Issue Date: May 29, 2017
A new record for delayed fluorescence
A new material composed of carbon dots embedded in zeolites, with the much-sought-after property of delayed fluorescence, fluoresces longer at ambient temperature and pressure than any such material, scientists report (Sci. Adv. 2017, DOI: 10.1126/sciadv.1603171). So-called thermally activated delayed fluorescence (TADF) materials have gained popularity in recent years, as their high quantum efficiency makes them useful for numerous applications, such as sensors and flat-panel displays. Carbon dots, which are less than 10 nm in size, are popular candidates for TADF materials because they are nontoxic, biocompatible, and stable. Light excites electrons in the carbon dots to triplet states, with delayed fluorescence occurring as electrons cross over to the singlet state. However, outside influences such as atmospheric oxygen can absorb the electrons’ energy before they have a chance to emit photons. So Jiyang Li, Jihong Yu, Jiancong Liu, and their colleagues at Jilin University protected the carbon dots by embedding them in a zeolite matrix. The result was a material with a fluorescence lifetime of up to 350 milliseconds, which far exceeds the several-millisecond maximum lifetimes of other materials.
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