Nano Lett. 14, 2623–2627 (2014)

Fluorescence lifetime microscopy is a popular tool for biomedical imaging. Now, scientists in Germany have taken the approach and in a 'tour de force' experiment engineered it to operate on the nanoscale so that it can determine the local density of photonic states surrounding a probe. Andreas Schell and co-workers from Humboldt University of Berlin in Germany attached a single-quantum emitter (a 30 nm nanodiamond with a nitrogen–vacancy defect) to the tip of an atomic force microscope and scanned it across a silver nanowire. By measuring changes in the emitter's spontaneous emission lifetime as a function of position, they were able to glean information about the local density of states with a nanoscale resolution. The researchers say that their 'scanning single-quantum emitter fluorescence lifetime imaging' will prove useful not only for understanding fundamental quantum optical processes but also for characterizing novel nanophotonic and plasmonic devices.