Host sensitized lanthanide photoluminescence from post-synthetically modified semiconductor nanoparticles depends on reactant identity

Optimizing the Key Variables to Generate Host Sensitized Lanthanide Doped Semiconductor Nanoparticle Luminophores

“…For postsynthetically modified II–VI NPs energy dispersive X-ray spectroscopy (EDS) showed (a) incorporation of Ln in the NPs, (b) significant changes in anion content of the NPs, and (c) an absence of complete cation exchange which is consistent with thermodynamic expectations . While Ln 3+ emission is appreciable in semiconductor NPs with a concentration in the range of tens of micromolar, the same can only be realized with a millimolar concentration for their free salts. ,, Dramatically altered excitation profiles upon monitoring Ln 3+ emissions in NPs, which overlap with NPs electronic absorption spectra, ,,− ,,− demonstrate the sensitization of the Ln 3+ emission by the NP. The significant lengthening of Ln 3+ emission lifetime in the NPs, as opposed to their corresponding free Ln 3+ salts in bulk solvent, , and the spectral changes of the NP capping ligand’s IR absorption spectrum by Ln 3+ ,, further substantiate the incorporation of the Ln 3+ in the NP lattice.…”

“…Left panel (top and bottom) shows normalized time-gated excitation [Tb (λ em = 545/490 nm, blue/red) and Eu (λ em = 696/616 nm (blue/red)] and emission spectra (λ ex = 300 nm, black) of the Zn­(Ln)S (Ln = Eu, Tb) NPs (adapted with permission from ref , Copyright 2011 American Chemical Society). (Middle) Normalized steady-state emission spectra of ZnS and Zn­(Ln)S (Ln = Eu, Tb) NPs are shown at the top (adapted with permission from ref , Copyright 2016 Royal Society of Chemistry and ref , Copyright 2019 Elsevier) and normalized steady-state emission spectra depicting the difference in Tb 3+ sensitization efficiency with different host semiconductor NPs is shown at the bottom. (Adapted with permission from ref , Copyright 2011 American Chemical Society).…”

“…(Adapted with permission from ref , Copyright 2011 American Chemical Society). (Right) Normalized steady-state excitation spectra of ZnS and Zn­(Ln)­S (Ln = Eu, Tb) NPs are shown at the top (adapted with permission from ref , Copyright 2016 Royal Society of Chemistry and ref , Copyright 2019 Elsevier), and normalized steady-state excitation spectra of free Ln 3+ in water are shown at the bottom (adapted with permission from ref , Copyright 2013 American Chemical Society).…”

“…Postsynthetic modification of undoped CA NPs by Ln 3+ cation exchange to create CA/Ln NPs enables a new sensing modality using cation exchange reactions. In 2013, we showed how to sensitize Eu 3+ and Tb 3+ emission by exposure of their solutions to undoped ZnS and CdS NPs at room temperature, and this was followed later by a comprehensive study of CdSe and ZnS NPs that were postsynthetically doped by Ln 3+ (Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb) . The remarkable observation of host sensitized Ln 3+ emission by semiconductor NPs at room temperature provides a unique avenue to develop luminophores in a less synthetically demanding fashion.…”

“…The Ln 3+ incorporation (in both synthetic and postsynthetic cases) has been demonstrated through observation of energy dispersive X-ray spectroscopic signatures for Ln 3+ in purified NPs, − and the increase in Ln 3+ photoluminescence in the NPs as compared to that found for free salts in bulk solvent. For postsynthetically modified II–VI NPs energy dispersive X-ray spectroscopy (EDS) showed (a) incorporation of Ln in the NPs, (b) significant changes in anion content of the NPs, and (c) an absence of complete cation exchange which is consistent with thermodynamic expectations .…”