Simultaneously controlling phase, morphology and up-conversion luminescence via lanthanide doping in Bi2O3: Yb3+/Tm3+ nanoparticles

Bi2O3: Yb3+/Tm3+ nanoparticles with varied phase structures and morphologies were synthesized via the coprecipitation method assisted with a subsequent high-temperature calcination process. The influences of experimental parameters including dosage of urea, dopant concentration, reaction temperature and time on the crystal phase structures and morphologies of the as-prepared nanoparticles were investigated. Results revealed that the morphology, the crystal phase and the up-conversion emission of Bi2O3: Yb3+/Tm3+ could be simultaneously controlled by varying Yb3+ doping concentration. With increasing Yb3+ doping concentration (0-40%), the dramatic morphological evolution (nano-sheet to nano-flower to nano-sphere) and phase transition (monoclinic to tetragonal to cubic phase) were observed. Under the excitation of CW and pulse 980 nm lasers, Bi2O3: Yb3+/Tm3+ samples exhibited red (693 nm) and NIR (795 nm) double-band up-conversion emissions, where the increase of Yb3+ concentration leaded to the decreased emission intensity ratio of NIR to red (I-795/I-693) and the suppressed pulse-width-dependent up-conversion output.