Green synthesis, structure feature and energy transfer of yellow-emitting (Y,Gd)2 O2 SO4 :Dy phosphors

A green chemical precipitation route was used to yield a hydrated basic sulfate precursor upon calcination at 1000°C into a series of (Y,Gd)₂ O₂ SO₄ :Dy particles. The phosphors exhibited characteristic Dy³⁺ emissions from ⁴ F_9/2 →⁶ H_J (J = 15/2, 13/2, 11/2) transitions under ultraviolet light excitation; the quenching concentration of Dy³⁺ was determined to be 2.5 at.%. Substitution of Gd³⁺ for Y³⁺ led to an additional strong sharp band at ~277 nm (⁸ S_7/2 →⁶ I_J transition of Gd³⁺ ) in the photoluminescence excitation spectra, upon which the (Gd_0.975 Dy_0.025 )₂ O₂ SO₄ phosphor achieved a ~2.8-fold higher photoluminescence intensity via an effective energy transfer from Gd³⁺ to Dy³⁺ compared with the 354 nm excitation of Dy³⁺ . Both the photoluminescence and photoluminescence excitation intensities of (Y,Gd)₂ O₂ SO₄ :Dy phosphors increased with rising Gd³⁺ concentration and calcination temperature in the range 750-1000°C. A higher Gd³⁺ concentration slightly prolonged the effective fluorescence lifetime.

Electrochemical Ce(III)/Ce(IV) Redox Behavior and Ce Oxide Nanostructure Recovery over Thio-Terpyridine-Functionalized Au/Carbon Paper Electrodes

Understanding the electrochemical behaviors of Ce(III)/Ce(IV) ions is essential for better treatment, separation, and recycling of lanthanide (Ln) and actinide (An) elements. Herein, electrochemical redox behavior and interconversion of Ce(III)/Ce(IV) ions and their recoveries were demonstrated over newly developed thio-terpyridine-functionalized Au-modified carbon paper electrodes in acidic and neutral electrolytes. Cyclic voltammetry and amperometry were performed for the electrodes with and without thio-terpyridine functionalization. Ce oxide nanostructure recovery was successfully conducted by amperometry, and the electrodeposited nanostructured Ce materials were fully characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction crystallography, and X-ray photoelectron spectroscopy. Geometry optimization and the electronic energy state calculations were conducted by density functional theory at the B3LYP/GENECP level for the complexes of Ce(III) and Ce(IV) ions with the thio-terpyridine in an aqueous state. The present unique results provide valuable information on understanding redox behaviors of Ln and An ions for their recycling and treatment processes.