Design of core–shell phosphors with tunable luminescence and improved thermal stability by coating with g-C3N4

The exploration of new strategies to fabricate phosphors with tunable luminescence and enhanced thermal stability has been pursued since a long time. In this study, we propose and demonstrate a novel methodology of coating g-C3N4 on phosphors by a vapor deposition method to synthesize core–shell phosphors with tunable luminescence and improved thermal stability. By this method, flaky g-C3N4 can be evenly coated on the surface of the precursors Y2O3:Eu3+,Tb3+ and Y2O3:Eu3+,Tb3+@SiO2 with a thickness of 8 nm. Under the excitation at 368 nm, the CIE coordinates can be adjusted from blue region (0.1713, 0.1887) to white (0.3074, 0.3232) and yellow (0.4565, 0.4703) regions by controlling the amount of g-C3N4. Moreover, the thermal stability of phosphors can be improved by the g-C3N4 coating shell at elevated temperatures due to the isolation of luminescence centers, modification of surface defects, and efficient energy transfer from g-C3N4; the emission intensity of Eu3+ at 398 K improved by 13% after coating with g-C3N4. The above-mentioned effects of g-C3N4 were also proved to work well on the Ca9.5Na2(PO4)7:Eu2+ yellow-green emitting phosphor, indicating that this methodology has general applicability for improving luminescent properties of phosphors.