Synthesis of Carbon Quantum Dots with Special Reference to Biomass as a Source - A Review

Quantum dots (QDs) have received much attention due to their extraordinary optical application in medical diagnostics, optoelectronics and in energy storage devices. The most conventional QDs are based on semiconductors that comprise heavy metals whose applications are limited due to toxicity and potential environmental hazard. Of late, researchers are focusing on carbon-based quantum dots, which have recently emerged as a new family of zero-dimensional nanostructured materials. They are spherical in shape with a size below 10 nm and exhibit excitation-wavelength-dependent photoluminescence (PL). Carbon quantum dots (CQDs) have unique optical, photoluminescence and electrochemical properties. They are environment-friendly with low toxicity as compared to toxic heavy metal quantum dots. Generally, CQDs are derived from chemical precursor materials, but recently researchers have focused their attention on the production of CQDs from waste biomass materials due to the economic and environmental exigency. In this review, recent advances in the synthesis of CQDs from waste biomass materials, functionalization and modulation of CQDs and their potential application of biosensing are focused. This review also brings out some challenges and future perspectives for developing smart biosensing gadgets based on CQDs.