Photon upconversion in Bi3Ti2O8F:Yb3+, Er3+ nanoplates for enhanced near-infrared light harvesting and their application in wastewater purification

Harvesting near-infrared (NIR) light to address the energy crisis and environmental pollution remains a challenge. In this study, full-spectrum-driven photocatalysts were realized through the design of Er 3+ /Yb 3+ co-doped Bi 3 Ti 2 O 8 F nanoplates. The Bi 3 Ti 2 O 8 F: Yb 3+ , Er 3+ nanoplates, when excited at 980 nm, demonstrated nearly single-band red upconversion (UC) emission. Furthermore, the corresponding UC emission mechanism was elucidated through the relationship between pump power and the UC emission spectrum. The experimental results and DFT calculation analysis revealed that the Er 3+ dopant ions form an impurity energy level, which broadens the light photoresponse range and promotes the separation of electron-hole (e − /h + ) pairs. Consequently, Bi 3 Ti 2 O 8 F:Yb 3+ , Er 3+ nanoplates exhibit 1.42 times better photocatalytic degradation of ciprofloxacin (CIP) than Bi 3 Ti 2 O 8 F under full-spectrum light irradiation and 4.54 times better than Bi 3 Ti 2 O 8 F: Er 3+ under NIR light irradiation. The trapping experiments and EPR analysis reveal that •O 2 – and h + are the main active species during the photocatalytic reaction process. Thus, this work demonstrates that efficient bismuth-based broadband photocatalysts can be developed through the simultaneous application of UC emission and doping engineering.