Trivalent rare earth ions (Ln3+) have the unique electronic configurations [Xe]4fn (n = 0–14) and numerous energy levels, which endow rare earth luminescent materials with many fascinating optical properties over a broad spectral region ranging from the ultraviolet (UV) to the near infrared (NIR); these include tunable atomic-like excitation/emission spectra, large Stokes/anti-Stokes shifts, long luminescent lifetimes, and excellent photostability1,2,3,4. In the 1960s, thanks to breakthroughs in purification technology, rare earth luminescent materials were successfully applied in lamps and cathode-ray tubes as original phosphors5. Since then, with continuous and important progress arising from research on rare earth luminescent materials, applications have consistently been expanded. Today, rare earth luminescent materials are used in almost every aspect of photonics and optoelectronics, for example, in lighting6,7, displays8,9, sensing10, optical information storage11, energy conservation12, and biomedicine13,14. This booming momentum prompted us to edit this album and summarize the latest progress in a timely manner and provide a reference for further developments with rare earth luminescent materials. This special issue includes a series of cutting-edge, high-quality original research reports and timely authoritative reviews of relevant progress involving mainly lanthanide ion-doped phosphors, persistent luminescent materials, lanthanide ion-doped upconversion materials, rare earth luminescent complexes, rare earth-relevant perovskite materials, and their applications in lighting, displays, information storage, sensing, and bioimaging/therapy.
For light-emitting diode (LED) applications, rare earth luminescent materials with high photoluminescence quantum yields, good stabilities, and broad luminescence spectra ranging from the visible (Vis) to the NIR region are highly desired. Shortwave infrared (SWIR) emission was realized by Zhang and coworkers when they doped Cr3+-Yb3+ ion pairs into Lu0.2Sc0.8BO3 host materials15. The SWIR phosphor Lu0.2Sc0.8BO3:Cr3+, Yb3+ exhibited high luminescence efficiency and good thermal stability, which endowed the fabricated SWIR LEDs with good performance characteristics. They further explored applications in nondestructive inspections, chemical analyses, anticounterfeiting and night vision lighting. Jin and coworkers discovered that a combination of self-trapped exciton (STE) recombination of Cs2AgInCl6 with Ln3+ dopant-induced extra light-emitting channels resulted in Vis-NIR (400–2000 nm) ultrabroadband emission from lead-free halide double perovskites (DPs)16. The fabricated LEDs featured cost-effective fabrication, compactness, excellent optical performance and extreme long-term stability compared to reported ultrabroadband light sources and showed promise for application in nondestructive spectroscopic analyses and multifunctional lighting. In addition to traditional LEDs driven by direct current (DC), alternating current light-emitting diodes (AC-LEDs) have aroused considerable interest because they can offer a more compact volume, lower production price, higher energy utilization efficiency and a longer service lifetime. To achieve white light emission during dimming time, Yuan and coworkers developed a promising strategy for building AC-LED lamps by adding a blue-light excited blue persistent luminescence (PersL) phosphor to the commercial orange‒red PersL phosphor17. Intense white PersL emission was observed during dimming time, with a substantial reduction in the flicker percentage.
High sensitivity, convenient use, rapid responses, and remote and noncontact properties are features of optical thermometers based on temperature-dependent spectroscopic properties, which have attracted increasing attention. However, the conventional luminescent materials applied often show background fluorescence interference due to UV/Vis light excitation. Lanthanide-doped inorganic upconversion nanoparticles (UCNPs) excitable with NIR light sources are regarded as promising alternatives with which to circumvent background fluorescence and stray light. In this special issue, An and coworkers report a novel one-step approach for synthesizing hollow structured UCNPs without a template18. These hollow UCNPs could act as stable self-referenced ratiometric luminescent thermometers over a broad temperature range. In addition to exploring new luminescent probes, progress has been made in relevant data processing methodologies. The power of dimensional reduction (DR) in analyses of the emission spectra for lanthanide-doped nanothermometers was demonstrated by Ximendes and coworkers19. Higher thermal resolution was achieved, and this may constitute a paradigm shift in the field of luminescence thermometry, particularly because it was shown that the method is applicable to rare earth luminescent materials and to semiconductor nanocrystals such as Ag2S.
Luminescent biodetection is another important application area for rare earth luminescent materials. Typical examples are UCNPs, where Förster resonance energy transfer (FRET) is one of the popular mechanisms adopted. Kotulska and coworkers illustrated the impact of core-shell compositional architectures of UCNPs and the mode of photoexcitation on the realization of UC-FRET from UCNPs to Rose Bengal (RB)20. They found that short pulsed excitation and risetime measurements provided highly sensitive assays, stressing the importance of UCNP compositional architecture for donors used to improve either the steady-state luminescence intensity or kinetic responses of UC-LRET-based assays.
