Tunable luminescence from two dimensional BCNO nanophosphor for high-contrast cellular imaging

Rare-earth free and biocompatible two dimensional carbon based boron oxynitride (2D BCNO) nanophosphors were synthesized using facile auto-combustion of inexpensive compounds such as urea, boric acid and polyethylene glycol at ambient atmosphere and relatively low temperatures. The surface morphology and microstructure images indicate that the nanophosphor has 2D layered structures and analogous mixed hexagonal lattices of boron nitride (BN) and graphene (C). The nanophosphor exhibits a single, distinct and broad photoluminescence emission and this emission colour can be easily tuned from violet to deep red by varying the amount of boron/carbon content. The time-resolved and photoluminescence spectroscopic results indicate that B-O act as luminescence centers, which are responsible for the tunable luminescent properties while carbon impurities induce energy levels in the band gap of 2D BCNO nanophosphors. These tunable and biocompatible luminescent nanophosphors are used for in vitro high-contrast cellular imaging of HeLa cells derived from human cervical cancer cells as well as in vivo imaging in C57BL/6J mice. Hence, these novel multi-colour emitting nanophosphors provide a paradigm shift in rare-earth free biocompatible nanoprobes for next generation high-contrast in vitro and in vivo imaging applications.