This work discusses the photoluminescence properties of doped semiconductor nanoparticles by adding cadmium(II) nitrates post-synthetically to the terbium cation incorporated zinc sulfide [Zn(Tb)S] nanoparticles at room temperature to generate the Zn(Tb)S/Cd nanoparticles. The evolution of nanoparticle's emission is monitored as a function of amount of Cd 2+ , with [Zn(Tb)S]/[Cd 2+ ] = 1:10 −4 to 1:10, providing an opportunity to access materials of different chemical compositions. Structural features, as evaluated by X-ray diffraction and energy-dispersive X-ray spectroscopy, indicate a partial cation exchange of zinc by cadmium. No apparent replacement of terbium is noticed throughout the post-synthetic modification of the Zn(Tb)S nanoparticles until the relative reactant ratio reaches 1:10, and this only becomes noticeable with [Zn(Tb)S]/[Cd 2+ ] = 1:50. Remarkable differences in both broad and sharp emissions of nanoparticles and Tb 3+ , respectively, have been observed in the post-synthetic modification. The reaction initiates with a blue shift of nanoparticle's broad emission, and a further increase in Cd 2+ content results in a red shift. Tb 3+ emission, despite its insensitivity in the spectral band position due to the intra-configurational 4f transitions, shows a decrease in emission efficiency following post-synthetic modification. Formation of alloyed particles, however, significantly improved excitation contribution approaching the visible spectral region. Lifetime measurements of nanoparticles and Tb 3+ emission support the exchange of cations and the role of competitive nonradiative deactivation pathways, respectively. Collectively, nanoparticles with [Zn(Tb)S]/[Cd 2+ ] = 1:10 −4 to 1:10 −3 , 1:10 −2 , 1:10 −2 to 1:10, and 1:50 are argued to form Cd 2+ -induced surface trap-passivated Zn(Cd)(Tb)S, onset of Zn 1−x Cd x (Tb)S alloy formation, Zn 1−x Cd x (Tb)S alloys of varying compositions, and Zn 1−x Cd x S nanoparticles, respectively. Finally, this work provides a foundation to tune the properties of any emissive doped semiconductor nanoparticles in a lesser synthetically demanding fashion and has important implications in developing such materials.

This work reports the photophysical properties of 1-thioglycerol capped hydrophilic terbium cation incorporated (doped) regime compared to in bulk environments. The results presented provide an avenue for the detection of heavy metal ions in general and Pb 2+ in particular, with a limit of detection that is at least in the range of sub-ppm, using either the broad ZnS or sharp Tb 3+ emission, respectively. This strategy provides an avenue to combine (i) the extremely sensitive and easily accessible analytical technique of photoluminescence spectroscopy, (ii) post-synthetic modification reactions in semiconductor nanoparticles that can be performed with less experimental demand, (iii) time-gated measurement related to the longer luminescence lifetime of terbium cations and (iv) the simultaneous use of broad ZnS nanoparticle and sharp Tb 3+ emission from the same assembly, helping eliminate false positive results.

Multiple and distinct lanthanide (Ln)-doped nanoparticles (NPs) can benefit in accessing multiplex assays for photoluminescence-based applications. This study develops Tb− Eu co-doped ZnS nanoparticles (NPs) using different synthetic pathways. These include Zn(Tb)S/Eu, Zn(Eu)S/Tb, Zn(TbEu)S, and ZnS/TbEu NPs, where the lanthanides within parenthesis and after a slash indicate their addition synthetically and postsynthetically, respectively. The differing synthetic protocols affect the dopant concentrations and spatial location in the NPs, which give rise to remarkable differences in interdopant electronic interactions. Both charge trapping-and spectral overlap-mediated interdopant electronic interactions can explain energy transfer from Tb 3+ to Eu 3+ . Control experiments with Tb−Yb, Tb−Sm, and Tb−Tm containing NPs identify the importance of the relative energetics of the Ln 2+ ground energy level with respect to the Tb 3+ luminescent energy level in controlling the Tb 3+ −Ln 3+ interaction, thus implicating the importance of charge trapping-mediated interdopant electronic interactions. The results discussed provide a solid foundation to identify suitable codoped NP luminophores.

The role of surface capping ligands in controlling dopant photoluminescence in semiconductor nanoparticles is examined by monitoring emission in terbium cation incorporated zinc sulfide [Zn­(Tb)­S] nanoparticles, as a function of [H+] that is varied postsynthetically. Increases in Tb3+ emission of ∼6 and ∼1.3 times are observed on changing the pH from 4 to 7 and from 7 to 11, respectively. An increased contribution of host sensitization over direct excitation is observed under basic conditions. Subtle structural modification of the capping ligand is argued to be solely responsible for the dopant emission in the acidic–neutral range. The neutral–basic range in addition to this effect has a minor contribution from alteration in band alignment as well. A major outcome from this work relates to identifying the role of the terminally placed functional group in the capping ligand to control emissions from both the host (zinc sulfide nanoparticles) and guest (Tb3+), with a pronounced effect on dopant Tb3+ emission in the 1-thioglycerol capped Zn­(Tb)S nanoparticles. These results identify surface engineering as an important modulator, in addition to the primary criteria of (a) band gap engineering and (b) breaking (or optimizing) dopant local site symmetry in maximizing (or guiding) dopant emission in doped semiconductor nanoparticles.

Postsynthetic modification of inorganic nanoparticles (NPs) involving appropriate cation pairs at or near ambient conditions can exchange their spatial positions. The characterization of final products from these reactions although attracted...