This review highlights recent and important advances related to the synthesis, characterization and application of graphene quantum dot (GQD)-based nanocomposites for the agriculture and environmental sectors.

Recently, a large variety of engineered nanostructures possessing enzyme-like activities have been proposed, whose unique physical–chemical characteristics have enabled remarkable technological advances. In this review, we survey the recent advances in nanozymes for environmental applications. First, we give an updated overview of different types of nanomaterial-based artificial enzymes, including carbon, metal and metal oxide nanomaterials, metal–organic frameworks (MOFs) and hybrid nanostructures, and compare their properties (namely, the Michaelis–Menten constant (K_m) and the maximal reaction velocity (V_max)) with standard natural enzymes. Furthermore, the progress in nanozymes for detecting and removing various environmental contaminants (e.g., heavy metals, dyes, pesticides, and hormones) is also discussed. Then, we provide a comprehensive overview of the enlightening strategies employed (based on the modification of size, shape/morphology, surface coating, doping and use of hybrid structures, for instance) to modulate the properties of nanozymes in order to achieve the desired properties for environmental sensing and remediation. Finally, challenges and current opportunities are discussed to stimulate the interest of researchers in the development of novel multifunctional nanozymes for environmental applications.

Graphene quantum dots (GQDs) have been widely investigated in recent years due to their outstanding physicochemical properties. Their remarkable characteristics allied to their capability of being easily synthesized and combined with other materials have allowed their use as electrochemical sensing platforms. In this work, we survey recent applications of GQDs-based nanocomposites in electrochemical sensors and biosensors. Firstly, the main characteristics and synthesis methods of GQDs are addressed. Next, the strategies generally used to obtain the GQDs nanocomposites are discussed. Emphasis is given on the applications of GQDs combined with distinct 0D, 1D, 2D nanomaterials, metal-organic frameworks (MOFs), molecularly imprinted polymers (MIPs), ionic liquids, as well as other types of materials, in varied electrochemical sensors and biosensors for detecting analytes of environmental, medical, and agricultural interest. We also discuss the current trends and challenges towards real applications of GQDs in electrochemical sensors.