Evaluating Inter-Lanthanide Interactions in Co-Doped Zinc Sulfide Nanoparticles for Multiplex Assays

Abstract

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.

Maximizing Terbium–Europium Electronic Interaction: Insight from Variation of Excitation Energy

“…55 Recently, we reported a difference in energy transfer from Tb 3+ * → Eu 3+ in differently synthesized ZnS-based NPs and observed a synthetic condition-dependent interdopant photophysical interaction. 51 These measurements, along with control experiments with Tb−Sm-, Tb−Tm-, and Tb−Yb-co-doped NPs, establish the importance of charge trapping.…”

“…Recently, we discussed how at least an equal amount of Tb and Eu codopants is necessary to realize achievable Tb 3+ −Eu 3+ electronic interaction. 51 XRF. XRF is an alternate method for determining the elemental composition.…”

“…This argument is based on our experiments with Tb−Eu-, Tb−Yb-, Tb−Sm-, and Tb−Tm-co-doped ZnS NPs. 51 We observed interdopant electronic interactions being present in the Tb− Eu-and Tb−Yb-containing NPs and the same being absent in the Tb−Sm-and Tb−Tm-containing NPs. While the experimental observations from the Tb−Eu-co-doped ZnS NPs can be well visualized within either a charge trappingmediated or spectral overlap-mediated process, the observations from the Tb−Yb-, Tb−Sm-, and Tb−Tm-co-doped NPs clearly identify the importance of a charge trapping-mediated process.…”

“…Another fascinating avenue is to dope multiple and distinct Ln 3+ in an NP to generate co-doped NPs. − These assemblies are particularly attractive to access luminophores for multiplex assays, which is to generate multiple non-overlapping emission bands at various wavelengths using a single excitation source. Such a scenario can be visualized in a Tb 3+ –Eu 3+ -co-doped ZnS NP.…”

“…Few articles reviewed and discussed different cases with Tb–Eu electronic interactions both from experimental and theoretical perspectives. − General considerations on the energy transfer between unlike Ln 3+ are also discussed . Recently, we reported a difference in energy transfer from Tb 3+* → Eu 3+ in differently synthesized ZnS-based NPs and observed a synthetic condition-dependent interdopant photophysical interaction . These measurements, along with control experiments with Tb–Sm-, Tb–Tm-, and Tb–Yb-co-doped NPs, establish the importance of charge trapping.…”