Tunable Photoluminescence of Bismuth‐ and Trivalent‐Lanthanide‐Doped Monolayer Perovskite Oxide Nanosheets

Abstract

Multicolor photoluminescent Bi0.4Ln0.1Na0.5Ta2O72− nanosheets (Ln = Eu, Tb, Dy, Sm, La) are prepared by delaminating an Aurivillius‐phase layered perovskite, Bi2.4Ln0.1Na0.5Ta2O9. Both Bi3+ and Ln3+ (except La3+) successfully function as luminescent centers under UV‐light illumination (λex. = 240–340 nm), which result in a photoluminescence color that can be tuned by changing the lanthanide doping. The emission spectra are influenced by pH because the energy distribution to Ln3+ or to Bi3+ is different in acidic or in basic solutions. Freestanding Bi0.4Ln0.1Na0.5Ta2O72− nanosheet membranes are prepared by vacuum filtration, and the relationship between the photoluminescence and structural properties of the nanosheet membranes is investigated. The results indicate that differences in the electron orbitals involved in the photoluminescence of Bi3+ (6s2–6s6p) and Ln3+ (4fn–4fn) influence the responsiveness to changes in the environment surrounding those luminescent centers.