Comparative analysis of Nd3+(4f3) energy levels in four garnet hosts

Covalency versus magnetic axiality in Nd molecular magnets: Nd-photoluminescence, strong ligand-field, and unprecedented nephelauxetic effect in fullerenes NdM2N@C80 (M = Sc, Lu, Y)

Nd-based nitride clusterfullerenes NdM2N@C80 with rare-earth metals of different sizes (M = Sc, Y, Lu) were synthesized to elucidate the influence of the cluster composition, shape and internal strain on the structural and magnetic properties. Single crystal X-ray diffraction revealed a very short Nd-N bond length in NdSc2N@C80. For Lu and Y analogs, the further shortening of the Nd-N bond and pyramidalization of the NdM2N cluster are predicted by DFT calculations as a result of the increased cluster size and a strain caused by the limited size of the fullerene cage. The short distance between Nd and nitride ions leads to a very large ligand-field splitting of Nd3+ of 1100-1200 cm-1, while the variation of the NdM2N cluster composition and concomitant internal strain results in the noticeable modulation of the splitting, which could be directly assessed from the well-resolved fine structure in the Nd-based photoluminescence spectra of NdM2N@C80 clusterfullerenes. Photoluminescence measurements also revealed an unprecedentedly strong nephelauxetic effect, pointing to a high degree of covalency. The latter appears detrimental to the magnetic axiality despite the strong ligand field. As a result, the ground magnetic state has considerable transversal components of the pseudospin g-tensor, and the slow magnetic relaxation of NdSc2N@C80 could be observed by AC magnetometry only in the presence of a magnetic field. A combination of the well-resolved magneto-optical states and slow relaxation of magnetization suggests that Nd clusterfullerenes can be useful building blocks for magneto-photonic quantum technologies.

Unraveling the local structure and luminescence evolution in Nd3+-doped LiYF4: a new theoretical approach

Neodymium ion (Nd3+)-doped yttrium lithium fluoride (LiYF4, YLF) laser crystals have shown significant prospects as excellent laser materials in many kinds of solid-state laser systems. However, the origins of the detailed information of their local structure and luminescence evolution are still poorly understood. Herein, we use an unbiased CALYPSO structure searching technique and density functional theory to study the local structure of Nd3+-doped YLF. Our results reveal a new stable phase with the P4[combining macron] (No. 81) space group for Nd3+-doped YLF, indicating that the host Y3+ ion site was naturally occupied by the Nd3+ ion impurity. On the basis of our newly developed WEPMD method, we adopt a specific type of orthogonal correlation crystal field to obtain a new set of crystal-field parameters as well as 182 complete Stark energy levels. Many absorption and emission lines for Nd3+-doped YLF are calculated and discussed based on Judd-Ofelt theory, and our results indicate that some of the observed absorption and emission lines are perfectly reproduced by our theoretical calculations. Additionally, we predict several promising transition lines in the visible and near-infrared spectral regions, including the electronic dipole emission lines 4F5/2 → 4I9/2 at 808 nm and 2H9/2 → 4I9/2 at 799 nm, as well as the magnetic dipole emission lines 4F3/2(27) → 4I11/2(6) at 1047 nm and 4F3/2(27) → 4I11/2(8) at 1052 nm. These transition channels indicate that Nd3+-doped YLF laser crystals have greatly promising laser actions for serving as a solid-state laser material.

Simultaneous Enhancement of Near-Infrared Emission and Dye Photodegradation in a Racemic Aspartic Acid Compound via Metal-Ion Modification

Changing functionalities of materials using simple methods is an active area of research, as it is "green" and lowers the developing cost of new products for the enterprises. A new small molecule racemic N,N-dimethyl aspartic acid has been prepared. Its structure is determined by single-crystal X-ray diffraction. It is characterized by FTIR, XPS, ¹H NMR, and mass spectroscopy. Its near-infrared luminescence can be enhanced by the combination of metal ions, including Dy³⁺, Gd³⁺, Nd³⁺, Er³⁺, Sr³⁺, Y³⁺, Zn²⁺, Zr⁴⁺, Ho³⁺, Yb³⁺, La³⁺, Pr⁶⁺/Pr³⁺, and Sm³⁺ ions. An optical chemistry mechanism upon interaction between the sensitizer and activator is proposed. Furthermore, the association of Ca²⁺, Sr²⁺, or Zr⁴⁺ ions to the molecule enhanced its photodegradation for dyes under white-light irradiation. Specifically, rhodamine 6G can be degraded by the Ca²⁺-modified molecule; rhodamine B, rhodamine 6G, and fluorescein sodium salt can be degraded by the Sr²⁺- or Zr⁴⁺-modified molecule. This surprising development opens a way in simultaneously increasing NIR luminescence and the ability of dye photodegradation for the investigated molecule.

New Theoretical Insights into the Crystal-Field Splitting and Transition Mechanism for Nd3+-Doped Y3Al5O12

There has been considerable research interest paid to rare-earth transition-metal-doped Y₃Al₅O₁₂, which has great potential for application as a laser crystal of new-type laser devices because of its unique optoelectronic and photophysical properties. Here, we present new research conducted on the structural evolution and crystal-field characteristics of a rare-earth Nd-doped Y₃Al₅O₁₂ laser crystal by using the CALYPSO structure search method and our newly developed WEPMD method. A novel cage-like structure with a Nd³⁺ concentration of 4.16% is uncovered, which belongs to the standardized C₂₂₂ space group. Our results indicate that the impurity Nd³⁺ ions are likely to substitute the Y³⁺ at the central site of the host Y₃Al₅O₁₂ crystal lattice. The laser emission ⁴F_3/2 → ⁴I_11/2 occurring at 1077 nm is in accord with that of the experimental data. By introducing the proper correlation crystal field, three transitions, ⁴G_5/2 → ⁴I_9/2, ⁴F_7/2 → ⁴I_9/2, and ⁴S_3/2 → ⁴I_9/2, are predicted to be good candidates for laser action. These findings can provide powerful guidelines for further experiments of rare-earth-metal-doped laser crystals.

Insights into the Microstructure and Transition Mechanism for Nd3+-Doped Bi4Si3O12: A Promising Near-Infrared Laser Material

Due to its unusual optical properties, neodymium ion (Nd³⁺)-doped bismuth silicate (Bi₄Si₃O₁₂, BSO) is widely used for its excellent medium laser amplification in physics, chemistry, biomedicine, and other research fields. Although the spectral transitions and luminescent mechanisms of Nd³⁺-doped BSO have been investigated experimentally, theoretical research is severely limited due to the lack of detailed information about the microstructure and the doping site of Nd³⁺-doped BSO, as well as the electric and magnetic dipole transition mechanisms. Herein, we systematically study the microstructure and doping site of Nd³⁺-doped BSO using an unbiased CALYPSO structure search method in conjunction with first-principles calculations. The result indicates that the Nd³⁺ ion impurity occupies the host Bi³⁺ ion site with trigonal symmetry, forming a unique semiconducting phase. Based on our newly developed WEPMD method, the electric dipole and magnetic dipole transition lines, including a large number of absorption and emission lines, in the region of visible and near-infrared spectra of Nd³⁺-doped BSO are calculated. It is found that the ⁴G_5/2 → ⁴I_9/2, ²H_9/2 → ⁴I_9/2, and ⁴F_3/2 → ⁴I_11/2 channels are promising laser actions of Nd³⁺-doped BSO. These findings indicate that Nd³⁺-doped BSO crystals can serve as a promising multifunctional material for optical laser devices.