Grafting Carbon Dots on Persistent Luminescence Phosphors to Generate Remarkably Improved NIR Afterglow for Microenvironment Fluorescence Detection

Abstract Recently, combining long afterglow materials with organic fluorescent dyes, particularly carbon dots (CDs) to produce heterojunction and improve its luminescence and persistence properties became an important research direction. However, the precise role of these internal defects in the energy transfer process of CD@inorganic matrix composite fluorescent materials has not been thoroughly discussed. Establishing matching trap level to promote the energy transfer between the trap level and CDs level not only helps to enhance the afterglow performance, but also can explain the heterogeneous structure interaction between organic–inorganic fluorescent materials. Herein, ZLAGC@CDs luminescent composite is successfully synthesized via coating CDs on Zn_1‐x(Li/Al)_xGa_2xO₄:0.005Cr³⁺ (ZLAGC, x = 0–1), which exhibits a unique double emission at ≈430 nm (the defect luminescence of CDs) and 718 nm (the ²E→⁴A₂ transition of Cr³⁺). After coating, the energy transfer from the defect level of CDs to the excited state of Cr³⁺ enhanced the NIR emission. The electron transfer between the defect level of CDs and the split deeper trap level of ZLAGC also improved the visible and near‐infrared (NIR) afterglow. The fluorescence and afterglow signals of ZLAGC@CDs are highly sensitive to solution pH under acidic conditions, indicating that the prepared fluorescent composite has potential application in acid microenvironment fluorescence detection.