Ginkgo-derived carbon quantum dots as a novel tracer for water seepage detection in grottoes

Water seepage within grottoes threatens structural stability and long-term conservation. Tracer method is effective for water seepage but are rarely applied in grottoes due to the potential impacts of conventional tracers on rocks. In this study, carbon quantum dots (CQDs) were synthesized on a large scale via a hydrothermal method using Ginkgo biloba leaves as a precursor. The physicochemical properties of the CQDs, their interactions with rock, and their migration behavior in water were systematically investigated. The synthesized CQDs exhibited strong fluorescence, excellent hydrophilicity, and negligible chemical interaction with rock substrates. The migration capacity was comparable to fluorescein sodium salt and superior to rhodamine B, indicating high mobility and recovery efficiency in typical rocky environments. Owing to low cost, high fluorescence intensity, good aqueous mobility, and non-invasive nature, the CQDs are promising tracers for identifying seepage pathways in grottoes and supporting seepage damage prevention and control.