Recent Progress in Lanthanide-Doped Inorganic Perovskite Nanocrystals and Nanoheterostructures: A Future Vision of Bioimaging

Abstract

All-inorganic lead halide perovskite nanocrystals have great potential in optoelectronics and photovoltaics. However, their biological applications have not been explored much owing to their poor stability and shallow penetration depth of ultraviolet (UV) excitation light into tissues. Interestingly, the combination of all-inorganic halide perovskite nanocrystals (IHP NCs) with nanoparticles consisting of lanthanide-doped matrix (Ln NPs, such as NaYF₄:Yb,Er NPs) is stable, near-infrared (NIR) excitable and emission tuneable (up-shifting emission), all of them desirable properties for biological applications. In addition, luminescence in inorganic perovskite nanomaterials has recently been sensitized via lanthanide doping. In this review, we discuss the progress of various Ln-doped all-inorganic halide perovskites (LnIHP). The unique properties of nanoheterostructures based on the interaction between IHP NCs and Ln NPs as well as those of LnIHP NCs are also detailed. Moreover, a systematic discussion of basic principles and mechanisms as well as of the recent advancements in bio-imaging based on these materials are presented. Finally, the challenges and future perspectives of bio-imaging based on NIR-triggered sensitized luminescence of IHP NCs are discussed.

Keywords: inorganic perovskite; lanthanide-doped nanocrystals; nanoheterostructure; upconversion photoluminescence.

Figure 1

Structural features for metal halide perovskites. (a) Unit cell of general cubic perovskite; (b) MAPbI₃ with octahedral coordination around lead ions; (c) MAPbI₃ with cuboctahedra coordination around organic ions. Reprinted with permission [27]. Copyright 2017, Royal Society of Chemistry.

Figure 2

(a) Colloidal CsPbX₃ NCs (X = Cl, Br and I) in toluene under UV lamp (λ = 365 nm); (b) corresponding PL spectra (λ_exc = 400 nm for all but 350 nm for CsPbCl₃ NCs); (c) optical absorption, PL spectra and inset images for CsPbCl₃, CsPbBr₃ and CsPbI₃ nanoplatelets. Reprinted with permission [49,50]. Copyright 2016, John Wiley & Sons and 2015, American Chemical society.

Figure 3

UC properties of KMgF₃:Yb³⁺, Er³⁺ UCNCs. (a) A spectrum of single-band red UC emission; (b) UC emission spectra with various doping concentrations; (c) UC emission spectra with various excitation powers; (d) the corresponding logarithmic plot between UC intensity and excitation power. Reprinted with permission [62]. Copyright 2016, Royal Society of Chemistry.

Figure 4

(a) UC emission of RbPbI₃:Er³⁺ (10 at.%), Yb³⁺ with different doping concentrations of ytterbium under an excitation at 980 nm; (b) transition mechanism of UC process (RbPbI₃:Er³⁺,Yb³⁺) at 980 nm excitation. Reprinted with permission [64]. Copyright 2018, American Institute of Physics.

Figure 5

Investigation on the RET process in NP-sensitized CsPbX₃ perovskite NCs. (a) CsPbBr₃ concentration-dependent UCL spectra for LiYbF₄:0.5%Tm³⁺@LiYF4 core/shell NP (1 mg·mL⁻¹)-sensitized CsPbBr₃ perovskite NCs excited at 980 nm; (b) integrated intensities for Tm³⁺ emissions and CsPbBr₃ emission at 520 nm vs. the CsPbBr₃ concentration from (a); (c) UCL decays from ¹D₂ of Tm³⁺ by monitoring the Tm³⁺ emission at 362 nm in NP-sensitized CsPbBr₃ perovskite NCs with various concentrations excited at 980 nm; (d) UCL lifetimes of ¹I₆, ¹D₂ and ¹G₄ of Tm³⁺ in NP-sensitized CsPbBr₃ perovskite NCs vs. the CsPbBr₃ concentration. Reprinted with permission [74]. Copyright 2018, Nature Publishing.

Figure 6

(a) UC emission spectra for CaF₂:Yb³⁺ (20%)/Ho³⁺ (x%) HNSs; (b) absorption and excitonic emission spectra for CsPbI₃ perovskite NCs; (c) UC emission spectra for HNS-perovskite NCs; dynamics of emissions for CsPbI₃ perovskite NCs at (d) 540 nm, (e) 695 nm and (f) 695 nm; (g) calculated energy transfer efficiency of HNS-perovskite NCs with various times obtained from (c,d); (h) mechanism of UC emission in CsPbI₃ and CaF₂:Yb³⁺/Ho³⁺ composites. Reprinted with permission [76]. Copyright 2021, Elsevier.

Figure 7

(a) Schematic diagram for the detection of temperature and emission spectrum of Ln NP-Ce6@mSiO₂-CuS incubated with cells in physiological range; (b) UC emission spectra for Ln NP-Ce6@mSiO₂-CuS incubated with cells at various temperatures by external heating; (c) finite impulse response (FIR) of green UC emissions for ²H_11/2/⁴S_3/2→⁴I_15/2 transitions based on the temperature of Ln NP-Ce6@mSiO₂-CuS incubated with cells (inset: AFM image of cell after spectral detection); (d) a plot of ln(I₅₂₅/I₅₄₅) versus 1/T to calibrate the thermometric scale for Ln NP-Ce6@mSiO₂-CuS incubated with cells. Reprinted with permission [89]. Copyright 2019, Elsevier.