Room-temperature single-molecule fluorescence imaging for terrylene in biphenyl single crystals

The technique of room-temperature wide-field epifluorescence microscopy has been applied to visualize, on a single-molecule level, impurity-related dynamical processes in sublimation-grown flakes of biphenyl single crystals doped with terrylene molecules. For dilute samples, spatially resolved fluorescence of individual terrylene molecules can be observed using a standard microscope equipped with an EMCCD camera. The 532 nm excitation laser light induces irreversible photobleaching of single-molecule emitters; this process is inhibited in a nitrogen-enriched atmosphere, thus confirming the role of photochemical reactions between terrylene and oxygen. Although most of terrylene impurity molecules appear to stay fixed in the host crystal, some of them can be observed to move around over distances of tens of micrometers, probably diffusing along the defects of the crystalline structure.