Emerging paradigms in bio-derived carbon dots for environmental sensing applications.

Biomass-based CDs constitute a rapidly developing, eco-friendly category of nanomaterials engineered mainly for ecological biosensing applications. By utilizing organic materials, including crop residues, botanical wastes and discarded food products, as the carbon source or precursor, these CDs offer a green synthesis method that avoids the risk of traditional chemical synthesis. As these green CDs are fabricated from natural precursors, these nanomaterials may contain surface-bound heteroatoms, like sulfur, nitrogen, and phosphorus, derived from their organic feedstocks. Therefore, these functionalized CDs facilitate the quick, easy and highly sensitive identification of environmental pollutants, such as pharmaceutical residues, toxic heavy metals, agricultural pesticides and novel contaminants. The presence of heteroatoms improves their fluorescence properties, selectivity, and interaction with target analytes. Consequently, these CDs exhibit rapid, user-friendly, and sensitive detection of environmental contaminants, including pesticides, heavy metals, antibiotics, and emerging pollutants. From this perspective, green-synthesised CDs are expected to have a substantial long-term impact on environmental monitoring. Their compatibility with portable sensing platforms, suitability for field-deployable platforms, and ability to detect contaminants at trace levels make them promising candidates for next-generation environmental monitoring systems. However, the transformation of these sustainable nanomaterials into practical environmental solutions will require further investigations into their biomass precursors, structural property correlations, and mechanism-driven sensing strategies. Instead of mainly focusing on lower detection limits, future research studies should focus on mechanistic insights, real environmental stability and real-world applicability to enable the practical utilisation of sustainable carbon dot sensing platforms.