Dual-emissive Bi3+, Cr3+ Co-doped K2LiGaF6 phosphors: Achieving white and near-infrared light for innovative applications in food detection and bio-imaging

Multifunctional luminescent materials emiting dual white and near-infrared (NIR) radiation have broad applications in various fields, including illumination, food detection and bio-imaging. Herein, an ultra-wide spectrum ranging from 330 to 1000 nm is achieved simply by co-doping Bi 3+ and Cr 3+ into the double perovskite K 2 LiGaF 6 , enabling simultaneous emission of white and NIR light. The emission bands peaking at 475 and 750 nm correspond to the radiative transitions of Bi 3+ and Cr 3+ , respectively. Systematically studies reveal that the NIR emission of Cr 3+ originates from efficient energy transfer from Bi 3+ , with energy transfer efficiency exceeding 80 %. The energy transfer mechanism is thoroughly explained. Moreover, the red partial emission of Cr 3+ in turn compensates the missing red component in the bluish emission of Bi 3+ , contributing to the final white emission. Notably, Bi 3+ ions occupy double lattice sites of Ga 3+ and Li + , which exhibit distinct luminescence properties. The luminescence behaviors of double Bi 3+ and Cr 3+ centers at various temperatures are systematically analyzed. Finally, the combination of the as-prepared dual-emissive K 2 LiGaF 6 :Bi 3+ ,Cr 3+ phosphor and a UV chip demonstrates potential applications in illumination, food detection and bio-imaging. This work provides new perspectives for the design of multifunctional luminescent materials and their deployment in diverse application scenarios.