Persistent luminescence (PersL) nanoparticles emit a signal that lasts long after the excitation has ended, enabling highly sensitive bioimaging without background noise. When using UV light as excitation source before the injection, a strong PersL signal can be detected in vivo before disappearing within a few hours. For long-term imaging, we have shown in the past that visible LED can be used to re-excite ZnGa1.995Cr0.005O4 (ZGO:Cr 3+ ) nanoparticles in vivo, producing a signal intensity that is, however, much lower compared to the signal obtained after the UV preexcitation method. This lower signal intensity of the nanoprobe when using visible LED may prevent its detection in some cases. Herein, we report an improvement in the excitation efficiency of visible LED using Zn1.33Ga1.335Cr0.005Sn0.33O4 (ZGSO:Cr 3+ ) PersL nanoparticles. We fully compared ZGSO:Cr 3+ and original ZGO:Cr in term of structure, optical properties and bio-imaging potential. The co-doping with tin strongly enhances the persistent luminescence, even at the nanoscale. In vivo imaging results showed that ZGSO:Cr 3+ exhibits an approximately 3-fold signal enhancement compared to ZGO:Cr 3+ using UV pre-excitation. Even more interestingly, when using LED excitation, the signal intensity of ZGSO: Cr 3+ is more than 10-fold higher than the one of ZGO:Cr 3+ , making ZGSO nanoparticles much easier to detect. ZGSO:Cr nanoparticles can be surface-modified with PEG to get nanoprobes with a much longer residence time in blood. This unique comparison between both compositions makes ZGSO:Cr 3+ a more effective imaging diagnostic probe than the original ZGO:Cr 3+ nanoparticles, opening up new applications for in vivo diagnostics.