Design and application of ratiometric room temperature phosphorescent probes based on triplet-singlet Fӧrster resonance energy transfer mechanism between silica-coated phosphorescent carbon dots and rhodamine 6G

In this paper, we successfully designed and constructed a ratiometric room temperature phosphorescent probe (CDs@SiO 2 –Rh6G) that can realize highly sensitive detection of nitrite in urine under the interference of ascorbic acid (AA) based on the triplet-to-singlet Fӧrster resonance energy transfer mechanism between silica-coated phosphorescent carbon dots and rhodamine 6G. This unique energy transfer mechanism is discussed in detail, and the interference of various factors on nitrite detection is systematically investigated. With the successful masking of AA by 4-hydroxy-2,2,6,6-tetramethylpiperidinooxy (4-OH-TEMPO), CDs@SiO 2 –Rh6G could accurately detect NO 2 − with a limit of detection (LOD) as low as 0.242 μmol/L, which is much lower than that of the commercially available urinary nitrite test paper. The probe was tested on real urine samples—human, dog, and cat urine—and the results were highly consistent with those obtained by ion chromatography, with spike recoveries ranging from 96.5 % to 105.3 %. Since the green and yellow luminescence of the probe is visible to the naked eye, a visual analysis method based on the RGB values of smartphones was developed. This study presents a new strategy for constructing ratiometric room temperature phosphorescent probes based on a unique TS-FRET mechanism. Meanwhile, this research not only overcomes the quantitative limitations of current test strip detection methods but also lays the foundation for developing more sensitive and accurate clinical diagnostic tools for urinary tract infections.