Bright Room-Temperature Phosphorescence from Mixed Mothballs Enabling Specific Identification of the Illegal Component

Ultralong organic room-temperature phosphorescence (RTP) with high brightness was rarely achieved to date despite their huge potential in various applications such as lighting, sensing, anti-counterfeiting and imaging. Herein, by exploiting π-π* nature of the lowest excited triplet state of naphthalene (NL, the traditional active ingredient for mothball) and intersystem crossingpromoting factors from 1,4-dichlorobenzene (DCB, a safer alternative to NL as mothball), we report a simple and novel guest/host system, namely NL/DCB, that could produce strong green RTP with quantum yield > 20% and lifetime > 0.76 s (afterglow duration > 10 s) at ambient conditions. The RTP performance with simultaneous high efficiency and ultralong lifetime is superior to that of most purely organic (metal-free) RTP materials reported so far. Control experiments with different hosts and first-principle theoretical calculations revealed that the robust RTP behavior in the unique NL/DCB system was mainly attributed to a combination of clusterexciton formation and external heavy atom effect. Meanwhile, the remarkable “turn-on” type RTP to naked eyes allows fast and specific detection of illegal NL mothball using DCB as a sensor, which is valuable in household as well as industrial applications.