“…The bi-exponential fitting of room temperature fluorescence decay curves for LiIn 1.97 SbO 6 :0.03Cr 3+ is shown in Figure 3 D. The average lifetime was calculated to be 4.54 μs based on the following relationships: where I represents the emission intensity, A 1 and A 2 are constants, τ 1 and τ 2 are the decay time for the exponential components, and τ ave is the average decay time. The fitting results (τ 1 = 3.86 μs and τ 2 = 21.65 μs) are in line with the typical Cr 3+ -doped compounds, and the shorter one is regarded as intrinsic ionic luminescence when the influence of temperature is taken into consideration ( Gao et al., 2020 ). Figure 3 Temperature-dependent PL spectra and fluorescence decay curves of LiIn 2- x SbO 6 : x Cr 3+ ( x = 0.01 - 0.12) (A and B) Normalized temperature-dependent PL spectra and fluorescence decay curves of LiIn 1.97 SbO 6 :0.03Cr 3+ under 492-nm excitation between 15 and 300 K, respectively.…”
Section: Resultssupporting
confidence: 78%
“…Since the optical performance of NIR pc-LEDs mainly depends on the phosphors used, intensive efforts have been made to exploit broadband NIR phosphors via rare-earth ion- (Eu 2+ ), transition metal ion- (Cr 3+ , Ni 2+ , Mn 2+ , Fe 3+ ), or Bi ion (Bi + , Bi 3+ )-activated inorganic matrices ( Tang et al., 2020 ; Gao et al., 2020 ; Song et al., 2019 ; Wei et al., 2020 ; Guan et al., 2020 ). Unfortunately, single invisible fluorescence emissions of Eu 2+ , Mn 2+ , and Fe 3+ ions are hard to acquire, and their emissions FWHM are insufficient ( Berezovskaya et al., 2013 ; Song et al., 2015 ; Zhou et al., 2020 ).…”
Summary
Near-infrared (NIR) phosphor-converted light-emitting diode (pc-LED) has great potential in non-invasive detection, while the discovery of tunable broadband NIR phosphor still remains a challenge. Here, we report that Cr
3+
-activated LiIn
2
SbO
6
exhibits a broad emission band ranging from 780 to 1400 nm with a full width at half maximum (FWHM) of 225 nm upon 492 nm excitation. The emission peaks are tuned from 970 to 1020 nm together with considerable broadening of FWHM (∼285 nm) via Li/Na substitution. Depending on Yb
3+
co-doping, a stronger NIR fluorescence peak of Yb
3+
appears with improved thermal resistance, which is ascribed to efficient energy transfer from Cr
3+
to Yb
3+
. An NIR pc-LED package has been finally designed and demonstrated a remarkable ability to penetrate pork tissues (∼2 cm) so that the insertion depth of a needle can be observed, indicating that the phosphor can be applied in non-destructive monitoring.
