A recent article in Luminescence reports a method for synthesizing fluorescent carbon dots (CDs) using laser ablation of bay leaves in biocompatible solutions. This approach emphasizes environmentally conscious practices in nanomaterial synthesis.
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Background
Carbon dots are nanometer-scale carbon particles with photoluminescent properties, biocompatibility, and chemical stability. These characteristics support their use in areas such as bioimaging, drug delivery, and environmental monitoring.
Synthesis methods include both top-down approaches (e.g., laser ablation, chemical oxidation) and bottom-up strategies (e.g., pyrolysis, microwave-assisted synthesis).
Laser ablation is recognized for its ability to produce CDs with controlled size and minimal chemical contamination. Traditionally, this technique uses synthetic or inorganic carbon sources. The use of natural biomass, such as plant leaves, offers a more sustainable alternative.
Methodology
In the study, bay leaves were irradiated using a Nd:YAG laser (1064 nm, 3 ns pulse duration, 100 mJ energy per pulse, 1 Hz repetition rate) while submerged in phosphate-buffered saline (PBS). Approximately 20 layers of bay leaves, each around 350 µm thick, were stacked in a glass test tube.
The sample was moved during irradiation to distribute the laser exposure evenly and avoid perforation. The process lasted for two hours, delivering about 7200 pulses. The laser ablation generated carbon-based nanoparticles directly in the PBS solution.
To characterize the resulting particles, several techniques were applied. UV-Visible spectroscopy showed an absorption peak near 274 nm, typical of π-π* transitions in carbon materials. Transmission electron microscopy (TEM) revealed mainly spherical particles, mostly 2–4 nm in diameter, with some larger particles present.
High-resolution TEM images indicated lattice fringes, suggesting some crystalline features. Under 365 nm UV light, the samples emitted blue light centered around 472 nm, indicating photoluminescence.
ATR-FTIR spectroscopy identified surface functional groups, including hydroxyl and carbonyl groups, associated with water dispersibility and biocompatibility. The fluorescence properties remained stable over a three-month period. Additional imaging with optical microscopy and scanning electron microscopy (SEM) provided further morphological context.
Results and Discussion
The synthesis method produced carbon dots with fluorescence and structural characteristics consistent with known nanomaterials. The absorption peak at 274 nm and emission around 472 nm are typical of CDs with sp² carbon domains and surface-related emission centers. TEM analysis confirmed a dominant particle size of 2–4 nm, with spherical morphology and partial crystalline features.
The optical properties, including emission under UV excitation, are consistent with size-dependent quantum confinement effects and possible contributions from surface defect states. ATR-FTIR analysis indicated the presence of hydrophilic functional groups, supporting the observed solubility and potential biocompatibility. The luminescence remained stable over a three-month period, suggesting chemical and structural stability.
Conclusion
The study presents a straightforward method for producing fluorescent carbon dots through laser ablation of bay leaves in PBS. The resulting nanoparticles are predominantly below 10 nm in size and exhibit blue photoluminescence under UV light. Their structural and chemical properties suggest potential applications in imaging and sensing technologies.
The use of natural bay leaves as a carbon source supports a more sustainable approach to CD synthesis and reduces the dependence on synthetic precursors or harsh chemicals. The findings demonstrate the relationship between synthesis conditions, nanoparticle structure, and optical behavior. Future research could further investigate and tailor the properties of these CDs for targeted applications.
Journal Reference
Manno D., Serra A. (2025). Synthesis of High Fluorescent Carbon Dots by Laser Ablation of Bay Leaves in Biocompatible Solutions. Luminescence. DOI: 10.1002/bio.70202, https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/bio.70202