Crystallographic control for Cr 4+ activators toward efficient NIR-II luminescence

Laser & Photonics Reviews

2022

Self Cite

202

145

Cr3+/Cr4+‐activated near‐infrared (NIR) luminescent materials have attracted extensive attention owing to their tunable emission wavelength and widespread applications in plant growth, food analysis, biomedical imaging, night vision, and so on. Plenty of excellent NIR materials are developed by introducing Cr3+/Cr4+ ion to various inorganic hosts. Herein, the effect of crystal field on Cr3+/Cr4+ luminescence by combining the Tanabe–Sugano energy level diagram and configuration coordinate model is discussed. Research progress of Cr3+/Cr4+‐doped NIR luminescent materials, including the phosphors designed from structural models with octahedral, tetrahedral, and other coordination types, is then outlined. The luminescence properties of more than 200 kinds of Cr3+/Cr4+‐doped materials are summarized. In particular, several strategies for tuning emission wavelength, broadening emission band, enhancing NIR luminescence efficiency, and improving thermal stability, are listed. Finally, the current challenges and future prospects in the research of Cr3+/Cr4+‐doped NIR luminescent materials are presented. This review will contribute to a deeper understanding of not only Cr3+/Cr4+ luminescence mechanism but also the current research progress of chromium‐doped luminescent materials, so as to develop more Cr3+/Cr4+‐activated NIR luminescent materials with better performance and explore more applications.

Section: Advances In Chromium‐activated Phosphors: Structure Properti...mentioning

confidence: 99%

Section: Selection Of Host Materialsmentioning

confidence: 99%

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Advances in Chromium‐Activated Phosphors for Near‐Infrared Light Sources

Zhao

Song

Laser & Photonics Reviews

2022

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202

145

“…[7] Inorganic compounds, doped by such transition-metal-elements as Cr 3+ , Cr 4+ , and Mn 5+ , received intense research due to their characteristic NIR luminescence and important Laser applications. [8][9][10][11][12] Besides, compared to the sharp-line absorption of rare-earth elements which could also emit NIR light, these transition-metal elements have wide-band absorptions. [13,14] As a result, it is becoming a widespread trend DOI: 10.1002/adts.202200466 to integrate transition-metal elements doped materials with light-emitting-diodes to fabricate compact NIR devices.…”

Section: Introductionmentioning

confidence: 99%

“…[16,17] Compared to Cr 3+ , Cr 4+ and Mn 5+ with 3d 2 configuration could have NIR luminescence at much longer wavelength range, but in most cases Cr 4+ and Mn 5+ are accommodated in tetrahedral sites. [8,18] Therefore, it is an urgent challenge to establish the T-S diagrams of 3d 2 configuration in tetrahedron in order to promote further development of Cr 4+ or Mn 5+ doped NIR materials. The understanding and interpretation of 3d 2 luminescence is facing several problems.…”

Section: Introductionmentioning

confidence: 99%

Energy Level Diagram of 3d² Configuration in Tetrahedral Crystal Field and Its Applications to Cr^{4 +} /Mn^{5 +} ‐Doped Luminescent Materials

Song

2022

Advcd Theory and Sims

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Tanabe–Sugano diagram is a successful guideline for the energy levels of 3dn electrons for half a century. However, it is developed only under the regular octahedral crystal field. With the surging research interests in the near‐infra‐red luminescence of 3d block transition‐metal elements, it becomes an urgent demand to know the energy level diagram of Cr4 + and Mn5 + with 3d2 configuration, which are usually embedded in the tetrahedral site due to the smaller ionic size. Although the Tanabe–Sugano diagram of 3d8 configuration in octahedron is usually used as a substitution for that of 3d2 configuration in tetrahedron, the result mismatches with the crystal field strength and emission profile. In this work, irreducible tensor operator method is applied to derive the full analytical expressions of 3d2 energy levels in the tetrahedral crystal field, based on which the Tanabe–Sugano diagram of 3d2 configuration in tetrahedron is built for the first time. Also provided is a set of formulas for fast estimation of Dq/B$Dq/B$ values, which shows consistency between the crystal field strength and the emission profile among Cr4+, Mn5+‐doped luminescent materials. As it is hoped, this work could provide more deep insights into the luminescence of 3d2 elements.

NIR Mechanoluminescence from Cr³⁺ Activated Y₃Al₅O₁₂ with Intense Zero Phonon line

Peng

et al. 2023

Adv Funct Materials

Mechanoluminescence (ML) materials with long-wavelength emission bands are essential for future in vivo bioimaging, non-destructive testing of solids, etc. The lack of a defined mechanism, however, prevents the application of near infrared ML materials above 650 nm in several new fields. Here, the addition of Ga 3+ ions to Y 3 Al 5 O 12 : Cr 3+ manipulates matrix microstructure evolution, boosting near-infrared (NIR) zero-phonon line (ZPL) stress optical output of the Cr 3+ ion at 688 nm. The key factor changing the crystal field intensity D q /B due to the addition of Ga 3+ ions is what causes the luminescence amplification of ZPL. The ML fabricated by composite polydimethylsiloxane and Y 3 Al 4 GaO 12 : Cr 3+ (YAGG: Cr 3+ ) may penetrate chicken feet epidermal tissue and 4 mm pork tissue thanks to the strong NIR ZPL emission of YAGG: Cr 3+ phosphor. This discovery of enhancing near-infrared ZPL intensity by solid solution provides us with a new technique for optimizing NIR ML materials, as well as a new prospect for NIR ML materials in biological applications.