Surface‐Engineered Nitrogen‐Doped MXene Quantum Dots for Fluorescent Environmental Metal Ion Detection

ABSTRACT Environmental contamination by metal ions poses serious risks to ecosystems and human health, driving the demand for sensitive, selective, and reliable detection strategies. Nitrogen‐doped MXene quantum dots (N‐MQDs) have recently emerged as promising fluorescent nanomaterials for environmental metal ion sensing owing to their rich surface chemistry, strong coordination ability, and tunable photoluminescence. This review summarizes recent progress in the synthesis, surface engineering, and fluorescence‐based sensing performance of N‐MQDs for the detection of environmentally relevant metal ions. Emphasis is placed on the role of nitrogen‐induced surface functional groups in regulating metal ion coordination, fluorescence quenching and recovery pathways, and sensing selectivity in aqueous and complex environmental matrices. Key chemical interaction mechanisms, including static quenching, competitive binding, and reversible coordination at the quantum dot surface, are systematically discussed to elucidate sensing behavior. The applicability of N‐MQDs in environmental monitoring, particularly for water quality assessment and heavy metal detection, is evaluated with respect to sensitivity, selectivity, and operational stability. This review provides a focused and comprehensive review of fluorescent environmental metal ion detection based on N‐MQDs.