Synthesis and luminescent properties of Eu(III)/Tb(III) rare earth complex-coated the core-shell structured silica microspheres: Unleashing the potential for white light emission

A rare earth organic complex, SiO2@ATPA-Si-RE (RE = Eu, Tb), exhibiting a core-shell structure, was synthesized using the ligand (HOOC)2C6H3NHCONH(CH2)3Si(OCH2CH3)3(ATPA-Si) to connect the silica microspheres core and coordinate with rare earth ions. The pH value of the reaction was adjusted to produce organic complex shells with thicknesses of 2.0 nm and 5.0 nm, while the SiO2 core measured a diameter of 125 nm. Luminescence spectra indicated that the emission intensity of the SiO2@ATPA-Si-RE (RE = Eu, Tb) core-shell structure was stronger than that of the ATPA-Si-RE organic complex due to a perfect match between the triplet energy level of SiO2@ATPA-Si and the excited energy level of rare earth ions (Eu3+, Tb3+). Remarkably, the core-shell structure with a 2.0 nm shell thickness possessed a greater emission intensity compared to the 5.0 nm shell thickness. Moreover, these findings unveiled the tunability of luminescence color, ranging from green or red to white, by adjusting the doping ratio of Eu3+ and Tb3+ ions and the coating thickness of complexes. Particularly, a warm white light emission, characterized by CIE coordinates (0.389, 0.347), a color rendering index value of 86.7, and a low correlated color temperature value of 3550 K, was achieved using the organic complex with a 2.0 nm thickness coated on SiO2 microspheres with a doping ratio of Eu3+ at 0.7 mmol and Tb3+ at 0.3 mmol. Conversely, the complexes with a 5.0 nm coating thickness and Tb3+ doping ratio of 0.3 mmol yielded a cold white light emission. These findings demonstrate the potential applications in next-generation lighting industry and display systems.