A dual-excited and dual near-infrared emission phosphor Mg₁₄Ge₅O₂₄:Cr³⁺,Cr⁴⁺ with a super broad band for biological detection

Abstract

Recently, near-infrared phosphors that can be applied in many fields such as night vision, agriculture, and bio-applications have attracted considerable interest in the research field worldwide. Herein, a multi-functional and...

Efficient Ultra‐Broadband Ga4GeO8:Cr3+ Phosphors with Tunable Peak Wavelengths from 835 to 980 nm for NIR pc‐LED Application

“…[ 12 ] After Cr 3+ doping, three absorption bands are observed at ≈300, 430, and 620 nm, which are attributed to 4 A 2 → 4 T 1 ( 4 P ), 4 A 2 → 4 T 1 ( 4 F ) and 4 A 2 → 4 T 2 ( 4 F ) transitions of Cr 3+ respectively. The absorption of Cr 4+ (>900 nm) is not found in DR spectra, [ 4g,9 ] which agrees with the results of XPS and EPR.…”

“…[ 6f,8 ] Another strategy is the introduction of Cr 4+ ions, such as Mg 2 GeO 4 :Cr 3+ , Cr 4+ , Mg 14 Ge 5 O 24 :Cr 3+ , Cr 4+ , and SrGa 4 O 7 :Cr 3+ , Cr 4+ . [ 9 ] Nevertheless, Cr 4+ ions show intensive absorption in the NIR spectral range, resulting in a decreased QY due to the re‐absorption. Multiple crystallographic site occupation by Cr 3+ is considered as another effective method to reach large bandwidth and high QY simultaneously.…”

Broadband Short-Wave Infrared Light-Emitting Diodes Based on Cr3+-Doped LiScGeO4 Phosphor

“…Tetravalent chromium (Cr 4+ ) is also a promising luminescent center for SWIR photoluminescence because of its broadband and tunable emissions in a wavelength range over 1100–1700 nm as a result of the characteristic 3 T 2 → 3 A 2 electronic transition . The broadband SWIR emission form Cr 4+ is mainly found in laser crystals and glasses, including Y 3 Al 5 O 12 :Cr 4+ crystal and Cr 4+ doped glass ceramics (Zn 2 SiO 4 , Mg 2 SiO 4 , Li 2 ZnSiO 4 , Li 2 MgSiO 4 , and Ca 2 GeO 4 :Cr 4+ ). , Recently, a handful of Cr 4+ -doped ceramic phosphors have been reported by introducing Cr 4+ into tetrahedral sites intentionally or unintentionally. ,− However, SWIR light emission beyond 1000 nm from Cr 4+ usually coexists with the dominant Cr 3+ NIR light emission. By far, although there are increasing interests for advanced applications ranging from night vision imaging to SWIR detection application, the research progress on the development and application of chromium (Cr 3+ /Cr 4+ )-doped phosphors in the SWIR is rather slow…”

Crystallographic control for Cr4+ activators toward efficient NIR-II luminescence

“…The fitted lifetime value is 90.1 μs. The crystal field strength can be roughly estimated using the following equations: 30,40…”

“…Unlike rareearth doped NIR-II phosphors, Cr 4+ -doped phosphors such as Mg 2 SiO 4 :Cr 4+ , Ca 2 Al 2 SiO 7 :Cr 4+ and Mg 14 Ge 5 O 24 :Cr 4+ show broadband emission ranging from 1000 to 1400 nm with a peak wavelength of over 1200 nm. [28][29][30] However in inorganic compounds, the chromium ions show a strong tendency to locate at octahedral sites and form a trivalent state. 31 Thus, the Cr 4+ NIR-II luminescence may be deteriorated with the existence of octahedral sites in a host lattice.…”