The applications of graphene oxide quantum dots in the removal of emerging pollutants in water: An overview

Abstract

Graphene oxide quantum dots (GQDs) are an emerging class of zero-dimensional, oxygen-rich materials with dimensions of less than 20 nm. GQDs exhibit the phenomena of quantum confinement and edge effects; this phenomenon bestows them with exceptional physico-chemical properties. These features have made GQDs suitable materials for application in the catalytic removal of organic pollutants and dyes, adsorption of heavy metals, filtration of organic pollutants and in the disinfection of microbes. However, challenges encountered when developing 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 allows high yields and easy purification of GQDs to be achieved. In addition, despite possible mechanisms having been proposed, a lack of an understanding of the photoluminescence (PL) properties of GQDs remains. This review focuses on some of the research that was reported on GQDs during in the past 20 years. The significant findings are summarized with comparative and balanced views. The emphasis is placed on the different synthetic routes for accessing GQDs and as well as the unique properties, which make GQDs ideal candidates for the removal of emerging pollutants from wastewater. An evaluation of the most used approaches and promising technologies for the removal of emerging pollutants using GQDs is also presented. Further, current challenges relating to the use of GQDs are addressed and an outlook of GQDs as well as recommendations for future work are presented.