Near‐Infrared I/II Nanophosphors with Cr³⁺/Ni²⁺ Energy Transfer for Bioimaging

Abstract In the biomedical field, the use of fluorescence imaging in the second near‐infrared (NIR‐II) region is growing rapidly because it imparts the advantages of reduced autofluorescence and low photon scattering. The advantage of reduced scattering is that it increases penetration depth in vivo and improves imaging clarity. Herein, this work uses mesoporous silica, a biocompatible template that can be easily modified, functionalized, and loaded with drugs for use in several bioapplications. The ZnGa₂O₄ spinel oxide system is integrated into mesoporous silica and different concentrations of Cr³⁺ and Ni²⁺ are loaded in octahedral sites to obtain the highest emission intensity in the NIR‐II region at 1285 nm via energy transfer from Cr³⁺ to Ni²⁺. Given that only a few nanophosphor systems with emission in the NIR‐II region are available, this work attempts to establish emission in the NIR‐II and NIR‐I regions to obtain images in vivo with an increased penetration depth to 5 mm and improved clarity for bioimaging purposes. This system will open the door for biomedical research on other NIR‐II nanophosphors.