Plant leaf-derived fluorescent carbon dots for sensing, patterning and coding

We report a simple, low-cost and green route for fabrication of fluorescent carbon dots (CDs), and demonstrate their applications in sensing, patterning, and coding. Pyrolysis of various plant leaves yielded bright blue-emitting CDs, providing a one-step way for large-scale production of CDs without surface passivation treatment or the use of toxic/expensive solvents and starting materials. Also, further improvement in the fluorescence intensity of CDs was achieved after treatment using plasma and microwave-assisted techniques. The obtained CDs were applied as a fluorescent sensing platform for sensitive and selective detection of Fe³⁺ ions, and as fluorescent inks for printing luminescent patterns useful in anti-counterfeit and optoelectronic applications. Moreover, uniform fluorescent microbeads of polymer-encapsulated CDs, CD/QD nanocomposites, and CD/organic fluorescent dye nanocomposites were prepared via a microfluidic process, which may expand the potential applications of CDs in coding, bioimaging, and drug delivery.