Recent advances in metal sulfide nanozymes for sensing.

Metal sulfide nanozymes have emerged as a highly promising class of catalytic nanomaterials for sensing applications due to their tunable activity, operational stability, and facile synthesis. Their sulfur-rich frameworks can promote electron transfer and the generation of reactive oxygen species, thereby enhancing signal amplification in colorimetric, electrochemical, and other sensing platforms. These attributes have enabled the sensitive detection of a broad range of analytes, including metal ions, pesticides, biomolecules, hydrogen peroxide, phenolics, and dyes, and have supported their integration into portable and point-of-care diagnostic devices. Despite rapid progress, the field remains fragmented by several unresolved challenges, including an incomplete understanding of structure-activity relationships, limited standardization of catalytic activity evaluation, and insufficient validation of selectivity in complex biological matrices. This review critically examines recent advances in metal sulfide nanozymes, focusing on their preparation strategies, catalytic mechanisms, and sensing applications. Unlike existing nanozyme reviews, this article specifically emphasizes how compositional modulation, defect engineering, heterostructure construction, and surface functionalization govern sensing performance in metal sulfide systems. By identifying major limitations and outlining future directions for mechanistic study, this review aims to provide a more focused framework for advancing metal sulfide nanozymes toward practical biomedical and environmental applications.