Benefiting from the sharp emission and theoretical 100% internal quantum efficiency, rare earth luminescent complexes have been intensively explored over the past three decades for use in the field of electroluminescence. A typical example is organic light-emitting diodes (OLEDs). Li and coworkers presented an overview of recent advances in the use of rare earth luminescent complexes in OLEDs21. This review introduces the luminescent characteristics of rare earth complexes and their electroluminescent mechanisms and emphatically highlights innovative applications of rare earth luminescent complexes as sensitizers in OLEDs, including sensitizing mechanisms and the development of rare earth complex-sensitized OLEDs.
As we entered the 21st century, nano research on rare earth luminescent materials began to unfold rapidly. One such field is optical information storage. A brand new optical storage medium composed of UCNPs and EuSe semiconductors was prepared by Xie and coworkers22, in which the emission spectrum was excitation wavelength dependent. The long lifetime upconversion emission was filtered by time-gating technology, and the possibilities for modulating the emission colors of the nanocomposites were further expanded. Based on the multicolor tunable luminescence spectrum, the nanocomposites act as optical modules to load optical information. Furthermore, the application of rare earth-doped luminescent crystals in quantum information processing has taken a big step in the past decade with the aid of electronic-nuclear hyperfine levels, for which information on the hyperfine and superhyperfine interactions, isotopic effects, inhomogeneous line shapes, and random lattice strains in a crystal is essential. Boldyrev and coworkers presented the first direct observation of well-resolved hyperfine structure with the photoluminescence spectra of LiYF4:Ho single crystals and anti-crossings of hyperfine levels in a magnetic field from low-temperature high-resolution Fourier spectroscopy and a special technique for luminescence detection23. The results highlighted the possibility of creating a magnetic-field sensor for quantum memory devices operating at low temperatures and evaluating random lattice deformations in crystals for quantum information devices.
Rare earth luminescent materials have also exhibited potential for applications in biomedicine, especially in the diagnosis and treatment of diseases, due to their unique optical properties, superior magnetism, and high X-ray absorption coefficients. For example, rare earth NIR luminescent materials and UCNPs are regarded as potential medical theranostic platforms for diagnosis and treatment of brain diseases since NIR light can penetrate the skull. One of the challenges is that most drugs and contrast agents cannot reach and accumulate in the lesions owing to protection from the blood‒brain barrier (BBB). In this special issue, Lv and coworkers explore a Nd3+-doped YVO4 nanotheranostic agent with good BBB permeability for bimodality imaging and sonodynamic therapy (SDT) of orthotopic gliomas24. The nanotheranostic agent was used for highly sensitive imaging with high resolution in the second optical window (NIR-II). The role of the MnO2 shell is twofold: on the one hand, it catalyzes the disintegration of H2O2 to release O2, thereby improving SDT treatment, and on the other hand, it releases Mn2+ for tumor microenvironment-responsive T1-weighted magnetic resonance imaging (MRI). To highlight the rational design and application of rare-earth-based materials in brain imaging, therapy, monitoring, and neuromodulation, Wei et al. reviewed recent advances in the use of rare-earth-based materials for theranostic studies of brain disease25. This review discusses the key aspects related to functional design, structural control, and performance enhancement of rare-earth-based materials, presents perspectives and challenges for clinical applications of rare-earth-based materials and indicates that there is ample room for their use in biomedical research.
Combining UCNPs with other functional materials to construct nanocomposites and achieve synergistic effects is an important strategy for strengthening and extending the applications of rare earth luminescent materials. Du and coworkers provided a comprehensive overview of diverse designs for UCNP-based nanocomposites and outlined the pros and cons of different approaches with many instructive examples involving emerging applications in bioimaging, cancer treatments, anticounterfeiting, and photocatalytic fields26.
In conclusion, this special issue focuses on recent progress made with rare earth luminescent materials and considers designs, preparation methods and applications in lighting, displays, sensing, optical information storage, biomedicine, and so on. We hope that this album will encourage more scientists to enter the field of rare earth luminescent materials, which have a wide range of application prospects, inspire scientists to develop new applications and accelerate the development of rare earth luminescent materials. Finally, we would like to express our appreciation to all the authors and reviewers for their excellent contributions and critical reviews.
References
Ward, M. The Rare Earth Elements: Fundamentals and Applications (ed. Atwood, D. A.) Vol. 27, 436 (Wiley-VCH, 2012).
Bünzli, J.-C. G. & Piguet, C. Taking advantage of luminescent lanthanide ions. Chem. Soc. Rev. 34, 1048–1077 (2005).
Binnemans, K. Lanthanide-based luminescent hybrid materials. Chem. Rev. 109, 4283–4374 (2009).
Eliseeva, S. V. & Bünzli, J.-C. G. Lanthanide luminescence for functional materials and bio-sciences. Chem. Soc. Rev. 39, 189–227 (2010).
