Bo-Mei Liu,Xiao-Xuan Guo,Lu-Yu Cao,Lin Huang,Rui Zou,Zhi Zhou,Jing Wang
The development of phosphor-converted light-emitting diodes (pc-LEDs) in the second near-infrared window (NIR-II, 1000–1700 nm) represents an important, newly emerging, and dynamic field in NIR spectroscopy. Unfortunately, lacking efficient NIR-II phosphors that can be excited by commercial blue LED chips impedes NIR spectroscopy applications. Herein, a donor–acceptor strategy is developed by introducing Cr 3+ sensitizers to greatly enhance the blue-light excitation efficiency of NIR-II-emitting MgO:Cr 3+ ,Ni 2+ phosphor. Consequently, a high-efficiency blue-light-excitable MgO:Cr 3+ ,Ni 2+ phosphor that gives a NIR-II emission at 1335 nm with a full width at half-maximum (FWHM) of 235 nm, is demonstrated. The product has a high internal quantum efficiency of 92.7 % and excellent thermal stability, maintaining 83.0 % of the room temperature emission intensity at 150 °C. Excitingly, the fabricated NIR-II pc-LED device shows a high NIR-II optical power (27.4 mW@350 mA). The performances of the achieved NIR-II pc-LED are almost the best results until now. Additionally, multifunctional applications including nondestructive detection and anti-counterfeiting of the NIR-II light source are demonstrated. These results are pretty crucial for the further development of NIR-II spectroscopy and imaging technology.
Xin Xu,Peigeng Han,Daoyuan Zheng,Kaimin Du,Chunxia Li,Feng Liu,Ruiling Zhang,Keli Han
Recently, lanthanide-doped halide perovskites have attracted increasing attention due to their unique optical properties, such as upconversion (UC) and near-infrared (NIR) emission. However, these emitters suffer from low efficiency, limiting further practical applications. Herein, a Bi 3+ -alloyed double perovskite, Cs 2 NaEr 0.5 Bi 0.5 Cl 6 , with strong NIR-triggered UC and NIR-II (1000–1700 nm) emission is reported. Cs 2 NaEr 0.5 Bi 0.5 Cl 6 exhibits efficient green UC emission with a high quantum yield up to 2.1% and NIR-II emission peaking at 1541 nm with a quantum yield of 37.9% under 980 nm excitation. The strong UC emission is related with the efficient energy transfer between Er 3+ and self-trapped exciton states induced by corporation of Bi 3+ ions. In addition, Bi 3+ ions can act as diluters, suppressing the energy loss caused by undesirable successive energy transfer among Er 3+ ions, enhancing the UC and NIR-II emission. Furthermore, a water-resistant Cs 2 NaEr 0.5 Bi 0.5 Cl 6 /polydimethylsiloxane film is prepared. Excitingly, Cs 2 NaEr 0.5 Bi 0.5 Cl 6 not only shows the potential as a UC thermometry with high sensitivity but also exhibits a high signal to noise ratio in NIR imaging.
Fluorescent imaging in the second near-infrared region (NIR-II, 1000–1700 nm) is optimal for in vivo imaging due to their low autofluorescence and weak tissue scattering. Recently, many efforts have been paid in search of NIR-II emitting agents. Herein, we report a facile one-pot approach for the synthesis of NIR-II emissive Ag 2 S quantum dots (QDs). The effect of ligand was carefully investigated to improve the quality of QDs. It is found that the QDs tend to form clusters when 1-dodecanethiol was used as the only ligand. The addition of oleic acid can greatly improve the dispersity of the nanocrystals but lead to a significantly decrease of the emission intensity. Meanwhile, the present of small amount of oleylamine can prevent the formation of undesired silver nanoparticles and improve the fluorescent intensity at high temperature. Whole-body blood vessel imaging and tumor imaging were performed with these biocompatible Ag 2 S QDs after PEGylation to demonstrate their potentials in vivo .
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