Green fluorescent carbon dots derived from cotton stalks for in situ labeling of cotton fibers

Abstract Background In-situ fluorescent labeling of cotton fibers using biomass-derived carbon dots remains underexplored. Conventional labeling techniques may damage fiber structure, exhibit limited environmental stability, and incur relatively high costs, restricting their practical application in sustainable cotton traceability. Carbon dots possess favorable photoluminescence properties, good biocompatibility, and low toxicity, showing promising potential for plant bioimaging and in-situ tracking. This provides a feasible route for developing low-damage, cost-effective, and stable labeling approaches for cotton fibers. In this study, green fluorescent carbon dots (G-CDs) were hydrothermally synthesized using renewable cotton stalk waste as the carbon source, and their applicability for in-situ fluorescent labeling of cotton fibers was investigated. Results The prepared G-CDs exhibited excitation-dependent photoluminescence, with optimal excitation at 410 nm, emission at 530 nm, and a quantum yield of 5.99%. TEM characterization revealed uniformly dispersed G-CDs nanoparticles with particle sizes ranging from 1.75 to 4.25 nm and an average diameter of 2.67 nm. FTIR and XPS analyses confirmed abundant hydrophilic functional groups (–OH, C = O, and C–N) on the G-CDs surface. G-CDs were supplied to cotton plants via root irrigation from the seedling stage to the boll-opening stage. CLSM observation and quantitative fluorescence analysis showed that G-CDs were absorbed by cotton roots (56.281 ± 1.073), translocated upward to stems (52.413 ± 2.003) and leaves (41.306 ± 2.063), and eventually accumulated in mature cotton fibers (29.985 ± 0.939). Furthermore, G-CDs labeling did not induce significant changes in cotton growth or fiber quality. All growth-related indicators and fiber quality parameters showed no statistically significant differences between the control and treatment groups ( p > 0.05). Conclusion G-CDs achieved in-situ fluorescent labeling of cotton fibers without impairing plant growth or fiber quality, while the synthesis strategy enabled the reuse of agricultural cotton stalk waste. It is suggested that this dual advantage facilitates non-destructive cotton labeling and the sustainable utilization of biomass waste. This work illustrates the applicable potential of biomass-derived carbon dots for in planta fiber labeling and cotton traceability research.