Spectroscopic Investigation On Upconversion Charging Of Cr³⁺-Dopded Infrared Persistent Phosphors

Infrared persistent phosphors refer to materials that can continuously emit infrared light after external excitation stops.Such materials have important application value in fields such as biomedical imaging,information storage,and anti-counterfeiting.Currently,reports on infrared persistent phosphors mainly focus on expanding material systems and optimizing emission performance,while research on excitation processes is relatively limited.Excitation of infrared persistent phosphors typically requires the use of high-energy light sources such as UV lamps,which significantly limits some special applications of persistent phosphors.Therefore,the development of a type of infrared persistent phosphors that can be excited by low-energy light sources such as visible light or infrared light has become meaningful.To address the above issues,this paper conducted research on producing infrared persistent luminescence under low-energy photon excitation in a Cr³⁺-sensitized infrared persistent phosphors system.By designing,verifying,and expanding the charging process of the infrared persistent phosphors,visible laser and high-power white light flashlight were used to charge the material.The specific experimental research contents are as follows:（1）The spectral information of the singly-doped materials was characterized,and the energy level structures of Cr³⁺,Yb³⁺,and Ni²⁺ions were comprehensively considered to propose an infrared persistent luminescence charging design.This design covers the upconversion excitation process sensitized by Cr³⁺and the persistent energy transfer process from Cr³⁺to Yb³⁺/Ni²⁺.（2）Based on the infrared persistent luminescence charging design,LaMgGa₁₁O₁₉:Cr³⁺,Yb³⁺,Ni²⁺was prepared.The material produced infrared persistent luminescence emission from Cr³⁺,Yb³⁺,and Ni²⁺ions under 593 nm laser excitation,validating the feasibility of this design.By studying the relationship between luminescence intensity and white light flashlight output power,it was determined that the luminescent system undergoes upconversion charging by absorbing two photons continuously.Furthermore,the upconversion charging excitation mechanism was verified through thermoluminescence experiments and persistent luminescence decay tests,and the results showed that both excited-state absorption upconversion and energy-transfer upconversion contribute to the upconversion charging excitation process.（3）In order to further enrich the infrared persistent phosphors system,infrared emitting centers were extended to lanthanide ions,and various infrared persistent phosphors LaMgGa₁₁O₁₉:Cr³⁺,Yb³⁺,Nd³⁺/Ho³⁺/Er³⁺were prepared.Under high-power white light flashlight excitation,materials doped with different activation ions produced characteristic infrared persistent luminescence emissions at 1065 nm(Nd³⁺),1200 nm(Ho³⁺),and1550 nm(Er³⁺),respectively,indicating that infrared persistent luminescence emission with tunable spectral range was achieved through upconversion charging.