Eu3+-doped Bi7O5F11 microplates with simultaneous luminescence and improved photocatalysis

Donglei Wei,Hyo Jin Seo,Yanlin Huang

doi:10.1063/5.0012636

Abstract

Doping of rare-earth ions in a host is one of the important strategies to modify the microstructure and electrical and optical properties. This work demonstrated the significant improvement of luminescence and photocatalytic performances of Bi7O5F11 via Eu3+ doping. Bi7O5F11 has a typical Sillén–Aurivillius structure, which shows an intrinsic luminescence band peaked at 527 nm with a decay time of 0.041 µs. The intrinsic emission quenches in Bi7O5F11:Eu3+, which shows characteristic transitions from 5D0,1,2,3 levels to 7FJ (J = 0–4) ground states. An experimental red-LED lamp was successfully fabricated by encapsulating Bi7O5F11:Eu3+ with a transparent resin. Bi7O5F11 has poor photocatalytic ability, which just can happen under UV light irradiation. The fast decay time (0.041 µs) of Bi7O5F11 causes an efficient recombination of the light-induced charges, resulting in a lower photocatalytic effect. Bi7O5F11:Eu3+ shows the improved photocatalytic abilities compared with pure Bi7O5F11. 4f levels of Eu3+ provide a longer decay time (1 ms) for the excited states of Bi7O5F11, which prevents the recombination of the light-induced charges. Importantly, Eu3+ doping moves the required wavelength in photocatalytic reactions from UV light (pure Bi7O5F11) to visible wavelength in Bi7O5F11:Eu3+. Bi7O5F11:Eu3+ could be further investigated to develop a multifunctional bismuth material such as dielectric, photoelectric, and photochemical abilities.

Highlights

Bismuth compounds with a layered structure exhibit multifunctional performances such as luminescence, dielectric, and photochemical applications
An experimental red-LED lamp was fabricated by encapsulating Bi7O5F11:Eu3+ with a transparent resin
The photocatalytic effects on photodegradation of Rhodamine B (RhB) dye were improved in Bi7O5F11:Eu3+

Summary

INTRODUCTION

Bismuth compounds with a layered structure exhibit multifunctional performances such as luminescence, dielectric, and photochemical applications. This work reports Eu3+-activated Bi7F11O5 microplates with the red-luminescence and photocatalysis performances. Similar to BiOCl, Bi7F11O5 has a layered structure with great spontaneous polarization along [001], which can efficiently separate light-produced charges in the lattices. In order to prolong decay times of excited states, it is possible to dope Eu3+ in Bi7F11O5, which provides 4f levels with longer lifetime in μs or ms orders. In this way, the photocatalysis could be enhanced due to the prolonged lifetimes of excited states. Several Bi-compounds have reported the enhanced photocatalysis by Eu3+ doping such as BiOCl:Eu3+,20 Bi2O3:Eu3+,21 and BiVO4:Eu3+,22 etc. The luminescence, decay time, and improved photocatalysis of Bi7−7xEu7xO5F11 were studied and discussed

EXPERIMENTAL

Phase formation and morphology

Optical absorption and band structure

Intrinsic luminescence transition

Photochemical abilities

CONCLUSIONS