Fluorescent carbon quantum dots for heavy metal sensing.

Many heavy metals pose significant threats to the environment and human health. Traditional methods for detecting heavy metals are often limited by complex procedures, high costs, and challenges in field monitoring. Carbon quantum dots (CQDs), a novel class of fluorescent carbon nanomaterials, have garnered significant interest due to their excellent biocompatibility, low cost, and minimal toxicity. This paper reviews the primary synthesis methods, luminescence mechanisms, and fluorescence quenching mechanisms of CQDs, as well as their recent applications in detecting heavy metals. In heavy metal sensing applications, the simplest hydrothermal method is commonly employed for the one-step synthesis and surface modification of CQDs. Various green reagents and biomass materials, such as citric acid, glutathione, orange peel, and bagasse, can be used for CQDs' preparation. Quantum confinement effects and surface defects give CQDs their distinctive luminescence properties, enabling the detection of heavy metals through fluorescence quenching or enhancement. Additionally, CQDs can be applied in biological imaging and smart detection, and when combined with adsorption materials, they can offer multifunctional capabilities. This review also discusses the future development prospects of CQDs.