Eu(III) and Tb(III) Complexes with the Nonsteroidal Anti-Inflammatory Drug Carprofen: Synthesis, Crystal Structure, and Photophysical Properties

Two new lanthanide complexes with general formula [Ln₂(carprofen)₆­(DMF)₂] (Ln = Eu (<b>1</b>), Tb (<b>2</b>), DMF = <i>N</i>,<i>N</i>-dimethylformamide, carprofen = 6-chloro-α-methylcarbazole-2-acetic acid) have been synthesized by a hydrothermal method. Complex <b>1</b> was characterized by single-crystal X-ray diffraction (XRD), and it was found to crystallize in the monoclinic space group <i>C</i>2<i>/c</i>. The coordination of the ligand to the lanthanide ion has been investigated by Fourier-transform infrared (FTIR) spectra and ultraviolet–visible (UV–vis) absorption spectra. Complex <b>1</b> emits red light, but the antenna effect of the ligand is not effective, whereas complex <b>2</b> presents intense green emission with effective energy transfer from the ligand. The different performance of the two complexes is related to the energy matching between the excited states of the lanthanide ion and the triplet state of the ligand. The intramolecular energy transfer mechanisms are also discussed

Eu(III) and Tb(III) Complexes with the Nonsteroidal Anti-Inflammatory Drug Carprofen: Synthesis, Crystal Structure, and Photophysical Properties

Two new lanthanide complexes with general formula [Ln₂(carprofen)₆­(DMF)₂] (Ln = Eu (<b>1</b>), Tb (<b>2</b>), DMF = <i>N</i>,<i>N</i>-dimethylformamide, carprofen = 6-chloro-α-methylcarbazole-2-acetic acid) have been synthesized by a hydrothermal method. Complex <b>1</b> was characterized by single-crystal X-ray diffraction (XRD), and it was found to crystallize in the monoclinic space group <i>C</i>2<i>/c</i>. The coordination of the ligand to the lanthanide ion has been investigated by Fourier-transform infrared (FTIR) spectra and ultraviolet–visible (UV–vis) absorption spectra. Complex <b>1</b> emits red light, but the antenna effect of the ligand is not effective, whereas complex <b>2</b> presents intense green emission with effective energy transfer from the ligand. The different performance of the two complexes is related to the energy matching between the excited states of the lanthanide ion and the triplet state of the ligand. The intramolecular energy transfer mechanisms are also discussed

Site-Dependent Luminescence and Thermal Stability of Eu²⁺ Doped Fluorophosphate toward White LEDs for Plant Growth

Eu²⁺ activated fluorophosphate Ba₃GdNa­(PO₄)₃F (BGNPF) with blue and red double-color emitting samples were prepared via a solid-state method in a reductive atmosphere. Their crystal structure and cationic sites were identified in light of X-ray diffraction pattern Rietveld refinement. Three different Ba²⁺ sites, coordinated by six O atoms referred to as Ba1, two F and five O atoms as Ba2, and two F and six O atoms as Ba3, were partially substituted by Eu²⁺. Photoluminescence emission (PL) and excitation (PLE) spectra of phosphor BGNPF:Eu²⁺ along with the lifetimes were characterized at the liquid helium temperature (LHT), which further confirm the existence of three Eu²⁺ emitting centers resulting in 436, 480, and 640 nm emission from the 5d → 4f transitions of Eu²⁺ in three different Ba²⁺ crystallographic sites. These emissions overlap with the absorption spectra of carotenoids and chlorophylls from plants, which could directly promote the photosynthesis. Temperature-dependent PL spectra were used to investigate the thermal stability of phosphor, which indicates that the PL intensity of BGNPF:0.9% Eu²⁺ with optimal composition at 150 °C still keeps 60% of its PL intensity at room temperature, in which blue emission has higher thermal-stability than the red emission. Furthermore, the approaching white LED devices have also been manufactured with a 365 nm n-UV LED chip and present phosphor, which make operators more comfortable than that of the plant growth purple emitting LEDs system composed of blue and red light. Results indicate that this phosphor is an attractive dual-responsive candidate phosphor in the application n-UV light-excited white LEDs for plant growth

