The second near-infrared fluorescence concealed imaging for identifying smuggled baggage

Smuggling methods are renovating with more diversified, complicated means, thereby developing concealed and non-sensitive luggage identification technology is of great significance. Herein, for the first time, the second near-infrared (NIR-II, 1000–2500 nm) concealed imaging for identifying smuggled baggage based on organic small molecule luminescent material was studied. A small molecule luminescent material (Y6) with the excitation in invisible near-infrared (NIR) light was used to generate fluorescence-emission in NIR-II region. The traceless Y6 sprayed on the surface of criminal luggage does not emit light under visible light irradiation, but shows hidden NIR-II signs under NIR excitation that can prevent the suspects to find abnormality and lose their luggage. The Y6 organic luminescent material has invisibility, low toxicity, long-term fluorescence stability and high transparency. This NIR-II fluorescence imaging technology can be used as a new type of concealed baggage marking, which is of great significance to help the customs combat smuggling crimes.