Ln^III-centered emission sensitized through fluorescent carbon dots

We synthesized CDs that were crystalline and monodisperse with average diameters in the range 4–5 nm. The CDs had a fluorescence quantum yield of 0.20%, with emission lifetimes of 3.1 and 6.5 ns attributed to surface and core emissions, respectively. ¹³C NMR spectroscopy indicated the presence of C–C, C⁼C and C⁼O groups on the surface of the CDs. Powder XRD and TEM indicate the CDs are graphitic. The CDs were decorated with Ln^III ions through coordination to the surface carbonyl and carboxylato groups. When excited, the CDs transferred energy to the emissive states of the Ln^III ions, which led to observation of the characteristic emission spectra of Eu^III and Tb^III with emission lifetimes of 1.00 and 0.63 ms, respectively and with emission quantum yields of 0.17% and 1.43%, respectively.