Broadband near-infrared (NIR) Cr ³⁺ -doped luminescence materials with long-wavelength emission peak and high thermal stability are being investigated by many researchers because of the applications in non-destructive testing, intelligent identification, night vision, and biomedical imaging. Herein, Li _1.6 (MgZn) _1.6 Sn _2.8 O ₈ :Cr ³⁺ phosphors are prepared in air via high-temperature solid-state method. NIR emission with ~186 nm full width at half maximum is found due to the ⁴ T ₂ ( ⁴ F) → ⁴ A ₂ transition of Cr ³⁺ ion. The co-doped Zn ²⁺ ions can enhance the emission of Li _1.6 Mg _1.6 Sn _2.8 O ₈ :Cr ³⁺ and the improvement rate can reach ~1.9 times because of the minute changes in the crystal field, which is analyzed by the crystal structure. PL peak of Li _1.6 (MgZn) _1.6 Sn _2.8 O ₈ :Cr ³⁺ has a red-shift from 838 to 870 nm with adding Zn ²⁺ content from 0 to 1.6. PLE peaks at ~ 356, 430, and 660 nm manifest that the samples can be excited by the ultraviolet (UV), near-UV, blue, even red light. The optimal Cr ³⁺ concentration is 1 mol% in Li _1.6 Mg _1.6 Sn _2.8 O ₈ :Cr ³⁺ and the optimal Zn ²⁺ content is 0.2 in Li _1.6 (MgZn) _1.6 Sn _2.8 O ₈ :Cr ³⁺ . Li _1.6 (MgZn) _1.6 Sn _2.8 O ₈ :Cr ³⁺ has potential applications in night vision systems and biomedical imaging for diagnosis. This work provides new idea and method for the improvement of other Cr ³⁺ doped luminescent materials.

Antioxidant activity and flavonoid content are important characteristics of colored rice grains. Previously, we obtained a preliminary understanding of the metabolic markers of antioxidant activity, namely, phlorizin and trilobatin, in different colored rice varieties and purple rice grains at different growth stages, but the mechanisms associated with these markers have not yet been confirmed. In this study, purple rice was selected as the experimental material, and clover extract was applied during the grain-filling stage to explore the impact of clover extract on the total antioxidant capacity and flavonoid biosynthesis in purple rice grains. The results indicated that the total flavonoid content, total phenolic content, oligomeric proanthocyanidin content, and total antioxidant capacity of purple rice grains treated with an exogenous application of trilobatin (T30) were significantly greater than those of the control (CK). The flavonoids in the T30 and CK groups accounted for 29.81% of the total flavonoids. The phenylpropanoid biosynthesis and flavonoid biosynthesis metabolic pathways were constructed on the basis of the differentially abundant metabolites between the T30 and CK groups. Additionally, 1-O-sinapoyl-beta-D-glucose, coniferaldehyde, 6″-acetylapiin, and kaempferol-3-O-rutinoside were determined to be essential metabolites for trilobatin-mediated flavonoid biosynthesis in purple rice. The correlation network diagram between biochemical indexes and metabolites revealed that 1-O-sinapoyl-beta-D-glucose, coniferaldehyde, 6″-acetylapiin, and kaempferol-3-O-rutinoside were important metabolites. This study provides a scientific basis for improving the nutritional quality of rice grains and understanding the flavonoid biosynthesis pathway.