Photon avalanche in nanoparticles opens way to bioimaging

Abstract

• Photon avalanching is a special type of upconversion, where multiple photons combine to create a single higher energy photon. • Photon avalanching is reported in thulium (Tm) doped core-shell nanoparticles. • Nanoscale confinement of photons in nanoparticle core enhances upconversion and leads to photon avalanching. • The phenomenon enables super-resolution scanning confocal microscopy and could be useful for sensing. An illustration of the chain-reaction process that underlies the photon avalanching mechanism Columbia Engineering researchers have realized in their nanoparticles. In this process, the absorption of a single low-energy photon sets off a chain reaction of energy transfers and further absorption events that result in many highly excited ions within the nanoparticle, which then release their energy in the intense emission of many higher-energy photons. Credit: Mikolaj Lukaszewicz, Polish Academy of Sciences.