Green synthesis of carbon quantum dots and applications: An insight

Carbon quantum dots (CQDs) are tiny(less than 10 nanometers size) carbon-based nanoparticles. Their exceptional chemical stability, photo luminescent properties and biocompatibility have opened up fascinating and diverse areas of applications in fields ranging from optoelectronics and photo catalysis to bio imaging and drug delivery. Synthesizing CQDs through varied techniques provides an area of intensive research, aiming to achieve well- controlled precision over their dimensions, structure, and optical properties. The bottom-up approaches as well as the top- down synthesis strategies are the commonly used methods. However these methods not being environment friendly, there has been shift towards greener methods of synthesis. The synthesis of CQDs from natural precursors is an innovative and sustainable approach in nanotechnology. Natural precursors offer a rich source of carbon making them inherently biocompatible due to which they are ideal for synthesis of CQDs with minimal environmental impact with enhanced potential for biomedical and environmental applications due to low or minimal toxicity of the starting materials. In this article we discuss the different methods of synthesis of CQDs and describe the advantages of synthesis from natural precursors as well as their varied applications. • Carbon quantum dots (CQDs) show fascinating and diverse areas of applications. • Different synthetic approaches i.e. top down and bottom up approaches are covered. • The comprehensive review covers green synthesis of CQDs. • It is a valuable resource for environmental and biomedical applications of CQDs. • Challenges and probable solutions for scaling up green synthesis have been presented.