Synthesis of functionalized triple-doped zinc gallogermanate nanoparticles with superlong near-infrared persistent luminescence for long-term orally administrated bioimaging

Near-infrared persistent luminescence nanoparticles (NIR-PLNPs) have great potential for bioimaging because of no need for in situ excitation, negligible autofluorescence background and deep tissue penetration in optical detection. However, it is challenging to synthesize monodispersed nanosize NIR-PLNPs along with high quantum yield and long afterglow. Here, we show a surfactant-aided hydrothermal method in combination with a short time calcination and a post hydrothermal procedure for the synthesis of ultra-bright monodispersed triple-doped zinc gallogermanate nanostructures with super-long near-infrared persistent luminescence (ZGGO:Cr3+,Yb3+,Er3+). The ZGGO: Cr3+, Yb3+, Er3+ exhibits NIR emission with high quantum yield (9.86%), superlong afterglow time (>20 days), monodispersed nanosize, red light renewability, excellent biocompatibility, and low toxicity. The effective red LED light activation of the persistent luminescence of ZGGO: Cr3+, Yb3+, Er3+ with no need for UV pre-irradiation permits the material for long-term in vivo bioimaging application. We also show for the first time the better targeting performance of the oral administration of folate acid functionalized ZGGO: Cr3+, Yb3+, Er3+ for tumor-targeting bioimaging than conventional intravenous injection. We believe that the ZGGO: Cr3+, Yb3+, Er3+ will open new perspectives for orally administrated optical imaging and for diagnosis applications.