ luminescence in Nd3+-doped LaF3

The 4°K excitation spectrum of the 4F3/2-4I11/2 luminescence of Nd3+ in LaF3 was measured in the region of the six A absorption lines.

Liquid lasers—Design of neodymium-based inorganic ionic systems

The quantum yield of luminescence of Nd 3+ in liquids can be raised to levels similar to those obtained in single crystals and exceeding those of glasses by the removal of bonds with high vibrational energies from the environment of the ion. Reduction of the vibrational energies can be partially accomplished by deuteration of complexing with proper ligands, but is best achieved by the use of aprotic solvent systems. Selenium oxychloride meets the solvent requirements. Acidifying the solvent with an aprotic acid like tin tetrachloride or antimony pentachloride increases the solubility of Nd 3+ compounds. Low threshold laser action (2 J) is obtained in acid as well as in neutral solutions. The fully solvated Nd 3+ ion is suggested as the luminescent laser active species in the acid solution. In the basic solution the species is different and probably contains a Cl − ion in the solvation shell. Because of their high vibrational energies, quenching by hydrogen-containing compounds is effective. Self and ionic impurity quenching are less important because the fully solvated ions cannot approach each other sufficiently to make the diffusion assisted process effective.