Carbon dot-based functional nanomaterials with superior optical and antimicrobial properties

Introduction: Carbon dots (C-dots) are biocompatible, photoluminescent nanoparticles composed mainly of carbon, hydrogen and oxygen. They can be synthesized via pyrolytic decomposition of various precursors, including polymers, small organic molecules and biomass waste (1,2). Their chemical composition, size, shape and macroscopic properties are largely impacted by reaction parameters such as temperature, precursor concentration and duration.

Methods: C-dots were derived via pyrolytic treatment of citric acid and urea and were purified via dialysis, centrifugation and filtration before being subjected to post-synthesis hypochlorite treatment (3,4). They were characterized using a combination of spectroscopic and microscopic techniques such as TEM, XRD, FTIR and XPS. Their photoluminescent properties, cytotoxicity and antimicrobial activity were systematically evaluated.

Results: We demonstrate that varying the molar ratio of precursors and applying standard size-separation methods yields materials with strong photoluminescence in both liquid and solid states as well as advanced antimicrobial properties. The direct NaClO treatment of C-dots causes significant surface oxidation and etching, which is a process that reduces UV-vis absorbance, increases the quantum yield sixfold and greatly enhances antifungal activity.

Conclusion: We present a low-cost, time-efficient strategy to generate a range of highly photoluminescent materials based on C-dots. The resulting materials are promising candidates for various applications, including bioimaging, biosensing, antimicrobial treatment, environmental sensing and remediation, forensic science and optoelectronics.

References

1. A. Kelarakis, Current Opinion in Colloid and Interface Science 2015, 20, 354
2. A. Kelarakis MRS Energy and Sustainability, 2014, 1, E2
3. J.D. Stachowska, A. Murphy, C. Mellor, D. Fernandes, E. Gibbons, M. Krysmann, A. Kelarakis, E. Burgaz, J. Moore and S. G. Yeates, Scientific Reports, 2021, 11,10554
4. S. Gavalas, S. Beg, E. Gibbons, A. Kelarakis, Nanomaterials 2025, 15, 184