Near-infrared emission carbon dots for bio-imaging applications

It is very difficult to prepare red/near-infrared emission carbon dots (CDs) for bio-imaging applications which are needed because of their deep tissue penetration, minimal auto-fluorescence, and low emission light damage to bio-tissues. Near-infrared emitting CDs (NIR-CDs) were synthesized from sulfonated tetraphenylporphyrin using a solvothermal method. They have excitation-independent properties with a maximum emission at 692 nm. Studies showed that this unique near-infrared emission mainly originated from the aggregated molecular states of the CDs. The NIR-CDs showed good water solubility, exceptional biocompatibility, low toxicity, and superior cellular labelling ability. This work could significantly advance the structural design and preparation of NIR-CDs and corresponding bio-imaging applications.