Durable room-temperature phosphorescence of nitrogen-doped carbon dots-silica composites for Fe3+ detection and anti-counterfeiting

Developing durable room temperature phosphorescent carbon dot-based materials with high stability and easy preparation has been a great challenge. Here, through a one-step hydrolysis-assisted carbonization treatment, nitrogen-doped carbon dots encapsulated in silica (N-CDs@silica) are obtained, with outstanding stability and durable room temperature phosphorescence (RTP) lifetime (1.81 s, nearly 9 s to naked eye). Further investigations reveal that C--O bonds from N-CDs are the main luminescence centers. The formation of Si-O-C bonds covalently linking N-CDs and silica matrice together within silica sphere, as well as the efficient crosslinking effect within N-CDs, are responsible for RTP emission. Based on the unique optical properties of NCDs@silica, we have developed the RTP strip probe for selective Fe3+ detection. In addition, we explored NCDs@silica as security ink for advanced anti-counterfeiting. This work not only provides a strategy to synergistically optimizes the structural and luminescent properties of N-CDs@silica in a simple and efficient manner, but more importantly opens a new perspective for developing simple RTP strip probes for sensor applications.