  The control in optical uniformity of single nanoparticles and tuning their
diversity in orthogonal dimensions, dot to dot, holds the key to unlock
nanoscience and applications. Here we report that the time-domain emissive
profile from single upconversion nanoparticle, including the rising, decay and
peak moment of the excited state population (T2 profile), can be arbitrarily
tuned by upconversion schemes, including interfacial energy migration,
concentration dependency, energy transfer, and isolation of surface quenchers.
This allows us to significantly increase the coding capacity at the nanoscale.
We further implement both time-resolved wide-field imaging and deep-learning
techniques to decode these fingerprints, showing high accuracies at high
throughput. These high-dimensional optical fingerprints provide a new horizon
for applications spanning from sub-diffraction-limit data storage, security
inks, to high-throughput single-molecule digital assays and super-resolution
imaging.
