Environmental behavior and analytical strategies of metal-doped nanoplastics: From labeling techniques to single-particle tracking

Due to the small size, diverse compositions, and interferences from natural carbon-containing particles, tracking the fate and transport of nanoplastics (NPs) in environments and living organisms remains a challenge. Metal-doped NPs have emerged as a powerful proxy for tracking NP dynamics in complex systems. This review systematically examines current advances in the synthesis and applications of metal-doped NPs. We first discuss fundamental principles for selecting appropriate metal tags based on detection sensitivity, environmental stability, and biological compatibility. Subsequently, we critically evaluate various metal-doping strategies, highlighting their advantages and limitations. Next, the applications of metal doped-NPs are discussed, including studying environmental processes of NPs, tracing the uptake and distribution of NPs in plants and animals, and assessing the heterogeneity of NPs in cells. Finally, we identify key challenges in current methodologies and propose future research directions. Metal-doped NPs have significantly advanced our understanding of NP behaviors in environmental and biological systems.