Graphene quantum dots: synthesis, characterization, and application in wastewater treatment: a review

Abstract

Graphene quantum dots (GQDs) are nanoscale particles of graphene, typically having a diameter of less than 20 nm. The unique attributes of GQDs include low toxicity, good solubility, tunable photoluminescence (PL), biocompatibility, and photo-induced electron transfer. GQDs can be produced using hydrothermal reactions, laser ablation, microwave radiation, and electrochemical oxidation. These procedures for producing GQDs involve various chemical reactions, including carbonization, oxidation, pyrolysis, and polymerization. Due to their small particle sizes, GQDs possess strong tunable fluorescent properties and exhibit high photo-luminescence emissions. GQDs have been acknowledged as appropriate for various applications, such as eliminating pollutants and organic dyes through catalysis, absorbing heavy metals, and purifying microbial contamination through filtration. However, challenges encountered during the development of GQDs for environmental applications include generating high-quality QDs and devising large-scale synthetic procedures that ensure reproducible size distribution. A need exists for theoretical and practical research on the development of novel methods that allow high yields and easy purification of GQDs to be achieved. In this article, the characteristics of GQDs in terms of their chemical and physical attributes are analyzed. The raw materials and techniques employed in the manufacturing process of GQDs are also discussed, along with their stability. Additionally, the potential applications of GQDs in treating wastewater are explored.