• Single-atom nanozymes (SANs) offer atomically dispersed active sites, high atom utilization, and tunable coordination, overcoming limitations of conventional nanozymes.
• The review systematically covers synthesis strategies for SANs, including template, pyrolysis, and wet-chemistry methods.
• SANs show significant potential in monitoring and controlling environmental pollutants, such as heavy metals, organic dyes, and pesticides.
• Challenges remain in scalable production, stability, and selectivity, but future prospects include multifunctional SANs and integration with sensing platforms.