Improvement of Green Upconversion Monochromaticity by Doping Eu³⁺ in Lu₂O₃:Yb³⁺/Ho³⁺ Powders with Detailed Investigation of the Energy Transfer Mechanism

The monochromaticity improvement of green upconversion (UC) in Lu₂O₃:Yb³⁺/Ho³⁺ powders has been successfully realized by tridoping Eu³⁺. The integral area ratio of green emission to red emission of Ho³⁺ increases 4.3 times with increasing Eu³⁺ doping concentration from 0 to 20 mol %. The energy transfer (ET) mechanism in the Yb³⁺/Ho³⁺/Eu³⁺ tridoping system has been investigated carefully by visible and near-infrared (NIR) emission spectra along with the decay curves, revealing the existence of ET from the Ho³⁺ ⁵F₄/⁵S₂ level tothe Eu³⁺ ⁵D₀ level and ET from the Ho³⁺ ⁵I₆ level to the Eu³⁺ ⁷F₆ level. In addition, the population routes of the red-emitting Ho³⁺ ⁵F₅ level in the Yb³⁺/Ho³⁺ codoped system under 980 nm wavelength excitation have also been explored. The ET process from the Yb³⁺ ²F_5/2 level to the Ho³⁺ ⁵I₇ level and the cross-relaxation process between two nearby Ho³⁺ ions in the ⁵F₄/⁵S₂ level and ⁵I₇ level, respectively, have been demonstrated to be the dominant approaches for populating the Ho³⁺ ⁵F₅ level. The multiphonon relaxation process originating from the Ho³⁺ ⁵F₄/⁵S₂ level is useless to populate the Ho³⁺ ⁵F₅ level. As the energy level gap between the Ho³⁺ ⁵I₇ level and Ho³⁺ ⁵I₈ level matches well with that between Eu³⁺ ⁷F₆ level and Eu³⁺ ⁷F₀ level, the energy of the Ho³⁺ ⁵I₇ level can be easily transferred to the Eu³⁺ ⁷F₆ level by an approximate resonant ET process, resulting in a serious decrease in the red UC emission intensity. Since this ET process is more efficient than the ET from the Ho³⁺ ⁵F₄/⁵S₂ level to the Eu³⁺ ⁵D₀ level as well as the ET from the Ho³⁺ ⁵I₆ level to the Eu³⁺ ⁷F₆ level, the integral area ratio of green emission to red emission of Ho³⁺ has been improved significantly

Enhancement of Eu³⁺ Red Upconversion in Lu₂O₃: Yb³⁺/Eu³⁺ Powders under the Assistance of Bridging Function Originated from Ho³⁺ Tridoping

The red upconversion (UC) emission of Eu³⁺ ions in Lu₂O₃: Yb³⁺/Eu³⁺ powders was successfully enhanced by tridoping Ho³⁺ ions in the matrix, which is due to the bridging function of Ho³⁺ ions. The experiment data manifest that, in Yb³⁺/Eu³⁺/Ho³⁺ tridoped system, the Ho³⁺ ions are first populated to the green emitting level ⁵F₄/⁵S₂ through the energy transfer (ET) processes from the excited Yb³⁺ ions. Subsequently, the Ho³⁺ ions at ⁵F₄/⁵S₂ level can transfer their energy to the Eu³⁺ ions at the ground state, resulting in the population of Eu³⁺ ⁵D₀ level. With the assistance of the bridging function of Ho³⁺ ion, this ET process is more efficient than the cooperative sensitization process between Yb³⁺ ion and Eu³⁺ ion. Compared with Lu₂O₃: 5 mol % Yb³⁺/1 mol % Eu³⁺, the UC intensity of Eu³⁺ ⁵D₀→⁷F₂ transition in Lu₂O₃: 5 mol % Yb³⁺/1 mol % Eu³⁺/0.5 mol % Ho³⁺ is increased by a factor of 8