Avalanching Upconverting Nanoparticles for Super Resolution Imaging*

Photon avalanche (PA) is a photon energy upconversion excitation mechanism. It enables nonlinear dependence on excitation power, which is a key factor for various applications in photon science. One exciting application is that it suggests a possible approach to super-resolution imaging with a simple confocal microscope system. Here, we introduce avalanching upconverting nanoparticles (AUCNPs), NaYF4 nanocrystals doped with Thulium ions. The presence of PA was verified by time-resolved photoluminescence measurement. Upon the exitation of 1064nm laser, the resolution of 2-dimensional photoluminescence map was resolved to 90nm as a result of high nonlinearity, more than 4 times of diffraction-limited imaging resolution. AUCNPs are thus a promising new method for super resolution bioimaging.