La0.90Dy0.05Nb2O7 nanosheet phosphor and its multilayer films with enhanced host excitation-mediated photoluminescence

Abstract

La0.90Dy0.05Nb2O7 nanosheets were achieved by exfoliating a layered compound HLa0.90Dy0.05Nb2O7. Multilayer films composed of the exfoliated nanosheets were prepared by a layer-by-layer deposition technology, which were subsequently heat-treated at 450°C and exposed under ultraviolet light to obtain the polymer-free nanosheet films, respectively. The resulting La0.90Dy0.05Nb2O7 nanosheet suspension and its films exhibit intense emission by the host excitation and negligibly low emission by the direct Dy3+ excitation, whereas the photoluminescence emissions of the bulk precursors are largely dominated by the direct Dy3+ excitation rather than the host excitation. The comparison between the excitation spectra and the bandgap absorption spectra indicates that the enhanced host excitation-mediated photoluminescence of La0.90Dy0.05Nb2O7 nanosheet results from the efficient energy transfer from the O–Dy charge-transfer transition to Dy3+ within the nanosheet, and that the intensive emission of the multilayer films is attributed to the energy transfer from both of the O–Dy charge-transfer transition and the O–Nb network to Dy3+. Dy3+ in the La0.90Dy0.05Nb2O7 nanosheet and the nanosheet-based films gives two emission peaks at around 480 and 576nm and the blue emission is prominent in the film form.