Tailoring of the trap distribution and crystal field in Cr3+-doped non-gallate phosphors with near-infrared long-persistence phosphorescence

Yang Li,Ruchun Chen,Mindaugas Gecevicius,Kaniyarakkal Sharafudeen,Haihui Wang,Xixi Qin,Yiyang Li,Yiling Wu,Jianrong Qiu,Shifeng Zhou,Guoping Dong

doi:10.1038/am.2015.38

Abstract

We present a series of efficient near-infrared (NIR) Cr3+-doped non-gallate long-persistence phosphors (Zn2SnO4: Cr and Zn(2-x)Al2xSn(1-x)O4: Cr) and highlight their special optical characteristics of broad emission band (650-1200 nm, peaking at 800 nm) and long afterglow duration (>35h). In the context of materials selection, these systems successfully avoid the existing ubiquitous reliance on gallates as hosts in Cr3+-doped phosphorescent phosphors. Zn2SnO4 is employed as a host to take advantage of its characteristic inverse spinel crystal structure, easy substitution into Zn2+ and Sn4+ sites by Cr3+ in distorted octahedral coordination and non-equivalent substitution. In this work, Al dopant was introduced both to precisely tailor the local crystal field around the activator center, Cr3+, and to redeploy trap distribution in the system. Indeed, such redeployment permits band gap adjustment and the dynamic variation of the annihilation and the formation of defects. The results demonstrate that the method employed here can be an effective way to fabricate multi-wavelength, low-cost, NIR phosphorescent phosphors with many potential multifunctional bio-imaging applications.

Highlights

Long-phosphorescence phosphors (LPPs), called long-lasting, long-persistence or long-duration phosphors, have been widely applied in safety signage, dial displays, security ink, night-vision surveillance and in vivo bio-imaging because of their unique energy storage ability.[1,2] In particular, they possess many advantages over other biomarkers for potential use in in vivo imaging applications
(4) The infrared phosphorescence peak positions can be precisely tuned from 800 to 720 nm by rearranging the ligands surrounding Cr3+ and by altering the electronic configuration of the central active element through the addition of Al. (5) It is revealed that the deepening of trap site levels caused by the increasing energy gap between the conduction band (CB) level and the trap site level, along with the variation in trap concentration and type, which is determined by the dynamic variation of defect annihilation and creation, are both related to the phosphorescence duration of Zn(2-x)Al2xSn(1-x)O4 phosphors, as demonstrated by the thermoluminescence (TL) spectra and electron spin resonance (ESR) measurements
Design strategy of Zn2SnO4 When designing LPPs with desirable photoemission wavelengths for practical applications, prioritized consideration must be given to identifying a suitable emitter because the emitters are centers that are capable of emitting radiation after being excited; they determine emission wavelength

Summary

Introduction

Long-phosphorescence phosphors (LPPs), called long-lasting, long-persistence or long-duration phosphors, have been widely applied in safety signage, dial displays, security ink, night-vision surveillance and in vivo bio-imaging because of their unique energy storage ability.[1,2] In particular, they possess many advantages over other biomarkers for potential use in in vivo imaging applications. Tailoring of the trap distribution and crystal field in Cr3+-doped non-gallate phosphors with near-infrared long-persistence phosphorescence

Results

Conclusion