Abstract
Developing an efficient approach to improve the luminescence of the phosphors without heating processing is a challenge, but attracts much attention. In the present paper, prismatic microcrystals of RE4O(OH)9NO3 (RE = Y, Eu) were synthesized by a hydrothermal reaction at 180 °C for 24 h. The reaction with VO3− did not change the crystal structure of the microcrystals and VO3− substituting for NO3− anions did not take place. However, it contributed to the formation of amorphous particles containing VO3− on the surface of a prism, which is similar to the surface corrosion of a metal, called “surface eroding”. Therefore, surface modification was successfully achieved by eroding the surface of the microcrystals through the reaction with vanadate ions. As a result of VO3−→Eu3+ energy transfer and the light-harvesting ability of VO3−, the red emission intensity at 617 nm of the modified microcrystals greatly increased. Eroding the surface of rare earth microcrystals recommends a new paradigm for luminescence improvement of rare earth compounds.
Highlights
Exciting RE3+ ions upon irradiation for luminescence is not an efficient method, because the f–f electronic transitions of the rare earth ions (RE3+) are usually forbidden by the spin selection rules [1]
RE2(OH)5NO3·nH2O layered rare earth hydroxide (LRH), RE4O(OH)9NO3 oxy-hydroxyl nitrate, RE(OH)2.94(NO3)0.06·nH2O hydroxyl nitrate, and RE(OH)3 hydroxide are the reported products synthesized from the hydrothermal reaction system [7,8,9,10], and their morphology and size could be regulated by varying the synthesis conditions, including the pH value, reaction temperature, and reaction time
The surface modification of the microcrystals was successfully achieved by eroding the surface of the microcrystals through vanadate ions
Summary
Exciting RE3+ ions upon irradiation for luminescence is not an efficient method, because the f–f electronic transitions of the rare earth ions (RE3+) are usually forbidden by the spin selection rules [1]. RE2(OH)5NO3·nH2O layered rare earth hydroxide (LRH), RE4O(OH)9NO3 oxy-hydroxyl nitrate, RE(OH)2.94(NO3)0.06·nH2O hydroxyl nitrate, and RE(OH) hydroxide are the reported products synthesized from the hydrothermal reaction system [7,8,9,10], and their morphology and size could be regulated by varying the synthesis conditions, including the pH value, reaction temperature, and reaction time. They are the desirable precursors for rare earth oxide phosphors. The oxy-hydroxyl nitrate microcrystals and the microcrystals eroded by VO3− are denoted as MC and MC-RV hereafter, with the R-fold VO3− in the reaction system
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