Innovative dual-mode colorimetric/fluorescent sensors based on transition metal nanozymes: mechanisms, applications, and future perspectives

Transition metal nanozymes have emerged as promising alternatives to natural enzymes due to their exceptional catalytic activity, tunable physicochemical properties, and robust stability. In recent years, the integration of colorimetric and fluorescent sensing modalities into a single platform has garnered significant attention, offering complementary advantages in sensitivity, accuracy, and practical applicability. This comprehensive review systematically summarizes the latest advances in colorimetric/fluorescent dual-mode sensors based on transition metal nanozymes. We highlight their versatile applications in detecting heavy metals, foodborne pathogens, mycotoxins, organophosphorus pesticides, antibiotics, biomolecules, and tumor markers. Furthermore, the review elucidates the catalytic mechanisms of various nanozymes, including oxidase-like, peroxidase-like, catalase-like, and superoxide dismutase-like activities, and discusses their design principles and synthesis strategies. Finally, we address the current challenges—such as environmental susceptibility and limited integration with portable devices—and propose future directions for enhancing nanozyme performance and expanding their real-world applications. This work aims to provide valuable insights and a foundational reference for researchers in the fields of biosensing, environmental monitoring, and food safety.