Facile cost-effective green synthesis of carbon dots: selective detection of biologically relevant metal ions and synergetic efficiency for treatment of cancer.

A facile cost-effective green synthesis approach has been used to synthesize carbon-dot (CDs) from the Kernel part of the Azadirachta Indica seeds and investigated their fluorescent and metal ions sensing capability and also used for the delivery of drugs. Metallic ions such as Ca2+, K+, Na+, Fe3+, and Zn2+ which are biologically important for many reactions and are selectively detected through the novel CDs. The resultant dot size of CDs (~ 4 nm) is useful to eliminate the 'Achilles heel' problems, which is associated with the Zn2+ in the body and its detection is a very challenging task. It is found that the sensitivity of CDs for the detection of Zn2+ can be regulated by using different solvents. These CDs can also be used as a sensing probe for the selective detection of Fe3+ at a very low concentration of solution (~ 5 µM). The synthesis method of CDs reported here is cost-effective, very fast and it is highly selective towards Fe3+ and Zn2+. Due to the fast response capability of these CDs, logic gate operation is achieved and it provides a new understanding to construct potential next-generation molecular devices for the detection of different biomolecules with high selectivity. Additionally, these CDs are biocompatible against normal healthy cells, capable of loading small biomolecules and drugs due to their porous nature, and exhibited potential impact for breast cancer therapy. It is observed that a significant synergic therapeutic effect of CDs loaded with DOX against breast cancer cells is very promising. Thus, the CDs reported herein in this work have been synthesized through a green synthesis approach and can be used as a molecular probe for the detection of metal ions as well as for drug delivery applications.