Nano Biosensors for Sustainable Water Safety and Sanitation: Emerging Advances and Future Perspectives

ABSTRACT The increasing occurrence of biological, chemical, and emerging contaminants in aquatic environments poses significant challenges to water safety and environmental sustainability. Although conventional analytical methods offer high sensitivity, they are often limited by expensive instrumentation, complex procedures, and poor field applicability. Recent advances in nanotechnology have enabled the development of nano biosensors that combine functional nanomaterials with biological recognition elements for rapid, sensitive, and selective contaminant detection. This review highlights recent progress in electrochemical, optical, fluorescence, surface‐enhanced Raman spectroscopy, field‐effect transistor, paper‐based, CRISPR‐enabled, and microfluidic nano biosensors for water quality monitoring. The contributions of graphene, carbon nanotubes, metal oxides, MXenes, metal–organic frameworks, quantum dots, and hybrid nanocomposites to enhanced sensing performance are discussed. Additionally, the integration of artificial intelligence, machine learning, the Internet of Things, and smartphone‐assisted sensing is explored. Current challenges and future prospects toward sustainable, real‐time water monitoring and achieving Sustainable Development Goal 6 are critically discussed.