Spectroscopic investigation on tunable luminescence by energy transfer in Tb2−xSmx(MoO4)3 nanophosphors

Abstract

New Sm3+ activated Tb2−xSmx(MoO4)3 nanophosphors were synthesized through sol–gel method. The structural and luminescence properties have been studied by XRD, TEM and photoluminescence measurements. The XRD pattern confirms that the Tb2−xSmx(MoO4)3 crystallizes in the same orthorhombic structure of Tb2(MoO4)3. The spectroscopic and laser parameters of Sm3+ ion in Tb2−x(MoO4)3 matrix were evaluated for the first time using Judd–Ofelt theoretical analysis. The higher value of stimulated emission cross-section of 4G5/2→6H7/2 transition of Sm3+ is favorable for low threshold and high gain to obtain continuous wave laser action. The photoluminescence excitation spectra suggest that this novel phosphor can be excited over a broad range from nUV to blue light (300–490nm). Under the excitation of UV, Tb2−xSmx(MoO4)3 nanophosphor exhibits the characteristic emissions of Tb3+ and Sm3+. By varying the doping concentration of Sm3+, the emission color of the phosphors can be tuned and white emission in a single composition can be obtained under host excitation, in which an energy transfer from MoO42−→Sm3+/ Tb3+ and Tb3+→Sm3+ was observed. The investigation of the luminescence decay curves and lifetime values implies the energy transfer between Tb3+→Sm3+ and confirms the absence of Sm3+→Tb3+ energy transfer. These phosphors might be a promising material for use in nUV LEDs and can exhibit tricolor luminescence under single excitation wavelength.