Carbon quantum dot-sensitized and tunable luminescence of Ca19Mg2(PO4)14:Ln3+ (Ln3+ = Eu3+ and/or Tb3+) nanocrystalline phosphors with abundant colors via a sol-gel process

Herein, we demonstrate the characteristic blue luminescence of carbon quantum dots embedded in the Ca19Mg2(PO4)(14) nanocrystalline phosphor and carbon quantum dot-sensitized luminescence of Ca19Mg2(PO4)(14):Ln(3+) (Ln(3+) = Eu3+ and/or Tb3+) nanocrystalline phosphors with abundant colors. A series of Ca19Mg2(PO4)(14) and Ca19Mg2(PO4)(14):Ln(3+) (Ln(3+) = Eu3+ and/or Tb3+) nanocrystalline phosphors was prepared via a Pechini-type sol-gel process. With UV light excitation, the prepared Ca19Mg2(PO4)(14) nanocrystalline phosphors exhibited novel blue luminescence with a broad band from 374 to 600 nm peaking at 439 nm, which is ascribed to the embedded carbon quantum dots. Also, the obtained Ca19Mg2(PO4)(14):Ln(3+) (Ln(3+) = Eu3+ and/or Tb3+) nanocrystalline phosphors not only exhibited the characteristic broad band emission of the carbon quantum dots, but also the characteristic narrow line emission of the doped rare earth ions, i.e., the characteristic red emission of Eu3+ (D-5(J) F-7(J) transitions, J, J = 0, 1, 2, 3) and the characteristic green emission of Tb3+ (D-5(4) F-7(J) transitions, J = 3, 4, 5, 6). Thus, energy transfer occurred from the carbon quantum dots to the doped Eu3+ and/or Tb3+ ions in the Ca19Mg2(PO4)(14):Ln(3+) (Ln(3+) = Eu3+ and/or Tb3+) nanocrystalline phosphors. The luminescence color of the Ca19Mg2(PO4)(14):Ln(3+) (Ln(3+) = Eu3+ and/or Tb3+) nanocrystalline phosphors could be tuned from blue to blue-green, green, white, pink, orange, red, etc. by changing the doping rare-earth ion concentration, species, and relative ratio of Eu3+ to Tb3+ ions. Furthermore, single-phase white-light luminescence was demonstrated in the Eu3+/Tb3+ codoped Ca19Mg2(PO4)(14):Ln(3+) nanocrystalline phosphors. Finally, the luminescence properties and mechanisms of the Ca19Mg2(PO4)(14) and Ca19Mg2(PO4)(14):Ln(3+) (Ln(3+) = Eu3+ and/or Tb3+) nanocrystalline phosphors were discussed.