Novel Red-Emitting Ba₂Tb(BO₃)₂Cl:Eu Phosphor with Efficient Energy Transfer for Potential Application in White Light-Emitting Diodes

A novel red-emitting Ba₂Tb­(BO₃)₂Cl:Eu phosphor possessing a broad excitation band in the near-ultraviolet (<i>n</i>-UV) region was synthesized by the solid-state reaction. Versatile Ba₂Tb­(BO₃)₂Cl compound has a rigid open framework, which can offer two types of sites for various valence’s cations to occupy, and the coexistence of Eu²⁺/Eu³⁺ and the red-emitting luminescence from Eu³⁺ with the aid of efficient energy transfer of Eu²⁺–Eu³⁺(Tb³⁺) and Tb³⁺–Eu³⁺ have been investigated. Ba₂Tb­(BO₃)₂Cl emits green emission with the main peak around 543 nm, which originates from ⁵D₄<i> → </i>⁷F₅ transition of Tb³⁺. Ba₂Tb­(BO₃)₂Cl:Eu shows bright red emission from Eu³⁺ with peaks around 594, 612, and 624 nm under <i>n</i>-UV excitation (350–420 nm). The existence of Eu²⁺ can be testified by the broad-band excitation spectrum, UV–vis reflectance spectrum, X-ray photoelectron spectrum, and Eu L₃-edge X-ray absorption spectrum. Decay time and time-resolved luminescence measurements indicated that the interesting luminescence behavior should be ascribed to efficient energy transfer of Eu²⁺–Eu³⁺(Tb³⁺) and Tb³⁺–Eu³⁺ in Ba₂Tb­(BO₃)₂Cl:Eu phosphors

Presentation1.pdf

<p>With a layered structure, layered double hydroxide (LDH) has potential applications in remediation of anionic contaminants, which has been a hot topic for recent years. In this study, a Cl type Mg-Al hydrotalcite (Cl-LDH) was prepared by a co-precipitation method. The adsorption process of three pharmaceuticals and personal care products (PPCPs) [tetracycline (TC), diclofenac sodium (DF), chloramphenicol (CAP)] by Cl-LDH was investigated by X-ray diffraction (XRD), Zeta potential, dynamic light scattering (DLS), BET, Fourier transform infrared (FTIR) spectroscopy, and molecular dynamics simulation. The results showed that the adsorption equilibrium of TC and DF could be reached in 120 min, and the maximum adsorption capacity of the TC and DF were 1.85 and 0.95 mmol/g, respectively. The isothermal adsorption model of TC was fitted with the Freundlich adsorption model, and the isothermal adsorption model of DF was fitted with the Langmuir adsorption model. The adsorption dynamics of TC and DF followed the pseudo-second-order model. The adsorption mechanisms of the three PPCPs into Cl-LDH were different based on the experimental results and molecular dynamics simulation. The TC adsorption on Cl-LDH was accompanied by the electrostatic interactions between the negative charge of TC and the positive charge of Cl-LDH. The uptake of DF was attributed to anion exchange and electrostatic interaction. Cl-LDH does not adsorb CAP due to no electrostatic interaction. The molecular dynamic simulation further confirmed different configurations of three selected PPCPs, which were ultimately responsible for the uptake of PPCPs on Cl-LDH.</p