Synthesis and Applications of Biomass-Derived Carbon Dots

At many universities, foundational chemistry laboratories remain dominated by verification-style experiments with limited connection to contemporary research, which can hinder students’ awareness of disciplinary frontiers. Here we report an upper-division undergraduate laboratory module that integrates the green synthesis, characterization, and applications of biomass-derived carbon dots (CDs) into the curriculum. Common cnidium fruit (CCF), an inexpensive and renewable herbal material, serves as a natural carbon and nitrogen source to prepare highly luminescent CDs (CCF-CDs) via a one-step hydrothermal process (160 °C, 4 h), followed by filtration and dialysis. Students observe bright blue fluorescence under 365 nm UV irradiation and relate the optical behavior to surface functional groups and photoluminescence mechanisms. TEM characterization (performed by a departmental technician, with students observing data acquisition) reveals uniform spherical particles (5–7 nm; 5.29 ± 0.22 nm) with a graphite-like core (0.23 nm lattice spacing). Students then evaluate three applications of CCF-CDs: selective fluorescence quenching for Fe 3+ detection against 18 competing metal ions, antibacterial activity toward Escherichia coli and Staphylococcus aureus using plate-count assays, and an anticounterfeiting demonstration using CD-based fluorescent ink on filter paper. The module requires modest instrumentation, provides clear visual outcomes, and supports extensions, such as tuning hydrothermal conditions or designing additional sensing targets. Implementation with ∼200 students (teams of three) showed high attainment of learning objectives (the post-test average score is 95.8%) and strengthened students’ competencies in experimental design, nanoscale materials characterization, and data interpretation. Overall, this sustainable, low-hazard experiment offers a practical pathway for incorporating contemporary nanomaterials into undergraduate chemistry laboratory teaching and serves as a foundational activity within the Undergraduate Innovation and Entrepreneurship Program at the University.