Recent advances in graphene quantum dots: Chemistry of synthesis, surface modifications, and improved properties for biomedical applications

Graphene quantum dots (GQDs) emerged as a focal point of researchers owing to their expceptional properties such as quantum confinement, pronounced edge effect, inherent biocompatibility, minimal toxicity, tunable photoluminescence, and excellent dispersibility. These properties make them highly suitable for a range of applications including promising biomedical applications, allowing for the exploration of biological processes at the cellular level. In this review, the recent advances in the synthesis of GQDs encompassing both top-down and bottom-up approaches have been discussed such as hydrothermal, microwave, electrochemical, ultrasonic, pyrolysis etc. along with green synthesis method with emphasis on how to improve their properties for biomedical applications. Various synthesis parameters and their optimizations of good biocompatible GQDs along with various surface modifications and other physio-chemical properties have been discussed in detail with their biomedical applications. Thereafter, review focuses on recent advances in biomedical applications using GQDs such as biosensing, bioimaging, drug delivery, tissue engineering, photothermal/photodynamic therapy etc. with emphasis on mechanism of action of GQDs. Eventually, the review delves into the multifaceted challenges associated with the integration of GQDs into biomedical applications. • Discusses the unique characteristics of GQDs, including quantum confinement, edge effects, biocompatibility, low toxicity, tunable photoluminescence • Advancements in GQD synthesis, including top-down and bottom-up methods such as hydrothermal, microwave, electrochemical, ultrasonic, pyrolysis, and green synthesis • Explores various functionalization strategies and physicochemical modifications • Role of GQDs in biosensing, bioimaging, drug delivery, tissue engineering, and photothermal/photodynamic therapy • key challenges in translating GQD including scalability, toxicity concerns