Coordination Geometry-Dependent Multi-Band Emissionrnand Atypically Deep-Trap-Dominated NIR PersistentrnLuminescence from Chromium-Doped Aluminates

摘要

An abnormal trap distribution and coordination geometry-dependent multibandrnemission are discovered in chromium-doped aluminates. The multi-bandrnand broadband persistent luminescence from 650–1100 nm peaking at 688rnand 793 nm from Cr3+-doped SrAl12O19 is systematically studied via structuralrnand spectroscopic analysis. Solid state nuclear magnetic resonance allows thernvisualization of various coordination configurations in SrAl12O19, thus offeringrnthe possibility of tailoring the local geometry of the emission center to triggerrnthe control of the spectral parameter. Deep tissue ex vivo and in vivo imagingrnin mice both demonstrate that multi-band-emissive SrAl12O19:Cr3+ shows superior,rnhigh-quality near-infrared (NIR) bio-imaging in the biological transparencyrnwindow compared to single band-emissive (with emission only at 688 nm)rnSrAl2O4:Cr3+, although SrAl2O4:Cr3+ has a higher luminescent intensity andrnlonger duration at 688 nm. Moreover, by measuring the thermoluminescencernspectra the driving force of carrier release is discovered to be only from therndeep trap (the depth is > 1 eV), which is different from the generally acceptedrnshallow-dependent afterglow-emitting process. These findings pave the wayrnfor opening a vista of possible avenues for the enhancement of signal-to-noisernratio, the improvement of imaging quality, as well as the understanding of therntrapping and de-trapping process in long-persistent phosphors.