The internal modification with rare earth ion doping proved to be a very effective strategy for improving the luminescent properties of NaYF 4 -based upconversion materials. However, greatly enhancing the luminescence efficiency of NaYF 4 :Yb 3+ /Er 3+ remains a major challenge. Herein, the effects of Sn 4+ doping on the structure and luminescent performance of such material were explored. The hydrothermal molten-salt method was applied to synthesize the Sn 4+ -doped NaYF 4 :Yb 3+ /Er 3+ upconversion materials, and their crystal structures, morphologies, surface chemical composition and element states, and luminescence performance were characterized. It was found that Sn 4+ doping can significantly enhance the luminescence intensity and tailor the chromaticity of NaYF 4 :Yb 3+ /Er 3+ . In particular, the green (G) and red (R) luminescence intensity levels of the 30 mol% Sn 4+ doped material were increased by factors of 26.97 and 38.91, respectively. The R/G ratio was incremented from 0.34 for the undoped material to 0.83 for the 40 mol% Sn 4+ doped counterpart. The Sn 4+ doping led to the change of lattice distortion and crystal growth pattern of NaYF 4 :Yb 3+ /Er 3+ . The mechanism for Sn 4+ doping to affect the luminescence properties of the prepared upconversion material was also explored. The changes in luminescence intensity levels and R/G ratios could be attributed to the highly asymmetric distorted lattice and crystal field resulting from Sn 4+ doping.
Ion doping represents a viable strategy for improving the photocatalytic performance of semiconductor materials. This study successfully synthesized Sn 4+ -doped Bi 4 O 5 I 2 photocatalysts through an in-situ calcination approach. Structural characterization confirmed that Sn 4+ incorporation induced lattice contraction while increasing the density of active surface sites. Photocatalytic evaluation revealed that the 10 % Sn-BOI catalyst achieved 95.4 % levofloxacin (LOFX) degradation within 40 min under visible light irradiation, exhibiting a reaction rate constant (k) 5.2-fold greater than undoped Bi 4 O 5 I 2 . The catalyst demonstrated excellent stability, retaining high activity through four consecutive recycling tests. Mechanistic studies showed that oxygen vacancies (OVs) generated during doping modified the electronic structure by elevating the valence band maximum and narrowing the bandgap, while simultaneously promoting charge separation through electron trapping. These findings establish an effective methodology for developing photocatalysts to address antibiotic pollution in wastewater.
Near-infrared (NIR) spectroscopy has significantly advanced NIR light sources. However, creating NIR emitters with optimal luminescence properties, high thermal stability, and adjustable emission peaks poses a critical challenge for future smart NIR devices. We introduced a chemical unit cosubstitution strategy by incorporating Ca 2+ and Sn 4+ ions into the garnet structure. Through this approach, Y 3− y Ca y Ga 4.95− y Sn y G 12 :0.05Cr 3+ ( y = 0–1) phosphors were developed by modulating the A&C ligands, resulting in emission centers ranging from 708 to 768 nm. The modified local environment of Cr 3+ accounts for the increased light intensity (2.71 times) and broadening observed. Furthermore, this study investigated the impact of varying Cr 3+ concentrations (Y 2.6 Ca 0.4 Ga 4.6− x Sn 0.4 G 12 : x Cr 3+ ) on the production of high-performance phosphors. Compared with Y 3 Ga 4.93 G 12 :0.07Cr 3+ , the optimized phosphor exhibited exceptional external quantum efficiency (EQE = 34.96%). The luminescence enhancement is attributed to an increase in radiative transitions caused by octahedral Jahn-Teller distortion, whereas the notable thermal stability (91.3% at 423 K) is attributed to the presence of weak electron-phonon coupling (EPC) and oxygen vacancy (O V ) defects. Finally, by combining it with a 450 nm blue LED chip, we constructed a near-infrared phosphor-converted LED (NIR pc-LED) device with superior electroluminescence efficiency (18.8% @ 100 mA), increasing the ultralow quenching rate (< 5% intensity loss after 30 days of operation) and demonstrating remarkable performance in plant lighting applications.
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