Mn²⁺-Doped CaF₂ Time-Resolved Luminescent Nanoprobes And Their Biological Applications

Time-resolved(TR)photoluminescence(PL)technique has shown great promise in ultrasensitive biodetection and high-resolution bioimaging,owing to its ability to eliminate the interference of short-lived background noise from biological autofluorescence and scattered light.Hitherto,almost all the TRPL bioprobes are based on lanthanide chelates or lanthanide-doped nanoparticles(NPs),by taking advantage of the long-lived PL(?s-ms range)of lanthanide ions originating from the parity-forbidden intra-4fNelectronic transition.Herein,we report TRPL biosensing by taking advantage of the d?d transition of transition metal(TM)Mn2+ ion.We demonstrate that the FRET signal can be distinguished from that of radiative reabsorption process through measuring the PL lifetime of Mn2+,thus establishing a reliable method for Mn2+ in homogeneous TR-FRET biodetection.We also demonstrate the biotin receptor-targeted cancer cell imaging by utilizing biotinylated CaF2:Ce,Mn nanoprobes.Furthermore,we show in a proof-of-concept experiment the application of the long-lived PL of Mn2+ for TRPL bioimaging through the burst shot with a cell phone.These findings provide a general approach for exploiting the long-lived PL of TM ions for TRPL biosensing,thereby opening up a new avenue for the exploration of novel and versatile applications of TM ions.