Multifunctional Near-Infrared (NIR) Phosphors with NIR I and NIR II Luminescence for Biological Detection

Multifunctional broadband near-infrared (NIR) Mg14Ge5O24: Mn4+, Cr, Yb3+ (MGO: Mn4+, Cr, Yb3+) phosphors were obtained by a solid-state method. An NIR emission band with a full width at half maximum of 320 nm was realized in the MGO: Cr, Yb3+ phosphor. The introduction of Yb3+ in MGO: Cr made the emission spectrum wider and improved the luminescence properties and thermal stability by energy transfer. The energy transfer mechanism was analyzed in detail. The improvement of NIR II luminescence was explored. A series of MGO: Mn4+, Cr samples were synthesized. The introduction of Mn4+ ions unexpectedly affects the crystal field of Cr4+. The decrease in the Stokes shift results in a decrease in nonradiative transition, so the probability of an effective electronic transition increases, and the emission intensity of Cr4+ has been improved to a certain extent. Finally, Mn4+, Cr, and Yb3+ tri-doped multifunctional near-infrared phosphors were obtained, and the applications of NIR I in the detection of hemoglobin concentration and detection of different biological tissues in NIR II proved that MGO: Mn4+, Cr, Yb3+ phosphors have great potential in the biological application field of NIR light-emitting diodes.