Shionoya, S. & Yen, W. M. Phosphor Handbook (CRC Press Inc., 1999).
Qin, X., Liu, X., Huang, W., Bettinelli, M. & Liu, X. Chem. Rev. 117, 4488 (2017).
Wei, Y. & Chen, Z. Y. An overview on enhancing the stability of lead halide perovskite quantum dots and their applications in phosphor-converted LEDs. Chem. Soc. Rev. 48, 310–350 (2019).
Deng, R. et al. Temporal full-colour tuning through non-steady-state upconversion. Nat. Nanotechnol. 10, 237–242 (2015).
Wang, L. et al. Rare Earth complexes with 5d-4f transition: new emitters in organic light-emitting diodes. J. Phys. Chem. Lett. 13, 2686–2694 (2022).
Zheng, W. et al. Lanthanide-doped upconversion nano-bioprobes: electronic structures, optical properties, and biodetection. Chem. Soc. Rev. 44, 1379–1415 (2015).
Zhang, C. et al. Luminescence modulation of ordered upconversion nanopatterns by a photochromic diarylethene: rewritable optical storage with nondestructive readout. Adv. Mater. 22, 633–637 (2010).
Huang, X., Han, S., Huang, W. & Liu, X. Enhancing solar cell efficiency: the search for luminescent materials as spectral converters. Chem. Soc. Rev. 42, 173–201 (2013).
Dong, H. et al. Lanthanide nanoparticles: from design toward bioimaging and therapy. Chem. Rev. 115, 10725–10815 (2015).
Zhou, J., Chizhik, A. I., Chu, S. & Jin, D. Single-particle spectroscopy for functional nanomaterials. Nature 579, 41–50 (2020).
Zhang, Y. et al. Blue LED-pumped intense short-wave infrared luminescence based on Cr3+-Yb3+-co-doped phosphors. Light Sci. Appl. 11, 136 (2022).
Jin, S. et al. Compact ultrabroadband light-emitting diodes based on lanthanide-doped lead-free double perovskites. Light Sci. Appl. 11, 52 (2022).
Yuan, W. et al. Enhanced blue-light excited cyan-emitting persistent luminescence of BaLu2Al2Ga2SiO12:Ce3+, Bi3+ phosphors for AC-LEDs via defect modulation. Light Sci. Appl. 11, 184 (2022).
An, R., Liang, Y., Deng, R., Lei, P. & Zhang, H. Hollow nanoparticles synthesized via Ostwald ripening and their upconversion luminescence-mediated Boltzmann thermometry over a wide temperature range. Light Sci. Appl. 11, 217 (2022).
Ximendes, E., Marin, R., Carlos, L. D. & Jaque, D. Less is more: dimensionality reduction as a general strategy for more precise luminescence thermometry. Light Sci. Appl. 11, 237 (2022).
Kotulska, A. M., Pilch-WrĂłbel, A., Lahtinen, S., Soukka, T. & Bednarkiewicz, A. Upconversion FRET quantitation: the role of donor photoexcitation mode and compositional architecture on the decay and intensity based responses. Light Sci. Appl. 11, 256 (2022).
Li, S., Zhou, L. & Zhang, H. Investigation progresses of rare earth complexes as emitters or sensitizers in organic light-emitting diodes. Light Sci. Appl. 11, 177 (2022).
Xie, Y., Song, Y., Sun, G., Hu, P., Bednarkiewicz, A. & Sun, L. Lanthanide-doped heterostructured nanocomposites toward advanced optical anti-counterfeiting and information storage. Light Sci. Appl. 11, 150 (2022).
Boldyrev, K. N., Malkin, B. Z. & Popova, M. N. Observation of the hyperfine structure and anticrossings of hyperfine levels in the luminescence spectra of LiYF4:Ho3+. Light Sci. Appl. 11, 245 (2022).
Lv, Z. et al. A nanotheranostic agent based on Nd3+-doped YVO4 with blood-brain-barrier permeability for NIR-II fluorescence imaging/magnetic resonance imaging and boosted sonodynamic therapy of orthotopic glioma. Light Sci. Appl. 11, 116 (2022).
Wei, Z. et al. Rare-earth based materials: an effective toolbox for brain imaging, therapy, monitoring and neuromodulation. Light Sci. Appl. 11, 175 (2022).
Du, K., Feng, J., Gao, X. & Zhang, H. Nanocomposites based on lanthanide-doped upconversion nanoparticles: diverse designs and applications. Light Sci. Appl. 11, 222 (2022).
Author information
Authors and Affiliations
Corresponding authors
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Zhang, H., Zhang, H. Special Issue: Rare earth luminescent materials. Light Sci Appl 11, 260 (2022). https://doi.org/10.1038/s41377-022-00956-9
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41377-022-00956-9
