The elemental composition from EDS measurements of the Zn(Tb)S and the Zn(Tb)S NPs that are post-synthetically treated with Pb²⁺ with varying concentrations are shown in panel (a). Panel (b) shows the XRD profiles of the Zn(Tb)S and the NPs with [Zn(Tb)S]:[Pb²⁺] = 1:1. Panels (c)–(e) show the luminescence excitation and emission spectra of the NPs investigated. The trends in quantum yields of ZnS and Tb³⁺ emissions in the NPs studied are shown in panels (f) and (g), respectively. The luminescence spectra from the experiments when the NPs with [Zn(Tb)S]:[Pb²⁺] = 1:1 is treated with an excess of Zn²⁺ and Tb³⁺ are shown in panel (h). The relative energy level schematic of Tb³⁺ with respect to the valence and conduction bands of the host ZnS and PbS are shown in panel (i). Panel (j) summarizes the Tb³⁺ emission quantum yields in different Zn(Tb)S/M [M = Pb, Hg, Cd, Ca, Mg, Na, K] NPs, with [Zn(Tb)S]:[Mⁿ⁺] = 1:10⁻². (Adapted with permission from Reference 102, Copyright 2018 Royal Society of Chemistry).