Amplifying Persistent Luminescence in Heavily Doped Nanopearls for Bioimaging and Solar-to-Chemical Synthesis.

Lanthanides are widely codoped in persistent luminescence phosphors (PLPs) to elevate defect concentration and enhance luminescence efficiency. However, the deleterious cross-relaxation between activators and lanthanides inevitably quenches persistent luminescence, particularly in heavily doped phosphors. Herein, we report a core-shell engineering strategy to minimize the unwanted cross-relaxation but retain the charge trapping capacity of heavily doped persistent luminescence phosphors by confining the activators and lanthanides in the core and shell, respectively. As a proof of concept, we prepared a series of codoped ZnGaO:Cr, Ln (CD-Ln, Ln = Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) and core-shell structured ZnGaO:Cr@ZnGaO:Ln (CS-Ln) nanoparticles. First-principles investigations suggested that lanthanide doping elevated the electron trap concentration for enhancing persistent luminescence, but energy transfer (ET) from Cr to Ln ions quenched the persistent luminescence. The spatial separation of Cr and Ln ions in the core-shell structured CS-Ln nanoparticles suppressed the ET from Cr to Ln. Due to the efficient suppression of deleterious ET, the optimal doping concentration of Ln in CS-Ln was elevated 50 times compared to CD-Ln. Moreover, the persistent luminescence intensity of CS-5%Ln was up to 60 times that of the original ZnGaO:Cr. The CS-5%Ln displayed significantly improved signal-to-noise ratios in bioimaging. Further, the CS-Ln was interfaced with the lycopene-producing bacteria for solar-to-chemical synthesis, and the lycopene productivity was increased by 190%. This work provides a reliable solution to fulfill the potential of lanthanides in enhancing persistent luminescence and can further promote the applications of persistent luminescence phosphors in biomedicine and solar-to-chemical synthesis.