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

Abstract

Trivalent lanthanide (Ln3+) doped semiconductor nanoparticles (NPs) provide an avenue for developing unique luminophores, which combine the properties of Ln3+ and NPs. Realizing their promise requires a thorough understanding of their underlying photophysical processes. This article summarizes experimental findings and uses them to sketch a framework for understanding the important NP core and surface properties that affect Ln3+ luminescence. A charge trapping mediated Ln3+ emission sensitization mechanism is shown to operate in both the synthetically doped and postsynthetically modified NPs, and it is strongly affected by the energy offsets between the lanthanide and NP electronic states. While both the host (semiconductor NP) and guest (Ln3+) properties must be considered in designing and controlling the photophysical outcome, the predictable trends in Ln3+ energetics make it possible to predict trends and behaviors semiempirically. The role of spectral overlap mediated energy transfer mechanisms are shown to contribute negligibly to the sensitization. Proof of principle experiments to uncover the roles of surface localized dopants and surface capping ligands in governing the dopant emission, and the realization of emission from distinct Ln3+ in a codoped assembly, are discussed.

Room temperature doping of Ln3+ in perovskite nanoparticles: a halide exchange mediated cation exchange approach

“…4d), which display Eu 3+ emission bands at 590, 616, and 700 nm that correspond to the 5 D 0 → 7 F J ( J = 1, 2, 4) transitions (Eu 3+ emission quantum yields range from 0.1-0.15%). 11,12,24 The excitation spectra obtained by monitoring the Eu 3+ emission band at 616 nm and the exciton emission band at 410 nm show a strong overlap (see Fig. S5 †) which confirms that the Eu 3+ emission is sensitized by the host NP.…”

“…4c) display Tb 3+ emission bands at 490, 545, 585, and 620 nm that originate from the 5 D 4 → 7 F J ( J = 6-3) transitions. 11,12,24 The excitation spectra of the CsPbBr 3 /TbCl 3 NPs, which are generated by monitoring the perovskite centered emission transition at 410 nm and the Tb 3+ emission band at 545 nm, show significant overlap (see Fig. S5 †), indicating that the host NP sensitizes the Tb 3+ emission.…”

“…The post-synthetic introduction of Ln 3+ in traditional II-VI semiconductor NPs and the investigation of their corresponding photophysical properties has been explored by us in detail. [22][23][24] However, reports on the post-synthetic Ln 3+ doping at room temperature in perovskite NPs are scant, with studies mostly discussing Yb 3+ doping in CsPbX 3 NPs (X = Cl, Br, I). 25,26 This work describes a convenient post-synthetic strategy, which uses simultaneous halide and cation exchange, to generate Ln 3+ [Ln = Nd, Sm, Eu, Tb, Dy, and Yb] doped CsPbBr 3 and CsPbCl 3 nanocrystals, which we refer to as CsPbBr 3 /LnCl 3 and CsPbCl 3 /LnCl 3 .…”

Remarkable difference in pre-cation exchange reactions of inorganic nanoparticles in cases with eventual complete exchange

“…By performing a series of experiments with hydrophobic Zn(Ln)S [Ln = Eu, Tb], 32 II-VI sulfides and selenides, 32 Zn(Tb)S NPs of varying size, 33 hydrophilic Zn(Ln)S [Ln = Sm, Eu, Tb, Dy] NPs, 34 Ti(Ln)O 2 [Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb] NPs, 55 near band gap-matched Sn(Ln)O 2 and Zn(Ln)S [Ln = Sm, Tb] NPs, 30 Sn(Ln)O 2 [Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb] NPs, 56 ZnS/Ln and CdSe/Ln [Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb] NPs, 36 and alloyed Zn 1Àx Cd x (Tb)S NPs, 25 we have argued that Ln 3+ emission sensitization in semiconductor NPs operates through a charge trapping-mediated photophysical pathway; in this process, the spectral overlap between the donor NP emission and acceptor Ln 3+ absorption is insignificant. 28,30,32,33 In the charge trapping-mediated dopant emission sensitization process, the Ln 3+ ground and luminescent energy levels need to be optimally placed above and below the valence and conduction band of the host material, respectively, to ensure the efficient colocalization of photogenerated holes and electrons at the Ln 3+ -related trap site. Subsequent electron-hole pair recombination at the Ln 3+ trap site populates the dopant luminescent energy level, thus generating the host-sensitized dopant emission from the composite doped NP assemblies.…”

Влияние Ионов Неодима (III) На Фотолюминесценцию Сульфидов Кадмия И Цинка В Полиакрилатной Матрице

“…Востребованными оптическими активаторами являются ионы лантанидов. Они применяются в сочетании с неорганическими полупроводниками [25][26][27][28][29][30][31]. Исследованы преимущественно КТ, легированные ионами Eu 3+ и Tb 3+ .…”