“…The bi-exponential fitting of room temperature fluorescence decay curves for LiIn 1.97 SbO 6 :0.03Cr 3+ is shown in Figure 3 D. The average lifetime was calculated to be 4.54 μs based on the following relationships: where I represents the emission intensity, A 1 and A 2 are constants, τ 1 and τ 2 are the decay time for the exponential components, and τ ave is the average decay time. The fitting results (τ 1 = 3.86 μs and τ 2 = 21.65 μs) are in line with the typical Cr 3+ -doped compounds, and the shorter one is regarded as intrinsic ionic luminescence when the influence of temperature is taken into consideration ( Gao et al., 2020 ). Figure 3 Temperature-dependent PL spectra and fluorescence decay curves of LiIn 2- x SbO 6 : x Cr 3+ ( x = 0.01 - 0.12) (A and B) Normalized temperature-dependent PL spectra and fluorescence decay curves of LiIn 1.97 SbO 6 :0.03Cr 3+ under 492-nm excitation between 15 and 300 K, respectively.…”
Section: Resultssupporting
confidence: 78%
“…Since the optical performance of NIR pc-LEDs mainly depends on the phosphors used, intensive efforts have been made to exploit broadband NIR phosphors via rare-earth ion- (Eu 2+ ), transition metal ion- (Cr 3+ , Ni 2+ , Mn 2+ , Fe 3+ ), or Bi ion (Bi + , Bi 3+ )-activated inorganic matrices ( Tang et al., 2020 ; Gao et al., 2020 ; Song et al., 2019 ; Wei et al., 2020 ; Guan et al., 2020 ). Unfortunately, single invisible fluorescence emissions of Eu 2+ , Mn 2+ , and Fe 3+ ions are hard to acquire, and their emissions FWHM are insufficient ( Berezovskaya et al., 2013 ; Song et al., 2015 ; Zhou et al., 2020 ).…”
Summary
Near-infrared (NIR) phosphor-converted light-emitting diode (pc-LED) has great potential in non-invasive detection, while the discovery of tunable broadband NIR phosphor still remains a challenge. Here, we report that Cr
3+
-activated LiIn
2
SbO
6
exhibits a broad emission band ranging from 780 to 1400 nm with a full width at half maximum (FWHM) of 225 nm upon 492 nm excitation. The emission peaks are tuned from 970 to 1020 nm together with considerable broadening of FWHM (∼285 nm) via Li/Na substitution. Depending on Yb
3+
co-doping, a stronger NIR fluorescence peak of Yb
3+
appears with improved thermal resistance, which is ascribed to efficient energy transfer from Cr
3+
to Yb
3+
. An NIR pc-LED package has been finally designed and demonstrated a remarkable ability to penetrate pork tissues (∼2 cm) so that the insertion depth of a needle can be observed, indicating that the phosphor can be applied in non-destructive monitoring.
“…The co-substitution changes the crystal field of Cr 3+ ions in the Ga 2 O 3 host, which can be explained using the Tanabe–Sugano theory. 6,38–40 The crystal field Dq and the Racah parameter B can be calculated as follows: 17,37 …”
Here, the method "chemical unit co-substitution" is used to improve the near-infrared (NIR) emission of phosphors, using [Zn2+ - Ge4+] to co-substitute [Ga3+ - Ga3+] sites to reduce crystal field...
“…Meanwhile, the FWHM of La 3– x Gd x Ga 5 GeO 14 :0.02Cr 3+ phosphor PL spectra can be enhanced significantly from ∼262.0 to ∼368.0 nm. Therefore, the increase of Cr 3+ emission intensity and the increased FWHM of the Cr 3+ spectra can be explained by two possible reasons: (1) the introduction of Gd 3+ ions can decrease the crystal field and (2) the introduction of Gd 3+ ions can promote the cosubstitution of Cr 3+ ions at the different Ga 3+ sites and then suppress the nonirradiation process …”
Wearable biosensing and food safety inspection devices with high thermal stability, high brightness, and broad near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) could accelerate the next-generation NIR light applications. In this work, NIR La 3−x Gd x Ga 5 GeO 14 :Cr 3+ (x = 0 to 1.5) phosphors were successfully fabricated by a high-temperature solid-state method. Here, by doping Gd 3+ ions into the La 3+ sites in the La 3 Ga 5 GeO 14 matrix, a 7.9-fold increase in the photoluminescence (PL) intensity of the Cr 3+ ions, as well as a remarkably broadened full width at half-maximum (FWHM) of the corresponding PL spectra, is achieved. The enhancements in the PL, PLE intensity, and FWHM are attributed to the suppression of the nonradiative transition process of Cr 3+ when Gd 3+ ions are doped into the host, which can be demonstrated by the decay curves. Moreover, the La 1.5 Gd 1.5 Ga 5 GeO 14 :Cr 3+ phosphor displays an abnormally negative thermal phenomenon that the integral PL intensity reaches 131% of the initial intensity when the ambient temperature increases to 160 °C. Finally, the broadband NIR pc-LED was fabricated based on the as-explored La 1.5 Gd 1.5 Ga 5 GeO 14 :Cr 3+ phosphors combined with a 460 nm chip, and the potential applications for the broadband NIR pc-LEDs were discussed in detail.
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