Luminescent materials with engineered optical property have been developed for multiplexed labeling detection, where encoding capacity plays a pivotal role in the efficiency. However, multi-dimensional optical identities are usually not independent which essentially hinders the practical encoding numbers to access theoretical capacity. In this work, we carefully studied the sensitizer gradient doping structure in near-infrared (NIR) excitable upconversion nanoparticles (UCNPs) and managed to achieve independent emission intensity and lifetime tuning. With the orthogonal tunability, it breaks the constraint of intensity (k) and lifetime (n) correlation and expands the practical encoding number to theoretical value as (k+1)n-1 in binary encoding. This method can also be combined with previous lifetime engineering to realize high level multiplexing.

   Fig 1. （a）Illustration showing the expanding of binary encoding capacity by orthogonal lifetime and intensity.（b）Scheme of sensitizer gradient doping strategy.（c）Illustration of independent tuning of luminescence lifetime and intensity. (d）Example images of full-color high level encoding encryption.

   https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202015273