Vanadium‐Sensitized Photon Upconversion of Lanthanide Ions (Er, Tm, Ho, Eu, Nd) in Yb3Al5O12 for In Vivo Imaging

Abstract Photon upconversion of oxides nanomaterials have attracted broad attentions on account of their high stability and cost‐effective fabrication process. However, the relative low emission intensity caused by nonradiative decay severely limits their applications. Here, a new strategy to enhance upconversion emission of oxides through vanadium sensitization is reported, in which efficient emissions can be achieved via Yb–VO 4 3− dimer‐mediated energy migration for a wide range of lanthanide activators (including Er, Tm, Ho, Eu, and Nd) in Yb 3 Al 5 O 12 system. Interestingly, the resulting oxide nanocrystals demonstrate remarkable upconversion enhancement compared with their vanadium‐undoped counterparts, for example, an enhancement factor of 580 is reached for green emission of Er. More importantly, efficient upconversion luminescence can be realized for the activators (such as Eu and Nd ions) without long‐lived intermediary energy states. Considering the demonstration of in vivo bioimaging by using these nanocrystals after surface modification, it is anticipated that these results can bring new opportunities to oxide upconversion nanomaterials in bioassay, therapy, sensing, and other aspects.